WO2019171414A1

WO2019171414A1 - Dc/dc converter control device

Info

Publication number: WO2019171414A1
Application number: PCT/JP2018/008246
Authority: WO
Inventors: 裕介齋藤; 杉戸　健
Original assignee: 新電元工業株式会社
Priority date: 2018-03-05
Filing date: 2018-03-05
Publication date: 2019-09-12
Also published as: JPWO2019171414A1; JP6898511B2

Abstract

Provided is a control device 50 for a DC/DC converter 1 with which it is possible to cover a wide range of obtainable output power with low loss. The control device 50 has a count value calculation unit 51, a comparator unit 52, a frequency control unit 53, a phase shift control unit 54, and a pulse drive unit 55. When rapidly charging a battery, for example, a DC output current Io is supplied to the battery by frequency control performed by the frequency control unit 53. Upon entering a power supply range less than or equal to the boundary of a current resonance control limit that serves as a reference value and is difficult to control, phase shift control performed by the phase shift control unit 54 is selected and the DC output current Io is supplied to the battery.

Description

Control device for DC / DC converter

The present invention is used in, for example, an EV quick charger, which is an in-vehicle charging device for rapidly charging a secondary battery (battery) mounted on an electric vehicle (hereinafter referred to as “EV”), and DC (direct current). The present invention relates to a control device for a DC / DC converter for converting a voltage into a desired DC voltage to rapidly charge a battery or the like.

Conventionally, for example, as a DC / DC converter for charging a battery, current resonant circuits such as a high-efficiency LLC circuit with low switching loss and the like are described in

Patent Documents

1 and 2 and the like.

A current resonance type circuit as a DC / DC converter includes, for example, a resonance inductor, a resonance capacitor, an exciting inductance of a transformer, and a switching element, and an output range can be determined by each parameter of a component.

JP 2012-249375 A JP 2013-243114 A

FIG. 6 is a diagram showing an example of output characteristics of the EV quick charger.

6, the horizontal axis represents the DC output current Io, and the vertical axis represents the DC output voltage Vo. A hatched area surrounded by points A, B, C, D, E, and F is an output possible power range Par of the EV quick charger. The EV quick charger requires a wide range of output characteristics due to the difference in battery voltage depending on the vehicle type.

For example, at point A in FIG. 6, the output current Io is 30 A and the output voltage Vo is 500 V, the point B is the output current Io is 33.3 A and the output voltage Vo is 450 V, and the point C is the output current Io is 38 A. This is a critical point where the voltage Vo is 395 V and the output power Po is 1501.0 W. Further, at point D, the output current Io is 38A and the output voltage Vo is 150V, at point E, the output current Io is 1A and the output voltage Vo is 150V, and at point F, the output current Io is 1A and the output voltage Vo is 500V. is there. The hatched area surrounded by these points A, B, C, D, E, and F is the output power range Par of the EV quick charger, and current control CC is required.

In a current resonance type circuit such as an LLC circuit, the output voltage Vo is decreased by increasing the switching frequency f of the switching element and the output voltage Vo is increased by decreasing the switching frequency f by frequency control. For this reason, when a conventional current resonance circuit is applied to an EV quick charger that requires a wide range of output characteristics, if the battery is to be charged with a low output voltage Vo of approximately 200 V to 150 V, the switching frequency f However, since the maximum allowable frequency is exceeded, it is difficult to charge the battery. Also, in order to realize a wide range of output characteristics, it is necessary to set parameters such that a reactive current that does not contribute to output power always flows through the excitation inductance. However, the reactive current causes a conduction loss in the route through which the reactive current flows (for example, the resonance capacitor → the switching element → the transformer primary winding → the resonance inductor → the current path of the resonance capacitor), and thus the loss cannot be reduced.

As described above, in the conventional current resonance type circuit, it is difficult to realize a DC / DC converter control device capable of covering a wide output possible power range Par with low loss.

According to the present invention, when a three-phase DC input voltage is supplied, the DC input voltage is switched by a plurality of switching elements that are turned on / off by a plurality of switching drive signals, respectively, and a three-phase AC (AC) voltage is switched A DC / AC conversion circuit that converts the three-phase resonance voltage to generate a three-phase resonance voltage by resonating with the three-phase AC voltage, and a three-phase conversion by converting the three-phase resonance voltage into a predetermined voltage A main circuit of a DC / DC converter comprising: a three-phase transformer that outputs a voltage; and a three-phase rectifier circuit that rectifies the three-phase conversion voltage and outputs a DC output current to a load. A control device for a DC / DC converter that supplies a plurality of switching drive signals.

The control device counts the DC output current, calculates the calculation value to obtain a calculation result, compares the calculation result with a reference value, and when the calculation result is larger than the reference value, The phase difference between the three phases in the AC voltage of the phase is set to an angle 2π / 3, and the frequency of the plurality of switching drive signals is changed by frequency control so that the desired DC output current is output from the rectifier circuit When the calculation result is smaller than the reference value, the frequency of the plurality of switching drive signals is set to the maximum value, and the desired DC output current is output from the rectifier circuit by phase shift control. The phase difference between the three phases is changed.

The control device, for example, counts the DC output current, calculates a count value to calculate the calculation result, compares the calculation result with the reference value, and the calculation result is A comparison unit that outputs a first comparison result when larger than a reference value, and outputs a second comparison result when the calculation result is smaller than the reference value, and the three-phase AC voltage based on the first comparison result The phase difference between the three phases is set to the angle 2π / 3, and the frequency of the plurality of switching drive signals is changed by the frequency control so that the desired DC output current is output from the rectifier circuit. And the frequency control unit to set the frequency of the plurality of switching drive signals to the maximum value based on the second comparison result, and the rectification by the phase shift control As it said desired DC output current from the road is output, and a, and the phase shift control unit for changing the phase difference between the three phases.

According to the DC / DC converter control device of the present invention, when the DC output current is supplied to the load by frequency control and the power supply region is smaller than the reference value that is difficult to control, the DC output current is switched to the phase shift control. Is supplied to the load. Therefore, a low-loss DC / DC converter that suppresses reactive current can be realized.

FIG. 1 is a schematic circuit diagram showing the entirety of a DC / DC converter in Embodiment 1 of the present invention. FIG. 2 is a block diagram showing a control device in the DC / DC converter of FIG. FIG. 3 is a diagram showing output characteristics of the EV quick charger in the first embodiment of the present invention. FIG. 4 is a flowchart showing the operation of the control device of FIG. FIG. 5 is a timing chart of the on / off operation in the switching element (for example, a field effect transistor, hereinafter referred to as “FET”) in FIG. FIG. 6 is a diagram showing output characteristics of a conventional EV quick charger.

The form for carrying out the present invention will become clear when the following description of the preferred embodiments is read with reference to the accompanying drawings. However, the drawings are only for explanation and do not limit the scope of the present invention.

(Configuration of Example 1)

FIG. 1 is a schematic circuit diagram showing the entire DC / DC converter in Embodiment 1 of the present invention.

The DC / DC converter 1 switches the three-phase (for example, U-phase, V-phase, W-phase) DC input voltages Viu, Viv, Viw and converts them into a predetermined DC output voltage Vo and DC output current Io. Main circuit 2 and a control device 50 for controlling the switching operation of the main circuit 2.

The main circuit 2 includes three-phase DC / AC conversion circuits 10U, 10V, and 10W. The three-phase DC / AC conversion circuits 10U, 10V, and 10W are circuits that switch the three-phase DC input voltages Viu, Viv, and Viw, respectively, to convert them into three-phase AC voltages, and each phase is the same circuit. It is configured.

The U-phase DC / AC conversion circuit 10U includes a plurality of switching elements (for example, FETs) 11U, 12U, 13U, and 14U that are turned on / off by a plurality of switching drive signals S11U, S12U, S13U, and S14U, respectively. These

FETs

11U, 12U, 13U, and 14U are bridge-connected. A parasitic diode 15 that is a body diode is connected in antiparallel between the source and drain of each of the

FETs

11U, 12U, 13U, and 14U.

Similarly, the V-phase DC / AC conversion circuit 10V includes a plurality of switching elements (for example, FETs) 11V, 12V, 13V, and 14V that are turned on / off by a plurality of switching drive signals S11V, S12V, S13V, and S14V, respectively. These

FETs

11V, 12V, 13V, and 14V are bridge-connected. Parasitic diodes 15 are connected in antiparallel between the sources and drains of the

FETs

11V, 12V, 13V, and 14V, respectively.

Further, the W-phase DC / AC conversion circuit 10W includes a plurality of switching elements (eg, FETs) 11W, 12W, 13W, and 14W that are turned on / off by a plurality of switching drive signals S11W, S12W, S13W, and S14W, respectively. These

FETs

11W, 12W, 13W, and 14W are bridge-connected. Parasitic diodes 15 are connected in antiparallel between the sources and drains of the

FETs

11W, 12W, 13W, and 14W, respectively.

Three-

phase resonance circuits

20U, 20V, and 20W are connected to the output sides of the three-phase DC / AC conversion circuits 10U, 10V, and 10W. The three-

phase resonance circuits

20U, 20V, and 20W are circuits that resonate with the three-phase AC voltage output from the three-phase DC / AC conversion circuits 10U, 10V, and 10W to generate a three-phase resonance voltage. Each phase is composed of the same circuit.

The U-phase resonance circuit 20U is constituted by a current resonance type circuit having a resonance capacitor 21U, a resonance inductor 22U, and an excitation inductor 23U. The resonant capacitor 21U, the resonant inductor 22U, and the exciting inductor 23U are connected in series between a connection point between the FET 11U and the FET 12U and a connection point between the FET 13U and the FET 14U.

Similarly, the V-phase resonance circuit 20V is constituted by a current resonance circuit having a resonance capacitor 21V, a resonance inductor 22V, and an excitation inductor 23V. The resonant capacitor 21V, the resonant inductor 22V, and the exciting inductor 23V are connected in series between a connection point between the FET 11V and the FET 12V and a connection point between the FET 13V and the FET 14V.

Further, the W-phase resonance circuit 20W is constituted by a current resonance circuit having a resonance capacitor 21W, a resonance inductor 22W, and an excitation inductor 23W. The resonant capacitor 21W, the resonant inductor 22W, and the exciting inductor 23W are connected in series between a connection point between the FET 11W and the FET 12W and a connection point between the FET 13W and the FET 14W.

Three-

phase transformers

30U, 30V, 30W are connected to the output sides of the three-

phase resonance circuits

20U, 20V, 20W. The three-

phase transformers

30U, 30V, and 30W convert the three-phase resonance voltage output from the three-

phase resonance circuits

20U, 20V, and 20W into a predetermined voltage and output a three-phase conversion voltage. Each phase has the same configuration.

The U-phase transformer 30U has a primary winding 31U and a secondary winding 32U. The winding start side (black dot in FIG. 1) of the primary winding 31U is connected to the resonant inductor 20U, and the winding end side of the primary winding 31U is connected to the connection point between the

FETs

13U and 14U. . Similarly, the V-phase transformer 30V has a primary winding 31V and a secondary winding 32V, and the winding start side of the primary winding 31V is connected to the resonant inductor 20V, and the primary winding 31V. Is connected to the connection point between the

FETs

13V and 14V. Further, the W-phase transformer 30W has a primary winding 31W and a secondary winding 32W, and the winding start side of the primary winding 31W is connected to the resonant inductor 20W, and the primary winding 31W The winding end side is connected to a connection point between the

FETs

13W and 14W.

A three-phase rectifier circuit 40 is connected to the three-phase

secondary windings

32U, 32V, and 32W. The three-phase rectifier circuit 40 is a circuit that rectifies the three-phase conversion voltage converted by the three-

phase transformers

30U, 30V, and 30W and outputs the DC output voltage Vo and the DC output current Io to the load 48. The three-phase rectifier circuit 40 includes a rectifier unit in which a plurality of (for example, six) rectifier elements (for example,

diodes

41, 42, 43, 44, 45, and 46) are bridge-connected, an output voltage of the rectifier unit, and And a smoothing section (for example, a smoothing capacitor 47) that smoothes the output current.

In order to control the switching operation of the main circuit 2, the control device 50 includes a plurality of (for example, 12) switching drive signals S11U, S12U, S13U, S14U, S11V, S12V, S13V, S14V, S11W, S12W, S13W, This device supplies S14W to the gates of

FETs

11U, 12U, 13U, 14U, 11V, 12V, 13V, 14V, 11W, 12W, 13W, and 14W in the main circuit 2.

FIG. 2 is a block diagram showing the control device 50 in the DC / DC converter 1 of FIG.

The control device 50 includes a count value calculation unit 51, a comparison unit 52, a frequency control unit 53, a phase shift control unit 54, and a pulse drive unit 55. The count value calculation unit 51, the comparison unit 52, the frequency control unit 53, and the phase shift control unit 54 are configured by a processor having a central processing unit (CPU) capable of program control, or an individual circuit. The pulse driving unit 55 is configured by an individual circuit.

The count value calculation unit 51 counts the DC output current Io measured by a current measuring instrument (not shown), calculates the count value, and obtains a calculation result CV. The count value calculation unit 51 includes an analog / digital conversion unit (hereinafter referred to as “A / D conversion unit”) 51a that converts the measured DC output current Io into an output current value IO of a digital signal, and an output current value IO thereof. And a calculation unit 51b for calculating a calculation result CV. A comparison unit 52 is connected to the output side of the calculation unit 51b. The comparison unit 52 compares the calculation result CV with the reference value RV, and outputs the first comparison result CR1 to the frequency control unit 53 when the calculation result CV is larger than the reference value RV (CV ≧ RV). When the result CV is smaller than the reference value RV (CV <RV), the second comparison result CR2 is output to the phase shift control unit 54.

The frequency control unit 53 sets the phase difference φ between the U, V, and W phases in the three-phase AC voltage converted by the DC / AC conversion circuits 10U, 10V, and 10W based on the first comparison result CR1 to an angle 2π / 3 ( = 120 °) and a plurality of switching drive signals S11U, S12U, S13U, S14U, S11V, S12V, S13V, S14V, and the like so that a desired DC output current Io is output from the rectifier circuit 40 by frequency control. The switching frequency f of S11W, S12W, S13W, S14W is changed. The frequency control unit 53 includes a phase difference setting unit 53a that sets the phase difference φ between the U, V, and W phases to an angle 2π / 3 (= 120 °), and a frequency modulation (hereinafter referred to as “PFM”) connected to the output side. And a pulse generator 53b. The PFM pulse generation unit 53b modulates the switching frequency f of the plurality of switching drive signals S11U, S12U, S13U, S14U, S11V, S12V, S13V, S14V, S11W, S12W, S13W, and S14W by frequency control to generate the PFM pulse. P1 is generated, and a pulse driving unit 55 is connected to the output side.

Based on the second comparison result CR2, the phase shift control unit 54 determines the values of the switching frequencies f of the plurality of switching drive signals S11U, S12U, S13U, S14U, S11V, S12V, S13V, S14V, S11W, S12W, S13W, and S14W. The phase difference φ between the U, V, and W phases is fixed so that the maximum switching frequency fmax of the maximum value is fixed (that is, set), and the desired DC output current Io is output from the rectifier circuit 40 by phase shift control. It is something to change. The phase shift control unit 54 includes a frequency setting unit 54a that sets the switching frequency f of the switching drive signals S11U, S12U, S13U, S14U, S11V, S12V, S13V, S14V, S11W, S12W, S13W, and S14W to the maximum frequency fmax; And a phase shift control pulse generator 54b connected to the output side. The phase shift control pulse generator 54b generates a phase shift control pulse P2 by changing the phase difference φ between the U, V, and W phases by phase shift control. On the output side, the pulse driver 55 It is connected.

The pulse driving unit 55 generates a switching drive signal S11U, S12U, S13U, S14U, S11V, S12V, S13V, S14V, S11W, S12W, S13W, S14W by driving the PFM pulse P1 or the phase shift control pulse P2. There are individual circuits such as transistors.

(Operation of supplying power to a load whose voltage does not fluctuate)

In the DC / DC converter 1 of FIG. 1, the operation when a device whose voltage does not vary is used as the load 48 will be described.

For example, when supplying a constant DC output voltage Vo to the load 48, the frequency control unit 53 in the control device 50 sets the phase difference φ between the U, V, and W phases to 120 °, and by frequency control, A PFM pulse P1 is generated, and this PFM pulse P1 is output to the pulse driving unit 55. In frequency control, in order to perform constant voltage output, if the DC output voltage Vo becomes lower than the target voltage Vth, the switching frequency f is controlled by feedback control so that the error voltage ΔV (= Vth−Vo) becomes zero. The DC output voltage Vo is increased to reduce the switching frequency f by feedback control so that the error voltage ΔV (= Vth−Vo) becomes zero when the DC output voltage Vo becomes higher than the target voltage Vth. The PFM pulse P1 is generated by performing frequency modulation such that the DC output voltage Vo is increased to decrease the DC output voltage Vo. The pulse driver 55 drives the PFM pulse P1 to generate the switching drive signals S11U, S12U, S13U, S14U, S11V, S12V, S13V, S14V, S11W, S12W, S13W, S14W, and the U, V, W phase The voltage is applied to each gate of the

FETs

11U, 12U, 13U, 14U, 11V, 12V, 13V, 14V, 11W, 12W, 13W, and 14W in the DC / AC conversion circuits 10U, 10V, and 10W.

In the U-phase DC / AC conversion circuit 10U, the

FETs

11U, 14U and the

FETs

12U, 13U are alternately turned on / off with a predetermined dead time by the switching drive signals S11U, S12U, S13U, S14U. In the V-phase DC / AC conversion circuit 10V, the

FETs

11V, 14V and

FETs

12V, 14V are alternately delayed by 120 ° from the U-phase with a predetermined dead time by the switching drive signals S11V, S12V, S13V, S14V. Turns on / off. Further, in the W-phase DC / AC conversion circuit 10W, the switching drive signals S11W, S12W, S13W, and S14W cause the FETs 11W and 14W and the

FETs

12W and 13W to be delayed by 120 ° from the V phase and have a predetermined dead time. Turns on / off alternately.

In the U-phase DC / AC conversion circuit 10U, when the

FETs

11U and 14U are turned on and the

FETs

12U and 13U are turned off, the U-phase DC input voltage Viu causes the FET 11U → resonance capacitor 21U → resonance inductor 22U → excitation inductor 23U and A power supply current flows through the path of the primary winding 31U → the FET 14U → the DC input voltage Viu of the transformer 30U. When the

FETs

12U and 13U are turned on and the

FETs

11U and 14U are turned off after a predetermined dead time, the FET 13U → the exciting inductor 23U and the primary winding 31U of the transformer 30U → the resonant inductor 22U → the resonance by the DC input voltage Viu. A power supply current flows through the path of the capacitor 21U → FET 12U → DC input voltage Viu. Thereby, the DC input voltage Viu is converted into an AC voltage by the switching operation of the DC / AC conversion circuit 10U.

The resonant circuit 20U is resonated by the converted AC voltage to generate a resonant voltage, which is applied to the primary winding 31U of the transformer 30U. Then, a predetermined conversion voltage is induced in the secondary winding 32U of the transformer 30. The induced conversion voltage is rectified by a plurality of diodes 41-46 in the rectifier circuit 40, smoothed by the smoothing capacitor 47, and the DC output voltage Vo is supplied to the load 48.

Similarly, the V-phase DC / AC conversion circuit 10V performs a switching operation with a 120 ° delay from the U-phase, and the V-phase DC input voltage Viv is converted into an AC voltage. By the converted AC voltage, the resonance circuit 20V resonates to generate a resonance voltage. The generated resonance voltage is converted into a predetermined voltage by the transformer 30V, rectified by the plurality of diodes 41-46 in the rectifier circuit 40, and then smoothed by the smoothing capacitor 47, and the DC output voltage Vo is applied to the load 48. Supplied to.

Further, the W-phase DC / AC conversion circuit 10W performs a switching operation with a 120 ° delay from the V-phase, and the W-phase DC input voltage Viw is converted into an AC voltage. Due to the converted AC voltage, the resonant circuit 20W resonates to generate a resonant voltage. The generated resonance voltage is converted into a predetermined voltage by the transformer 30W, rectified by the plurality of diodes 41-46 in the rectifier circuit 40, and then smoothed by the smoothing capacitor 47, and the DC output voltage Vo is applied to the load 48. Supplied to.

(Operation of supplying power to a load whose voltage fluctuates)

An operation when the DC / DC converter 1 is used as an EV quick charger to rapidly charge a device (for example, a battery) whose voltage varies as the load 48 in FIG. 1 will be described.

FIG. 3 is a diagram showing the output characteristics of the EV quick charger according to the first embodiment of the present invention. Elements common to those shown in FIG. 6 are denoted by common reference numerals.

3, the horizontal axis represents the DC output current Io, and the vertical axis represents the DC output voltage Vo. In FIG. 3, the boundary line BL of the LLC control limit that becomes the reference value RV in FIG. 6 is added, and other portions are the same as those in FIG. In the DC / DC converter 1 according to the first embodiment, the frequency control CF is performed in a region exceeding the boundary line BL that becomes the reference value RV in the output power range Par, and is below the boundary line BL that becomes the reference value RV. In the region, phase shift control CΦ is performed.

FIG. 4 is a flowchart showing the operation of the control device 50 of FIG.

FIG. 5 is a timing chart of the on / off operation in the

FETs

11U, 12U, 13U, 14U, 11V, 12V, 13V, 14V, 11W, 12W, 13W, and 14W in FIG.

In the flowchart of FIG. 4, the battery as the load 48 is rapidly charged by the following steps ST1, ST2, ST3, ST4, ST5, ST6, ST7.

First, when the operation of the control device 50 in the DC / DC converter 1 of FIG. 1 starts, the process proceeds to step ST1. In step ST1, the DC output current Io is measured by a current measuring instrument (not shown), and converted into an output current value IO of a digital signal by the A / D converter 51a in the count value calculator 51. The converted output current value IO is counted by the calculation unit 51b in the count value calculation unit 51, the count value is calculated to obtain the calculation result CV, and the process proceeds to step ST2.

In step ST2, the comparison unit 52 compares the calculation result CV of the count value with the reference value RV that is the boundary line BL in FIG. 3, and when the calculation result CV is larger than the reference value RV (CV ≧ RV). The first comparison result CR1 is output to the frequency control unit 53, and the process proceeds to step ST3. When the calculation result CV is smaller than the reference value RV (CV <RV), the second comparison result CR2 is output to the phase shift control unit 54. To step ST5.

In step ST3, the phase difference setting unit 53a in the frequency control unit 53 sets the phase difference φ of the V phase with respect to the U phase to 120 °, and further the phase difference φ of the W phase with respect to the U phase to 240 °. Each is set, that is, the phase difference φ between the U, V, and W phases is set to 120 °, and the process proceeds to step ST4.

In step ST4, the PFM pulse generation unit 53b in the frequency control unit 53 generates a PFM pulse P1 by the frequency control CF, and outputs this PFM pulse P1 to the pulse drive unit 55. In the frequency control CF, for example, in order to perform constant current output, if the DC output current Io becomes smaller than the target current Ith, feedback control is performed so that the error current ΔI (= Ith−Io) becomes zero. The switching frequency f is increased to increase the DC output current Io. When the DC output current Io becomes larger than the target current Ith, switching is performed by feedback control so that the error current ΔI (= Ith−Io) becomes zero. The PFM pulse P1 is generated by performing frequency modulation such that the frequency f is lowered to reduce the DC output current Io.

The pulse driver 55 drives the PFM pulse P1 to generate the switching drive signals S11U, S12U, S13U, S14U, S11V, S12V, S13V, S14V, S11W, S12W, S13W, S14W, and the U, V, W phase The voltage is applied to each gate of the

FETs

11U, 12U, 13U, 14U, 11V, 12V, 13V, 14V, 11W, 12W, 13W, and 14W in the DC / AC conversion circuits 10U, 10V, and 10W. Then, at the timing shown in FIG. 5, the

U-phase FETs

11U and 14U and the

FETs

12U and 13U are alternately turned on / off with a predetermined dead time. The V-

phase FETs

11V and 14V and the

FETs

12V and 14V are alternately turned on / off with a predetermined dead time delayed by 120 ° from the U-phase. Furthermore, the W-phase FETs 11W and 14W and the

FETs

12W and 13W are alternately turned on / off with a predetermined dead time delayed by 120 ° from the V-phase.

Thereby, the U-phase DC / AC conversion circuit 10U performs a switching operation, and the U-phase DC input voltage Viu is converted into an AC voltage. By the converted AC voltage, the resonance circuit 20U resonates to generate a resonance voltage. The generated resonance voltage is converted into a predetermined voltage by the transformer 30U, rectified and smoothed by the rectifier circuit 40, and a DC output current Io is generated.

Similarly, the V-phase DC / AC conversion circuit 10V performs a switching operation with a 120 ° delay from the U-phase, and the V-phase DC input voltage Viv is converted into an AC voltage. By the converted AC voltage, the resonance circuit 20V resonates to generate a resonance voltage. The generated resonance voltage is converted into a predetermined voltage by the transformer 30V, and rectified and smoothed by the rectifier circuit 40 to generate a DC output current Io. Further, the W-phase DC / AC conversion circuit 10W performs a switching operation with a 120 ° delay from the V-phase, and the W-phase DC input voltage Viw is converted into an AC voltage. Due to the converted AC voltage, the resonant circuit 20W resonates to generate a resonant voltage. The generated resonance voltage is converted into a predetermined voltage by the transformer 30W, rectified and smoothed by the rectifier circuit 40, and a DC output current Io is generated. The battery as the load 48 is rapidly charged by the DC output current Io generated in this way, and the process proceeds to step ST7.

In step ST7, a charging end determination unit (not shown) in the control device 50 determines whether or not there is a request to end battery charging. When there is a request to end battery charging (Yes), the operation ends and the battery charging ends. When there is no termination request (No), the process returns to step ST1 and the above steps ST1 to ST7 are repeated.

In step ST2, when the calculation result CV is smaller than the reference value RV (CV <RV), the second comparison result CR2 is output to the phase shift control unit 54, and the process proceeds to step ST5. In step ST5, the frequency setting unit 54a in the phase shift control unit 54 sets the switching frequency f to the value of the maximum frequency fmax, and proceeds to step ST6.

In step ST6, the phase shift control pulse generator 54b in the phase shift controller 54 changes the phase difference φ between the U, V, and W phases by the phase shift control CΦ as indicated by the arrows in FIG. That is, a phase shift control pulse P 2 that is shifted) is generated, and this phase shift control pulse P 2 is output to the pulse driver 55. In step ST3, the phase difference φ between the U, V, and W phases is set to 120 °. In step ST6, the phase difference φ is changed.

In the phase shift control CΦ, for example, if the DC output current Io becomes smaller than the target current Ith in order to perform a large current output at a low voltage, the error current ΔI (= Ith−Io) becomes zero. By feedback control, the phase difference φ between the U, V, and W phases is made smaller than 120 ° to increase the DC output current Io. If the DC output current Io becomes larger than the target current Ith, the error current ΔI ( = Ith−Io) is phase-shifted by performing phase shift such that the phase difference φ between the U, V, and W phases is increased and the DC output current Io is decreased by feedback control so that it becomes zero. P2 is generated.

The pulse driver 55 drives the phase shift control pulse P2 to generate switching drive signals S11U, S12U, S13U, S14U, S11V, S12V, S13V, S14V, S11W, S12W, S13W, S14W, and U, V, W This is applied to the respective gates of the

FETs

11U, 12U, 13U, 14U, 11V, 12V, 13V, 14V, 11W, 12W, 13W, 14W in the phase DC / AC conversion circuits 10U, 10V, 10W. Then, the

U-phase FETs

11U and 14U and the

FETs

12U and 13U are alternately turned on / off at a timing indicated by an arrow in FIG. 5 with a predetermined dead time. The V-

phase FETs

11V and 14V and the

FETs

12V and 14V are alternately turned on / off with a predetermined dead time after the phase difference φ (<120 °) after the change from the U-phase. Furthermore, the W-phase FETs 11W and 14W and the

FETs

12W and 13W are alternately turned on / off with a predetermined dead time after the phase difference φ (<120 °) after the change from the V-phase.

Thereby, the DC input voltages Viu, Viv, Viw of each phase are converted into AC voltages. The

resonance circuits

20U, 20V, and 20W resonate with the converted AC voltages of the respective phases to generate a resonance voltage. The generated resonance voltage of each phase is converted into a predetermined voltage by the

transformers

30U, 30V, and 30W, and rectified and smoothed by the rectifier circuit 40 to generate the DC output current Io. The battery is rapidly charged by the generated DC output current Io, and the process proceeds to step ST7.

In step ST7, a charging end determination unit (not shown) in the control device 50 determines whether or not there is a request to end battery charging. When there is a request to end battery charging (Yes), the operation ends and the battery charging ends. When there is no request for termination (No), the process returns to step ST1 to repeat the above steps ST1, ST2, ST5, ST6, ST7.

(Effect of Example 1)

According to the control device 50 of the DC / DC converter 1 in the first embodiment, for example, when the battery as the load 48 is rapidly charged, the DC output current Io is supplied to the battery by frequency control and becomes the reference value RV. In the power supply region below the difficult boundary line BL, the phase shift control CΦ is switched to supply the DC output current Io to the battery. Therefore, the low loss DC / DC converter 1 in which the reactive current is suppressed can be realized.

(Modification)

The present invention is not limited to the first embodiment, and various usage forms and modifications are possible. For example, the following forms (a) and (b) are used as the usage form and the modified examples.

(A) The main circuit 2 in the DC / DC converter 1 of FIG. 1 may be changed to another circuit configuration. For example, each

FET

11U, 12U, 13U, 14U, 11V, 12V, 13V, 14V, 11W, 12W, 13W, 14W may be replaced with another switching element such as an insulated gate bipolar transistor (IGBT). The

resonance circuits

20U, 20V, and 20W may be changed to other circuit configurations. For example, instead of the

resonant inductors

21U, 21V, and 21W, the leakage impedance of the

transformers

30U, 30V, and 30W may be used. Further, the plurality of diodes 41 to 46 constituting the rectifier circuit 40 may be replaced with other rectifier elements such as switch elements.

(B) The three-phase DC / AC conversion circuits 10U, 10V, and 10W may be replaced with one full-bridge type DC / AC conversion circuit having six switching elements instead.

DESCRIPTION OF SYMBOLS 1 DC / DC converter 2 Main circuit 10U, 10V, 10W DC /

AC conversion circuit

20U, 20V,

20W Resonance circuit

30U, 30V, 30W Transformer 40 Rectifier circuit 48 Load 50 Control apparatus 51 Count value calculation part 51a A / D conversion Unit 51b Calculation unit 52 Comparison unit 53 Frequency control unit 53a Phase difference setting unit 53b PFM pulse generation unit 54 Phase shift control unit 54a Frequency setting unit 54b Phase shift control pulse generation unit 55 Pulse drive unit

Claims

When a three-phase DC input voltage is supplied, DC / AC conversion is performed by switching the DC input voltage to a three-phase AC voltage by a plurality of switching elements that are turned on / off by a plurality of switching drive signals. Circuit,
A resonant circuit that resonates with the three-phase AC voltage to generate a three-phase resonant voltage;
A three-phase transformer that converts the three-phase resonance voltage into a predetermined voltage and outputs a three-phase conversion voltage;
A three-phase rectifier circuit that rectifies the three-phase conversion voltage and outputs a DC output current to a load;
A controller for a DC / DC converter that supplies the plurality of switching drive signals to a main circuit of the DC / DC converter comprising:
Count the DC output current, calculate the count value to obtain the calculation result,
Comparing the calculation result with a reference value;
When the calculation result is larger than the reference value, the phase difference between the three phases in the three-phase AC voltage is set to an angle 2π / 3, and the desired DC output current is output from the rectifier circuit by frequency control. So as to change the frequency of the plurality of switching drive signals,
When the calculation result is smaller than the reference value, the frequency of the plurality of switching drive signals is set to a maximum value, and the desired DC output current is output from the rectifier circuit by phase shift control. Changing the phase difference between the three phases,
A control device for a DC / DC converter, characterized by being configured.
A count value calculation unit that counts the DC output current, calculates the count value, and obtains the calculation result;
A comparison that compares the calculation result with the reference value, outputs a first comparison result when the calculation result is larger than the reference value, and outputs a second comparison result when the calculation result is smaller than the reference value. And
Based on the first comparison result, the phase difference between the three phases in the three-phase AC voltage is set to the angle 2π / 3, and the desired DC output current is output from the rectifier circuit by the frequency control. As described above, a frequency controller that changes the frequency of the plurality of switching drive signals;
Based on the second comparison result, the frequency of the plurality of switching drive signals is set to the maximum value, and the desired DC output current is output from the rectifier circuit by the phase shift control. A phase shift controller that changes the phase difference between the phases;
The control apparatus for a DC / DC converter according to claim 1, comprising:
The count value calculator is
An analog / digital converter that converts the measured DC output current into an output current value of a digital signal;
A calculation unit for calculating an output current value of the digital signal to obtain the calculation result;
The control device for a DC / DC converter according to claim 2, wherein:
The DC / DC converter control device according to claim 3 is:
A pulse driver that drives a frequency modulation pulse and / or a phase shift control pulse to generate the plurality of switching drive signals;
The frequency control unit
A phase difference setting unit for setting the phase difference between the three phases to the angle 2π / 3;
A frequency modulation pulse generator that modulates the frequency by the frequency control and generates the frequency modulation pulse to be given to the pulse driver; and
The control apparatus of the DC / DC converter characterized by having.
The phase shift controller is
A frequency setting unit for setting the frequency to the maximum value;
A phase shift control pulse generating unit that changes the phase difference between the three phases by the phase shift control and generates the phase shift control pulse to be given to the pulse driving unit;
5. The control device for a DC / DC converter according to claim 4, further comprising:
The DC / AC conversion circuit is constituted by a bridge circuit of the plurality of switching elements,
The resonant circuit is constituted by a current resonant circuit having a resonant inductor, a resonant capacitor, and an exciting inductor,
The rectifier circuit includes a rectifier unit in which a plurality of rectifier elements are bridge-connected, and a smoother unit that smoothes the output voltage of the rectifier unit.
The control device for a DC / DC converter according to claim 1.
2. The DC / DC converter control device according to claim 1, wherein the load is a device whose voltage fluctuates.
8. The DC / DC converter control device according to claim 7, wherein the device is a battery.