CN112564468A - Passive discharge circuit of low-voltage system and use method thereof - Google Patents
Passive discharge circuit of low-voltage system and use method thereof Download PDFInfo
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- CN112564468A CN112564468A CN202011571022.5A CN202011571022A CN112564468A CN 112564468 A CN112564468 A CN 112564468A CN 202011571022 A CN202011571022 A CN 202011571022A CN 112564468 A CN112564468 A CN 112564468A
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- field effect
- resistor
- energy storage
- pull
- storage capacitor
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M1/00—Details of apparatus for conversion
- H02M1/32—Means for protecting converters other than automatic disconnection
Abstract
The invention relates to the field of devices for protecting converters, in particular to a low-voltage system passive discharge circuit and a using method thereof. A low-voltage system passive discharge circuit comprises a direct current power supply (1), and is characterized in that: the energy storage capacitor (2), the pull-up resistor (31), the pull-down resistor (32), the discharge resistor (33), the field effect transistor (4) and the break contact (5) are further included, and three nodes, namely one end of the energy storage capacitor (2), one end of the pull-up resistor (31) and the drain electrode of the field effect transistor (4), are connected with the positive electrode of the direct-current power supply (1) through a control bus (6) which is connected with the break contact (5) in series; the other end of the energy storage capacitor (2) is connected with the negative electrode of the direct current power supply (1). A use method of a low-voltage system passive discharge circuit is characterized by comprising the following steps: the method is implemented in sequence according to the following steps: closing; and (9) disconnecting. The invention has compact structure, reduced power consumption, flexible configuration, safety and reliability.
Description
Technical Field
The invention relates to the field of devices for protecting converters, in particular to a low-voltage system passive discharge circuit and a using method thereof.
Background
At present, a passive discharge circuit of a low-voltage system mainly releases energy by connecting a plurality of discharge resistors in parallel. When the main circuit is powered on, all power supply sources are loaded on the discharge resistor, and the discharge resistor continuously runs with high power consumption; when the main circuit switch is disconnected, the energy of the DC-Link energy storage capacitor is released through the discharge resistor, the voltage of the bus on the side of the controller is rapidly reduced, and the fault that the relay is adhered is misinformed after the power supply is disconnected.
The method can realize the control requirement of passive discharge after the relay is disconnected, but the battery voltage is directly loaded on the discharge resistor, and when the relay is closed, the full voltage of the discharge resistor continuously works, so that the standby power consumption and the power consumption in the running process are increased; the larger power consumption requires larger package and more discharge resistors, so that the layout space is larger, and the problems of heat generation and the like are also caused.
Disclosure of Invention
In order to overcome the defects of the prior art and provide a passive discharge circuit with compact structure, reduced power consumption, flexible configuration, safety and reliability, the invention discloses a low-voltage system passive discharge circuit and a use method thereof.
The invention achieves the purpose by the following technical scheme:
a low-voltage system passive discharge circuit comprises a direct-current power supply and is characterized in that: also comprises an energy storage capacitor, a pull-up resistor, a pull-down resistor, a discharge resistor, a field effect transistor and a break contact,
one end of the energy storage capacitor, one end of the pull-up resistor and the drain electrode of the field effect transistor are connected with each other and then connected with the anode of the direct current power supply through a control bus in series connection with the break contact;
the other end of the energy storage capacitor is connected with the negative electrode of the direct current power supply;
the other end of the pull-up resistor is respectively connected with the grid of the field effect transistor and one end of the pull-down resistor, and the source electrode of the field effect transistor is connected with one end of the discharge resistor;
the other end of the pull-down resistor and the other end of the discharge resistor are both connected with the negative electrode of the direct current power supply.
The low-voltage system passive discharge circuit is characterized in that: the field effect transistor is an N-channel enhanced insulated gate field effect transistor.
The use method of the low-voltage system passive discharge circuit is characterized in that: the method is implemented in sequence according to the following steps:
closing: when the main circuit relay is closed, the break contact is closed at the moment, the field effect tube drives the grid electrode to reach threshold opening voltage due to the partial pressure action of the pull-up resistor and the pull-down resistor, current starts to flow through the drain electrode of the field effect tube, meanwhile, due to the existence of the discharge resistor, the source electrode voltage of the field effect tube is continuously raised along with the increase of the drain electrode current of the field effect tube, the potential difference between the grid electrode and the source electrode of the field effect tube is continuously reduced until the potential difference reaches the grid source opening threshold voltage of the field effect tube, the field effect tube is in unsaturated conduction at the moment, and the voltage of the direct current power supply cannot;
cutting off: when the main circuit relay is disconnected, the dynamic breaking contact is disconnected, due to the energy storage effect of the energy storage capacitor, the potential of the energy storage capacitor end of the control bus slowly drops from the potential of the direct current power source end of the control bus after the dynamic breaking contact is disconnected, the field effect transistor still works in an amplification area within a period of time after the dynamic breaking contact is disconnected, due to the consumption of the discharge resistor, the potential of the energy storage capacitor end of the control bus continuously drops, the discharge current of the energy storage capacitor continuously decreases until the potential of the energy storage capacitor end of the control bus is low enough not to drive the field effect transistor to be opened, and at the moment, the passive discharge of the energy storage capacitor stops. In the whole 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.
According to the invention, by utilizing the working characteristics of the field effect transistor amplification area, when the relay is closed to close the dynamic breaking contact, partial voltage of the direct current power supply is distributed between the drain electrode and the source electrode of the field effect transistor, and only partial voltage is consumed on the discharging resistor, so that the standby power consumption and the power loss in the operation process when the system works are greatly reduced, the heating is reduced, and the layout space can be saved due to the reduction of the power consumption and the reduction of the number of the discharging resistors. The invention can complete the function requirement of passive discharge after power failure, can flexibly configure the discharge time aiming at different operation scenes, can meet the requirement that the bus voltage is reduced to a safe voltage range within the specified time after the power failure of the controller through proper parameter adjustment, prevents the fault of mistakenly triggering the adhesion of the relay of the whole vehicle, and optimizes the design requirements of system power consumption and stable safety.
The invention has the following beneficial effects: compact structure, reduced power consumption, flexible configuration, safety and reliability.
Drawings
Fig. 1 is a circuit schematic of the present invention.
Detailed Description
The invention is further illustrated by the following specific examples.
Example 1
A low-voltage system passive discharge circuit comprises 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 dynamic break contact 5, and the specific structure is as shown in the figure:
one end of the energy storage capacitor 2, one end of the pull-up resistor 31 and the drain electrode of the field effect tube 4 are connected with each other and then connected with the anode of the direct current power supply 1 through a control bus 6 which is connected with the dynamic break contact 5 in series;
the other end of the energy storage capacitor 2 is connected with the negative electrode of the direct current power supply 1;
the other end of the pull-up resistor 31 is respectively connected with the grid of the field effect transistor 4 and one end of the pull-down resistor 32, and the source of the field effect transistor 4 is connected with 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.
In this embodiment: the field effect transistor 4 is an N-channel enhanced insulated gate field effect transistor.
In fig. 1: e is a DC power supply 1, C is an energy storage capacitor 2, R1Is a pull-up resistor 31, R2Is a pull-down resistor 32, R3Is the discharge resistor 33, Q is the fet 4, G, D and S are the gate, drain and source, respectively, of the fet 4, and K is the trip contact 5.
When the method is used, the steps are implemented in sequence as follows:
closing: when the main circuit relay is closed, the break contact 5 is closed, due to the voltage division effect of the pull-up resistor 31 and the pull-down resistor 32, the field effect tube 4 drives the grid to reach threshold opening voltage, current starts to flow through the drain of the field effect tube 4, meanwhile, due to the existence of the discharge resistor 33, along with the increase of the current flowing through the drain of the field effect tube 4, the source voltage of the field effect tube 4 is continuously raised, the potential difference between the grid and the source of the field effect tube 4 is continuously reduced until the potential difference reaches the grid source opening threshold voltage of the field effect tube 4, and the voltage of the direct current power supply 1 cannot be completely loaded on the discharge resistor 33;
cutting off: when the main circuit relay is disconnected, the dynamic breaking contact 5 is disconnected at the moment, 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 is slowly reduced from the potential of the direct-current power supply end of the control bus 6 after the dynamic breaking contact 5 is disconnected, the field effect transistor 4 still works in an amplification area within a period of time after the dynamic breaking 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 is continuously reduced, the discharge current of the energy storage capacitor 2 is continuously reduced until the potential of the energy storage capacitor end of the control bus 6 is low enough not to drive the field effect transistor 4 to be opened, and at the moment, the passive discharge of the energy. In the whole 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 31, the pull-down resistor 32 and the discharge resistor 33, and the safety potential for finally stopping the discharge can also be realized by adjusting the resistance values of the pull-up resistor 31 and the pull-down resistor 32.
In this embodiment: if the gate-source turn-on threshold voltage of the fet 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 to each other, and the resistance value of the discharge resistor 33 is 500 Ω, then the discharge current I =isobtained
=0.004A =4 mA. If the discharge time needs to be reduced, the resistance of the discharge resistor 33 can be reduced, and if the resistance of the discharge resistor 33 is reduced to 100 Ω, the discharge current I =isobtained
=0.02A =20mA, an increase in discharge current will shorten the discharge time since the amount of power dissipated is the same; finally stop the electricityThe voltage can be realized by selecting the field effect transistor 4 with different threshold voltages, or by adjusting the ratio of the resistance values of the pull-up resistor 31 and the pull-down resistor 32, in this embodiment, when the voltage of the energy storage capacitor 2 is reduced to about 8V, the divided driving voltage is just 4V, and the field effect transistor 4 cannot be driven to flow through the current any more, and the discharge is stopped.
Claims (3)
1. A low-voltage system passive discharge circuit comprises a direct current power supply (1), and is characterized in that: also comprises an energy storage capacitor (2), a pull-up resistor (31), a pull-down resistor (32), a discharge resistor (33), a field effect tube (4) and a break contact (5),
one end of the energy storage capacitor (2), one end of the pull-up resistor (31) and the drain electrode of the field effect transistor (4) are connected with each other and then connected with the anode of the direct current power supply (1) through a control bus (6) which is connected with the dynamic break contact (5) in series;
the other end of the energy storage capacitor (2) is connected with the negative electrode of the direct current power supply (1);
the other end of the pull-up resistor (31) is respectively connected with the grid of the field effect transistor (4) and one end of the pull-down resistor (32), and the source of the field effect transistor (4) is connected with 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 with the negative electrode of the direct current power supply (1).
2. The low voltage system passive discharge circuit of claim 1, further comprising: the field effect tube (4) is an N-channel enhanced insulated gate field effect tube.
3. The use method of the low-voltage system passive discharge circuit as claimed in claim 1 or 2, characterized in that: the method is implemented in sequence according to the following steps:
closing: when a main circuit relay is closed, the break contact (5) is closed, due to the voltage division effect of the pull-up resistor (31) and the pull-down resistor (32), the field effect tube (4) drives the grid to reach threshold opening voltage, current starts to flow through the drain of the field effect tube (4), simultaneously, due to the existence of the discharge resistor (33), along with the increase of the current flowing through the drain of the field effect tube (4), the source voltage of the field effect tube (4) is raised continuously, the potential difference between the grid and the source of the field effect tube (4) is reduced continuously until the potential difference reaches the grid source opening threshold voltage of the field effect tube (4), at the moment, the field effect tube (4) is conducted in an unsaturated mode, and the voltage of the direct current power supply (1) cannot be completely loaded on the discharge resistor (33);
cutting off: when the main circuit relay is disconnected, the dynamic breaking contact (5) is disconnected at the moment, 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) is slowly reduced from the potential of the direct-current power supply end of the control bus (6) after the dynamic breaking contact (5) is disconnected, the field effect transistor (4) still works in an amplification area within a period of time after the dynamic breaking 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) is continuously reduced, the discharge current of the energy storage capacitor (2) is continuously reduced until the potential of the energy storage capacitor end of the control bus (6) is low enough to drive the field effect transistor (4) to be started, and at the moment, the passive discharge of the energy storage capacitor (2.
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| Application Number | Priority Date | Filing Date | Title |
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| CN202011571022.5A CN112564468A (en) | 2020-12-27 | 2020-12-27 | Passive discharge circuit of low-voltage system and use method thereof |
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| CN202011571022.5A CN112564468A (en) | 2020-12-27 | 2020-12-27 | Passive discharge circuit of low-voltage system and use method thereof |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113824300A (en) * | 2021-09-18 | 2021-12-21 | 珠海格力电器股份有限公司 | Discharge circuit for blocking bus capacitor and electrical equipment |
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2020
- 2020-12-27 CN CN202011571022.5A patent/CN112564468A/en active Pending
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113824300A (en) * | 2021-09-18 | 2021-12-21 | 珠海格力电器股份有限公司 | Discharge circuit for blocking bus capacitor and electrical equipment |
| CN113824300B (en) * | 2021-09-18 | 2023-07-18 | 珠海格力电器股份有限公司 | Discharging circuit for blocking bus capacitor and electrical equipment |
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