JP6013696B2 - Power converter - Google Patents

Description

  The present invention relates to a power conversion device that charges a capacitive load.

  There exists a power supply control apparatus of patent document 1 as what charges a capacitive load using DC power supply. The power supply control device described in Patent Document 1 includes a main power storage device, a capacitive load connected between the power lines of the main power storage device, and a capacitive load between the power lines of the main power storage device via a bidirectional converter. And an auxiliary power storage device connected in parallel. Power transfer between the main power storage device and the auxiliary power storage device is performed using a bidirectional converter. Further, by supplying the power of the auxiliary power storage device to the capacitive load using the bidirectional converter, charging is performed until the voltage of the capacitive load becomes equal to the voltage of the main power storage device.

JP 2007-295699 A

  When the bidirectional converter in the power supply control device described in Patent Literature 1 is a current input type push-pull DCDC converter having a choke coil on the auxiliary battery, the charging to the capacitive load is performed by the current of the choke coil. This is done by repeating the increase and decrease. Further, the power supply control device described in Patent Document 1 is not provided with a limiting resistor or the like for preventing an inrush current from the viewpoint of cost reduction and miniaturization of the system.

  Here, the condition for reducing the current of the choke coil is that the voltage of the auxiliary storage battery is smaller than the value obtained by dividing the voltage of the capacitive load by the turn ratio of the coils constituting the bidirectional converter. Therefore, when the voltage of the capacitive load is small, such as at the start of charging, the choke coil current continues to increase. As a result, the DCDC converter may be deteriorated or damaged.

  The present invention has been made to solve the above-described problems, and a main object of the present invention is to provide a power conversion device capable of quickly charging a capacitive load while suppressing an excessive current in the circuit. Is to provide.

  The present invention is a power conversion device, which includes a DC power supply, a choke coil whose input end is connected to the positive electrode of the DC power supply, and a center tap, both ends of which are respectively connected via a first switching element and a second switching element. A first coil connected to a predetermined connection point, a second coil magnetically coupled to the first coil, a capacitive load connected to the second coil via a rectifier circuit, and a capacitance that is a voltage of the capacitive load A capacitive load voltage detecting means for detecting a load voltage, and a pulse generator for transmitting the first PWM signal and the second PWM signal having the same control period to each of the first switching element and the second switching element, The tap is connected to the negative electrode of the power source and the predetermined connection point is connected to the output end of the choke coil, or the center tap is connected to the output end of the choke coil and When the constant connection point is connected to the negative electrode of the power source and the capacitive load voltage is equal to or lower than the first predetermined value, the phase difference between the first PWM signal and the second PWM signal is half of the control period, and The duty values of the 1 PWM signal and the second PWM signal are set to the first mode in which both are equal values less than 0.5, and when the capacitive load voltage is larger than the first predetermined value, the first PWM signal and the second PWM signal The third mode is characterized in that the phase difference is half of the control period, and the duty values of the first PWM signal and the second PWM signal are both equal values larger than 0.5.

  The present invention is also a power conversion device, which includes a DC power source, a choke coil whose input terminal is connected to the positive electrode of the DC power source, and a center tap, and both ends of the first switching element and the second switching element, respectively. A first coil connected to a predetermined connection point via the second coil, a second coil magnetically coupled to the first coil, a capacitive load connected to the second coil via a rectifier circuit, and a voltage of the capacitive load A capacitive load voltage detecting means for detecting a certain capacitive load voltage; and a pulse generator for transmitting one of an ON signal and an OFF signal to each of the first switching element and the second switching element. Connected to the negative electrode of the DC power source and the predetermined connection point is connected to the output end of the choke coil, or the center tap is connected to the output end of the choke coil and the predetermined connection point Connected to the negative electrode of the DC power supply, and when the capacitive load voltage is equal to or lower than the first predetermined value, one of the first switching element and the second switching element is turned on and the other is turned off; The control for turning off both the switching element and the second switching element is a first mode that repeats alternately, and when the capacitive load voltage is larger than the first predetermined value, the first switching element and the second switching element The third mode is characterized in that the control for turning one on and the other OFF and the control for turning on both the first switching element and the second switching element are alternately repeated.

  In a current input push-pull DCDC converter having a choke coil on the power supply side with respect to the transformer, the first coil is short-circuited when both the first switching element and the second switching element are ON. The coil voltage is zero. Therefore, the input voltage itself, which is the voltage of the DC power supply, is applied to the choke coil, and the current increases linearly.

  In addition, when one of the first switching element and the second switching element is ON, the current flowing through the choke coil based on the input voltage, the capacitive load voltage that is the capacitive load voltage, and the coil turns ratio is It is determined whether to increase or decrease. That is, if the input voltage is larger than the value obtained by dividing the capacitive load voltage by the turns ratio, the voltage applied to the choke coil becomes a positive value, and the choke coil current increases. On the other hand, if the input voltage is smaller than the value obtained by dividing the capacitive load voltage by the turn ratio, the voltage applied to the choke coil becomes a negative value, and the current of the choke coil decreases.

  Further, when both the first switching element and the second switching element are OFF, the current flowing through the choke coil decreases.

  Here, when the capacitive load voltage is small, such as at the start of charging of the capacitive load, the input voltage is larger than the value obtained by dividing the capacitive load voltage by the turns ratio. For this reason, even when one of the first switching element and the second switching element is turned ON, the current flowing through the choke coil continues to increase. Therefore, in this case, the phase difference between the first PWM signal and the second PWM signal is half of the control period, and the duty values of the first PWM signal and the second PWM signal are both equal to less than 0.5. The first mode is controlled.

  Alternatively, the first switching element may alternately repeat the control of turning on one of the first switching element and the second switching element and turning off the other, and the control of turning off both the first switching element and the second switching element. Control the mode.

  By the control in the first mode, the state where one of the first switching element and the second switching element is ON and the state where both the first switching element and the second switching element are OFF are alternately repeated. It will be. Therefore, it is possible to provide time for both the first switching element and the second switching element to be OFF, and to reduce the current flowing through the choke coil during this period. Therefore, it can prevent that the electric current accumulate | stored in a choke coil continues increasing, and can suppress degradation and a failure of a DCDC converter as a result.

  On the other hand, when the capacitive load voltage increases, such as when charging of the capacitive load proceeds, the input voltage becomes smaller than the value obtained by dividing the capacitive load voltage by the turns ratio. For this reason, when one of the first switching element and the second switching element is turned on, the current flowing through the choke coil is reduced. Therefore, when the capacitive load voltage is larger than the first predetermined value, the phase difference between the first PWM signal and the second PWM signal is half of the control period, and the duty values of the first PWM signal and the second PWM signal are both The third mode is controlled to an equal value greater than 0.5.

  Alternatively, the third switching element alternately repeats the control of turning on one of the first switching element and the second switching element and turning off the other, and the control of turning on both the first switching element and the second switching element. Control the mode.

  By the control in the third mode, the state in which both the first switching element and the second switching element are ON, and the state in which one of the first switching element and the second switching element is ON are alternately repeated. Become. Therefore, the current flowing through the choke coil can be increased during the period when both the first switching element and the second switching element are ON, and during the period when either one of the first switching element or the second switching element is ON. By reducing the current flowing through the choke coil, the charged capacitive load can be quickly charged.

  The present invention is also a power conversion device, which includes a DC power source, a choke coil whose input terminal is connected to the positive electrode of the DC power source, and a center tap, and both ends of the first switching element and the second switching element, respectively. A first coil connected to a predetermined connection point via the second coil, a second coil magnetically coupled to the first coil, a capacitive load connected to the second coil via a rectifier circuit, and a voltage of the capacitive load A capacitive load voltage detecting means for detecting a certain capacitive load voltage; and a pulse generator for transmitting the first PWM signal and the second PWM signal having the same control period to each of the first switching element and the second switching element. The center tap is connected to the negative electrode of the power source and the predetermined connection point is connected to the output end of the choke coil, or the center tap is connected to the output end of the choke coil. And when the predetermined connection point is connected to the negative electrode of the power source and the capacitive load voltage is equal to or lower than the second predetermined value which is smaller than the first predetermined value, the first PWM signal and the second PWM signal are The phase difference is half of the control cycle, and the duty values of the first PWM signal and the second PWM signal are both equal to less than 0.5, and the capacitive load voltage is greater than the second predetermined value. When the phase difference between the first PWM signal and the second PWM signal is equal to or less than the first predetermined value, the phase difference between the first PWM signal and the second PWM signal is one cycle difference of the control period, and the first PWM signal and the second PWM signal are signals having the first duty value. And a signal having a second duty value different from the first duty value is alternately repeated every control cycle, and the sum of the first duty value and the second duty value is less than 1 and the signal of the first duty value is When the switch from OFF to ON and the timing when the second duty value signal switches from OFF to ON are in the second mode, which is one cycle difference of the control cycle, and the capacitive load voltage is greater than the first predetermined value In the third mode, the phase difference between the first PWM signal and the second PWM signal is half of the control period, and the duty values of the first PWM signal and the second PWM signal are both equal to greater than 0.5. It is characterized by.

  The present invention is also a power conversion device, which includes a DC power source, a choke coil whose input terminal is connected to the positive electrode of the DC power source, and a center tap, and both ends of the first switching element and the second switching element, respectively. A first coil connected to a predetermined connection point via the second coil, a second coil magnetically coupled to the first coil, a capacitive load connected to the second coil via a rectifier circuit, and a voltage of the capacitive load A capacitive load voltage detecting means for detecting a certain capacitive load voltage; and a pulse generator for transmitting one of an ON signal and an OFF signal to each of the first switching element and the second switching element. Connected to the negative electrode of the DC power source and the predetermined connection point is connected to the output end of the choke coil, or the center tap is connected to the output end of the choke coil and the predetermined connection point When the capacitive load voltage is connected to the negative electrode of the DC power source and the capacitive load voltage is less than or equal to a second predetermined value that is smaller than the first predetermined value, one of the first switching element and the second switching element is turned ON, The first mode in which the control to turn off the other and the control to turn off both the first switching element and the second switching element are set as a first mode, the capacitive load voltage is greater than the second predetermined value, and the first If the value is equal to or less than 1 predetermined value, the control for turning on both the first switching element and the second switching element, and the control for turning on one of the first switching element and the second switching element and turning off the other, The second mode in which the control to turn off both the first switching element and the second switching element is repeated in order, and when the capacitive load voltage is greater than the first predetermined value, A third mode in which one of the switching element and the second switching element is turned on and the other is turned off and the control of turning on both the first switching element and the second switching element are alternately set to a third mode. It is characterized by.

  When the capacitive load voltage is equal to or lower than the first predetermined value, the capacitive load voltage increases due to charging by the control in the first mode. When the value obtained by dividing the capacitive load voltage by the coil turns ratio is larger than the input voltage, the current flowing through the choke coil does not increase, and the value obtained by dividing the capacitive load voltage by the coil turns ratio is smaller than the input voltage. However, the amount of increase in the current flowing through the choke coil decreases, and the charging speed decreases.

  Therefore, a second predetermined value smaller than the first predetermined value is set as the threshold value of the capacitive load voltage. When the capacitive load voltage is greater than the second predetermined value and less than or equal to the first predetermined value, the phase difference between the first PWM signal and the second PWM signal is one cycle difference of the control cycle, In the first PWM signal and the second PWM signal, a first duty value and a second duty value different from the first duty value are alternately repeated every control cycle, and the sum of the first duty value and the second duty value is less than 1. And the second mode control in which the timing at which the first duty value signal is switched from OFF to ON and the timing at which the second duty value signal is switched from OFF to ON is one cycle difference of the control cycle. Assumed to be performed.

  Alternatively, control for turning on both the first switching element and the second switching element, control for turning on one of the first switching element and the second switching element, and turning off the other, and the first switching element and the second switching element. It is assumed that the control in the second mode is performed by repeating the control for turning off both the two switching elements in order.

  By the control of the second mode, a period in which both the first switching element and the second switching element are ON, a period in which one of the first switching element and the second switching element is ON, and the first switching element, A period in which both the second switching elements are OFF can be provided.

  That is, first, the first switching element and the second switching element are simultaneously turned ON, and the current flowing through the choke coil increases. Next, the ON state of one of the first switching element and the second switching element is continued, and the other is turned OFF. By doing this, if the input voltage is higher than the value obtained by dividing the capacitive load voltage by the turns ratio, the current flowing through the choke coil increases, and if the input voltage is lower than the value obtained by dividing the capacitive load voltage by the turns ratio, The current flowing through the choke coil is reduced. During this period, the capacitive load is charged. Thereafter, both the first switching element and the second switching element are turned OFF, and the current flowing through the choke coil decreases.

  Therefore, when charging to the capacitive load proceeds and the capacitive load voltage becomes equal to or higher than the second predetermined value, the current flowing through the choke coil can be increased, and the charging speed to the capacitive load can be improved. . Also in the second mode, it is possible to prevent the current flowing through the choke coil from continuing to increase by providing a period in which both the first switching element and the second switching element are OFF.

It is a circuit diagram of the power converter concerning a 1st embodiment. (A) is a figure which shows the electric current which flows into a power converter device when both a 1st switching element and a 2nd switching element are set to ON, (b) is the equivalent circuit. (A) is a figure which shows the electric current which flows into a power converter device when a 1st switching element is ON and a 2nd switching element is OFF, (b) is the equivalent circuit. It is a flowchart which shows a series of processes of 1st Embodiment. (A) is a PWM signal in the first mode, (b) is a PWM signal in the second mode, and (c) is a PWM signal in the third mode. It is a circuit diagram of the power converter device which concerns on 3rd Embodiment. It is a figure explaining the relationship between the 1st permissible maximum value and Duty value in the 1st mode in a 4th embodiment. It is a figure explaining the 2nd allowable maximum value and Duty value in the 2nd mode in a 4th embodiment. It is a figure explaining the control signal in 5th Embodiment, (a) is a control signal in 1st mode, (b) is a control signal in 2nd mode, (c) is in 3rd mode. Control signal. It is a figure explaining the control signal in 6th Embodiment, (a) is a control signal in 1st mode, (b) is a control signal in 2nd mode, (c) is in 3rd mode. Control signal. It is a circuit diagram of the power converter device which concerns on 7th Embodiment. It is a block diagram which shows the process which a pulse generation part performs in the power converter device which concerns on 7th Embodiment. It is a figure which shows the reactor current in 2nd mode in 7th Embodiment.

  Hereinafter, each embodiment will be described with reference to the drawings. In the following embodiments, parts that are the same or equivalent to each other are denoted by the same reference numerals in the drawings, and the description of the same reference numerals is used.

<First Embodiment>
The power conversion device according to the present embodiment is mounted on a hybrid car including a secondary battery such as a lead battery having a nominal voltage of 12V and a high voltage storage battery such as a lithium ion battery having a nominal voltage of several hundred volts. .

  FIG. 1 is a circuit diagram of the power conversion device according to the present embodiment. The power conversion device according to the present embodiment includes a DCDC converter 10, a secondary battery 20 that is a DC power source connected to an input end of the DCDC converter 10, and a capacitive load 30 ( Smoothing capacitor) and connection terminals 40 a and 40 b provided at the output end of the DCDC converter 10. The electric power stored in the secondary battery 20 is transformed by the DCDC converter 10 and output from the connection terminals 40a and 40b. The electric power input from the connection terminals 40 a and 40 b is transformed by the DCDC converter 10 and input to the secondary battery 20. A high voltage storage battery, an electric load, a generator, etc. (not shown) are connected to the connection terminals 40a and 40b, and power can be exchanged with the secondary battery 20.

  The DCDC converter 10 includes a choke coil 11, a transformer Tr, a bridge circuit 14, a first switching element Q1, and a second switching element Q2.

  The transformer Tr is composed of a first coil L1 and a second coil L2 that are magnetically coupled to each other, and the first coil L1 has a center tap 13. The number of turns of the second coil L2 is N / 2 times the number of turns of the first coil L1. That is, the number of turns of the second coil L2 is N times the number of turns from one end of the first coil L1 to the center tap 13. The second coil L2 is connected to the capacitive load 30 via the bridge circuit 14 and the output terminal of the DCDC converter 10.

  The bridge circuit 14 includes a switching element and a diode, and functions as a rectifier circuit when supplying power from the first coil L1 side to the second coil L2 side, and from the second coil L2 side to the first coil L1 side. When power is supplied to the power supply, it functions as a switching circuit.

  The first switching element Q1 and the second switching element Q2 are MOSFETs, and both ends of the first coil L1 are connected to the source of the first switching element Q1 and the source of the second switching element Q2, respectively. On the other hand, the drain of the first switching element Q1 and the drain of the second switching element Q2 are both connected to the predetermined connection point 12. The output terminal of the choke coil 11 is connected to the predetermined connection point 12, and the input terminal of the choke coil 11 is connected to the positive electrode of the secondary battery 20 through the input terminal of the DCDC converter 10. Further, the center tap 13 of the first coil L <b> 1 is connected to the negative electrode of the secondary battery 20 through the input end of the DCDC converter 10. The first switching element Q1 and the second switching element Q2 each have a first parasitic diode D1 and a second parasitic diode D2 that are connected in parallel in opposite directions.

  The DCDC converter 10 includes an input voltage detection unit 15, a capacitive load voltage detection unit 16, a pulse generation unit 17, and a drive circuit 18. The input voltage detection unit 15 detects an input voltage Vin that is a voltage input from the secondary battery 20 to the choke coil 11. The capacitive load voltage detection means 16 detects a capacitive load voltage Vc that is the voltage of the capacitive load 30.

  The input voltage Vin detected by the input voltage detector 15 and the capacitive load voltage Vc detected by the capacitive load voltage detector 16 are input to the pulse generator 17. Based on the input voltage Vin and capacitive load voltage Vc that are input, the pulse generator 17 includes a first PWM signal that is a drive signal for the first switching element Q1 and a second PWM signal that is a drive signal for the second switching element Q2. Is transmitted to the drive circuit 18.

  The drive circuit 18 drives the first switching element Q1 based on the first PWM signal received from the pulse generator 17, and drives the second switching element Q2 based on the second PWM signal.

  In the present embodiment, the capacity load 30 is charged with the electric power stored in the secondary battery 20. At this time, the DCDC converter 10 functions as a current input type push-pull DCDC converter. Charging is started when a charging start command is generated in the ECU mounted on the vehicle when the vehicle is powered on. On the other hand, the charging is performed until the voltage close to the voltage of the high voltage storage battery is set as the target voltage and the capacity load voltage Vc reaches the target voltage. In addition, the value memorize | stored in the memory in ECU may be used for a target voltage, and a target voltage may be calculated based on the measured value of the voltage of a high voltage storage battery. It is also possible to adopt means for acquiring the charge start command and the target voltage value from the outside of the vehicle.

  FIG. 2A shows a path of a current flowing through the circuit when both the first switching element Q1 and the second switching element Q2 are turned on. FIG. 2B shows an equivalent circuit when both the first switching element Q1 and the second switching element Q2 are turned on. In this state, since the first coil L1 is in a short circuit state, the voltage of the first coil L1 is zero. Therefore, the input voltage Vin is applied to the choke coil 11.

  The increase amount ΔI (A / s) per unit time of the current flowing through the choke coil 11 is expressed by the following equation (3), where L (H) is the self-inductance of the choke coil 11.

ΔI = Vin / L (3)
That is, the choke coil current increases linearly. Note that a period during which both the first switching element Q1 and the second switching element Q2 are turned on is a period α.

  FIG. 3A shows a path of a current flowing through the circuit when the first switching element Q1 is turned on and the second switching element Q2 is turned off. FIG. 3B shows an equivalent circuit when the first switching element Q1 is ON and the second switching element Q2 is OFF. Here, it is assumed that the DCDC converter 10 is in a steady state and the output voltage Vout, which is a voltage output from the second coil L2 of the transformer Tr, is equal to the capacitive load voltage Vc. In this state, whether the voltage applied to the choke coil 11 becomes a positive value or a negative value depending on the magnitude relationship between the input voltage Vin and the value obtained by dividing the capacitive load voltage Vc by the turn ratio N. It is determined. If the voltage applied to the choke coil 11 has a positive value, the choke coil current increases. If the voltage applied to the choke coil 11 has a negative value, the choke coil current decreases. Note that, when the first switching element Q1 is OFF and the second switching element Q2 is ON, an equivalent circuit similar to FIG. 3B is obtained. Note that a period during which one of the first switching element Q1 and the second switching element Q2 is turned ON is defined as a period β.

  The increase / decrease amount ΔI (A / s) per unit time of the choke coil current is expressed by the following equation (4).

ΔI = (Vin−Vc / N) / L (4)
That is, if the input voltage Vin is larger than the value obtained by dividing the capacitive load voltage Vc by the turn ratio N, ΔI takes a positive value, and the choke coil current increases. On the other hand, if the input voltage Vin is smaller than the value obtained by dividing the capacitive load voltage Vc by the turn ratio N, ΔI takes a negative value, so that the choke coil current decreases. This is because, when the capacitive load voltage Vc is small, such as at the start of charging of the capacitive load 30, the capacitive load 30 is charged even during the period β, whereas the capacitive load 30 is being charged. If the capacitive load voltage Vc increases, the choke coil current decreases, which means that the charging rate in the period β decreases.

  When both the first switching element Q1 and the second switching element Q2 are turned off, a counter electromotive voltage having a polarity opposite to that of the input voltage Vin is generated in the choke coil 11, and the choke coil current is reduced. Note that a period during which both the first switching element Q1 and the second switching element Q2 are OFF is defined as a period γ.

  The control of the first switching element Q1 and the second switching element Q2 is performed in the first mode, the second mode, and the third mode in which the length of the control cycle is Ts. In the first mode, the second mode, and the third mode, the length of the ON period of the first switching element Q1 and the length of the ON period of the second switching element Q2 are respectively set to the length Ts of the control cycle. Duty values that are values divided by are different. In the first mode, the second mode, and the third mode, the magnitude relationship between the value of the capacitive load voltage Vc and the second predetermined value V2 that is smaller than the first predetermined value V1 and the first predetermined value V1. Is switched based on

  When the capacitive load voltage Vc is less than or equal to the second predetermined value V2, control is performed in the first mode, and when the capacitive load voltage Vc is greater than the second predetermined value V2 and less than or equal to the first predetermined value V1. When the control is performed in the second mode and the capacitive load voltage Vc is larger than the first predetermined value V1, the control is performed in the third mode.

  Here, the second predetermined value V2 is set so that the current flowing through the choke coil 11 increases in the period β. That is, ΔI expressed by the above equation (4) is set to be a positive value. On the other hand, the first predetermined value V1 is set so that the current flowing through the choke coil 11 decreases during the period β. That is, ΔI expressed by the above equation (4) is set to a negative value.

  At this time, a series of processes executed by the pulse generator 17 will be described with reference to the flowchart of FIG. The control according to the flowchart of FIG. 4 is executed at a predetermined control cycle.

  First, it is determined whether an activation request has been acquired (S101). The start request command signal is transmitted from, for example, an ECU or the like, which is a host control device. When the activation request has not been acquired (S101: NO), the standby state is continued without performing a series of controls.

  If the activation request is acquired (S101: YES), the capacitive load voltage Vc is acquired (S102), and it is determined whether or not the capacitive load voltage Vc is equal to or less than the second predetermined value V2 (S103). If the capacitive load voltage Vc is less than or equal to the second predetermined value V2 (S103: YES), control in the first mode is performed (S104). If the capacitive load voltage Vc is not less than or equal to the second predetermined value V2 (S103: NO), it is subsequently determined whether or not the capacitive load voltage Vc is less than or equal to the first predetermined value V1 (S105). If the capacitive load voltage Vc is less than or equal to the first predetermined value V1 (S105: YES), control is performed in the second mode (S106). On the other hand, if the capacitive load voltage Vc is not less than or equal to the first predetermined value V1 (S105: NO), control is performed in the third mode (S107).

  After the control in any one of the first mode, the second mode, and the third mode is performed for a predetermined time, the control end determination is performed (S108). In the process of S108, for example, the capacitive load voltage Vc may be acquired again, and it may be determined whether or not the capacitive load voltage Vc is equal to or higher than a predetermined upper limit value. The determination as to whether or not the capacitive load voltage Vc has become equal to or greater than a predetermined upper limit value may be made after a negative determination is made in S105. If it is determined that the control is to be terminated (S108: YES), the process is terminated until a start request is made. If it is not determined to end the control (S108: NO), it is determined whether an end request has been acquired (S109). This end request command signal is transmitted from a host control device such as an ECU. If an end request is acquired (S109: YES), a series of processing is ended and the process waits until an activation request is made. If the end request is not acquired (S109: NO), the processing after S102 is executed again.

  In the flowchart of FIG. 4, only control related to charging control to the capacitive load 30 is shown, but the DCDC converter 10 performs power conversion other than charging control to the capacitive load 30. For example, there is a control in which the power supplied via the connection terminals 40a and 40b is stepped down and the secondary battery 20 is charged. Since the control is a well-known control, description thereof is omitted.

  FIG. 5A shows a PWM signal when control is performed in the first mode. In the first mode, the phase difference between the first PWM signal and the second PWM signal is a Ts / 2 difference. Both the first PWM signal and the second PWM signal form one control cycle by an ON period having a length T1 and an OFF period having a length (Ts−T1), and the length T1 of the ON period is less than Ts / 2. It is. That is, the duty value indicated by T1 / Ts is less than 0.5. Therefore, in the first mode, the period β having the length T1 and the period γ having the length (Ts / 2−T1) are alternately repeated.

  In the first mode, the capacitive load 30 is charged in the period β, and the choke coil current increases. On the other hand, in the period γ, the choke coil current increased in the period β is consumed in the circuit. The length T1 of the ON period is set so that the choke coil current becomes zero in the period γ.

  FIG. 5B shows a PWM signal when performing control in the second mode. In the second mode, the phase difference between the first PWM signal and the second PWM signal is a Ts difference. Both the first PWM signal and the second PWM signal start from the ON period of length T2h, start from the OFF period of length (Ts−T2h), and start from the ON period of length T2l. The second control cycle that ends in the OFF period of the length (Ts−T2l) is alternately repeated. That is, the timing at which the ON period of the length T2h of the first PWM signal is started and the timing at which the ON period of the length T2l of the second PWM signal is started are the same timing, and the ON of the length T2l of the first PWM signal The timing when the period is started and the timing when the ON period of the length T2h of the second PWM signal is started are the same timing. Furthermore, the sum of the value of T2h / Ts, which is the first duty value in the first control cycle, and T21 / Ts, which is the second duty value in the second control cycle, is less than 1.

  Therefore, in the second mode, a period α having a length of T2l, a period β having a length of (T2h−T2l), and a period γ having a length of (Ts−T2h) are repeated in one control cycle. Become.

  In the second mode, the choke coil current increases in the period α, and the choke coil current increases in the period β based on the magnitude relationship between the input voltage Vin and the value obtained by dividing the capacitive load voltage Vc by the turn ratio N. Or decrease. In the period γ, the choke coil current increased in the period α and the period β or the choke coil current that has not become zero in the period β is consumed in the circuit. Note that the lengths T2h and T2l of the ON period are set so that the choke coil current becomes zero in the period γ.

  FIG. 5C shows a PWM signal when performing control in the third mode. In the third mode, the phase difference between the first PWM signal and the second PWM signal is a Ts / 2 difference. Both the first PWM signal and the second PWM signal have one control cycle composed of an ON period having a length T3 and an OFF period having a length (Ts−T3). It is larger than the half length Ts / 2. That is, the duty value indicated by T3 / Ts is greater than 0.5. Therefore, in the third mode, the period α whose length is (T3−Ts / 2) and the period β whose length is (Ts−T3) are alternately repeated.

  In the third mode, the choke coil current increases in the period α. On the other hand, in the period β, the choke coil current is decreased, and charging of the capacitive load 30 is performed as the choke coil current decreases. Note that the length T3 of the ON period is set so that the increase amount of the choke coil current in the period α is equal to the decrease amount of the choke coil current in the period β.

  The duty value in the third mode, which is a value larger than 0.5, is changed as the charging of the capacitive load 30 proceeds. Further, when the duty 3 is switched from the second mode to the third mode, the duty 3 is set to a duty 0 that is an initial value larger than 0.5.

  In the third mode, the amount of increase in current during the period α is equal to the amount of decrease in current during the period β. Therefore, a value obtained by multiplying the amount of increase in current per unit time in the period α expressed by the above expression (3) by the length of the period α (T3−Ts / 2), and the expression expressed by the above expression (4). Since the total value of the increase amount of the current per unit time in the period β and the value obtained by multiplying the length of the period β (Ts−T3) becomes zero, the following expression (5) is obtained. In this case, since it is assumed that the capacitive load voltage Vc and the output voltage Vout are different, the capacitive load voltage Vc is replaced with the output voltage Vout in the above equation (4).

(T3−Ts / 2) × Vin + (Ts−T3) × (Vin−Vout / N) = 0 (5)
Here, when the above equation (5) is modified using the duty 3 of the PWM signal in the third mode, the output voltage Vout of the transformer Tr is represented by the following equation (6).

Vout = N × Vin / (2 × (1-Duty3)) (6)
Here, when switching from the second mode to the third mode, if there is a divergence between the output voltage Vout and the capacitive load voltage Vc, assuming that the circuit is an ideal circuit without resistance, An inrush current of infinite magnitude will be generated. Even if the circuit is not an ideal circuit, an inrush current may occur.

  Therefore, when the first predetermined value V1, which is a condition for switching from the second mode to the third mode, is switched from the second mode to the third mode, the first predetermined value V1, which is the threshold value of the capacitive load voltage Vc, It sets by following Formula (1) using Duty0 mentioned above so that the output voltage Vout may become equal.

V1 = N × Vin / (2 × (1-Duty0)) (1)
That is, the first predetermined value V1, which is the value of the capacitive load voltage Vc when switching from the second mode to the third mode, is made equal to the output voltage Vout of the transformer Tr.

  Here, as described above, the value of Duty3 that is the duty value in the third mode is changed as the charging of the capacitive load 30 proceeds. Therefore, if there is a divergence between the output voltage Vout and the capacitive load voltage Vc due to the change in the value of Duty3, assuming that the circuit is an ideal circuit without resistance, an infinite magnitude is entered. An electric current will be generated. Even if the circuit is not an ideal circuit, an inrush current may occur. Therefore, the above expression (6) is modified to replace the output voltage Vout with the capacitive load voltage Vc. Then, the value of Duty3 is set by the following equation (2) obtained.

Duty3 = 1−N × Vin / (2 × Vc) (2)
That is, Duty3 is set so that the capacitive load voltage Vc and the output voltage Vout of the transformer Tr are equal.

  Note that not all of the first to third modes are performed depending on the initial value and the target value of the capacitive load voltage Vc. That is, only when the initial value of the capacitive load voltage Vc is equal to or lower than the second predetermined value V2 and the target value of the capacitive load voltage Vc is larger than the first predetermined value V1, the charging is performed in the first to third modes. Done. On the other hand, when the initial value of the capacitive load voltage Vc is not less than or equal to the second predetermined value V2, and / or when the target value of the capacitive load voltage Vc is less than or equal to the first predetermined value V1, the following control is performed.

  When the target value of the capacitive load voltage Vc is equal to or lower than the second predetermined value V2, charging is started in the first mode, and the charging is terminated in the first mode without shifting to the second mode and the third mode. To do.

  When the initial value of the capacitive load voltage Vc is less than or equal to the second predetermined value and the target value of the capacitive load voltage Vc is greater than the second predetermined value V2 and less than or equal to the first predetermined value V1, the first mode The charging is started, and the charging is terminated in the second mode without shifting to the third mode.

  The initial value of the capacitive load voltage Vc is greater than the second predetermined value V2 and not greater than the first predetermined value V1, and the target value of the capacitive load voltage Vc is greater than the second predetermined value V2 and not greater than the first predetermined value V1. If not, charging is started in the second mode without passing through the first mode, and charging is terminated in the second mode without shifting to the third mode.

  When the initial value of the capacitive load voltage Vc is greater than the second predetermined value V2 and equal to or less than the first predetermined value V1, and the target value of the capacitive load voltage Vc is greater than the first predetermined value V1, the first mode Without charging, charging is started in the second mode, and charging is ended in the third mode.

  When the initial value of the capacitive load voltage Vc is larger than the first predetermined value V1, charging is started in the third mode without passing through the first mode and the second mode, and charging is performed in the third mode. finish.

  With this configuration, the present embodiment has the following effects.

  -When the capacitive load voltage Vc is small, such as when charging of the capacitive load 30 is started, by performing the control in the first mode, one of the first switching element Q1 and the second switching element Q2 is OFF. A period β and a period γ in which both the first switching element Q1 and the second switching element Q2 are OFF are provided. Therefore, the current of the choke coil 11 increased in the period β can be decreased in the period γ. Therefore, it can prevent that the electric current which flows into the choke coil 11 continues increasing, and can suppress the deterioration and failure of the DCDC converter 10 by extension.

  When the capacitive load voltage Vc is greater than the second predetermined value V2, by performing the second mode control, a period α in which both the first switching element Q1 and the second switching element Q2 are ON, and the first A period β in which one of the switching element Q1 and the second switching element Q2 is OFF and a period γ in which both the first switching element Q1 and the second switching element Q2 are OFF are provided. Therefore, the current flowing through the choke coil 11 in the period α can be increased, and the charging speed to the capacitive load 30 can be improved. In addition, the current of the choke coil 11 can be reduced in the period γ. Therefore, it can prevent that the electric current which flows into the choke coil 11 continues increasing, and can suppress the deterioration and failure of the DCDC converter 10 by extension.

  When the capacitive load voltage Vc becomes larger than the first predetermined value V1, such as when charging to the capacitive load 30 proceeds, the first switching element Q1 and the second switching are performed by performing the control in the third mode. A period α in which both the elements Q2 are ON and a period β in which one of the first switching element Q1 and the second switching element Q2 is ON are provided. Therefore, it is possible to increase the current flowing through the choke coil 11 during the period α, and to reduce the current flowing through the choke coil 11 during the period β to quickly charge the capacitive load 30 that has been charged. it can.

  If the difference between the output voltage Vout of the transformer Tr and the capacitive load voltage Vc occurs when the capacitive load voltage Vc exceeds the first predetermined value V1, the circuit is an ideal circuit having no resistance value. Assuming that, inrush current may occur, which increases the possibility of circuit destruction. In the present embodiment, since the first predetermined value V1 is set so that the output voltage Vout becomes equal to the capacitive load voltage Vc when the capacitive load voltage Vc exceeds the first predetermined value V1, the output of the transformer Tr There is no potential difference between the voltage Vout and the capacitive load voltage Vc, thereby suppressing the occurrence of inrush current.

  When performing control in the third mode, if there is a difference between the output voltage Vout of the transformer Tr and the capacitive load voltage Vc, it is assumed that the circuit is an ideal circuit having no resistance value. This may increase the possibility of circuit destruction. In the present embodiment, when the control is performed in the third mode, the duty 3 is set so that the output voltage Vout becomes equal to the capacitive load voltage Vc, and therefore, between the output voltage Vout of the transformer Tr and the capacitive load voltage Vc. Thus, no potential difference is generated, so that inrush current can be suppressed.

Second Embodiment
The power conversion device according to the present embodiment is a circuit similar to the power conversion device according to the first embodiment, and the control method thereof is different. In the power conversion device according to the present embodiment, the control in the second mode is not performed, charging is performed until the capacitive load voltage Vc reaches the first predetermined value V1 in the first mode, and the capacitive load voltage Vc is the first predetermined value. If it becomes larger than value V1, it will charge in 3rd mode. Here, the first predetermined value V1 and the value of Duty3, which is the duty value in the third mode, are set in the same manner as in the first embodiment.

  Note that both the first mode and the third mode are not performed depending on the initial value and the target value of the capacitive load voltage Vc. That is, charging is performed in the first mode and the third mode only when the initial value of the capacitive load voltage Vc is equal to or less than the first predetermined value V1 and the target value of the capacitive load voltage Vc is greater than the first predetermined value V1. Is done. On the other hand, when the initial value of the capacitive load voltage Vc is larger than the first predetermined value V1, or when the target value of the capacitive load voltage Vc is equal to or lower than the first predetermined value V1, the following control is performed.

  When the initial value of the capacitive load voltage Vc is larger than the first predetermined value V1, charging is started in the third mode without passing through the first mode, and charging is ended in the third mode.

  When the target value of the capacitive load voltage Vc is equal to or less than the first predetermined value V1, charging is started in the first mode, and the charging is terminated in the first mode without shifting to the third mode.

  With the configuration described above, the power conversion device according to the present embodiment has an effect similar to that of the power conversion device according to the first embodiment.

<Third Embodiment>
FIG. 6 shows a circuit diagram of the power conversion device according to the third embodiment. The power conversion device according to the present embodiment is similar to the power conversion device according to the first embodiment. The DCDC converter 10, the secondary battery 20 that is a DC power source connected to the input terminal of the DCDC converter 10, and the DCDC converter 10 includes a capacitive load 30 (smoothing capacitor) connected in parallel to the output terminal of 10 and connection terminals 40 a and 40 b provided at the output terminal of the DCDC converter 10.

  The DCDC converter 10 includes a choke coil 11, a transformer Tr, a bridge circuit 14, a first switching element Q1, and a second switching element Q2.

  The transformer Tr is composed of a first coil L1 and a second coil L2 that are magnetically coupled to each other, and the first coil L1 has a center tap 13. The second coil L2 is connected to the capacitive load 30 via the bridge circuit 14 and the output terminal of the DCDC converter 10.

  The first switching element Q1 and the second switching element Q2 are MOSFETs, and both ends of the first coil L1 are connected to the drain of the first switching element Q1 and the drain of the second switching element Q2, respectively. On the other hand, the source of the first switching element Q1 and the source of the second switching element Q2 are both connected to the predetermined connection point 12. The predetermined connection point 12 is connected to the negative electrode of the secondary battery 20 via the input end of the DCDC converter 10. The input end of the choke coil 11 is connected to the positive electrode of the secondary battery 20 via the input end of the DCDC converter 10, and the output end of the choke coil 11 is connected to the center tap 13. The first switching element Q1 and the second switching element Q2 each have a first parasitic diode D1 and a second parasitic diode D2 that are connected in parallel in opposite directions.

  In the power conversion device according to the present embodiment, the same control as the control of the power conversion device according to the first embodiment or the same control as the control of the power conversion device according to the second embodiment is performed. And there exists an effect similar to the power converter device which concerns on 1st Embodiment, or the power converter device which concerns on 2nd Embodiment.

<Fourth embodiment>
The power conversion device according to the present embodiment uses a circuit similar to that of the power conversion device according to the first embodiment or the third embodiment, and the duty value setting method in the first mode and the duty value in the second mode. The setting method is more concrete. In the present embodiment, the first allowable maximum value Imax1 is provided for the first mode as the maximum value that can be tolerated for the choke coil current with little risk of deterioration of the DCDC converter 10, and the second for the second mode. An allowable maximum value Imax2 is provided. The first allowable maximum value Imax1 and the second allowable maximum value Imax2 are stored in a memory (not shown) or the like.

  FIG. 7 shows the relationship between the duty value and the first allowable maximum value Imax1 in the first mode. A value obtained by multiplying the increase amount ΔI of current per unit time in the period β expressed by the above formula (4) by the product of the length T1 of the period β, that is, the control period Ts and the duty value Duty1. However, Duty1 is set by the following equation (7) so that the first allowable maximum value Imax1 is obtained. At this time, in the period β, the input voltage Vin, the capacitive load voltage Vc, and L that is the self-inductance of the choke coil are considered to be constant.

Duty1 = Imax1 × L / {Ts (Vin−Vc / N)} (7)
Accordingly, after either one of the first switching element Q1 and the second switching element Q2 is turned ON, the choke coil current becomes the first allowable maximum value Imax1 after the length T1 of the period β has elapsed.

  FIG. 8 shows the duty value and the second allowable maximum value Imax2 in the second mode. In the second mode, the duty value in the period α is set to Duty2l so that the sum of the increase amount of the choke coil current in the period α and the increase amount of the choke coil current in the period β becomes the second allowable maximum value Imax2. , Duty2h which is a Duty value corresponding to the sum of the period α and the period β is set.

  The increase amount of the choke coil current in the period α is a value obtained by multiplying the increase amount ΔI of the current per unit time in the period α expressed by the above equation (3) by the length T2l of the period α. At this time, the length T2l of the period α is expressed as a product of Ts that is a control cycle and Duty2l that is a duty value. Therefore, Duty2l is set by the following equation (8) so that the increase amount of the choke coil current in the period α is smaller than the second allowable maximum value Imax2.

Duty2l <Imax2 × L / (Ts × Vin) (8)
On the other hand, the increase amount of the choke coil current in the period β is a value obtained by multiplying the increase amount ΔI of the current per unit time in the period β expressed by the above equation (4) by the length of the period β (T2h−T2l). It becomes. At this time, the length T2h of the period β is expressed as a product of Ts that is the control cycle and the difference between the duty values (Duty2h−Duty2l). Then, Duty2h is set by the following equation (9) so that the total value of the increase amount of the choke coil current in the period α and the increase amount of the choke coil current in the period β becomes the second allowable maximum value Imax2. . At this time, Duty2l set by the above equation (8) is used. Note that in the period α and the period β, the input voltage Vin, the capacitive load voltage Vc, and L that is the self-inductance of the choke coil are considered to be constant.

Duty2h = (Imax2 × L−Vc × Duty2l × Ts / N) / {Ts (Vin−Vc) / N} (9)
Accordingly, in the second mode, after both the first switching element Q1 and the second switching element Q2 are turned on, the choke coil current is set to the second allowable maximum value after the total length T2h of the period α and the period β has elapsed. Imax2.

  Note that the first allowable maximum value Imax1 and the second allowable maximum value Imax2 may be the same value or different values. Moreover, when this embodiment is applied to the power converter device which concerns on 2nd Embodiment, what is necessary is just to set Duty1 mentioned above about control of a 1st mode.

  In addition to the effect which the power converter device which concerns on 1st-3rd embodiment show | plays, the power converter device which concerns on this embodiment has the following effects by the said structure.

  In each of the first mode and the second mode, the duty values Duty1, Duty2l, and Duty2h are set so that the choke coil current does not exceed the first allowable maximum value Imax1 and the second allowable maximum value Imax2. Therefore, the choke coil current does not increase excessively, and deterioration and failure of the DCDC converter 10 can be suppressed.

<Fifth Embodiment>
The power conversion device according to the present embodiment uses the same circuit as the power conversion device according to the first embodiment or the third embodiment, and the control method is different. In the power conversion device according to the present embodiment, control in the first to third modes is performed as in the first embodiment, but the control signals in the respective modes are different.

  FIG. 9A shows a control signal in the first mode in the present embodiment. In the first mode, each of the first switching element Q1 and the second switching element Q2 has a common control cycle Ts, and transmits a control signal having a phase difference of a half cycle of the control cycle Ts. The control signal is one of an ON signal and an OFF signal that instructs one of the ON state and the OFF state for each of the first switching element Q1 and the second switching element Q2.

  The control signals of the first switching element Q1 and the second switching element Q2 respectively have an ON period of length T1 (<Ts / 4) and a length (Ts / 4-T1) in a half cycle of the control cycle Ts. The OFF period is alternately repeated twice. In the subsequent half cycle (first predetermined period), the OFF state is continued.

  That is, in the first mode, one OFF state of the first switching element Q1 and the second switching element Q2 is continued, and the other ON state and OFF state of the first switching element Q1 and the second switching element Q2 are alternately switched. Repeat the control. By doing so, similarly to the first embodiment, the period β in which one of the first switching element Q1 and the second switching element Q2 is ON and the other is OFF, and the first switching element Q1 and the second switching element. The period γ in which both the elements Q2 are OFF can be alternately repeated.

  FIG. 9B shows a control signal in the second mode in the present embodiment. In the second mode, each of the first switching element Q1 and the second switching element Q2 has a common control cycle Ts and transmits a control signal having a phase difference of a half cycle of the control cycle Ts.

  The control signals of the first switching element Q1 and the second switching element Q2 respectively have an ON period of length T2h (<Ts / 4) and a length (Ts / 4−T2h) in the half cycle of the control period Ts. The OFF period is alternately repeated twice. In the subsequent half cycle (first predetermined period), the ON period of length T2l (<Ts / 4) and the OFF period of length (Ts / 4-T2l) are alternately repeated twice. At this time, in each of the control signals of the first switching element Q1 and the second switching element Q2, the timing at which the ON period of length T2h is started and the timing at which the ON period of length T2l is started are mutually Ts. / 2 periods shifted. Therefore, the timing at which the ON period of the first switching element Q1 is started coincides with the timing at which the ON period of the second switching element Q2 is started.

  By doing so, as in the first embodiment, the period α in which both the first switching element Q1 and the second switching element Q2 are ON, and one of the first switching element Q1 and the second switching element Q2 is ON. The period β in which the other is OFF and the period γ in which both the first switching element Q1 and the second switching element Q2 are OFF can be sequentially repeated.

  FIG. 9C shows a control signal in the third mode in the present embodiment. In the third mode, each of the first switching element Q1 and the second switching element Q2 has a common control cycle Ts and transmits a control signal having a phase difference of a half cycle of the control cycle Ts.

  The control signals of the first switching element Q1 and the second switching element Q2 are respectively the ON period of length T3 ′ (<Ts / 4) and the length (Ts / 4−T3 ′) in the half cycle of the control period Ts. ) And the OFF period are repeated twice. In the subsequent half cycle (first predetermined period), the OFF state is continued.

  That is, in the third mode, the ON state of one of the first switching element Q1 and the second switching element Q2 is continued, and the other ON state and OFF state of the first switching element Q1 and the second switching element Q2 are alternated. Repeat the control. By doing so, as in the first embodiment, the period α in which both the first switching element Q1 and the second switching element Q2 are ON, and one of the first switching element Q1 and the second switching element Q2 is ON. Yes, and the period β in which the other is OFF can be alternately repeated.

  In the first to third modes, the ON period is provided twice each in the 1/2 control cycle, but may be provided three times or more.

  In addition, the length of the ON period of the first switching element Q1 and the second switching element Q2 in the first to third modes may be set in the same manner as in the first embodiment. Further, the lengths of the ON periods of the first switching element Q1 and the second switching element Q2 in the first mode and the second mode may be set similarly to the fourth embodiment.

  Further, as in the second embodiment, only the control in the first and third modes may be performed, and the second mode may not be performed.

  With the above configuration, the power conversion device according to the present embodiment has an effect similar to that of each of the above embodiments.

<Sixth Embodiment>
The power conversion device according to the present embodiment uses the same circuit as the power conversion device according to the first embodiment or the third embodiment, and the control method is different. In the power conversion device according to the present embodiment, control in the first to third modes is performed as in the first embodiment, but the control signals in the respective modes are different.

  FIGS. 10A to 10C show control signals in the first to third modes in the present embodiment, respectively.

  As shown in FIG. 10A, in the first mode, the OFF state of the second switching element Q2 is continued in the predetermined period (first predetermined period) from t0 to t2, and the ON state of the first switching element Q1 is The OFF state is repeated alternately. Further, during the predetermined period (first predetermined period) from t1 to t4, the OFF state of the first switching element Q1 is continued, and the ON state and the OFF state of the second switching element Q2 are alternately repeated. Furthermore, the OFF state of the 2nd switching element Q2 is continued for the predetermined period (1st predetermined period) of t3-t5, and the ON state and OFF state of the 1st switching element Q1 are repeated alternately.

  At this time, the predetermined period for continuing the OFF state of the first switching element Q1 and the predetermined period for continuing the OFF state of the second switching element Q2 may be the same length or different lengths. Good. Also, each of the predetermined periods in which the first switching element Q1 is kept in the OFF state may have the same length or different lengths. The same applies to the second switching element Q2. In addition, the number of times of alternately repeating the ON state and the OFF state of the other while one of them is in the OFF state may be any number, and each may be the same length or a different length. There may be. For example, the first switching element Q1 may be turned on once or twice during a predetermined period (first predetermined period) from t0 to t2 in FIG. 10A, and a predetermined period (first predetermined period) from t1 to t4. ), The second switching element Q2 may be turned on a plurality of times.

  That is, in the first mode, one OFF state of the first switching element Q1 and the second switching element Q2 is continued, and the other ON state and OFF state of the first switching element Q1 and the second switching element Q2 are alternately switched. Repeat the control. By doing so, similarly to the first embodiment, the period β in which one of the first switching element Q1 and the second switching element Q2 is ON and the other is OFF, and the first switching element Q1 and the second switching element. The period γ in which both the elements Q2 are OFF can be alternately repeated.

  As shown in FIG. 10B, in the second mode, both the first switching element Q1 and the second switching element Q2 are turned on at t0, the second switching element Q2 is turned off at t1, and the first switching element is turned on at t2. The switching element Q1 is turned off. This OFF period continues until t3. Therefore, t0 to t1 is a period α in which both the first switching element Q1 and the second switching element Q2 are ON, and t1 to t2 are only one of the first switching element Q1 and the second switching element Q2 being ON. It becomes a certain period β, and t2 to t3 become a period γ in which both the first switching element Q1 and the second switching element Q2 are OFF. Similarly, both the first switching element Q1 and the second switching element Q2 are turned on at t3, the second switching element Q2 is turned off at t4, and the first switching element Q1 is turned off at t5. This OFF period continues until t6.

  Subsequently, both the first switching element Q1 and the second switching element Q2 are turned on at t6, the first switching element Q1 is turned off at t7, and the second switching element Q2 is turned off at t8. Therefore, in the period β from T7 to t8, the switching elements in the ON state are different from the period β from t1 to t2 and the period β from t4 to t5.

  In addition, you may perform control which always turns off one of the 1st switching element Q1 and the 2nd switching element Q2 first.

  That is, in the second mode, both the first switching element Q1 and the second switching element Q2 are turned on, and one of the first switching element Q1 and the second switching element Q2 is turned on and the other is turned off. The control and the control for turning on both the first switching element Q1 and the second switching element Q2 can be repeated in order.

  As shown in FIG. 10C, in the third mode, the ON state of the second switching element Q2 is continued during the predetermined period (second predetermined period) from t0 to t2, and the ON state of the first switching element Q1 is The OFF state is repeated alternately. Further, during a predetermined period (second predetermined period) after t1, the ON state of the first switching element Q1 is continued, and the ON state and OFF state of the second switching element Q2 are alternately repeated.

  At this time, the predetermined period for continuing the ON state of the first switching element Q1 and the predetermined period for continuing the ON state of the second switching element Q2 may be the same length or different lengths. Good. In addition, each of the predetermined periods during which the first switching element Q1 is kept on may have the same length or a different length. The same applies to the second switching element Q2. In addition, the number of times of alternately repeating the ON state and the OFF state of the other while one is in the ON state may be any number, and each may have the same length or a different length. There may be. For example, the first switching element Q1 may be turned on only once or three times or more in a predetermined period (second predetermined period) from t0 to t2 in FIG. In a predetermined period), the second switching element Q2 may be turned on only once or three times or more.

  That is, in the third mode, the ON state of one of the first switching element Q1 and the second switching element Q2 is continued, and the other ON state and OFF state of the first switching element Q1 and the second switching element Q2 are alternated. Repeat the control. By doing so, as in the first embodiment, the period α in which both the first switching element Q1 and the second switching element Q2 are ON, and one of the first switching element Q1 and the second switching element Q2 is ON. And the period β in which the other is OFF can be alternately repeated.

  In the present embodiment, the ON period of the first switching element Q1 and the second switching element Q2 in the first mode and the second mode is the same as the fourth embodiment in that the choke coil current is equal to the first allowable maximum value Imax1 and the first mode. 2 may be set so as not to exceed the allowable maximum value Imax2. Further, the ON periods of the first switching element Q1 and the second switching element Q2 in the third mode may be set as in the first embodiment.

  The control signals shown in FIGS. 10A to 10C are merely examples, and the first switching element Q1 and the second switching element Q2 may be controlled in the first to third modes.

  In addition, in this embodiment, the first switching element Q1 and the second switching element Q2 are further provided with a timer for calculating the cumulative value of the respective ON times. In a predetermined period (third predetermined period), control is performed so that the accumulated value of the ON time of the first switching element Q1 is equal to the accumulated value of the ON time of the second switching element Q2. By doing so, it is possible to prevent the DCDC converter 10 from being demagnetized and to equalize the loss and heat generation of the first switching element Q1 and the second switching element Q2.

  At this time, in each of the first to third modes, the cumulative value of the ON time of the first switching element Q1 may be equal to the cumulative value of the ON time of the second switching element Q2. Further, the predetermined period (third predetermined period) may span a plurality of modes. In this case, for example, if there is a difference between the cumulative value of one ON time and the cumulative value of the other ON time in the first mode, the difference is calculated in the second mode and the third mode. Control may be performed so as to fill.

  If there is a difference between the cumulative value of the ON time of the first switching element Q1 and the cumulative value of the ON time of the second switching element Q2 at the time when the charging to the capacitive load 30 is completed, the next time Control may be performed to fill the difference when charging.

  Although the control is performed so that the cumulative ON time of the first switching element Q1 and the cumulative ON time of the second switching element Q2 are equal, the concept of “equal” only means that they are completely matched. Instead, a predetermined error is allowed.

  With the above configuration, the power conversion device according to the present embodiment has an effect similar to that of each of the above embodiments.

<Seventh embodiment>
The power converter according to this embodiment is partly different in circuit configuration from the power converter according to the first embodiment, and the processing executed by the pulse generator 17 is different. FIG. 11 shows a circuit diagram of the power converter according to the present embodiment.

  The power conversion device further includes current detection means 19. The current detection means 19 detects a reactor current IL that is a current flowing through the choke coil 11 and inputs it to the pulse generator 17. Since other configurations are the same as those of the first embodiment, description thereof is omitted. Moreover, it is good also considering a power converter device as the circuit structure based on 3rd Embodiment shown in FIG.

  Next, processing executed by the pulse generation unit 17 according to the present embodiment will be described with reference to FIG.

  The constant current control unit 50 includes a first command value Iref1 that is a command value of the reactor current IL in the first mode, a second command value Iref2 that is a command value of the reactor current IL in the second mode, and a reactor in the third mode. A third command value Iref3, which is a command value of the current IL, is read from the memory and used for control.

  The first command value Iref1 is based on the value of the first command value Iref1 when one of the first switching element Q1 and the second switching element Q2 transitions from the ON state to the OFF state. It is set so that the generated avalanche current does not become excessive. The first command value Iref1 is output from the constant current control unit 50 as it is.

  The second command value Iref2 may be the same value as the first command value Iref1, or may be a different value. That is, the second command value Iref2 is set so that the avalanche current does not become excessive.

  On the other hand, the input voltage Vin and the capacitive load voltage Vc are input to the current correction unit 51, and a correction value to be added to the second command value Iref2 is output. This correction value is added to the second command value Iref2 in the adder 52, and a second correction command value Iref2 'is output. The relationship between the input voltage Vin and the capacitive load voltage Vc and the correction value added to the second command value Iref2 may be obtained by calculation or may be obtained based on a stored table.

  In the second mode controlled based on the second command value Iref2, the duty value of the first switching element Q1 is fixed to 50%, and the duty value of the second switching element Q2 is changed. Specifically, in the period α in which the first switching element Q1 and the second switching element Q2 are ON, the reactor current IL becomes the corrected second correction command value Iref2 ′, and the first switching element Q1 is ON, The duty value of the second switching element Q2 is changed so that the reactor current IL becomes the second command value Iref2 during the period β in which the second switching element Q2 is OFF.

  The relationship between the second command value Iref2 and the second correction command value Iref2 'will be described in detail with reference to FIGS.

  FIG. 13A shows the reactor current IL when the input voltage Vin is larger than the value obtained by dividing the capacitive load voltage Vc by the turns ratio N. In this case, the reactor current IL increases during the period β in which the first switching element Q1 is ON and the second switching element Q2 is OFF. Therefore, when the reactor current IL at the timing when the second switching element Q2 is turned off is set to the second command value Iref2, the reactor current IL may be excessive. Therefore, the ON period of the second switching element Q2 corresponding to the period α is set so that the reactor current IL becomes the second command value Iref2 at the timing when the first switching element Q1 is turned OFF.

  FIG. 13B shows the reactor current IL when the input voltage Vin is equal to the value obtained by dividing the capacitive load voltage Vc by the turns ratio N. In this case, the reactor current IL does not increase or decrease during the period β. Therefore, the second command value Iref2 and the second correction command value Iref2 'are equal.

  FIG. 13C shows the reactor current IL when the input voltage Vin is smaller than the value obtained by dividing the capacitive load voltage Vc by the turns ratio N. In this case, the reactor current IL decreases during the period β. Therefore, when the reactor current IL at the timing when the second switching element Q2 is turned OFF is set to the second command value Iref2, the charging time increases as the reactor current IL decreases in the period β. Therefore, the ON period of the second switching element Q2 corresponding to the period α is set so that the second command value Iref2 is obtained at the timing when the first switching element Q1 is turned OFF.

  The third command value Iref3 is input to the feedback control unit 53. The third command value Iref3 is sufficiently larger than the first command value Iref1 and the second command value Iref2. In addition, the feedback control unit 53 acquires an average value IL_ave that is the actual current of the reactor current IL. The average value IL_ave is obtained by accumulating the reactor current IL detected by the current detection means 19 for a predetermined period and averaging the values. The third command value Iref3 and the average value IL_ave are input to the adder 54, and the adder 54 takes the difference between the third command value Iref3 and the average value IL_ave. This difference is input to the PI controller 55 and input to the limiter 56. In the limiter 56, if the output value of the PI controller 55 is larger than the upper limit value, the output value is limited to the upper limit value. The output value from the limiter 56 is added to the third command value Iref3 by the adder 57 and output from the feedback control unit 53.

  On the other hand, the input voltage Vin and the capacitive load voltage Vc are input to the current correction unit 58, and a correction value of the third command value Iref3 is output. This correction value is added to the third command value Iref3 by the adding unit 59, and a third correction command value Iref3 'is output. As in the second mode, during the period β in which the first switching element Q1 is ON and the second switching element Q2 is OFF, the amount of decrease in the reactor current IL varies depending on the input voltage Vin and the capacitive load voltage Vc. This is because it is necessary to add a correction value that takes this decrease amount into consideration. In addition, it is necessary to correct the deviation between the third command value Iref3 and the average value IL_ave, which is generated by the slope compensation unit 73 described later.

  The first command value Iref1, the second correction command value Iref2 ', and the third correction command value Iref3' output from the constant current control unit 50 are input to the mode selection unit 60. Further, the capacitive load voltage Vc is also input to the mode selection unit 60, and the capacitive load voltage Vc is compared with the first predetermined value V1 and the second predetermined value V2, and the first command value Iref1 and the second correction command are compared. Whether to output the value Iref2 ′ or the third correction command value Iref3 ′ is determined and output.

  Any of the first command value Iref 1, the second correction command value Iref 2 ′, and the third correction command value Iref 3 ′ output from the mode selection unit 60 is input to the peak current control unit 70. Any of the first command value Iref1, the second correction command value Iref2 ', and the third correction command value Iref3' is converted into an analog value by the DA converter 71 and input to the minus terminal of the comparator 72.

  On the other hand, the slope compensator 73 of the peak current controller 70 generates a slope signal obtained from the value of the register and inputs it to the DA converter 74. The slope signal is a sawtooth wave signal that monotonously increases linearly from 0A in each control cycle. Then, the slope signal converted into an analog waveform by the DA converter 74 and the reactor current IL are added by the adder 75 and input to the plus terminal of the comparator 72. The slope compensator 73 may directly generate an analog waveform and input it to the comparator 72 without going through the DA converter 74.

  The slope compensator 73 sets the value of the slope signal to zero in the first mode and the second mode, and outputs the above-mentioned sawtooth wave slope signal in the third mode. This is because, in the first mode and the second mode, the reactor current IL becomes zero at the timing when both the first switching element Q1 and the second switching element Q2 are turned OFF, and as a result, the subharmonic oscillation phenomenon does not occur. It is.

  The comparator 72 outputs a slope signal to any one of the first command value Iref1, the second correction command value Iref2 ′, the third correction command value Iref3 ′ input to the minus terminal, and the reactor current IL input to the plus terminal. Compare with the added value. Then, in a period in which the input value of the plus terminal is smaller than the input value of the minus terminal, a signal in a high state is input to the S terminal of the RS flip-flop 77, and the period in which the input value of the plus terminal is larger than the input value of the minus terminal. , A low signal is input to the S terminal of the RS flip-flop 77. A clock signal from the clock 76 is input to the R terminal of the RS flip-flop 77.

  In the first mode, the RS flip-flop 77 transmits a signal that turns on one of the first switching element Q1 and the second switching element Q2 and turns off the other if the input signal is a high state signal. . On the other hand, if the input signal is a low signal in the first mode, a signal for turning off both the first switching element Q1 and the second switching element Q2 is output.

  In the second mode, the RS flip-flop 77 transmits a signal for turning on both the first switching element Q1 and the second switching element Q2 if the input signal is a high state signal. On the other hand, in the second mode, if the input signal is a low state signal, the first switching element Q1 is turned on until the half period of the control period, that is, until the Duty value reaches 50%, and the second A signal for turning off the switching element Q2 is output. If the duty value exceeds 50%, a signal for turning off both the first switching element Q1 and the second switching element Q2 is output. Note that when the input signal is a low-level signal, the duty limiting unit 78 may perform control to turn on the first switching element Q1 until the duty value becomes 50%.

  In the third mode, the RS flip-flop 77 transmits a signal for turning on both the first switching element Q1 and the second switching element Q2 if the input signal is a high-level signal. On the other hand, in the third mode, if the input signal is a low signal, a signal is output that turns on one of the first switching element Q1 and the second switching element Q2 and turns off the other.

  The output of the RS flip-flop 77 is output to the drive circuit 18 that drives the first switching element Q1 and the second switching element Q2 after the upper limit value and the lower limit value of the duty value are set by the duty limiting unit 78. Specifically, in the first mode, the upper limit value of each Duty value is set to 50% or less so that the ON period of the first switching element Q1 and the ON period of the second switching element Q2 do not overlap. In the second mode, as described above, the duty value of the first switching element Q1 is set to 50%. For this reason, in the second mode, the upper limit value is set so that the duty value of the second switching element Q2 does not become larger than the duty value of the first switching element Q1. In the third mode, the lower limit value of the Duty value is set to a value larger than 50% so that a period in which the ON period of the first switching element Q1 and the second switching element Q2 overlap is generated.

  With the configuration described above, the power conversion device according to the present embodiment has the following effects in addition to the effects exhibited by the power conversion device according to the first embodiment.

  The peak current control unit 70 performs constant current control using the first command value Iref1, the second correction command value Iref2 ', and the third correction command value Iref3' input from the constant current control unit 50. Thereby, in the case where a change occurs in the input voltage Vin, the robustness against overcurrent can be improved.

  In the second mode, the duty value of one switching element is fixed, and peak current control is performed by changing the ON period of the other switching element. Therefore, the control can be simplified as compared with the case where the duty values of the two switching elements Q1, Q2 are both changed. As a result, robustness against overcurrent can be improved.

  In the second mode, since the fixed duty value is 50% or less, the period γ in which both the first switching element Q1 and the second switching element Q2 are OFF can be made sufficiently long. Therefore, in the period γ, the exciting current flowing through the transformer Tr can be sufficiently reduced, and the bias and saturation of the transformer Tr can be suppressed.

  The first command value Iref1 in the first mode and the second command value Iref2 in the second mode are different from the third command value Iref3 in the third mode. Thereby, the reactor current IL does not become excessive in the first mode and the second mode. Therefore, when both the first switching element Q1 and the second switching element Q2 are turned off, the avalanche current generated based on the reactor current IL is not excessively increased, and the first switching element Q1 and the second switching element Q2 fail. And deterioration can be suppressed. In addition, in the third mode, the charging time can be shortened by setting the third command value Iref3 to a larger value.

  In the second mode constant current control, the second command value Iref2 is corrected by using the capacitive load voltage Vc and the input voltage Vin to obtain the second correction command value Iref2 '. The ON period of the second switching element Q2 is determined by the second correction command value Iref2 '. As a result, when the input voltage Vin is larger than the value obtained by dividing the capacitive load voltage Vc by the turn ratio N, the second correction command value Iref2 ′ becomes smaller than the second command value Iref2, and the reactor current IL in the period β. Is increased to become the second command value Iref2. Therefore, the situation where the avalanche current becomes excessively large can be suppressed. On the other hand, when the input voltage Vin is smaller than the value obtained by dividing the capacitive load voltage Vc by the turn ratio N, the second correction command value Iref2 ′ is larger than the second command value Iref2, and the reactor current IL is increased in the period β. After the decrease, the second command value Iref2 is obtained. Therefore, in period α, reactor current IL can be further increased, and the charging period can be shortened.

<Modification>
In the first embodiment, when switching from the second mode to the third mode, the first predetermined value V1 is set so that the output voltage Vout of the transformer Tr is equal to the capacitive load voltage Vc. However, the first predetermined value V1 may be corrected using the predetermined correction value ΔV1, and the first predetermined value V1 may be set by the following equation (7).

V1 = N × Vin / (2 × (1-Duty0)) − ΔV1 (7)
Even if there is a difference between the output voltage Vout of the transformer Tr and the capacitive load voltage Vc, a large current is not always generated immediately. That is, the actual output voltage Vout is determined by the capacitive load 30, the wiring, the resistance of the first coil L1 and the second coil L2, the loss in each switching element, the difference between the command value of each PWM signal and the actual duty value, and the like. There is a difference between the theoretical values. Therefore, in practice, the current value does not become infinite. If the current value is smaller than the withstand current of the elements in the circuit, the generation can be permitted.

  By the way, when the control in the third mode is performed, the charging speed to the capacitive load 30 can be increased as described above. Therefore, by subtracting the positive correction value ΔV1 from the first predetermined value V1 and starting the control in the third mode earlier, the capacity is compared with the case where the theoretical value is used as the first predetermined value V1. The charging speed to the load 30 can be increased.

  The correction value ΔV1 can also be a negative value. In this case, the first predetermined value V1 becomes large and the transition to the third mode is delayed, so the charging speed to the capacitive load 30 decreases. On the other hand, the current generated by the difference between the output voltage Vout of the transformer Tr and the capacitive load voltage Vc can be further suppressed, and a circuit in which no load is applied to the elements in the circuit can be obtained.

  In the first embodiment, when the third mode control is performed, the duty 3 is set so that the output voltage Vout of the transformer Tr and the capacitive load voltage Vc are equal. However, the capacitive load voltage Vc may be corrected using a predetermined correction value ΔVc, and Duty3 may be set by the following equation (8).

Duty3 = 1−N × Vin / (2 × (Vc + ΔVc)) (8)
As described above, even if there is a difference between the output voltage Vout of the transformer Tr and the capacitive load voltage Vc, a large current is not always generated immediately. Therefore, when calculating Duty3, Duty3 can be made larger than the theoretical value by adding the correction value ΔVc to the capacitive load voltage Vc. Thereby, the application time of the input voltage Vin to the choke coil 11 can be lengthened, the current used for charging can be increased, and the charging speed can be further increased. Further, the correction value ΔVc may be the same value as the correction value ΔV1 or a different value. Further, the correction value ΔVc may be changed as the capacitive load voltage Vc increases.

  The correction value ΔV1 can also be a negative value. In this case, since the value of Duty3 becomes small and the period α, which is the period in which the current of the choke coil 11 increases, the charging speed to the capacitive load 30 decreases. On the other hand, the current generated by the difference between the output voltage Vout of the transformer Tr and the capacitive load voltage Vc can be further suppressed, and a circuit in which no load is applied to the elements in the circuit can be obtained.

  In the first embodiment, the first mode is set when the output voltage Vout is equal to or lower than the second predetermined value V2, and the second mode is set when the output voltage Vout is greater than the second predetermined value V2 and equal to or lower than the first predetermined value V1. The third mode is set when the output voltage Vout is larger than the first predetermined value V1. However, when the output voltage Vout is smaller than the second predetermined value V2, the first mode is set. When the output voltage Vout is equal to or higher than the second predetermined value V2 and smaller than the first predetermined value V1, the second mode is set. It is good also as a 3rd mode when it is more than the 1st predetermined value V1. The same applies to the third embodiment.

  In the first embodiment, the control periods of the first mode, the second mode, and the third mode are the same value. However, the control periods may be different in each mode. That is, in each mode, it is only necessary that the control cycle of the first PWM signal is equal to the control cycle of the second PWM signal. In the second embodiment, the control periods of the first mode and the third mode may be different values. The same applies to the third embodiment.

  In each of the above embodiments, it is preferable to set the length T1 of the ON period so that the choke coil current becomes zero at the end of the period γ of the first mode, but this is not necessarily limited thereto. When the length T1 of the ON period is set so that the choke coil current does not become zero at the end of the period γ, the choke coil current gradually increases by repeating the control in the first mode. In this case, the ON period length T1 may be set so that the gradually increasing choke coil current does not exceed the rated current values of the first switching element Q1 and the second switching element Q2.

  In the first embodiment and the third embodiment, it is preferable to set the lengths T2h and T2l of the ON period so that the choke coil current becomes zero at the end of the second mode period γ. Not as long. When the lengths T2h and T2l of the ON period are set so that the choke coil current does not become zero at the end of the period γ, the choke coil current gradually increases by repeating the control in the second mode. In this case, the lengths T2h and T2l of the ON period may be set so that the gradually increasing choke coil current does not exceed the rated current values of the first switching element Q1 and the second switching element Q2.

  In each of the above embodiments, it is preferable to set the length T3 of the ON period so that the increase amount of the choke coil current in the period α is equal to the decrease amount of the choke coil current in the period β. is not. When the ON period length T3 is set so that the decrease amount of the choke coil current in the period β is smaller than the increase amount of the choke coil current in the period α, the third mode control is repeated. The choke coil current increases gradually. In this case, the ON period length T3 may be set so that the gradually increasing choke coil current does not exceed the rated current values of the first switching element Q1 and the second switching element Q2.

  In the first mode of the first embodiment, one control cycle is defined from the timing when the first switching element Q1 is turned on to the timing when the first switching element Q1 is turned on next. The definition of is not limited to this. For example, one control cycle may be from the timing when the first switching element Q1 is turned OFF to the timing when the first switching element Q1 is turned ON next. Similarly in other modes, the definition of the control period is not limited to the above embodiment. Further, the definition of one control cycle in the fifth embodiment is not limited to the above example. For example, in the control in the first mode shown in FIG. 8A, a control cycle including the period β and the period γ once each may be defined as one control cycle. Also in this case, the start of the control cycle may be the timing at which the switching element is turned off.

  In the seventh embodiment, the second command value Iref2 is corrected. However, this correction may not be performed. In this case, the reactor current IL becomes the second command value Iref2 at the timing when one of the first switching element Q1 and the second switching element Q2 is turned OFF. In the case of performing such control, the ON period of the switching element having the shorter ON period may be constant, the ON period of the other switching element may be changed, and the ON periods of both switching elements may be changed. It may be variable.

  In the seventh embodiment, the second mode control may not be performed as in the second embodiment.

  In each of the above embodiments, the power conversion device is provided in the hybrid car, but the invention can also be applied to other than the hybrid car. In addition, although the DCDC converter 10 can transmit and receive power bidirectionally, it may be configured to be capable of only supplying power from the first coil L1 side to the second coil L2 side. The bridge circuit 14 may be a diode bridge circuit.

  DESCRIPTION OF SYMBOLS 11 ... Choke coil, 12 ... Predetermined connection point, 13 ... Center tap, 14 ... Bridge circuit, 16 ... Capacitive load voltage detection means, 17 ... Pulse generation part, 20 ... Secondary battery, 30 ... Capacitive load, L1 ... 1st Coil, L2 ... second coil, Q1 ... first switching element, Q2 ... second switching element.

Claims (24)

A DC power source (20);
A choke coil (11) having an input terminal connected to the positive electrode of the DC power supply;
A first coil (L1) having a center tap (13) and having both ends connected to a predetermined connection point (12) via a first switching element (Q1) and a second switching element (Q2), respectively;
A second coil (L2) magnetically coupled to the first coil;
A capacitive load (30) connected to the second coil via a rectifier circuit (14);
Capacitive load voltage detecting means (16) for detecting a capacitive load voltage which is the voltage of the capacitive load;
A pulse generator (17) that transmits one of an ON signal and an OFF signal to each of the first switching element and the second switching element;
The center tap is connected to the negative electrode of the DC power source and the predetermined connection point is connected to the output end of the choke coil, or the center tap is connected to the output end of the choke coil and the predetermined connection point Is connected to the negative electrode of the DC power supply,
When the capacitive load voltage is less than or equal to a first predetermined value, one of the first switching element and the second switching element is turned on and the other is turned off, and the first switching element and the second switching element The first mode in which the control to turn off both of the switching elements is repeated alternately,
When the capacitive load voltage is greater than the first predetermined value, control is performed to turn on one of the first switching element and the second switching element and turn off the other, and the first switching element and the first switching element. A power conversion device characterized in that a third mode in which the control for turning on both of the two switching elements is alternately repeated is a third mode. A DC power source (20);
A choke coil (11) having an input terminal connected to the positive electrode of the DC power supply;
A first coil (L1) having a center tap (13) and having both ends connected to a predetermined connection point (12) via a first switching element (Q1) and a second switching element (Q2), respectively;
A second coil (L2) magnetically coupled to the first coil;
A capacitive load (30) connected to the second coil via a rectifier circuit (14);
Capacitive load voltage detecting means (16) for detecting a capacitive load voltage which is the voltage of the capacitive load;
A pulse generator (17) that transmits one of an ON signal and an OFF signal to each of the first switching element and the second switching element;
The center tap is connected to the negative electrode of the DC power source and the predetermined connection point is connected to the output end of the choke coil, or the center tap is connected to the output end of the choke coil and the predetermined connection point Is connected to the negative electrode of the DC power supply,
A control in which one of the first switching element and the second switching element is turned on and the other is turned off when the capacitive load voltage is equal to or smaller than a second predetermined value that is smaller than the first predetermined value; The first mode in which the control of turning off both the first switching element and the second switching element is alternately repeated,
A control for turning on both the first switching element and the second switching element when the capacitive load voltage is greater than the second predetermined value and less than or equal to the first predetermined value; A second mode in which one of the switching element and the second switching element is turned on and the other is turned off, and the control of turning off both the first switching element and the second switching element is repeated in order. ,
When the capacitive load voltage is greater than the first predetermined value, control is performed to turn on one of the first switching element and the second switching element and turn off the other, and the first switching element and the first switching element. A power conversion device characterized in that a third mode in which the control for turning on both of the two switching elements is alternately repeated is a third mode.   The power conversion device according to claim 1, wherein the pulse generation unit transmits a signal having the same control period to each of the first switching element and the second switching element. A DC power source (20);
A choke coil (11) having an input terminal connected to the positive electrode of the DC power supply;
A first coil (L1) having a center tap (13) and having both ends connected to a predetermined connection point (12) via a first switching element (Q1) and a second switching element (Q2), respectively;
A second coil (L2) magnetically coupled to the first coil;
A capacitive load (30) connected to the second coil via a rectifier circuit (14);
Capacitive load voltage detecting means (16) for detecting a capacitive load voltage which is the voltage of the capacitive load;
A pulse generator (17) for transmitting a first PWM signal and a second PWM signal having the same control period to each of the first switching element and the second switching element;
The center tap is connected to the negative electrode of the DC power source and the predetermined connection point is connected to the output end of the choke coil, or the center tap is connected to the output end of the choke coil and the predetermined connection point Is connected to the negative electrode of the DC power supply,
When the capacitive load voltage is less than or equal to a first predetermined value, the phase difference between the first PWM signal and the second PWM signal is half of the control period, and the first PWM signal and the second PWM signal The duty value is the first mode in which both are equal values less than 0.5,
When the capacitive load voltage is greater than the first predetermined value, the phase difference between the first PWM signal and the second PWM signal is half of the control period, and the first PWM signal and the second PWM signal The power conversion device is characterized in that the duty mode of the third mode is set to an equal value both greater than 0.5. A DC power source (20);
A choke coil (11) having an input terminal connected to the positive electrode of the DC power supply;
A first coil (L1) having a center tap (13) and having both ends connected to a predetermined connection point (12) via a first switching element (Q1) and a second switching element (Q2), respectively;
A second coil (L2) magnetically coupled to the first coil;
A capacitive load (30) connected to the second coil via a rectifier circuit (14);
Capacitive load voltage detecting means (16) for detecting a capacitive load voltage which is the voltage of the capacitive load;
A pulse generator (17) for transmitting a first PWM signal and a second PWM signal having the same control period to each of the first switching element and the second switching element;
The center tap is connected to the negative electrode of the DC power source and the predetermined connection point is connected to the output end of the choke coil, or the center tap is connected to the output end of the choke coil and the predetermined connection point Is connected to the negative electrode of the DC power supply,
When the capacitive load voltage is equal to or smaller than a second predetermined value that is smaller than the first predetermined value, the phase difference between the first PWM signal and the second PWM signal is half of the control period, The duty values of the first PWM signal and the second PWM signal are set to a first mode in which both are equal values less than 0.5,
When the capacitive load voltage is greater than the second predetermined value and less than or equal to the first predetermined value, the phase difference between the first PWM signal and the second PWM signal is one cycle difference of the control cycle. And the first PWM signal and the second PWM signal are a signal of a first duty value and a signal of a second duty value different from the first duty value are alternately repeated for each control cycle, and The sum of the first duty value and the second duty value is less than 1, and the timing at which the signal of the first duty value is switched from OFF to ON, and the timing at which the signal of the second duty value is switched from OFF to ON. Is a second mode that is one cycle difference of the control cycle,
When the capacitive load voltage is greater than the first predetermined value, the phase difference between the first PWM signal and the second PWM signal is half of the control period, and the first PWM signal and the second PWM signal The power conversion device is characterized in that the duty mode of the third mode is set to an equal value both greater than 0.5. An input voltage detecting means (15) for detecting an input voltage which is a voltage of the DC power supply;
The power converter according to claim 4 or 5, wherein the first predetermined value is calculated by the following equation (1).
V1 = N × Vin / (2 × (1-Duty0)) (1)
Here, V1 is the first predetermined value, N is the turn ratio of the second coil to the first coil, Vin is the input voltage, and Duty0 is used when starting the control of the third mode. The initial value of the Duty value, which is a value greater than 0.5 and less than 1. An input voltage detecting means (15) for detecting an input voltage which is a voltage of the DC power supply;
6. The power conversion device according to claim 4, wherein the duty value when the capacitive load voltage is greater than the first predetermined value is calculated by the following equation (2).
Duty3 = 1−N × Vin / (2 × Vc) (2)
Here, Duty3 is the duty value of the third mode, N is the turn ratio of the second coil to the first coil, Vin is the input voltage, and Vc is the capacitive load voltage. The power conversion device according to claim 6, wherein the duty value when the capacitive load voltage is larger than the first predetermined value is calculated by the following equation (2).
Duty3 = 1−N × Vin / (2 × Vc) (2)
Here, Duty3 is the duty value of the third mode, N is the turn ratio of the second coil to the first coil, Vin is the input voltage, and Vc is the capacitive load voltage.   The power converter according to claim 6, wherein the first predetermined value calculated by the above equation (1) is corrected using a predetermined correction value.   The duty value is calculated by adding a correction value to the capacitive load voltage when calculating the duty value when the capacitive load voltage is greater than the first predetermined value according to the above equation (2). The power converter according to claim 7 or 8. An input voltage detecting means (15) for detecting an input voltage which is a voltage of the DC power supply;
The power converter according to claim 4 or 5, wherein the duty value in the first mode is calculated by the following equation (7).
Duty1 = Imax1 × L / {Ts (Vin−Vc / N)} (7)
Here, Duty1 is the Duty value of the first mode, Imax1 is the maximum value of the current flowing through the choke coil that can be allowed in the first mode, and L is the self-inductance of the choke coil. Ts is the control period, Vin is the input voltage, Vc is the capacitive load voltage, and N is a turn ratio of the second coil to the first coil. An input voltage detecting means (15) for detecting an input voltage which is a voltage of the DC power supply;
The power converter according to claim 5, wherein the first duty value and the second duty value in the second mode are calculated by the following expressions (8) and (9).
Duty2l <Imax2 × L / (Ts × Vin) (8)
Duty2h = (Imax2 × L−Vc × Duty2l × Ts / N) / {Ts (Vin−Vc) / N} (9)
Here, Duty21 is one of the first duty value and the second duty value, Duty2h is the other of the first duty value and the second duty value, and is larger than Duty2l, and Imax2 is the choke. The maximum value of the current flowing through the coil that can be allowed in the second mode, L is the self-inductance of the choke coil, Ts is the control period, Vin is the input voltage, and Vc Is the capacitive load voltage, and N is the turn ratio of the second coil to the first coil.   In the first mode, one of the first switching element and the second switching element is turned OFF during a first predetermined period, and the other of the first switching element and the second switching element is set to the first predetermined element. The power converter according to any one of claims 1 to 3, wherein ON and OFF are alternately repeated in a period.   In the third mode, one of the first switching element and the second switching element is turned ON for a second predetermined period, and the other of the first switching element and the second switching element is set to the second predetermined element. 14. The power conversion device according to claim 1, wherein ON and OFF are alternately repeated during the period.   The accumulated value of the time during which the first switching element is turned on in the third predetermined period is equal to the accumulated value of the time during which the second switching element is turned on. The power conversion device according to any one of 14. A current detecting means for detecting a current value of the choke coil;
In each of the first mode and the third mode, the first switching element and the second switching element are controlled such that the detected current value becomes a command value that is a predetermined value. The power conversion device according to claim 1.   The power conversion device according to claim 16, wherein the command value in the third mode is larger than the command value in the first mode. A current detecting means for detecting a current value of the choke coil;
In the first mode, the second mode, and the third mode, the first switching element and the second switching are set so that the detected current value becomes a command value that is a predetermined value, respectively. The power converter according to claim 2, wherein an element is controlled.   The power conversion device according to claim 18, wherein the command value in the third mode is larger than the command value in the first mode and the command value in the second mode.   In the second mode, by making one ON period of the first switching element and the second switching element constant and changing the other ON period of the first switching element and the second switching element, The power conversion device according to claim 18 or 19, wherein control is performed so that the current value becomes the command value.   21. The duty value of the switching element in which the ON period is constant among the first switching element and the second switching element in the second mode is 50% or less. Power converter.   In the second mode, control is performed so that the current value at the timing when both the first switching element and the second switching element are turned OFF becomes the command value. The power converter of any one of Claims. A slope compensator for adding a slope signal that is a sawtooth wave to the current value;
The slope compensator does not add the slope signal in the first mode and the second mode, but adds the slope signal in the third mode. The power converter according to item.   The power converter according to any one of claims 16 to 23, wherein in each of the modes, peak current control is performed so that the current value becomes the command value.

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