WO2015008456A1 - Dc/dc converter - Google Patents

Dc/dc converter Download PDF

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Publication number
WO2015008456A1
WO2015008456A1 PCT/JP2014/003636 JP2014003636W WO2015008456A1 WO 2015008456 A1 WO2015008456 A1 WO 2015008456A1 JP 2014003636 W JP2014003636 W JP 2014003636W WO 2015008456 A1 WO2015008456 A1 WO 2015008456A1
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Prior art keywords
switching element
frequency
turned
down switching
control amount
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PCT/JP2014/003636
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French (fr)
Japanese (ja)
Inventor
泰弘 新宅
昌志 岡松
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パナソニックＩｐマネジメント株式会社
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Publication of WO2015008456A1 publication Critical patent/WO2015008456A1/en

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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M3/00—Conversion of dc power input into dc power output
    • H02M3/02—Conversion of dc power input into dc power output without intermediate conversion into ac
    • H02M3/04—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters
    • H02M3/10—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M3/145—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
    • H02M3/155—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
    • H02M3/156—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators
    • H02M3/158—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators including plural semiconductor devices as final control devices for a single load
    • H02M3/1582—Buck-boost converters

Definitions

  • the present invention relates to a DC / DC converter.
  • FIG. 19 is a schematic diagram of a buck-boost switching regulator which is a conventional DC / DC converter 101 described in Patent Document 1.
  • the DC / DC converter 101 is a step-up / step-down DC / DC converter that can obtain a desired output voltage by stepping up and stepping down an input voltage.
  • the DC / DC converter 101 includes a synchronous switching regulator 103 and a control circuit 105.
  • the synchronous switching regulator 103 receives the input voltage Vin and provides a regulated output voltage Vout.
  • the input voltage Vin can be higher, lower or substantially the same as the output voltage Vout.
  • the control circuit 105 can operate the synchronous switching regulator 103 in the buck mode, the boost mode, or the buck-boost mode.
  • Synchronous switching regulator 103 has four switches 107, 109, 111, 113 coupled between voltages Vin, Vout.
  • the switches 107, 109, 111, and 113 control the amount of current supplied to the output node at the voltage Vout, whereby the output voltage Vout can be held at the adjusted value.
  • the control circuit 105 receives the output voltage Vout and controls four drive signals V A , V B , V C , and V D that control switching of the four switches 107, 109, 111, and 113 in the synchronous switching regulator 103, respectively. I will provide a.
  • Control circuit 105 includes resistors 115 and 117, error amplifier 119, pulse width modulator 121, and logic circuit 123.
  • Pulse width modulator 121 includes a signal generator 125 and comparators 127 and 129.
  • FIG. 20 shows a signal of the DC / DC converter 101.
  • the horizontal axis indicates time
  • the vertical axis indicates voltage.
  • FIG. 20 shows voltages V X and V Y and a control voltage V CL input to the comparator 127 shown in FIG.
  • the voltage V X has a period T and is a triangular waveform having a minimum value V 1 and a maximum value V 3 .
  • Waveform signal V Y has a period T, it is a triangular waveform having a minimum value V 2 and a maximum value V 4. Further, as shown in FIG. 20, the voltage values V 1 to V 4 satisfy the relationship of V 1 ⁇ V 2 ⁇ V 3 ⁇ V 4 .
  • the synchronous switching regulator 103 controlled by the control circuit 105 When V 1 ⁇ V CL ⁇ V 2 , the synchronous switching regulator 103 controlled by the control circuit 105 operates in the back mode, and when V 2 ⁇ V CL ⁇ V 3 , the synchronization controlled by the control circuit 105.
  • the type switching regulator 103 operates in the buck-boost mode, and when V 3 ⁇ V CL ⁇ V 4 , the synchronous switching regulator 103 controlled by the control circuit 105 operates in the boost mode. If a V CL ⁇ V 1 or V CL ⁇ V 4, the synchronous switching regulator 103 operates in a degraded mode. By such an operation, the voltages V Z1 and V A2 and the drive signals V A to V D output from the comparators 127 and 129 change as shown in FIG.
  • the DC / DC converter includes a step-down switching element, a step-up switching element, and a control circuit.
  • the control circuit obtains the time ratio of the boosting switching element as a time ratio control amount based on the output voltage, turns on and off the boosting switching element at a predetermined on / off frequency, and at a frequency determined based on the time ratio control amount. It operates to turn on and off the step-down switching element.
  • the control circuit obtains the time ratio of the step-down switching element as a time ratio control amount based on the output voltage, turns on and off the step-down switching element at a predetermined on / off frequency, and is determined based on the time ratio control amount It operates to turn on and off the step-up switching element at a frequency.
  • This DC / DC converter operates normally even when the output voltage is very close to the input voltage.
  • FIG. 1 is a block circuit diagram of the DC / DC converter according to the first embodiment.
  • FIG. 2 is a timing chart of the switching elements in the step-up operation of the DC / DC converter in the first embodiment.
  • FIG. 3 is a diagram showing the correlation between the duty ratio control amount and the on / off frequency of the DC / DC converter in the first embodiment.
  • FIG. 4 is a timing chart of the switching element during the step-up operation of the DC / DC converter in the first embodiment.
  • FIG. 5 is a timing chart of the switching elements in the step-up operation of the DC / DC converter in the first embodiment.
  • FIG. 6 is a timing chart of the switching element at the time of switching of the step-up / step-down operation of the DC / DC converter in the first embodiment.
  • FIG. 7 is a timing chart of the switching elements in the step-down operation of the DC / DC converter in the first embodiment.
  • FIG. 8 is a timing chart of the switching element in the step-down operation of the DC / DC converter in the first embodiment.
  • FIG. 9 is a timing chart of the switching elements in the step-down operation of the DC / DC converter in the first embodiment.
  • FIG. 10 is a block circuit diagram of the DC / DC converter according to the second embodiment.
  • FIG. 11 is a timing chart of the switching elements in the step-up operation of the DC / DC converter according to the second embodiment.
  • FIG. 12 is a diagram showing the correlation between the duty ratio control amount and the on / off frequency of the DC / DC converter in the second embodiment.
  • FIG. 13 is a timing chart of the switching elements in the step-up operation of the DC / DC converter according to the second embodiment.
  • FIG. 14 is a timing chart of the switching elements in the step-up operation of the DC / DC converter according to the second embodiment.
  • FIG. 15 is a timing chart of the switching elements at the time of step-up / step-down switching of the DC / DC converter in the second embodiment.
  • FIG. 16 is a switching element timing chart in the step-down operation of the DC / DC converter in the second embodiment.
  • FIG. 17 is a timing chart of the switching elements in the step-down operation of the DC / DC converter according to the second embodiment.
  • FIG. 18 is a timing chart of the switching elements in the step-down operation of the DC / DC converter according to the second embodiment.
  • FIG. 19 is a schematic diagram of a conventional DC / DC converter.
  • FIG. 20 is a diagram showing signals of a conventional DC / DC converter.
  • FIG. 1 is a block circuit diagram of a DC / DC converter 11 according to the first embodiment.
  • the DC / DC converter 11 is connected to the input terminal 15 and the connection point 30P electrically in series between the input terminal 15, the output terminal 19, the ground terminal 17, and the input terminal 15 and the connection point 30P.
  • the step-down switching element 30, the step-down switching element 31 electrically connected in series between the connection point 30P and the ground terminal 17, and the output terminal 19 and the connection point 33P are connected to the connection point 30P and the ground terminal 17.
  • the step-up switching element 33 electrically connected in series between the output terminal 19 and the connection point 33P, and the connection point 33P and the ground terminal 17 electrically connected in series between the connection point 33P and the ground terminal 17.
  • the step-up switching element 35 connected to each other, the inductor 21 electrically connected in series between the connection points 30P and 33P, and the input terminal 5, an input voltage detection circuit 23 electrically connected to the output terminal 19, an output voltage detection circuit 25 electrically connected to the output terminal 19, step-down switching elements 30 and 31, step-up switching elements 33 and 35, and input voltage detection A control circuit 27 electrically connected to the circuit 23 and the output voltage detection circuit 25 is provided.
  • the input voltage detection circuit 23 detects the input voltage Vi at the input terminal 15.
  • the output voltage detection circuit 25 detects the output voltage Vo at the output terminal 19.
  • a DC power supply 28 is electrically connected between the input terminal 15 and the ground terminal 17.
  • DC power supply 28 is a solar cell.
  • the DC / DC converter 11 can output a stable output voltage Vo that is not easily affected by the weather or shadow by boosting or stepping down the input voltage Vi generated by the DC power supply 28 (solar cell).
  • a load for example, a load, a secondary battery, or an inverter for supplying power to commercial system power can be connected between the output terminal 19 and the ground terminal 17, but the embodiment 1 is not particularly limited. .
  • the step-down switching elements 30 and 31 are connected in series at a connection point 30P.
  • the step-down switching elements 30 and 31 perform complementary operations.
  • the complementary operation is basically an operation in which the on / off states of the step-down switching elements 30 and 31 are different from each other. However, if the step-down switching elements 30 and 31 are simultaneously turned off within a short period, the complementary operation is not temporarily performed. However, in the first embodiment, the short-time simultaneous off is included in the complementary operation. .
  • the on and off states of the step-down switching elements 30 and 31 are changed through the simultaneous off state in which both the step-down switching elements 30 and 31 are off. Specifically, when one of the step-down switching elements 30 and 31 is on, the other is off.
  • the control circuit 27 turns on and off the switching elements 30 and 31 in a complementary manner, the on period of the switching elements 30 and 31 should be smaller than a certain minimum value due to the simultaneous off period of the switching elements 30 and 31 and the switching speed. It is not possible to set the ON period longer than the minimum value, or the switching elements 30 and 31 can be turned OFF.
  • the step-up switching elements 33 and 35 perform the same complementary operation as the step-down switching elements 30 and 31.
  • the control circuit 27 turns on and off the switching elements 33 and 35 in a complementary manner, the on period of the switching elements 33 and 35 should be smaller than a certain minimum value due to the simultaneous off period of the switching elements 33 and 35 and the switching speed. It is not possible to set the ON period longer than the minimum value, or the switching elements 33 and 35 can be turned OFF.
  • switching elements 30, 31, 33, and 35 use field effect transistors (hereinafter referred to as FETs). Therefore, parasitic diodes 30D, 31D, 33D, and 35D are connected in parallel to the switching elements 30, 31, 33, and 35, respectively.
  • the switching element is not limited to the FET, and may be another semiconductor switching element.
  • a smoothing capacitor 37 is electrically connected between the output terminal 19 and the ground terminal 17.
  • the smoothing capacitor 37 may not be connected when a secondary battery having a very large capacity is connected between the output terminal 19 and the ground terminal 17.
  • the input voltage detection circuit 23 detects the input voltage Vi based on the potential of the ground terminal 17 and outputs it to the control circuit 27.
  • the output voltage detection circuit 25 detects the output voltage Vo based on the potential of the ground terminal 17 and outputs it to the control circuit 27.
  • the control circuit 27 includes a microcomputer, a peripheral circuit, a memory, and the like.
  • the control circuit 27 takes in the input voltage Vi and the output voltage Vo, and turns on and off the step-down switching elements 30 and 31 with the switch signals SW1 and SW2, respectively.
  • the step-up switching elements 33 and 35 are turned on and off by SW4.
  • FIG. 2 shows the on / off states of the step-down switching elements 30 and 31 and the step-up switching elements 33 and 35 in the step-up operation of the DC / DC converter 11.
  • the vertical axis indicates the on and off states of each switching element, and the horizontal axis indicates time.
  • the control circuit 27 switches the step-up switching elements 33 and 35 on and off at a predetermined on / off frequency and operates them in a complementary manner. By this operation, the DC / DC converter 11 boosts the input voltage Vi and outputs the output voltage Vo.
  • the control circuit 27 sets the time ratio of the step-up switching elements 33 and 35 so that the output voltage Vo detected by the output voltage detection circuit 25 becomes a predetermined set voltage, that is, based on the output voltage Vo. Obtained by calculating as a ratio control amount.
  • the duty ratio is the ratio of the on period to one cycle of the on / off frequency of the switching element.
  • the control circuit 27 calculates the duty ratio of the boosting switching element 35 as the duty ratio control amount Ds.
  • the time ratio of the boosting switching element 33 is the number obtained by subtracting the time ratio of the boosting switching element 35 from 1 when the simultaneous off period of the boosting switching elements 33 and 35 is short, that is, the boosting switching element 35 is turned on / off.
  • the DC / DC converter 11 adjusts the step-up ratio, which is the ratio of the output voltage Vo to the input voltage Vi, by pulse width modulation (PWM) control in which the control circuit 27 changes the time ratio, and sets the output voltage Vo to a predetermined set voltage.
  • PWM pulse width modulation
  • the control circuit 27 does not perform on-off control of the step-down switching elements 30 and 31 at a predetermined frequency, and the step-down switching is performed so that the input voltage Vi is directly applied to the inductor 21 as shown in FIG.
  • the element 30 is turned on, and the step-down switching element 31 is turned off so that the input terminal 15 and the ground terminal 17 are not short-circuited.
  • Such an operation is, for example, in the case of sunrise, dusk, cloudy weather, or shadows, and the amount of solar radiation incident on the DC power supply 28 (solar cell) is insufficient, and the input voltage Vi is higher than the desired output voltage Vo. Done when low.
  • the operation of the DC / DC converter 11 when the amount of solar radiation to the DC power supply 28 is improved and the input voltage Vi increases will be described.
  • the DC / DC converter 11 is switched from the step-up operation to the step-down operation.
  • the correlation between the duty ratio control amount Ds and the on / off frequency is determined in advance, and the correlation is stored in the memory of the control circuit 27.
  • the control circuit 27 controls the switching operation of the switching elements 30, 31, 33 and 35 based on the correlation.
  • FIG. 3 shows the correlation between the on / off frequency fs of the step-down switching elements 30 and 31, the on / off frequency fb of the step-up switching elements 33 and 35, and the time ratio control amount Ds.
  • the horizontal axis represents the duty ratio control amount Ds
  • the vertical axis represents the on / off frequency.
  • the operation of the DC / DC converter 11 shown in FIG. 2 will be described with reference to FIG.
  • the control circuit 27 complementarily turns on and off the boosting switching elements 33 and 35
  • the ON period of the boosting switching elements 33 and 35 cannot be made smaller than a certain minimum value.
  • the control circuit 27 complementarily turns on and off the boosting switching elements 33 and 35 at the on / off frequency
  • the boosting switching element 35 is boosted at a time ratio equal to or greater than the predetermined value Ds1 that is equal to or greater than the minimum value of the on period of the boosting switching element 35
  • the boosting switching elements 33 and 35 are complementarily turned on and off at the on / off frequency so that the switching element 35 is turned on and off. In the operation shown in FIG.
  • the duty ratio control amount Ds shown in FIG. 3 is in a range Rs1 that is equal to or greater than a predetermined value Ds1.
  • the control circuit 27 sets the on / off frequency f1 in a state where the duty ratio of the boosting switching element 35 is the predetermined value Ds1.
  • the boosting switching elements 33 and 35 are complementarily turned on and off, that is, the boosting switching elements 33 and 35 are operated in a complementary manner by PWM control.
  • the on / off frequency f1 is 80 kHz in the range Rs1 in which the step-up switching elements 33 and 35 are PWM-controlled.
  • the predetermined value Ds1 that is the minimum value of the duty ratio of the boosting switching element 35 is 0.5.
  • the duty ratio of the boosting switching element 35 is the predetermined value Ds1. Since the period of the frequency of 80 kHz is 12.5 ⁇ sec, the control circuit 27 generates a pulse waveform with a time ratio of 0.5 and turns on the boosting switching element 35 for an on period of 6.25 ⁇ sec every 12.5 ⁇ sec. To.
  • the control circuit 27 causes the boosting switching element 33 to be repeatedly turned on and off every 6.25 ⁇ sec every 12.5 ⁇ sec. Since the step-up switching element 35 performs an operation complementary to the step-up switching element 33, in the operation shown in FIG. 2 where the time ratio is 0.5, the phase of the ON / OFF operation of the step-up switching element 35 is the step-up switching element. It is 180 degrees out of phase with the 33 operation.
  • step-down switching element 30 is on and the step-down switching element 31 is off as described above, as shown in FIG. 3, when the time ratio control amount Ds is in the range Rs1 that is the predetermined value Ds1, The on / off frequency fs of the step-down switching elements 30 and 31 is zero.
  • the control ratio 27 for the control circuit 27 to set the output voltage Vo to the target value.
  • Ds decreases and enters a range Rs2 smaller than the predetermined value Ds1
  • the on / off frequency fs of the step-down switching elements 30, 31 is kept zero, that is, the step-down switching element 30 is kept on and the step-down switching element PWM control that changes the time ratio of the step-up switching elements 33 and 35 at a constant on / off frequency f1 with 31 kept off cannot be performed.
  • a range Rs2 of the duty ratio control amount Ds is a range smaller than the predetermined value Ds1 and equal to or greater than zero.
  • the control circuit 27 maintains the duty ratio of the boosting switching element 35 at the predetermined value Ds1.
  • the step-up switching elements 33 and 35 are complementarily turned on and off at the on / off frequency f1 to perform complementary operations, and at the same time, the step-down switching elements 30 and 31 are complementarily turned on and off at the on / off frequency fs to perform complementary operations. Operates to do.
  • the minimum value of the on / off frequency fs of the step-down switching elements 30 and 31 is the audible frequency. It is higher than the maximum frequency f0 of the band Bf. In the first embodiment, the maximum frequency f0 is 18 kHz. Therefore, when the duty ratio control amount Ds changes from the predetermined value Ds1 to a state slightly smaller than the predetermined value Ds1, the control circuit 27 rapidly increases the on / off frequency fs from zero to a frequency higher than the maximum frequency f0. Thus, in the ranges Rs1 and Rs2, the correlation between the on / off frequency fs of the step-down switching elements 30 and 31 and the duty ratio control amount Ds is discontinuous.
  • the on / off frequency fs is in the audible frequency band Bf, noise may be generated from the DC / DC converter 11.
  • the on / off frequency f1 in the PWM control is included in the audible frequency band Bf, it becomes a noise factor. Therefore, the on / off frequency f1 is also set to 80 kHz, which is a value outside the audible frequency band Bf.
  • the lowest frequency of the on / off frequency fs is set to zero, and the correlation between the on / off frequency fs of the step-down switching elements 30 and 31 and the duty ratio control amount Ds is continuously obtained in the ranges Rs1 and Rs2. It may be.
  • the control circuit 27 can determine from the difference in the output voltage Vo with respect to the target value that the PWM control cannot be performed. That is, when it is determined that the difference is equal to or less than the measurement or control error range and the output voltage Vo matches the target value, the control circuit 27 determines that the PWM control is being performed. On the other hand, if the difference exceeds the error range, the control circuit 27 determines that PWM control cannot be performed. In this case, the control circuit 27 fixes the time ratio of the boosting switching elements 33 and 35 to the predetermined value Ds1 and complementarily turns on and off the boosting switching elements 33 and 35 at the on / off frequency f1. The step-down switching elements 30 and 31 are turned on and off at the on / off frequency fs.
  • the duty ratio control amount Ds in this operation is based on the proportional integration amount in the first embodiment. Therefore, in the first embodiment, when the duty ratio control amount Ds is smaller than the predetermined value Ds1, the duty ratio control amount Ds is a proportional integral amount with respect to the step-down switching elements 30 and 31. Note that the duty ratio control amount Ds is not limited to the proportional integral amount, and may be, for example, a proportional integral differential amount. In this case, although the control is complicated, the accuracy of the output voltage Vo is increased. it can. Thus, the DC / DC converter 11 operates normally even when the output voltage Vo is very close to the input voltage Vi.
  • the control circuit 27 When the duty ratio control amount Ds is in the range Rs2 smaller than the predetermined value Ds1, as shown in FIG. 3, the control circuit 27 is in a state where the boosting switching elements 33 and 35 are complementarily turned on and off at the on / off frequency f1.
  • the step-down switching elements 30 and 31 are complementarily turned on and off at the on / off frequency fs.
  • the step-down switching elements 30 and 31 In the process where the duty ratio control amount Ds decreases from the predetermined value Ds1 to the predetermined value Ds2 smaller than the predetermined value Ds1, as shown in FIG. 3, the step-down switching elements 30 and 31 are complementarily turned on and off at the on / off frequency fs.
  • the control circuit 27 turns on and off the step-down switching elements 30 and 31 at the on / off frequency f2 (20 kHz) in a complementary manner.
  • FIG. 4 is a timing chart of the switching elements 30, 31, 33, and 35 when the duty ratio control amount Ds is the predetermined value Ds2.
  • the step-up switching elements 33 and 35 are 180 degrees out of phase and have an on / off frequency f1 (80 kHz) and a fixed time ratio (0 in the first embodiment). 5) Complementarily repeats the on / off operation.
  • the control circuit 27 turns off the step-down switching element 30 in a period from time t2 to time t3 and in a period from time t10 to time t11. Since the control circuit 27 operates the step-down switching element 31 in a complementary manner with the step-down switching element 30, it is turned on during the above period.
  • the on / off frequency f2 of the step-down switching elements 30 and 31 when the duty ratio control amount Ds is a predetermined value Ds2 is 20 kHz
  • the on / off frequency f2 is the on / off frequency f1 ( 80 kHz)
  • its period is four times. Therefore, the step-down switching element 30 is repeatedly turned off by the control circuit 27 at a period four times that of the step-up switching element 33, and the step-down switching element 31 operating in a complementary manner with the step-down switching element 30 is The switch is repeatedly turned on at a cycle four times that of the boosting switching element 35.
  • the ON period during which the step-down switching element 31 is turned on is fixed to the same value as the ON period (6.25 ⁇ sec) of the step-up switching element 35.
  • the off period during which the boosting switching element 33 that performs a complementary operation with the boosting switching element 35 is turned off is also fixed to 6.25 ⁇ s, which is the same period as the on period (6.25 ⁇ s) of the boosting switching element 35. .
  • the step-down switching element 30 is turned on every four times as high as the step-up switching elements 33 and 35, and the step-down switching element 31 is turned off every period. . That is, in the first embodiment, every time the step-up switching element 33 is turned off four times, the step-down switching element 30 is turned off once. The off periods of the step-up switching element 33 and the step-down switching element 30 are substantially equal within the error range of the control circuit 27. Similarly, every time the step-up switching element 35 is turned on four times, the step-down switching element 31 is turned on once, and the ON period of the step-up switching element 35 and the step-down switching element 31 is substantially within an error range. equal.
  • the on / off frequencies fs of the step-down switching elements 31 and 33 gradually increase.
  • FIG. 5 is a timing chart of the switching elements 30, 31, 33, and 35 when the duty ratio control amount Ds is the predetermined value Ds3.
  • the cycle in which the step-down switching element 31 is turned on is twice the cycle of the on-off frequency f1 of the step-up switching element 35.
  • the on-period of the step-down switching element 31 is 6.25 ⁇ sec, and is substantially equal to the on-period of the step-up switching element 35 within an error range. Therefore, every time the step-up switching element 35 is turned on twice, the step-down switching element 31 is turned on once.
  • the step-down switching element 30 performs an operation complementary to the step-down switching element 31.
  • the boosting switching element 33 performs an operation complementary to the boosting switching element 35.
  • the on / off frequency fs of the step-down switching elements 30, 31 gradually increases, the step-down switching element 31 is turned on, and the step-down switching element 31 is turned on.
  • the period when the switching element 30 is turned off is shortened. Since the off period of the step-down switching element 30 is fixed at 6.25 ⁇ sec, the on period in one cycle of the step-down switching element 30 becomes shorter as the time ratio control amount Ds decreases. Since the step-down switching element 31 performs a complementary operation with the step-down switching element 30, the OFF period of one step of the step-down switching element 31 is shortened with a decrease in the time ratio control amount Ds.
  • the duty ratio control amount Ds is further reduced to a predetermined value Ds4 that is substantially zero within an error range of voltage detection or calculation, that is, when the input voltage Vi and the output voltage Vo become substantially equal within the error range.
  • Ds4 a predetermined value that is substantially zero within an error range of voltage detection or calculation, that is, when the input voltage Vi and the output voltage Vo become substantially equal within the error range.
  • the on / off frequency fs of the step-down switching elements 30 and 31 is substantially equal to the on / off frequency f1 of the step-up switching elements 33 and 35 within an error range.
  • the timing chart of the step-down switching element 30 is the same as the timing chart of the step-up switching element 33.
  • the timing chart of the step-down switching element 31 is the same as the timing chart of the step-up switching element 35.
  • This state corresponds to the DC / DC converter 11 performing the step-up operation and the step-down operation at the same time under the same conditions, and as described above, the input voltage Vi is controlled as it is to the output voltage Vo.
  • the period when the step-down switching element 31 is turned on as the time ratio control amount Ds decreases. Becomes shorter and the number of on-times increases. Accordingly, the pulse of the step-down switching element 31 is controlled to increase while the duty ratio control amount Ds is between the predetermined value Ds1 and the predetermined value Ds2.
  • This can be realized by proportional-integral control by the control circuit 27. Note that this control may be realized by proportional-integral-derivative control as described above.
  • the duty ratio control amount Ds becomes negative, and the on / off frequency fb of the step-up switching elements 33 and 35 gradually decreases according to the correlation shown in FIG.
  • the on state of the switching element 35 is controlled.
  • FIG. 7 is a timing chart of the switching elements 30, 31, 33, and 35 when the duty ratio control amount Ds is the predetermined value Ds5.
  • the step-up switching element 35 is controlled so as to be turned on in a period (25 ⁇ sec) twice as long as that of the step-down switching element 31 in a state where the on-period (6.25 ⁇ sec) is fixed.
  • the step-down switching element 30 performs an operation complementary to the step-down switching element 31, and the step-up switching element 33 performs an operation complementary to the step-up switching element 35.
  • FIG. 8 is a timing chart of the switching elements 30, 31, 33, and 35 when the duty ratio control amount Ds is the predetermined value Ds6.
  • the step-up switching element 35 is controlled to be turned on at a cycle four times that of the step-down switching element 31.
  • the step-down switching element 30 performs an operation complementary to the step-down switching element 31, and the step-up switching element 33 performs an operation complementary to the step-up switching element 35.
  • the control circuit 27 stops the on / off operation of the step-up switching elements 33 and 35 according to the correlation shown in FIG. Only the elements 30 and 31 are turned on / off. As a result, the DC / DC converter 11 performs a step-down operation using only the step-down switching elements 30 and 31.
  • the control circuit 27 performs PWM at the variation time ratio with respect to the step-down switching elements 30 and 31. By performing the control, the output voltage Vo is controlled to a desired voltage value.
  • FIG. 9 is a timing chart of the switching elements 30, 31, 33, and 35 when the duty ratio control amount Ds is in the range Rs4 that is equal to or less than the predetermined value Ds7.
  • the control circuit 27 keeps the boost switching element 33 on and keeps the boost switching element 35 off. Further, the control circuit 27 causes the step-down switching elements 30 and 31 to repeat the ON / OFF operation complementarily.
  • the boosting switching element 35 is turned off as the time ratio control amount Ds decreases, as shown in FIGS. Becomes longer and the number of times of off is reduced. Therefore, while the duty ratio control amount Ds is between the predetermined value Ds4 and the predetermined value Ds7, the pulse of the boosting switching element 33 is controlled to decrease. This operation can be realized by proportional-integral control by the control circuit 27.
  • the DC / DC converter 11 When the duty ratio control amount Ds is increased from a small value, that is, when the step-up operation is performed from the step-down operation, the DC / DC converter 11 performs an operation reverse to the above description. In this case, the predetermined value Ds1 is replaced with the predetermined value Ds7, and the predetermined value Ds7 is replaced with the predetermined value Ds1.
  • control by the control circuit 27 when switching from the step-up operation described above to the step-down operation is summarized below.
  • the control circuit 27 determines in advance for the step-down switching elements 30 and 31 that are not performing pulse width modulation control. On-control is performed in a state in which the ON period of one step-down switching element 30, 31 is fixed for each period obtained based on the correlation between the duty ratio control amount Ds and the ON / OFF frequency fs. At the same time, the OFF control is performed in a state where the OFF period of the other step-down switching element 30, 31 is fixed.
  • the control circuit 27 switches the operation of the step-up switching elements 33 and 35 and the operation of the step-down switching elements 30 and 31.
  • the step-down switching elements 30 and 31 perform step-down operation.
  • the control by the control circuit 27 when switching from the step-down operation to the step-up operation is summarized below.
  • the control circuit 27 determines in advance the switching elements 33 and 35 for boosting that are not performing pulse width modulation control.
  • on-control is performed in a state in which the ON period of one of the boosting switching elements 33 and 35 is fixed for each period obtained based on the correlation between the duty ratio control amount Ds and the ON / OFF frequency fb.
  • the OFF control is performed in a state where the OFF period of the other boosting switching element 35 of the boosting switching elements 33 and 35 is fixed.
  • the control circuit 27 switches the operation of the step-up switching elements 33 and 35 and the operation of the step-down switching elements 30 and 31.
  • the boosting switching elements 33 and 35 perform the boosting operation.
  • the DC / DC converter 11 can smoothly switch the step-up / step-down operation. Further, only when the voltage difference in the vicinity of switching the step-up / step-down operation, that is, when the duty ratio control amount Ds is close to 0, the four switching elements are turned on / off, and when only the step-up operation or the step-down operation is performed, two Only the switching element is turned on / off. Therefore, the efficiency of the DC / DC converter 11 is improved.
  • a conventional DC / DC converter 101 shown in FIG. 19 performs a buck-boost mode operation when switching between a boost mode and a buck mode, as shown in FIG. At this time, as shown in FIG. 20, two voltages V Z1 and V Z2 are required. Since these are generated based on two voltages V X and V Y which are triangular waves, a circuit for generating the voltages V X and V Y is required, and the circuit configuration is complicated.
  • the DC / DC converter 11 when the step-up / step-down operation is switched, the switching elements 30, 31, Since the on-controls 33 and 35 are performed, it is not necessary to use two triangular waves. Therefore, the DC / DC converter 11 can have a simple circuit configuration.
  • the on / off frequency fs of the step-down switching elements 30 and 31 and the minimum value of the on / off frequency fb of the step-up switching elements 33 and 35 are each zero, but in the case of the bootstrap circuit configuration, the on / off frequency fs is set.
  • Fb may be zero or more.
  • the control circuit 27 performs PWM control on the boosting switching elements 33 and 35 when boosting only, and performs PWM control on the buck switching elements 30 and 31 when only boosting. Do. Then, the control circuit 27 can perform step-up / step-down switching by controlling a total of four switching elements 30, 31, 33, and 35 based on the correlation. Since the control only changes the on / off cycle at the time of switching, the circuit for obtaining the two triangular waves of the conventional DC / DC converter shown in FIGS. 19 and 20 is not required, and the voltage can be increased or decreased with a simple configuration. A DC / DC converter 11 can be obtained.
  • the control circuit 27 turns on / off each time when the step-up switching elements 33 and 35 perform complementary operations and when the step-down switching elements 30 and 31 perform complementary operations.
  • the states are switched simultaneously within an error range in the response of the control circuit 27 and the switching element.
  • the control circuit 27 switches on and off through a simultaneous off period in which the two step-up switching elements 33 and 35 are simultaneously turned off, and a simultaneous off period in which the two step-down switching elements 30 and 31 are simultaneously turned off. May be switched on and off. Thereby, the possibility of a short circuit when there is substantially no simultaneous OFF period can be reduced for the following reasons.
  • step-up switching elements 33 and 35 When the step-up switching elements 33 and 35 are switched at substantially the same time, both of them may be turned on simultaneously for a moment depending on an error. As a result, the output terminal 19 and the ground terminal 17 may be short-circuited and the output voltage Vo may become unstable. Also, due to the occurrence of a short circuit, depending on the capacity of the smoothing capacitor 37, a large current may flow from the smoothing capacitor 37, and the boosting switching elements 33 and 35 may deteriorate.
  • step-down switching elements 30 and 31 are switched substantially simultaneously, there is a possibility that both of them may be turned on simultaneously for a moment depending on an error. As a result, the input voltage Vi becomes unstable, and may cause a malfunction particularly during the buck-boost control. Furthermore, since the positive electrode and the negative electrode of the DC power supply 28 are short-circuited, the life of the DC power supply 28 may be affected.
  • the simultaneous off period affects the stability of the output voltage Vo, so the simultaneous off period exceeds the error range and is compared to the on period. It is desirable to set as short as possible. Further, depending on the control speed of the control circuit 27 and the response speed of each switching element, the ON / OFF states of the switching elements may be switched simultaneously without interposing the simultaneous OFF period.
  • the necessity of interposing the simultaneous OFF period may be determined as appropriate depending on the device to be used, its performance, and the stability of the required output voltage Vo.
  • the operation of the step-up switching elements 33 and 35 and the step-down switching element 30 are performed.
  • this is not limited to such an operation. Specific examples thereof will be described below.
  • the control circuit 27 performs the operation of the step-up switching elements 33 and 35 and the operation of the step-down switching elements 30 and 31 when the duty ratio control amount Ds decreases and reaches a predetermined value Ds3.
  • the operation of each switching element is changed from the operation shown in the timing chart of FIG. 5 to the operation shown in the timing chart of FIG. Since the timing chart of FIG. 7 is an operation when the duty ratio control amount Ds reaches the predetermined value Ds5, the output voltage Vo is a desired value until the duty ratio control amount Ds reaches the predetermined value Ds5 from the predetermined value Ds3.
  • the above deviation may be within an allowable range. In this case, the timing at which the operation of the step-up switching elements 33 and 35 and the operation of the step-down switching elements 30 and 31 are exchanged does not have to be strictly the time when the time ratio control amount Ds reaches the predetermined value Ds4. .
  • the switching elements 30, 31, 33, and 35 are turned on and off at substantially the same cycle even if the duty ratio control amount Ds is not exactly the predetermined value Ds4. Can be considered.
  • substantially is defined to include an allowable range in the amount of deviation of the output voltage Vo in addition to the above error range of voltage measurement and calculation. Accordingly, in the process in which the duty ratio control amount Ds decreases toward the predetermined value Ds4, if the amount of deviation of the output voltage Vo falls within the allowable range, the switching elements 30, 31, 33, and 35 are substantially controlled in the same cycle.
  • the control circuit 27 considers that this is the state, and switches the operation of the step-up switching elements 33 and 35 and the operation of the step-down switching elements 30 and 31. Even in such a configuration, the circuit for obtaining the two triangular waves of the conventional DC / DC converter shown in FIGS. 19 and 20 is not required, and the DC / DC converter 11 capable of step-up / step-down with a simple configuration is provided. can get.
  • the control circuit 27 operates as follows when the output voltage Vo is equal to or higher than the input voltage Vi. That is, the control circuit 27 turns on the step-down switching element 30, turns off the step-down switching element 31, and turns on the step-up switching elements 33 and 35 at a predetermined on / off frequency f1. It operates so as to obtain the time ratio as the time ratio control amount Ds based on the output voltage Vo. When the time ratio control amount Ds is equal to or greater than the predetermined value Ds1, the control circuit performs step-up switching at the time ratio of the time ratio control amount Ds with the step-down switching element 30 turned on and the step-down switching element 31 turned off.
  • the elements 33 and 35 operate so as to be turned on / off at a predetermined on / off frequency f1.
  • the control circuit 27 turns on and off the boosting switching elements 33 and 35 at the predetermined on / off frequency f1 at the time ratio of the predetermined value Ds1, and based on the time ratio control amount Ds.
  • the step-down switching elements 30 and 31 are operated to be turned on and off at the determined on / off frequency fs.
  • the control circuit 27 When the output voltage Vo is equal to or higher than the input voltage Vi and the duty ratio control amount Ds is smaller than the predetermined value Ds1, the control circuit 27 performs step-down at the on / off frequency fs with the on-period of the step-down switching element 31 fixed. You may operate
  • the control circuit 27 When the duty ratio control amount Ds is substantially zero, the control circuit 27 turns on and off the step-up switching elements 33 and 35 at a predetermined on / off frequency f1, and steps down the step-down switching element 30 at a predetermined on / off frequency f1. You may operate
  • control circuit 27 switches the operation of the step-up switching elements 33 and 35 and the operation of the step-down switching elements 30 and 31 when the duty ratio control amount Ds becomes smaller than the predetermined value Ds3 smaller than the predetermined value Ds1. May be. That is, when the duty ratio control amount Ds is equal to or larger than the predetermined value Ds3 smaller than the predetermined value Ds1, the control circuit 27 turns on and off the boosting switching elements 33 and 35 at the predetermined on / off frequency f1 at the time ratio of the predetermined value Ds1.
  • the step-down switching elements 30 and 31 may be turned on and off at the on / off frequency fs.
  • the control circuit 27 turns on and off the step-down switching elements 30 and 31 at the predetermined on / off frequency f1 at the time ratio of the predetermined value Ds1 and at the on / off frequency fs.
  • the boosting switching elements 33 and 35 operate so as to be turned on and off.
  • the minimum value of the on / off frequency fs may be higher than the maximum frequency f0 of the audible frequency band Bf.
  • the control circuit 27 When the step-down operation is performed and the output voltage Vo is lower than the input voltage Vi, the control circuit 27 is turned on / off at the on / off frequency fs instead of the time ratio control amount Ds of the step-up switching element 33 as shown in FIG.
  • a time ratio control amount De that is a time ratio of the step-down switching element 31 may be obtained.
  • the absolute values of the predetermined values Ds7, Ds6, and Ds5, which are negative values of the duty ratio control amount Ds correspond to the predetermined values De1, De2, and De3 of the duty ratio control amount De, respectively.
  • the control circuit 27 may operate as follows when the output voltage Vo is lower than the input voltage Vi. In other words, the control circuit 27 turns on the step-up switching element 33, turns off the step-up switching element 35, and turns on the step-down switching elements 30, 31 at a predetermined on / off frequency f1.
  • the hour ratio is obtained as the hour ratio control amount De.
  • the control circuit 27 steps down the voltage at the time ratio of the time ratio control amount De with the boost switching element 33 turned on and the boost switching element 35 turned off.
  • the switching elements 30, 31 are operated so as to be turned on / off at a predetermined on / off frequency f1.
  • the control circuit 27 turns on and off the step-down switching elements 30 and 31 at a predetermined on / off frequency f1 at a time ratio of the predetermined value De1 to obtain the time ratio control amount De.
  • the boosting switching elements 33 and 35 are operated to be turned on / off at the on / off frequency fb determined based on the on / off frequency fb.
  • the control circuit 27 When the output ratio Vo is lower than the input voltage Vi and the duty ratio control amount De is smaller than the predetermined value De1, the control circuit 27 performs boost switching at the on / off frequency fb with the on period of the boost switching element 35 fixed. You may operate
  • control circuit 27 switches the operation of the step-up switching elements 33 and 35 and the operation of the step-down switching elements 30 and 31 when the duty ratio control amount De becomes smaller than the predetermined value De3 smaller than the predetermined value De1. May be. That is, the control circuit 27 turns on and off the step-down switching elements 30 and 31 at the predetermined on / off frequency f1 at the time ratio of the predetermined value De1 when the time ratio control amount De is equal to or larger than the predetermined value De3 smaller than the predetermined value De1.
  • the step-up switching elements 33 and 35 may be turned on / off at the on / off frequency fb.
  • the control circuit 27 turns on and off the boosting switching elements 33 and 35 at the predetermined on / off frequency f1 at the time ratio of the predetermined value De1. It operates so as to turn on and off the step-down switching elements 30 and 31 at fb.
  • the control circuit 27 switches on / off of the step-up switching elements 33, 35 through a period in which the step-up switching elements 33, 35 are simultaneously turned off, and performs step-down switching through a period in which the step-down switching elements 30, 31 are simultaneously turned off. You may operate
  • FIG. 10 is a block circuit diagram of the DC / DC converter 11A in the second embodiment. 10, the same reference numerals are assigned to the same portions as those of DC / DC converter 11 in the first embodiment shown in FIG.
  • the DC / DC converter 11A includes a control circuit 27A instead of the control circuit 27 of the DC / DC converter 11 in the first embodiment shown in FIG.
  • the control circuit 27A turns on and off the switching elements 30, 31, 33, and 35 at a timing different from that of the control circuit 27.
  • the DC / DC converter 11A operates normally even when the output voltage Vo is very close to the input voltage Vi, like the DC / DC converter 11 in the first embodiment.
  • the operation of the DC / DC converter 11A in the second embodiment will be described more specifically.
  • FIG. 11 shows the on / off states of the step-down switching elements 30 and 31 and the step-up switching elements 33 and 35 in the step-up operation of the DC / DC converter 11A.
  • the vertical axis indicates the on and off states of each switching element, and the horizontal axis indicates time.
  • the step-up switching elements 33 and 35 are switched on and off at a predetermined on-off frequency and complementarily. Make it work. With this operation, the DC / DC converter 11A boosts the input voltage Vi and outputs the output voltage Vo.
  • the control circuit 27A sets the time ratio of the step-up switching elements 33 and 35 so that the output voltage Vo detected by the output voltage detection circuit 25 becomes a predetermined set voltage, that is, based on the output voltage Vo. Obtained by calculating as a ratio control amount.
  • the duty ratio is the ratio of the on period to one cycle of the on / off frequency of the switching element.
  • the control circuit 27A calculates the duty ratio of the boosting switching element 35 as the duty ratio control amount Ds.
  • the time ratio of the boosting switching element 33 is the number obtained by subtracting the time ratio of the boosting switching element 35 from 1 when the simultaneous off period of the boosting switching elements 33 and 35 is short, that is, the boosting switching element 35 is turned on / off.
  • the step-up switching elements 33 and 35 are complementarily turned on and off at the on / off frequency fb while the step-down switching element 30 is kept on and the step-down switching element 31 is kept off.
  • PWM control is performed by changing the above.
  • the step-up switching elements 33 and 35 operate at an on / off frequency fb of 80 kHz at a time ratio of 0.5.
  • the correlation between the duty ratio control amount Ds and the on / off frequency f is determined in advance and stored in the memory of the control circuit 27A.
  • the control circuit 27A controls the switching operation of the switching elements 30, 31, 33, and 35 based on the correlation.
  • FIG. 12 shows the correlation between the on / off frequency fs of the step-down switching elements 30 and 31, the on / off frequency fb of the step-up switching elements 33 and 35, and the time ratio control amount Ds.
  • the horizontal axis represents the duty ratio control amount Ds
  • the vertical axis represents the on / off frequency.
  • the duty ratio control amount Ds is in the range Rs11 that is equal to or greater than the predetermined value Ds11.
  • the control circuit 27A performs PWM control of the boosting switching elements 33 and 35 so that the boosting switching elements 33 and 35 perform complementary operations.
  • the duty ratio control amount Ds is the predetermined value Ds11.
  • the on / off frequency fb shown in FIG. 12 is a frequency that generates an on period in the PWM control of the step-up switching element 33, for example, as described above. Therefore, from FIG. 12, the on / off frequency fs of the step-down switching elements 30 and 31 at the time ratio control amount Ds of the predetermined value Ds11 is 0 Hz. When the on / off frequency fs is 0 Hz, the cycle is infinite, so the switching element does not perform the on / off operation. Therefore, as shown in FIG. 11, when the duty ratio control amount Ds is in the range Rs11 that is equal to or greater than the predetermined value Ds11, the control circuit 27A keeps the step-down switching element 30 on and the step-down switching element 31 is turned on. Keep off.
  • the control circuit 27A controls on / off of the step-up switching elements 33 and 35 in a cycle with a frequency of 60 kHz.
  • the control circuit 27A controls the boosting switching elements 33 and 35 in the direction of decreasing the boosting ratio.
  • the boosting switching element 33 performs a complementary operation with the boosting switching element 35 as shown in FIG.
  • the step-down switching elements 30 and 31 maintain the same state as the operation shown in FIG. 11 because the on / off frequency fs is 0 Hz when the duty ratio control amount Ds is the predetermined value Ds12 as shown in FIG.
  • the step-down switching element 30 is kept on, and the step-down switching element 31 is kept off.
  • FIG. 14 shows the on / off states of the switching elements 30, 31, 33, and 35 when the duty ratio control amount Ds is a predetermined value Ds13.
  • One period is, for example, from time t1 to time t5, and is an on period in which the period from time t4 to time t5 is fixed among the period from time t1 to time t5.
  • the boosting switching element 33 performs a complementary operation with the boosting switching element 35.
  • the duty ratio control amount Ds is a predetermined value Ds13
  • the on / off frequency fs of the step-down switching elements 30 and 31 is 0 Hz. Therefore, as shown in FIG.
  • the switching element 31 is kept off while being kept on. Therefore, the control circuit 27A further reduces the boost ratio.
  • FIG. 15 shows the on / off state of the switching elements 30, 31, 33, and 35 when the duty ratio control amount Ds is a predetermined value Ds14.
  • the control circuit 27A keeps the boosting switching element 35 off and keeps the boosting switching element 33 on. At this time, since the on / off frequency fs of the step-down switching elements 30 and 31 is 0 kHz as shown in FIG.
  • the control circuit 27A keeps the step-down switching element 30 on as shown in FIG.
  • the switching element 31 is kept off. Therefore, when the duty ratio control amount Ds is the predetermined value Ds14, the control circuit 27A stops the on / off operation of all the switching elements, and keeps only the boosting switching element 33 and the step-down switching element 30 on to increase the voltage for boosting. By keeping the switching element 35 and the step-down switching element 31 off, the input terminal 15 and the output terminal 19 are directly connected, and the input voltage Vi and the output voltage Vo are made substantially equal. Thus, since the switching operation of the switching elements 30, 31, 33, and 35 is not performed when the duty ratio control amount Ds is the predetermined value Ds14, the DC / DC converter 11A is the DC / DC converter 11 in the first embodiment. More efficient.
  • the on / off frequency fb when the duty ratio control amount Ds is the predetermined value Ds14 is not the frequency f0 (0 ⁇ f0 ⁇ 18 kHz) but 0 Hz, so that the DC / DC converter 11 in the first embodiment is used.
  • the noise can be reduced similarly to the operation when the time ratio control amount Ds is the predetermined value Ds4. If noise is not a problem, the minimum frequency of the on / off frequency fb is set to zero, and the correlation between the on / off frequency fb of the step-up switching elements 33 and 35 and the duty ratio control amount Ds is continuously obtained in the ranges Rs12 and Rs13. It may be.
  • the correlation between the on / off frequency fs of the step-down switching elements 30 and 31 and the time ratio control amount Ds is relative to the correlation between the on / off frequency fb of the step-up switching elements 33 and 35 and the time ratio control amount Ds about the vertical axis. Symmetric. As shown in FIG. 12, when the duty ratio control amount Ds reaches a predetermined value Ds4 in which the step-up switching elements 33 and 35 and the step-down switching elements 30 and 31 are ON / OFF controlled in substantially the same cycle, the control circuit 27A Switches the operation of the step-up switching elements 33 and 35 and the operation of the step-down switching elements 30 and 31.
  • the DC / DC converter 11A When the duty ratio control amount Ds is smaller than the predetermined value Ds14, the DC / DC converter 11A performs a step-down operation (Vo ⁇ Vi), and the control circuit 27A keeps the step-up switching element 33 on as shown in FIG. Then, the boosting switching element 35 is kept off.
  • the definition of the state in which the on / off control is performed at substantially the same cycle is the same as in the first embodiment. Therefore, the operation of the step-up switching elements 33 and 35 and the operation of the step-down switching elements 30 and 31 do not have to be strictly at the point when the time ratio control amount Ds reaches the predetermined value Ds14.
  • the control circuit 27A keeps the step-down switching element 30 on and keeps the step-down switching element 31 off.
  • the control circuit 27A keeps the boosting switching element 33 on and keeps the boosting switching element 35 off, the cycle becomes infinite. .
  • on / off control is defined here as including ON-only ON control and OFF-only OFF control.
  • FIG. 16 shows the on / off states of the switching elements 30, 31, 33, and 35 when the duty ratio control amount Ds is a predetermined value Ds15.
  • the step-down switching element 30 performs a complementary operation with the step-down switching element 31.
  • the control circuit 27A keeps the boosting switching element 33 on and keeps the boosting switching element 35 off.
  • FIG. 17 shows an on / off state of the switching elements 30, 31, 33, and 35 when the duty ratio control amount Ds is a predetermined value Ds16.
  • the step-down switching element 30 performs a complementary operation with the step-down switching element 31. At this time, the control circuit 27A keeps the boosting switching element 33 on and keeps the boosting switching element 35 off.
  • FIG. 18 shows an on / off state of the switching elements 30, 31, 33, and 35 when the duty ratio control amount Ds is a predetermined value Ds17.
  • the step-down switching element 30 performs a complementary operation with the step-down switching element 31.
  • the control circuit 27A keeps the boosting switching element 33 on and keeps the boosting switching element 35 off.
  • the DC / DC converter 11A smoothly switches from a step-up operation to a step-down operation through a step-up / step-down operation.
  • the control circuit 27A sets the cycle of the switching element in a state where the ON period of the PWM controlled switching element is fixed based on the correlation between the duty ratio control amount Ds and the on / off frequencies fb and fs. Since it is increased or decreased, the step-up / step-down operation can be switched with a simple operation.
  • the control circuit 27A When the amount of power generated by the DC power supply 28 is reduced from a large state, the control circuit 27A performs the reverse operation. In this case, the first predetermined value is replaced with the predetermined value Ds17, and the third predetermined value is replaced with the predetermined value Ds11.
  • the control by the control circuit 27A when switching from the step-up operation described above to the step-down operation is summarized below.
  • the step-up switching element 33 that performs the pulse width modulation control. , 35 the ON control is performed in a state in which one ON period of the step-up switching elements 33, 35 is fixed for each period obtained based on the correlation between the predetermined time ratio control amount Ds and the ON / OFF frequency fb.
  • the off control is performed with the other off period of the boosting switching elements 33 and 35 being fixed.
  • the control circuit 27A When the duty ratio control amount Ds reaches the second predetermined value Ds14 when the on / off control is not substantially performed, the control circuit 27A performs the operations of the step-up switching elements 33 and 35 and the operation of the step-down switching elements 30 and 31. Replace. When the duty ratio control amount Ds reaches the third predetermined value Ds17, the control circuit 27A performs the step-down operation by the step-down switching elements 30 and 31.
  • the pulse width modulation control is performed when the duty ratio control amount Ds reaches a first predetermined value Ds17 at which the pulse width modulation control cannot be performed from a value smaller than the first predetermined value Ds17.
  • One of the step-down switching elements 30 and 31 for each period determined based on the correlation between the predetermined time ratio control amount Ds and the on / off frequency fs. On-control is performed with the on-period of the step-down switching element 31 fixed, and off-control is performed with the off-period of the other switching element 30 of the step-down switching elements 30, 31 fixed.
  • the control circuit 27A When the duty ratio control amount Ds reaches the second predetermined value Ds14 when the on / off control is not substantially performed, the control circuit 27A performs the operations of the step-up switching elements 33 and 35 and the operation of the step-down switching elements 30 and 31. Replace. Then, when the duty ratio control amount Ds reaches the third predetermined value Ds11, the control circuit 27A performs the boosting operation by the boosting switching elements 33 and 35.
  • the control circuit 27A performs PWM control on the boosting switching elements 33 and 35 when only the boosting operation is performed, and performs PWM control on the step-down switching elements 30 and 31 when performing only the bucking operation. Take control.
  • the control circuit 27A can switch the step-up / step-down operation by controlling a total of four switching elements 30, 31, 33, and 35 based on the correlation.
  • the on period and the off control are performed with the on period fixed for each period obtained based on the correlation between the predetermined time ratio control amount Ds and the on / off frequencies fs and fb.
  • a circuit for obtaining the two triangular waves of the conventional DC / DC converter shown in FIG. 20 is not required, and a DC / DC converter 11A capable of step-up / step-down with a simple configuration is obtained.
  • the control circuit 27A operates as follows when the output voltage Vo is equal to or higher than the input voltage Vi.
  • the control circuit 27A turns on the step-down switching element 30, turns off the step-down switching element 31, and turns on and off the step-up switching elements 33 and 35 at a predetermined on / off frequency f1. Is obtained as the duty ratio control amount Ds based on the output voltage Vo.
  • the control circuit 27A boosts the time ratio control amount Ds with the time ratio while the step-down switching element 30 is turned on and the step-down switching element 31 is turned off.
  • the switching elements 33 and 35 are turned on / off at a predetermined on / off frequency f1.
  • the control circuit 27A controls the step-up switching elements 33 and 35 with the time ratio control with the step-down switching element 30 turned on and the step-down switching element 31 turned off.
  • the signal is turned on / off at an on / off frequency fb determined based on the quantity Ds.
  • the control circuit 27A When the step-down operation is performed and the output voltage Vo is lower than the input voltage Vi, the control circuit 27A is turned on / off at the on / off frequency fs instead of the time ratio control amount Ds of the step-up switching element 33 as shown in FIG.
  • a time ratio control amount De that is a time ratio of the step-down switching element 31 may be obtained.
  • the absolute values of the predetermined values Ds17, Ds16, and Ds15 that are negative values of the duty ratio control amount Ds correspond to the predetermined values De11, De12, and De13 of the duty ratio control amount De, respectively.
  • the control circuit 27A operates as follows when the output voltage Vo is lower than the input voltage Vi. That is, the control circuit 27A turns on the step-down switching element 33 in a state where the step-up switching element 33 is turned on, the step-up switching element 35 is turned off, and the step-down switching elements 30 and 31 are turned on / off at a predetermined on / off frequency f1.
  • the ratio is obtained as the duty ratio control amount De based on the output voltage Vo.
  • the control circuit 27A reduces the voltage at the time ratio of the time ratio control amount De with the boost switching element 33 turned on and the boost switching element 35 turned off.
  • the switching elements 30, 31 are turned on / off at a predetermined on / off frequency f1.
  • the control circuit 27A controls the step-down switching elements 30 and 31 with the time ratio control while the step-up switching element 33 is turned on and the step-up switching element 35 is turned off.
  • the on / off frequency fs determined based on the quantity De is turned on / off.
  • the control circuit 27A turns on the boost switching element 33 and the step-down switching element 30 at the same time, and sets the boost switching element 35 and the step-down switching element 31 to May be turned off simultaneously.
  • the minimum value of the on / off frequency fb and the minimum value of the on / off frequency fs may be higher than the maximum frequency f0 of the audible frequency band Bf.
  • the control circuit 27A switches on / off of the step-up switching elements 33, 35 through a period in which the step-up switching elements 33, 35 are simultaneously turned off, and performs step-down switching through a period in which the step-down switching elements 30, 31 are simultaneously turned off.
  • the elements 30 and 31 may be switched on / off.
  • the on-control of the step-down switching element 31 that has not been turned on / off until the operation shown in FIGS. .25 ⁇ s) is fixed.
  • the frequency is calculated
  • the pulses of the step-down switching elements 30 and 31 that are not PWM-controlled by the step-up operation are applied.
  • PWM control is performed on the step-down switching elements 30 and 31.
  • the step-up switching elements 33, 35) that have been PWM-controlled by the step-up operation perform the reverse operation of the step-down switching elements 30, 31.
  • the ON period of the step-up switching element 33 that has been PWM-controlled by the step-up operation is fixed in the operation shown in FIGS.
  • the turn-on and turn-on periods are determined by the correlation shown in FIG. Thereby, the pulse of the step-up switching element 33 decreases.
  • the step-up switching element 33 maintains the on state.
  • the step-up switching element 35 performs an operation complementary to the step-up switching element 33. Further, the step-down switching elements 30 and 31 perform the reverse operation of the step-up switching elements 33 and 35 as shown in FIG.
  • the step-up / step-down switching is performed by controlling the pulse of the switching element that is not subjected to the PWM control for performing the step-up operation or the step-down operation.
  • the step-up / step-down switching is performed by controlling the pulse of the switching element that is PWM controlled to perform the step-up operation or the step-down operation. Regardless of which control is employed, the DC / DC converters 11 and 11A that can switch between the ascending operation and the step-down operation with a simple configuration can be obtained.
  • the step-down switching elements 33 and 35 are switched on and off through the simultaneous off period in which the step-up switching elements 33 and 35 are simultaneously turned off.
  • the on / off may be switched through a simultaneous off period in which the switching elements 30, 31 are turned off at the same time.
  • the control circuit 27A maintains the step-down switching elements 30 and 31 on or off when the duty ratio control amount Ds is equal to or greater than the predetermined value Ds14, and the on / off frequency fs.
  • the duty ratio control amount Ds is equal to or less than the predetermined value Ds14, the step-up switching elements 33 and 35 are kept on or off, and the on / off frequency fb is made zero.
  • the on / off frequencies fs and fb change linearly with the time ratio control amount Ds in the above correlation, but the present invention is not limited to this.
  • the on / off frequencies fs and fb together with the duty ratio control amount Ds may be changed in another relationship instead of linear.
  • the DC power supply 28 connected to the DC / DC converters 11 and 11A in the first and second embodiments is a solar cell.
  • the DC power supply 28 may be a configuration in which the input voltage Vi greatly varies with respect to the desired output voltage Vo and requires a step-up / step-down operation, for example, a secondary battery.
  • the DC / DC converters 11 and 11A are secondary batteries. You may apply to the charging / discharging circuit etc. of a battery.
  • the DC / DC converter according to the present invention can perform both step-up and step-down operations, it is particularly useful as a DC / DC converter for a DC power source such as a solar cell having a large input voltage fluctuation.
  • Step-down switching element (first step-down switching element) 30P connection point (first connection point) 31 Step-down switching element (second step-down switching element) 33 Boosting switching element (first boosting switching element) 33P connection point (second connection point) 35 Boosting switching element (second boosting switching element) De time ratio control amount (second time ratio control amount) De1 predetermined value (second predetermined value) De3 predetermined value (third predetermined value) De11 predetermined value (second predetermined value) Ds time ratio control amount (first time ratio control amount) Ds1 predetermined value (first predetermined value) Ds3 predetermined value (second predetermined value) Ds11 predetermined value (first predetermined value) f1 On / off frequency (predetermined on / off frequency) fb On / off frequency (second on / off frequency) fs On / off frequency (first on / off frequency)

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Abstract

This DC/DC converter is provided with a step-down switching element, a step-up switching element, and a control circuit. The control circuit, on the basis of the output voltage, obtains the duty ratio of the step-up switching element as a duty ratio control quantity, and operates so as to switch the step-up switching element on/off at a predetermined on/off frequency, and to switch the step-down switching element on/off at a frequency determined on the basis of the duty ratio control quantity. Alternatively, the control circuit, on the basis of the output voltage, obtains the duty ratio of the step-down switching element as a duty ratio control quantity, and operates so as to switch the step-down switching element on/off at a predetermined on/off frequency, and to switch the step-up switching element on/off at a frequency determined on the basis of the duty ratio control quantity. This DC/DC converter operates normally, even in instances in which the output voltage is extremely close to the input voltage.

Description

ＤＣ／ＤＣコンバータDC / DC converter
　本発明はＤＣ／ＤＣコンバータに関する。 The present invention relates to a DC / DC converter.
　図１９は特許文献１に記載されている従来のＤＣ／ＤＣコンバータ１０１であるバックブースト切換調整器の模式図である。ＤＣ／ＤＣコンバータ１０１は、入力された電圧を昇圧および降圧することにより所望の出力電圧を得ることが可能な昇降圧型のＤＣ／ＤＣコンバータである。ＤＣ／ＤＣコンバータ１０１は、同期型切換調整器１０３および制御回路１０５を含む。同期型切換調整器１０３は、入力電圧Ｖｉｎを受け取り、調整された出力電圧Ｖｏｕｔを提供する。入力電圧Ｖｉｎは、出力電圧Ｖｏｕｔよりも高いか、低いか、あるいは実質的に同じであり得る。制御回路１０５は、同期型切換調整器１０３をバックモード、ブーストモードまたはバックブーストモードで動作させ得る。同期型切換調整器１０３は、電圧Ｖｉｎ、Ｖｏｕｔの間に結合された４つのスイッチ１０７、１０９、１１１、１１３を有する。スイッチ１０７、１０９、１１１、１１３は、電圧Ｖｏｕｔにある出力ノードへの電流の供給量を制御し、これにより、出力電圧Ｖｏｕｔは調整値で保持され得る。制御回路１０５は、出力電圧Ｖｏｕｔを受け取り、同期型切換調整器１０３内の４つのスイッチ１０７、１０９、１１１、１１３の切り換えをそれぞれ制御する４つの駆動信号ＶＡ、ＶＢ、ＶＣ、ＶＤを提供する。制御回路１０５は、抵抗器１１５および１１７と、誤り増幅器１１９と、パルス幅変調器１２１と、論理回路１２３とを含む。パルス幅変調器１２１は、信号発生器１２５とコンパレータ１２７および１２９とを含む。 FIG. 19 is a schematic diagram of a buck-boost switching regulator which is a conventional DC / DC converter 101 described in Patent Document 1. In FIG. The DC / DC converter 101 is a step-up / step-down DC / DC converter that can obtain a desired output voltage by stepping up and stepping down an input voltage. The DC / DC converter 101 includes a synchronous switching regulator 103 and a control circuit 105. The synchronous switching regulator 103 receives the input voltage Vin and provides a regulated output voltage Vout. The input voltage Vin can be higher, lower or substantially the same as the output voltage Vout. The control circuit 105 can operate the synchronous switching regulator 103 in the buck mode, the boost mode, or the buck-boost mode. Synchronous switching regulator 103 has four switches 107, 109, 111, 113 coupled between voltages Vin, Vout. The switches 107, 109, 111, and 113 control the amount of current supplied to the output node at the voltage Vout, whereby the output voltage Vout can be held at the adjusted value. The control circuit 105 receives the output voltage Vout and controls four drive signals V A , V B , V C , and V D that control switching of the four switches 107, 109, 111, and 113 in the synchronous switching regulator 103, respectively. I will provide a. Control circuit 105 includes resistors 115 and 117, error amplifier 119, pulse width modulator 121, and logic circuit 123. Pulse width modulator 121 includes a signal generator 125 and comparators 127 and 129.
　次に、ＤＣ／ＤＣコンバータ１０１の動作について説明する。図２０はＤＣ／ＤＣコンバータ１０１の信号を示す。図２０のグラフにおいて、横軸は時間を示し、縦軸は電圧を示す。 Next, the operation of the DC / DC converter 101 will be described. FIG. 20 shows a signal of the DC / DC converter 101. In the graph of FIG. 20, the horizontal axis indicates time, and the vertical axis indicates voltage.
　図２０は、図１９に示すコンパレータ１２７に入力される電圧ＶＸ、ＶＹならびに制御電圧ＶＣＬを示す。電圧ＶＸは周期Ｔを有し、最小値Ｖ１および最大値Ｖ３を有する三角波形である。波形信号ＶＹは、周期Ｔを有し、最小値Ｖ２および最大値Ｖ４を有する三角波形である。また、図２０に示すように、電圧の値Ｖ１～Ｖ４はＶ１＜Ｖ２＜Ｖ３＜Ｖ４の関係を満たす。Ｖ１＜ＶＣＬ≦Ｖ２の場合、制御回路１０５により制御される同期型切換調整器１０３はバックモードで動作し、Ｖ２＜ＶＣＬ＜Ｖ３の場合、制御回路１０５により制御される同期型切換調整器１０３はバックブーストモードで動作し、Ｖ３≦ＶＣＬ＜Ｖ４の場合、制御回路１０５により制御される同期型切換調整器１０３はブーストモードで動作する。ＶＣＬ≦Ｖ１またはＶＣＬ≧Ｖ４である場合、同期型切換調整器１０３は縮退モードで動作する。このような動作により、コンパレータ１２７、１２９がそれぞれ出力する電圧ＶＺ１、ＶＡ２と駆動信号ＶＡ～ＶＤは図２０に示すように変化する。 FIG. 20 shows voltages V X and V Y and a control voltage V CL input to the comparator 127 shown in FIG. The voltage V X has a period T and is a triangular waveform having a minimum value V 1 and a maximum value V 3 . Waveform signal V Y has a period T, it is a triangular waveform having a minimum value V 2 and a maximum value V 4. Further, as shown in FIG. 20, the voltage values V 1 to V 4 satisfy the relationship of V 1 <V 2 <V 3 <V 4 . When V 1 <V CL ≦ V 2 , the synchronous switching regulator 103 controlled by the control circuit 105 operates in the back mode, and when V 2 <V CL <V 3 , the synchronization controlled by the control circuit 105. The type switching regulator 103 operates in the buck-boost mode, and when V 3 ≦ V CL <V 4 , the synchronous switching regulator 103 controlled by the control circuit 105 operates in the boost mode. If a V CL ≦ V 1 or V CL ≧ V 4, the synchronous switching regulator 103 operates in a degraded mode. By such an operation, the voltages V Z1 and V A2 and the drive signals V A to V D output from the comparators 127 and 129 change as shown in FIG.
　図１９に示す従来のＤＣ／ＤＣコンバータ１０１は回路構成が複雑になる。 The circuit configuration of the conventional DC / DC converter 101 shown in FIG.
特許第４９０３９４５号公報Japanese Patent No. 4903945
　ＤＣ／ＤＣコンバータは降圧用スイッチング素子と昇圧用スイッチング素子と制御回路とを備える。制御回路は、昇圧用スイッチング素子の時比率を時比率制御量として出力電圧に基づいて得て、昇圧用スイッチング素子を所定のオンオフ周波数でオンオフし、時比率制御量に基づいて決定された周波数で降圧用スイッチング素子をオンオフするように動作する。または、制御回路は、降圧用スイッチング素子の時比率を時比率制御量として出力電圧に基づいて得て、降圧用スイッチング素子を所定のオンオフ周波数でオンオフし、時比率制御量に基づいて決定された周波数で昇圧用スイッチング素子をオンオフするように動作する。 The DC / DC converter includes a step-down switching element, a step-up switching element, and a control circuit. The control circuit obtains the time ratio of the boosting switching element as a time ratio control amount based on the output voltage, turns on and off the boosting switching element at a predetermined on / off frequency, and at a frequency determined based on the time ratio control amount. It operates to turn on and off the step-down switching element. Alternatively, the control circuit obtains the time ratio of the step-down switching element as a time ratio control amount based on the output voltage, turns on and off the step-down switching element at a predetermined on / off frequency, and is determined based on the time ratio control amount It operates to turn on and off the step-up switching element at a frequency.
　このＤＣ／ＤＣコンバータは、出力電圧が入力電圧に非常に近い場合でも正常に動作する。 This DC / DC converter operates normally even when the output voltage is very close to the input voltage.
図１は実施の形態１におけるＤＣ／ＤＣコンバータのブロック回路図である。FIG. 1 is a block circuit diagram of the DC / DC converter according to the first embodiment. 図２は実施の形態１におけるＤＣ／ＤＣコンバータの昇圧動作におけるスイッチング素子のタイミングチャートである。FIG. 2 is a timing chart of the switching elements in the step-up operation of the DC / DC converter in the first embodiment. 図３は実施の形態１におけるＤＣ／ＤＣコンバータの時比率制御量とオンオフ周波数との相関関係を示す図である。FIG. 3 is a diagram showing the correlation between the duty ratio control amount and the on / off frequency of the DC / DC converter in the first embodiment. 図４は実施の形態１におけるＤＣ／ＤＣコンバータの昇圧動作時におけるスイッチング素子のタイミングチャートである。FIG. 4 is a timing chart of the switching element during the step-up operation of the DC / DC converter in the first embodiment. 図５は実施の形態１におけるＤＣ／ＤＣコンバータの昇圧動作におけるスイッチング素子のタイミングチャートである。FIG. 5 is a timing chart of the switching elements in the step-up operation of the DC / DC converter in the first embodiment. 図６は実施の形態１におけるＤＣ／ＤＣコンバータの昇降圧動作の切替時におけるスイッチング素子のタイミングチャートである。FIG. 6 is a timing chart of the switching element at the time of switching of the step-up / step-down operation of the DC / DC converter in the first embodiment. 図７は実施の形態１におけるＤＣ／ＤＣコンバータの降圧動作におけるスイッチング素子のタイミングチャートである。FIG. 7 is a timing chart of the switching elements in the step-down operation of the DC / DC converter in the first embodiment. 図８は実施の形態１におけるＤＣ／ＤＣコンバータの降圧動作におけるスイッチング素子のタイミングチャートである。FIG. 8 is a timing chart of the switching element in the step-down operation of the DC / DC converter in the first embodiment. 図９は実施の形態１におけるＤＣ／ＤＣコンバータの降圧動作におけるスイッチング素子のタイミングチャートである。FIG. 9 is a timing chart of the switching elements in the step-down operation of the DC / DC converter in the first embodiment. 図１０は実施の形態２におけるＤＣ／ＤＣコンバータのブロック回路図である。FIG. 10 is a block circuit diagram of the DC / DC converter according to the second embodiment. 図１１は実施の形態２におけるＤＣ／ＤＣコンバータの昇圧動作におけるスイッチング素子のタイミングチャートである。FIG. 11 is a timing chart of the switching elements in the step-up operation of the DC / DC converter according to the second embodiment. 図１２は実施の形態２におけるＤＣ／ＤＣコンバータの時比率制御量とオンオフ周波数との相関関係を示す図である。FIG. 12 is a diagram showing the correlation between the duty ratio control amount and the on / off frequency of the DC / DC converter in the second embodiment. 図１３は実施の形態２におけるＤＣ／ＤＣコンバータの昇圧動作におけるスイッチング素子のタイミングチャートである。FIG. 13 is a timing chart of the switching elements in the step-up operation of the DC / DC converter according to the second embodiment. 図１４は実施の形態２におけるＤＣ／ＤＣコンバータの昇圧動作におけるスイッチング素子のタイミングチャートである。FIG. 14 is a timing chart of the switching elements in the step-up operation of the DC / DC converter according to the second embodiment. 図１５は実施の形態２におけるＤＣ／ＤＣコンバータの昇降圧切替時におけるスイッチング素子のタイミングチャートである。FIG. 15 is a timing chart of the switching elements at the time of step-up / step-down switching of the DC / DC converter in the second embodiment. 図１６は実施の形態２におけるＤＣ／ＤＣコンバータの降圧動作におけるスイッチング素子タイミングチャートである。FIG. 16 is a switching element timing chart in the step-down operation of the DC / DC converter in the second embodiment. 図１７は実施の形態２におけるＤＣ／ＤＣコンバータの降圧動作におけるスイッチング素子のタイミングチャートである。FIG. 17 is a timing chart of the switching elements in the step-down operation of the DC / DC converter according to the second embodiment. 図１８は実施の形態２におけるＤＣ／ＤＣコンバータの降圧動作におけるスイッチング素子のタイミングチャートである。FIG. 18 is a timing chart of the switching elements in the step-down operation of the DC / DC converter according to the second embodiment. 図１９は従来のＤＣ／ＤＣコンバータの模式図である。FIG. 19 is a schematic diagram of a conventional DC / DC converter. 図２０は従来のＤＣ／ＤＣコンバータの信号を示す図である。FIG. 20 is a diagram showing signals of a conventional DC / DC converter.
　（実施の形態１）
　図１は実施の形態１におけるＤＣ／ＤＣコンバータ１１のブロック回路図である。ＤＣ／ＤＣコンバータ１１は、入力端子１５と、出力端子１９と、グランド端子１７と、入力端子１５と接続点３０Ｐとの間に電気的に直列に入力端子１５と接続点３０Ｐとに接続された降圧用スイッチング素子３０と、接続点３０Ｐとグランド端子１７との間に電気的に直列に接続点３０Ｐとグランド端子１７とに接続された降圧用スイッチング素子３１と、出力端子１９と接続点３３Ｐとの間に電気的に直列に出力端子１９と接続点３３Ｐとに接続された昇圧用スイッチング素子３３と、接続点３３Ｐとグランド端子１７との間に電気的に直列に接続点３３Ｐとグランド端子１７とに接続された昇圧用スイッチング素子３５と、接続点３０Ｐ、３３Ｐの間に電気的に直列に接続点３０Ｐ、３３Ｐに接続されたインダクタ２１と、入力端子１５と電気的に接続された入力電圧検出回路２３と、出力端子１９と電気的に接続され出力電圧検出回路２５と、降圧用スイッチング素子３０、３１と昇圧用スイッチング素子３３、３５と入力電圧検出回路２３と出力電圧検出回路２５と電気的に接続された制御回路２７とを備える。入力電圧検出回路２３は入力端子１５の入力電圧Ｖｉを検出する。出力電圧検出回路２５は出力端子１９の出力電圧Ｖｏを検出する。 (Embodiment 1)
FIG. 1 is a block circuit diagram of a DC / DC converter 11 according to the first embodiment. The DC / DC converter 11 is connected to the input terminal 15 and the connection point 30P electrically in series between the input terminal 15, the output terminal 19, the ground terminal 17, and the input terminal 15 and the connection point 30P. The step-down switching element 30, the step-down switching element 31 electrically connected in series between the connection point 30P and the ground terminal 17, and the output terminal 19 and the connection point 33P are connected to the connection point 30P and the ground terminal 17. The step-up switching element 33 electrically connected in series between the output terminal 19 and the connection point 33P, and the connection point 33P and the ground terminal 17 electrically connected in series between the connection point 33P and the ground terminal 17. The step-up switching element 35 connected to each other, the inductor 21 electrically connected in series between the connection points 30P and 33P, and the input terminal 5, an input voltage detection circuit 23 electrically connected to the output terminal 19, an output voltage detection circuit 25 electrically connected to the output terminal 19, step- down switching elements 30 and 31, step-up switching elements 33 and 35, and input voltage detection A control circuit 27 electrically connected to the circuit 23 and the output voltage detection circuit 25 is provided. The input voltage detection circuit 23 detects the input voltage Vi at the input terminal 15. The output voltage detection circuit 25 detects the output voltage Vo at the output terminal 19.
　図１に示すように、入力端子１５とグランド端子１７の間には直流電源２８が電気的に接続されている。実施の形態１では、直流電源２８は太陽電池である。ＤＣ／ＤＣコンバータ１１は直流電源２８（太陽電池）が発電した入力電圧Ｖｉを昇圧もしくは降圧することにより、天候や陰影に影響されにくい安定した出力電圧Ｖｏを出力することができる。 As shown in FIG. 1, a DC power supply 28 is electrically connected between the input terminal 15 and the ground terminal 17. In the first embodiment, DC power supply 28 is a solar cell. The DC / DC converter 11 can output a stable output voltage Vo that is not easily affected by the weather or shadow by boosting or stepping down the input voltage Vi generated by the DC power supply 28 (solar cell).
　出力端子１９とグランド端子１７の間には、例えば、負荷、二次電池、あるいは商用の系統電力に電力を供給するためのインバータなどを接続することができるが、実施の形態１では特に限定しない。 For example, a load, a secondary battery, or an inverter for supplying power to commercial system power can be connected between the output terminal 19 and the ground terminal 17, but the embodiment 1 is not particularly limited. .
　次に、ＤＣ／ＤＣコンバータ１１の内部構成の詳細について説明する。 Next, the details of the internal configuration of the DC / DC converter 11 will be described.
　降圧用スイッチング素子３０、３１は接続点３０Ｐで互いに直列に接続されている。降圧用スイッチング素子３０、３１は相補な動作を行う。相補な動作とは、基本的に、降圧用スイッチング素子３０、３１のオンオフの状態が互いに異なる動作である。但し、降圧用スイッチング素子３０、３１が短期間内に同時にオフとなる場合は一時的に相補な動作を行っていないが、実施の形態１では短期間の同時のオフは相補な動作に含まれる。実施の形態１では、相補な動作では、降圧用スイッチング素子３０、３１のオンとオフの状態は、降圧用スイッチング素子３０、３１がともにオフである同時オフの状態を介して遷移する。具体的には、降圧用スイッチング素子３０、３１のうちの一方がオンであるときに他方がオフである。さらに、同時のオフが行われない場合には、降圧用スイッチング素子３０、３１のうちの一方がオフであるときに他方がオンである。しかし同時のオフが行われる場合には、降圧用スイッチング素子３０、３１のうちの一方がオフであるときに他方がオンであるとは限らず、同時にオフの期間ではオフである。制御回路２７がスイッチング素子３０、３１を相補的にオンオフさせる場合には、スイッチング素子３０、３１の同時オフ期間やスイッチング速度の関係でスイッチング素子３０、３１のオン期間はある最小値より小さくすることはできず、そのオン期間をその最小値以上にするかもしくはスイッチング素子３０、３１をオフにすることはできる。 The step- down switching elements 30 and 31 are connected in series at a connection point 30P. The step- down switching elements 30 and 31 perform complementary operations. The complementary operation is basically an operation in which the on / off states of the step-down switching elements 30 and 31 are different from each other. However, if the step-down switching elements 30 and 31 are simultaneously turned off within a short period, the complementary operation is not temporarily performed. However, in the first embodiment, the short-time simultaneous off is included in the complementary operation. . In the first embodiment, in the complementary operation, the on and off states of the step-down switching elements 30 and 31 are changed through the simultaneous off state in which both the step-down switching elements 30 and 31 are off. Specifically, when one of the step-down switching elements 30 and 31 is on, the other is off. Further, when simultaneous off is not performed, when one of the step-down switching elements 30 and 31 is off, the other is on. However, when simultaneous off is performed, when one of the step-down switching elements 30 and 31 is off, the other is not necessarily on, and is off during the off period at the same time. When the control circuit 27 turns on and off the switching elements 30 and 31 in a complementary manner, the on period of the switching elements 30 and 31 should be smaller than a certain minimum value due to the simultaneous off period of the switching elements 30 and 31 and the switching speed. It is not possible to set the ON period longer than the minimum value, or the switching elements 30 and 31 can be turned OFF.
　同様に、昇圧用スイッチング素子３３、３５は降圧用スイッチング素子３０、３１と同様の相補な動作を行う。制御回路２７がスイッチング素子３３、３５を相補的にオンオフさせる場合には、スイッチング素子３３、３５の同時オフ期間やスイッチング速度の関係でスイッチング素子３３、３５のオン期間はある最小値より小さくすることはできず、そのオン期間をその最小値以上にするかもしくはスイッチング素子３３、３５をオフにすることはできる。実施の形態１ではスイッチング素子３０、３１、３３、３５は電界効果トランジスタ（以下、ＦＥＴという）を用いる。したがって、スイッチング素子３０、３１、３３、３５には寄生ダイオード３０Ｄ、３１Ｄ、３３Ｄ、３５Ｄがそれぞれ並列に接続されている。なお、スイッチング素子はＦＥＴに限定されるものではなく、他の半導体スイッチング素子であってもよい。 Similarly, the step-up switching elements 33 and 35 perform the same complementary operation as the step-down switching elements 30 and 31. When the control circuit 27 turns on and off the switching elements 33 and 35 in a complementary manner, the on period of the switching elements 33 and 35 should be smaller than a certain minimum value due to the simultaneous off period of the switching elements 33 and 35 and the switching speed. It is not possible to set the ON period longer than the minimum value, or the switching elements 33 and 35 can be turned OFF. In the first embodiment, switching elements 30, 31, 33, and 35 use field effect transistors (hereinafter referred to as FETs). Therefore, parasitic diodes 30D, 31D, 33D, and 35D are connected in parallel to the switching elements 30, 31, 33, and 35, respectively. Note that the switching element is not limited to the FET, and may be another semiconductor switching element.
　出力端子１９とグランド端子１７との間には平滑コンデンサ３７が電気的に接続される。平滑コンデンサ３７は、出力端子１９とグランド端子１７との間に容量が極めて大きい二次電池などが接続される場合は接続されていなくてもよい。 A smoothing capacitor 37 is electrically connected between the output terminal 19 and the ground terminal 17. The smoothing capacitor 37 may not be connected when a secondary battery having a very large capacity is connected between the output terminal 19 and the ground terminal 17.
　入力電圧検出回路２３は、グランド端子１７の電位を基準とした入力電圧Ｖｉを検出し、制御回路２７へ出力する。同様に、出力電圧検出回路２５は、グランド端子１７の電位を基準とした出力電圧Ｖｏを検出し、制御回路２７へ出力する。 The input voltage detection circuit 23 detects the input voltage Vi based on the potential of the ground terminal 17 and outputs it to the control circuit 27. Similarly, the output voltage detection circuit 25 detects the output voltage Vo based on the potential of the ground terminal 17 and outputs it to the control circuit 27.
　制御回路２７は、マイクロコンピュータと周辺回路、メモリ等で構成され、入力電圧Ｖｉと出力電圧Ｖｏを取り込むとともに、スイッチ信号ＳＷ１、ＳＷ２で降圧用スイッチング素子３０、３１をそれぞれオンオフし、スイッチ信号ＳＷ３、ＳＷ４で昇圧用スイッチング素子３３、３５をそれぞれオンオフする。 The control circuit 27 includes a microcomputer, a peripheral circuit, a memory, and the like. The control circuit 27 takes in the input voltage Vi and the output voltage Vo, and turns on and off the step-down switching elements 30 and 31 with the switch signals SW1 and SW2, respectively. The step-up switching elements 33 and 35 are turned on and off by SW4.
　次に、ＤＣ／ＤＣコンバータ１１の動作について説明する。 Next, the operation of the DC / DC converter 11 will be described.
　まず、ＤＣ／ＤＣコンバータ１１の昇圧動作について述べる。図２はＤＣ／ＤＣコンバータ１１の昇圧動作での降圧用スイッチング素子３０、３１と昇圧用スイッチング素子３３、３５のオンオフの状態を示す。図２において、縦軸は各スイッチング素子のオンとオフの状態を示し、横軸は時刻を示す。昇圧動作では、制御回路２７は、図２に示すように、昇圧用スイッチング素子３３、３５を所定のオンオフ周波数でオンオフを切り替えてかつ相補に動作させる。この動作により、ＤＣ／ＤＣコンバータ１１は、入力電圧Ｖｉを昇圧して出力電圧Ｖｏを出力する。このとき、制御回路２７は、出力電圧検出回路２５で検出された出力電圧Ｖｏが所定の設定電圧になるように、すなわち出力電圧Ｖｏに基づいて、昇圧用スイッチング素子３３、３５の時比率を時比率制御量として算出して得る。時比率とは、スイッチング素子のオンオフ周波数の１周期に対するオン期間の比率である。特に、制御回路２７は昇圧用スイッチング素子３５の時比率を時比率制御量Ｄｓとして算出して得る。昇圧用スイッチング素子３３の時比率は、昇圧用スイッチング素子３３、３５の同時オフ期間が短い場合には、昇圧用スイッチング素子３５の時比率を１から引いた数、すなわち昇圧用スイッチング素子３５のオンオフ周波数の１周期に対するオフ期間の比率にほぼ等しい。図２に示す動作では、スイッチング素子３３、３５のそれぞれのオン期間とオフ期間が等しいので時比率は０．５である。ＤＣ／ＤＣコンバータ１１は、制御回路２７が時比率を変更するパルス幅変調（ＰＷＭ）制御により出力電圧Ｖｏの入力電圧Ｖｉに対する比である昇圧比を調整して、出力電圧Ｖｏを所定の設定電圧にする。 First, the boosting operation of the DC / DC converter 11 will be described. FIG. 2 shows the on / off states of the step-down switching elements 30 and 31 and the step-up switching elements 33 and 35 in the step-up operation of the DC / DC converter 11. In FIG. 2, the vertical axis indicates the on and off states of each switching element, and the horizontal axis indicates time. In the step-up operation, as shown in FIG. 2, the control circuit 27 switches the step-up switching elements 33 and 35 on and off at a predetermined on / off frequency and operates them in a complementary manner. By this operation, the DC / DC converter 11 boosts the input voltage Vi and outputs the output voltage Vo. At this time, the control circuit 27 sets the time ratio of the step-up switching elements 33 and 35 so that the output voltage Vo detected by the output voltage detection circuit 25 becomes a predetermined set voltage, that is, based on the output voltage Vo. Obtained by calculating as a ratio control amount. The duty ratio is the ratio of the on period to one cycle of the on / off frequency of the switching element. In particular, the control circuit 27 calculates the duty ratio of the boosting switching element 35 as the duty ratio control amount Ds. The time ratio of the boosting switching element 33 is the number obtained by subtracting the time ratio of the boosting switching element 35 from 1 when the simultaneous off period of the boosting switching elements 33 and 35 is short, that is, the boosting switching element 35 is turned on / off. It is approximately equal to the ratio of the off period to one period of the frequency. In the operation shown in FIG. 2, since the ON period and the OFF period of each of the switching elements 33 and 35 are equal, the duty ratio is 0.5. The DC / DC converter 11 adjusts the step-up ratio, which is the ratio of the output voltage Vo to the input voltage Vi, by pulse width modulation (PWM) control in which the control circuit 27 changes the time ratio, and sets the output voltage Vo to a predetermined set voltage. To.
　一方、昇圧動作では、制御回路２７は降圧用スイッチング素子３０、３１を所定の周波数でオンオフ制御せず、図２に示すように、入力電圧Ｖｉが直接インダクタ２１に印加されるように降圧用スイッチング素子３０をオンにするとともに、入力端子１５とグランド端子１７とが短絡しないように降圧用スイッチング素子３１をオフにする。 On the other hand, in the step-up operation, the control circuit 27 does not perform on-off control of the step-down switching elements 30 and 31 at a predetermined frequency, and the step-down switching is performed so that the input voltage Vi is directly applied to the inductor 21 as shown in FIG. The element 30 is turned on, and the step-down switching element 31 is turned off so that the input terminal 15 and the ground terminal 17 are not short-circuited.
　このような動作は、例えば日の出、夕暮れ、曇天、あるいは影が差した場合などで、直流電源２８（太陽電池）へ入射する日射量が不十分であり、入力電圧Ｖｉが所望の出力電圧Ｖｏより低い場合に行われる。 Such an operation is, for example, in the case of sunrise, dusk, cloudy weather, or shadows, and the amount of solar radiation incident on the DC power supply 28 (solar cell) is insufficient, and the input voltage Vi is higher than the desired output voltage Vo. Done when low.
　次に、直流電源２８への日射量が改善され、入力電圧Ｖｉが上昇してきた場合のＤＣ／ＤＣコンバータ１１の動作について説明する。この場合、ＤＣ／ＤＣコンバータ１１は昇圧動作から降圧動作へ切り替わる。 Next, the operation of the DC / DC converter 11 when the amount of solar radiation to the DC power supply 28 is improved and the input voltage Vi increases will be described. In this case, the DC / DC converter 11 is switched from the step-up operation to the step-down operation.
　実施の形態１のＤＣ／ＤＣコンバータ１１では、時比率制御量Ｄｓとオンオフ周波数との相関関係が予め決定されており、その相関関係は制御回路２７のメモリに記憶されている。ＤＣ／ＤＣコンバータ１１の昇圧動作と降圧動作を切り替える際には、その相関関係に基づいて制御回路２７はスイッチング素子３０、３１、３３、３５のスイッチング動作を制御する。以下に、スイッチング素子３０、３１、３３、３５のスイッチング動作につき説明する。図３は降圧用スイッチング素子３０、３１のオンオフ周波数ｆｓと、昇圧用スイッチング素子３３、３５のオンオフ周波数ｆｂと、時比率制御量Ｄｓとの相関関係を示す。図３において、横軸は時比率制御量Ｄｓを示し、縦軸はオンオフ周波数を示す。 In the DC / DC converter 11 of the first embodiment, the correlation between the duty ratio control amount Ds and the on / off frequency is determined in advance, and the correlation is stored in the memory of the control circuit 27. When switching between the step-up operation and the step-down operation of the DC / DC converter 11, the control circuit 27 controls the switching operation of the switching elements 30, 31, 33 and 35 based on the correlation. Hereinafter, switching operations of the switching elements 30, 31, 33, and 35 will be described. FIG. 3 shows the correlation between the on / off frequency fs of the step-down switching elements 30 and 31, the on / off frequency fb of the step-up switching elements 33 and 35, and the time ratio control amount Ds. In FIG. 3, the horizontal axis represents the duty ratio control amount Ds, and the vertical axis represents the on / off frequency.
　図３を参照してＤＣ／ＤＣコンバータ１１の図２に示す動作について説明する。上述のように、制御回路２７が昇圧用スイッチング素子３３、３５を相補的にオンオフさせる場合には昇圧用スイッチング素子３３、３５のオン期間はある最小値より小さくすることはできない。したがって、制御回路２７が昇圧用スイッチング素子３３、３５をオンオフ周波数で相補的にオンオフさせる場合には、昇圧用スイッチング素子３５のオン期間の上記最小値以上である所定値Ｄｓ１以上の時比率で昇圧用スイッチング素子３５をオンオフさせるように昇圧用スイッチング素子３３、３５をオンオフ周波数で相補的にオンオフさせる。図２に示す動作では、図３に示す時比率制御量Ｄｓは所定値Ｄｓ１以上である範囲Ｒｓ１に入っている。図２に示す動作では、時比率制御量Ｄｓが所定値Ｄｓ１以上である範囲Ｒｓ１にあるときには、制御回路２７は、昇圧用スイッチング素子３５の時比率が所定値Ｄｓ１である状態でオンオフ周波数ｆ１にて昇圧用スイッチング素子３３、３５を相補的にオンオフさせ、すなわち、ＰＷＭ制御で昇圧用スイッチング素子３３、３５に相補な動作を行わせる。 The operation of the DC / DC converter 11 shown in FIG. 2 will be described with reference to FIG. As described above, when the control circuit 27 complementarily turns on and off the boosting switching elements 33 and 35, the ON period of the boosting switching elements 33 and 35 cannot be made smaller than a certain minimum value. Accordingly, when the control circuit 27 complementarily turns on and off the boosting switching elements 33 and 35 at the on / off frequency, the boosting switching element 35 is boosted at a time ratio equal to or greater than the predetermined value Ds1 that is equal to or greater than the minimum value of the on period of the boosting switching element 35 The boosting switching elements 33 and 35 are complementarily turned on and off at the on / off frequency so that the switching element 35 is turned on and off. In the operation shown in FIG. 2, the duty ratio control amount Ds shown in FIG. 3 is in a range Rs1 that is equal to or greater than a predetermined value Ds1. In the operation shown in FIG. 2, when the duty ratio control amount Ds is in the range Rs1 that is equal to or greater than the predetermined value Ds1, the control circuit 27 sets the on / off frequency f1 in a state where the duty ratio of the boosting switching element 35 is the predetermined value Ds1. Thus, the boosting switching elements 33 and 35 are complementarily turned on and off, that is, the boosting switching elements 33 and 35 are operated in a complementary manner by PWM control.
　実施の形態１においては、昇圧用スイッチング素子３３、３５がＰＷＭ制御される範囲Ｒｓ１ではオンオフ周波数ｆ１は８０ｋＨｚである。実施の形態１では、昇圧用スイッチング素子３５の時比率の最小値である所定値Ｄｓ１は０．５である。図２に示す動作では、昇圧用スイッチング素子３５の時比率が所定値Ｄｓ１である。周波数８０ｋＨｚの周期は１２．５μ秒であるので、制御回路２７は時比率０．５のパルス波形を発生して１２．５μ秒毎に６．２５μ秒のオン期間だけ昇圧用スイッチング素子３５をオンにする。同時に、制御回路２７は、昇圧用スイッチング素子３３を１２．５μ秒毎に６．２５μ秒ずつのオンオフを繰り返させる。昇圧用スイッチング素子３５は昇圧用スイッチング素子３３と相補な動作を行うので、時比率が０．５である図２に示す動作では、昇圧用スイッチング素子３５のオンオフの動作の位相は昇圧用スイッチング素子３３の動作の位相と１８０度ずれている。 In the first embodiment, the on / off frequency f1 is 80 kHz in the range Rs1 in which the step-up switching elements 33 and 35 are PWM-controlled. In the first embodiment, the predetermined value Ds1 that is the minimum value of the duty ratio of the boosting switching element 35 is 0.5. In the operation shown in FIG. 2, the duty ratio of the boosting switching element 35 is the predetermined value Ds1. Since the period of the frequency of 80 kHz is 12.5 μsec, the control circuit 27 generates a pulse waveform with a time ratio of 0.5 and turns on the boosting switching element 35 for an on period of 6.25 μsec every 12.5 μsec. To. At the same time, the control circuit 27 causes the boosting switching element 33 to be repeatedly turned on and off every 6.25 μsec every 12.5 μsec. Since the step-up switching element 35 performs an operation complementary to the step-up switching element 33, in the operation shown in FIG. 2 where the time ratio is 0.5, the phase of the ON / OFF operation of the step-up switching element 35 is the step-up switching element. It is 180 degrees out of phase with the 33 operation.
　一方、降圧用スイッチング素子３０は上記したようにオンであり降圧用スイッチング素子３１はオフであるので、図３に示すように、時比率制御量Ｄｓが所定値Ｄｓ１である範囲Ｒｓ１にあるときには、降圧用スイッチング素子３０、３１のオンオフ周波数ｆｓはゼロである。 On the other hand, since the step-down switching element 30 is on and the step-down switching element 31 is off as described above, as shown in FIG. 3, when the time ratio control amount Ds is in the range Rs1 that is the predetermined value Ds1, The on / off frequency fs of the step-down switching elements 30 and 31 is zero.
　次に、時比率制御量Ｄｓが所定値Ｄｓ１より小さい場合のＤＣ／ＤＣコンバータ１１の動作について説明する。直流電源２８（太陽電池）への日射量が増加して入力電圧Ｖｉが高くなって出力電圧Ｖｏの目標値に近づくと、制御回路２７が出力電圧Ｖｏを目標値にするための時比率制御量Ｄｓが小さくなって所定値Ｄｓ１より小さい範囲Ｒｓ２に入ると、降圧用スイッチング素子３０、３１のオンオフ周波数ｆｓをゼロにしたまま、すなわち降圧用スイッチング素子３０をオンに維持してかつ降圧用スイッチング素子３１をオフに維持した状態で一定のオンオフ周波数ｆ１で昇圧用スイッチング素子３３、３５の時比率を変えるＰＷＭ制御を行なえなくなる。時比率制御量Ｄｓの範囲Ｒｓ２は所定値Ｄｓ１より小さくゼロ以上の範囲である。実施の形態１におけるＤＣ／ＤＣコンバータ１１では、制御回路は、時比率制御量Ｄｓが範囲Ｒｓ２に入っているときには、制御回路２７は、昇圧用スイッチング素子３５の時比率を所定値Ｄｓ１に維持して昇圧用スイッチング素子３３、３５をオンオフ周波数ｆ１で相補的にオンオフして相補な動作を行わせ、同時に、降圧用スイッチング素子３０、３１をオンオフ周波数ｆｓで相補的にオンオフして相補な動作を行わせるように動作する。 Next, the operation of the DC / DC converter 11 when the duty ratio control amount Ds is smaller than the predetermined value Ds1 will be described. When the amount of solar radiation to the DC power supply 28 (solar cell) increases and the input voltage Vi increases and approaches the target value of the output voltage Vo, the control ratio 27 for the control circuit 27 to set the output voltage Vo to the target value. When Ds decreases and enters a range Rs2 smaller than the predetermined value Ds1, the on / off frequency fs of the step-down switching elements 30, 31 is kept zero, that is, the step-down switching element 30 is kept on and the step-down switching element PWM control that changes the time ratio of the step-up switching elements 33 and 35 at a constant on / off frequency f1 with 31 kept off cannot be performed. A range Rs2 of the duty ratio control amount Ds is a range smaller than the predetermined value Ds1 and equal to or greater than zero. In the DC / DC converter 11 according to the first embodiment, when the duty ratio control amount Ds is within the range Rs2, the control circuit 27 maintains the duty ratio of the boosting switching element 35 at the predetermined value Ds1. Thus, the step-up switching elements 33 and 35 are complementarily turned on and off at the on / off frequency f1 to perform complementary operations, and at the same time, the step-down switching elements 30 and 31 are complementarily turned on and off at the on / off frequency fs to perform complementary operations. Operates to do.
　上記のように、制御回路２７が算出して得た時比率制御量Ｄｓが所定値Ｄｓ１より小さく範囲Ｒｓ２に入っているときには、降圧用スイッチング素子３０、３１のオンオフ周波数ｆｓの最低値は可聴周波数帯域Ｂｆの最高周波数ｆ０より高い。実施の形態１では最高周波数ｆ０は１８ｋＨｚである。ゆえに、時比率制御量Ｄｓが所定値Ｄｓ１である状態から所定値Ｄｓ１より僅かに小さい状態になると、制御回路２７は、オンオフ周波数ｆｓをゼロから最高周波数ｆ０より高い周波数に急増させる。このように、範囲Ｒｓ１、Ｒｓ２では降圧用スイッチング素子３０、３１のオンオフ周波数ｆｓと時比率制御量Ｄｓとの相関関係は不連続である。 As described above, when the duty ratio control amount Ds obtained by calculation by the control circuit 27 is smaller than the predetermined value Ds1 and falls within the range Rs2, the minimum value of the on / off frequency fs of the step-down switching elements 30 and 31 is the audible frequency. It is higher than the maximum frequency f0 of the band Bf. In the first embodiment, the maximum frequency f0 is 18 kHz. Therefore, when the duty ratio control amount Ds changes from the predetermined value Ds1 to a state slightly smaller than the predetermined value Ds1, the control circuit 27 rapidly increases the on / off frequency fs from zero to a frequency higher than the maximum frequency f0. Thus, in the ranges Rs1 and Rs2, the correlation between the on / off frequency fs of the step-down switching elements 30 and 31 and the duty ratio control amount Ds is discontinuous.
　オンオフ周波数ｆｓが可聴周波数帯域Ｂｆに入っていると、ＤＣ／ＤＣコンバータ１１から騒音が発生する可能性がある。同様に、ＰＷＭ制御におけるオンオフ周波数ｆ１が可聴周波数帯域Ｂｆに含まれると騒音の要因となるので、オンオフ周波数ｆ１も可聴周波数帯域Ｂｆから外れた値である８０ｋＨｚに設定している。なお、騒音が問題とならない場合は、オンオフ周波数ｆｓの最低の周波数をゼロにして、範囲Ｒｓ１、Ｒｓ２において降圧用スイッチング素子３０、３１のオンオフ周波数ｆｓと時比率制御量Ｄｓとの相関関係を連続にしてもよい。 If the on / off frequency fs is in the audible frequency band Bf, noise may be generated from the DC / DC converter 11. Similarly, if the on / off frequency f1 in the PWM control is included in the audible frequency band Bf, it becomes a noise factor. Therefore, the on / off frequency f1 is also set to 80 kHz, which is a value outside the audible frequency band Bf. When noise is not a problem, the lowest frequency of the on / off frequency fs is set to zero, and the correlation between the on / off frequency fs of the step-down switching elements 30 and 31 and the duty ratio control amount Ds is continuously obtained in the ranges Rs1 and Rs2. It may be.
　なお、制御回路２７はＰＷＭ制御が行えなくなったことを、目標値に対する出力電圧Ｖｏの差から判断することができる。すなわち、その差が測定や制御の誤差範囲以下であり出力電圧Ｖｏが目標値と一致していると判断した場合、制御回路２７はＰＷＭ制御が行われていると判断する。一方、その差が誤差範囲を超える場合、制御回路２７はＰＷＭ制御を行えないと判断する。この場合に、制御回路２７は、昇圧用スイッチング素子３３、３５の時比率を所定値Ｄｓ１に固定して昇圧用スイッチング素子３３、３５をオンオフ周波数ｆ１で相補的にオンオフして相補的な動作を継続させるとともに、降圧用スイッチング素子３０、３１をオンオフ周波数ｆｓでオンオフ動作させる。この動作における時比率制御量Ｄｓは、実施の形態１では比例積分量に基づく。したがって、実施の形態１では、時比率制御量Ｄｓが所定値Ｄｓ１より小さい場合には、時比率制御量Ｄｓは降圧用スイッチング素子３０、３１に対する比例積分量である。なお、時比率制御量Ｄｓは比例積分量に限定されるものではなく、例えば比例積分微分量であってもよく、この場合には制御が複雑になるものの、出力電圧Ｖｏの精度を高めることはできる。このように、ＤＣ／ＤＣコンバータ１１は、出力電圧Ｖｏが入力電圧Ｖｉに非常に近い場合でも正常に動作する。 The control circuit 27 can determine from the difference in the output voltage Vo with respect to the target value that the PWM control cannot be performed. That is, when it is determined that the difference is equal to or less than the measurement or control error range and the output voltage Vo matches the target value, the control circuit 27 determines that the PWM control is being performed. On the other hand, if the difference exceeds the error range, the control circuit 27 determines that PWM control cannot be performed. In this case, the control circuit 27 fixes the time ratio of the boosting switching elements 33 and 35 to the predetermined value Ds1 and complementarily turns on and off the boosting switching elements 33 and 35 at the on / off frequency f1. The step-down switching elements 30 and 31 are turned on and off at the on / off frequency fs. The duty ratio control amount Ds in this operation is based on the proportional integration amount in the first embodiment. Therefore, in the first embodiment, when the duty ratio control amount Ds is smaller than the predetermined value Ds1, the duty ratio control amount Ds is a proportional integral amount with respect to the step-down switching elements 30 and 31. Note that the duty ratio control amount Ds is not limited to the proportional integral amount, and may be, for example, a proportional integral differential amount. In this case, although the control is complicated, the accuracy of the output voltage Vo is increased. it can. Thus, the DC / DC converter 11 operates normally even when the output voltage Vo is very close to the input voltage Vi.
　次に、時比率制御量Ｄｓが所定値Ｄｓ１より小さい場合のＤＣ／ＤＣコンバータ１１の具体的な動作を以下に説明する。 Next, the specific operation of the DC / DC converter 11 when the duty ratio control amount Ds is smaller than the predetermined value Ds1 will be described below.
　時比率制御量Ｄｓが所定値Ｄｓ１より小さい範囲Ｒｓ２にあるときには、図３に示すように、制御回路２７は、昇圧用スイッチング素子３３、３５をオンオフ周波数ｆ１で相補的にオンオフさせている状態で、降圧用スイッチング素子３０、３１をオンオフ周波数ｆｓで相補的にオンオフさせる。時比率制御量Ｄｓが所定値Ｄｓ１から所定値Ｄｓ１より小さい所定値Ｄｓ２まで小さくなる過程では、図３に示すように、降圧用スイッチング素子３０、３１がオンオフ周波数ｆｓで相補的にオンオフ動作する。時比率制御量Ｄｓが所定値Ｄｓ２に至ると、図３に示すように、制御回路２７はオンオフ周波数ｆ２（２０ｋＨｚ）で降圧用スイッチング素子３０、３１を相補的にオンオフさせる。 When the duty ratio control amount Ds is in the range Rs2 smaller than the predetermined value Ds1, as shown in FIG. 3, the control circuit 27 is in a state where the boosting switching elements 33 and 35 are complementarily turned on and off at the on / off frequency f1. The step-down switching elements 30 and 31 are complementarily turned on and off at the on / off frequency fs. In the process where the duty ratio control amount Ds decreases from the predetermined value Ds1 to the predetermined value Ds2 smaller than the predetermined value Ds1, as shown in FIG. 3, the step-down switching elements 30 and 31 are complementarily turned on and off at the on / off frequency fs. When the time ratio control amount Ds reaches the predetermined value Ds2, as shown in FIG. 3, the control circuit 27 turns on and off the step-down switching elements 30 and 31 at the on / off frequency f2 (20 kHz) in a complementary manner.
　図４は、時比率制御量Ｄｓが所定値Ｄｓ２であるときのスイッチング素子３０、３１、３３、３５のタイミングチャートである。 FIG. 4 is a timing chart of the switching elements 30, 31, 33, and 35 when the duty ratio control amount Ds is the predetermined value Ds2.
　図４に示すように、昇圧用スイッチング素子３３、３５は、図２に示す動作と同様に、位相が１８０度ずれてオンオフ周波数ｆ１（８０ｋＨｚ）でかつ固定の時比率（実施の形態１では０．５）で相補的にオンオフ動作を繰り返す。 As shown in FIG. 4, the step-up switching elements 33 and 35, as in the operation shown in FIG. 2, are 180 degrees out of phase and have an on / off frequency f1 (80 kHz) and a fixed time ratio (0 in the first embodiment). 5) Complementarily repeats the on / off operation.
　一方、図４に示すように、制御回路２７は降圧用スイッチング素子３０を時刻ｔ２から時刻ｔ３までの期間と、時刻ｔ１０から時刻ｔ１１までの期間にオフにする。制御回路２７は、降圧用スイッチング素子３１を降圧用スイッチング素子３０と相補的に動作させるので、上記の期間にオンにする。 On the other hand, as shown in FIG. 4, the control circuit 27 turns off the step-down switching element 30 in a period from time t2 to time t3 and in a period from time t10 to time t11. Since the control circuit 27 operates the step-down switching element 31 in a complementary manner with the step-down switching element 30, it is turned on during the above period.
　図３に示すように、時比率制御量Ｄｓが所定値Ｄｓ２における降圧用スイッチング素子３０、３１のオンオフ周波数ｆ２は２０ｋＨｚであるので、オンオフ周波数ｆ２は昇圧用スイッチング素子３３、３５のオンオフ周波数ｆ１（８０ｋＨｚ）の１／４であり、その周期は４倍である。したがって、降圧用スイッチング素子３０は、制御回路２７により、昇圧用スイッチング素子３３の４倍の周期で繰り返しオフされ、降圧用スイッチング素子３０と相補に動作する降圧用スイッチング素子３１は、制御回路２７により、昇圧用スイッチング素子３５の４倍の周期で繰り返しオンされる。この際、降圧用スイッチング素子３１がオンされるオン期間は、昇圧用スイッチング素子３５のオン期間（６．２５μ秒）と同じ値に固定される。昇圧用スイッチング素子３５と相補な動作を行う昇圧用スイッチング素子３３がオフされるオフ期間も昇圧用スイッチング素子３５のオン期間（６．２５μ秒）と同じ期間である６．２５μ秒に固定される。 As shown in FIG. 3, since the on / off frequency f2 of the step-down switching elements 30 and 31 when the duty ratio control amount Ds is a predetermined value Ds2 is 20 kHz, the on / off frequency f2 is the on / off frequency f1 ( 80 kHz), and its period is four times. Therefore, the step-down switching element 30 is repeatedly turned off by the control circuit 27 at a period four times that of the step-up switching element 33, and the step-down switching element 31 operating in a complementary manner with the step-down switching element 30 is The switch is repeatedly turned on at a cycle four times that of the boosting switching element 35. At this time, the ON period during which the step-down switching element 31 is turned on is fixed to the same value as the ON period (6.25 μsec) of the step-up switching element 35. The off period during which the boosting switching element 33 that performs a complementary operation with the boosting switching element 35 is turned off is also fixed to 6.25 μs, which is the same period as the on period (6.25 μs) of the boosting switching element 35. .
　上記の動作により、降圧用スイッチング素子３０は、図４に示すように、昇圧用スイッチング素子３３、３５の４倍の周期毎にオンとなり、降圧用スイッチング素子３１は、その周期毎にオフとなる。すなわち、実施の形態１では、昇圧用スイッチング素子３３が４回オフになる毎に、降圧用スイッチング素子３０が１回オフとなる。昇圧用スイッチング素子３３と降圧用スイッチング素子３０のオフ期間は制御回路２７の誤差範囲内で実質的に等しい。同様に、昇圧用スイッチング素子３５が４回オン状態になる毎に降圧用スイッチング素子３１が１回オンとなり、昇圧用スイッチング素子３５と降圧用スイッチング素子３１のオン期間は誤差範囲内で実質的に等しい。 With the above operation, as shown in FIG. 4, the step-down switching element 30 is turned on every four times as high as the step-up switching elements 33 and 35, and the step-down switching element 31 is turned off every period. . That is, in the first embodiment, every time the step-up switching element 33 is turned off four times, the step-down switching element 30 is turned off once. The off periods of the step-up switching element 33 and the step-down switching element 30 are substantially equal within the error range of the control circuit 27. Similarly, every time the step-up switching element 35 is turned on four times, the step-down switching element 31 is turned on once, and the ON period of the step-up switching element 35 and the step-down switching element 31 is substantially within an error range. equal.
　さらに時比率制御量Ｄｓが所定値Ｄｓ２からさらに小さくなると、図３に示すように、降圧用スイッチング素子３１、３３のオンオフ周波数ｆｓは徐々に大きくなる。そして、時比率制御量Ｄｓが所定値Ｄｓ３に至ると、オンオフ周波数ｆｓはオンオフ周波数ｆ３（＝４０ｋＨｚ）となる。オンオフ周波数ｆ３は、ＰＷＭ制御される昇圧用スイッチング素子３３、３５のオンオフ周波数ｆ１（＝８０ｋＨｚ）の半分であるので、制御回路２７が降圧用スイッチング素子３１をオンする周期は昇圧用スイッチング素子３５をオンする周期の２倍である。 Further, when the duty ratio control amount Ds is further reduced from the predetermined value Ds2, as shown in FIG. 3, the on / off frequencies fs of the step-down switching elements 31 and 33 gradually increase. When the duty ratio control amount Ds reaches the predetermined value Ds3, the on / off frequency fs becomes the on / off frequency f3 (= 40 kHz). Since the on / off frequency f3 is half of the on / off frequency f1 (= 80 kHz) of the step-up switching elements 33 and 35 that are PWM-controlled, the period when the control circuit 27 turns on the step-down switching element 31 causes the step-up switching element 35 to turn on. It is twice the cycle to turn on.
　図５は時比率制御量Ｄｓが所定値Ｄｓ３であるときのスイッチング素子３０、３１、３３、３５のタイミングチャートである。 FIG. 5 is a timing chart of the switching elements 30, 31, 33, and 35 when the duty ratio control amount Ds is the predetermined value Ds3.
　図５に示す動作では、上記したとおり、降圧用スイッチング素子３１がオンされる周期が昇圧用スイッチング素子３５のオンオフ周波数ｆ１の周期の２倍になる。また、図５に示す動作においても、図４に示すように、降圧用スイッチング素子３１のオン期間は６．２５μ秒であり、昇圧用スイッチング素子３５のオン期間と誤差範囲内で実質的に等しいので、昇圧用スイッチング素子３５が２回オンになる毎に降圧用スイッチング素子３１が１回オンになる。図５に示すように、降圧用スイッチング素子３０は、降圧用スイッチング素子３１と相補な動作を行う。また、昇圧用スイッチング素子３３は、図５に示すように、昇圧用スイッチング素子３５と相補な動作を行う。 In the operation shown in FIG. 5, as described above, the cycle in which the step-down switching element 31 is turned on is twice the cycle of the on-off frequency f1 of the step-up switching element 35. Also in the operation shown in FIG. 5, as shown in FIG. 4, the on-period of the step-down switching element 31 is 6.25 μsec, and is substantially equal to the on-period of the step-up switching element 35 within an error range. Therefore, every time the step-up switching element 35 is turned on twice, the step-down switching element 31 is turned on once. As shown in FIG. 5, the step-down switching element 30 performs an operation complementary to the step-down switching element 31. Further, as shown in FIG. 5, the boosting switching element 33 performs an operation complementary to the boosting switching element 35.
　時比率制御量Ｄｓが所定値Ｄｓ３よりさらに小さくなると、図３に示すように、降圧用スイッチング素子３０、３１のオンオフ周波数ｆｓは徐々に大きくなり、降圧用スイッチング素子３１がオンになりかつ降圧用スイッチング素子３０がオフになる周期が短くなる。降圧用スイッチング素子３０のオフ期間は６．２５μ秒に固定されているので、降圧用スイッチング素子３０の１周期におけるオン期間が時比率制御量Ｄｓの低下とともに短くなる。降圧用スイッチング素子３１は降圧用スイッチング素子３０と相補な動作を行うので、降圧用スイッチング素子３１の１周期におけるオフ期間が時比率制御量Ｄｓの低下とともに短くなる。 When the time ratio control amount Ds becomes further smaller than the predetermined value Ds3, as shown in FIG. 3, the on / off frequency fs of the step-down switching elements 30, 31 gradually increases, the step-down switching element 31 is turned on, and the step-down switching element 31 is turned on. The period when the switching element 30 is turned off is shortened. Since the off period of the step-down switching element 30 is fixed at 6.25 μsec, the on period in one cycle of the step-down switching element 30 becomes shorter as the time ratio control amount Ds decreases. Since the step-down switching element 31 performs a complementary operation with the step-down switching element 30, the OFF period of one step of the step-down switching element 31 is shortened with a decrease in the time ratio control amount Ds.
　時比率制御量Ｄｓがさらに小さくなって電圧検出や演算の誤差範囲内で実質的にゼロである所定値Ｄｓ４になる、すなわち、入力電圧Ｖｉと出力電圧Ｖｏが誤差範囲内で実質的に等しくなると、図３に示すように、降圧用スイッチング素子３０、３１のオンオフ周波数ｆｓは、昇圧用スイッチング素子３３、３５のオンオフ周波数ｆ１と誤差範囲内で実質的に等しくなる。図６は、時比率制御量Ｄｓが所定値Ｄｓ４（＝０）であるときのスイッチング素子３０、３１、３３、３５のタイミングチャートである。 When the duty ratio control amount Ds is further reduced to a predetermined value Ds4 that is substantially zero within an error range of voltage detection or calculation, that is, when the input voltage Vi and the output voltage Vo become substantially equal within the error range. As shown in FIG. 3, the on / off frequency fs of the step-down switching elements 30 and 31 is substantially equal to the on / off frequency f1 of the step-up switching elements 33 and 35 within an error range. FIG. 6 is a timing chart of the switching elements 30, 31, 33, and 35 when the duty ratio control amount Ds is a predetermined value Ds4 (= 0).
　図６に示すように、時比率制御量Ｄｓが所定値Ｄｓ４（＝０）である場合、降圧用スイッチング素子３０のタイミングチャートは昇圧用スイッチング素子３３のタイミングチャートと同じになる。同様に、降圧用スイッチング素子３１のタイミングチャートは昇圧用スイッチング素子３５のタイミングチャートと同じとなる。この状態は、ＤＣ／ＤＣコンバータ１１が昇圧動作と降圧動作を同条件で同時に行っていることに相当し、上記したように、入力電圧Ｖｉがそのまま出力電圧Ｖｏになるように制御されている。 6, when the duty ratio control amount Ds is a predetermined value Ds4 (= 0), the timing chart of the step-down switching element 30 is the same as the timing chart of the step-up switching element 33. Similarly, the timing chart of the step-down switching element 31 is the same as the timing chart of the step-up switching element 35. This state corresponds to the DC / DC converter 11 performing the step-up operation and the step-down operation at the same time under the same conditions, and as described above, the input voltage Vi is controlled as it is to the output voltage Vo.
　このように、時比率制御量Ｄｓが所定値Ｄｓ１から所定値Ｄｓ２までの間では、図２から図６に示すように、時比率制御量Ｄｓが小さくなるほど降圧用スイッチング素子３１がオンとなる周期が短くなり、オンの回数が増える。従って、時比率制御量Ｄｓが所定値Ｄｓ１から所定値Ｄｓ２までの間は降圧用スイッチング素子３１のパルスが増えるように制御される。これは、制御回路２７による比例積分制御により実現できる。なお、この制御は、上記したように比例積分微分制御で実現してもよい。 As described above, when the time ratio control amount Ds is between the predetermined value Ds1 and the predetermined value Ds2, as shown in FIGS. 2 to 6, the period when the step-down switching element 31 is turned on as the time ratio control amount Ds decreases. Becomes shorter and the number of on-times increases. Accordingly, the pulse of the step-down switching element 31 is controlled to increase while the duty ratio control amount Ds is between the predetermined value Ds1 and the predetermined value Ds2. This can be realized by proportional-integral control by the control circuit 27. Note that this control may be realized by proportional-integral-derivative control as described above.
　太陽電池である直流電源２８への日射量がさらに増えると、入力電圧Ｖｉが出力電圧Ｖｏより高くなる。この場合は、時比率制御量Ｄｓが負になり、図３に示す相関関係にしたがって、昇圧用スイッチング素子３３、３５のオンオフ周波数ｆｂが徐々に低くなり、同時に、降圧用スイッチング素子３０、３１のオンオフ周波数ｆｓは一定の周波数ｆ１（＝８０ｋＨｚ）となる。このように、時比率制御量Ｄｓが実質的にゼロである所定値Ｄｓ４に至ると、制御回路２７は昇圧用スイッチング素子３３、３５の動作と降圧用スイッチング素子３０、３１の動作とを入れ替える。 When the amount of solar radiation to the DC power supply 28 that is a solar cell further increases, the input voltage Vi becomes higher than the output voltage Vo. In this case, the duty ratio control amount Ds becomes negative, and the on / off frequency fb of the step-up switching elements 33 and 35 gradually decreases according to the correlation shown in FIG. The on / off frequency fs is a constant frequency f1 (= 80 kHz). As described above, when the time ratio control amount Ds reaches the predetermined value Ds4 which is substantially zero, the control circuit 27 switches the operation of the step-up switching elements 33 and 35 and the operation of the step-down switching elements 30 and 31.
　時比率制御量Ｄｓが所定値Ｄｓ４より小さい範囲Ｒｓ３に入って所定値Ｄｓ５まで小さくなると、図３に示す相関関係に基づいて、オンオフ周波数ｆｂが周波数ｆ３（＝４０ｋＨｚ）となるように、昇圧用スイッチング素子３５のオン状態が制御される。このとき、降圧用スイッチング素子３０、３１はオンオフ周波数ｆ１（＝８０ｋＨｚ）でオンオフ制御される。したがって、昇圧用スイッチング素子３５は降圧用スイッチング素子３１の２倍の周期でオンになるように制御される。 When the duty ratio control amount Ds enters the range Rs3 smaller than the predetermined value Ds4 and decreases to the predetermined value Ds5, based on the correlation shown in FIG. 3, the on / off frequency fb is set to the frequency f3 (= 40 kHz). The on state of the switching element 35 is controlled. At this time, the step-down switching elements 30 and 31 are on / off controlled at an on / off frequency f1 (= 80 kHz). Therefore, the step-up switching element 35 is controlled to be turned on at a cycle twice that of the step-down switching element 31.
　図７は、時比率制御量Ｄｓが所定値Ｄｓ５であるときのスイッチング素子３０、３１、３３、３５のタイミングチャートである。昇圧用スイッチング素子３５は、オン期間（６．２５μ秒）固定された状態で降圧用スイッチング素子３１の２倍の周期（２５μ秒）でオン状態になるように制御される。降圧用スイッチング素子３０は降圧用スイッチング素子３１と相補な動作を行い、昇圧用スイッチング素子３３は昇圧用スイッチング素子３５と相補な動作を行う。 FIG. 7 is a timing chart of the switching elements 30, 31, 33, and 35 when the duty ratio control amount Ds is the predetermined value Ds5. The step-up switching element 35 is controlled so as to be turned on in a period (25 μsec) twice as long as that of the step-down switching element 31 in a state where the on-period (6.25 μsec) is fixed. The step-down switching element 30 performs an operation complementary to the step-down switching element 31, and the step-up switching element 33 performs an operation complementary to the step-up switching element 35.
　時比率制御量Ｄｓが所定値Ｄｓ５からさらに小さくなり所定値Ｄｓ６に至ると、図３に示すように、オンオフ周波数ｆ２（＝２０ｋＨｚ）で昇圧用スイッチング素子３５が動作する。図８は、時比率制御量Ｄｓが所定値Ｄｓ６であるときのスイッチング素子３０、３１、３３、３５のタイミングチャートである。昇圧用スイッチング素子３５は降圧用スイッチング素子３１の４倍の周期でオン状態になるように制御される。降圧用スイッチング素子３０は降圧用スイッチング素子３１と相補な動作を行い、昇圧用スイッチング素子３３は昇圧用スイッチング素子３５と相補な動作を行う。 When the duty ratio control amount Ds further decreases from the predetermined value Ds5 and reaches the predetermined value Ds6, the step-up switching element 35 operates at the on / off frequency f2 (= 20 kHz) as shown in FIG. FIG. 8 is a timing chart of the switching elements 30, 31, 33, and 35 when the duty ratio control amount Ds is the predetermined value Ds6. The step-up switching element 35 is controlled to be turned on at a cycle four times that of the step-down switching element 31. The step-down switching element 30 performs an operation complementary to the step-down switching element 31, and the step-up switching element 33 performs an operation complementary to the step-up switching element 35.
　時比率制御量Ｄｓが所定値Ｄｓ６からさらに小さくなり所定値Ｄｓ７に至ると、図３に示す相関関係にしたがって、制御回路２７は昇圧用スイッチング素子３３、３５のオンオフ動作を停止し、降圧用スイッチング素子３０、３１のみをオンオフ動作させる。これにより、ＤＣ／ＤＣコンバータ１１は降圧用スイッチング素子３０、３１のみで降圧動作を行う。時比率制御量Ｄｓが所定値Ｄｓ４より小さく所定値Ｄｓ７より大きい範囲Ｒｓ３から所定値Ｄｓ７以下の範囲Ｒｓ４に入ると、制御回路２７は降圧用スイッチング素子３０、３１に対して変動時比率でのＰＷＭ制御を行なうことにより、出力電圧Ｖｏが所望の電圧値になるように制御する。 When the duty ratio control amount Ds further decreases from the predetermined value Ds6 to the predetermined value Ds7, the control circuit 27 stops the on / off operation of the step-up switching elements 33 and 35 according to the correlation shown in FIG. Only the elements 30 and 31 are turned on / off. As a result, the DC / DC converter 11 performs a step-down operation using only the step-down switching elements 30 and 31. When the time ratio control amount Ds enters the range Rs4 that is smaller than the predetermined value Ds4 and larger than the predetermined value Ds7 to the range Rs4 that is equal to or smaller than the predetermined value Ds7, the control circuit 27 performs PWM at the variation time ratio with respect to the step-down switching elements 30 and 31. By performing the control, the output voltage Vo is controlled to a desired voltage value.
　図９は、時比率制御量Ｄｓが所定値Ｄｓ７以下である範囲Ｒｓ４に入っているときのスイッチング素子３０、３１、３３、３５のタイミングチャートである。図９に示すように、制御回路２７は昇圧用スイッチング素子３３をオンに維持し、昇圧用スイッチング素子３５をオフに維持する。さらに、制御回路２７は降圧用スイッチング素子３０、３１に相補にオンオフ動作を繰り返させる。 FIG. 9 is a timing chart of the switching elements 30, 31, 33, and 35 when the duty ratio control amount Ds is in the range Rs4 that is equal to or less than the predetermined value Ds7. As shown in FIG. 9, the control circuit 27 keeps the boost switching element 33 on and keeps the boost switching element 35 off. Further, the control circuit 27 causes the step-down switching elements 30 and 31 to repeat the ON / OFF operation complementarily.
　このように、時比率制御量Ｄｓが所定値Ｄｓ４から所定値Ｄｓ７までの間、昇圧用スイッチング素子３５は、図６から図９に示すように、時比率制御量Ｄｓが小さくなるほどオフとなる周期が長くなり、オフの回数が減る。したがって、時比率制御量Ｄｓが所定値Ｄｓ４から所定値Ｄｓ７までの間は、昇圧用スイッチング素子３３のパルスが減るように制御される。この動作は制御回路２７による比例積分制御により実現できる。 As described above, during the time ratio control amount Ds from the predetermined value Ds4 to the predetermined value Ds7, the boosting switching element 35 is turned off as the time ratio control amount Ds decreases, as shown in FIGS. Becomes longer and the number of times of off is reduced. Therefore, while the duty ratio control amount Ds is between the predetermined value Ds4 and the predetermined value Ds7, the pulse of the boosting switching element 33 is controlled to decrease. This operation can be realized by proportional-integral control by the control circuit 27.
　なお、時比率制御量Ｄｓが小さい場合から大きくなる際、すなわち、降圧動作から昇圧動作を行う場合は、ＤＣ／ＤＣコンバータ１１は上記した説明と逆の動作を行う。この場合、所定値Ｄｓ１が所定値Ｄｓ７に代わり、所定値Ｄｓ７が所定値Ｄｓ１に代わる。 When the duty ratio control amount Ds is increased from a small value, that is, when the step-up operation is performed from the step-down operation, the DC / DC converter 11 performs an operation reverse to the above description. In this case, the predetermined value Ds1 is replaced with the predetermined value Ds7, and the predetermined value Ds7 is replaced with the predetermined value Ds1.
　上記した昇圧動作から降圧動作に切り替わる際の制御回路２７による制御を以下にまとめる。制御回路２７は、時比率制御量Ｄｓが第１所定値Ｄｓ１より大きい値から第１所定値Ｄｓ１に至ると、パルス幅変調制御を行っていない降圧用スイッチング素子３０、３１に対し、予め決定された時比率制御量Ｄｓとオンオフ周波数ｆｓとの相関関係に基づいて求められる周期毎に、降圧用スイッチング素子３０、３１の一方の降圧用スイッチング素子３１のオン期間を固定した状態でオン制御を行なうとともに、降圧用スイッチング素子３０、３１の他方の降圧用スイッチング素子３０のオフ期間を固定した状態でオフ制御を行なう。そして、制御回路２７は、時比率制御量Ｄｓが第２所定値Ｄｓ４に至ると、昇圧用スイッチング素子３３、３５の動作と降圧用スイッチング素子３０、３１の動作とを入れ替える。そして、時比率制御量Ｄｓが第３所定値Ｄｓ７に至ると、降圧用スイッチング素子３０、３１により降圧動作を行なう。 The control by the control circuit 27 when switching from the step-up operation described above to the step-down operation is summarized below. When the duty ratio control amount Ds reaches from the value greater than the first predetermined value Ds1 to the first predetermined value Ds1, the control circuit 27 determines in advance for the step-down switching elements 30 and 31 that are not performing pulse width modulation control. On-control is performed in a state in which the ON period of one step-down switching element 30, 31 is fixed for each period obtained based on the correlation between the duty ratio control amount Ds and the ON / OFF frequency fs. At the same time, the OFF control is performed in a state where the OFF period of the other step-down switching element 30, 31 is fixed. Then, when the duty ratio control amount Ds reaches the second predetermined value Ds4, the control circuit 27 switches the operation of the step-up switching elements 33 and 35 and the operation of the step-down switching elements 30 and 31. When the duty ratio control amount Ds reaches the third predetermined value Ds7, the step-down switching elements 30 and 31 perform step-down operation.
　また、降圧動作から昇圧動作に切り替わる際の制御回路２７による制御を以下にまとめる。制御回路２７は、時比率制御量Ｄｓが第１所定値Ｄｓ７より小さい値から第１所定値Ｄｓ７に至ると、パルス幅変調制御を行っていない昇圧用スイッチング素子３３、３５に対し、予め決定された時比率制御量Ｄｓとオンオフ周波数ｆｂとの相関関係に基づいて求められる周期毎に、昇圧用スイッチング素子３３、３５の一方の昇圧用スイッチング素子３３のオン期間を固定した状態でオン制御を行なうとともに、昇圧用スイッチング素子３３、３５の他方の昇圧用スイッチング素子３５のオフ期間を固定した状態でオフ制御を行なう。そして、制御回路２７は、時比率制御量Ｄｓが第２所定値Ｄｓ４に至ると、昇圧用スイッチング素子３３、３５の動作と降圧用スイッチング素子３０、３１の動作とを入れ替える。そして、時比率制御量Ｄｓが第３所定値Ｄｓ１に至ると、昇圧用スイッチング素子３３、３５により昇圧動作を行なう。 Also, the control by the control circuit 27 when switching from the step-down operation to the step-up operation is summarized below. When the duty ratio control amount Ds reaches a first predetermined value Ds7 from a value smaller than the first predetermined value Ds7, the control circuit 27 determines in advance the switching elements 33 and 35 for boosting that are not performing pulse width modulation control. On the other hand, on-control is performed in a state in which the ON period of one of the boosting switching elements 33 and 35 is fixed for each period obtained based on the correlation between the duty ratio control amount Ds and the ON / OFF frequency fb. At the same time, the OFF control is performed in a state where the OFF period of the other boosting switching element 35 of the boosting switching elements 33 and 35 is fixed. Then, when the duty ratio control amount Ds reaches the second predetermined value Ds4, the control circuit 27 switches the operation of the step-up switching elements 33 and 35 and the operation of the step-down switching elements 30 and 31. When the duty ratio control amount Ds reaches the third predetermined value Ds1, the boosting switching elements 33 and 35 perform the boosting operation.
　このように動作することで、ＤＣ／ＤＣコンバータ１１は昇降圧動作をスムースに切り替えることができる。さらに、昇降圧動作を切り替える近傍の電圧差、すなわち時比率制御量Ｄｓが０に近い場合のみ、４つのスイッチング素子のオンオフ動作を行い、昇圧動作のみまたは降圧動作のみを行っている場合は２つのスイッチング素子のみオンオフ動作を行う。よって、ＤＣ／ＤＣコンバータ１１の効率がよくなる。 By operating in this manner, the DC / DC converter 11 can smoothly switch the step-up / step-down operation. Further, only when the voltage difference in the vicinity of switching the step-up / step-down operation, that is, when the duty ratio control amount Ds is close to 0, the four switching elements are turned on / off, and when only the step-up operation or the step-down operation is performed, two Only the switching element is turned on / off. Therefore, the efficiency of the DC / DC converter 11 is improved.
　図１９に示す従来のＤＣ／ＤＣコンバータ１０１は、図２０に示すように、ブーストモードとバックモードとを切り替える際にバックブーストモード動作を行う。この際、図２０に示すように、２つの電圧ＶＺ１、ＶＺ２が必要となる。これらは三角波である２つの電圧ＶＸ、ＶＹに基づいて生成されているので、電圧ＶＸ、ＶＹを生成するための回路が必要となり、回路構成が複雑になる。 A conventional DC / DC converter 101 shown in FIG. 19 performs a buck-boost mode operation when switching between a boost mode and a buck mode, as shown in FIG. At this time, as shown in FIG. 20, two voltages V Z1 and V Z2 are required. Since these are generated based on two voltages V X and V Y which are triangular waves, a circuit for generating the voltages V X and V Y is required, and the circuit configuration is complicated.
　実施の形態１におけるＤＣ／ＤＣコンバータ１１では、昇降圧動作の切り換え時には、時比率制御量Ｄｓとオンオフ周波数（ｆｂ、ｆｓ）との相関関係に基づいて求められる周期毎にスイッチング素子３０、３１、３３、３５のオン制御を行なうので、２つの三角波を用いる必要がない。したがって、ＤＣ／ＤＣコンバータ１１を簡単な回路構成とすることができる。 In the DC / DC converter 11 according to the first embodiment, when the step-up / step-down operation is switched, the switching elements 30, 31, Since the on- controls 33 and 35 are performed, it is not necessary to use two triangular waves. Therefore, the DC / DC converter 11 can have a simple circuit configuration.
　また、実施の形態１では降圧用スイッチング素子３０、３１のオンオフ周波数ｆｓ、昇圧用スイッチング素子３３、３５のオンオフ周波数ｆｂの最小値をそれぞれゼロとしているが、ブートストラップ回路構成の場合、オンオフ周波数ｆｓ、ｆｂはゼロ以上であってもよい。 In the first embodiment, the on / off frequency fs of the step-down switching elements 30 and 31 and the minimum value of the on / off frequency fb of the step-up switching elements 33 and 35 are each zero, but in the case of the bootstrap circuit configuration, the on / off frequency fs is set. , Fb may be zero or more.
　以上の構成、動作により、制御回路２７は、昇圧のみの場合に昇圧用スイッチング素子３３、３５に対してＰＷＭ制御を行い、降圧のみの場合に降圧用スイッチング素子３０、３１に対してＰＷＭ制御を行なう。そして、制御回路２７は、上記相関関係に基づいて合計４つのスイッチング素子３０、３１、３３、３５を制御することにより昇降圧切替が可能となる。この切替時に、オンオフ周期を可変するだけの制御であるので、図１９と図２０に示す従来のＤＣ／ＤＣコンバータの２つの三角波を得るための回路が不要となり、簡単な構成で昇降圧が可能なＤＣ／ＤＣコンバータ１１が得られる。 With the above configuration and operation, the control circuit 27 performs PWM control on the boosting switching elements 33 and 35 when boosting only, and performs PWM control on the buck switching elements 30 and 31 when only boosting. Do. Then, the control circuit 27 can perform step-up / step-down switching by controlling a total of four switching elements 30, 31, 33, and 35 based on the correlation. Since the control only changes the on / off cycle at the time of switching, the circuit for obtaining the two triangular waves of the conventional DC / DC converter shown in FIGS. 19 and 20 is not required, and the voltage can be increased or decreased with a simple configuration. A DC / DC converter 11 can be obtained.
　なお、実施の形態１では、制御回路２７は、昇圧用スイッチング素子３３、３５を相補な動作を行わせる際と、降圧用スイッチング素子３０、３１を相補な動作を行わせる際に、それぞれのオンオフ状態が制御回路２７やスイッチング素子の応答における誤差範囲内で同時に切り替える。しかし、制御回路２７は２個の昇圧用スイッチング素子３３、３５が同時にオフになる同時オフ期間を介在させてオンオフを切り替え、２個の降圧用スイッチング素子３０、３１が同時にオフになる同時オフ期間を介在させてオンオフを切り替えてもよい。これにより、同時オフ期間が実質的にない場合における短絡の可能性を以下の理由で低減することができる。 In the first embodiment, the control circuit 27 turns on / off each time when the step-up switching elements 33 and 35 perform complementary operations and when the step-down switching elements 30 and 31 perform complementary operations. The states are switched simultaneously within an error range in the response of the control circuit 27 and the switching element. However, the control circuit 27 switches on and off through a simultaneous off period in which the two step-up switching elements 33 and 35 are simultaneously turned off, and a simultaneous off period in which the two step-down switching elements 30 and 31 are simultaneously turned off. May be switched on and off. Thereby, the possibility of a short circuit when there is substantially no simultaneous OFF period can be reduced for the following reasons.
　昇圧用スイッチング素子３３、３５が実質的に同時に切り替わるようにした場合、誤差によっては一瞬、両者が同時にオン状態になる可能性がある。その結果、出力端子１９とグランド端子１７が短絡して出力電圧Ｖｏが不安定になる可能性がある。また、短絡の発生により、平滑コンデンサ３７の容量によっては、平滑コンデンサ３７から大電流が流れ、昇圧用スイッチング素子３３、３５が劣化する可能性がある。 When the step-up switching elements 33 and 35 are switched at substantially the same time, both of them may be turned on simultaneously for a moment depending on an error. As a result, the output terminal 19 and the ground terminal 17 may be short-circuited and the output voltage Vo may become unstable. Also, due to the occurrence of a short circuit, depending on the capacity of the smoothing capacitor 37, a large current may flow from the smoothing capacitor 37, and the boosting switching elements 33 and 35 may deteriorate.
　降圧用スイッチング素子３０、３１が実質的に同時に切り替わるようにした場合も、誤差によっては一瞬、両者が同時にオン状態になる可能性がある。その結果、入力電圧Ｖｉが不安定になり、特に昇降圧制御中は、誤動作の要因となり得る。さらに、直流電源２８の正極と負極が短絡する状態となるので、直流電源２８の寿命に影響する可能性もある。 Even when the step-down switching elements 30 and 31 are switched substantially simultaneously, there is a possibility that both of them may be turned on simultaneously for a moment depending on an error. As a result, the input voltage Vi becomes unstable, and may cause a malfunction particularly during the buck-boost control. Furthermore, since the positive electrode and the negative electrode of the DC power supply 28 are short-circuited, the life of the DC power supply 28 may be affected.
　但し、同時オフ期間を介在させて２つのスイッチング素子を相補的にオンオフさせると、同時オフ期間が出力電圧Ｖｏの安定性に影響するので、同時オフ期間は誤差範囲を超えかつオン期間に比べてできるだけ短く設定することが望ましい。また、制御回路２７の制御速度や各スイッチング素子の応答速度によっては、同時オフ期間を介在させずにスイッチング素子のオンオフ状態を同時に切り替えてもよい。 However, if the two switching elements are complementarily turned on / off through the simultaneous off period, the simultaneous off period affects the stability of the output voltage Vo, so the simultaneous off period exceeds the error range and is compared to the on period. It is desirable to set as short as possible. Further, depending on the control speed of the control circuit 27 and the response speed of each switching element, the ON / OFF states of the switching elements may be switched simultaneously without interposing the simultaneous OFF period.
　このように、使用するデバイスやその性能、必要とされる出力電圧Ｖｏの安定性などによって、適宜、同時オフ期間の介在の要否を決定すればよい。 As described above, the necessity of interposing the simultaneous OFF period may be determined as appropriate depending on the device to be used, its performance, and the stability of the required output voltage Vo.
　また、実施の形態１では、時比率制御量Ｄｓが実質的に、すなわち、誤差範囲内で同じ周期に至る所定値Ｄｓ４となれば、昇圧用スイッチング素子３３、３５の動作と降圧用スイッチング素子３０、３１の動作とを入れ替えているが、これは、このような動作に限定されるものではない。その具体例を以下に説明する。 Further, in the first embodiment, when the duty ratio control amount Ds is substantially, that is, when the predetermined value Ds4 reaches the same period within the error range, the operation of the step-up switching elements 33 and 35 and the step-down switching element 30 are performed. However, this is not limited to such an operation. Specific examples thereof will be described below.
　この例では、制御回路２７は時比率制御量Ｄｓが小さくなって所定値Ｄｓ３に至った時点で、制御回路２７が昇圧用スイッチング素子３３、３５の動作と降圧用スイッチング素子３０、３１の動作とを入れ替える。これにより、各スイッチング素子の動作は図５のタイミングチャートに示す動作から図７のタイミングチャートに示す動作になる。図７のタイミングチャートは時比率制御量Ｄｓが所定値Ｄｓ５に至った際の動作であるので、時比率制御量Ｄｓが所定値Ｄｓ３から所定値Ｄｓ５に至るまでは、出力電圧Ｖｏが所望の値からずれる。しかし、ＤＣ／ＤＣコンバータ１１の用途によっては、上記のずれる量が許容範囲内の場合もある。この場合には、昇圧用スイッチング素子３３、３５の動作と降圧用スイッチング素子３０、３１の動作とを入れ替えるタイミングは、厳密に時比率制御量Ｄｓが所定値Ｄｓ４に至った時点である必要はない。 In this example, the control circuit 27 performs the operation of the step-up switching elements 33 and 35 and the operation of the step-down switching elements 30 and 31 when the duty ratio control amount Ds decreases and reaches a predetermined value Ds3. Replace. Thereby, the operation of each switching element is changed from the operation shown in the timing chart of FIG. 5 to the operation shown in the timing chart of FIG. Since the timing chart of FIG. 7 is an operation when the duty ratio control amount Ds reaches the predetermined value Ds5, the output voltage Vo is a desired value until the duty ratio control amount Ds reaches the predetermined value Ds5 from the predetermined value Ds3. Deviate. However, depending on the application of the DC / DC converter 11, the above deviation may be within an allowable range. In this case, the timing at which the operation of the step-up switching elements 33 and 35 and the operation of the step-down switching elements 30 and 31 are exchanged does not have to be strictly the time when the time ratio control amount Ds reaches the predetermined value Ds4. .
　出力電圧Ｖｏのずれる量が許容範囲に入れば、厳密に時比率制御量Ｄｓが所定値Ｄｓ４でなくても、実質的に同じ周期でスイッチング素子３０、３１、３３、３５がオンオフされているとみなすことができる。ここで、「実質的に」とは、上記した電圧測定や演算の誤差範囲に加え、出力電圧Ｖｏのずれる量における許容範囲も含むものと定義する。従って、時比率制御量Ｄｓが所定値Ｄｓ４に向かって小さくなる過程で、出力電圧Ｖｏのずれる量が許容範囲に入れば、実質的にスイッチング素子３０、３１、３３、３５が同じ周期でオンオフ制御される状態であると制御回路２７がみなし、昇圧用スイッチング素子３３、３５の動作と降圧用スイッチング素子３０、３１の動作とを入れ替える。このような構成であっても、図１９と図２０に示す従来のＤＣ／ＤＣコンバータの２つの三角波を得るための回路が不要となり、簡単な構成で昇降圧が可能なＤＣ／ＤＣコンバータ１１が得られる。 If the amount of deviation of the output voltage Vo falls within the allowable range, the switching elements 30, 31, 33, and 35 are turned on and off at substantially the same cycle even if the duty ratio control amount Ds is not exactly the predetermined value Ds4. Can be considered. Here, “substantially” is defined to include an allowable range in the amount of deviation of the output voltage Vo in addition to the above error range of voltage measurement and calculation. Accordingly, in the process in which the duty ratio control amount Ds decreases toward the predetermined value Ds4, if the amount of deviation of the output voltage Vo falls within the allowable range, the switching elements 30, 31, 33, and 35 are substantially controlled in the same cycle. The control circuit 27 considers that this is the state, and switches the operation of the step-up switching elements 33 and 35 and the operation of the step-down switching elements 30 and 31. Even in such a configuration, the circuit for obtaining the two triangular waves of the conventional DC / DC converter shown in FIGS. 19 and 20 is not required, and the DC / DC converter 11 capable of step-up / step-down with a simple configuration is provided. can get.
　上述のように、制御回路２７は、出力電圧Ｖｏが入力電圧Ｖｉ以上である場合に以下のように動作する。すなわち、制御回路２７は、降圧用スイッチング素子３０をオンにして降圧用スイッチング素子３１をオフにしかつ昇圧用スイッチング素子３３、３５を所定のオンオフ周波数ｆ１でオンオフする状態での昇圧用スイッチング素子３５の時比率を時比率制御量Ｄｓとして出力電圧Ｖｏに基づいて得るように動作する。制御回路は、時比率制御量Ｄｓが所定値Ｄｓ１以上であるときには、降圧用スイッチング素子３０をオンにして降圧用スイッチング素子３１をオフにした状態で時比率制御量Ｄｓの時比率で昇圧用スイッチング素子３３、３５を所定のオンオフ周波数ｆ１でオンオフするように動作する。制御回路２７は、時比率制御量Ｄｓが所定値Ｄｓ１より小さいときには、所定値Ｄｓ１の時比率で昇圧用スイッチング素子３３、３５を所定のオンオフ周波数ｆ１でオンオフし、時比率制御量Ｄｓに基づいて決定されたオンオフ周波数ｆｓで降圧用スイッチング素子３０、３１をオンオフするように動作する。 As described above, the control circuit 27 operates as follows when the output voltage Vo is equal to or higher than the input voltage Vi. That is, the control circuit 27 turns on the step-down switching element 30, turns off the step-down switching element 31, and turns on the step-up switching elements 33 and 35 at a predetermined on / off frequency f1. It operates so as to obtain the time ratio as the time ratio control amount Ds based on the output voltage Vo. When the time ratio control amount Ds is equal to or greater than the predetermined value Ds1, the control circuit performs step-up switching at the time ratio of the time ratio control amount Ds with the step-down switching element 30 turned on and the step-down switching element 31 turned off. The elements 33 and 35 operate so as to be turned on / off at a predetermined on / off frequency f1. When the time ratio control amount Ds is smaller than the predetermined value Ds1, the control circuit 27 turns on and off the boosting switching elements 33 and 35 at the predetermined on / off frequency f1 at the time ratio of the predetermined value Ds1, and based on the time ratio control amount Ds. The step-down switching elements 30 and 31 are operated to be turned on and off at the determined on / off frequency fs.
　制御回路２７は、出力電圧Ｖｏが入力電圧Ｖｉ以上である場合に、時比率制御量Ｄｓが所定値Ｄｓ１より小さいときには、降圧用スイッチング素子３１のオン期間を固定した状態でオンオフ周波数ｆｓで降圧用スイッチング素子３０、３１をオンオフするように動作してもよい。 When the output voltage Vo is equal to or higher than the input voltage Vi and the duty ratio control amount Ds is smaller than the predetermined value Ds1, the control circuit 27 performs step-down at the on / off frequency fs with the on-period of the step-down switching element 31 fixed. You may operate | move so that the switching elements 30 and 31 may be turned on / off.
　制御回路２７は、時比率制御量Ｄｓが実質的にゼロであるときに、所定のオンオフ周波数ｆ１で昇圧用スイッチング素子３３、３５をオンオフし、かつ所定のオンオフ周波数ｆ１で降圧用スイッチング素子３０、３１をオンオフするように動作してもよい。 When the duty ratio control amount Ds is substantially zero, the control circuit 27 turns on and off the step-up switching elements 33 and 35 at a predetermined on / off frequency f1, and steps down the step-down switching element 30 at a predetermined on / off frequency f1. You may operate | move so that 31 may be turned on and off.
　また、制御回路２７は、時比率制御量Ｄｓが所定値Ｄｓ１より小さい所定値Ｄｓ３より小さくなったときに、昇圧用スイッチング素子３３、３５の動作と降圧用スイッチング素子３０、３１の動作とを入れ替えてもよい。すなわち、制御回路２７は、時比率制御量Ｄｓが所定値Ｄｓ１より小さい所定値Ｄｓ３以上であるときに、所定値Ｄｓ１の時比率で昇圧用スイッチング素子３３、３５を所定のオンオフ周波数ｆ１でオンオフし、オンオフ周波数ｆｓで降圧用スイッチング素子３０、３１をオンオフするように動作してもよい。この場合、制御回路２７は、時比率制御量Ｄｓが所定値Ｄｓ３より小さいときに、所定値Ｄｓ１の時比率で降圧用スイッチング素子３０、３１を所定のオンオフ周波数ｆ１でオンオフし、オンオフ周波数ｆｓで昇圧用スイッチング素子３３、３５をオンオフするように動作する。 Further, the control circuit 27 switches the operation of the step-up switching elements 33 and 35 and the operation of the step-down switching elements 30 and 31 when the duty ratio control amount Ds becomes smaller than the predetermined value Ds3 smaller than the predetermined value Ds1. May be. That is, when the duty ratio control amount Ds is equal to or larger than the predetermined value Ds3 smaller than the predetermined value Ds1, the control circuit 27 turns on and off the boosting switching elements 33 and 35 at the predetermined on / off frequency f1 at the time ratio of the predetermined value Ds1. The step-down switching elements 30 and 31 may be turned on and off at the on / off frequency fs. In this case, when the time ratio control amount Ds is smaller than the predetermined value Ds3, the control circuit 27 turns on and off the step-down switching elements 30 and 31 at the predetermined on / off frequency f1 at the time ratio of the predetermined value Ds1 and at the on / off frequency fs. The boosting switching elements 33 and 35 operate so as to be turned on and off.
　オンオフ周波数ｆｓの最低値は可聴周波数帯域Ｂｆの最高周波数ｆ０より高くてもよい。 The minimum value of the on / off frequency fs may be higher than the maximum frequency f0 of the audible frequency band Bf.
　制御回路２７は、降圧動作を行って出力電圧Ｖｏが入力電圧Ｖｉより低い場合に、図３に示すように、昇圧用スイッチング素子３３の時比率制御量Ｄｓの代わりに、オンオフ周波数ｆｓでオンオフされる降圧用スイッチング素子３１の時比率である時比率制御量Ｄｅを得てもよい。この場合には、時比率制御量Ｄｓの負の値である所定値Ｄｓ７、Ｄｓ６、Ｄｓ５の絶対値が時比率制御量Ｄｅの所定値Ｄｅ１、Ｄｅ２、Ｄｅ３にそれぞれ対応する。 When the step-down operation is performed and the output voltage Vo is lower than the input voltage Vi, the control circuit 27 is turned on / off at the on / off frequency fs instead of the time ratio control amount Ds of the step-up switching element 33 as shown in FIG. A time ratio control amount De that is a time ratio of the step-down switching element 31 may be obtained. In this case, the absolute values of the predetermined values Ds7, Ds6, and Ds5, which are negative values of the duty ratio control amount Ds, correspond to the predetermined values De1, De2, and De3 of the duty ratio control amount De, respectively.
　制御回路２７は、出力電圧Ｖｏが入力電圧Ｖｉより低い場合に、以下のように動作してもよい。すなわち、制御回路２７は、昇圧用スイッチング素子３３をオンにして昇圧用スイッチング素子３５をオフにしかつ降圧用スイッチング素子３０、３１を所定のオンオフ周波数ｆ１でオンオフする状態での降圧用スイッチング素子３１の時比率を時比率制御量Ｄｅとして得る。制御回路２７は、時比率制御量Ｄｅが所定値Ｄｅ１以上であるときには、昇圧用スイッチング素子３３をオンにして昇圧用スイッチング素子３５をオフにした状態で、時比率制御量Ｄｅの時比率で降圧用スイッチング素子３０、３１を所定のオンオフ周波数ｆ１でオンオフするように動作する。さらに、制御回路２７は、時比率制御量Ｄｅが所定値Ｄｅ１より小さいときには、所定値Ｄｅ１の時比率で降圧用スイッチング素子３０、３１を所定のオンオフ周波数ｆ１でオンオフし、時比率制御量Ｄｅに基づいて決定されたオンオフ周波数ｆｂで昇圧用スイッチング素子３３、３５をオンオフするように動作する。 The control circuit 27 may operate as follows when the output voltage Vo is lower than the input voltage Vi. In other words, the control circuit 27 turns on the step-up switching element 33, turns off the step-up switching element 35, and turns on the step-down switching elements 30, 31 at a predetermined on / off frequency f1. The hour ratio is obtained as the hour ratio control amount De. When the time ratio control amount De is equal to or greater than the predetermined value De1, the control circuit 27 steps down the voltage at the time ratio of the time ratio control amount De with the boost switching element 33 turned on and the boost switching element 35 turned off. The switching elements 30, 31 are operated so as to be turned on / off at a predetermined on / off frequency f1. Further, when the time ratio control amount De is smaller than the predetermined value De1, the control circuit 27 turns on and off the step-down switching elements 30 and 31 at a predetermined on / off frequency f1 at a time ratio of the predetermined value De1 to obtain the time ratio control amount De. The boosting switching elements 33 and 35 are operated to be turned on / off at the on / off frequency fb determined based on the on / off frequency fb.
　制御回路２７は、出力電圧Ｖｏが入力電圧Ｖｉより低い場合に、時比率制御量Ｄｅが所定値Ｄｅ１より小さいときには、昇圧用スイッチング素子３５のオン期間を固定した状態でオンオフ周波数ｆｂで昇圧用スイッチング素子３３、３５をオンオフするように動作してもよい。 When the output ratio Vo is lower than the input voltage Vi and the duty ratio control amount De is smaller than the predetermined value De1, the control circuit 27 performs boost switching at the on / off frequency fb with the on period of the boost switching element 35 fixed. You may operate | move so that the elements 33 and 35 may be turned on / off.
　また、制御回路２７は、時比率制御量Ｄｅが所定値Ｄｅ１より小さい所定値Ｄｅ３より小さくなったときに、昇圧用スイッチング素子３３、３５の動作と降圧用スイッチング素子３０、３１の動作とを入れ替えてもよい。すなわち、制御回路２７は、時比率制御量Ｄｅが所定値Ｄｅ１より小さい所定値Ｄｅ３以上であるときに、所定値Ｄｅ１の時比率で降圧用スイッチング素子３０、３１を所定のオンオフ周波数ｆ１でオンオフし、オンオフ周波数ｆｂで昇圧用スイッチング素子３３、３５をオンオフするように動作してもよい。この場合には、制御回路２７は、時比率制御量Ｄｅが所定値Ｄｅ３より小さいときに、所定値Ｄｅ１の時比率で昇圧用スイッチング素子３３、３５を所定のオンオフ周波数ｆ１でオンオフし、オンオフ周波数ｆｂで降圧用スイッチング素子３０、３１をオンオフするように動作する。 Further, the control circuit 27 switches the operation of the step-up switching elements 33 and 35 and the operation of the step-down switching elements 30 and 31 when the duty ratio control amount De becomes smaller than the predetermined value De3 smaller than the predetermined value De1. May be. That is, the control circuit 27 turns on and off the step-down switching elements 30 and 31 at the predetermined on / off frequency f1 at the time ratio of the predetermined value De1 when the time ratio control amount De is equal to or larger than the predetermined value De3 smaller than the predetermined value De1. The step-up switching elements 33 and 35 may be turned on / off at the on / off frequency fb. In this case, when the time ratio control amount De is smaller than the predetermined value De3, the control circuit 27 turns on and off the boosting switching elements 33 and 35 at the predetermined on / off frequency f1 at the time ratio of the predetermined value De1. It operates so as to turn on and off the step-down switching elements 30 and 31 at fb.
　制御回路２７は、昇圧用スイッチング素子３３、３５を同時にオフする期間を介して昇圧用スイッチング素子３３、３５のオンオフを切り替え、降圧用スイッチング素子３０、３１を同時にオフする期間を介して降圧用スイッチング素子３０、３１のオンオフを切り替えるように動作してもよい。 The control circuit 27 switches on / off of the step-up switching elements 33, 35 through a period in which the step-up switching elements 33, 35 are simultaneously turned off, and performs step-down switching through a period in which the step-down switching elements 30, 31 are simultaneously turned off. You may operate | move so that the elements 30 and 31 may be switched on / off.
　（実施の形態２）
　図１０は実施の形態２におけるＤＣ／ＤＣコンバータ１１Ａのブロック回路図である。図１０において、図１に示す実施の形態１におけるＤＣ／ＤＣコンバータ１１と同じ部分に同じ参照番号を付す。ＤＣ／ＤＣコンバータ１１Ａは図１に示す実施の形態１におけるＤＣ／ＤＣコンバータ１１の制御回路２７の代わりに制御回路２７Ａを備える。制御回路２７Ａは制御回路２７と異なるタイミングでスイッチング素子３０、３１、３３、３５をオンオフする。ＤＣ／ＤＣコンバータ１１Ａは、実施の形態１におけるＤＣ／ＤＣコンバータ１１と同様に、出力電圧Ｖｏが入力電圧Ｖｉに非常に近い場合でも正常に動作する。以下、より具体的に実施の形態２におけるＤＣ／ＤＣコンバータ１１Ａの動作について説明する。 (Embodiment 2)
FIG. 10 is a block circuit diagram of the DC / DC converter 11A in the second embodiment. 10, the same reference numerals are assigned to the same portions as those of DC / DC converter 11 in the first embodiment shown in FIG. The DC / DC converter 11A includes a control circuit 27A instead of the control circuit 27 of the DC / DC converter 11 in the first embodiment shown in FIG. The control circuit 27A turns on and off the switching elements 30, 31, 33, and 35 at a timing different from that of the control circuit 27. The DC / DC converter 11A operates normally even when the output voltage Vo is very close to the input voltage Vi, like the DC / DC converter 11 in the first embodiment. Hereinafter, the operation of the DC / DC converter 11A in the second embodiment will be described more specifically.
　まず、ＤＣ／ＤＣコンバータ１１Ａの昇圧動作について述べる。図１１はＤＣ／ＤＣコンバータ１１Ａの昇圧動作での降圧用スイッチング素子３０、３１と昇圧用スイッチング素子３３、３５のオンオフの状態を示す。図１１において、縦軸は各スイッチング素子のオンとオフの状態を示し、横軸は時刻を示す。図１１に示すように、この昇圧動作では、図２に示す実施の形態１におけるＤＣ／ＤＣコンバータ１１と同様に、昇圧用スイッチング素子３３、３５を所定のオンオフ周波数でオンオフを切り替えてかつ相補に動作させる。この動作により、ＤＣ／ＤＣコンバータ１１Ａは、入力電圧Ｖｉを昇圧して出力電圧Ｖｏを出力する。このとき、制御回路２７Ａは、出力電圧検出回路２５で検出された出力電圧Ｖｏが所定の設定電圧になるように、すなわち出力電圧Ｖｏに基づいて、昇圧用スイッチング素子３３、３５の時比率を時比率制御量として算出して得る。時比率とは、スイッチング素子のオンオフ周波数の１周期に対するオン期間の比率である。特に、制御回路２７Ａは昇圧用スイッチング素子３５の時比率を時比率制御量Ｄｓとして算出して得る。昇圧用スイッチング素子３３の時比率は、昇圧用スイッチング素子３３、３５の同時オフ期間が短い場合には、昇圧用スイッチング素子３５の時比率を１から引いた数、すなわち昇圧用スイッチング素子３５のオンオフ周波数の１周期に対するオフ期間の比率にほぼ等しい。この昇圧動作では、降圧用スイッチング素子３０をオンに維持してかつ降圧用スイッチング素子３１をオフに維持した状態で、昇圧用スイッチング素子３３、３５をオンオフ周波数ｆｂで相補的にオンオフして時比率を変化させてＰＷＭ制御を行っている。図１１に示す動作では、昇圧用スイッチング素子３３、３５は０．５の時比率で８０ｋＨｚのオンオフ周波数ｆｂで動作している。 First, the boosting operation of the DC / DC converter 11A will be described. FIG. 11 shows the on / off states of the step-down switching elements 30 and 31 and the step-up switching elements 33 and 35 in the step-up operation of the DC / DC converter 11A. In FIG. 11, the vertical axis indicates the on and off states of each switching element, and the horizontal axis indicates time. As shown in FIG. 11, in this step-up operation, as with the DC / DC converter 11 in the first embodiment shown in FIG. 2, the step-up switching elements 33 and 35 are switched on and off at a predetermined on-off frequency and complementarily. Make it work. With this operation, the DC / DC converter 11A boosts the input voltage Vi and outputs the output voltage Vo. At this time, the control circuit 27A sets the time ratio of the step-up switching elements 33 and 35 so that the output voltage Vo detected by the output voltage detection circuit 25 becomes a predetermined set voltage, that is, based on the output voltage Vo. Obtained by calculating as a ratio control amount. The duty ratio is the ratio of the on period to one cycle of the on / off frequency of the switching element. In particular, the control circuit 27A calculates the duty ratio of the boosting switching element 35 as the duty ratio control amount Ds. The time ratio of the boosting switching element 33 is the number obtained by subtracting the time ratio of the boosting switching element 35 from 1 when the simultaneous off period of the boosting switching elements 33 and 35 is short, that is, the boosting switching element 35 is turned on / off. It is approximately equal to the ratio of the off period to one period of the frequency. In this step-up operation, the step-up switching elements 33 and 35 are complementarily turned on and off at the on / off frequency fb while the step-down switching element 30 is kept on and the step-down switching element 31 is kept off. PWM control is performed by changing the above. In the operation shown in FIG. 11, the step-up switching elements 33 and 35 operate at an on / off frequency fb of 80 kHz at a time ratio of 0.5.
　次に、入力電圧Ｖｉが上昇してきた場合のＤＣ／ＤＣコンバータ１１Ａの動作について説明する。この場合、ＤＣ／ＤＣコンバータ１１Ａは、昇圧動作から降圧動作へ切り替わる。 Next, the operation of the DC / DC converter 11A when the input voltage Vi increases will be described. In this case, the DC / DC converter 11A switches from the step-up operation to the step-down operation.
　ＤＣ／ＤＣコンバータ１１Ａでは、時比率制御量Ｄｓとオンオフ周波数ｆとの相関関係が予め決定されており、制御回路２７Ａのメモリに記憶されている。ＤＣ／ＤＣコンバータ１１Ａの昇圧動作と降圧動作を切り替える際には、その相関関係に基づいて、制御回路２７Ａはスイッチング素子３０、３１、３３、３５のスイッチング動作を制御する。以下に、スイッチング素子３０、３１、３３、３５のスイッチング動作につき説明する。図１２は降圧用スイッチング素子３０、３１のオンオフ周波数ｆｓと、昇圧用スイッチング素子３３、３５のオンオフ周波数ｆｂと、時比率制御量Ｄｓとの相関関係を示す。図１２において、横軸は時比率制御量Ｄｓを示し、縦軸はオンオフ周波数を示す。 In the DC / DC converter 11A, the correlation between the duty ratio control amount Ds and the on / off frequency f is determined in advance and stored in the memory of the control circuit 27A. When switching between the step-up operation and the step-down operation of the DC / DC converter 11A, the control circuit 27A controls the switching operation of the switching elements 30, 31, 33, and 35 based on the correlation. Hereinafter, switching operations of the switching elements 30, 31, 33, and 35 will be described. FIG. 12 shows the correlation between the on / off frequency fs of the step-down switching elements 30 and 31, the on / off frequency fb of the step-up switching elements 33 and 35, and the time ratio control amount Ds. In FIG. 12, the horizontal axis represents the duty ratio control amount Ds, and the vertical axis represents the on / off frequency.
　図１１に示す動作では、上記したように、昇圧動作のみが行われているので、図１２において、時比率制御量Ｄｓが所定値Ｄｓ１１以上である範囲Ｒｓ１１に入っている。この場合には、制御回路２７Ａは昇圧用スイッチング素子３３、３５が相補な動作を行うように昇圧用スイッチング素子３３、３５をＰＷＭ制御する。図１１に示す動作では、時比率制御量Ｄｓが所定値Ｄｓ１１である。ここで、図１２に示すように、所定値Ｄｓ１１における昇圧用スイッチング素子３３、３５のオンオフ周波数ｆｂは周波数ｆ１（＝８０ｋＨｚ）である。したがって、昇圧用スイッチング素子３３、３５は１２．５μ秒の周期で相補にオンオフ制御されている。 In the operation shown in FIG. 11, since only the boosting operation is performed as described above, in FIG. 12, the duty ratio control amount Ds is in the range Rs11 that is equal to or greater than the predetermined value Ds11. In this case, the control circuit 27A performs PWM control of the boosting switching elements 33 and 35 so that the boosting switching elements 33 and 35 perform complementary operations. In the operation shown in FIG. 11, the duty ratio control amount Ds is the predetermined value Ds11. Here, as shown in FIG. 12, the on / off frequency fb of the step-up switching elements 33 and 35 at the predetermined value Ds11 is the frequency f1 (= 80 kHz). Therefore, the boosting switching elements 33 and 35 are complementarily controlled on and off with a period of 12.5 μsec.
　図１２に示すオンオフ周波数ｆｂとは、上記したとおり、例えば昇圧用スイッチング素子３３のＰＷＭ制御におけるオン期間を発生させる周波数である。したがって、図１２より所定値Ｄｓ１１の時比率制御量Ｄｓにおける降圧用スイッチング素子３０、３１のオンオフ周波数ｆｓは０Ｈｚである。オンオフ周波数ｆｓが０Ｈｚであるということは、その周期が無限大であるので、スイッチング素子はオンオフ動作を行わない。ゆえに、図１１に示すように、時比率制御量Ｄｓが所定値Ｄｓ１１以上である範囲Ｒｓ１１に入っているときには、制御回路２７Ａは降圧用スイッチング素子３０をオンに維持し、降圧用スイッチング素子３１をオフに維持する。 The on / off frequency fb shown in FIG. 12 is a frequency that generates an on period in the PWM control of the step-up switching element 33, for example, as described above. Therefore, from FIG. 12, the on / off frequency fs of the step-down switching elements 30 and 31 at the time ratio control amount Ds of the predetermined value Ds11 is 0 Hz. When the on / off frequency fs is 0 Hz, the cycle is infinite, so the switching element does not perform the on / off operation. Therefore, as shown in FIG. 11, when the duty ratio control amount Ds is in the range Rs11 that is equal to or greater than the predetermined value Ds11, the control circuit 27A keeps the step-down switching element 30 on and the step-down switching element 31 is turned on. Keep off.
　時比率制御量Ｄｓが所定値Ｄｓ１１より小さい範囲Ｒｓ１２に入ると、図１２に示すように、昇圧用スイッチング素子３３、３５のオンオフ周波数ｆｂは低下する。そして、時比率制御量Ｄｓが所定値Ｄｓ１２に至ると、昇圧用スイッチング素子３３、３５のオンオフ周波数ｆｂは周波数ｆ４（＝６０ｋＨｚ）となる。ゆえに、制御回路２７Ａは６０ｋＨｚの周波数での周期で昇圧用スイッチング素子３３、３５のオンオフを制御する。 When the duty ratio control amount Ds enters the range Rs12 smaller than the predetermined value Ds11, as shown in FIG. 12, the on / off frequency fb of the step-up switching elements 33 and 35 decreases. When the duty ratio control amount Ds reaches the predetermined value Ds12, the on / off frequency fb of the step-up switching elements 33 and 35 becomes the frequency f4 (= 60 kHz). Therefore, the control circuit 27A controls on / off of the step-up switching elements 33 and 35 in a cycle with a frequency of 60 kHz.
　図１３は、オンオフ周波数ｆｂが周波数ｆ４（＝６０ｋＨｚ）であるときのスイッチング素子３０、０１、３３、３５のオンオフの状態を示す。オンオフ周波数ｆ４（＝６０ｋＨｚ）の周期は約１６．６７μ秒であるので、昇圧用スイッチング素子３５は、１周期の間に固定期間である６．２５μ秒だけオンになる。図１３において、例えば時刻ｔ１から時刻ｔ３１までが１周期であり、時刻ｔ２１から時刻ｔ３１までが昇圧用スイッチング素子３５のオン期間である。ゆえに、制御回路２７Ａは昇圧用スイッチング素子３５のオフ期間を延ばし、その結果、パルスが減る。このような動作を繰り返すことで、制御回路２７Ａは昇圧比を下げる方向に昇圧用スイッチング素子３３、３５を制御している。このとき、図１３に示すように昇圧用スイッチング素子３３は昇圧用スイッチング素子３５と相補な動作を行う。降圧用スイッチング素子３０、３１は、図１２に示すように時比率制御量Ｄｓが所定値Ｄｓ１２であるときのオンオフ周波数ｆｓは０Ｈｚであるので、図１１に示す動作と同様の状態を維持し、降圧用スイッチング素子３０はオンに維持され、降圧用スイッチング素子３１はオフに維持される。 FIG. 13 shows the on / off state of the switching elements 30, 01, 33, and 35 when the on / off frequency fb is the frequency f4 (= 60 kHz). Since the cycle of the on / off frequency f4 (= 60 kHz) is about 16.67 μsec, the boosting switching element 35 is turned on for 6.25 μsec, which is a fixed period, during one cycle. In FIG. 13, for example, from time t1 to time t31 is one cycle, and from time t21 to time t31 is the ON period of the boosting switching element 35. Therefore, the control circuit 27A extends the off period of the boosting switching element 35, and as a result, the number of pulses decreases. By repeating such an operation, the control circuit 27A controls the boosting switching elements 33 and 35 in the direction of decreasing the boosting ratio. At this time, the boosting switching element 33 performs a complementary operation with the boosting switching element 35 as shown in FIG. The step-down switching elements 30 and 31 maintain the same state as the operation shown in FIG. 11 because the on / off frequency fs is 0 Hz when the duty ratio control amount Ds is the predetermined value Ds12 as shown in FIG. The step-down switching element 30 is kept on, and the step-down switching element 31 is kept off.
　時比率制御量Ｄｓが所定値Ｄｓ１２からさらに小さくなって所定値Ｄｓ１３に至ると、図１２に示すように、昇圧用スイッチング素子３３、３５のオンオフ周波数ｆｂは周波数ｆ３（＝４０ｋＨｚ）となる。図１４は時比率制御量Ｄｓが所定値Ｄｓ１３であるときのスイッチング素子３０、３１、３３、３５のオンオフの状態を示す。周波数ｆ３の周期は周波数ｆ１（＝８０ｋＨｚ）の２倍となるので２５μ秒となる。昇圧用スイッチング素子３５のオンされる固定期間が６．２５μ秒であるので、１周期の１／４が昇圧用スイッチング素子３５のオン期間になる。１周期は例えば時刻ｔ１から時刻ｔ５までであり、時刻ｔ１から時刻ｔ５までの期間のうち時刻ｔ４から時刻ｔ５までの期間が固定されたオン期間である。なお、図１４に示すように、昇圧用スイッチング素子３３は昇圧用スイッチング素子３５と相補な動作を行う。図１２に示すように、時比率制御量Ｄｓが所定値Ｄｓ１３であるときには、降圧用スイッチング素子３０、３１のオンオフ周波数ｆｓは０Ｈｚであるので、図１４に示すように、降圧用スイッチング素子３０がオンに維持され、スイッチング素子３１がオフに維持される。したがって、制御回路２７Ａは、昇圧比をさらに下げる。 When the duty ratio control amount Ds further decreases from the predetermined value Ds12 to the predetermined value Ds13, the on / off frequency fb of the boosting switching elements 33 and 35 becomes the frequency f3 (= 40 kHz) as shown in FIG. FIG. 14 shows the on / off states of the switching elements 30, 31, 33, and 35 when the duty ratio control amount Ds is a predetermined value Ds13. The period of the frequency f3 is twice the frequency f1 (= 80 kHz), and thus becomes 25 μsec. Since the fixed period during which the boosting switching element 35 is turned on is 6.25 μsec, ¼ of one cycle is the on period of the boosting switching element 35. One period is, for example, from time t1 to time t5, and is an on period in which the period from time t4 to time t5 is fixed among the period from time t1 to time t5. As shown in FIG. 14, the boosting switching element 33 performs a complementary operation with the boosting switching element 35. As shown in FIG. 12, when the duty ratio control amount Ds is a predetermined value Ds13, the on / off frequency fs of the step-down switching elements 30 and 31 is 0 Hz. Therefore, as shown in FIG. The switching element 31 is kept off while being kept on. Therefore, the control circuit 27A further reduces the boost ratio.
　図１２に示すように、時比率制御量Ｄｓが所定値Ｄｓ１３からさらに小さくなって所定値Ｄｓ１４に至ると、図１２に示すように、昇圧用スイッチング素子３３、３５のオンオフ周波数ｆｂは周波数ｆ０（＝１８ｋＨｚ）ではなく０Ｈｚとなる。図１５は時比率制御量Ｄｓが所定値Ｄｓ１４であるときのスイッチング素子３０、３１、３３、３５のオンオフの状態を示す。図１５に示すように、制御回路２７Ａは、昇圧用スイッチング素子３５はオフに維持し、昇圧用スイッチング素子３３はオンに維持する。このとき、図１２に示すように降圧用スイッチング素子３０、３１のオンオフ周波数ｆｓは０ｋＨｚであるので、図１５に示すように、制御回路２７Ａは降圧用スイッチング素子３０をオンに維持し、降圧用スイッチング素子３１をオフに維持する。したがって、時比率制御量Ｄｓが所定値Ｄｓ１４であるときには、制御回路２７Ａはすべてのスイッチング素子のオンオフ動作を停止し、昇圧用スイッチング素子３３と降圧用スイッチング素子３０のみをオンに維持して昇圧用スイッチング素子３５と降圧用スイッチング素子３１をオフに維持することで、入力端子１５と出力端子１９を直結し、入力電圧Ｖｉと出力電圧Ｖｏを実質的に等しくする。このように、時比率制御量Ｄｓが所定値Ｄｓ１４であるときにはスイッチング素子３０、３１、３３、３５のスイッチング動作が行われないので、ＤＣ／ＤＣコンバータ１１Ａは実施の形態１におけるＤＣ／ＤＣコンバータ１１よりも効率が向上する。 As shown in FIG. 12, when the duty ratio control amount Ds is further reduced from the predetermined value Ds13 to the predetermined value Ds14, as shown in FIG. 12, the on / off frequency fb of the boosting switching elements 33 and 35 is set to the frequency f0 ( = 18 kHz), not 0 Hz. FIG. 15 shows the on / off state of the switching elements 30, 31, 33, and 35 when the duty ratio control amount Ds is a predetermined value Ds14. As shown in FIG. 15, the control circuit 27A keeps the boosting switching element 35 off and keeps the boosting switching element 33 on. At this time, since the on / off frequency fs of the step-down switching elements 30 and 31 is 0 kHz as shown in FIG. 12, the control circuit 27A keeps the step-down switching element 30 on as shown in FIG. The switching element 31 is kept off. Therefore, when the duty ratio control amount Ds is the predetermined value Ds14, the control circuit 27A stops the on / off operation of all the switching elements, and keeps only the boosting switching element 33 and the step-down switching element 30 on to increase the voltage for boosting. By keeping the switching element 35 and the step-down switching element 31 off, the input terminal 15 and the output terminal 19 are directly connected, and the input voltage Vi and the output voltage Vo are made substantially equal. Thus, since the switching operation of the switching elements 30, 31, 33, and 35 is not performed when the duty ratio control amount Ds is the predetermined value Ds14, the DC / DC converter 11A is the DC / DC converter 11 in the first embodiment. More efficient.
　ＤＣ／ＤＣコンバータ１１Ａにおいて時比率制御量Ｄｓが所定値Ｄｓ１４であるときのオンオフ周波数ｆｂが周波数ｆ０（０＜ｆ０＜１８ｋＨｚ）ではなく０Ｈｚであることにより、実施の形態１におけるＤＣ／ＤＣコンバータ１１の時比率制御量Ｄｓが所定値Ｄｓ４であるときの動作と同様に騒音を低減することができる。なお、騒音が問題とならない場合は、オンオフ周波数ｆｂの最低の周波数をゼロにして、範囲Ｒｓ１２、Ｒｓ１３において昇圧用スイッチング素子３３、３５のオンオフ周波数ｆｂと時比率制御量Ｄｓとの相関関係を連続にしてもよい。 In the DC / DC converter 11A, the on / off frequency fb when the duty ratio control amount Ds is the predetermined value Ds14 is not the frequency f0 (0 <f0 <18 kHz) but 0 Hz, so that the DC / DC converter 11 in the first embodiment is used. The noise can be reduced similarly to the operation when the time ratio control amount Ds is the predetermined value Ds4. If noise is not a problem, the minimum frequency of the on / off frequency fb is set to zero, and the correlation between the on / off frequency fb of the step-up switching elements 33 and 35 and the duty ratio control amount Ds is continuously obtained in the ranges Rs12 and Rs13. It may be.
　降圧用スイッチング素子３０、３１のオンオフ周波数ｆｓと時比率制御量Ｄｓとの相関関係は、縦軸について昇圧用スイッチング素子３３、３５のオンオフ周波数ｆｂと時比率制御量Ｄｓとの相関関係に対して対称である。図１２に示すように、時比率制御量Ｄｓが昇圧用スイッチング素子３３、３５と降圧用スイッチング素子３０、３１とが実質的に同じ周期でオンオフ制御される所定値Ｄｓ４に至ると、制御回路２７Ａは昇圧用スイッチング素子３３、３５の動作と降圧用スイッチング素子３０、３１の動作とを入れ替える。時比率制御量Ｄｓが所定値Ｄｓ１４より小さいときにはＤＣ／ＤＣコンバータ１１Ａは降圧動作を行っており（Ｖｏ＜Ｖｉ）、図１２に示すように、制御回路２７Ａは昇圧用スイッチング素子３３をオンに維持し、昇圧用スイッチング素子３５をオフに維持する。 The correlation between the on / off frequency fs of the step-down switching elements 30 and 31 and the time ratio control amount Ds is relative to the correlation between the on / off frequency fb of the step-up switching elements 33 and 35 and the time ratio control amount Ds about the vertical axis. Symmetric. As shown in FIG. 12, when the duty ratio control amount Ds reaches a predetermined value Ds4 in which the step-up switching elements 33 and 35 and the step-down switching elements 30 and 31 are ON / OFF controlled in substantially the same cycle, the control circuit 27A Switches the operation of the step-up switching elements 33 and 35 and the operation of the step-down switching elements 30 and 31. When the duty ratio control amount Ds is smaller than the predetermined value Ds14, the DC / DC converter 11A performs a step-down operation (Vo <Vi), and the control circuit 27A keeps the step-up switching element 33 on as shown in FIG. Then, the boosting switching element 35 is kept off.
　なお、実質的に同じ周期でオンオフ制御される状態についての定義は実施の形態１と同じである。したがって、昇圧用スイッチング素子３３、３５の動作と降圧用スイッチング素子３０、３１の動作とは厳密に時比率制御量Ｄｓが所定値Ｄｓ１４に至った時点である必要はない。ただし、図１２に示すように、時比率制御量Ｄｓが所定値Ｄｓ１４以上であるときには制御回路２７Ａは降圧用スイッチング素子３０をオンに維持してかつ降圧用スイッチング素子３１をオフに維持しており、時比率制御量Ｄｓが所定値Ｄｓ１４より小さいときには制御回路２７Ａは昇圧用スイッチング素子３３をオンに維持してかつ昇圧用スイッチング素子３５をオフに維持しているので、その周期は無限大となる。しかし、例えば降圧用スイッチング素子３０がオンのままでかつ降圧用スイッチング素子３１がオフのままであれば、いずれも周期が無限大であるので、実施の形態１で述べた「実質的に同じ周期でオンオフ制御される状態」を含む。したがって、ここでは、オンオフ制御はオンのみのオン制御及びオフのみのオフ制御を含むものと定義する。 Note that the definition of the state in which the on / off control is performed at substantially the same cycle is the same as in the first embodiment. Therefore, the operation of the step-up switching elements 33 and 35 and the operation of the step-down switching elements 30 and 31 do not have to be strictly at the point when the time ratio control amount Ds reaches the predetermined value Ds14. However, as shown in FIG. 12, when the duty ratio control amount Ds is equal to or greater than the predetermined value Ds14, the control circuit 27A keeps the step-down switching element 30 on and keeps the step-down switching element 31 off. When the duty ratio control amount Ds is smaller than the predetermined value Ds14, since the control circuit 27A keeps the boosting switching element 33 on and keeps the boosting switching element 35 off, the cycle becomes infinite. . However, for example, if the step-down switching element 30 remains on and the step-down switching element 31 remains off, the period is infinite. State that is controlled to be turned on / off by ". Therefore, on / off control is defined here as including ON-only ON control and OFF-only OFF control.
　時比率制御量Ｄｓが所定値Ｄｓ１４から小さくなり所定値Ｄｓ１５に至ると、図１２に示すように、降圧用スイッチング素子３０、３１のオンオフ周波数ｆｓは周波数ｆ３（＝４０ｋＨｚ）となる。図１６は時比率制御量Ｄｓが所定値Ｄｓ１５であるときのスイッチング素子３０、３１、３３、３５のオンオフの状態を示す。時比率制御量Ｄｓが所定値Ｄｓ１５であるときには、制御回路２７Ａは降圧用スイッチング素子３１が周波数ｆ３（＝４０ｋＨｚ）の周期（２５μ秒）のうち固定されたオン期間（６．２５μ秒）にオンにする制御を繰り返す。降圧用スイッチング素子３０は降圧用スイッチング素子３１と相補な動作を行う。このとき、制御回路２７Ａは昇圧用スイッチング素子３３をオンに維持してかつ昇圧用スイッチング素子３５をオフに維持する。 When the time ratio control amount Ds decreases from the predetermined value Ds14 to the predetermined value Ds15, as shown in FIG. 12, the on / off frequency fs of the step-down switching elements 30 and 31 becomes the frequency f3 (= 40 kHz). FIG. 16 shows the on / off states of the switching elements 30, 31, 33, and 35 when the duty ratio control amount Ds is a predetermined value Ds15. When the duty ratio control amount Ds is the predetermined value Ds15, the control circuit 27A turns on the step-down switching element 31 in the fixed on period (6.25 μsec) in the period (25 μsec) of the frequency f3 (= 40 kHz). Repeat the control. The step-down switching element 30 performs a complementary operation with the step-down switching element 31. At this time, the control circuit 27A keeps the boosting switching element 33 on and keeps the boosting switching element 35 off.
　時比率制御量Ｄｓが所定値Ｄｓ１５よりさらに小さくなって所定値Ｄｓ１６に至ると、図１２に示すように、降圧用スイッチング素子３０、３１のオンオフ周波数ｆｓは周波数ｆ４（＝６０ｋＨｚ）となる。図１７は時比率制御量Ｄｓが所定値Ｄｓ１６であるときのスイッチング素子３０、３１、３３、３５のオンオフの状態を示す。時比率制御量Ｄｓが所定値Ｄｓ１６であるときには、制御回路２７Ａは周波数ｆ４（＝６０ｋＨｚ）の周期（１６．６７μ秒）のうち固定オン期間（６．２５μ秒）にスイッチング素子３１をオンにする制御を繰り返す。降圧用スイッチング素子３０は降圧用スイッチング素子３１と相補な動作を行う。このとき、制御回路２７Ａは昇圧用スイッチング素子３３をオンに維持してかつ昇圧用スイッチング素子３５をオフに維持する。 When the duty ratio control amount Ds becomes further smaller than the predetermined value Ds15 and reaches the predetermined value Ds16, as shown in FIG. 12, the on / off frequency fs of the step-down switching elements 30 and 31 becomes the frequency f4 (= 60 kHz). FIG. 17 shows an on / off state of the switching elements 30, 31, 33, and 35 when the duty ratio control amount Ds is a predetermined value Ds16. When the duty ratio control amount Ds is the predetermined value Ds16, the control circuit 27A turns on the switching element 31 in the fixed on period (6.25 μsec) in the period (16.67 μsec) of the frequency f4 (= 60 kHz). Repeat control. The step-down switching element 30 performs a complementary operation with the step-down switching element 31. At this time, the control circuit 27A keeps the boosting switching element 33 on and keeps the boosting switching element 35 off.
　時比率制御量Ｄｓが所定値Ｄｓ１６からさらに小さくなり所定値Ｄｓ１７に至ると、図１２に示すように、降圧用スイッチング素子３０、３１のオンオフ周波数ｆｓを周波数ｆ１（＝８０ｋＨｚ）にする。図１８は時比率制御量Ｄｓが所定値Ｄｓ１７であるときのスイッチング素子３０、３１、３３、３５のオンオフの状態を示す。時比率制御量Ｄｓが所定値Ｄｓ１７であるときには、制御回路２７Ａは周波数ｆ１（＝８０ｋＨｚ）の周期（１２．５μ秒）で固定オン期間（６．２５μ秒）に降圧用スイッチング素子３１をオンにする制御を繰り返す。降圧用スイッチング素子３０は、降圧用スイッチング素子３１と相補な動作を行う。このとき、制御回路２７Ａは昇圧用スイッチング素子３３をオンに維持してかつ昇圧用スイッチング素子３５をオフに維持する。 When the duty ratio control amount Ds further decreases from the predetermined value Ds16 and reaches the predetermined value Ds17, the on / off frequency fs of the step-down switching elements 30 and 31 is set to the frequency f1 (= 80 kHz) as shown in FIG. FIG. 18 shows an on / off state of the switching elements 30, 31, 33, and 35 when the duty ratio control amount Ds is a predetermined value Ds17. When the duty ratio control amount Ds is the predetermined value Ds17, the control circuit 27A turns on the step-down switching element 31 in the fixed on-period (6.25 μsec) with a period (12.5 μsec) of the frequency f1 (= 80 kHz). Repeat the control. The step-down switching element 30 performs a complementary operation with the step-down switching element 31. At this time, the control circuit 27A keeps the boosting switching element 33 on and keeps the boosting switching element 35 off.
　時比率制御量Ｄｓが所定値Ｄｓ１４より小さく所定値Ｄｓ１７より大きい範囲Ｒｓ１３から所定値Ｄｓ１７以下の範囲Ｒｓ１４に入ると、制御回路２７Ａは降圧用スイッチング素子３０、３１のオンオフ周波数ｆｓがＰＷＭ制御に用いられる周波数ｆ１（＝８０ｋＨｚ）に至る。時比率制御量Ｄｓが範囲Ｒｓ１４に入ると、図１２に示すように、制御回路２７Ａは昇圧用スイッチング素子３３をオンに維持してかつ昇圧用スイッチング素子３５をオフに維持した状態でオンオフ周波数ｆｓを周波数ｆ１（＝８０ｋＨｚ）に維持し、降圧用スイッチング素子３０、３１の時比率を変化させるＰＷＭ制御により降圧動作を行う。 When the duty ratio control amount Ds is within the range Rs14 smaller than the predetermined value Ds14 and larger than the predetermined value Ds17 to the range Rs14 below the predetermined value Ds17, the control circuit 27A uses the on / off frequency fs of the step-down switching elements 30 and 31 for PWM control. Frequency f1 (= 80 kHz). When the duty ratio control amount Ds falls within the range Rs14, as shown in FIG. 12, the control circuit 27A keeps the boosting switching element 33 on and keeps the boosting switching element 35 off. Is maintained at the frequency f1 (= 80 kHz), and the step-down operation is performed by PWM control that changes the time ratio of the step-down switching elements 30 and 31.
　太陽電池である直流電源２８の発電量が少ない状態から多くなった場合、ＤＣ／ＤＣコンバータ１１Ａは昇圧動作から昇降圧動作を経て降圧動作へスムースに切り替わる。この昇降圧動作において、制御回路２７Ａは時比率制御量Ｄｓとオンオフ周波数ｆｂ、ｆｓとの相関関係に基づいて、ＰＷＭ制御されているスイッチング素子のオン期間を固定した状態でそのスイッチング素子の周期を増減させるので、簡単な動作で昇降圧動作を切替えることが可能となる。 When the amount of power generated by the DC power supply 28, which is a solar battery, increases from a small state, the DC / DC converter 11A smoothly switches from a step-up operation to a step-down operation through a step-up / step-down operation. In this step-up / step-down operation, the control circuit 27A sets the cycle of the switching element in a state where the ON period of the PWM controlled switching element is fixed based on the correlation between the duty ratio control amount Ds and the on / off frequencies fb and fs. Since it is increased or decreased, the step-up / step-down operation can be switched with a simple operation.
　なお、直流電源２８の発電量が多い状態から少なくなった場合は、制御回路２７Ａは上記と逆の動作を行う。この場合、第１所定値が所定値Ｄｓ１７に代わり、第３所定値が所定値Ｄｓ１１に代わる。 When the amount of power generated by the DC power supply 28 is reduced from a large state, the control circuit 27A performs the reverse operation. In this case, the first predetermined value is replaced with the predetermined value Ds17, and the third predetermined value is replaced with the predetermined value Ds11.
　上記した昇圧動作から降圧動作に切り替わる際の制御回路２７Ａによる制御を以下にまとめる。制御回路２７Ａは、昇圧動作から降圧動作に切り替える際に、時比率制御量Ｄｓがパルス幅変調制御を行なえなくなる第１所定値Ｄｓ１１に至ると、パルス幅変調制御を行っている昇圧用スイッチング素子３３、３５に対し、予め決定された時比率制御量Ｄｓとオンオフ周波数ｆｂとの相関関係に基づいて求められる周期毎に、昇圧用スイッチング素子３３、３５の一方のオン期間を固定した状態でオン制御を行なうとともに、昇圧用スイッチング素子３３、３５の他方のオフ期間を固定した状態でオフ制御を行なう。そして、制御回路２７Ａは、時比率制御量Ｄｓが実質的にオンオフ制御されない際の第２所定値Ｄｓ１４に至ると、昇圧用スイッチング素子３３、３５の動作と降圧用スイッチング素子３０、３１の動作とを入れ替える。そして、制御回路２７Ａは、時比率制御量Ｄｓが第３所定値Ｄｓ１７に至ると、降圧用スイッチング素子３０、３１により降圧動作を行う。 The control by the control circuit 27A when switching from the step-up operation described above to the step-down operation is summarized below. When the control circuit 27A switches from the step-up operation to the step-down operation and the time ratio control amount Ds reaches the first predetermined value Ds11 at which the pulse width modulation control cannot be performed, the step-up switching element 33 that performs the pulse width modulation control. , 35, the ON control is performed in a state in which one ON period of the step-up switching elements 33, 35 is fixed for each period obtained based on the correlation between the predetermined time ratio control amount Ds and the ON / OFF frequency fb. And the off control is performed with the other off period of the boosting switching elements 33 and 35 being fixed. When the duty ratio control amount Ds reaches the second predetermined value Ds14 when the on / off control is not substantially performed, the control circuit 27A performs the operations of the step-up switching elements 33 and 35 and the operation of the step-down switching elements 30 and 31. Replace. When the duty ratio control amount Ds reaches the third predetermined value Ds17, the control circuit 27A performs the step-down operation by the step-down switching elements 30 and 31.
　制御回路２７Ａは、降圧動作から昇圧動作に切り替える際に、時比率制御量Ｄｓが第１所定値Ｄｓ１７より小さい値からパルス幅変調制御を行なえなくなる第１所定値Ｄｓ１７に至ると、パルス幅変調制御を行っている降圧用スイッチング素子３０、３１に対し、予め決定された時比率制御量Ｄｓとオンオフ周波数ｆｓとの相関関係に基づいて求められる周期毎に、降圧用スイッチング素子３０、３１の一方の降圧用スイッチング素子３１のオン期間を固定した状態でオン制御を行なうとともに、降圧用スイッチング素子３０、３１の他方のスイッチング素子３０のオフ期間を固定した状態でオフ制御を行なう。そして、制御回路２７Ａは、時比率制御量Ｄｓが実質的にオンオフ制御されない際の第２所定値Ｄｓ１４に至ると、昇圧用スイッチング素子３３、３５の動作と降圧用スイッチング素子３０、３１の動作とを入れ替える。そして、制御回路２７Ａは、時比率制御量Ｄｓが第３所定値Ｄｓ１１に至ると、昇圧用スイッチング素子３３、３５により昇圧動作を行う。 When the control circuit 27A switches from the step-down operation to the step-up operation, the pulse width modulation control is performed when the duty ratio control amount Ds reaches a first predetermined value Ds17 at which the pulse width modulation control cannot be performed from a value smaller than the first predetermined value Ds17. One of the step-down switching elements 30 and 31 for each period determined based on the correlation between the predetermined time ratio control amount Ds and the on / off frequency fs. On-control is performed with the on-period of the step-down switching element 31 fixed, and off-control is performed with the off-period of the other switching element 30 of the step-down switching elements 30, 31 fixed. When the duty ratio control amount Ds reaches the second predetermined value Ds14 when the on / off control is not substantially performed, the control circuit 27A performs the operations of the step-up switching elements 33 and 35 and the operation of the step-down switching elements 30 and 31. Replace. Then, when the duty ratio control amount Ds reaches the third predetermined value Ds11, the control circuit 27A performs the boosting operation by the boosting switching elements 33 and 35.
　以上のように、制御回路２７Ａは、昇圧動作のみを行う場合に昇圧用スイッチング素子３３、３５に対してＰＷＭ制御を行い、降圧動作のみを行う場合に降圧用スイッチング素子３０、３１に対してＰＷＭ制御を行なう。そして、制御回路２７Ａは、上記相関関係に基づいて合計４つのスイッチング素子３０、３１、３３、３５を制御することにより昇降圧動作の切替が可能となる。この切替時に、予め決定された時比率制御量Ｄｓとオンオフ周波数ｆｓ、ｆｂとの相関関係に基づいて求められる周期毎に、オン期間を固定してオン制御とオフ制御を行なうので、図１９と図２０に示す従来のＤＣ／ＤＣコンバータの２つの三角波を得るための回路が不要となり、簡単な構成で昇降圧が可能なＤＣ／ＤＣコンバータ１１Ａが得られる。 As described above, the control circuit 27A performs PWM control on the boosting switching elements 33 and 35 when only the boosting operation is performed, and performs PWM control on the step-down switching elements 30 and 31 when performing only the bucking operation. Take control. The control circuit 27A can switch the step-up / step-down operation by controlling a total of four switching elements 30, 31, 33, and 35 based on the correlation. At the time of switching, the on period and the off control are performed with the on period fixed for each period obtained based on the correlation between the predetermined time ratio control amount Ds and the on / off frequencies fs and fb. A circuit for obtaining the two triangular waves of the conventional DC / DC converter shown in FIG. 20 is not required, and a DC / DC converter 11A capable of step-up / step-down with a simple configuration is obtained.
　上述のように、制御回路２７Ａは、出力電圧Ｖｏが入力電圧Ｖｉ以上である場合に以下のように動作する。制御回路２７Ａは、降圧用スイッチング素子３０をオンにして降圧用スイッチング素子３１をオフにしかつ昇圧用スイッチング素子３３、３５を所定のオンオフ周波数ｆ１でオンオフする状態での昇圧用スイッチング素子３５の時比率を時比率制御量Ｄｓとして出力電圧Ｖｏに基づいて得る。制御回路２７Ａは、時比率制御量Ｄｓが所定値Ｄｓ１１以上であるときには、降圧用スイッチング素子３０をオンにして降圧用スイッチング素子３１をオフにした状態で、時比率制御量Ｄｓの時比率で昇圧用スイッチング素子３３、３５を所定のオンオフ周波数ｆ１でオンオフする。制御回路２７Ａは、時比率制御量Ｄｓが所定値Ｄｓ１１より小さいときには、降圧用スイッチング素子３０をオンにして降圧用スイッチング素子３１をオフにした状態で、昇圧用スイッチング素子３３、３５を時比率制御量Ｄｓに基づいて決定されたオンオフ周波数ｆｂでオンオフする。 As described above, the control circuit 27A operates as follows when the output voltage Vo is equal to or higher than the input voltage Vi. The control circuit 27A turns on the step-down switching element 30, turns off the step-down switching element 31, and turns on and off the step-up switching elements 33 and 35 at a predetermined on / off frequency f1. Is obtained as the duty ratio control amount Ds based on the output voltage Vo. When the time ratio control amount Ds is equal to or greater than the predetermined value Ds11, the control circuit 27A boosts the time ratio control amount Ds with the time ratio while the step-down switching element 30 is turned on and the step-down switching element 31 is turned off. The switching elements 33 and 35 are turned on / off at a predetermined on / off frequency f1. When the time ratio control amount Ds is smaller than the predetermined value Ds11, the control circuit 27A controls the step-up switching elements 33 and 35 with the time ratio control with the step-down switching element 30 turned on and the step-down switching element 31 turned off. The signal is turned on / off at an on / off frequency fb determined based on the quantity Ds.
　制御回路２７Ａは、降圧動作を行って出力電圧Ｖｏが入力電圧Ｖｉより低い場合に、図１２に示すように、昇圧用スイッチング素子３３の時比率制御量Ｄｓの代わりに、オンオフ周波数ｆｓでオンオフされる降圧用スイッチング素子３１の時比率である時比率制御量Ｄｅを得てもよい。この場合には、時比率制御量Ｄｓの負の値である所定値Ｄｓ１７、Ｄｓ１６、Ｄｓ１５の絶対値が時比率制御量Ｄｅの所定値Ｄｅ１１、Ｄｅ１２、Ｄｅ１３にそれぞれ対応する。 When the step-down operation is performed and the output voltage Vo is lower than the input voltage Vi, the control circuit 27A is turned on / off at the on / off frequency fs instead of the time ratio control amount Ds of the step-up switching element 33 as shown in FIG. A time ratio control amount De that is a time ratio of the step-down switching element 31 may be obtained. In this case, the absolute values of the predetermined values Ds17, Ds16, and Ds15 that are negative values of the duty ratio control amount Ds correspond to the predetermined values De11, De12, and De13 of the duty ratio control amount De, respectively.
　制御回路２７Ａは、出力電圧Ｖｏが入力電圧Ｖｉより低い場合に、以下のように動作する。すなわち制御回路２７Ａは、昇圧用スイッチング素子３３をオンにして昇圧用スイッチング素子３５をオフにしかつ降圧用スイッチング素子３０、３１を所定のオンオフ周波数ｆ１でオンオフする状態での降圧用スイッチング素子３１の時比率を時比率制御量Ｄｅとして出力電圧Ｖｏに基づいて得る。制御回路２７Ａは、時比率制御量Ｄｅが所定値Ｄｅ１１以上であるときには、昇圧用スイッチング素子３３をオンにして昇圧用スイッチング素子３５をオフにした状態で、時比率制御量Ｄｅの時比率で降圧用スイッチング素子３０、３１を所定のオンオフ周波数ｆ１でオンオフする。制御回路２７Ａは、時比率制御量Ｄｅが所定値Ｄｅ１１より小さいときには、昇圧用スイッチング素子３３をオンにして昇圧用スイッチング素子３５をオフにした状態で、降圧用スイッチング素子３０、３１を時比率制御量Ｄｅに基づいて決定されたオンオフ周波数ｆｓでオンオフする。 The control circuit 27A operates as follows when the output voltage Vo is lower than the input voltage Vi. That is, the control circuit 27A turns on the step-down switching element 33 in a state where the step-up switching element 33 is turned on, the step-up switching element 35 is turned off, and the step-down switching elements 30 and 31 are turned on / off at a predetermined on / off frequency f1. The ratio is obtained as the duty ratio control amount De based on the output voltage Vo. When the time ratio control amount De is equal to or greater than the predetermined value De11, the control circuit 27A reduces the voltage at the time ratio of the time ratio control amount De with the boost switching element 33 turned on and the boost switching element 35 turned off. The switching elements 30, 31 are turned on / off at a predetermined on / off frequency f1. When the time ratio control amount De is smaller than the predetermined value De11, the control circuit 27A controls the step-down switching elements 30 and 31 with the time ratio control while the step-up switching element 33 is turned on and the step-up switching element 35 is turned off. The on / off frequency fs determined based on the quantity De is turned on / off.
　制御回路２７Ａは、時比率制御量Ｄｅが実質的にゼロであるときに、昇圧用スイッチング素子３３と降圧用スイッチング素子３０とを同時にオンにしてかつ昇圧用スイッチング素子３５と降圧用スイッチング素子３１とを同時にオフするように動作してもよい。 When the duty ratio control amount De is substantially zero, the control circuit 27A turns on the boost switching element 33 and the step-down switching element 30 at the same time, and sets the boost switching element 35 and the step-down switching element 31 to May be turned off simultaneously.
　オンオフ周波数ｆｂの最低値とオンオフ周波数ｆｓの最低値は可聴周波数帯域Ｂｆの最高周波数ｆ０より高くてもよい。 The minimum value of the on / off frequency fb and the minimum value of the on / off frequency fs may be higher than the maximum frequency f0 of the audible frequency band Bf.
　制御回路２７Ａは、昇圧用スイッチング素子３３、３５を同時にオフする期間を介して昇圧用スイッチング素子３３、３５のオンオフを切り替え、降圧用スイッチング素子３０、３１を同時にオフする期間を介して降圧用スイッチング素子３０、３１のオンオフを切り替えてもよい。 The control circuit 27A switches on / off of the step-up switching elements 33, 35 through a period in which the step-up switching elements 33, 35 are simultaneously turned off, and performs step-down switching through a period in which the step-down switching elements 30, 31 are simultaneously turned off. The elements 30 and 31 may be switched on / off.
　実施の形態１におけるＤＣ／ＤＣコンバータ１１と実施の形態２におけるＤＣ／ＤＣコンバータ１１Ａとの違いを以下にまとめる。 Differences between the DC / DC converter 11 in the first embodiment and the DC / DC converter 11A in the second embodiment are summarized below.
　図１から図３に示す実施の形態１におけるＤＣ／ＤＣコンバータ１１では、図２から図６に示す動作までで、オンオフ動作をしていなかった降圧用スイッチング素子３１のオン制御がオン期間（６．２５μ秒）を固定した状態で行われる。そして、その頻度が図３に示す相関関係から求められる。ゆえに、実施の形態１におけるＤＣ／ＤＣコンバータ１１では、昇圧から降圧へ動作が切り替わる際に、まず降圧用スイッチング素子３１がオンになるパルスが増える。降圧用スイッチング素子３０は降圧用スイッチング素子３１と相補な動作を行うので、降圧用スイッチング素子３０をオフにするパルスが増える。 In the DC / DC converter 11 according to the first embodiment shown in FIGS. 1 to 3, the on-control of the step-down switching element 31 that has not been turned on / off until the operation shown in FIGS. .25 μs) is fixed. And the frequency is calculated | required from the correlation shown in FIG. Therefore, in the DC / DC converter 11 according to the first embodiment, when the operation is switched from step-up to step-down, first, the number of pulses for turning on the step-down switching element 31 increases. Since the step-down switching element 30 performs a complementary operation with the step-down switching element 31, the number of pulses for turning off the step-down switching element 30 increases.
　次に、図７から図９に示すように、時比率制御量Ｄｓが負に至ると、昇圧用スイッチング素子３３のオン制御が、オン期間（６．２５μ秒）を固定した状態で行われる。そして、オン制御の頻度が図３に示す相関関係から求められる。ゆえに、実施の形態１におけるＤＣ／ＤＣコンバータ１１では、昇圧動作から降圧動作へ動作が切り替わる際に、時比率制御量Ｄｓが負になると昇圧用スイッチング素子３３がオンになるパルスが増え、昇圧用スイッチング素子３５がオフになるパルスが増える。 Next, as shown in FIG. 7 to FIG. 9, when the duty ratio control amount Ds reaches a negative value, the ON control of the boosting switching element 33 is performed with the ON period (6.25 μsec) being fixed. And the frequency of ON control is calculated | required from the correlation shown in FIG. Therefore, in the DC / DC converter 11 according to the first embodiment, when the operation is switched from the step-up operation to the step-down operation, if the time ratio control amount Ds becomes negative, the number of pulses for turning on the step-up switching element 33 increases. The number of pulses that turn off the switching element 35 increases.
　以上より、実施の形態１におけるＤＣ／ＤＣコンバータ１１では、図３に示すように、昇圧動作から降圧動作へ切り替える際に、昇圧動作でＰＷＭ制御されていない降圧用スイッチング素子３０、３１のパルスを増やし、降圧動作に入れば降圧用スイッチング素子３０、３１に対してＰＷＭ制御を行う。昇圧動作でＰＷＭ制御されていた昇圧用スイッチング素子３３、３５）は、降圧用スイッチング素子３０、３１と逆の動作を行う。 As described above, in the DC / DC converter 11 according to the first embodiment, as shown in FIG. 3, when switching from the step-up operation to the step-down operation, the pulses of the step-down switching elements 30 and 31 that are not PWM-controlled by the step-up operation are applied. When the step-down operation is increased, PWM control is performed on the step-down switching elements 30 and 31. The step-up switching elements 33, 35) that have been PWM-controlled by the step-up operation perform the reverse operation of the step-down switching elements 30, 31.
　実施の形態２におけるＤＣ／ＤＣコンバータ１１Ａでは、昇圧動作から降圧動作へ切り替える際に、図１１から図１５に示す動作で、昇圧動作でＰＷＭ制御されていた昇圧用スイッチング素子３３のオン期間が固定されてかつオンになる周期が図１２に示す相関関係により決定される。これにより、昇圧用スイッチング素子３３のパルスは減っていく。図１６から図１８に示すように、降圧動作では昇圧用スイッチング素子３３はオン状態を維持する。昇圧用スイッチング素子３５は昇圧用スイッチング素子３３と相補な動作を行う。また、降圧用スイッチング素子３０、３１は、図１２に示すように、昇圧用スイッチング素子３３、３５と逆の動作を行う。 In the DC / DC converter 11A according to the second embodiment, when switching from the step-up operation to the step-down operation, the ON period of the step-up switching element 33 that has been PWM-controlled by the step-up operation is fixed in the operation shown in FIGS. The turn-on and turn-on periods are determined by the correlation shown in FIG. Thereby, the pulse of the step-up switching element 33 decreases. As shown in FIGS. 16 to 18, in the step-down operation, the step-up switching element 33 maintains the on state. The step-up switching element 35 performs an operation complementary to the step-up switching element 33. Further, the step-down switching elements 30 and 31 perform the reverse operation of the step-up switching elements 33 and 35 as shown in FIG.
　したがって、実施の形態１におけるＤＣ／ＤＣコンバータ１１では、昇圧動作または降圧動作を行うためのＰＷＭ制御がされていないスイッチング素子のパルスを制御して昇降圧切替を行い、実施の形態２におけるＤＣ／ＤＣコンバータ１１Ａでは、昇圧動作または降圧動作を行うためのＰＷＭ制御がされているスイッチング素子のパルスを制御して昇降圧切替を行う。いずれの制御を採用しても、簡単な構成で昇動作と降圧動作の切替が可能となるＤＣ／ＤＣコンバータ１１、１１Ａが得られる。 Therefore, in DC / DC converter 11 in the first embodiment, the step-up / step-down switching is performed by controlling the pulse of the switching element that is not subjected to the PWM control for performing the step-up operation or the step-down operation. In the DC converter 11A, the step-up / step-down switching is performed by controlling the pulse of the switching element that is PWM controlled to perform the step-up operation or the step-down operation. Regardless of which control is employed, the DC / DC converters 11 and 11A that can switch between the ascending operation and the step-down operation with a simple configuration can be obtained.
　実施の形態２におけるＤＣ／ＤＣコンバータ１１Ａにおいても、実施の形態１におけるＤＣ／ＤＣコンバータ１１と同様に、昇圧用スイッチング素子３３、３５が同時にオフになる同時オフ期間を介してオンオフを切り替え、降圧用スイッチング素子３０、３１が同時にオフになる同時オフ期間を介してオンオフを切り替えてもよい。 Also in the DC / DC converter 11A in the second embodiment, as in the DC / DC converter 11 in the first embodiment, the step-down switching elements 33 and 35 are switched on and off through the simultaneous off period in which the step-up switching elements 33 and 35 are simultaneously turned off. The on / off may be switched through a simultaneous off period in which the switching elements 30, 31 are turned off at the same time.
　また、実施の形態２におけるＤＣ／ＤＣコンバータ１１Ａでは、制御回路２７Ａは、時比率制御量Ｄｓが所定値Ｄｓ１４以上であるときには降圧用スイッチング素子３０、３１をオンまたはオフに維持してオンオフ周波数ｆｓをゼロにし、時比率制御量Ｄｓが所定値Ｄｓ１４以下であるときには昇圧用スイッチング素子３３、３５をオンまたはオフに維持してオンオフ周波数ｆｂをゼロにしている。これに限らず、例えば制御回路２７Ａは、時比率制御量Ｄｓが所定値Ｄｓ１４以上であるときには降圧用スイッチング素子３０、３１を可聴周波数帯域Ｂｆの最高周波数ｆ０（＝１８ｋＨｚ）のオンオフ周波数ｆｓでオンオフし、時比率制御量Ｄｓが所定値Ｄｓ１４以下であるときには昇圧用スイッチング素子３３、３５を可聴周波数帯域Ｂｆの最高周波数ｆ０（＝１８ｋＨｚ）のオンオフ周波数ｆｂでオンオフしてもよい。 In the DC / DC converter 11A according to the second embodiment, the control circuit 27A maintains the step-down switching elements 30 and 31 on or off when the duty ratio control amount Ds is equal to or greater than the predetermined value Ds14, and the on / off frequency fs. When the duty ratio control amount Ds is equal to or less than the predetermined value Ds14, the step-up switching elements 33 and 35 are kept on or off, and the on / off frequency fb is made zero. For example, the control circuit 27A turns on and off the step-down switching elements 30 and 31 at the on / off frequency fs of the highest frequency f0 (= 18 kHz) in the audible frequency band Bf when the duty ratio control amount Ds is equal to or greater than the predetermined value Ds14. When the duty ratio control amount Ds is equal to or less than the predetermined value Ds14, the boosting switching elements 33 and 35 may be turned on / off at the on / off frequency fb of the highest frequency f0 (= 18 kHz) of the audible frequency band Bf.
　実施の形態１、２におけるＤＣ／ＤＣコンバータ１１、１１Ａでは、上記の相関関係において、時比率制御量Ｄｓとともにオンオフ周波数ｆｓ、ｆｂが直線的に変化するが、これに限定されるものではなく、ＤＣ／ＤＣコンバータ１１、１１Ａの仕様などに応じて、時比率制御量Ｄｓとともにオンオフ周波数ｆｓ、ｆｂが直線的ではなく他の関係で変化してもよい。 In the DC / DC converters 11 and 11A according to the first and second embodiments, the on / off frequencies fs and fb change linearly with the time ratio control amount Ds in the above correlation, but the present invention is not limited to this. Depending on the specifications of the DC / DC converters 11 and 11A and the like, the on / off frequencies fs and fb together with the duty ratio control amount Ds may be changed in another relationship instead of linear.
　また、実施の形態１、２におけるＤＣ／ＤＣコンバータ１１、１１Ａに接続される直流電源２８は太陽電池である。直流電源２８は、所望の出力電圧Ｖｏに対して、入力電圧Ｖｉの変動が大きく、昇降圧動作が必要な構成、例えば二次電池であってもよく、ＤＣ／ＤＣコンバータ１１、１１Ａは二次電池の充放電回路等に適用してもよい。 Further, the DC power supply 28 connected to the DC / DC converters 11 and 11A in the first and second embodiments is a solar cell. The DC power supply 28 may be a configuration in which the input voltage Vi greatly varies with respect to the desired output voltage Vo and requires a step-up / step-down operation, for example, a secondary battery. The DC / DC converters 11 and 11A are secondary batteries. You may apply to the charging / discharging circuit etc. of a battery.
　本発明にかかるＤＣ／ＤＣコンバータは昇圧と降圧の両方を行うことが可能であるので、特に入力電圧の変動が大きい太陽電池等の直流電源用のＤＣ／ＤＣコンバータ等として有用である。 Since the DC / DC converter according to the present invention can perform both step-up and step-down operations, it is particularly useful as a DC / DC converter for a DC power source such as a solar cell having a large input voltage fluctuation.
１１，１１Ａ　　ＤＣ／ＤＣコンバータ
１５　　入力端子
１７　　グランド端子
１９　　出力端子
２１　　インダクタ
２７，２７Ａ　　制御回路
３０　　降圧用スイッチング素子（第１の降圧用スイッチング素子）
３０Ｐ　　接続点（第１の接続点）
３１　　降圧用スイッチング素子（第２の降圧用スイッチング素子）
３３　　昇圧用スイッチング素子（第１の昇圧用スイッチング素子）
３３Ｐ　　接続点（第２の接続点）
３５　　昇圧用スイッチング素子（第２の昇圧用スイッチング素子）
Ｄｅ　　時比率制御量（第２の時比率制御量）
Ｄｅ１　　所定値（第２の所定値）
Ｄｅ３　　所定値（第３の所定値）
Ｄｅ１１　　所定値（第２の所定値）
Ｄｓ　　時比率制御量（第１の時比率制御量）
Ｄｓ１　　所定値（第１の所定値）
Ｄｓ３　　所定値（第２の所定値）
Ｄｓ１１　　所定値（第１の所定値）
ｆ１　　オンオフ周波数（所定のオンオフ周波数）
ｆｂ　　オンオフ周波数（第２のオンオフ周波数）
ｆｓ　　オンオフ周波数（第１のオンオフ周波数） 11, 11A DC / DC converter 15 Input terminal 17 Ground terminal 19 Output terminal 21 Inductor 27, 27A Control circuit 30 Step-down switching element (first step-down switching element)
30P connection point (first connection point)
31 Step-down switching element (second step-down switching element)
33 Boosting switching element (first boosting switching element)
33P connection point (second connection point)
35 Boosting switching element (second boosting switching element)
De time ratio control amount (second time ratio control amount)
De1 predetermined value (second predetermined value)
De3 predetermined value (third predetermined value)
De11 predetermined value (second predetermined value)
Ds time ratio control amount (first time ratio control amount)
Ds1 predetermined value (first predetermined value)
Ds3 predetermined value (second predetermined value)
Ds11 predetermined value (first predetermined value)
f1 On / off frequency (predetermined on / off frequency)
fb On / off frequency (second on / off frequency)
fs On / off frequency (first on / off frequency)

Claims (18)

  1. 　　　グランド端子と、
    　　　前記グランド端子との間に入力電圧が印加されるように構成された入力端子と、
    　　　前記グランド端子との間に出力電圧を出力するように構成された出力端子と、
    　　　前記入力端子と第１の接続点との間に電気的に直列に接続された第１の降圧用スイッチング素子と、
    　　　前記グランド端子と前記第１の接続点との間に電気的に直列に接続され、前記第１の降圧用スイッチング素子と相補な動作を行う第２の降圧用スイッチング素子と、
    　　　前記出力端子と第２の接続点との間に電気的に直列に接続された第１の昇圧用スイッチング素子と、
    　　　前記グランド端子と前記第２の接続点との間に電気的に直列に接続され、前記第１の昇圧用スイッチング素子と相補な動作を行う第２の昇圧用スイッチング素子と、
    　　　前記第１の接続点と前記第２の接続点との間に電気的に直列に接続されたインダクタと、
    　　　前記第１の降圧用スイッチング素子と前記第２の降圧用スイッチング素子と前記第１の昇圧用スイッチング素子と前記第２の昇圧用スイッチング素子とに電気的に接続された制御回路と、
    を備え、
    前記制御回路は、前記出力電圧が前記入力電圧以上である場合に、
    　　　前記第１の降圧用スイッチング素子をオンにして前記第２の降圧用スイッチング素子をオフにしかつ前記第１の昇圧用スイッチング素子と前記第２の昇圧用スイッチング素子とを所定のオンオフ周波数でオンオフする状態での前記第２の昇圧用スイッチング素子の時比率を第１の時比率制御量として前記出力電圧に基づいて得て、
    　　　前記第１の時比率制御量が第１の所定値以上であるときには、前記第１の降圧用スイッチング素子をオンにして前記第２の降圧用スイッチング素子をオフにした状態で前記第１の時比率制御量の時比率で前記第１の昇圧用スイッチング素子と前記第２の昇圧用スイッチング素子とを前記所定のオンオフ周波数でオンオフし、
    　　　前記第１の時比率制御量が前記第１の所定値より小さいときには、前記第１の所定値の時比率で前記第１の昇圧用スイッチング素子と前記第２の昇圧用スイッチング素子とを前記所定のオンオフ周波数でオンオフし、前記第１の時比率制御量に基づいて決定された第１のオンオフ周波数で前記第１の降圧用スイッチング素子と前記第２の降圧用スイッチング素子とをオンオフする、
    ように動作する、ＤＣ／ＤＣコンバータ。     A ground terminal;
    An input terminal configured to apply an input voltage to the ground terminal;
    An output terminal configured to output an output voltage to and from the ground terminal;
    A first step-down switching element electrically connected in series between the input terminal and a first connection point;
    A second step-down switching element electrically connected in series between the ground terminal and the first connection point and performing an operation complementary to the first step-down switching element;
    A first step-up switching element electrically connected in series between the output terminal and a second connection point;
    A second step-up switching element electrically connected in series between the ground terminal and the second connection point and performing an operation complementary to the first step-up switching element;
    An inductor electrically connected in series between the first connection point and the second connection point;
    A control circuit electrically connected to the first step-down switching element, the second step-down switching element, the first step-up switching element, and the second step-up switching element;
    With
    The control circuit, when the output voltage is greater than or equal to the input voltage,
    The first step-down switching element is turned on, the second step-down switching element is turned off, and the first step-up switching element and the second step-up switching element are turned on / off at a predetermined on / off frequency. Obtaining a time ratio of the second step-up switching element in a state as a first time ratio control amount based on the output voltage;
    When the first time ratio control amount is greater than or equal to a first predetermined value, the first time-step switching element is turned on and the second step-down switching element is turned off. The first boosting switching element and the second boosting switching element are turned on / off at the predetermined on / off frequency at a time ratio of the ratio control amount,
    When the first time ratio control amount is smaller than the first predetermined value, the first boost switching element and the second boost switching element are connected to the predetermined boost ratio at the first predetermined time ratio. The first step-down switching element and the second step-down switching element are turned on / off at a first on / off frequency determined based on the first duty ratio control amount.
    DC / DC converter that operates as follows.
  2. 前記制御回路は、前記出力電圧が前記入力電圧以上である場合に、前記第１の時比率制御量が前記第１の所定値より小さいときには、前記第２の降圧用スイッチング素子をオンにするオン期間を固定した状態で前記第１のオンオフ周波数で前記第１の降圧用スイッチング素子と前記第２の降圧用スイッチング素子とをオンオフするように動作する、請求項１に記載のＤＣ／ＤＣコンバータ。 The control circuit turns on the second step-down switching element when the output voltage is equal to or higher than the input voltage and the first time ratio control amount is smaller than the first predetermined value. 2. The DC / DC converter according to claim 1, wherein the first step-down switching element and the second step-down switching element are operated to be turned on / off at the first on / off frequency in a state where the period is fixed.
  3. 前記制御回路は、前記第１の時比率制御量が実質的にゼロであるときに、前記所定のオンオフ周波数で前記第１の昇圧用スイッチング素子と前記第２の昇圧用スイッチング素子とをオンオフし、かつ前記所定のオンオフ周波数で前記第１の降圧用スイッチング素子と前記第２の降圧用スイッチング素子とをオンオフするように動作する、請求項１に記載のＤＣ／ＤＣコンバータ。 The control circuit turns on and off the first boosting switching element and the second boosting switching element at the predetermined on / off frequency when the first duty ratio control amount is substantially zero. The DC / DC converter according to claim 1, wherein the DC / DC converter operates to turn on and off the first step-down switching element and the second step-down switching element at the predetermined on / off frequency.
  4. 前記制御回路は、
    　　　前記第１の時比率制御量が前記第１の所定値より小さい第２の所定値以上であるときに、前記第１の所定値の時比率で前記第１の昇圧用スイッチング素子と前記第２の昇圧用スイッチング素子とを前記所定のオンオフ周波数でオンオフし、前記第１のオンオフ周波数で前記第１の降圧用スイッチング素子と前記第２の降圧用スイッチング素子とをオンオフし、
    　　　前記第１の時比率制御量が前記第２の所定値より小さいときに、前記第１の所定値の時比率で前記第１の降圧用スイッチング素子と前記第２の降圧用スイッチング素子とを前記所定のオンオフ周波数でオンオフし、前記第１のオンオフ周波数で前記第１の昇圧用スイッチング素子と前記第２の昇圧用スイッチング素子とをオンオフする、
    ように動作する、請求項１に記載のＤＣ／ＤＣコンバータ。     The control circuit includes:
    When the first time ratio control amount is equal to or greater than a second predetermined value smaller than the first predetermined value, the first boost switching element and the second at a time ratio of the first predetermined value. And switching on and off the first step-down switching element and the second step-down switching element at the first on / off frequency,
    When the first time ratio control amount is smaller than the second predetermined value, the first step-down switching element and the second step-down switching element are set at the time ratio of the first predetermined value. Turning on and off at a predetermined on / off frequency, and turning on and off the first boosting switching element and the second boosting switching element at the first on / off frequency;
    The DC / DC converter according to claim 1 which operates as follows.
  5. 前記第１のオンオフ周波数の最低値は可聴周波数帯域の最高周波数より高い、請求項１に記載のＤＣ／ＤＣコンバータ。 The DC / DC converter according to claim 1, wherein the lowest value of the first on / off frequency is higher than the highest frequency of an audible frequency band.
  6. 前記制御回路は、前記出力電圧が前記入力電圧より低い場合に、
    　　　前記第１の昇圧用スイッチング素子をオンにして前記第２の昇圧用スイッチング素子をオフにしかつ前記第１の降圧用スイッチング素子と前記第２の降圧用スイッチング素子とを前記所定のオンオフ周波数でオンオフする状態での前記第２の降圧用スイッチング素子の時比率を第２の時比率制御量として得て、
    　　　前記第２の時比率制御量が第２の所定値以上であるときには、前記第１の昇圧用スイッチング素子をオンにして前記第２の昇圧用スイッチング素子をオフにした状態で、前記第２の時比率制御量の時比率で前記第１の降圧用スイッチング素子と前記第２の降圧用スイッチング素子とを前記所定のオンオフ周波数でオンオフし、
    　　　前記第２の時比率制御量が前記第２の所定値より小さいときには、前記第２の所定値の時比率で前記第１の降圧用スイッチング素子と前記第２の降圧用スイッチング素子とを前記所定のオンオフ周波数でオンオフし、前記第２の時比率制御量に基づいて決定された第２のオンオフ周波数で前記第１の昇圧用スイッチング素子と前記第２の昇圧用スイッチング素子とをオンオフする、
    ように動作する、請求項１に記載のＤＣ／ＤＣコンバータ。     The control circuit, when the output voltage is lower than the input voltage,
    The first step-up switching element is turned on, the second step-up switching element is turned off, and the first step-down switching element and the second step-down switching element are turned on / off at the predetermined on / off frequency. Obtaining a time ratio of the second step-down switching element in a state to be a second time ratio control amount;
    When the second duty ratio control amount is equal to or greater than a second predetermined value, the second boosting switching element is turned on and the second boosting switching element is turned off. Turning on and off the first step-down switching element and the second step-down switching element at the predetermined on / off frequency at a time ratio of a time ratio control amount;
    When the second time ratio control amount is smaller than the second predetermined value, the first step-down switching element and the second step-down switching element are connected to the predetermined amount at the time ratio of the second predetermined value. The first boost switching element and the second boost switching element are turned on / off at a second on / off frequency determined based on the second duty ratio control amount,
    The DC / DC converter according to claim 1 which operates as follows.
  7. 前記制御回路は、前記出力電圧が前記入力電圧より低い場合に、前記第２の時比率制御量が前記第２の所定値より小さいときには、前記第２の昇圧用スイッチング素子をオンにするオン期間を固定した状態で前記第２のオンオフ周波数で前記第１の昇圧用スイッチング素子と前記第２の昇圧用スイッチング素子とをオンオフするように動作する、請求項６に記載のＤＣ／ＤＣコンバータ。 The control circuit is configured to turn on the second step-up switching element when the output voltage is lower than the input voltage and the second time ratio control amount is smaller than the second predetermined value. 7. The DC / DC converter according to claim 6, wherein the first boosting switching element and the second boosting switching element are operated to be turned on / off at the second on / off frequency in a fixed state.
  8. 前記制御回路は、
    　　　前記第２の時比率制御量が前記第２の所定値より小さい第３の所定値以上であるときに、前記第２の所定値の時比率で前記第１の降圧用スイッチング素子と前記第２の降圧用スイッチング素子とを前記所定のオンオフ周波数でオンオフし、前記第２のオンオフ周波数で前記第１の昇圧用スイッチング素子と前記第２の昇圧用スイッチング素子とをオンオフし、
    　　　前記第２の時比率制御量が前記第３の所定値より小さいときに、前記第２の所定値の時比率で前記第１の昇圧用スイッチング素子と前記第２の昇圧用スイッチング素子とを前記所定のオンオフ周波数でオンオフし、前記第２のオンオフ周波数で前記第１の降圧用スイッチング素子と前記第２の降圧用スイッチング素子とをオンオフする、
    ように動作する、請求項６に記載のＤＣ／ＤＣコンバータ。     The control circuit includes:
    When the second time ratio control amount is equal to or greater than a third predetermined value smaller than the second predetermined value, the first step-down switching element and the second at a time ratio of the second predetermined value. The step-down switching element is turned on / off at the predetermined on / off frequency, the first step-up switching element and the second step-up switching element are turned on / off at the second on-off frequency,
    When the second time ratio control amount is smaller than the third predetermined value, the first boosting switching element and the second boosting switching element at the second predetermined value time ratio Turning on and off at a predetermined on / off frequency, and turning on and off the first step-down switching element and the second step-down switching element at the second on / off frequency;
    The DC / DC converter according to claim 6 which operates as follows.
  9. 前記制御回路は、
    　　　前記第１の昇圧用スイッチング素子と前記第２の昇圧用スイッチング素子とを同時にオフする期間を介して前記第１の昇圧用スイッチング素子と前記第２の昇圧用スイッチング素子とのオンオフを切り替え、
    　　　前記第１の降圧用スイッチング素子と前記第２の降圧用スイッチング素子とを同時にオフする期間を介して前記第１の降圧用スイッチング素子と前記第２の降圧用スイッチング素子とのオンオフを切り替える、
    ように動作する、請求項１に記載のＤＣ／ＤＣコンバータ。     The control circuit includes:
    Switching on and off of the first boosting switching element and the second boosting switching element through a period of simultaneously turning off the first boosting switching element and the second boosting switching element;
    Switching on and off the first step-down switching element and the second step-down switching element through a period in which the first step-down switching element and the second step-down switching element are simultaneously turned off;
    The DC / DC converter according to claim 1 which operates as follows.
  10. 　　　グランド端子と、
    　　　前記グランド端子との間に入力電圧が印加されるように構成された入力端子と、
    　　　前記グランド端子との間に出力電圧を出力するように構成された出力端子と、
    　　　前記入力端子と第１の接続点との間に電気的に直列に接続された第１の降圧用スイッチング素子と、
    　　　前記グランド端子と前記第１の接続点との間に電気的に直列に接続され、前記第１の降圧用スイッチング素子と相補な動作を行う第２の降圧用スイッチング素子と、
    　　　前記出力端子と第２の接続点との間に電気的に直列に接続された第１の昇圧用スイッチング素子と、
    　　　前記グランド端子と前記第２の接続点との間に電気的に直列に接続され、前記第１の昇圧用スイッチング素子と相補な動作を行う第２の昇圧用スイッチング素子と、
    　　　前記第１の接続点と前記第２の接続点との間に電気的に直列に接続されたインダクタと、
    　　　前記第１の降圧用スイッチング素子と前記第２の降圧用スイッチング素子と前記第１の昇圧用スイッチング素子と前記第２の昇圧用スイッチング素子とに電気的に接続された制御回路と、
    を備え、
    前記制御回路は、前記出力電圧が前記入力電圧より低い場合に、
    　　　前記第１の昇圧用スイッチング素子をオンにして前記第２の昇圧用スイッチング素子をオフにしかつ前記第１の降圧用スイッチング素子と前記第２の降圧用スイッチング素子とを前記所定のオンオフ周波数でオンオフする状態での前記第２の降圧用スイッチング素子の時比率を時比率制御量として前記出力電圧に基づいて得て、
    　　　前記時比率制御量が所定値以上であるときには前記時比率制御量の時比率で前記第１の降圧用スイッチング素子と前記第２の降圧用スイッチング素子とを前記所定のオンオフ周波数でオンオフし、
    　　　前記第２の時比率制御量が前記所定値より小さいときには、前記所定値の時比率で前記第１の降圧用スイッチング素子と前記第２の降圧用スイッチング素子とを前記所定のオンオフ周波数でオンオフし、前記時比率制御量に基づいて決定されたオンオフ周波数で前記第１の昇圧用スイッチング素子と前記第２の昇圧用スイッチング素子とをオンオフする、
    ように動作する、ＤＣ／ＤＣコンバータ。     A ground terminal;
    An input terminal configured to apply an input voltage to the ground terminal;
    An output terminal configured to output an output voltage to and from the ground terminal;
    A first step-down switching element electrically connected in series between the input terminal and a first connection point;
    A second step-down switching element electrically connected in series between the ground terminal and the first connection point and performing an operation complementary to the first step-down switching element;
    A first step-up switching element electrically connected in series between the output terminal and a second connection point;
    A second step-up switching element electrically connected in series between the ground terminal and the second connection point and performing an operation complementary to the first step-up switching element;
    An inductor electrically connected in series between the first connection point and the second connection point;
    A control circuit electrically connected to the first step-down switching element, the second step-down switching element, the first step-up switching element, and the second step-up switching element;
    With
    The control circuit, when the output voltage is lower than the input voltage,
    The first step-up switching element is turned on, the second step-up switching element is turned off, and the first step-down switching element and the second step-down switching element are turned on / off at the predetermined on / off frequency. Obtaining a time ratio of the second step-down switching element in a state of being based on the output voltage as a time ratio control amount;
    When the time ratio control amount is equal to or greater than a predetermined value, the first step-down switching element and the second step-down switching element are turned on / off at the predetermined on / off frequency at the time ratio of the time ratio control amount,
    When the second time ratio control amount is smaller than the predetermined value, the first step-down switching element and the second step-down switching element are turned on / off at the predetermined on / off frequency at the time ratio of the predetermined value. Turning on and off the first boosting switching element and the second boosting switching element at an on / off frequency determined based on the duty ratio control amount;
    DC / DC converter that operates as follows.
  11. 前記制御回路は、前記出力電圧が前記入力電圧より低い場合に、前記時比率制御量が前記所定値より小さいときには、前記第２の昇圧用スイッチング素子のオン期間を固定した状態で前記時比率制御量に基づいて決定された前記オンオフ周波数で前記第１の昇圧用スイッチング素子と前記第２の昇圧用スイッチング素子とをオンオフするように動作する、請求項１０に記載のＤＣ／ＤＣコンバータ。 When the output voltage is lower than the input voltage and the time ratio control amount is smaller than the predetermined value, the control circuit controls the time ratio control while fixing the ON period of the second boosting switching element. 11. The DC / DC converter according to claim 10, wherein the DC / DC converter operates to turn on and off the first boosting switching element and the second boosting switching element at the on / off frequency determined based on a quantity.
  12. 前記制御回路は、前記時比率制御量が実質的にゼロであるときに、前記所定のオンオフ周波数で前記第１の降圧用スイッチング素子と前記第２の降圧用スイッチング素子とをオンオフし、かつ前記所定のオンオフ周波数で前記第１の昇圧用スイッチング素子と前記第２の昇圧用スイッチング素子とをオンオフするように動作する、請求項１０に記載のＤＣ／ＤＣコンバータ。 The control circuit turns on and off the first step-down switching element and the second step-down switching element at the predetermined on / off frequency when the duty ratio control amount is substantially zero; and The DC / DC converter according to claim 10, wherein the DC / DC converter operates to turn on and off the first boosting switching element and the second boosting switching element at a predetermined on / off frequency.
  13. 前記時比率制御量に基づいて決定された前記オンオフ周波数の最低値は可聴周波数帯域の最高周波数より高い、請求項１０に記載のＤＣ／ＤＣコンバータ。 The DC / DC converter according to claim 10, wherein a minimum value of the on / off frequency determined based on the duty ratio control amount is higher than a maximum frequency of an audible frequency band.
  14. 前記制御回路は、
    　　　前記第１の昇圧用スイッチング素子と前記第２の昇圧用スイッチング素子とを同時にオフする期間を介して前記第１の昇圧用スイッチング素子と前記第２の昇圧用スイッチング素子とのオンオフを切り替え、
    　　　前記第１の降圧用スイッチング素子と前記第２の降圧用スイッチング素子とを同時にオフする期間を介して前記第１の降圧用スイッチング素子と前記第２の降圧用スイッチング素子とのオンオフを切り替える、
    ように動作する、請求項１０に記載のＤＣ／ＤＣコンバータ。     The control circuit includes:
    Switching on and off of the first boosting switching element and the second boosting switching element through a period of simultaneously turning off the first boosting switching element and the second boosting switching element;
    Switching on and off the first step-down switching element and the second step-down switching element through a period in which the first step-down switching element and the second step-down switching element are simultaneously turned off;
    The DC / DC converter according to claim 10, which operates as follows.
  15. 　　　グランド端子と、
    　　　前記グランド端子との間に入力電圧が印加されるように構成された入力端子と、
    　　　前記グランド端子との間に出力電圧を出力するように構成された出力端子と、
    　　　前記入力端子と第１の接続点との間に電気的に直列に接続された第１の降圧用スイッチング素子と、
    　　　前記グランド端子と前記第１の接続点との間に電気的に直列に接続され、前記第１の降圧用スイッチング素子と相補な動作を行う第２の降圧用スイッチング素子と、
    　　　前記出力端子と第２の接続点との間に電気的に直列に接続された第１の昇圧用スイッチング素子と、
    　　　前記グランド端子と前記第２の接続点との間に電気的に直列に接続され、前記第１の昇圧用スイッチング素子と相補な動作を行う第２の昇圧用スイッチング素子と、
    　　　前記第１の接続点と前記第２の接続点との間に電気的に直列に接続されたインダクタと、
    　　　前記第１の降圧用スイッチング素子と前記第２の降圧用スイッチング素子と前記第１の昇圧用スイッチング素子と前記第２の昇圧用スイッチング素子とに電気的に接続された制御回路と、
    を備え、
    前記制御回路は、前記出力電圧が前記入力電圧以上である場合に、
    　　　前記第１の降圧用スイッチング素子をオンにして前記第２の降圧用スイッチング素子をオフにしかつ前記第１の昇圧用スイッチング素子と前記第２の昇圧用スイッチング素子とを所定のオンオフ周波数でオンオフする状態での前記第２の昇圧用スイッチング素子の時比率を第１の時比率制御量として前記出力電圧に基づいて得て、
    　　　前記第１の時比率制御量が第１の所定値以上であるときには、前記第１の降圧用スイッチング素子をオンにして前記第２の降圧用スイッチング素子をオフにした状態で、前記第１の時比率制御量の時比率で前記第１の昇圧用スイッチング素子と前記第２の昇圧用スイッチング素子とを前記所定のオンオフ周波数でオンオフし、
    　　　前記時比率制御量が前記第１の所定値より小さいときには、前記第１の降圧用スイッチング素子をオンにして前記第２の降圧用スイッチング素子をオフにした状態で、前記第１の昇圧用スイッチング素子と前記第２の昇圧用スイッチング素子とを前記第１の時比率制御量に基づいて決定された第１のオンオフ周波数でオンオフする、
    ように動作し、
    前記制御回路は、前記出力電圧が前記入力電圧より低い場合に、
    　　　前記第１の昇圧用スイッチング素子をオンにして前記第２の昇圧用スイッチング素子をオフにしかつ前記第１の降圧用スイッチング素子と前記第２の降圧用スイッチング素子とを前記所定のオンオフ周波数でオンオフする状態での前記第２の降圧用スイッチング素子の時比率を第２の時比率制御量として前記出力電圧に基づいて得て、
    　　　前記第２の時比率制御量が第２の所定値以上であるときには、前記第１の昇圧用スイッチング素子をオンにして前記第２の昇圧用スイッチング素子をオフにした状態で、前記第２の時比率制御量の時比率で前記第１の降圧用スイッチング素子と前記第２の降圧用スイッチング素子とを前記所定のオンオフ周波数でオンオフし、
    　　　前記第２の時比率制御量が前記第２の所定値より小さいときには、前記第１の昇圧用スイッチング素子をオンにして前記第２の昇圧用スイッチング素子をオフにした状態で、前記第１の降圧用スイッチング素子と前記第２の降圧用スイッチング素子とを前記第２の時比率制御量に基づいて決定された第２のオンオフ周波数でオンオフする、
    ように動作する、ＤＣ／ＤＣコンバータ。     A ground terminal;
    An input terminal configured to apply an input voltage to the ground terminal;
    An output terminal configured to output an output voltage to and from the ground terminal;
    A first step-down switching element electrically connected in series between the input terminal and a first connection point;
    A second step-down switching element electrically connected in series between the ground terminal and the first connection point and performing an operation complementary to the first step-down switching element;
    A first step-up switching element electrically connected in series between the output terminal and a second connection point;
    A second step-up switching element electrically connected in series between the ground terminal and the second connection point and performing an operation complementary to the first step-up switching element;
    An inductor electrically connected in series between the first connection point and the second connection point;
    A control circuit electrically connected to the first step-down switching element, the second step-down switching element, the first step-up switching element, and the second step-up switching element;
    With
    The control circuit, when the output voltage is greater than or equal to the input voltage,
    The first step-down switching element is turned on, the second step-down switching element is turned off, and the first step-up switching element and the second step-up switching element are turned on / off at a predetermined on / off frequency. Obtaining a time ratio of the second step-up switching element in a state as a first time ratio control amount based on the output voltage;
    When the first duty ratio control amount is equal to or greater than a first predetermined value, the first step-down switching element is turned on and the second step-down switching element is turned off. Turning on and off the first step-up switching element and the second step-up switching element at the predetermined on / off frequency at a time ratio of a time ratio control amount;
    When the duty ratio control amount is smaller than the first predetermined value, the first step-up switching is performed with the first step-down switching element turned on and the second step-down switching element turned off. An element and the second step-up switching element are turned on and off at a first on / off frequency determined based on the first time ratio control amount;
    Works like
    The control circuit, when the output voltage is lower than the input voltage,
    The first step-up switching element is turned on, the second step-up switching element is turned off, and the first step-down switching element and the second step-down switching element are turned on / off at the predetermined on / off frequency. Obtaining a time ratio of the second step-down switching element in a state of being based on the output voltage as a second time ratio control amount;
    When the second duty ratio control amount is equal to or greater than a second predetermined value, the second boosting switching element is turned on and the second boosting switching element is turned off. Turning on and off the first step-down switching element and the second step-down switching element at the predetermined on / off frequency at a time ratio of a time ratio control amount;
    When the second duty ratio control amount is smaller than the second predetermined value, the first boosting switching element is turned on and the second boosting switching element is turned off. Turning on and off the step-down switching element and the second step-down switching element at a second on / off frequency determined based on the second time ratio control amount;
    DC / DC converter that operates as follows.
  16. 前記制御回路は、前記時比率制御量がゼロであるときに、前記第１の昇圧用スイッチング素子と前記第１の降圧用スイッチング素子とを同時にオンにしてかつ前記第２の昇圧用スイッチング素子と前記第２の降圧用スイッチング素子とを同時にオフするように動作する、請求項１５に記載のＤＣ／ＤＣコンバータ。 The control circuit turns on the first step-up switching element and the first step-down switching element at the same time and the second step-up switching element when the time ratio control amount is zero. The DC / DC converter according to claim 15, wherein the DC / DC converter operates so as to simultaneously turn off the second step-down switching element.
  17. 前記第１のオンオフ周波数の最低値と前記第２のオンオフ周波数の最低値は可聴周波数帯域の最高周波数より高い、請求項１５に記載のＤＣ／ＤＣコンバータ。 The DC / DC converter according to claim 15, wherein a minimum value of the first on / off frequency and a minimum value of the second on / off frequency are higher than a maximum frequency of an audible frequency band.
  18. 前記制御回路は、
    　　　前記第１の昇圧用スイッチング素子と前記第２の昇圧用スイッチング素子とを同時にオフする期間を介して前記第１の昇圧用スイッチング素子と前記第２の昇圧用スイッチング素子とのオンオフを切り替え、
    　　　前記第１の降圧用スイッチング素子と前記第２の降圧用スイッチング素子とを同時にオフする期間を介して前記第１の降圧用スイッチング素子と前記第２の降圧用スイッチング素子とのオンオフを切り替える、
    ように動作する、請求項１５に記載のＤＣ／ＤＣコンバータ。     The control circuit includes:
    Switching on and off of the first boosting switching element and the second boosting switching element through a period of simultaneously turning off the first boosting switching element and the second boosting switching element;
    Switching on and off the first step-down switching element and the second step-down switching element through a period in which the first step-down switching element and the second step-down switching element are simultaneously turned off;
    16. The DC / DC converter according to claim 15, which operates as follows.
PCT/JP2014/003636 2013-07-17 2014-07-09 Dc/dc converter WO2015008456A1 (en)

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