TWI674721B - A voltage control device with automated voltage detection - Google Patents

Abstract

The voltage control device with automatic detection function of the present invention includes a voltage control unit and a signal control unit. The voltage control unit includes a high-voltage switch connected in series between the DC link capacitor and the reference potential terminal of the voltage supply, and has a control. A signal control unit is connected to the control terminal. By detecting the voltage level of the voltage supplier, when the voltage level exceeds a protection voltage value, a cut-off signal is output to the control terminal to open the high-voltage switch to cut off. The connection of the voltage supply end to the DC link capacitor achieves the purpose of protecting the motor driver from overvoltage.

Description

Voltage control device with automatic detection function

The invention relates to a voltage protection device with an automatic detection function, in particular to a protection device suitable for voltage detection and control of electric vehicles.

Due to the increasingly serious air pollution, countries around the world are committed to the development of electric vehicles based on environmental protection and environmental protection factors. Europe and the United States have also proposed that the production of gasoline vehicles be banned completely from 2035 to 2040. Electric vehicle power comes from the motor, which is controlled by the motor drive circuit. Motors can be roughly divided into two categories: induction motors and permanent magnet motors. When the motor speed is higher, the back-EMF is higher. At this time, if the back-EMF is higher than the battery voltage when the motor is operating in the generator mode, the battery can be charged.

A block diagram of a conventional motor drive circuit is shown in FIG. 1. The motor drive circuit includes a three-phase power switch 10 connected to a three-phase motor 12, and the three-phase power switch 10 receives a pulse width modulation by a signal control unit 11. The control of the signal (PWM) drives the three-phase motor 12 to operate. The three-phase power switch 10 is further connected to a battery DC link capacitor 13 and a battery 14 to supply the power required for the motor 12 to operate.

In the prior art, the new patent No. M500388 of the Republic of China proposes that when the voltage detection unit detects that the output voltage of the external power supply unit reaches the threshold voltage of the voltage control element, the voltage control element is turned on and the corresponding control potential is output to the switch unit. , Turn off the switch unit to protect the power supply unit. However, this technology cannot be used in isolated high-voltage systems, Overvoltages still do not provide protection.

In addition, the invention patent No. I381603 of the Republic of China proposes an overvoltage protection circuit for a pulse width modulation regulator, which includes: a power transistor, a control drive circuit to generate a pulse width modulation drive signal to drive one of the power transistors, And a voltage detection circuit detects a power supply voltage input to the power transistor, and when the power supply voltage reaches a preset voltage value, an overvoltage protection signal is output to turn off the pulse width modulation drive signal for the power transistor Driven. However, this technology only turns off the PWM, and it still cannot provide protection against overvoltages exceeding the withstand voltage of the component.

At present, the electric vehicle battery is not allowed to be charged when it is fully charged, but if the motor is running at a high speed, for example, the car is driving on a long downhill state, the back-EMF of the motor under no-load condition cannot be caused at this time. Charging the battery is too high, which will cause the voltage of the motor drive circuit to be too high and damage it. Therefore, it is necessary to develop a control method that can effectively control the voltage of the motor driving circuit so as to achieve the purpose of protecting the motor driving circuit.

To achieve the above object, the voltage control device with automatic detection function of the present invention includes a voltage control unit and a signal control unit, and a driving circuit of the signal control unit outputs a pulse width modulation signal (PWM) to drive a three-phase motor. ; A DC link capacitor is connected in parallel to the three-phase power switch and connected to a voltage supply terminal to supply the operating voltage of the three-phase motor, or the back-EMF of the three-phase motor is supplied to the voltage supply terminal; a high-voltage switch is connected to the DC A control terminal is provided between the link capacitor and a reference potential terminal of a voltage supply terminal; a signal control unit is connected to the control terminal and detects the voltage level on the voltage supply terminal when the voltage level exceeds a protection voltage value At this time, a cut-off signal is output to the control terminal to open the high-voltage switch to cut off the connection of the voltage supply terminal to the DC link capacitor and the three power switches.

The system of the present invention can automatically detect the voltage and wake up the microcontroller to enter the protection mode when the power is off. In addition, the present invention can prevent the back-EMF voltage from being too high during high-speed towing or improper driving and damage the motor driver.

10‧‧‧Three-phase power switch

12‧‧‧ three-phase motor

13‧‧‧DC link capacitor

14‧‧‧ Battery

20‧‧‧Signal Control Unit

21‧‧‧Microcontroller

22‧‧‧Drive circuit

23‧‧‧ Voltage Regulator

30‧‧‧Voltage Control Unit

31‧‧‧Voltage Detector

32‧‧‧ Comparator

33‧‧‧DC converter

34‧‧‧The first isolator

35‧‧‧Second isolator

40‧‧‧High-voltage switch

FIG. 1 is a block diagram of a conventional motor driver circuit.

FIG. 2 is a schematic circuit diagram of an embodiment of a voltage control device with an automatic detection function according to the present invention.

FIG. 3 is a schematic diagram of an automatic detection voltage control process of the present invention.

FIG. 4-1 is a schematic diagram of a process of performing a field weakening control according to the present invention.

Fig. 4-2 is a schematic diagram of a single-phase control flow of the present invention.

FIG. 5 is a schematic diagram of the phase current when the S1, S4, and S6 of the present invention are turned on.

The present invention is a voltage control device with an automatic detection function, which is used in a motor drive circuit of an electric vehicle. Please refer to FIG. 2 for a schematic circuit diagram of an embodiment of the voltage control device of the present invention. The voltage control device of the embodiment of the present invention has two protection mechanisms, the first is a voltage protection mechanism controlled by software, and the second is a voltage control mechanism controlled by hardware. The voltage control device of the present invention includes a signal control unit 20, a voltage control unit 30, a three-phase power switch 10, and a battery (BT3) 14. The signal control unit 20 further includes a microcontroller (MCU) 21 , A driving circuit 22 and a voltage regulator (U2) 23, and the voltage control unit 30 further includes an electric DC link capacitor 13, a voltage detector 31, a comparator (U1A) 32, and a high-voltage switch 40 .

First, the software-controlled voltage protection mechanism of the present invention is introduced. The microcontroller (MCU) 21 in the signal control unit 20 outputs a pulse width modulation signal (PWM). The moving circuit 22 is connected to the three-phase power switch 10 for driving the three-phase power switch 10 to drive the three-phase motor 12. The DC link capacitor 13 is connected in parallel to the three-phase power switch 10 and is further connected to a voltage supply terminal ( HV), the voltage supply terminal (HV) is connected to the battery (BT3) 14 to supply the operating voltage of the three-phase motor 12, or the back-EMF of the three-phase motor 12 is supplied to the voltage supply terminal (HV) to the battery (BT3 ) 14 charging.

The high-voltage switch 40 is connected between the DC link capacitor 13 and the battery 14. The high-voltage switch 40 has a control terminal connected to the microcontroller (MCU) 21 of the signal control unit 20. The control of the MCU) 21 is formed as an open circuit or a conducting circuit. When conducting, the DC link capacitor 13 is connected in parallel to the battery 14. The voltage detector 31 is connected to the voltage supply terminal (HV) to detect the voltage supply terminal. The voltage level on (HV) is output to the microcontroller (MCU) 21 through a first isolator 34. When the microcontroller (MCU) 21 determines that the voltage level on the voltage supply terminal (HV) exceeds one When the protection voltage value (Vn), a cut-off signal (HV CTL) is output to the control terminal of the high-voltage switch 40, and the high-voltage switch 40 is opened to cut off the DC link capacitor 13 in parallel with the battery 14, which means to cut off the The charging connection between the battery (BT3) 14 and the three-phase motor 12, otherwise, if the voltage level on the voltage supply terminal (HV) does not exceed the protection voltage value (Vn), the high voltage switch (S1) 40 Turn on, the battery (BT3) 14 is connected in parallel to the DC link capacitor 13, meaning that the battery (BT3) 14 is connected in parallel between the three-phase motors 12The protection voltage value (Vn) is set by the microcontroller (MCU) 21.

As is known to all, when the electric vehicle is accelerating, the battery (BT3) 14 supplies power to the three-phase motor 12, and the signal control unit 20 outputs a PWM signal to control the three-phase power switch 10 to drive the three-phase motor 12 to run. In the slope state, the three-phase motor 12 is switched to the generator mode, and the voltage generated by its back-EMF can charge the battery (BT3) 14, but if the battery (BT3) 14 is in a fully charged state and charging is not allowed. When the three-phase motor 12 is running in the power generation mode without load, the voltage (back-emf) generated by it will be too high, resulting in three-phase power. The switch 10 is damaged.

Therefore, in the present invention, the high-voltage switch 40 is connected between the DC link capacitor 13 and the battery 14. Preferably, the high-voltage switch 30 is connected to the DC link capacitor 13 as a ground terminal (GNDC) and the battery. Between the ground terminal (GNDHV) of 14, the voltage detector 31 can detect the voltage level of battery (BT3) 14 on the voltage supply terminal (HV). When the voltage level of battery (BT3) 14 exceeds a protection When the voltage value (Vn), a cut-off signal (HV CTL) is output to the control terminal of the high-voltage switch 40, and the high-voltage switch 40 is opened to cut off the parallel connection between the voltage supply terminal (HV) and the battery (BT3) 14. Connect without causing excessive voltage to damage the motor drive circuit.

In this embodiment, the battery (BT3) 14 is a lithium battery of an electric vehicle, and the output is high-voltage direct current. The three-phase power switch 10 may be a three-phase MOSFET or an insulated gate bipolar transistor (IGBT). The DC link capacitor 13 is a series capacitor (C1n ~ Cnn). The high-voltage switch 40 may be a switch control circuit composed of a MOSFET or a relay.

The following describes the hardware-protected voltage control mechanism of the present invention. The voltage detector 31 of the voltage control unit 30 of the present invention is connected to the voltage supply terminal (HV) to detect the voltage of the battery (BT3) 14. The voltage level outputs a potential signal value (V1). The comparator (U1A) 32 compares whether the potential signal value (V1) exceeds a set potential value (VTH). If it exceeds, a signal is output through a second isolator 35 WK_HV enables the voltage regulator (U2) 23.

The comparator (U1A) 33 has a first comparison terminal, a second comparison terminal, and an output terminal. The first comparison terminal is connected to the voltage detector 31 and receives the potential signal value (V1). The second comparison terminal is connected to a set potential value (VTH). When the potential signal value (V1) is greater than the When setting the potential value (VTH), its output terminal outputs a high potential signal (WK_HV), otherwise it outputs a low potential signal. The voltage regulator (U2) 23 has an output control terminal (CTL) connected to the output terminal of the comparator (U1A) 32. When the comparator (U1A) 32 outputs a high potential signal (WK_HV), the voltage regulator The output terminal (OUT) of the comparator (U2) 23 outputs a working voltage (+ VDD) to provide the microcontroller (MCU) 21 and other circuits with operating power. When the comparator (U1A) 31 outputs a low potential signal, the The voltage regulator (U2) 23 turns off the output of the working voltage (+ VDD), so that the microcontroller (MCU) 21 enters the power-off sleep state.

The set potential value (VTH) is converted from the voltage supply terminal (HV) to a circuit voltage (+ Vcc) through the DC converter 33, and then formed by dividing the two resistors (R1, R3). The set potential The value (VTH) can be determined by adjusting the resistance of the two resistors (R1, R3). The voltage regulator (U2) 23 is powered by a vehicle-mounted system battery (BT1) and converted into a stable voltage of the working voltage (+ VDD). The output control terminal (CTL) of the voltage regulator (U2) 23 is further connected with a start-up power signal (V_IGN). When the vehicle starts, the start-up power signal (V_IGN) is high, indicating that the vehicle is in the power-on state. At this time, the voltage regulator (U2) 23 outputs the working voltage (+ VDD).

Please refer to FIG. 3, which is a schematic diagram of a control flow of automatic voltage detection according to the present invention. The microcontroller (MCU) 21 of the present invention can be operated in a normal mode or an active protection mode, wherein the microcontroller (MCU) 21 is operated in the normal mode to be a normal driving state of the vehicle. When the electric vehicle is in the startup state, the start-up power signal (V_IGN) is ON at high potential (S401), then the microcontroller (MCU) 21 starts (S402) in normal mode. If the start-up power signal (V_IGN) is low, but the comparator (U1A) 32 outputs a high-level normal signal (WK_HV) (S403), the microcontroller (MCU) 21 starts (S402) normal mode. If the start-up power signal (V_IGN) is low and the comparator (U1A) 32 output is also a low-level abnormal signal, it means that the microcontroller (MCU) 21 is turning off the power Hibernation.

When the microcontroller (MCU) 21 starts (S402) in normal mode, it will detect whether the voltage level of the battery (BT3) 14 is in an excessively high state. When the potential signal value (V1) is less than the protection voltage value (Vn ) (S404) indicates that the battery voltage is normal, the high-voltage switch (S1) is controlled to be turned on (S405), and the subsequent process (S410) is entered. The back-EMF of the three-phase motor 12 can charge the battery (BT3) 14. When the potential signal value (V1) is greater than the protection voltage value (Vn) plus the hysteresis voltage (△ V) (S406), it indicates that the voltage level of the battery is too high, then the high voltage switch (S1) is controlled to open (S407) To cut off the danger of the battery to the motor driver. At this time, the back electromotive force of the three-phase motor 12 cannot charge the battery (BT1) 14. If the motor continues to run at this time, the microcontroller (MCU) 21 enters the active voltage control mode (S408), and the voltage is immediately reduced to protect the three-phase power switch 10 and the DC link capacitor 13 from damage caused by overvoltage. If the potential signal value (V1) is greater than the protection voltage value (Vn), but less than the protection voltage value (Vn) plus the hysteresis voltage (△ V), the high voltage switch (S1) is also controlled to be turned on (S409), and the subsequent process is entered. (S410).

When the microcontroller (MCU) 21 operates in the active protection mode, the vehicle is in a high-speed towing state or the vehicle is in a high-speed driving state when the power is turned off. The start-up power signal (V_IGN) is a low potential (Off), and the voltage regulation (U2) 23 does not output the operating voltage (+ VDD), the microcontroller (MCU) 21 is in the power-off state, but the back-EMF of the three-phase motor 12 makes the voltage value of the voltage supply terminal (HV) greater than the set potential Value (VTH), so the regulator (U2) 23 outputs the operating voltage (+ VDD) to start the microcontroller (MCU) 22.

Please refer to FIG. 4-1, FIG. 4-2 and FIG. 5 together. FIG. 4-1 is a schematic diagram of the implementation of the field weakening control process of the active voltage control of the present invention. The Id size depends on the speed of the voltage drop and the allowable range. . Figure 4-2 is a schematic diagram of a single-phase control flow for active voltage control of the present invention, such as S1 ON, then S4, S6 ON, Duty decides how fast the voltage drops. Similarly, the combination of S3, S2, S6 and S5, S2, S4 is also the same. FIG. 5 is a schematic diagram of the phase currents when the three-phase power switches S1, S4, and S6 of the present invention are turned ON. The figure shows that when there is a current load, the DC link capacitor voltage should gradually decrease to a safe range.

Claims (13)

A voltage control device with automatic detection function includes: a three-phase power switch, controlled by a signal control unit to output a pulse width modulation signal (PWM), driving a three-phase motor; DC link capacitor , Connected in parallel to the three-phase power switch, connected to a voltage supply terminal of a battery to supply the operating voltage of the three-phase motor, or the back-EMF of the three-phase motor is supplied to the voltage supply terminal to charge the battery; a high-voltage switch, Connected in series between the DC link capacitor and a reference potential terminal, with a control terminal; a voltage detector connected to the voltage supply terminal for detecting the voltage level of the battery on the voltage supply terminal; and A microcontroller, connected to the output terminal of the voltage detector and the control terminal of the high voltage switch, judges the voltage level of the battery, and when the voltage level exceeds a protection voltage value, outputs a cut-off signal to the control Open the high-voltage switch to cut off the connection of the voltage supply terminal to the battery; wherein, the microcontroller operates in a normal mode to detect the battery for the normal driving state of the vehicle Whether the voltage level is fully charged, output a potential signal value, when the potential signal value is less than the protection voltage value, the back electromotive force of the three-phase motor can charge the battery, when the potential signal value is greater than the protection voltage value , Then output the cut-off signal to the control end of the high-voltage switch to cut off the charging connection of the battery by the back electromotive force of the three-phase motor. The voltage control device with automatic detection function according to claim 1, wherein the three-phase power switch is a three-phase MOSFET or an insulated gate bipolar transistor (IGBT). The voltage control device with automatic detection function according to claim 1, wherein the DC link capacitor is formed by a plurality of capacitors connected in series. The voltage control device with automatic detection function according to claim 1, wherein the high-voltage switch is a switch control circuit composed of a MOSFET or a relay. The voltage control device with automatic detection function according to claim 1, wherein the reference potential terminal is a ground terminal. The voltage control device with automatic detection function as described in claim 1, wherein an isolator is further provided between the microcontroller and the voltage detector. The voltage control device with automatic detection function as described in claim 1, wherein the protection voltage value is set by the microcontroller. A voltage control device with automatic detection function includes: a three-phase power switch, controlled by a signal control unit to output a pulse width modulation signal (PWM), driving a three-phase motor; DC link capacitor , Connected in parallel to the three-phase power switch, connected to a voltage supply terminal of a battery to supply the operating voltage of the three-phase motor, or the back-EMF of the three-phase motor is supplied to the voltage supply terminal to charge the battery; a high-voltage switch, Connected in series between the DC link capacitor and a reference potential terminal, with a control terminal; a voltage detector connected to the voltage supply terminal for detecting the voltage level of the battery on the voltage supply terminal; and A microcontroller, connected to the output terminal of the voltage detector and the control terminal of the high voltage switch, judges the voltage level of the battery, and when the voltage level exceeds a protection voltage value, outputs a cut-off signal to the control Open the high-voltage switch to cut off the connection of the voltage supply terminal to the battery; wherein the microcontroller operates in an active protection mode, which means that the vehicle is in a high-speed towing state or off When the vehicle is in a high-speed driving state, a starting power signal is low, a voltage regulator does not output an operating voltage (VDD), the microcontroller is in a sleep state, but the voltage supply terminal is caused by the back-EMF of the three-phase motor The voltage value is greater than a set potential value, so the regulator outputs the working voltage (VDD) to start the microcontroller. A voltage control device with automatic detection function includes: a DC link capacitor connected to a voltage supply terminal of a battery; a voltage detector connected to the voltage supply terminal for detecting the voltage of the voltage supply terminal Level, outputting a potential signal value; and a comparator, having a first comparison terminal, a second comparison terminal and an output terminal, the first comparison terminal is connected to the voltage detector and receives the potential signal value, Wherein the second comparison terminal is connected to a set potential value, when the potential signal value is greater than the set potential value, a high potential normal signal is output, otherwise a low potential abnormal signal is output; and a voltage regulator has an output The control terminal is connected to the output of the comparator. When the comparator outputs the high-level normal signal, it outputs an operating voltage to provide the power required by the microcontroller. When the comparator outputs the low-level abnormal signal, it is turned off. The output of this working voltage. The voltage control device with automatic detection function as described in claim 9, wherein the set potential value is converted from the voltage supply terminal to a circuit voltage by a DC converter, and then formed by dividing the voltage by two resistors. The potential value can be determined by adjusting the voltage divider resistance value of the two resistors. The voltage control device with automatic detection function as described in claim 9, wherein the regulator is the working voltage converted from a vehicle-powered system battery to a stable voltage. The voltage control device with automatic detection function according to claim 9, wherein an isolator is further provided between the voltage regulator and the output terminal of the comparator. The voltage control device with automatic detection function as described in claim 9, wherein the output control terminal of the voltage regulator is further connected to a starting power signal, and the starting power signal is high when the vehicle is started, so that the voltage is stabilized The device outputs the working voltage.