WO2020070789A1

WO2020070789A1 - Power conversion device

Info

Publication number: WO2020070789A1
Application number: PCT/JP2018/036807
Authority: WO
Inventors: 編絹中林; 竹島　由浩; 大斗水谷; 岩蕗　寛康
Original assignee: 三菱電機株式会社
Priority date: 2018-10-02
Filing date: 2018-10-02
Publication date: 2020-04-09
Also published as: JPWO2020070789A1; JP6937939B2

Abstract

A power conversion unit (2) is provided with: a transformer (6); a switching circuit (7) which includes switching elements (Q1, Q4) for applying positive voltage and switching elements (Q2, Q3) for applying negative voltage, and which is connected to the primary side of the transformer (6); and a rectification circuit (8) which is connected to the secondary side of the transformer (6). A control unit (3) generates a duty ratio and controls a first detection value (V2A) obtained by detection of output voltage, and further, performs detection at two second timings at a half period interval in each driving period, detects a magnetic asymmetry on the basis of the difference between the two second detection values (V2B1, V2B2), and separately corrects the duty ratios of the switching elements (Q1, Q4) and the switching elements (Q2, Q3) so as to suppress the magnetic asymmetry.

Description

Power converter

The present application relates to a power converter, and more particularly to a power converter having a transformer to which positive and negative voltages are applied.

In an isolated DC-DC converter, which is a power converter including a transformer to which positive and negative voltages are applied, if the voltage-time product of the positive and negative voltages applied to the transformer is different, the transformer is magnetized, and the power conversion function is impaired. It is known that
In the conventional power converter, two rectifiers for rectifying the secondary voltages Vs1 and Vs2 output from the secondary terminals of the transformer, and each DC voltage rectified by the two rectifiers are integrated individually and with time. And an integrator for outputting the two voltage-time products obtained as follows. By controlling the deviation between the two voltage-time products to be zero, the magnetic bias of the transformer is suppressed (for example, Patent Document 1).

JP 2013-55858 A

(4) In the above-described conventional power converter, the transformer demagnetization is detected by detecting the secondary voltages Vs1 and Vs2 of the transformer and obtaining a product of two voltage times. For this reason, two voltage detecting units and two integrating units are required, and the secondary winding of the transformer is limited to the center tap type. For this reason, there is a problem that it is difficult to reduce the size of the device configuration and the degree of freedom in design is small.

The present application discloses a technique for solving the above-described problem, and can reliably suppress the transformer's magnetization, and can reduce the size of the device configuration and improve the design flexibility. An object is to provide a power converter.

The power conversion device disclosed in the present application includes a transformer, a first semiconductor switching element that applies a positive voltage to the transformer when turned on, and a second semiconductor switching element that applies a negative voltage to the transformer when turned on. A switching circuit connected between the primary side of the transformer and the DC power supply to convert power between DC / AC, and a rectifier diode, a smoothing reactor, and a smoothing capacitor; And a power converter for converting the power from the DC power supply to supply the power to the load, and a controller for controlling the output of the power converter. The control unit generates a duty ratio of the first and second semiconductor switching elements so that a first detection value obtained by detecting an output voltage of the rectifier circuit at a first timing follows a command value. A voltage control unit that controls a second switching element; and a biasing unit that detects biasing of the transformer and individually corrects the duty ratios of the first and second semiconductor switching devices so as to suppress the biasing. A control unit. Then, the demagnetization control unit detects at least one of the output voltage of the rectifier circuit and the current of the smoothing reactor at two second timings at a half cycle interval in each cycle of the drive cycle, and The magnetic field is detected based on the difference between the second detection values.

According to the power conversion device disclosed in the present application, it is possible to reliably suppress the demagnetization of the transformer, reduce the size of the device configuration, and improve the design flexibility.

FIG. 1 is a diagram illustrating a schematic configuration of a power conversion device according to a first embodiment. FIG. 3 is a functional block diagram of a control unit of the power conversion device according to the first embodiment. FIG. 4 is a diagram illustrating generation of a gate drive signal according to the first embodiment. FIG. 3 is an operation waveform diagram for describing an operation in a normal state in the power conversion device according to the first embodiment. 5 is a flowchart for explaining the operation of the magnetization control unit according to the first embodiment. FIG. 5 is an operation waveform diagram for describing an operation when a magnetic bias occurs in the power converter according to the first embodiment. FIG. 5 is an operation waveform diagram for describing an operation when a magnetic bias occurs in the power converter according to the first embodiment. FIG. 5 is a functional block diagram of a control unit according to another example of the first embodiment. FIG. 7 is a diagram illustrating a schematic configuration of a power conversion device according to a second embodiment. FIG. 13 is a diagram illustrating a schematic configuration of a power conversion device according to a third embodiment. FIG. 13 is a functional block diagram of a control unit of the power conversion device according to the third embodiment. FIG. 13 is an operation waveform diagram for describing an operation in a normal state in the power conversion device according to the third embodiment. 13 is a flowchart for explaining the operation of the magnetization control unit according to the third embodiment. FIG. 13 is an operation waveform diagram for describing an operation of the power conversion device according to the third embodiment when a magnetic bias occurs. FIG. 13 is an operation waveform diagram for describing an operation of the power conversion device according to the third embodiment when a magnetic bias occurs. FIG. 15 is an operation waveform diagram for describing an operation at a normal time in the power conversion device according to the fourth embodiment. FIG. 13 is an operation waveform diagram for describing an operation of the power conversion device according to the fourth embodiment when a magnetic bias occurs. FIG. 13 is an operation waveform diagram for describing an operation of the power conversion device according to the fourth embodiment when a magnetic bias occurs.

Embodiment 1 FIG.
FIG. 1 is a diagram illustrating a schematic configuration of the power conversion device according to the first embodiment.
As shown in FIG. 1, the power conversion device 1 includes a power conversion unit 2 and a control unit 3 that controls the output of the power conversion unit 2 to convert DC power (voltage V1) from a DC power supply 4 into power. To supply DC power (voltage V2) to the load 5.
The power converter 2 includes a transformer 6, a switching circuit 7 connected between the primary side of the transformer 6 and the DC power supply 4 and performing power conversion between DC / AC, and a secondary circuit of the transformer 6 and the load 5. And a rectifier circuit 8 connected therebetween.

The switching circuit 7 includes an input capacitor 9, a MOSFET Q1 as a first semiconductor switching element that applies a positive voltage to the transformer 6 when turned on, a MOSFET Q4, and a MOSFET Q2 as a second semiconductor switching element that applies a negative voltage to the transformer 6 when turned on. MOSFET Q3. In this case, a full bridge circuit is formed by the four MOSFETs Q1 to Q4, but is not limited to this.
Hereinafter, the MOSFETs Q1, Q2, Q3, and Q4 are simply referred to as Q1, Q2, Q3, and Q4.

(4) The positive electrode of the input capacitor 9 is connected to the drain terminals of Q1 and Q3, and the negative electrode of the input capacitor 9 is connected to the source terminals of Q2 and Q4. The source terminal of Q1 is connected to the drain terminal of Q2, and the connection point is connected to the primary terminal 6a of the transformer 6. The source terminal of Q3 is connected to the drain terminal of Q4, and the connection point is connected to the primary terminal 6b of the transformer 6.

The rectifier circuit 8 includes two

rectifier diodes

10 and 11, a smoothing reactor 12, and a smoothing capacitor 13.
The transformer 6 has a center tap type secondary winding and three secondary terminals 6c, 6d, 6e. The secondary terminal 6c of the transformer 6 is connected to the anode terminal of the rectifier diode 10, and the secondary terminal 6e of the transformer 6 is connected to the anode terminal of the rectifier diode 11. Each cathode terminal of the

rectifier diodes

10 and 11 is connected to one end of a smoothing reactor 12, and the other end of the smoothing reactor 12 is connected to one end of a smoothing capacitor 13. The other end of the smoothing capacitor 13 is connected to a secondary terminal 6d of the transformer 6.

The power conversion device 1 further includes a voltage detection unit 20 that detects the output voltage V2 of the rectifier circuit 8. The voltage detector 20 detects the voltage of the smoothing capacitor 13 as the output voltage V2 of the rectifier circuit 8.
The control unit 3 includes a voltage control unit 14 and a demagnetization control unit 15, generates a gate drive signal for Q 1 to Q 4 in the switching circuit 7 based on the output of the voltage detection unit 20, and controls the power conversion unit 2. Output control.

FIG. 2 is a functional block diagram of the control unit 3.
As shown in FIG. 2, the control unit 3 includes a voltage control unit 14, a magnetization control unit 15, a correction unit 16, and a gate drive signal generation unit 17. The voltage control unit 14 detects the output voltage V2 of the rectifier circuit 8 at a first timing described below, acquires a first detection value V2A, and inputs the first detection value V2A to the feedback calculation unit 141. The feedback calculation unit 141 generates the duty ratio D such that the first detection value V2A follows the command value V2 * that is a constant voltage.

(4) The bias control unit 15 detects the output voltage V2 of the rectifier circuit 8 at two second timings, which will be described later, obtains two second detection values V2B1 and V2B2, and inputs the values to the feedback calculation unit 151. The feedback calculation unit 151 generates the correction amounts αa and αb such that the difference between the two second detection values V2B1 and V2B2 approaches zero. For example, the control amount α is calculated so that the difference between the two second detection values V2B1 and V2B2 approaches 0, and the correction amounts αa and αb are (α / 2, −α / 2) or (α, 0). And so on, so that the difference between the two correction amounts αa and αb becomes α.

出力 The output of the voltage control unit 14 and the output of the magnetization control unit 15 are input to the correction unit 16. The correction unit 16 includes two

adders

16a and 16b. The duty ratio D is corrected by adding the correction amount αa by the adder 16a, and the duty ratio D1 of Q1 and Q4 is generated. At the same time, the duty ratio D is corrected by adding the correction amount αb by the adder 16b, and the duty ratio D2 of Q2 and Q3 is generated.

The gate drive signal generator 17 includes

comparators

171 and 172. The comparator 171 receives the duty ratio D1 and the carrier wave Ca1, and outputs a gate drive signal G1 to Q1 and Q4 by PWM (pulse width modulation) control. Further, the duty ratio D2 and the carrier wave Ca2 are input to the comparator 172, and the comparator 172 outputs a gate drive signal G2 to Q2 and Q3 by PWM control.

FIG. 3 is a diagram illustrating generation of the gate drive signals G1 and G2. As shown in FIG. 3, the gate drive signals G1 and G2 are generated by comparing the duty ratios D1 and D2 with the carrier waves Ca1 and Ca2. The two carrier waves Ca1 and Ca2 have the same waveform with the phase shifted by a half cycle T / 2.

FIG. 4 is an operation waveform diagram for explaining a normal operation of power conversion device 1. In this case, the correction amounts αa and αb output by the bias control unit 15 are 0, and the gate drive signals G1 and G2 are generated based on the duty ratio D generated by the voltage control unit 14.
FIG. 4 shows the on / off signals of Q1 and Q4, the on / off signals of Q2 and Q3, the primary voltage Vtr of the transformer 6, the current IL of the smoothing reactor 12, the current IC of the smoothing capacitor 13, and the output voltage V2. Show. The on / off signals of Q1 and Q4 and the on / off signals of Q2 and Q3 are signals indicating the timing of actually turning on / off and applying a voltage to the transformer 6, and are not necessarily the gate drive signals G1 and G2 generated by the control unit 3. They do not match. In FIG. 4, the on / off signals of Q1 and Q4 and the on / off signals of Q2 and Q3 coincide with the gate drive signals G1 and G2 in order to show a normal state in which no magnetic demagnetization of the transformer 6 occurs.

As shown in FIG. 4, while Q1 and Q4 are on, the primary voltage Vtr is positive, while Q2 and Q3 are on, the primary voltage Vtr is negative, and accordingly, the current IL, the current IC, and the output voltage The ripple component of V2 fluctuates.
The above-described first detection value V2A is detected at a first timing when the output voltage V2 becomes an average value of one cycle, for example, at a phase 0 (t0) and a phase π (t01), every half cycle or every cycle. In this case, the timing at which Q1 and Q4 are turned on is set to phase 0 and the first timings t0 and t01.

The two second detection values V2B1 and V2B2 are detected at two second timings t1 and t2 at which the ripple voltage of the output voltage V2 becomes maximum. These two second timings t1 and t2 are half-period intervals in each cycle, and are the center of the entire off-period in which both Q1 and Q4 and Q2 and Q3 are off.
The second timings t1 and t2 in each cycle are represented by the following equations (1) and (2). The ON times of Q1 and Q4 and the ON times of Q2 and Q3 are the same ton, and T is a drive cycle.

t1 = ton + (T / 2−ton) / 2
= (T / 2 + ton) / 2 (1)
t2 = (3T / 2-ton) / 2 (2)

(4) The magnetization control unit 15 determines the second timings t1 and t2 based on the gate drive signals G1 and G2 at the duty ratio D, that is, based on the calculation result of the voltage control unit 14. Then, by sampling the output of the voltage detection unit 20 at the second timings t1 and t2, two second detection values V2B1 and V2B2 are obtained.

FIG. 5 is a flowchart illustrating the operation of the magnetization control unit 15.
As shown in FIG. 5, the magnetization control unit 15 determines whether or not a difference (V2B1−V2B2) between the two second detection values V2B1 and V2B2 detected at the second timings t1 and t2 is zero. (Step S1).
If (V2B1−V2B2) is 0, it is determined that no magnetic bias has occurred in the transformer 6, and the correction amounts αa and αb are both set to 0 (step S2). Thereby, in the control unit 3, the gate drive signals G1 and G2 are generated based on the duty ratio D generated by the voltage control unit 14, and the normal voltage control is continued.

If (V2B1-V2B2) is not 0 in step S1, it is determined whether (V2B1-V2B2) is positive (step S3).
If (V2B1−V2B2) is positive, it is determined that the transformer 6 has a negative magnetic bias, and the correction amounts αa and αb satisfying αa> 0 and αb <0 are determined (step S4). Thus, the control unit 3 generates the gate drive signal G1 based on the duty ratio D1 larger than the duty ratio D generated by the voltage control unit 14, and generates the gate drive signal G2 based on the duty ratio D2 smaller than the duty ratio D. Is done. Then, the on-time of Q1 and Q4 is adjusted to be long, and the on-time of Q2 and Q3 is adjusted to be short, so that the negative-side magnetization is suppressed.

If (V2B1−V2B2) is not positive in step S3, (V2B1−V2B2) is negative and it is determined that the transformer 6 has a positive-side magnetization, and αa <0 and αb> 0. The correction amounts αa and αb are determined (step S5). Thus, the control unit 3 generates the gate drive signal G1 based on the duty ratio D1 smaller than the duty ratio D generated by the voltage control unit 14, and generates the gate drive signal G2 based on the duty ratio D2 larger than the duty ratio D. Is done. Then, the on-time of Q1 and Q4 is adjusted to be short, and the on-time of Q2 and Q3 is adjusted to be long, so that the positive-side demagnetization is suppressed.

In steps S4 and S5, the two correction amounts αa and αb are determined to have polarities opposite to each other, but one of them may be set to 0 as described above.

FIGS. 6 and 7 are operation waveform diagrams for explaining the operation of the power conversion device 1 at the time of occurrence of magnetic polarization. In particular, FIG. The operation of FIG. The case where the correction amount αa is set to 0 and the control amount α is applied only to the duty ratio D2 is shown.
As shown in FIG. 6, when the gate drive signals G1 and G2 are generated based on the duty ratio D generated by the voltage control unit 14, and the voltage control in the normal state is performed, the switching timing is changed for some reason. It is assumed that positive side magnetization has occurred due to deviation or the like. In this case, the on-time of Q2 and Q3 is shortened, and the output voltage V2 detected at the second timing t1 and t2 is such that the value (V2B2) at the second timing t2 after Q2 and Q3 are turned on is Q1 and Q4. Becomes higher than the value (V2B1) at the second timing t1 after turning on.

(4) At the second timing t2 after the occurrence of the magnetization, the difference (V2B1−V2B2) between the two second detection values becomes negative, and the magnetization is detected. Then, the correction amounts αa and αb are generated so that the magnetization is suppressed, the duty ratio D1 of Q1 and Q4 and the duty ratio D2 of Q2 and Q3 are individually generated, and the magnetization suppression control is started. . In this case, since the control amount α is applied only to the duty ratio D2, the on-time of Q1 and Q4 does not change, and the on-time of Q2 and Q3 is adjusted to be longer, and the positive-side magnetization is suppressed. Is done.

Further, as shown in FIG. 7, it is assumed that a negative-side demagnetization occurs during the normal voltage control. In this case, the on-time of Q2 and Q3 becomes longer, and the output voltage V2 detected at the second timing t1 and t2 is such that the value (V2B2) at the second timing t2 after Q2 and Q3 are turned on is Q1 and Q4. Becomes lower than the value (V2B1) at the second timing t1 after turning on.

にて At the second timing t2 after the occurrence of the magnetic bias, the difference (V2B1−V2B2) between the two second detection values becomes positive, and the magnetic bias is detected. Then, the correction amounts αa and αb are generated so that the magnetization is suppressed, the duty ratio D1 of Q1 and Q4 and the duty ratio D2 of Q2 and Q3 are individually generated, and the magnetization suppression control is started. . In this case, since the control amount α is applied only to the duty ratio D2, the on-time of Q1 and Q4 does not change, and the on-time of Q2 and Q3 is adjusted to be shorter, and the negative-side demagnetization is suppressed. Is done.

Note that, even when the magnetic field is deflected, the second timings t1 and t2 are timings determined by ton based on the duty ratio D, and the second detection values (V2B1, V2B2) are detected as in the normal case. The two second timings t1 and t2 are timings at which the ripple voltage of the output voltage V2 becomes the maximum in the normal state, and the ripple voltage of the output voltage V2 does not always become the maximum when the demagnetization occurs.

As described above, in this embodiment, the bias control unit 15 detects the output voltage V2 of the rectifier circuit 8 at two second timings t1 and t2 at half cycle intervals in each cycle of the drive cycle T. Then, the magnetic bias of the transformer 6 is detected based on the difference between the two second detection values V2B1 and V2B2. Then, feedback control is performed so that the difference between the two second detection values V2B1 and V2B2 is reduced, and the duty ratio D1 of Q1 and Q4 and the duty ratio D2 of Q2 and Q3 are individually corrected and generated.
For this reason, it is possible to acquire the two second detection values V2B1 and V2B2 by using the voltage detection unit 20 used for the voltage control in the normal state, and to detect the magnetization of the transformer 6 as described in the related art. It does not require a voltage detection unit and an integration unit for detecting magnetic bias. For this reason, it is possible to reduce the size of the device configuration and reliably suppress the magnetic bias of the transformer 6.
Further, since it is not necessary to separately detect positive and negative voltages on the secondary side of the transformer 6, it is not necessary to limit the secondary winding of the transformer to the center tap type, and the degree of freedom in design is improved.

偏 Furthermore, since the magnetization control unit 15 determines the second timings t1 and t2 based on the calculation result of the voltage control unit 14, it is possible to easily determine the optimal second timings t1 and t2 for the detection of the magnetization.

Further, in a power converter mounted on a vehicle that shifts power from a high-voltage battery to a low-voltage load, demands for downsizing are strict. However, when the power converter 1 according to the present embodiment is applied, downsizing is effectively achieved. Since the magnetization can be promoted and the magnetization can be suppressed with high reliability, a great effect can be obtained.

In the above-described embodiment, the duty ratio D is corrected using only the correction amounts αa and αb calculated by the feedback calculation unit 151. However, as shown in FIG. 8, feedforward control may be used together. In this case, the feedforward calculation unit 18 calculates the feedforward term αf such that the difference between the current integrals of the smoothing reactor 12 becomes 0 between the ON periods of Q1 and Q4 and the ON periods of Q2 and Q3. Specifically, the current values IL-t1, IL-t2, IL-t0, and IL-t01 of the smoothing reactor 12 at the second timings t1 and t2 and the timings t0 and t01 at the phases 0 and π, and the voltage control unit 14 Is calculated based on the duty ratio D generated by the following equation (3). Here, T is a driving cycle.

X = (IL-t0) + (IL-t1)
Assuming that Y = (IL-t01) + (IL-t2),
αf = ((Y−X) / (Y + X)) · D · T (3)

In this case, the demagnetization control unit 15a sets the correction amounts αa and αb to α / 2 and −α / 2, and adds the αf to α / 2 by the adder 152 to generate the duty ratio D1. (Α / 2 + αf) is generated, and αf is subtracted from −α / 2 by the subtracter 153 to generate a correction amount (−α / 2−αf) for generating the duty ratio D2.
When only one of the two correction amounts αa and αb generated by the feedback calculation unit 151 is used and the other is set to 0, the feedforward term αf is also doubled and only one of addition and subtraction is used.

In this way, the feedforward term αf calculated so that the difference between the integrated values of the currents IL between the on-periods of Q1 and Q4 and the on-periods of Q2 and Q3 becomes zero, and the correction amounts αa and αb which are feedback terms. Synthesized. As a result, the amount of correction for generating the duty ratios D1 and D2 can be reduced, and the time required for suppressing the magnetic bias can be shortened.

Also, in the above embodiment, the detection of magnetic declination is determined based on whether the difference between the two second detection values V2B1 and V2B2 is 0, but a dead zone may be provided depending on the detection accuracy.

Also, in the above-described embodiment, the case where the step-down converter is used for the power conversion unit 2 has been described, but any circuit system that can perform DC / DC conversion and controls the output voltage may be used.

Further, in the above-described embodiment, the MOSFET has been described as the semiconductor switching element. However, an IGBT (Insulated Gate Bipolar Transistor), a silicon carbide MOSFET, or a gallium nitride high electron mobility transistor (HEMT) may be used. The effect is obtained.

Further, in the above-described embodiment, a triangular wave is used for the carrier waves Ca1 and Ca2, but a sawtooth wave or an inverse sawtooth wave may be used, and the same effect is obtained.

In the above-described embodiment, the two second timings t1 and t2 at half-cycle intervals are represented by the above equations (1) and (2). However, the present invention is not limited to this. In this case, the timing may be two times at half cycle intervals in each cycle. In that case, the calculation results of the voltage control unit 14 need not be used for generating the second timings t1 and t2.
Furthermore, a plurality of pairs of the second timings t1 and t2 at two half-cycle intervals may be provided in one cycle, and the accuracy of the detection of the demagnetization can be improved.

Embodiment 2 FIG.
FIG. 9 is a diagram illustrating a schematic configuration of the power conversion device according to the first embodiment.
As shown in FIG. 9, the power conversion device 1a includes a power conversion unit 2a and a control unit 3 that controls the output of the power conversion unit 2a, and converts the DC power (voltage V1) from the DC power supply 4 into power. To supply DC power (voltage V2) to the load 5.
The power conversion unit 2 a includes a transformer 6, a switching circuit 7 connected between the primary side of the transformer 6 and the DC power supply 4 and performing power conversion between DC / AC, and a secondary circuit of the transformer 6 and the load 5. And a rectifier circuit 8a connected therebetween.

In the first embodiment, the secondary winding of the transformer 6 is a center tap type having three secondary terminals 6c, 6d, and 6e. In the second embodiment, the secondary winding of the transformer 6 is There are only two side terminals 6c and 6e at both ends of the secondary winding. The rectifier circuit 8a includes a full bridge circuit including four

rectifier diodes

10a, 10b, 11a, and 11b, a smoothing reactor 12, and a smoothing capacitor 13. Other configurations are the same as those in the first embodiment.
In this case, when the secondary voltage of the transformer 6 is positive, current flows through the

rectifier diodes

10a and 10b, and when the secondary voltage of the transformer 6 is negative, current flows through the

rectifier diodes

11a and 11b. In addition, during the period when the secondary voltage of the transformer 6 is zero, that is, when there is no power transmission, a return current flows with all the

rectifier diodes

10a, 10b, 11a, and 11b in a forward bias state.

In the power converter 1a according to the second embodiment, the configuration and operation of the control unit 3 are the same as those in the first embodiment, and the same effects can be obtained. That is, the bias control section 15 detects the output voltage V2 of the rectifier circuit 8a at two second timings t1 and t2 at half cycle intervals in each cycle of the driving cycle T, and the two second detections are performed. The magnetic bias of the transformer 6 is detected based on the difference between the values V2B1 and V2B2. Then, feedback control is performed so that the difference between the two second detection values V2B1 and V2B2 is reduced, and the duty ratio D1 of Q1 and Q4 and the duty ratio D2 of Q2 and Q3 are individually corrected and generated.
For this reason, the two second detection values V2B1 and V2B2 can be acquired by using the voltage detection unit 20 used for the voltage control at the time of normal operation, and the magnetic bias of the transformer 6 can be detected, as described in the related art. It does not require a voltage detection unit and an integration unit for detecting magnetic bias. For this reason, it is possible to reduce the size of the device configuration and reliably suppress the magnetic bias of the transformer 6.

In this case, also in this case, the feedforward control may be used together with the feedback control. That is, the feedforward term αf is calculated and used so that the difference between the current integrated values of the smoothing reactor 12 becomes 0 between the ON periods of Q1 and Q4 and the ON periods of Q2 and Q3. As a result, the time required for suppressing the magnetization can be shortened.

Embodiment 3 FIG.
FIG. 10 is a diagram illustrating a schematic configuration of a power conversion device according to the third embodiment.
As shown in FIG. 10, the power conversion device 1 b includes a power conversion unit 2 similar to that of the first embodiment and a control unit 3 a that controls the output of the power conversion unit 2. The voltage V <b> 1) is converted into electric power, and DC power (voltage V <b> 2) is supplied to the load 5.
Power conversion device 1b includes a voltage detection unit 20 for detecting the voltage (output voltage V2) of smoothing capacitor 13, and a current detection unit for detecting current IL of smoothing reactor 12, as in the first embodiment. 21.

The control unit 3a includes a voltage control unit 14 and a magnetization control unit 15b. Based on the output of the voltage detection unit 20, the control unit 3a generates a gate drive signal to Q1 to Q4 in the switching circuit 7 and controls the power conversion unit 2 to operate. Output control.
FIG. 11 is a functional block diagram of the control unit 3a.
As shown in FIG. 11, the control unit 3a includes a voltage control unit 14, a magnetization control unit 15b, a correction unit 16, and a gate drive signal generation unit 17. The configuration other than the magnetization control unit 15b is the same as that of the above-described first embodiment, and thus the description will be appropriately omitted.

(4) The demagnetization control unit 15b detects the current IL of the smoothing reactor 12 at two second timings t1a and t2a, acquires two second detection values IL1 and IL2, and inputs them to the feedback calculation unit 154. The feedback calculation unit 154 generates the correction amounts αaa and αbb such that the difference between the two second detection values IL1 and IL2 approaches zero. The determination of the correction amounts αaa and αbb is the same as in the first embodiment. For example, the control amount α is calculated so that the difference between the two second detection values IL1 and IL2 approaches 0, and the correction amounts αaa and αaaa are calculated. αbb is generated such that the difference between the two correction amounts αaa and αbb, such as (α / 2, −α / 2) or (α, 0), becomes α.

The output of the voltage control unit 14 and the output of the demagnetization control unit 15b are input to the correction unit 16, and the Duty ratio D is individually corrected by the two correction amounts αaa and αbb to obtain the duty ratio D1 of Q1 and Q4. The duty ratio D2 of Q2 and Q3 is generated.

FIG. 12 is an operation waveform diagram for describing a normal operation of power conversion device 1b. In this case, the correction amounts αaa and αbb output from the magnetization control unit 15b are 0, and the gate drive signals G1 and G2 are generated based on the duty ratio D generated by the voltage control unit 14. The operation waveform is the same as the operation waveform shown in FIG.
The first detection value V2A is detected at a first timing when the output voltage V2 becomes an average value of one cycle, for example, at a phase 0 (t0) and a phase π (t01) every half cycle or every cycle. In this case, the timing at which Q1 and Q4 are turned on is set to phase 0 and the first timings t0 and t01.

The two second detection values IL1 and IL2 are detected at two second timings t1a and t2a at which the ripple current of the current IL of the smoothing reactor 12 is maximized. These two second timings t1a and t2a are half-cycle intervals in each cycle, and are the timing when Q1 and Q4 turn off and the timing when Q2 and Q3 turn off.
The second timings t1a and t2a in each cycle are represented by the following equations (4) and (5). The ON times of Q1 and Q4 and the ON times of Q2 and Q3 are the same ton, and T is a drive cycle.

t1a = ton (4)
t2a = ton + T / 2 (5)

The magnetization control unit 15b determines the second timings t1a and t2a based on the gate drive signals G1 and G2 at the duty ratio D, that is, based on the calculation result of the voltage control unit 14. Then, by sampling the output of the current detection unit 21 at the second timings t1a and t2a, two second detection values IL1 and IL2 are obtained.

FIG. 13 is a flowchart illustrating the operation of the magnetization control unit 15b.
As illustrated in FIG. 13, the magnetization control unit 15b determines whether the difference (IL1−IL2) between the two second detection values IL1 and IL2 detected at the second timings t1a and t2a is 0. (Step SS1).
If (IL1−IL2) is 0, it is determined that no magnetic bias has occurred in the transformer 6, and the correction amounts αa and αb are both set to 0 (step SS2). Thereby, in the control unit 3a, the gate drive signals G1 and G2 are generated based on the duty ratio D generated by the voltage control unit 14, and the normal voltage control is continued.

If it is determined in step SS1 that (IL1−IL2) is not 0, it is determined that the transformer 6 is demagnetized. First, assuming the occurrence of the positive-side magnetization, correction amounts αaa and αbb satisfying αaa <0 and αbb> 0 are determined (step SS3). Thereby, in the control unit 3a, the gate drive signal G1 is generated based on the duty ratio D1 smaller than the duty ratio D generated by the voltage control unit 14, and the gate drive signal G2 is generated based on the duty ratio D2 larger than the duty ratio D. Is done. Then, the ON times of Q1 and Q4 are adjusted to be short, and the ON times of Q2 and Q3 are adjusted to be long.

Next, it is determined whether or not the absolute value of (IL1−IL2) has decreased. That is, it is determined whether or not the difference (IL1−IL2) between the two second detection values IL1 and IL2 approaches 0 to suppress the magnetization (step SS4).
When the absolute value of (IL1−IL2) decreases, the assumption (the occurrence of positive-side demagnetization) is determined to be valid, and the control for suppressing the positive-side demagnetization, ie, αaa <0, αbb> 0, is established. The control of the magnetic depolarization suppression using the correction amounts αaa and αbb is continued (step SS5).

In step SS4, when the absolute value of (IL1−IL2) increases without decreasing, it is determined that the transformer 6 has a negative-side bias, and the correction amounts αaa, αaa> 0 and αbb <0, αbb is determined (step SS6). Thereby, in the control unit 3a, the gate drive signal G1 is generated based on the duty ratio D1 larger than the duty ratio D generated by the voltage control unit 14, and the gate drive signal G2 is generated based on the duty ratio D2 smaller than the duty ratio D. Is done. Then, the on-time of Q1 and Q4 is adjusted to be long, and the on-time of Q2 and Q3 is adjusted to be short, so that the negative-side magnetization is suppressed.

Although the two correction amounts αaa and αbb are determined to have polarities opposite to each other, one of them may be set to 0 as described above.

FIGS. 14 and 15 are operation waveform diagrams for explaining the operation of the power conversion device 1b at the time of occurrence of magnetic polarization. In particular, FIG. The operation of FIG. 14 shows a case where the correction amount αaa is set to 0 and the control amount α is applied only to the duty ratio D2, and FIG. 15 shows a case where the correction amount αbb is set to 0 and the control amount α is applied only to the duty ratio D1.

As shown in FIG. 14, the gate drive signals G1 and G2 are generated based on the duty ratio D generated by the voltage control unit 14, and when the voltage control in the normal state is performed, the switching timing is changed for some reason. It is assumed that a negative side magnetization occurs due to a deviation or the like. In this case, the on-time of Q2 and Q3 is prolonged, and negative-side magnetic bias occurs. When the magnetic bias occurs, the current IL of the smoothing reactor 12 increases, and the current IL detected at the second timings t1a and t2a has a value (IL2) at the second timing t2a, which is late, at the second timing t1a. (IL1).

にて At the second timing t2a after the occurrence of the magnetization, the difference (IL1−IL2) between the two second detection values becomes a value other than 0, and the magnetization is detected. Then, as shown in FIG. 13, the correction amounts αaa and αbb in the direction in which the magnetization is suppressed are generated, and the duty ratio D1 of Q1 and Q4 and the duty ratio D2 of Q2 and Q3 are generated individually. The demagnetization suppression control is started. In this case, since the control amount α is applied only to the duty ratio D2, the on-time of Q1 and Q4 does not change, and the on-time of Q2 and Q3 is adjusted to be shorter, and the negative-side demagnetization is suppressed. Is done.

Further, as shown in FIG. 15, it is assumed that the positive-side magnetization has occurred during the normal voltage control. In this case, the on-time of Q1 and Q4 becomes long, and the positive side magnetization occurs, and current IL of smoothing reactor 12 increases. As for the current IL detected at the second timings t1a and t2a, the value (IL2) at the second timing t2a whose timing is later is higher than the value (IL1) at the second timing t1a.
At the second timing t2a after the occurrence of the magnetization, the difference (IL1−IL2) between the two second detection values becomes a value other than 0, and the magnetization is detected. Then, as shown in FIG. 13, the correction amounts αaa and αbb in the direction in which the magnetization is suppressed are generated, and the duty ratio D1 of Q1 and Q4 and the duty ratio D2 of Q2 and Q3 are generated individually. The demagnetization suppression control is started. In this case, since the control amount α is applied only to the duty ratio D1, the on-time of Q2 and Q3 does not change, and the on-time of Q1 and Q4 is adjusted so as to be shortened, thereby suppressing the positive-side demagnetization. Is done.

Also, even when the magnetic field is deflected, the second timings t1a and t2a are timings determined by ton based on the duty ratio D, and the second detection values (IL1 and IL2) are detected as in the normal case. The two second timings t1a and t2a are timings at which the ripple current of the current IL of the smoothing reactor 12 is maximized in a normal state, and the ripple current of the current IL is not always maximized when a magnetic demagnetization occurs.

As described above, in the present embodiment, the demagnetization control unit 15b detects the current IL of the smoothing reactor 12 at two second timings t1a and t2a at half-cycle intervals in each drive cycle T. , Based on the difference between the two second detection values IL1 and IL2. Then, feedback control is performed so that the difference between the two second detection values IL1 and IL2 is reduced, and the duty ratio D1 of Q1 and Q4 and the duty ratio D2 of Q2 and Q3 are individually corrected and generated.

As described above, the current detection unit 21 for detecting the current IL of the smoothing reactor 12 can be used to acquire the two second detection values IL1 and IL2 to detect the magnetic bias of the transformer 6. For this reason, it is not necessary to detect positive and negative voltages or currents for the detection of the magnetic polarization, and a detection unit and an integration unit for detecting the magnetic polarization are not required as shown in the related art. Therefore, as in the first embodiment, the size of the device can be reduced, and the bias of the transformer 6 can be suppressed with high reliability.
Further, since it is not necessary to individually detect positive and negative voltages or currents on the secondary side of the transformer 6, the secondary winding of the transformer need not be limited to the center tap type, and the degree of freedom in design is improved.

偏 Because the magnetization control unit 15b determines the second timings t1a and t2a based on the calculation result of the voltage control unit 14, it is possible to easily determine the optimal second timings t1a and t2a for detecting the magnetization.

Embodiment 4 FIG.
In the third embodiment, the two second timings t1a and t2a at half-cycle intervals are timings at which the ripple current of the current IL of the smoothing reactor 12 is maximized, but the present invention is not limited to this. In the fourth embodiment, the timing at which the ripple current of the current IL becomes minimum is defined as the second timings t1b and t2b. Other configurations are the same as those of the third embodiment, that is, the configuration of the power converter 1b shown in FIG. 10 and the configuration of the control unit 3a shown in FIG. 11 are the same as those of the third embodiment.

FIG. 16 is an operation waveform diagram for describing a normal operation of power conversion device 1b according to the present embodiment. In this case, the correction amounts αaa and αbb output from the magnetization control unit 15b are 0, and the gate drive signals G1 and G2 are generated based on the duty ratio D generated by the voltage control unit 14. The operation waveform is the same as the operation waveform shown in FIG.
The first detection value V2A is detected at a first timing t0, t01 at which the output voltage V2 becomes an average value of one cycle, and every half cycle or one cycle.

The two second detection values IL1 and IL2 are detected at two second timings t1b and t2b at which the ripple current of the current IL of the smoothing reactor 12 is minimized. The two second timings t1b and t2b are half-cycle intervals in each cycle, and are the timing when Q1 and Q4 turn on and the timing when Q2 and Q3 turn on.
In this case, the second timings t1b and t2b in each cycle are the same as the first timings t0 and t01, and are represented by the following equations (6) and (7). Note that T is a driving cycle.

t1b = 0 (6)
t2b = T / 2 (7)

In this case, the second timings t1b and t2b can be easily determined without using the calculation result of the voltage control unit 14. Then, by sampling the output of the current detection unit 21 at the second timings t1b and t2b, two second detection values IL1 and IL2 are obtained.
If the timings when Q1 and Q4 are turned on and the timings when Q2 and Q3 are turned on are not set to the phase 0 (t0) and the phase π (t01), the second timings t1b and t2b are set to the voltage control unit. The determination is made using the calculation results of No. 14.

(4) Then, based on the two second detection values IL1 and IL2 detected at the second timings t1b and t2b, the magnetization control unit 15b detects and suppresses the magnetization as in the third embodiment. That is, when the difference (IL1−IL2) between the two second detection values is other than 0, the magnetism is detected and the correction amounts αaa and αbb in the direction in which the magnetization is suppressed are generated, and the voltage control unit is controlled. 14 corrects the duty ratio D generated.

FIGS. 17 and 18 are operation waveform diagrams for explaining the operation of the power conversion device 1b at the time of occurrence of magnetic polarization. In particular, FIG. The operation of FIG. FIG. 17 shows a case where the correction amount αaa is 0 and the control amount α is applied only to the duty ratio D2, and FIG. 18 shows a case where the correction amount αbb is 0 and the control amount α is applied only to the duty ratio D1.

As shown in FIG. 17, when the gate drive signals G1 and G2 are generated based on the duty ratio D generated by the voltage control unit 14, and the voltage control in the normal state is performed, the switching timing may be changed for some reason. It is assumed that a negative side magnetization occurs due to a deviation or the like. In this case, the on-time of Q2 and Q3 is prolonged, and negative-side magnetic bias occurs. When the magnetic bias occurs, the current IL of the smoothing reactor 12 increases, and the current IL detected at the second timings t1b and t2b has a value (IL2) at the second timing t2b, which is late, at the second timing t1b. (IL1).

(4) At the second timing t2b after the occurrence of the magnetization, the difference (IL1−IL2) between the two second detection values becomes a value other than 0, and the magnetization is detected. Then, as shown in FIG. 13, the correction amounts αaa and αbb in the direction in which the magnetization is suppressed are generated, and the duty ratio D1 of Q1 and Q4 and the duty ratio D2 of Q2 and Q3 are generated individually. The demagnetization suppression control is started. In this case, since the control amount α is applied only to the duty ratio D2, the on-time of Q1 and Q4 does not change, and the on-time of Q2 and Q3 is adjusted to be shorter, and the negative-side demagnetization is suppressed. Is done.

Further, as shown in FIG. 18, it is assumed that the positive-side magnetization has occurred during the normal voltage control. In this case, the on-time of Q1 and Q4 becomes long, and the positive side magnetization occurs, and current IL of smoothing reactor 12 increases. In the current IL detected at the second timings t1b and t2b, the value (IL2) at the second timing t2b, which is late, becomes higher than the value (IL1) at the second timing t1b.
At the second timing t2b after the occurrence of the magnetization, the difference (IL1−IL2) between the two second detection values becomes a value other than 0, and the magnetization is detected. Then, as shown in FIG. 13, the correction amounts αaa and αbb in the direction in which the magnetization is suppressed are generated, and the duty ratio D1 of Q1 and Q4 and the duty ratio D2 of Q2 and Q3 are generated individually. The demagnetization suppression control is started. In this case, since the control amount α is applied only to the duty ratio D1, the on-time of Q2 and Q3 does not change, and the on-time of Q1 and Q4 is adjusted to be shorter, and the positive-side demagnetization is suppressed. Is done.

(4) Even when a magnetic bias occurs, the second timings t1b and t2b are the same as those in the normal state, and the second detection values (IL1 and IL2) are detected as in the normal state. The two second timings t1b and t2b are timings at which the ripple current of the current IL of the smoothing reactor 12 is minimized in a normal state, and the ripple current of the current IL is not necessarily minimized when a magnetic bias occurs.

As described above, also in this embodiment, as in the above-described third embodiment, two second detection values IL1 and IL2 are obtained using the current detection unit 21 that detects the current IL of the smoothing reactor 12. It is possible to detect the magnetic bias of the transformer 6. Therefore, the same effect as in the third embodiment can be obtained, the size of the device can be reduced, the bias of the transformer 6 can be suppressed with high reliability, and the degree of freedom in design can be improved.

In the third and fourth embodiments, the two second timings t1b and t2b at half-period intervals are timings at which the ripple current of the current IL of the smoothing reactor 12 is maximum or minimum, but is not limited to this. is not. The second timings t1b and t2b are only required to be able to detect a change in the ripple current of the current IL at two times at half cycle intervals in each cycle. In that case, the calculation results of the voltage control unit 14 need not be used for generating the second timings t1b and t2b.
Furthermore, a plurality of pairs of two second timings t1b and t2b at half-cycle intervals may be provided in one cycle, and the accuracy of the detection of magnetic declination can be improved.

Further, when the power converter 1b according to the third and fourth embodiments is applied to a vehicle-mounted power converter that transfers power from a high-voltage battery to a low-voltage load, it is possible to effectively promote downsizing, and to improve reliability. Since the magnetism can be suppressed, a great effect can be obtained.

Also, in the third and fourth embodiments, the detection of magnetic declination is determined based on whether the difference between the two second detection values IL1 and IL2 is 0, but a dead zone may be provided.

Although this application describes various exemplary embodiments and examples, the various features, aspects, and functions described in one or more embodiments may apply to particular embodiments. However, the present invention is not limited thereto, and can be applied to the embodiment alone or in various combinations.
Accordingly, innumerable modifications not illustrated are envisioned within the scope of the technology disclosed herein. For example, a case where at least one component is deformed, added or omitted, and a case where at least one component is extracted and combined with components of other embodiments are included.

1, 1a, 1b power converter, 2, 2a power converter, 3, 3a controller, 4 DC power supply, 5 load, 6 transformer, 7 switching circuit, 8, 8a rectifier circuit, 10, 11 rectifier diode, 10a, 10b, 11a, 11b rectifier diode, 12 smoothing reactor, 13 smoothing capacitor, 14 voltage control unit, 15, 15a, 15b demagnetization control unit, 18 feedforward operation unit, 20 voltage detection unit, 21 current detection unit, D, D1 , D2 Duty ratio, Q1, Q4 first semiconductor switching element, Q2, Q4 second semiconductor switching element, t0, t01 first timing, t1, t2 second timing, t1a, t2a second timing, t1b, t2b second timing , T drive cycle, αa, αb correction amount, αaa, αb Correction amount, .alpha.f feedforward term, V2A first detection value, V2B1, V2B2 second detection value, IL1, IL2 second detection value.

Claims

A first semiconductor switching element for applying a positive voltage to the transformer when the transformer is on, and a second semiconductor switching element for applying a negative voltage to the transformer when the transformer is on; And a rectifier circuit that has a rectifier diode, a smoothing reactor, and a smoothing capacitor and is connected between a secondary side of the transformer and a load. A power converter for converting the power from the DC power supply to supply the converted power to the load;
And a control unit that controls the output of the power conversion unit.
The control unit includes:
The first and second semiconductor switching elements are generated by generating a duty ratio of the first and second semiconductor switching elements such that a first detection value obtained by detecting an output voltage of the rectifier circuit at a first timing follows a command value. A voltage control unit for controlling
A polarization control unit configured to detect the magnetic polarization of the transformer and individually correct the Duty ratios of the first and second semiconductor switching elements so as to suppress the magnetic polarization;
The demagnetization control unit detects at least one of the output voltage of the rectifier circuit and the current of the smoothing reactor at two second timings at a half cycle interval in each cycle of the drive cycle, and A power converter for detecting the magnetic bias based on a difference between the second detection values.
The power converter according to claim 1, wherein the bias control unit determines the second timing based on a calculation result of the voltage control unit.
The voltage control unit acquires the first detection value at the first timing when the output voltage becomes an average value of one cycle,
3. The power converter according to claim 1, wherein the magnetization control unit detects the output voltage at a second timing different from the first timing and acquires the second detection value. 4.
The power converter according to claim 2, wherein the bias control unit detects the output voltage and obtains the second detection value at the second timing when the ripple voltage of the output voltage becomes maximum.
The said magnetization control part detects the said output voltage and acquires the said 2nd detection value at the said 2nd timing which is the center of the period when the said 1st, 2nd semiconductor switching element is all off. The power converter according to claim 2 or claim 4.
The said demagnetization control part detects the electric current of the said smoothing reactor at the said 2nd timing when the ripple current of the said smoothing reactor becomes the maximum or the minimum, and acquires the said 2nd detection value. 3. The power converter according to claim 1.
The said demagnetization control part detects the electric current of the said smoothing reactor at the 2nd timing which becomes the timing which turns on or off the said 1st, 2nd semiconductor switching element, and acquires the said 2nd detection value. The power converter according to any one of claims 1, 2, and 6.
The demagnetization control unit calculates a feedforward term so that a difference between a current integral value of the smoothing reactor becomes 0 between an ON period of the first semiconductor switching element and an ON period of the second semiconductor switching element. The power conversion device according to any one of claims 3 to 5, wherein the power conversion device is used by using.