CN212677138U

CN212677138U - Field-effect tube electronic switch circuit with load cold short circuit protection function

Info

Publication number: CN212677138U
Application number: CN202021241078.XU
Authority: CN
Inventors: 陈维忠; 许中荣
Original assignee: Nanjing Changya Track Traffic Technology Co ltd
Current assignee: Nanjing Changya Track Traffic Technology Co ltd
Priority date: 2020-06-30
Filing date: 2020-06-30
Publication date: 2021-03-09
Anticipated expiration: 2030-06-30

Abstract

The utility model discloses a field effect transistor electronic switch circuit with load cold short-circuit protection function, including drive chip U1, overcurrent value sets for potentiometre W1, divider resistance R1, input resistance R3, field effect transistor Q1 and grid resistance R2, grid discharge diode D1, discharge resistance R4 and protection stabilivolt Z1, current sampling resistance R6, sample filter resistance R5 and sample filter capacitance C2, output protection piezoresistance RV1, output freewheeling diode D3, output filter capacitance C3, output voltage keeps apart diode D2, current limiting resistance R7, current limiting resistance R8, prevent reverse diode D4 and output voltage sample opto-coupler U2; the utility model adopts the voltage sampling method for overcurrent protection, and the circuit realizes the protection of overcurrent, thermal short circuit and cold short circuit by collecting the load voltage; the circuit has the advantages of simple circuit, low cost, wide protection range, reliable action and the like.

Description

Field-effect tube electronic switch circuit with load cold short circuit protection function

Technical Field

The utility model relates to a head lamp, tail lamp, electric loudspeaker, DC motor of city rail vehicle and the application circuit of the power supply program controlled switch of other power consumption loads of tail car especially relate to a field effect transistor electronic switch circuit with load cold short-circuit protection function, belong to passenger train electrical product and make technical field.

Background

At present, the urban rail vehicle is rapidly developed, the automation degree of the urban rail vehicle is higher and higher, and unmanned driving becomes a future development trend; from the aspect of design and manufacture of functional parts of a vehicle, intellectualization is also required, such as automatic closing after tripping of a switch protection, protection and automatic restarting after a load short circuit, and the like; particularly, various contactless electronic switches can be reliably protected during overcurrent, can be automatically restarted under the control of a vehicle control unit, and cannot be permanently damaged due to faults such as local short circuit and the like; due to the particularity of the railway industry, the direct current power supply of the vehicle is provided with DC600V, DC110V, DC48V and DC24V, and four voltages coexist on one vehicle; at present, most finished electronic switches with perfect protection are designed for automobiles, the working voltage is usually not higher than DC24V, the electronic switch of DC110V has no ready-made available integrated circuit, the electronic switch above DC48V is mainly designed by using a MOSFET field effect transistor, common electronic switches are all designed with overcurrent protection, otherwise, the use requirements cannot be met, and the electronic switches are slightly abnormal and are immediately broken down and damaged; however, most of the over-current protection is thermal short-circuit protection, that is, the electronic switch is already turned on, the switch is normally powered on to work, a load short circuit occurs in the process, and a common current sampling method can be used for performing the protection.

Disclosure of Invention

In order to solve the deficiency of the prior art, the utility model provides a field effect transistor electronic switch circuit with load cold short circuit protection function, which is a simple and reliable MOSFET field effect transistor electronic switch circuit with load cold short circuit, hot short circuit and load overcurrent protection function, and adopts the voltage sampling method for overcurrent protection, and the circuit realizes the protection of overcurrent, hot short circuit and cold short circuit by collecting the load voltage; the circuit does not need a special chip, does not need debugging in use, and has the advantages of simple circuit, low cost, wide protection range, reliable action and the like; the urban rail vehicle has simple circuit composition and excellent protection performance, and can well meet the requirements of the urban rail vehicle under the working conditions of manned driving and unmanned driving.

The utility model discloses the technical scheme who adopts does:

the field effect transistor electronic switch circuit with the load cold short circuit protection function comprises a driving chip U1, an overcurrent value setting potentiometer W1, a voltage dividing resistor R1, an input resistor R3, a field effect transistor Q1 and a grid resistor R2 thereof, a grid discharge diode D1, a discharge resistor R4, a protection voltage stabilizing tube Z1, a current sampling resistor R6, a sampling filter resistor R5, a sampling filter capacitor C2, an output protection voltage dependent resistor RV1, an output freewheeling diode D3, an output filter capacitor C3, an output voltage isolation diode D2, a current limiting resistor R7, a current limiting resistor R8, an anti-reverse diode D4 and an output voltage sampling optocoupler U2;

one end of the input resistor R3 is connected with an externally input pulse signal, the other end of the input resistor R3 is connected with 3 input pins of a driving chip U1, a voltage dividing resistor R1 is connected with an overcurrent value setting potentiometer W1 in series and outputs a voltage-variable overcurrent protection reference voltage to 1 pin of the driving chip U1, 8 pins and 5 pins of the driving chip U1 are respectively used for supplying positive and negative terminals for a power supply VCC of the driving chip U1, a driving terminal 6 pin and a discharging terminal 7 pin of the driving chip U1 are connected in parallel and then connected with one end of a gate resistor R2, the other end of the gate resistor R2 is connected with the gate of a field effect tube Q1, and a gate discharging diode D1 is connected with the gate resistor R2 in parallel; a discharge resistor R4 and a protection voltage regulator tube Z1 are connected in parallel between the grid of the field effect tube Q1 and the source electrode of the field effect tube Q1; the drain electrode of the field effect transistor Q1 is connected with the anode IN + of the power input end, the source electrode of the field effect transistor Q1 is connected with one end of a current sampling resistor R6, the other end of the current sampling resistor R6 is connected with the anode OUT + of the switch output end, a sampling filter resistor R5 and a sampling filter capacitor C2 are connected IN series and then connected IN parallel with the two ends of a current sampling resistor R6, and the source electrode of the field effect transistor Q1 is also connected with the 2 pin of a driving chip U1 through the sampling filter resistor R5; a protection voltage dependent resistor RV1, an output freewheeling diode D3 and an output filter capacitor C3 are connected in parallel between the positive pole OUT + of the switch output end and the negative pole OUT < - >; the anode of the output voltage isolation diode D2 is connected with the anode OUT + of the output end of the switch, the cathode of the output voltage isolation diode D2 is connected with the pin 1 of the output voltage sampling optocoupler U2, the pin 2 of the output voltage sampling optocoupler U2 is connected with the cathode OUT-of the output end of the switch through the current limiting resistor R7, and the anti-reverse diode D4 is reversely connected in parallel between the pin 1 and the pin 2 of the output voltage sampling optocoupler U2; the 3-pin of the output voltage sampling optocoupler U2 is connected with one end of a current limiting resistor R8, the other end of the current limiting resistor R8 is connected with the 3-pin of the driving chip U1, and the 4-pin of the output voltage sampling optocoupler U2 is connected with a power supply VCC.

As a further preferred aspect of the present invention, a filter capacitor C1 for supplying power to the filter and decoupling the high frequency to the driver chip U1 is connected between the power VCC and the ground GND.

The beneficial effects of the utility model reside in that: the circuit is simple and reliable, all components used in the whole circuit are general components, special or special components are not needed, and the circuit has the advantages of low cost and high reliability; overcurrent protection is realized by adopting a voltage sampling method, and overcurrent, thermal short circuit and cold short circuit are protected by the circuit by collecting load voltage; the circuit does not need a special chip, does not need debugging in use, and has the advantages of simple circuit, low cost, wide protection range, reliable action and the like; the urban rail vehicle has simple circuit composition and excellent protection performance, and can well meet the requirements of the urban rail vehicle under the working conditions of manned driving and unmanned driving.

Drawings

Fig. 1 is a circuit diagram of the present invention.

Detailed Description

The present invention will be described in detail with reference to the accompanying drawings and examples.

As shown in fig. 1: the embodiment is a field effect transistor electronic switch circuit with load cold short circuit protection function, which comprises a driving chip U1, an overcurrent value setting potentiometer W1, a voltage dividing resistor R1, an input resistor R3, a field effect transistor Q1 and a grid resistor R2 thereof, a grid discharge diode D1, a discharge resistor R4, a protection voltage stabilizing tube Z1, a current sampling resistor R6, a sampling filter resistor R5, a sampling filter capacitor C2, an output protection voltage dependent resistor RV1, an output freewheeling diode D3, an output filter capacitor C3, an output voltage isolation diode D2, a current limiting resistor R7, a current limiting resistor R8, an anti-reverse diode D4 and an output voltage sampling optocoupler U2;

In this embodiment, a filter capacitor C1 for supplying power, filtering and decoupling high frequency for the driver chip U1 is connected between the power VCC and the ground GND.

The circuit principle of the embodiment is as follows:

here, it is assumed that: the external start high level pulse width is 20 uS; when an externally input pulse signal is a starting pulse high level '1', 6 pins of a driving chip U1 output driving voltage, a driving field effect tube Q1 is opened, a switch is switched on, a load R9 is electrified to work, the voltage between the positive electrode OUT + of the output end of the switch and the negative electrode OUT-of the output end of the switch is input voltage DC110V, the output voltage of the DC110V drives an output voltage sampling optocoupler U2 to be switched on through an output voltage isolation diode D2 and a current-limiting resistor R7, and the voltage of a 4 pin power VCC of the output voltage sampling optocoupler U2 is applied to the input 3 pins of the driving chip U1 through the output 3 pins and 4 pins of the output voltage sampling optocoupler U2 and the current-limiting resistor R8; when the load R9 is just powered on, if the load R9 is short-circuited, a cold short circuit occurs, and because the voltage between the positive pole OUT + of the switch output end and the negative pole OUT-of the switch output end cannot be established, the high level disappears after the input starting pulse high level '1' continues for 20uS at the moment, the input end becomes a high-resistance state, the output voltage sampling optocoupler U2 cannot be switched on to maintain the high level on the input 3 pin of the driving chip U1, and the circuit cannot be started, so that the switching circuit keeps a turn-off state.

When the externally input pulse signal is a starting pulse high level '1', a pin 3 of the driving chip U1 is a high level '1', a pin 6 of the driving chip U1 outputs driving voltage, the field effect transistor Q1 is driven to be turned on, the switch is switched on, and the load R9 is electrified to work; at the moment, the voltage between the positive pole OUT + of the switch output end and the negative pole OUT-of the switch output end is input voltage DC110V, the output voltage of the DC110V drives an output voltage sampling optocoupler U2 to be conducted through an output voltage isolation diode D2 and a current-limiting resistor R7, and the voltage of a 4-pin power supply VCC of the output voltage sampling optocoupler U2 is applied to an input 3 pin of a driving chip U1 through an output end 3 pin and a 4 pin of the output voltage sampling optocoupler U2 and the current-limiting resistor R8; at this time, if the load R9 has no short circuit, the output voltage continuously makes the output voltage sampling optocoupler U2 conduct, the output end pin 3 and pin 4 of the output voltage sampling optocoupler U2 and the current limiting resistor R8 continuously provide the high level "1" for the pin 3 of the driving chip U1, at this time, the start pulse has been changed into the high impedance state by the high level "1", but because the output end pin 3 and pin 4 of the output voltage sampling optocoupler U2 and the high level applied to the input pin 3 of the driving chip U1 by the current limiting resistor R8 are continuously maintained, so the switching circuit enters the normal continuous working state.

Under normal operating condition, when load R9 appears transient short circuit, DC110V at the output end of the switch circuit disappears instantaneously, voltage between pin 1 and pin 2 of output voltage sampling optocoupler U2 becomes 0V, output voltage sampling optocoupler U2 is cut off, pin 3 and pin 4 at the output end of output voltage sampling optocoupler U2 are disconnected, pin 3 of driving chip U1 loses high level, because of input signal is high-impedance state, under the effect of pull-down resistor in pin 3 of driving chip U1, pin 3 of driving chip U1 becomes low level "0", pin 6 of driving chip U1 also becomes low level "0", field effect transistor Q1 is turned off, and the switch circuit will be maintained under the continuous turn-off state.

The circuit of the embodiment adopts a pulse starting and pulse stopping working mode, and when the INPUT end INPUT is a high-level starting pulse '1', the circuit is started; when the INPUT end INPUT is in an artery starting high resistance state, the circuit is in a normal working state or a normal stop state; when the INPUT end INPUT is at low level and stops pulse '0', the circuit stops; when the circuit normally works, the voltage between the positive pole OUT + of the switch output end and the negative pole OUT-of the switch output end locks the input 3 pins of the drive chip U1 through the output voltage sampling optocoupler U2, when the voltage between the positive pole OUT + of the switch output end and the negative pole OUT-of the switch output end disappears or is greatly reduced due to the short circuit of the load R9, the locking function of the output voltage sampling optocoupler U2 on the input 3 pins of the drive chip U1 fails, the circuit stops outputting, and the circuit is protected; the overcurrent protection action threshold value of the circuit is continuously adjustable through the overcurrent value setting potentiometer W1, and the overcurrent protection action threshold value can be set arbitrarily; the driver chip U1 is EG3002 with conventional overcurrent protection.

The cold-state short-circuit protection and the hot-state short-circuit protection of the electronic switch load are realized by adopting the principle of pulse starting and output voltage feedback locking input; the driving chip U1 is a universal chip with a protection turn-off function, and in the implementation process, a single-path low-side driving chip of any manufacturer and model can be competent without harsh requirements as long as the single-path low-side driving chip has the turn-off protection function; the circuit of the utility model can work in a very wide voltage range without special adjustment, and the voltage which the circuit can bear is directly related to the withstand voltage of the field effect transistor Q1; the output voltage feedback locking circuit adopts optical coupling locking, but other forms of output voltage feedback locking circuits can be adopted, and the short-circuit protection principles of the circuits are consistent.

The implementation circuit is simple and reliable, all components used in the whole circuit are general components, special or special components are not needed, and the implementation circuit has the advantages of low cost and high reliability; overcurrent protection is realized by adopting a voltage sampling method, and overcurrent, thermal short circuit and cold short circuit are protected by the circuit by collecting load voltage; the circuit does not need a special chip, does not need debugging in use, and has the advantages of simple circuit, low cost, wide protection range, reliable action and the like; the urban rail vehicle has simple circuit composition and excellent protection performance, and can well meet the requirements of the urban rail vehicle under the working conditions of manned driving and unmanned driving.

The above description is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, a plurality of improvements and decorations can be made without departing from the principle of the present invention, and these improvements and decorations should also be regarded as the protection scope of the present invention.

Claims

1. The field effect transistor electronic switch circuit with the load cold short circuit protection function is characterized in that: the driving circuit comprises a driving chip U1, an overcurrent value setting potentiometer W1, a voltage division resistor R1, an input resistor R3, a field effect transistor Q1, a grid resistor R2 of the field effect transistor Q1, a grid discharge diode D1, a discharge resistor R4, a protection voltage regulator tube Z1, a current sampling resistor R6, a sampling filter resistor R5, a sampling filter capacitor C2, an output protection voltage dependent resistor RV1, an output freewheeling diode D3, an output filter capacitor C3, an output voltage isolation diode D2, a current limiting resistor R7, a current limiting resistor R8, an anti-reverse diode D4 and an output voltage sampling optocoupler U2;

2. The FET electronic switch circuit with load cold short-circuit protection function according to claim 1, wherein a filter capacitor C1 for filtering power supply and high frequency decoupling of the driver IC U1 is connected between the power supply VCC and ground GND.