Low voltage system passive discharge circuit and method of using same

Abstract

The present application relates to the field of device for protecting transformer, specifically to a low-voltage system passive discharge circuit and its using method. A low-voltage system passive discharge circuit, comprising a DC power supply (1), characterized in that: further comprising an energy storage capacitor (2), a pull-up resistor (31), a pull-down resistor (32), a discharge resistor (33), a field effect transistor (4) and a movable break contact (5), the three junctions of one end of the energy storage capacitor (2), one end of the pull-up resistor (31) and the drain of the field effect transistor (4) are connected to the positive pole of the DC power supply (1) through a control bus (6) in series with the movable break contact (5); the other end of the energy storage capacitor (2) is connected to the negative pole of the DC power supply (1). The using method of the low-voltage system passive discharge circuit, characterized in that: the following steps are implemented in sequence: ① closing; ② opening. The present application has compact structure, reduces power consumption, is flexible in configuration and safe and reliable.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of devices for protecting a converter, in particular a low-voltage system passive discharge circuit and a method for using the same. BACKGROUND

[0002] At present, the low-voltage system passive discharge circuit mainly releases energy through a plurality of discharge resistors in parallel. When the main circuit is powered on, all power supplies are loaded on the discharge resistors, and the discharge resistors continuously operate at high power consumption; when the main circuit switch is turned off, the energy of the DC-Link energy storage capacitor is released through the discharge resistor, and the controller side bus voltage rapidly decreases to ensure that the power supply is disconnected after the fault of the misreporting relay sticking.

[0003] This method can achieve the control needs of passive discharge after the relay is turned off, but the battery voltage is directly loaded on the discharge resistor, and the discharge resistor works continuously at full voltage when the relay is closed, which increases the standby power consumption and the power consumption during operation; due to the large power consumption, more discharge resistors with larger packaging are needed, the layout space is large, and problems such as heating are also accompanied. SUMMARY

[0004] In order to overcome the defects of the prior art, a low-voltage system passive discharge circuit and a method for using the same are provided, which are compact in structure, low in power consumption, flexible in configuration, safe and reliable.

[0005] The present application achieves the purpose of the invention through the following technical solutions:

[0006] A low-voltage system passive discharge circuit, comprising a direct current power supply, characterized in that it further comprises an energy storage capacitor, a pull-up resistor, a pull-down resistor, a discharge resistor, a field effect transistor and a dynamic breaking contact,

[0007] One end of the energy storage capacitor, one end of the pull-up resistor and the drain of the field effect transistor are connected to each other and then connected to the positive electrode of the direct current power supply through a control bus in series with the dynamic breaking contact;

[0008] The other end of the energy storage capacitor is connected to the negative electrode of the direct current power supply;

[0009] The other end of the pull-up resistor is connected to the gate of the field effect transistor and one end of the pull-down resistor, respectively, and the source of the field effect transistor is connected to one end of the discharge resistor;

[0010] The other end of the pull-down resistor and the other end of the discharge resistor are both connected to the negative electrode of the direct current power supply.

[0011] The low-voltage system passive discharge circuit, characterized in that the field effect transistor is an N-channel enhancement mode insulated gate field effect transistor.

[0012] The use method of the low-voltage system passive discharge circuit is characterized in that the following steps are sequentially implemented:

[0013] ① closing: when the main circuit relay is closed, the movable breaking contact is closed at this time, due to the voltage division of the pull-up resistor and the pull-down resistor, the threshold voltage of the driving gate of the field effect transistor is reached, the drain of the field effect transistor starts to have current flow, and at the same time, due to the existence of the discharge resistor, as the current flowing through the drain of the field effect transistor increases, the voltage of the source of the field effect transistor continuously rises, the potential difference between the gate and the source of the field effect transistor continuously decreases, until the potential difference reaches the threshold voltage of the gate-source of the field effect transistor, at this time, the field effect transistor is not saturated and is turned on, and the voltage of the direct current power supply cannot be completely loaded on the discharge resistor;

[0014] ② opening: when the main circuit relay is opened, the movable breaking contact is opened at this time, due to the energy storage effect of the energy storage capacitor, the potential at the energy storage capacitor end of the control bus slowly decreases from the potential at the direct current power supply end of the control bus after the movable breaking contact is opened, the field effect transistor still works in the amplification zone for a period of time after the movable breaking contact is opened, due to the consumption of the discharge resistor, the potential at the energy storage capacitor end of the control bus continuously decreases, the discharge current of the energy storage capacitor also continuously decreases, until the potential at the energy storage capacitor end of the control bus is low enough to drive the field effect transistor to open, at this time, the passive discharge of the energy storage capacitor stops. During the entire passive discharge process, the duration of the passive discharge and the discharge current can be realized by adjusting the resistance values of the pull-up resistor, the pull-down resistor and the discharge resistor, and the safe potential for finally stopping the discharge can also be realized by adjusting the resistance values of the pull-up resistor and the pull-down resistor.

[0015] The application utilizes the working characteristics of the amplification zone of the field effect transistor, when the relay is closed to make the movable breaking contact closed, part of the voltage of the direct current power supply is distributed between the drain and the source of the field effect transistor, only part of the voltage is consumed on the discharge resistor, the standby power consumption during the system operation and the power loss during the running process are greatly reduced, the heat is reduced, and due to the reduction of the power consumption and the reduction of the number of low discharge resistors, the layout space can also be saved. The application can complete the function of passive discharge after power-off, and the discharge time can be flexibly configured according to different running scenes, and through appropriate parameter adjustment, the bus voltage can be lowered to a safe voltage range within a specified time after the controller is powered off, the fault of the vehicle relay sticking due to mis-triggering is prevented, and the design requirements of system power consumption, stability and safety are optimized.

[0016] The application has the following beneficial effects: compact structure, reduced power consumption, flexible configuration, safety and reliability. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 is the circuit principle diagram of the application. DETAILED DESCRIPTION

[0018] The application will be further explained by specific examples.

[0019] Example 1

[0020] A low-voltage system passive discharge circuit, comprising a direct current power supply 1, an energy storage capacitor 2, a pull-up resistor 31, a pull-down resistor 32, a discharge resistor 33, a field effect transistor 4 and a movable break contact 5, as shown in the figure, and the specific structure is as follows:

[0021] One end of the energy storage capacitor 2, one end of the pull-up resistor 31 and the drain of the field effect transistor 4 are connected to each other and then connected to the positive pole of the direct current power supply 1 through a control bus 6 in series with the movable break contact 5;

[0022] The other end of the energy storage capacitor 2 is connected to the negative pole of the direct current power supply 1;

[0023] The other end of the pull-up resistor 31 is connected to the gate of the field effect transistor 4 and one end of the pull-down resistor 32 respectively, and the source of the field effect transistor 4 is connected to one end of the discharge resistor 33;

[0024] The other end of the pull-down resistor 32 and the other end of the discharge resistor 33 are both connected to the negative pole of the direct current power supply 1.

[0025] In this embodiment, the field effect transistor 4 is an N-channel enhancement mode insulated gate field effect transistor.

[0026] Figure 1 In this embodiment, E is the direct current power supply 1, C is the energy storage capacitor 2, R1 is the pull-up resistor 31, R2 is the pull-down resistor 32, R3 is the discharge resistor 33, Q is the field effect transistor 4, G, D and S are the gate, drain and source of the field effect transistor 4 respectively, and K is the movable break contact 5.

[0027] When the embodiment is used, the following steps are implemented in sequence:

[0028] ① Closing: when the main circuit relay is closed, the movable break contact 5 is closed at this time, due to the voltage division effect of the pull-up resistor 31 and the pull-down resistor 32, the drive gate of the field effect transistor 4 reaches the threshold opening voltage, the drain of the field effect transistor 4 starts to have current flow, and at the same time, due to the existence of the discharge resistor 33, as the current flowing through the drain of the field effect transistor 4 increases, the source voltage of the field effect transistor 4 continuously rises, the potential difference between the gate and the source of the field effect transistor 4 continuously decreases, until the potential difference reaches the gate-source opening threshold voltage of the field effect transistor 4, and the voltage of the direct current power supply 1 cannot be completely loaded on the discharge resistor 33;

[0029] ② Disconnection: When the main circuit relay is disconnected, the break contact 5 is disconnected. Due to the energy storage effect of the energy storage capacitor 2, the potential at the energy storage capacitor end of the control bus 6 will slowly decrease from the potential at the DC power supply end of the control bus 6 after the break contact 5 is disconnected. The field effect transistor 4 will continue to operate in the amplification region for a period of time after the break contact 5 is disconnected. Due to the consumption of the discharge resistor 33, the potential at the energy storage capacitor end of the control bus 6 continues to decrease, and the discharge current of the energy storage capacitor 2 also continuously decreases until the potential at the energy storage capacitor end of the control bus 6 is low enough to drive the field effect transistor 4 to turn on. At this time, the passive discharge of the energy storage capacitor 2 stops. During the entire passive discharge process, the duration of the passive discharge and the discharge current can be adjusted by adjusting the resistance values ​​of the pull-up resistor 31, the pull-down resistor 32, and the discharge resistor 33. The safe potential at which the discharge is finally stopped can also be adjusted by adjusting the resistance values ​​of the pull-up resistor 31 and the pull-down resistor 32.

[0030] In this embodiment, the gate-source turn-on threshold voltage of the field effect tube 4 is 4V, the electromotive force of the DC power supply 1 is 12V, the resistance values ​​of the pull-up resistor 31 and the pull-down resistor 32 are equal, and the resistance value of the discharge resistor 33 is 500Ω, then the discharge current I= =0.004A=4mA. If you need to reduce the discharge time, just reduce the resistance of the discharge resistor 33. If the resistance of the discharge resistor 33 is reduced to 100Ω, the discharge current I= =0.02A=20mA. Since the amount of electricity released is the same, an increase in the discharge current will shorten the discharge time. The final stop voltage can be achieved by selecting field effect transistors 4 with different threshold voltages, or by adjusting the resistance ratio of the pull-up resistor 31 and the pull-down resistor 32. In this embodiment, when the voltage of the energy storage capacitor 2 drops to about 8V, the divided driving voltage is exactly 4V, which can no longer drive the field effect transistor 4 to flow current, and the discharge stops.

Claims

1. A method for using a low-voltage system passive discharge circuit, the low-voltage system passive discharge circuit comprising a DC power supply (1), an energy storage capacitor (2), a pull-up resistor (31), a pull-down resistor (32), a discharge resistor (33), a field effect transistor (4), and a break contact (5). The three nodes, one end of the energy storage capacitor (2), one end of the pull-up resistor (31) and the drain of the field effect transistor (4), are connected to each other and then connected to the positive electrode of the DC power supply (1) through a control bus (6) connected in series with a break contact (5); The other end of the energy storage capacitor (2) is connected to the negative electrode of the DC power supply (1); The other end of the pull-up resistor (31) is connected to the gate of the field effect transistor (4) and one end of the pull-down resistor (32), respectively, and the source of the field effect transistor (4) is connected to one end of the discharge resistor (33); The other end of the pull-down resistor (32) and the other end of the discharge resistor (33) are both connected to the negative electrode of the DC power supply (1); The field effect transistor (4) is an N-channel enhanced insulated gate field effect transistor; Its characteristics are: Follow the steps below: ① Closed: When the main circuit relay is closed, the break contact (5) is closed. Due to the voltage-dividing effect of the pull-up resistor (31) and the pull-down resistor (32), the field effect tube (4) drives the gate to reach the threshold turn-on voltage. Current begins to flow through the drain of the field effect tube (4). At the same time, due to the existence of the discharge resistor (33), as the current flowing through the drain of the field effect tube (4) increases, the source voltage of the field effect tube (4) continues to rise, and the potential difference between the gate and source of the field effect tube (4) continues to decrease until the potential difference reaches the gate-source turn-on threshold voltage of the field effect tube (4). At this time, the field effect tube (4) is not saturated and the voltage of the DC power supply (1) cannot be fully loaded on the discharge resistor (33); ② Disconnection: When the main circuit relay is disconnected, the break contact (5) is disconnected. Due to the energy storage effect of the energy storage capacitor (2), the potential of the energy storage capacitor end of the control bus (6) will slowly decrease from the potential of the DC power supply end of the control bus (6) after the break contact (5) is disconnected. The field effect tube (4) will still work in the amplification area for a period of time after the break contact (5) is disconnected. Due to the consumption of the discharge resistor (33), the potential of the energy storage capacitor end of the control bus (6) continues to decrease, and the discharge current of the energy storage capacitor (2) also continues to decrease until the potential of the energy storage capacitor end of the control bus (6) is low enough to drive the field effect tube (4) to turn on. At this time, the passive discharge of the energy storage capacitor (2) stops.

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