JP7349371B2 - discharge control circuit - Google Patents

Description

The present invention relates to a discharge control circuit.

A discharge circuit for a DC power supply smoothing capacitor that reliably stops discharging when a failure occurs is known (for example, see Patent Document 1).

Patent Document 1 proposes means for discharging a capacitor by separately preparing a controller exclusively for discharge control, which draws power from the voltage accumulated in a voltage smoothing capacitor.

Japanese Patent Application Publication No. 2011-41363

In the method of Patent Document 1, when the discharge control of the VB or the motor controller fails, the discharge-only controller takes charge of the discharge. The discharge controller monitors the voltage value of the voltage smoothing capacitor, and when the battery and the voltage smoothing capacitor are connected by a contactor and the voltage does not drop even if the discharge switch element is turned on, the discharge controller monitors the voltage value of the voltage smoothing capacitor. The discharge switch element is turned off to stop the discharge midway.

Furthermore, in case the contactor is turned off after that, it has a function of testing the discharge process at regular intervals.

However, because of this function that enters the discharging process at regular intervals, for example, when charging the battery with the ignition IGN turned off and the motor controller not started, the battery and voltage smoothing capacitor are connected by a contactor. In this state, the discharge treatment is repeated at regular intervals. When the discharge process is performed at regular intervals, a voltage is applied to the discharge resistor for a predetermined period of time, causing a loss of V^2/R and increasing the temperature of the resistor. In addition to being a loss in terms of energy, this also leads to deterioration of the discharge resistance.

An object of the present invention is to provide a discharge control circuit that solves the above problems, eliminates unnecessary energy loss during charging, and prevents deterioration of discharge resistance.

In order to achieve the above object, the present invention provides a discharge control circuit comprising a switch element connected in series to a discharge resistor, and a microcomputer that controls the switch element, wherein the discharge resistor controls the switch element. The microcomputer is connected in parallel to a capacitor via a contactor, and the capacitor is connected in parallel to a battery via a contactor, and when a discharge command indicating start or stop of discharge is input from an external controller, the microcomputer is configured to perform a discharge command according to the discharge command. outputting a first control signal that turns on/off the switch element; and outputting a second control signal that turns off the switch element when the discharge command is not input from the external controller and the battery is in a charging state; Output.

According to the present invention, unnecessary energy loss during charging can be eliminated and deterioration of the discharge resistance can be prevented. Problems, configurations, and effects other than those described above will be made clear by the following description of the embodiments.

FIG. 2 is a block diagram of a motor drive system. 1 is a block diagram illustrating a discharge control circuit according to Example 1 of the present invention. FIG. FIG. 3 is a timing chart diagram illustrating discharge control according to Example 1 of the present invention. FIG. 3 is a timing chart diagram illustrating control during charging according to Example 1 of the present invention. It is a block diagram explaining the discharge control circuit concerning Example 2 of the present invention. It is a figure explaining the discharge prohibition mode based on Example 2 of this invention. FIG. 2 is a block diagram illustrating a specific example A of a discharge control circuit according to a second embodiment of the present invention. FIG. 3 is a block diagram illustrating a specific example B of a discharge control circuit according to a second embodiment of the present invention.

Next, a discharge control circuit according to an embodiment of the present invention will be described in detail below with reference to the drawings. Note that embodiments of the present invention relate to a power conversion device (inverter device), and particularly to internal charge discharge control of a power conversion device for a vehicle.

(Configuration of motor drive system)
FIG. 1 shows the configuration of a motor drive system including a motor drive inverter device, which is an example (comparative example) of a power conversion device. 900 is a motor, 200 is an inverter device (inverter device for driving a motor), 901 is a battery (high voltage battery), and 902 is a contactor that controls the connection between the inverter device and the battery 901.

The inverter device 200 includes, as main components, a capacitor 500 (voltage smoothing capacitor) that smoothes the DC voltage input to the inverter, a power semiconductor module 250 in which power semiconductor elements are modularized, a driver circuit 102 (gate driver circuit), and a motor. It is composed of a controller 101 (controller for motor control). A higher-level controller (not shown) gives commands for driving the motor, such as torque and rotation commands, to the motor controller 101, and the motor controller 101 transmits a PWM signal according to the commands to the driver circuit 102. The driver circuit 102 controls switching of the power semiconductor module 250 (power semiconductor) according to the PWM signal, and converts the DC voltage from the battery 901 into an AC voltage for driving the motor 900.

Other safety components include a voltage sensor 60, a discharge resistor 70, and a discharge switch 71 (discharge switch). After driving the motor, inverter device 200 is electrically disconnected from battery 901 by turning off contactor 902 in accordance with a command from the host controller. However, the voltage from when the capacitor 500 in the inverter device 200 was connected to the battery 901 remains.

Since there is a possibility that a worker may touch the inside of the inverter device for maintenance after the motor has stopped, a means is usually provided to rapidly discharge the charge remaining in the capacitor after the motor has stopped driving. For example, this means turns on the discharge switch 71 after the motor is stopped, and reduces the voltage of the capacitor 500 by the discharge resistor 70.

However, if the low-voltage battery voltage VB that supplies voltage to the motor controller 101 is lost for some reason, or if the motor controller 101 breaks down, discharge control cannot be performed and electric charges remain in the inverter device. It turns out.

(Example 1)
FIG. 2 shows a circuit block diagram according to the first embodiment of the present invention. In FIG. 2, a vehicle controller 105 sends torque and rotation commands to the motor controller 101 to control the state of the vehicle.

A battery controller 106 monitors the state of the battery 901, such as the amount of charge, and when a charging connector is connected to the charging connector 905, it detects it, communicates with an external charging device (not shown), and connects the contactor. 902 is turned on and the charging device and battery 901 are connected. It also has a function of detecting and determining that it is in a charging state and transmitting the fact that it is in a charging state to an external controller (microcomputer 310) (charging mode detection signal 335).

The motor controller 101 controls the motor 900 according to the rotation and torque instructions from the vehicle controller 105, as described above, and also sends a command to discharge the remaining charge in the capacitor 500 when the vehicle is stopped or abnormal.

300 is a discharge control circuit, which is composed of a microcomputer 310, a microcomputer power supply 311, a power supply 312, and the like.

312 is a power supply that outputs 7V from the high voltage input to the microcomputer power supply.

311 is a microcomputer power supply that outputs 5V from a 7V input to be supplied to the microcomputer 310, and also has a monitoring function for the microcomputer 310.

310 is a microcomputer (discharge microcomputer), which inputs a first control signal to the discharge switch 71 via the buffer 315 to turn on the discharge switch 71 in accordance with the discharge command 330 from the motor controller 101, thereby causing the discharge resistor 70 to , performs a process of discharging the remaining charge of the capacitor 500.

In other words, the discharge control circuit 300 includes at least a discharge switch 71 (switch element) connected in series to the discharge resistor 70 and a microcomputer 310 that controls the discharge switch 71. Discharge resistor 70 is connected in parallel to capacitor 500 via discharge switch 71, and capacitor 500 is connected in parallel to battery 901 via contactor 902. When a discharge command 330 indicating the start or stop of discharge is input from the motor controller 101 (external controller), the microcomputer 310 generates a control signal 332 (first control signal) that turns on/off the discharge switch 71 according to the discharge command 330. ) is output. As a result, the charge in the capacitor 500 is discharged in accordance with the discharge command 330 from the motor controller 101 (external controller).

The discharge command 330 is executed by a duty command from the motor controller 101 during normal discharge, and is a discharge command when the duty is 75%, and a discharge stop command when the duty is 25%. The microcomputer 310 (discharge microcomputer) performs discharging processing according to instructions from the motor controller 101.

In other words, the discharge command 330 is composed of a signal indicating the duty ratio. When the duty ratio is 75% (first set value), the discharge command 330 indicates the start (execution) of discharge, and when the duty ratio is 25% (second set value), the discharge command 330 indicates the stop of discharge. . Note that if the signal is fixed, the microcomputer 310 determines that the discharge command 330 is not input from the motor controller 101 (external controller). Thereby, it is possible to easily determine whether or not a discharge command has been input.

Next, a discharge process in an abnormal state in a normal discharge process will be described using FIG. 3. Normal discharge processing is performed by the microcomputer 310 inputting a first control command to the discharge switch 71 in response to a discharge duty command from the motor controller 101. However, when the discharge command 330 is fixed at H or L, it is determined that there is an abnormality in the motor controller 101 or the signal line of the discharge command 330, and the microcomputer 310 manages the discharge process. A drive signal sent from the microcomputer 310 to the discharge switch 71 while the microcomputer 310 is managing the discharge is called a second control signal.

At this time, if the contactor 902 is turned off and the capacitor 500 and the battery 901 are disconnected, the voltage of the capacitor 500 will drop and the discharge process will be performed without any problem, but if the contactor 902 is turned on due to some abnormality. There are cases where the status remains the same.

In this case, if the discharge switch 71 remains on, the temperature of the discharge resistor 70 will rise due to the loss of V^2/R, and the discharge resistor 70 will burn out due to overtemperature. Therefore, the microcomputer 310 monitors the voltage drop of the capacitor 500, and stops the discharging process if the voltage drop is below a certain value. Then, after a predetermined period of time Tintv, the discharge process is repeated. Thereafter, when the contactor 902 is turned off, the voltage of the capacitor 500 decreases without any problem, so the discharge process is continued, and when the voltage drops below a certain level, the process of turning off the discharge switch 71 is performed.

Next, the operation when charging the battery 901 will be described using FIG. 4.

When charging the battery 901, a charging device (not shown) is connected to the charging connector 905 via a cable, and charging control is performed while communicating with the battery controller 106. When the charging connector is connected, the contactor 902 is turned on to connect the external charging device and the battery 901.

Furthermore, during charging, the motor controller 101 is in a stopped state without receiving the VIGN signal, so the microcomputer 310 manages the discharging process. Here, as described above, in the microcomputer 310, when the voltage of the capacitor 500 exceeds a certain level, the power supply 312 is activated and the microcomputer 310 is also activated.

Thereafter, a charging mode detection signal 335 is transmitted from the battery controller 106 and received by the microcomputer 310, thereby recognizing that the microcomputer 310 is in the charging mode and stopping the discharging process.

In other words, if a discharge command is not input from the motor controller 101 (external controller) and the battery 901 is in a charging state, the microcomputer 310 generates a control signal 332 (second control signal) that turns off the discharge switch 71 (switch element). signal). As a result, discharging is stopped when the discharge command 330 is not input and the battery 901 is in a charging state. As a result, unnecessary energy loss during charging can be eliminated and deterioration of the discharge resistor 70 can be prevented.

In this embodiment, when the microcomputer 310 receives a charging mode detection signal 335 (detection signal) indicating that the battery 901 is in a charging state from the battery controller 106 that detects that the battery 901 is in a charging state, the microcomputer 310 detects that the battery 901 is in a charging state. is determined to be in a charging state. Thereby, the charging state can be determined based on the charging mode detection signal 335 from the battery controller 106.

In the technique disclosed in Patent Document 1, when the discharge command 330 (input signal) is fixed at L, the microcomputer 310 starts the discharge process. During charging, the battery 901 and the capacitor 500 are connected by the contactor 902, so in order to protect the discharge resistor 70, the discharge process + stop is performed while monitoring the voltage of the capacitor 500, in the same way as when the contactor is abnormal as described above. This was repeated during charging, causing loss in the discharge resistor 70 and leading to accelerated deterioration due to a rise in temperature of the discharge resistor 70, but this embodiment can prevent this.

As described above, according to this embodiment, unnecessary energy loss during charging can be eliminated and deterioration of the discharge resistance can be prevented.

(Example 2)
Next, Example 2 of the present invention will be described using FIG. 5.

In the second embodiment, 350 is a discharge prohibition mode detection section. Using the low voltage battery voltage VB and the ignition signal VIGN as input, it determines a mode in which discharging of the charge of the capacitor 500 by the discharge resistor 70 is prohibited, and the microcomputer 310 is stopped by a reset signal 337.

Specifically, the discharge prohibition mode detection unit 350 operates according to the logic shown in FIG.

Conditions 1 and 2 assume that VB is at the L level, the vehicle crashes and VB is disconnected, the output becomes H, and the microcomputer 310 operates according to the state of the discharge command 330. Since there is no VB, the discharge command is fixed at the L level, so the microcomputer 310 enters the discharge management state.

Condition 3 is a state in which VB is at H level and VIGN is at L level, VB is connected and IGN is turned off. The output becomes L, the microcomputer 310 is reset, and the discharge process is stopped. It is assumed that a charger is connected to charging connector 905.

In other words, the discharge prohibition mode detection unit 350 (discharge prohibition circuit) activates the discharge switch 71 (switch element) when VB (low voltage battery voltage) is at H level and VIGN (ignition signal) is at L level. Turn off. Thereby, for example, when a charger is connected to charging connector 905 and the power switch of the vehicle is off, discharging is prohibited (stopped).

In this embodiment, the discharge prohibition mode detection unit 350 (discharge prohibition circuit) resets the microcomputer 310 when VB (low voltage battery voltage) is at H level and VIGN (ignition signal) is at L level. Discharge is prohibited (stopped) by resetting the microcomputer 310.

Condition 4 is a state in which VB is at H level and VIGN is at H level, and the motor controller is turned on and motor control can be performed. The output is H, and the microcomputer 310 is operating. The microcomputer 310 turns on and off the discharge switch 71 in response to a discharge stop command from the motor controller 101.

(Specific example A)
Next, specific example A of the second embodiment will be described using FIG. 7.

In FIG. 7, D1 and D2 are diodes. R11, R12, R21, and R22 are resistors. TR1 and TR2 are FETs. 355 is a photocoupler which is an insulating element.

TR1 is turned on when the VB input is at a predetermined level or higher, turns on the photocoupler 355, sets the output to L, sets the reset signal of the microcomputer 310 to L, and stops the discharge microcomputer.

Here, when VIGN reaches a predetermined level or higher, TR2 is turned on, and by setting the gate of TR1 to L level, TR1 is turned off, the photocoupler 355 is turned off, the output signal becomes H, and the reset signal of the microcomputer 310 is It is released and the microcomputer 310 returns to normal operation. Note that although a photocoupler is used in this embodiment, other insulating elements may also be used.

In other words, the discharge prohibition mode detection unit 350 (discharge prohibition circuit) detects a photocoupler 355 (insulating element) that turns on when VB (low voltage battery voltage) is at H level and VIGN (ignition signal) is at L level. ), and a resistor R3 whose one end is connected to the collector of the photocoupler 355 and whose other end is connected to the power supply 312. A reset terminal of the microcomputer 310 is connected to a connection point between the collector of the photocoupler 355 and the resistor R3.

As a result, when the photocoupler 355 (insulating element) is turned on, the voltage at the reset terminal is switched from the H level to the L level. Furthermore, since a reset terminal (port) generally provided in the microcomputer 310 is used, manufacturing costs can be reduced.

Note that the discharge control circuit 300 is supplied with power from the capacitor 500. Thereby, discharge control can be performed even when the contactor 902 is off.

(Specific example B)
Next, specific example B of the second embodiment will be described using FIG. 8.

In FIG. 8, the collector terminal of the output transistor of the photocoupler 355 is connected to the gate terminal of the discharge switch 71. By setting the gate terminal of the discharge switch 71 to the L level when VB is at the H level and VIGN is at the L level, the discharge can be stopped regardless of the control by the microcomputer 310.

In other words, the discharge prohibition mode detection unit 350 (discharge prohibition circuit) activates the discharge switch 71 (switch element) when VB (low voltage battery voltage) is at H level and VIGN (ignition signal) is at L level. The level of the gate terminal (control terminal) of the discharge switch 71 is changed so as to turn it off. As a result, for example, when a charger is connected to the charging connector 905 and the power switch of the vehicle is off, discharging is prohibited (stopped) by directly turning off the discharging switch 71 without going through the microcomputer 310. Note that since the discharge switch 71 of this embodiment is an NMOS (Negative-channel Metal Oxide Semiconductor), for example, the discharge switch 71 can be turned off by changing the level of the gate terminal (control terminal) from the H level to the L level. do.

Specifically, the discharge prohibition mode detection unit 350 (discharge prohibition circuit) detects a photocoupler 355 (insulating element) that is turned on when VB (low voltage battery voltage) is at H level and VIGN (ignition signal) is at L level. ), and a resistor R3 whose one end is connected to the collector of the photocoupler 355 and whose other end is connected to the gate terminal (control terminal) of the discharge switch 71 (switch element). Thereby, the switch element can be reliably turned off regardless of the state (normal/abnormal) of the microcomputer.

According to the discharge control circuit according to the second embodiment, it is possible to prevent the discharge resistor from repeatedly discharging during charging, causing loss in the discharge resistor, and accelerating deterioration due to temperature rise of the discharge resistor.

Note that the present invention is not limited to the above-described embodiments, and includes various modifications. For example, the embodiments described above are described in detail to explain the present invention in an easy-to-understand manner, and the present invention is not necessarily limited to having all the configurations described. Furthermore, it is possible to replace a part of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of one embodiment. Further, it is possible to add, delete, or replace a part of the configuration of each embodiment with other configurations.

Further, each of the configurations, functions, etc. described above may be partially or entirely realized by hardware, for example, by designing an integrated circuit. Furthermore, each of the above-mentioned configurations, functions, etc. may be realized by software by a processor (microcomputer) interpreting and executing a program for realizing each function. Information such as programs, tables, files, etc. that realize each function can be stored in a memory, a recording device such as a hard disk, an SSD (Solid State Drive), or a recording medium such as an IC card, an SD card, or a DVD.

In addition, the following aspects may be sufficient as the Example of this invention.

(1). A discharge control circuit that discharges charges accumulated in a capacitor element by controlling on/off of a semiconductor switching element connected in series with a discharge resistor, the semiconductor switching element discharging the charge accumulated in a capacitor element based on a discharge instruction from an external controller (MC). A discharge control IC that outputs a first control signal that controls the element, and a charging mode detection unit that detects or determines that a DC battery connected to the capacitor element via a contactor is in a charging state, The discharge control IC has a function of determining an abnormal state and outputting a second control signal to control the semiconductor switching element when there is no discharge instruction from the external controller, and a function of outputting a second control signal for controlling the semiconductor switching element. A discharge control circuit, wherein the discharge control IC prohibits output of the second control signal when it is detected or determined that the DC battery is in a charging state.

This makes it possible to provide a discharging means that stops discharging during charging, eliminates unnecessary energy loss due to the discharging resistance, and prevents deterioration of the discharging resistor.

(2). A discharge control circuit that discharges charges accumulated in a capacitor element by controlling on/off of a semiconductor switching element connected in series with a discharge resistor, the semiconductor switching element discharging the charge accumulated in a capacitor element based on a discharge instruction from an external controller (MC). The discharge control IC includes a discharge control IC that outputs a first control signal for controlling the element, and a discharge prohibition mode detection section that detects or determines that there is a possibility that the contactor and the capacitor element are connected. has a function of determining an abnormal state and outputting a second control signal to control the semiconductor switching element when there is no discharge instruction from the external controller; The discharge control circuit is characterized in that the discharge control IC prohibits output of the second control signal when it is detected or determined that the mode is set.

Thereby, it is possible to provide a discharging means that eliminates unnecessary energy loss due to the discharging resistor and prevents deterioration of the discharging resistor when the external controller is not activated and is in the charging state.

(3). The discharging prohibition mode detection unit described in (2) uses the low-voltage battery voltage and the ignition signal as input signals, uses the output of the isolated power supply that receives the voltage accumulated in the capacitor element as the input signal, and uses the output of the isolated power supply as the input signal, and the signal is transmitted through the signal isolation element. and sends an output signal to the discharge control IC, and only when the low voltage system battery voltage exceeds a predetermined voltage and the ignition signal is below a predetermined voltage, there is a possibility that the contactor and the capacitor element are connected. The present invention is characterized in that it detects or judges that there is a discharge control IC, and sends a signal to the discharge control IC to inhibit output (discharge).

It is possible to provide a discharging means that eliminates unnecessary energy loss due to the discharging resistor when the external controller is not activated and during charging, and prevents deterioration of the discharging resistor. In addition, since the energy for transmitting the signal output of the external controller activation detection section to the discharge control IC on the high voltage side is received from the output of the isolated power supply whose input is the voltage accumulated in the capacitor element, the current consumption from the low voltage battery is reduced. It can be suppressed.

50 Current sensor 70 Discharge resistor 71 Discharge switch 101 Motor controller 102 Driver circuit 200 Inverter device 250 Power semiconductor module 500 Capacitor 900 Motor 901 Battery 902 Contactor VB Low voltage system battery voltage VIGN Ignition signal 105 Vehicle controller 106 Battery controller 300 Discharge control circuit 310 Microcomputer 311 Microcomputer power supply 312 Power supply 314 Voltage detection unit 315 Buffer 320 Discharge command isolation element 321 Error signal isolation element 322 Charge mode detection signal Insulation element 330 Discharge command 331 Discharge error signal 335 Charge mode detection signal 350 Discharge prohibition mode detection unit 400 Battery controller 402 Charging connector communication command 403 Contactor control command 905 Charging connector

Claims (9)

a switch element connected in series to the discharge resistor;
A discharge control circuit comprising: a microcomputer that controls the switch element;
The discharge resistor is connected in parallel to the capacitor via the switch element,
the capacitor is connected in parallel to a battery via a contactor;
The microcomputer is
When a discharge command indicating the start or stop of discharge is input from an external controller, outputting a first control signal to turn on/off the switch element according to the discharge command;
A discharge control circuit configured to output a second control signal that turns off the switch element when the discharge command is not input from the external controller and the battery is in a charging state. The discharge control circuit according to claim 1,
The microcomputer is
A discharge control circuit that determines that the battery is in a charging state when it receives a detection signal indicating that the battery is in a charging state from a battery controller that detects that the battery is in a charging state. The discharge control circuit according to claim 1,
A discharge control circuit comprising: a discharge prohibition circuit that turns off the switch element when the voltage of the low-voltage battery is at H level and the ignition signal is at L level. The discharge control circuit according to claim 3,
The discharge prohibition circuit is
A discharge control circuit that resets the microcomputer when the voltage of the low-voltage battery is at H level and the ignition signal is at L level. The discharge control circuit according to claim 3,
The discharge prohibition circuit is
A discharge control circuit characterized in that when the voltage of a low-voltage battery is at H level and the ignition signal is at L level, the level of a control terminal of the switch element is changed so as to turn off the switch element. The discharge control circuit according to claim 4,
The discharge prohibition circuit is
an insulating element that turns on when the voltage of the low-voltage battery is at H level and the ignition signal is at L level;
a resistor whose one end is connected to the collector of the insulating element and whose other end is connected to a power supply,
The reset terminal of the microcomputer is
A discharge control circuit connected to a connection point between the collector of the insulating element and the resistor. The discharge control circuit according to claim 5,
The discharge prohibition circuit is
an insulating element that turns on when the voltage of the low-voltage battery is at H level and the ignition signal is at L level;
A discharge control circuit comprising: a resistor whose one end is connected to the collector of the insulating element and whose other end is connected to the control terminal of the switch element. The discharge control circuit according to claim 1,
The discharge control circuit includes:
A discharge control circuit, wherein power is supplied from the capacitor. The discharge control circuit according to claim 1,
The discharge command is
Consists of a signal indicating the duty ratio,
When the duty ratio is a first set value, it indicates the start of discharge,
When the duty ratio is a second set value, it indicates a stop of discharging;
The microcomputer is
A discharge control circuit characterized in that, if the signal is fixed, it is determined that the discharge command is not input from the external controller.

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