JP2021002902A - Charger - Google Patents

Abstract

To provide a charger which charges a load capacitor while preventing dielectric breakdown.SOLUTION: A constant current DC/DC converter CC is capable of varying an output voltage between a ground voltage and a predetermined voltage and outputs a constant current. Constant voltage DC/DC converters CV1-CVN output a predetermined voltage. A capacitor C is charged with a voltage obtained by cascade-connection of the constant current DC/DC converter CC with the constant voltage DC/DC converters CV1-CVN. The constant current DC/DC converter CC and the constant voltage DC/DC converters CV1-CVN output a voltage stepped up by a step-up transformer in which a primary inductor and a secondary inductor are provided in a physically separated state.SELECTED DRAWING: Figure 1

Description

The present invention relates to a charging device.

It is known that a capacitor is used as a high-voltage power storage as a power source for a device operating at a high voltage. A method of charging such a power supply capacitor has been proposed.

As a method of charging a capacitor, a method of charging a capacitor while controlling a current is known. For example, a charging device (Reference 1) has been proposed in which the charging voltage of a capacitor is controlled with high accuracy by charging the capacitor while limiting the output DC current. In addition, a method of charging a capacitor with a constant voltage (constant voltage charging), a method of charging a capacitor with a constant current (constant current charging), and a method of combining constant voltage charging and constant current charging, etc. Various charging methods are known.

A method has also been proposed in which an AC voltage output from a DC-DC converter composed of a switching regulator or the like is boosted by a step-up transformer, and a capacitor is charged by a DC voltage rectified by a rectifier (Patent Document 2). A configuration using such a transformer is known as an isolated DC / DC converter. In this method, two inverter circuits are provided, and the first initial charging inverter charges to an initial charging voltage slightly lower than the target voltage of the load capacitor. After that, the initial charging inverter is stopped, the fine adjustment inverter is operated, and the voltage of the load capacitor 10 is charged more slowly from the initial charging voltage to the target voltage than at the time of initial charging.

Further, there is known a method in which a chopper circuit is provided in front of an isolated DC / DC converter and a voltage transformed by the chopper circuit is input to an inverter circuit (Patent Document 3). In this configuration, the boost chopper circuit boosts the voltage of the main storage battery to charge the intermittent discharge storage battery. The inverter circuit converts it into DC AC of the storage battery for intermittent discharge and outputs it to a step-up transformer consisting of a transformer. The step-up transformer boosts the alternating current from the inverter circuit to a high-voltage alternating current and outputs it to the high-voltage rectifying circuit. The high-voltage rectifier circuit converts high-voltage alternating current into direct current and outputs a direct current voltage. Therefore, by charging the storage battery for intermittent discharge with the voltage boosted by the chopper circuit, it is possible to suppress a voltage drop during intermittent discharge and an increase in size of the power supply device.

In addition, various high-voltage power supplies or capacitor charging devices have been proposed (Patent Documents 4 to 6 and Non-Patent Document 1).

Jitsukaisho 60-11344 Japanese Unexamined Patent Publication No. 10-52030 JP-A-63-92263 Japanese Unexamined Patent Publication No. 10-117478 Japanese Unexamined Patent Publication No. 2010-218856 Japanese Unexamined Patent Publication No. 2011-36063

Kazuhiro Kawamura and 2 others, "Circuit Technology for LLC Current Resonant Power Supply", Fuji Electric Technical Report Vol. 87, No. 4, published on December 30, 2014, Fuji Electric Co., Ltd.

As described above, when power is supplied to a device used at a high voltage, a configuration having an isolated DC / DC converter that transforms with a transformer is used in order to secure insulation between the main power supply and the device side. .. In order to perform transformation with high efficiency by a transformer, in order to reduce the leakage of magnetic flux and transmit power from the primary side to the secondary side, the primary side winding and the secondary side winding are wound in layers. The wire will be wound as closely as possible.

However, for example, when charging a capacitor at a high pressure of 10 kV or more, if the primary winding and the secondary winding are tightly wound, there arises a problem that insulation between the two becomes difficult. In addition, if the number of secondary windings is increased in high-voltage and high-frequency transformers, the voltage between the wires increases, the leakage current flowing through the capacitance between the wires increases, and problems such as heating of each wire occur. ..

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a charging device for charging a load capacitor while preventing dielectric breakdown.

The charging device according to the first aspect of the present invention includes a constant current DC / DC converter whose output voltage is variable between a ground voltage and a predetermined voltage and which outputs a constant current, and the predetermined voltage. The capacitor is charged by a voltage obtained by cascading the constant current DC / DC converter and the plurality of constant voltage DC / DC converters, and having a plurality of constant voltage DC / DC converters to output the above. The constant current DC / DC converter and the plurality of constant voltage DC / DC converters output a voltage boosted by a step-up transformer in which the primary side inductor and the secondary side inductor are physically separated from each other. As a result, when charging the capacitor, insulation breakage in the constant current DC / DC converter and constant voltage DC / DC converter is prevented, and leakage current of the secondary winding is prevented to provide a highly efficient converter. Can be configured.

The charging device according to the second aspect of the present invention is the charging device described above, wherein the constant current DC / DC converter and the constant voltage DC / DC converter include a switching circuit, a resonance capacitor, and the primary side inductor. Is connected to the switching circuit via the resonance capacitor, a rectifier that outputs a rectified voltage obtained by rectifying the voltage induced in the secondary inductor of the transformer, and a control circuit that controls switching of the switching circuit. And, it is desirable to have. Thereby, a constant current DC / DC converter and a constant voltage DC / DC converter that can prevent dielectric breakdown can be configured.

The charging device according to the third aspect of the present invention is the above-mentioned charging device, in which the rectifier of the constant voltage DC / DC converter outputs the predetermined voltage, and the constant current DC / DC converter is: The constant current DC / DC converter further has a chopper circuit capable of adjusting the voltage input to the switching circuit, and by controlling the switching between the chopper circuit and the switching circuit, the current output from the rectifier can be generated. It is desirable to control the voltage output by the rectifier so that the current becomes constant. Thereby, the operation of the constant current DC / DC converter and the constant voltage DC / DC converter can be realized.

The charging device according to the fourth aspect of the present invention is the above-mentioned charging device, and in the control circuit, the switching frequency of the switching circuit is the leakage inductance generated by the leakage flux of the transformer and the resonance capacitor. It is desirable to control the switching of the switching circuit so as to substantially match the resonance frequency of. Thereby, the influence of the leakage inductance can be offset.

The charging device according to the fifth aspect of the present invention is the above-mentioned charging device, and the control circuit is the switching circuit at a timing when the current flowing due to the resonance between the leakage inductance and the resonance capacitor is near zero. It is desirable to perform switching. This makes it possible to prevent loss due to switching.

The charging device according to the sixth aspect of the present invention is the above-mentioned charging device, in which the capacitor is constantly charged by the constant current DC / DC converter, and the output voltage of the constant current DC / DC converter is the predetermined voltage. When the voltage reaches the above voltage, the step of stopping the constant current charging and one of the plurality of constant voltage DC / DC converters are operated to obtain the predetermined voltage from the one constant voltage DC / DC converter. It is desirable to charge the capacitor by the step of outputting. As a result, the charging voltage of the capacitor can be improved.

The charging device according to the seventh aspect of the present invention is the above-mentioned charging device, and it is desirable to charge the capacitor by repeating the two steps. As a result, the charging voltage of the capacitor can be improved.

According to the present invention, it is possible to provide a charging device that charges a load capacitor while preventing dielectric breakdown.

It is a figure which shows typically the circuit structure of the charging device 100 which concerns on Embodiment 1. FIG. It is a figure which shows typically the structure of the constant current DC / DC converter CC. It is a figure which shows typically the structure of the constant voltage DC / DC converter CV. It is a flowchart which shows the charging operation of the charging device 100 which concerns on Embodiment 1. FIG. It is a figure which shows the charging voltage of a capacitor.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In each drawing, the same elements are designated by the same reference numerals, and duplicate explanations are omitted as necessary.

Embodiment 1
The charging device according to the first embodiment will be described. FIG. 1 schematically shows a circuit configuration of the charging device 100 according to the first embodiment. The charging device 100 is configured to receive a power supply from the DC power source 20 and quickly charge a capacitor C, which is a high-voltage large-capacity capacitor provided as a high-voltage power storage device. The charged capacitor C is connected to an external device to provide a high voltage power supply.

The charging device 100 includes one constant current DC / DC converter CC, a plurality of constant voltage DC / DC converters CV1 to CVN, and a voltage measuring circuit 30. The constant current DC / DC converter CC and the constant voltage DC / DC converters CV1 to CVN are cascade-connected to the common line CL. However, N is an integer of 2 or more. The power supply terminal ST of the charging device 100 is connected to the positive electrode PE of the DC power supply 20, and the ground terminal GT of the charging device 100 is connected to the negative electrode NE of the DC power supply 20, that is, ground. The voltage measuring circuit 30 is configured to be able to measure the voltage (that is, charging voltage) output to the capacitor C, and outputs the measurement result DET to the constant current DC / DC converter CC.

The configuration of the constant current DC / DC converter CC will be described. FIG. 2 schematically shows the configuration of the constant current DC / DC converter CC. The constant current DC / DC converter CC includes a current resonance type DC / DC converter 1, a control circuit 2, a step-down chopper circuit 3, and current sensors S1 and S2.

The step-down chopper circuit 3 has transistors T31 and T32, a smoothing capacitor C1 and an inductor L. Here, the transistors T31 and T32 will be described as being an insulated gate bipolar transistor (IGBT). The transistors T31 and T32 are not limited to IGBTs, and other transistors such as MOSFETs (Metal-Oxide-Semiconductor Field-Effect Transistors) may be used.

The transistors T31 and T32 have the same polarity so that a current flows from the high voltage side to the low voltage side, and are vertically connected between the power supply terminal ST and the ground terminal GT. Specifically, the collector of the transistor T31 is connected to the power supply terminal ST, and the emitter is connected to the collector of the transistor T32. The emitter of the transistor T32 is connected to the ground terminal GT. Further, the emitter of the transistor T31 and the collector of the transistor T32 are connected to one end LT1 of the inductor L. Further, a smoothing capacitor C1 is connected between the collector of the transistor T31 and the emitter of the transistor T32.

The gates of the transistors T31 and T32 are connected to the control circuit 2. As a result, the on / off (switching) of the transistors T31 and T32 is controlled by the control circuit 2.

In the following, it is assumed that a freewheeling diode (freewheeling diode) is connected to the transistor in antiparallel. That is, the anode of the freewheeling diode is connected to the emitter of the transistor and the cathode is connected to the collector of the transistor. As a result, the backflow current generated when the transistor is turned off can be passed through the freewheeling diode, so that the transistor can be avoided from failure due to the backflow current.

Next, the current resonance type DC / DC converter 1 includes a high frequency inverter circuit 11, a high frequency transformer 12, a resonance capacitor Cr, a smoothing capacitor C2, and rectifiers R1 and R2.

The high-frequency inverter circuit 11 (also referred to as a switching circuit) is configured as a full-bridge type inverter having transistors T1 to T4. The high frequency transformer 12 is configured as a step-up transformer provided with the primary side inductor L1 and the secondary side inductors L2 and L3. Here, it is assumed that the transistors T1 to T4 are IGBTs. The transistors T1 to T4 are not limited to IGBTs, and other transistors such as MOSFETs may be used.

The transistors T1 and T2 are aligned in polarity so that a current flows from the high voltage side to the low voltage side, and are longitudinally connected between the end portion LT2 of the inductor L of the step-down chopper circuit 3 and the ground terminal GT. Specifically, the collector of the transistor T1 is connected to the end portion LT2 of the inductor L, and the emitter is connected to the collector of the transistor T4. The emitter of the transistor T4 is connected to the ground terminal GT.

The transistors T3 and T4 are aligned in polarity so as to allow current to flow from the high voltage side to the low voltage side, and are longitudinally connected between the end portion LT2 of the inductor L of the step-down chopper circuit 3 and the ground terminal GT. Specifically, the collector of the transistor T3 is connected to the end portion LT2 of the inductor L, and the emitter is connected to the collector of the transistor T4. The emitter of the transistor T4 is connected to the ground terminal GT.

The gates of the transistors T1 to T4 are connected to the control circuit 2. As a result, the on / off (switching) of the transistors T1 to T4 is controlled by the control circuit 2.

In order to smooth the bank voltage input from the step-down chopper circuit 3 to the high-frequency inverter circuit 11, a smoothing capacitor C2 is connected between the collectors of the transistors T1 and T3 and the emitters of the transistors T2 and T4.

The emitter of the transistor T1 and the collector of the transistor T2 are connected to one end of the resonant capacitor Cr. The other end of the resonance capacitor Cr is connected to one end of the primary inductor L1 of the high frequency transformer 12. The other end of the primary inductor L1 of the high frequency transformer 12 is connected to the emitter of the transistor T3 and the collector of the transistor T4.

In the present embodiment, the primary side inductor L1 and the secondary side inductors L2 and L3 are arranged apart from each other, and leakage flux is generated. Leakage inductance Lr is generated by this leakage flux. In FIG. 2, the leakage inductance Lr is displayed between the resonance capacitor Cr and the primary inductor L1.

A rectifier R1 is connected to the secondary inductor L2, and a DC voltage obtained by rectifying the AC voltage generated by induction on the secondary inductor L2 is output to the common line CL. A rectifier R2 is connected to the secondary inductor L3, and a DC voltage obtained by rectifying the AC voltage generated by induction on the secondary inductor L3 is output to the common line CL.

A smoothing capacitor C3 is connected between the output of the rectifier R1 and the output of the rectifier R2 in order to smooth the voltage output to the common line CL.

Next, the control circuit 2 will be described. The control circuit 2 is connected to the end LT2 of the step-down chopper circuit 3. As a result, the bank voltage input to the high-frequency inverter circuit 11 can be monitored. Further, a current sensor S1 is provided between the end LT2 of the step-down chopper circuit 3 and the high-frequency inverter circuit 11, measures the current supplied to the high-frequency inverter circuit 11, and outputs the measurement result to the control circuit 2. .. Further, a current sensor S2 is provided to measure the current flowing through the primary inductor L1 of the high frequency transformer 12, and the measurement result is output to the control circuit 2.

As will be described later, in order to control the operation of the constant voltage DC / DC converters CV1 to CVN, the control circuit 2 is configured to be able to output a control signal CON to the control circuit of the constant voltage DC / DC converters CV1 to CVN. To.

Next, the configurations of the constant voltage DC / DC converters CV1 to CVN will be described. The constant voltage DC / DC converters CV1 to CVN are configured as constant voltage DC / DC converters CV having the same circuit configuration. FIG. 3 schematically shows the configuration of the constant voltage DC / DC converter CV.

The constant voltage DC / DC converter CV has a configuration in which the step-down chopper circuit 3 and the current sensor S1 are removed from the constant current DC / DC converter 1, and the control circuit 2 is replaced with the control circuit 4. The collectors of the transistors T1 and T3 of the high-frequency inverter circuit 11 are connected to the power supply terminal ST. As a result, the power supply voltage output from the DC power supply 20 becomes the bank voltage input to the high-frequency inverter circuit 11.

The control circuit 4 is connected to the gate of the transistors T1 to T4 of the high-frequency inverter circuit 11 and controls the on / off (switching) of the transistors T1 to T4. Further, the current sensor S2 measures the current flowing through the primary side inductor L1 of the high frequency transformer 12, and outputs the measurement result to the control circuit 4. The control circuit 4 controls the switching of the high frequency inverter circuit 11 so that a constant voltage V1 is output to the common line CL.

The control circuit 4 receives a control signal CON from the control circuit 2 of the constant current DC / DC converter CC. Thereby, the control circuit 2 of the constant current DC / DC converter CC can control the stop and start of the respective operations of the constant voltage DC / DC converters CV1 to CVN.

Here, switching of the high frequency inverter circuit 11 in the constant current DC / DC converter CC and the constant voltage DC / DC converters CV1 to CVN will be described. As described above, in this configuration, since the primary side inductor L1 and the secondary side inductors L2 and L3 of the high frequency transformer 12 are physically separated from each other, there is a leakage inductance Lr due to the leakage flux. To do.

Therefore, in this configuration, in order to cancel the influence of the leakage inductance Lr, the high frequency inverter circuit 11 is switched at the resonance frequency F between the leakage inductance Lr and the resonance capacitor Cr. The resonance frequency F for energizing the 50% alternating current at this time is expressed by the following equation.

The timing at which the current flowing in the resonance circuit composed of the leakage inductance Lr and the resonance capacitor Cr becomes zero and the switching timing can be synchronized by the control circuits 2 and 4 whose current is monitored by the current sensor S2. Is.

In this case, the combined impedance of the leakage inductance Lr and the resonance capacitor Cr becomes zero due to the resonance, and the influence of the leakage inductance Lr can be canceled. Further, since the switching in the high frequency inverter circuit 11 is performed when the current flowing through the resonance circuit is zero, the loss due to the switching can be suppressed.

Therefore, it is possible to cancel the influence of the leakage inductance caused by the arrangement of the inductor of the high frequency transformer 12 while suppressing the switching loss of the high frequency inverter circuit 11.

In the above, it has been explained that switching is performed when the current flowing through the resonant circuit is zero, but this does not mean that the current flowing through the resonant circuit is exactly zero. That is, in a state where the current flowing through the resonance circuit is reduced to the extent that the switching loss can be suppressed, in other words, switching is performed even when the current is near zero or near zero.

Next, the operation of the charging device 100 will be described. FIG. 4 shows the charging operation of the charging device 100 according to the first embodiment. In this configuration, the charging device 100 starts charging the capacitor C while the capacitor C to be charged is not charged.

Step ST1
First, the constant current DC / DC converter CC starts operation and outputs a constant current to the capacitor C (constant current charging). As the charging of the capacitor C progresses, the voltage between both ends of the capacitor C rises. Along with this, the output voltage of the constant current DC / DC converter CC rises from 0.

Step ST2
The output voltage of the constant current DC / DC converter CC is monitored, and it is determined whether or not a predetermined voltage (maximum output voltage) V1 has been reached. The output voltage of the constant current DC / DC converter CC may be monitored autonomously by the constant current DC / DC converter CC, or may be performed by using the voltage measuring circuit 30.

Step ST3
When the output voltage of the constant current DC / DC converter CC reaches V1, which is the maximum output voltage, the operation of the constant current DC / DC converter CC is stopped.

Step ST4
After that, the operation of one of the constant voltage DC / DC converters CV1 to CVN is started. As a result, the voltage V1 is output from the constant voltage DC / DC converter that has started operation.

Step ST5
The voltage measuring circuit 30 monitors whether the charging voltage of the capacitor C (voltage of the common line CL) has reached the target voltage VT. If the charging voltage of the capacitor C (voltage of the common line CL) is smaller than the target voltage VT, the process returns to step ST1.

Step ST6
If the charging voltage of the capacitor C (voltage of the common line CL) is equal to or higher than the target voltage VT, the capacitor C is sufficiently charged, and the charging operation by the charging device 100 is stopped.

In the above procedure, steps ST1 to ST5 are repeated until the charging voltage of the capacitor C reaches the target voltage VT. As a result, each time the output voltage of the constant current DC / DC converter CC reaches V1, the number of constant voltage DC / DC converters that output the voltage V1 (that is, in the operating state) increases by one. Therefore, when all the constant voltage DC / DC converters CV1 to CVN are in the operating state, the charging voltage of the capacitor C can be increased up to (N + 1) × V1.

When the capacitor C is charged by repeating (repeating) steps ST1 to ST5 in this way, the constant current DC / DC converter CC and the constant voltage DC / DC converters CV1 to CVN are cascade-connected, so that charging is performed. The current is equal to the output current of the constant current DC / DC converter CC.

FIG. 5 shows the charging voltage of the capacitor C. The horizontal axis of FIG. 5 shows the number of constant voltage DC / DC converters that output the voltage V1. In this way, as the number of constant voltage DC / DC converters CVs outputting the voltage V1 increases, the charging voltage of the capacitor C rises, and all N DC / DC converters CV1 to CVN output the voltage V1. In this case, it can be understood that the charging voltage of the capacitor C is (N + 1) × V1.

For example, when the voltage V1 is about 2,800V and N = 3, the charging voltage of the capacitor C can be about 11,200V.

As described above, according to this configuration, when the capacitor is charged with a high charging voltage, the voltage output by each of the constant current DC / DC converter CC and the constant voltage DC / DC converters CV1 to CVN can be suppressed. It is possible to prevent the insulation from being destroyed.

Further, in the constant current DC / DC converter CC and the constant voltage DC / DC converters CV1 to CVN, since the primary side inductor and the secondary side inductor are physically separated from each other, the insulation failure resistance can be improved.

Other Embodiments The present invention is not limited to the above embodiments, and can be appropriately modified without departing from the spirit. For example, the configurations of the step-down chopper circuit and the high-frequency inverter circuit are not limited to the above examples. If the same functions as the above-mentioned constant current DC / DC converter and constant voltage DC / DC converter can be realized, a step-down chopper circuit and a high-frequency inverter circuit having other circuit configurations may be used.

Further, the configuration of the high frequency transformer is not limited to the above example. A transformer having another configuration in which the primary inductor and the secondary inductor are physically separated from each other may be used as appropriate. Further, as long as a transformer in which the primary side inductor and the secondary side inductor are physically separated from each other is used, the constant current DC / DC converter and the constant voltage DC / DC converter may be appropriately changed.

1 Current resonance type DC / DC converter 2 Control circuit 3 Step-down chopper circuit 4 Control circuit 11 High frequency inverter circuit 12 High frequency transformer 20 DC power supply 50 Voltage measurement circuit 100 Charging device C Capacitor CC Constant current DC / DC converter CL Common line CON control signal Cr Resonant Capacitor CV, CV1-CVN Constant Voltage DC / DC Converter GT Ground Terminal LT1, LT2 End NE Negative Negative PE Positive Positive R1, R2 Rectifier S1, S2 Current Sensor C1-C3 Smoothing Capacitor ST Power Terminal T1-T4, T31, T32 Transistor

Claims (7)

A constant current DC / DC converter that outputs a constant current with a variable output voltage between the ground voltage and a predetermined voltage.
A plurality of constant voltage DC / DC converters that output the predetermined voltage are provided.
The capacitor is charged by the voltage obtained by cascading the constant current DC / DC converter and the plurality of constant voltage DC / DC converters.
The constant current DC / DC converter and the plurality of constant voltage DC / DC converters output a voltage boosted by a step-up transformer in which the primary inductor and the secondary inductor are physically separated from each other.
Charging device. The constant current DC / DC converter and the constant voltage DC / DC converter are
Switching circuit and
Resonant capacitor and
A transformer in which the primary inductor is connected to the switching circuit via the resonant capacitor.
A rectifier that outputs a voltage obtained by rectifying the voltage induced in the secondary inductor of the transformer, and
A control circuit for controlling switching of the switching circuit is provided.
The charging device according to claim 1. The rectifier of the constant voltage DC / DC converter outputs the predetermined voltage.
The constant current DC / DC converter further includes a chopper circuit capable of adjusting the voltage input to the switching circuit.
In the constant current DC / DC converter, by controlling the switching between the chopper circuit and the switching circuit, the voltage output by the rectifier is controlled so that the current output from the rectifier becomes the constant current. ,
The charging device according to claim 2. The control circuit controls the switching of the switching circuit so that the switching frequency of the switching circuit substantially matches the leakage inductance generated by the leakage flux of the transformer and the resonance frequency of the resonance capacitor.
The charging device according to claim 2 or 3. The control circuit switches the switching circuit at a timing when the current flowing due to the resonance between the leakage inductance and the resonance capacitor becomes near zero.
The charging device according to claim 4. A step of constantly charging the capacitor with the constant current DC / DC converter and stopping the constant current charging when the output voltage of the constant current DC / DC converter reaches the predetermined voltage.
The capacitor is charged by the step of operating one of the plurality of constant voltage DC / DC converters and outputting the predetermined voltage from the one constant voltage DC / DC converter.
The charging device according to any one of claims 1 to 5. By repeating the two steps, the capacitor is charged.
The charging device according to claim 6.

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