JP3746226B2 - Control device for resonant DC-DC converter - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a resonant DC-DC converter in which a resonant element is inserted into a part of a converter to make a voltage waveform or a current waveform sinusoidal, thereby reducing the burden on a switching element (hereinafter simply referred to as a switch) during switching. In particular, the present invention relates to a control device for a resonance type DC-DC converter that can avoid the inability to control that occurs at a light load and can perform a stable operation.
[0002]
[Prior art]
In recent years, a resonant element is inserted into a part of a converter to perform resonant operation of voltage and current, and realize ZVS that turns on a switch at zero voltage and ZCS that turns on a switch at zero current. Resonance type DC-DC converters that reduce the noise by suppressing the time change rate and reduce the loss of the switch to increase the efficiency have been developed.
[0003]
FIG. 2 is a circuit diagram showing a configuration of a main circuit of a resonant DC-DC converter disclosed in, for example, Japanese Patent Laid-Open No. 7-222444. In the figure, one end of a parallel circuit formed by connecting a series connection circuit of switches S1 and S2 and a series connection circuit of switches S3 and S4 in parallel is connected to the positive electrode of the DC power supply 1, and the other end is a negative electrode of the DC power supply 1. It is connected to the. With these switches S1~S4 sac Chis switch S1 diode D1 to the connected antiparallel, the capacitance SC1 is connected in parallel as a lossless snubber, likewise with the diode D2 to the switch S2 is connected antiparallel The capacitance SC2 is connected in parallel. A diode D3 is connected in reverse parallel to the switch S3, and a diode D4 is connected in reverse parallel to the switch S4. Furthermore, snubber reactors 3 and 4 are connected in series to the interconnection point of the switches S3 and S4.
[0004]
Further, one end of the primary winding of the transformer 6 is connected to the interconnection point of the switches S1 and S2 via a series connection circuit of the resonant reactor 2 and the resonant capacitance 5, and the other end of the primary winding is the snubber reactor. Connected to 3 and 4 interconnection points. The secondary winding of the transformer 6 is connected to a full-wave rectifier circuit 7 formed by bridge-connecting diodes 7 a to 7 d, and a load is applied to the smoothing capacitance 9 between the output terminals of the full-wave rectifier circuit 7. 10 are connected in parallel.
[0005]
Since the control of the resonance type DC-DC converter configured as described above is described in Japanese Patent Laid-Open No. 7-222444, the outline of the operation related to the present invention will be described below.
The switches S1 and S4 are turned on with a phase difference α shifted, and the switches S2 and S3 are also turned on with a phase difference α shifted. Furthermore, the switch S1 and the switch S2, and the switch S3 and the switch S4 are alternately turned on with a phase difference of 180 °. Therefore, the power supplied to the load 10 can be controlled by changing the phase difference α between the switches S1 and S4 or the phase difference α between the switches S2 and S3. Incidentally, the output voltage becomes lower as the phase difference α is increased.
[0006]
By thus controlling the switches S1 to S4 on and off, a square wave voltage having the peak value of the voltage of the DC power supply 1 is supplied. This voltage snubber reactor 3 and 4, the resonance reactor 2, together with the applied as a sine wave voltage to the primary winding of the transformer 6 through the resonant circuit composed of a resonance capacitance 5, turns on the switch at zero voltage ZVS, zero by implementing ZCS turning on a current, to reduce the noise by suppressing the temporal change of the current, it is possible to reduce the loss of the switch achieve high efficiency. At this time, the capacitances SC1 and SC2 function as lossless snubbers, and the snubber reactors 3 and 4 also function as lossless snubbers.
[0007]
The voltage supplied to the primary winding of the transformer 6 is boosted and output from the secondary winding, and the pulsating current obtained by full-wave rectification by the smoothing reactor 8 is generated by the smoothing reactor and the smoothing capacitance 9. Smoothed and supplied to the load 10.
[0008]
Incidentally, the phase difference α between the switches S1 and S4, as shown in FIG. 3, proportional to a value obtained by subtracting the output voltage detection value V _o at the load from the output voltage command value V ^* to the load in the PI control unit 30, An integral operation was performed and determined according to the obtained value.
[0009]
[Problems to be solved by the invention]
The problems of the conventional resonance type DC-DC converter described above will be described with reference to FIG. A lossless snubber capacitance SC1 is connected in parallel to the first switch S1, and a lossless snubber capacitance SC2 is connected in parallel to the second switch S2. In order to prevent short circuit of these lossless snubber capacitances SC1 and SC2, in the first switch S1, the detected value of the element voltage in the on state is compared with the preset value of the on voltage by the comparator 11, a signal element voltage detection value Vs1 becomes "1" when lower than the oN voltage set value VsE to one input of the aND circuit 12, a signal which becomes "1" when the first switch S1 is turned on in addition as the other input of the aND circuit 12, the gate drive circuit 13 when the output of the aND circuit 12 is "1" was produced gate drive signal of the first switch S1. In the second switch S2, a gate drive signal is generated in the same manner as this.
[0010]
For this reason, since the current decreases as the load becomes lighter, the lossless snubber capacitances SC1 and SC2 are not discharged in time, and only one of the first switch S1 and the second switch S2 is switched. Sometimes. Then, when the load is further reduced, there may be a mode in which both the first switch S1 and the second switch S2 remain off.
[0011]
As described above, if one or both of the first switch S1 and the second switch S2 enters a mode in which switching is not performed and then the load becomes heavy, the control is disabled. Further, even when the DC voltage is lowered, the control may be impossible.
[0012]
The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a control device for a resonance type DC-DC converter that can be stably operated regardless of the weight of a load.
[0013]
[Means for Solving the Problems]
In the invention according to claim 1, the series connection circuit of the first and second switches and the series connection circuit of the third and fourth switches are connected in parallel, and one end of the parallel connection circuit is connected to the DC power supply. Connected to the positive electrode, connected to the negative electrode of the DC power supply, connected to the interconnection point of the first and second switches with one end of the primary winding of the transformer, and connected to the third and fourth switches. The other end of the primary winding is connected to the interconnection point, and a diode is connected in antiparallel to the first and second switches, and a capacitance is connected in parallel, and the third and fourth switches are connected in parallel, respectively. A diode is connected in reverse parallel, a first reactor and a capacitance are connected in series with the primary winding of the transformer, and a second is connected between the other end of the primary winding of the transformer and the third switch. React of 2 There are connected, said third reactor between the other end of the transformer primary winding and said fourth switch is connected to the first to third reactor and said capacitance form a resonant circuit In the control device for the resonance type DC-DC converter, when power is supplied to the load via the transformer, the voltage across the first and second switch elements is detected, and the detection value is set in advance. A difference between a voltage command value for the load and a voltage detection value of the load; and a first control unit that performs on / off control of the first to fourth switches by a phase difference control method on condition that the value is lower than a value. in less than a predetermined value, and, when the phase difference of the phase difference control reaches the lower limit of the allowable range, and second control means for forcibly controlling turning on the first and second switches, the voltage of the load Detected value and load Third control means for controlling all of the first to fourth switches to be off when the difference from the voltage command value to be performed is a predetermined value or more and the phase difference of the phase difference control reaches the upper limit of the allowable range. And .
[0014]
According to a second aspect of the present invention, in the control device for the resonant DC-DC converter according to the first aspect, an integral calculation is executed in proportion to the deviation between the voltage command value supplied to the load and the detected voltage value of the load. And a PI control unit for determining the phase difference according to the phase difference control method according to the output and controlling the first to fourth switches on and off, and the control is performed on condition that the detected value is lower than the set value. In this case, there is provided means for resetting the output of the PI control unit to zero when the first to fourth switches are forcibly turned on / off regardless of whether or not the operation is stopped.
[0015]
The invention according to claim 3 is the control apparatus for the resonance type DC-DC converter according to claim 1 or 2, wherein the detected voltage value of the load is higher than a predetermined value with respect to the voltage command value supplied to the load, and when the phase difference for phase difference control has reached the upper limit of the allowable range, characterized in that Ru comprises means for all the off-state of the first to fourth switches.
According to a fourth aspect of the present invention, in the control device for the resonance type DC-DC converter according to the first aspect, the first control means detects the element voltage value of the first or second switch. A detection unit; an on-voltage setting unit that sets an on-voltage of the first or second switch; an element voltage detection value detected by the element voltage detection unit; and the on-voltage set by the on-voltage setting unit A comparison unit that compares a set value and outputs a significant signal level when the element voltage detection value is smaller than the on-voltage set value; and an on signal of the first or second switch and the comparator And a first calculation unit that calculates a logical product with a significant signal level to be output.
According to a fifth aspect of the present invention, in the control device for the resonance type DC-DC converter according to the fourth aspect, the second control means calculates a difference between a voltage command value for the load and a detected voltage value of the load. A comparator that outputs a significant signal level when the difference is less than or equal to a predetermined value compared to a predetermined value; and a second arithmetic unit that calculates a logical product of the significant signal level and the phase difference minimum limit; , A third arithmetic unit that calculates a logical product of the ON signal of the first or second switch and the output of the second arithmetic unit, the output of the first arithmetic unit, and the output of the third arithmetic unit And a fourth arithmetic unit that calculates a logical sum of the two.
According to a sixth aspect of the present invention, in the control device for the resonance type DC-DC converter according to any one of the first, fourth, and fifth aspects, the third control means is a load voltage for detecting a voltage value of the load. The detection unit compares the difference between the load voltage detection value detected by the load voltage detection unit and the load voltage command value for the load, and outputs a significant signal level when the difference is equal to or greater than the predetermined value. A comparison unit; and a fifth calculation unit that calculates a negative product of the significant signal level and the maximum phase difference limit.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail based on preferred embodiments shown in the drawings. FIG. 1 is a circuit diagram showing a configuration of an embodiment of a control device for a resonant DC-DC converter according to the present invention. In the figure, the same reference numerals as those of the conventional apparatus shown in FIG. 4 denote the same elements.
[0017]
Here, the element voltage detection value Vs1 (or Vs2) when the first switch S1 (or the second switch S2) is in the on state and the on-voltage set value VsE are compared by the comparator 11, and Vs1 (or When Vs2) <VsE, a signal that is “1” is input as one input, and an ON signal that is “1” when the first switch S1 (or second switch S2) is turned on is the other input. An AND circuit 12 is provided.
[0018]
Moreover, compared with the command value V ^* and the load voltage detected value V _o of the load voltage, when the difference between the command value V ^* and the load voltage detected value V _o of the load voltage is less than a predetermined value [Delta] V1, i.e., V ^* The output signal of the comparator 14 which is “1” when −V _o ≦ ΔV1 is one input, and the phase difference α determined based on the output of the PI control unit 30 (see FIG. 3) is the lower limit of the allowable range. And an AND circuit 15 having a phase difference minimum limit signal that becomes “1” when the signal reaches the other input.
[0019]
Further, an AND circuit 16 having an ON signal that becomes “1” when the first switch S1 (or the second switch S2) is turned on as one input and the output signal of the AND circuit 15 as the other input, and AND An OR circuit 17 having the output of the circuit 12 as one input and the output of the AND circuit 16 as the other input; an AND circuit 18 having the output signal of the OR circuit 17 as one input and an output signal of the NAND circuit 20 described later as the other input; It has.
[0020]
Further, compares the command value V of the load voltage ^* and load voltage detection value V _o, when the load voltage detected value V _o is higher than a predetermined value ΔV2 than the command value V of the load voltage ^*, i.e., V _o -V ^* The output signal of the comparator 19 which becomes “1” when ≧ ΔV2 is one input, and the phase difference α determined based on the output of the PI control unit 30 (see FIG. 3) reaches the upper limit of the allowable range. The NAND circuit 20 has a phase difference maximum limit signal that is “1” as the other input, and the output signal of the NAND circuit 20 is added as the other input of the AND circuit 18 described above.
[0021]
In addition, an AND circuit 21 is provided which receives the output signal of the NAND circuit 20 as one input and the ON signal for turning on the third switch S3 (or the fourth switch S4) as the other input.
[0022]
When the output of the AND circuit 18 is “1”, the gate drive circuit 13 generates a gate drive signal for the first switch S1 (or the second switch S2), and the output of the AND circuit 21 is “1”. The gate drive circuit 22 generates a gate drive signal for the third switch S3 (or the fourth switch S4).
[0023]
In the above-described embodiment, for example, S1 (S2) is provided corresponding to the switch S1, and means that the same one is provided corresponding to the switch S2.
[0024]
The operation of the present embodiment configured as described above will be described below.
First, the gate drive circuit 13 shown in FIG. 1 generates a gate drive signal for the first switch S1, and the PI control unit 30 shown in FIG. 3 may be included in the gate drive circuit 13, or It may be provided separately. When the phase difference α of the PI control unit 30 becomes the minimum value corresponding to the maximum output voltage, the phase minimum limit signal applied to the AND circuit 15 is “1”, on the contrary, the output having the minimum phase difference α. It is assumed that the phase maximum limit signal applied to the AND circuit 20 becomes “1” when the maximum value corresponding to the voltage is reached.
[0025]
Here, the following conditions are defined.
(A) The phase difference minimum limit signal is a value corresponding to the minimum value.
(B) the relationship of ^V * -V _o ≦ [Delta] V1 between the command value ^{V *} and the load voltage detected value _{V o} of the load voltage.
(C) There is a relationship of Vs1 <VsE between the element voltage detection value Vs1 and the on-voltage setting value VsE when the first switch S1 is in the on state.
(D) There is a relationship of V _o −V ^* ≧ ΔV 2 between the command value V ^* of the load voltage and the load voltage detection value V _o .
(E) The phase difference maximum limit signal is a value corresponding to the maximum value.
[0026]
Now, when the condition (c) is satisfied among the conditions (a) to (d), the output signal of the comparator 11 is “1”, so that the ON signal of the first switch S1 is directly received from the AND circuit 12. It is output and added to the AND circuit 18 through the OR circuit 17. At this time, since the output signal of the NAND circuit 20 is “1”, the output of the AND circuit 18 is also “1”, and the gate drive circuit 13 generates a gate control signal for the first switch S 1. The control is executed in the normal mode described in No. 222444.
[0027]
Next, when the load is reduced and the conditions (a) and (b) are satisfied simultaneously, the output signal of the AND circuit 15 is “1”, so that the condition (c) is satisfied. Regardless, the ON signal of the first switch S 1 is output as it is from the AND circuit 16 and is applied to the AND circuit 18 via the OR circuit 17. At this time, since the output signal of the NAND circuit 20 is “1”, the output of the AND circuit 18 is also “1”, and the gate drive circuit 13 generates a gate control signal for the first switch S1, and in the forced drive mode. Control is executed.
[0028]
That is, the maximum load voltage command value is output even though the load voltage approaches the command value. When such a state persists, control in the normal mode is already disabled. At this time, an ON signal for the first switch S1 is applied to the gate drive circuit 13 through the AND circuit 16, the OR circuit 17 and the AND circuit 18 to control in the forced drive mode. At this time, the integral value of the PI control unit 30 shown in FIG. 3 is reset to zero to smoothly shift to the normal mode control.
[0029]
Next, when the conditions (d) and (e) are satisfied due to the lighter load, the output signal of the NAND circuit 20 becomes “0”, and the outputs of both the AND circuit 18 and the AND circuit 21 are output. “0” is set to stop all the ON / OFF operations of the switches S1 to S4.
[0030]
That is, even if the control command is reduced in a state where the load voltage command value is lower than the load voltage detection value, the control becomes impossible. At this time, all the switches S1 to S4 are turned off to automatically reduce the voltage. When the load voltage detection value falls below the load voltage command value, the output signal of the NAND circuit 20 returns to “1”, so that the control returns to the normal mode.
[0031]
The second switch S2 is provided with a circuit similar to that described above, and the ON signal of the fourth switch S4 is shifted by the phase difference α with respect to the first switch S1. The on signal of the second switch S2 is an inversion of the on signal of the first switch S1, and the on signal of the third switch S3 is an inversion of the on signal of the fourth switch S4.
[0032]
Thus, according to this embodiment, the resonant DC-DC converter can be stably operated regardless of the load weight.
[0033]
According to the above embodiment, each control means is constituted by a logic circuit. However, even if these functions are provided in a data processing apparatus such as a microcomputer, the same effects as described above can be obtained.
[0034]
【The invention's effect】
As is apparent from the above description, according to the present invention, it is possible to provide a control device for a resonant DC-DC converter that can be stably operated regardless of the load weight.
[Brief description of the drawings]
FIG. 1 is a circuit diagram showing a configuration of an embodiment of a control device for a resonant DC-DC converter according to the present invention.
FIG. 2 is a circuit diagram showing a configuration of a main circuit of a resonance type DC-DC converter to which the present invention is applied.
FIG. 3 is a diagram showing elements that generate a phase difference determination signal for phase difference control of the resonant DC-DC converter shown in FIG. 2;
4 is a circuit diagram showing a part of the control device for the resonance type DC-DC converter shown in FIG. 2;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 DC power supply 2 Resonant reactor 3, 4 Snubber reactor 5 Resonance capacitance 6 Transformer
10 loads 13, 22 Gate drive circuit 30 PI control units S1-S4 Switching elements D1-D4 Diodes SC1, SC2 Capacitances 11, 14, 19 Comparator 12 first operation unit (AND circuit)
15 Second arithmetic unit (AND circuit)
16 3rd operation part (AND circuit)
17 Fourth arithmetic unit (OR circuit)
18 AND circuit 20 5th arithmetic part (NAND circuit)
21 AND circuit

Claims (6)

The series connection circuit of the first and second switches and the series connection circuit of the third and fourth switches are connected in parallel, and one end of the parallel connection circuit is connected to the positive electrode of the DC power supply, and the other end is connected One end of the primary winding of the transformer is connected to the interconnection point of the first and second switches, and the primary winding is connected to the interconnection point of the third and fourth switches. The other end of the line is connected, a diode is connected in antiparallel to each of the first and second switches and a capacitance is connected in parallel, and a diode is connected in antiparallel to the third and fourth switches, respectively. A first reactor and a capacitance are connected in series with the primary winding of the transformer, and a second reactor is connected between the other end of the primary winding of the transformer and the third switch, Transformation Third reactor is connected, the first to third reactor and the capacitance and the resonant DC-DC converter to form a resonant circuit between the other end of the primary winding and said fourth switch In the control device of
In supplying electric power to the load through the transformer, the voltage between both ends of the elements of the first and second switches is detected, and the first to second are set on condition that the detected value is lower than a preset set value. 1st control means which carries out on / off control of 4 switches with a phase difference control system ,
When the difference between the voltage command value for the load and the voltage detection value of the load is less than a predetermined value and the phase difference of the phase difference control reaches the lower limit of the allowable range, the first and second switches are forced Second control means for controlling to be turned on automatically ,
When the difference between the detected voltage value of the load and the voltage command value for the load is equal to or greater than a predetermined value and the phase difference of the phase difference control reaches the upper limit of the allowable range, all the first to fourth switches are turned on. Third control means for controlling off;
A control apparatus for a resonance type DC-DC converter, comprising: Proportional and integral calculations are executed with respect to the deviation between the voltage command value supplied to the load and the voltage detection value of the load, and the phase difference according to the phase difference control method is determined according to the output to determine the first to fourth. on the switch, includes a PI controller for turning off control, the execution of the control in which the detection value is provided that is lower than the set value, regardless of the stop, forcing the first to fourth switches turn on, when the off control, the PI control unit resonant DC-DC converter control device according to claim 1, characterized in that Ru comprising means for resetting the output to zero. When the voltage detection value of the load is higher than a predetermined value with respect to the voltage command value of the voltage supplied to the load , and the phase difference for performing phase difference control has reached the upper limit of the allowable range, the first or control device for resonant DC-DC converter according to claim 1 or 2, characterized in that Ru comprising means for all turned off and the fourth switch. The first control means includes an element voltage detection unit that detects an element voltage value of the first or second switch, an on-voltage setting unit that sets an on-voltage of the first or second switch, It is significant when the element voltage detection value is smaller than the on-voltage setting value by comparing the element voltage detection value detected by the element voltage detection unit with the on-voltage setting value set by the on-voltage setting unit. A comparator that outputs a signal level; and a first calculator that calculates a logical product of an ON signal of the first or second switch and a significant signal level output from the comparator. The control device for the resonance type DC-DC converter according to claim 1. The second control means compares a difference between a voltage command value for the load and a detected voltage value of the load with a predetermined value, and outputs a significant signal level when the difference is less than or equal to the predetermined value. A second arithmetic unit that calculates a logical product of the significant signal level and the minimum phase difference limit, and calculates a logical product of the ON signal of the first or second switch and the output of the second arithmetic unit. 5. A fourth arithmetic unit that calculates a logical sum of an output of the first arithmetic unit and an output of the third arithmetic unit. 5. Of the described resonance type DC-DC converter Control device. The third control means compares a load voltage detection unit that detects a voltage value of the load with a difference between the load voltage detection value detected by the load voltage detection unit and the load voltage command value for the load. A comparator that outputs a significant signal level when the difference is greater than or equal to the predetermined value, and a fifth calculator that calculates a negative product of the significant signal level and the maximum phase difference limit. 6. The control device for a resonance type DC-DC converter according to claim 1, wherein the control device is a resonance type DC-DC converter.

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