JPWO2019171414A1 - DC / DC converter controller - Google Patents

Abstract

The control device 50 of the DC / DC converter 1 capable of covering a wide range of outputable power with low loss is realized. 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. For example, when the battery is quickly charged, the DC output current Io is supplied to the battery by the frequency control of the frequency control unit 53. When the power supply region falls below the boundary line of the current resonance control limit, which is a reference value and difficult to control, the phase shift control is switched to the phase shift control of the phase shift control unit 54, and the DC output current Io is supplied to the battery.

Description

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

Conventionally, for example, as a DC / DC converter for charging a battery, a current resonance type circuit such as a high-efficiency LLC circuit having a small switching loss or the like is described in Patent Documents 1 and 2.

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

Japanese Unexamined Patent Publication No. 2012-249375 Japanese Unexamined Patent Publication No. 2013-243114

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

In FIG. 6, the horizontal axis represents the DC output current Io and the vertical axis represents the DC output voltage Vo. The shaded area surrounded by points A, B, C, D, E, and F is the output power range Par of the EV quick charger. EV quick chargers require a wide range of output characteristics due to differences in battery voltage depending on the vehicle model.

For example, point A in FIG. 6 has an output current Io of 30 A and an output voltage Vo of 500 V, point B has an output current Io of 33.3 A and an output voltage Vo of 450 V, and point C has an output current Io of 38 A and an output. It 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 shaded area surrounded by these points A, B, C, D, E, and F is the output power range Par of the EV quick charger, and a current control CC is required.

In a current resonance type circuit such as an LLC circuit, the output voltage Vo is lowered by raising the switching frequency f of the switching element and the output voltage Vo is raised by lowering the switching frequency f by frequency control. Therefore, when a conventional current resonance type circuit is applied to an EV quick charger that requires a wide range of output characteristics, when trying to charge the battery at a low voltage with an output voltage Vo of around 200V to 150V, the switching frequency f However, it exceeds the maximum allowable frequency, which makes it difficult to charge the battery. Further, in order to realize a wide range of output characteristics, it is necessary to set a parameter so that a reactive current that does not contribute to the output power always flows through the exciting inductance. However, the ineffective current causes conduction loss in the flowing route (for example, resonance capacitor-> switching element-> transformer primary winding-> resonance inductor-> resonance capacitor current path), so that the loss cannot be reduced.

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

According to the present invention, when a three-phase DC input voltage is supplied, a plurality of switching elements that operate on / off by a plurality of switching drive signals switch the DC input voltage to obtain a three-phase AC (alternating current) voltage. A DC / AC conversion circuit that converts to the three-phase AC voltage, a resonance circuit that resonates with the three-phase AC voltage to generate a three-phase resonance voltage, and a three-phase conversion that converts the three-phase resonance voltage into a predetermined voltage. For the main circuit of a DC / DC converter including 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. It is a control device of a DC / DC converter that supplies a plurality of switching drive signals.

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

The control device, for example, compares the calculation result with the reference value with a count value calculation unit that counts the DC output current, calculates the count value to obtain the calculation result, and obtains the calculation result. A comparison unit that outputs the first comparison result when it is larger than the reference value and outputs the second comparison result when the calculation result is smaller than the reference value, and the AC voltage of the three phases 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 so that the desired DC output current is output from the rectifier circuit by the frequency control. Based on the frequency control unit to be operated and 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. As described above, it has a phase shift control unit that changes the phase difference between the three phases.

According to the control device of the DC / DC converter of the present invention, the DC output current is supplied to the load by frequency control, and when the power supply region becomes smaller than the reference value which is difficult to control, the DC output current is switched to the phase shift control. Is configured to supply 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 entire DC / DC converter according to the first embodiment of the present invention. FIG. 2 is a configuration diagram showing a control device in the DC / DC converter of FIG. FIG. 3 is a diagram showing the output characteristics of the EV quick charger according to 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 on / off operation of the switching element in FIG. 1 (for example, a field effect transistor, hereinafter referred to as “FET”). FIG. 6 is a diagram showing the output characteristics of a conventional EV quick charger.

The embodiments for carrying out the present invention will become clear when the following description of preferred embodiments is read in light of the accompanying drawings. However, the drawings are for illustration purposes only and do not limit the scope of the present invention.

(Structure of Example 1)

FIG. 1 is a schematic circuit diagram showing the entire DC / DC converter according to the first embodiment of the present invention.

The DC / DC converter 1 switches the three-phase (for example, U-phase, V-phase, and W-phase) DC input voltages Viu, Viv, and Viw to convert them into a predetermined DC output voltage Vo and DC output current Io. The main circuit 2 is composed of a control device 50 that controls 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 to convert them into three-phase AC voltage, and each phase is the same circuit. It is configured.

The U-phase DC / AC conversion circuit 10U has a plurality of switching elements (for example, FETs) 11U, 12U, 13U, 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, which 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 connects a plurality of switching elements (for example, FETs) 11V, 12V, 13V, 14V that are turned on / off by a plurality of switching drive signals S11V, S12V, S13V, and S14V, respectively. These FETs 11V, 12V, 13V, 14V are bridge-connected. Parasitic diodes 15 are connected in antiparallel between the source and drain of each FET 11V, 12V, 13V, and 14V.

Further, the W-phase DC / AC conversion circuit 10W has a plurality of switching elements (for example, FETs) 11W, 12W, 13W, 14W that are turned on / off by a plurality of switching drive signals S11W, S12W, S13W, and S14W, respectively. However, these FETs 11W, 12W, 13W, and 14W are bridge-connected. Parasitic diodes 15 are connected in antiparallel between the source and drain of each of the FETs 11W, 12W, 13W, and 14W.

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

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

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

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

A three-phase transformer 30U, 30V, 30W is connected to the output side of the three-phase resonance circuit 20U, 20V, 20W. The three-phase transformers 30U, 30V, 30W convert the three-phase resonance voltage output from the three-phase resonance circuits 20U, 20V, 20W into a predetermined voltage and output the 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 of the primary winding 31U (black circle point in FIG. 1) is connected to the resonance 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, the winding start side of the primary winding 31V is connected to the resonant inductor 20V, and the primary winding 31V thereof. The winding end side of the 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 thereof. The winding end side is connected to the connection point between the FETs 13W and 14W.

A three-phase rectifier circuit 40 is connected to the three-phase secondary windings 32U, 32V, 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, 46) are bridge-connected, an output voltage of the rectifier unit, and the output voltage of the rectifier unit. It is composed of a smoothing portion (for example, a smoothing capacitor 47) that smoothes the output current.

The control device 50 controls a plurality of (for example, 12) switching drive signals S11U, S12U, S13U, S14U, S11V, S12V, S13V, S14V, S11W, S12W, S13W, in order to control the switching operation of the main circuit 2. This is a device that 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 configuration diagram showing a 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 composed of a processor having a central processing unit (CPU) capable of program control, or an individual circuit. The pulse drive unit 55 is composed of individual circuits.

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 the calculation result CV. The count value calculation unit 51 is 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. A calculation unit 51b for calculating the calculation result CV, and a comparison unit 52 are 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 when the calculation result CV is larger than the reference value RV (CV ≧ RV), outputs the first comparison result CR1 to the frequency control unit 53 for calculation. 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.

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

The phase shift control unit 54 sets 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 based on the second comparison result CR2. The phase difference φ between the U, V, and W phases is set so that the desired DC output current Io is output from the rectifier circuit 40 by the phase shift control while fixing (that is, setting) the maximum switching frequency fmax of the maximum value. 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, S14W to the maximum frequency fmax. It has a phase shift control pulse generation unit 54b connected to the output side. The phase shift control pulse generation unit 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, and the pulse drive unit 55 is on the output side. It is connected.

The pulse drive unit 55 drives the PFM pulse P1 or the phase shift control pulse P2 to generate switching drive signals S11U, S12U, S13U, S14U, S11V, S12V, S13V, S14V, S11W, S12W, S13W, S14W. Yes, it is composed of individual circuits such as transistors.

(Operation of power supply 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 fluctuate is used as the load 48 will be described.

For example, when a constant voltage DC output voltage Vo is supplied 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 controls the frequency. A PFM pulse P1 is generated, and this PFM pulse P1 is output to the pulse drive 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 error voltage ΔV (= Vth-Vo) becomes zero, and the switching frequency f is controlled by feedback control. When the DC output voltage Vo is raised and the DC output voltage Vo becomes higher than the target voltage Vth, the switching frequency f is set by feedback control so that the error voltage ΔV (= Vth-Vo) becomes zero. The PFM pulse P1 is generated by performing frequency modulation such that the DC output voltage Vo is raised to lower it. The pulse drive unit 55 drives the PFM pulse P1 to generate switching drive signals S11U, S12U, S13U, S14U, S11V, S12V, S13V, S14V, S11W, S12W, S13W, S14W, and U, V, W phases. It is given to each gate of FET 11U, 12U, 13U, 14U, 11V, 12V, 13V, 14V, 11W, 12W, 13W, 14W in the DC / AC conversion circuit 10U, 10V, 10W.

In the U-phase DC / AC conversion circuit 10U, the FETs 11U, 14U and the FETs 12U, 13U are alternately turned on / off by the switching drive signals S11U, S12U, S13U, and S14U with a predetermined dead time. In the V-phase DC / AC conversion circuit 10V, the switching drive signals S11V, S12V, S13V, S14V cause FET11V, 14V and FET12V, 14V to alternate 120 ° behind the U phase with a predetermined dead time. Works on / off. Further, in the W-phase DC / AC conversion circuit 10W, the FETs 11W, 14W and the FETs 12W, 13W are delayed by 120 ° from the V phase due to the switching drive signals S11W, S12W, S13W, S14W, and a predetermined dead time is set. It operates on / off alternately.

In the U-phase DC / AC conversion circuit 10U, when the FETs 11U and 14U are on and the FETs 12U and 13U are off, the U-phase DC input voltage Viu causes the FET 11U → resonance capacitor 21U → resonance inductor 22U → excitation inductor 23U and The power supply current flows in the path of the primary winding 31U of the transformer 30U → the FET 14U → the DC input voltage Viu. When the FETs 12U and 13U are turned on and the FETs 11U and 14U are turned off after a predetermined dead time, the DC input voltage Viu causes the FET 13U → the exciting inductor 23U and the transformer 30U to be the primary winding 31U → the resonance inductor 22U → resonance. The power supply current flows in the path of the capacitor 21U → FET 12U → DC input voltage Viu. As a result, the DC input voltage Viu is converted into an AC voltage by the switching operation of the DC / AC conversion circuit 10U.

The converted AC voltage causes the resonance circuit 20U to resonate to generate a resonance 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, then 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 delay of 120 ° from the U-phase, and the V-phase DC input voltage Viv is converted into an AC voltage. The converted AC voltage causes the resonance circuit 20V to resonate to generate a resonance voltage. The generated resonance voltage is converted into a predetermined voltage by the transformer 30V, rectified by a 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 loaded 48. Is supplied to.

Further, the W-phase DC / AC conversion circuit 10W performs a switching operation with a delay of 120 ° from the V-phase, and the W-phase DC input voltage Viw is converted into an AC voltage. The converted AC voltage causes the resonance circuit 20W to resonate to generate a resonance voltage. The generated resonance voltage is converted into a predetermined voltage by the transformer 30W, rectified by a 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 loaded 48. Is supplied to.

(Operation of power supply to loads with fluctuating voltage)

As the load 48 of FIG. 1, the operation when the DC / DC converter 1 is used as an EV quick charger in order to quickly charge a device (for example, a battery) whose voltage fluctuates 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, and common reference numerals are given to the elements common to the elements in the conventional FIG.

In FIG. 3, the horizontal axis represents the DC output current Io and the vertical axis represents the DC output voltage Vo. In FIG. 3, in FIG. 6, the boundary line BL of the LLC control limit, which is the reference value RV, is added, and other parts are the same as those in FIG. In the DC / DC converter 1 of the first embodiment, in the output available power range Par, frequency control CF is performed in a region exceeding the boundary line BL which is the reference value RV, and is below the boundary line BL which is 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 on / off operation for FETs 11U, 12U, 13U, 14U, 11V, 12V, 13V, 14V, 11W, 12W, 13W, 14W in FIG.

In the flowchart of FIG. 4, the battery having a load of 48 is rapidly charged by the following steps ST1, ST2, ST3, ST4, ST5, ST6, and 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 is converted into the output current value IO of the digital signal by the A / D conversion unit 51a in the count value calculation unit 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, the calculation result CV is obtained, 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 which 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, the process proceeds to step ST3, and 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. Output to and proceed 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 to 120 ° with respect to the U phase, and further sets the phase difference φ of the W phase to 240 ° with respect to the U phase. 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 the PFM pulse P1 by the frequency control CF, and outputs the 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 Is, the error current ΔI (= Is-Io) becomes zero by feedback control. Switching is performed by feedback control so that the switching frequency f is increased to increase the DC output current Io, and when the DC output current Io becomes larger than the target current Is, the error current ΔI (= Is-Io) becomes zero. The PFM pulse P1 is generated by performing frequency modulation such as lowering the frequency f to reduce the DC output current Io.

The pulse drive unit 55 drives the PFM pulse P1 to generate switching drive signals S11U, S12U, S13U, S14U, S11V, S12V, S13V, S14V, S11W, S12W, S13W, S14W, and U, V, W phases. It is given to each gate of FET 11U, 12U, 13U, 14U, 11V, 12V, 13V, 14V, 11W, 12W, 13W, 14W in the DC / AC conversion circuit 10U, 10V, 10W. Then, at the timing shown in FIG. 5, the U-phase FETs 11U and 14U and the FETs 12U and 13U alternately turn on / off with a predetermined dead time. The V-phase FETs 11V, 14V and FETs 12V, 14V operate alternately on / off with a predetermined dead time, delayed by 120 ° from the U phase. Further, the W-phase FETs 11W and 14W and the FETs 12W and 13W alternately turn on / off with a predetermined dead time with a delay of 120 ° from the V-phase.

As a result, 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. The converted AC voltage causes the resonance circuit 20U to resonate 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 the DC output current Io is generated.

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

In step ST7, the charge end determination unit (not shown) in the control device 50 determines whether or not there is a request to end battery charging, and when there is a request to end battery charging (Yes), ends the operation and charges the battery. When there is no request for termination (No), the process returns to step ST1 and the above steps ST1-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 generation unit 54b in the phase shift control unit 54 changes the phase difference φ between the U, V, and W phases by the phase shift control CΦ, as shown by the arrows in FIG. That is, a phase shift control pulse P2 that causes shift) is generated, and the phase shift control pulse P2 is output to the pulse drive unit 55. In step ST3, the phase difference φ between the U, V, and W phases is set to 120 °, but in step ST6, the phase difference φ is changed.

In the phase shift control CΦ, for example, in order to output a large current with a low voltage, if the DC output current Io becomes smaller than the target current Is, the error current ΔI (= Is-Io) becomes zero. By feedback control, the phase difference φ between each U, V, W phase is made smaller than 120 ° to increase the DC output current Io, and if the DC output current Io becomes larger than the target current Is, the error current ΔI ( The phase shift control pulse is performed by performing a 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 (= Is-Io) becomes zero. Generate P2.

The pulse drive unit 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. It is applied to each gate of FET 11U, 12U, 13U, 14U, 11V, 12V, 13V, 14V, 11W, 12W, 13W, 14W in the phase DC / AC conversion circuit 10U, 10V, 10W. Then, at the timing indicated by the arrow in FIG. 5, the U-phase FETs 11U and 14U and the FETs 12U and 13U alternately turn on and off with a predetermined dead time. The V-phase FETs 11V and 14V and the FETs 12V and 14V operate alternately on / off with a predetermined dead time after a phase difference φ (<120 °) after the change from the U phase. Further, the W-phase FETs 11W and 14W and the FETs 12W and 13W are alternately on / off with a predetermined dead time after a phase difference φ (<120 °) after the change from the V phase.

As a result, the DC input voltages Viu, Viv, and Viw of each phase are converted into AC voltages. Resonant circuits 20U, 20V, and 20W resonate with the converted AC voltage of each phase 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 is rectified and smoothed by the rectifier circuit 40 to generate a 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, the charge end determination unit (not shown) in the control device 50 determines whether or not there is a request to end battery charging, and when there is a request to end battery charging (Yes), ends the operation and charges the battery. When there is no request for termination (No), the process returns to step ST1 and the above steps ST1, ST2, ST5, ST6, and ST7 are repeated.

(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 having a load of 48 is rapidly charged, the DC output current Io is supplied to the battery by frequency control to obtain the reference value RV. When the power supply region falls below the difficult boundary line BL, the phase shift control CΦ is switched to supply the DC output current Io to the battery. Therefore, a low-loss DC / DC converter 1 in which reactive current is suppressed can be realized.

(Modification example)

The present invention is not limited to the above-mentioned Example 1, and various usage forms and modifications are possible. Examples of this usage pattern and modification include the following (a) and (b).

(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, the leakage impedance of the transformers 30U, 30V, 30W may be used instead of the resonant inductors 21U, 21V, 21W. Further, the plurality of diodes 41-46 constituting the rectifier circuit 40 may be replaced with other rectifier elements such as a switch element.

(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.

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 Controller 51 Count value calculation unit 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 (8)

When a three-phase DC input voltage is supplied, a plurality of switching elements that operate on / off by a plurality of switching drive signals switch the DC input voltage and convert it into a three-phase AC voltage. Circuit and
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 the three-phase conversion voltage.
A three-phase rectifier circuit that rectifies the three-phase conversion voltage and outputs a DC output current to the load.
A DC / DC converter control device that supplies the plurality of switching drive signals to the main circuit of the DC / DC converter.
The DC output current is counted, and this count value is calculated to obtain the calculation result.
Compare the calculation result with the 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 three phases is set to an angle of 2π / 3, and the desired DC output current is output from the rectifier circuit by frequency control. By changing the frequencies of the plurality of switching drive signals so as to
When the calculation result is smaller than the reference value, the frequencies of the plurality of switching drive signals are set to the maximum values, and the phase shift control is used so that the desired DC output current is output from the rectifier circuit. Change the phase difference between the three phases,
A control device for a DC / DC converter characterized by having a configuration. A count value calculation unit that counts the DC output current, calculates the count value, and obtains the calculation result.
Comparison between the calculation result and the reference value, and when the calculation result is larger than the reference value, the first comparison result is output, and when the calculation result is smaller than the reference value, the second comparison result is output. Department and
Based on the first comparison result, the phase difference between the three phases in the AC voltage of the three phases 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, the frequency control unit 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 control unit that changes the phase difference between the phases,
The control device for a DC / DC converter according to claim 1. The count value calculation unit
An analog / digital converter that converts the measured DC output current into a digital signal output current value,
An arithmetic unit that calculates the output current value of the digital signal and obtains the calculation result,
2. The control device for a DC / DC converter according to claim 2. The DC / DC converter control device according to claim 3 is
It has a pulse drive unit 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 that sets the phase difference between the three phases to the angle 2π / 3 and
A frequency modulation pulse generation unit that modulates the frequency by the frequency control and generates the frequency modulation pulse to be given to the pulse drive unit.
A control device for a DC / DC converter, which comprises. The phase shift control unit
A frequency setting unit that sets the frequency to the maximum value,
A phase shift control pulse generation 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 drive unit.
The DC / DC converter control device according to claim 4, wherein the DC / DC converter has. The DC / AC conversion circuit is composed of a bridge circuit of the plurality of switching elements.
The resonance circuit is composed of a current resonance type circuit having a resonance inductor, a resonance capacitor and an excitation inductor.
The rectifier circuit is composed of a rectifier unit in which a plurality of rectifier elements are bridge-connected and a smoothing unit that smoothes the output voltage of the rectifier unit.
The control device for a DC / DC converter according to claim 1. The control device for a DC / DC converter according to claim 1, wherein the load is a device whose voltage fluctuates. The control device for a DC / DC converter according to claim 7, wherein the device is a battery.

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