CN212695971U

CN212695971U - Short-circuit protection module with current-limiting function

Info

Publication number: CN212695971U
Application number: CN202021942787.0U
Authority: CN
Inventors: 杭华; 胡和平
Original assignee: Beijing Zhongke Zhichuang Electric Appliance Co ltd Shanghai Qingpu Branch
Current assignee: Beijing Zhongke Zhichuang Electric Appliance Co ltd Shanghai Qingpu Branch
Priority date: 2020-09-08
Filing date: 2020-09-08
Publication date: 2021-03-12
Anticipated expiration: 2030-09-08

Abstract

The utility model discloses a short-circuit protection module with current-limiting function, which comprises a switch driving unit, a control unit and at least two switch units; each of the switching units is connected in parallel between a voltage input terminal and a voltage output terminal. The first bias resistor, the sampling resistor and the current-limiting triode in each switch unit form a current source, and the current source is matched with the pull-down resistor to form a negative feedback suppression circuit for the switch transistor, so that the maximum current flowing through the switch transistor is limited. When the switch module is in a current limiting state, the control unit closes the switch unit by closing the switch driving unit, so that the switch transistor in the switch unit is prevented from being burnt due to long-term overcurrent, and the switch driving unit is tried to be started after preset time, so that power supply is automatically recovered after factors causing short circuit are eliminated.

Description

Short-circuit protection module with current-limiting function

Technical Field

The utility model relates to the field of electronic technology, concretely relates to short-circuit protection module with current limiting function.

Background

In emergency lighting equipment, a mode of combining a direct current power supply and an alternating current commercial power supply is required to supply power to a load. In the two power supply methods, alternating current commercial power is used as a main power supply, and when the alternating current commercial power fails, the power supply method is switched to a direct current power supply using a battery as an energy source, so that a switch module is required to be arranged between the direct current power supply and a load to control the on and off of the direct current power supply and the load.

The existing switch module is usually realized by adopting MOS transistors, the maximum current between the source and the drain of a single MOS transistor is usually small, and in the prior art, a plurality of MOS transistors are usually connected in parallel to deal with the large current. The problem that this kind of mode exists is that the MOS pipe that connects in parallel does not have the ability of flow equalizing, if the electric current imbalance of each MOS pipe can lead to the MOS pipe that the electric current is bigger to overheat and burn out.

In addition, the switch module in the prior art does not have the current-limiting capability, and when the load is short-circuited, the switch tube can flow a great current, so that the switch tube is burnt in a short time.

SUMMERY OF THE UTILITY MODEL

The utility model aims at providing a short-circuit protection module with current-limiting function according to the weak point of above-mentioned prior art, each MOS pipe has the current-limiting circuit that flow equalizes that corresponds in this module, has solved the uneven and short-circuit protection's that lacks of electric current that MOS pipe parallel circuit exists among the prior art problem.

The utility model discloses the purpose is realized accomplishing by following technical scheme:

a short-circuit protection module with a current-limiting function comprises a switch driving unit, a control unit and at least two switch units; each switch unit is connected in parallel between a voltage input end and a voltage output end;

the switch unit comprises a switch transistor, a voltage stabilizing diode and a current limiting triode; the drain electrode of the switching transistor is connected with the voltage output end, and the voltage stabilizing diode is connected between the source electrode and the grid electrode of the switching transistor; the emitting electrode of the current-limiting triode is connected with the voltage input end and is connected with the source electrode of the switching transistor through the sampling resistor; a first bias resistor is connected between the base electrode of the current-limiting triode and the source electrode of the switching transistor; two ends of the voltage stabilizing diode are connected with a second biasing resistor; the grid electrode of the switching transistor and the collector electrode of the current-limiting triode are both connected with the first end of the pull-down resistor;

the switch driving unit comprises a driving triode and a base electrode biasing circuit; the collector of the driving triode is connected with the second end of each pull-down resistor, the emitter of the driving triode is grounded, and the base of the driving triode is connected with the output end of the base bias circuit;

the control unit comprises a voltage sampling end and a control output end; the control output end is connected with the input end of the base electrode biasing circuit, and the voltage sampling end is connected with the voltage output end through a voltage division filter circuit; the control unit is configured to turn on the switching unit by driving the switching driving unit to be turned on, turn off the switching driving unit when the voltage of the voltage sampling terminal is lower than a threshold value, and attempt to turn on the switching driving unit after a predetermined time.

The utility model discloses a further improvement lies in: the base electrode biasing circuit comprises a first capacitor, an eighth resistor and a ninth resistor; the eighth resistor and the first capacitor are connected in parallel between the base electrode and the emitter electrode of the driving triode; one end of the ninth resistor is connected with the base electrode of the driving triode, and the other end of the ninth resistor is connected with the control output end.

The utility model discloses a further improvement lies in: the voltage division filter circuit comprises a sixth resistor, a tenth resistor and a second capacitor; the sixth resistor is connected between the voltage output end and the voltage sampling end; the tenth resistor and the second capacitor are connected in parallel between the voltage sampling terminal and the ground terminal.

The utility model discloses a further improvement lies in: in the switching unit, the sampling resistor has a resistance value of 45m Ω to 55m Ω, and the first bias resistor has a resistance value of 25 Ω to 35 Ω.

The utility model has the advantages that:

(1) the first bias resistor, the sampling resistor and the current-limiting triode in each switch unit form a current source, and the current source is matched with the pull-down resistor to form a negative feedback suppression circuit for the switch transistor, so that the maximum current flowing through the switch transistor is limited. When the switch module is in a current-limiting state, the control unit closes the switch unit by closing the switch driving unit, so that the switch transistor in the switch unit is prevented from being burnt down due to long-term overcurrent.

(2) Since each switching unit has a maximum current, the current of each switching unit is within a limit range, and the switching transistor in a single switching unit is prevented from exceeding the maximum current value.

(3) The control unit may automatically turn off the switch driving unit upon detection of the short-circuit fault and periodically attempt to start the switch driving unit so as to automatically restore power supply after the short-circuit fault is removed.

Drawings

Fig. 1 is a circuit diagram of a short-circuit protection module with a current limiting function.

Detailed Description

The features of the present invention and other related features are described in further detail below by way of example with reference to the accompanying drawings, for the understanding of those skilled in the art:

example (b): as shown in fig. 1, an embodiment of the present invention includes a short circuit protection module with a current limiting function, which includes a switch driving unit 10, a control unit IC1, and at least two switch units 20; the switching units 20 are connected in parallel between the voltage input terminal and the voltage output terminal. The switch driving unit 10 is used for driving each switch unit 20 to be conducted, each switch unit 20 has a current limiting function, and the maximum current of the switch unit is determined by internal element parameters; the control unit IC1 will continuously sense the voltage at the voltage output and will turn off the switch driving unit 10 when the voltage is too low (indicating that an overcurrent or short circuit occurs, resulting in too large a voltage drop across the switch module 20).

The circuit structures of the switch units 20 are the same, and thus the embodiment is described by taking one of them as an example. One switching unit 20 includes a switching transistor Q2, a zener diode ZD1, and a current limiting transistor Q1. The drain of the switching transistor Q2 is connected to the voltage output terminal, and the zener diode ZD1 is connected between the source and the gate of the switching transistor Q2, and its on voltage is 15V, which can play a role of voltage clamping. The emitter of the current-limiting transistor Q1 is connected to the voltage input and to the source of the switching transistor Q2 via the sampling resistor R2. A first bias resistor R1 is connected between the base of the current-limiting transistor Q1 and the source of the switching transistor Q2. A second bias resistor R3 is connected to both ends of the zener diode ZD 1. The gate of the switching transistor Q2 and the collector of the current limiting transistor Q1 are both connected to a first terminal of a pull-down resistor R7.

The switch driving unit 10 includes a driving transistor Q1 and a base bias circuit 11. The collector of the driving transistor Q1 is connected to the second terminal of each pull-down resistor (R7, R14), the emitter thereof is grounded, and the base thereof is connected to the output terminal of the base bias circuit 11.

When the switch driving unit 10 is turned on, the pull-down resistors (R7, R14) of the switch units 20 are grounded, so that the gate voltage of the switching transistor Q2 in the switch module is pulled low, and the source and the drain of the switching transistor Q2 are turned on. At this time, the current limiting transistor Q1, the sampling resistor R2, and the first bias resistor R1 in the switching unit 20 constitute a current source, and the magnitude of the output current thereof is positively correlated with the current flowing through the sampling resistor.

Normally, the current flowing through the sampling resistor R2 is small, so that the base current of the current-limiting transistor Q1 is very small. However, as the resistance value of the load connected to the voltage output terminal becomes smaller, the current flowing through each switching unit 20 increases, so that the voltage between the emitter and the base of the current-limiting transistor Q1 in the switching unit 20 increases, and further, the current flowing through the corresponding pull-down resistor R7 increases, so that the gate voltage of the switching transistor Q2 increases, thereby limiting the current of the switching transistor, and the switching unit 20 is in the current-limiting state. In the embodiment shown in fig. 1, the maximum current of each switching unit 20 is about 12A.

In this embodiment, the control unit IC1 includes a voltage sampling terminal and a control output terminal; the control output end is connected with the input end of the base electrode bias circuit 11, and the voltage sampling end is connected with the voltage output end through the voltage division filter circuit 30.

The control unit IC1 is configured to: each switching unit 20 is turned on by controlling the switching driving unit 10 to be turned on. When the voltage at the voltage sampling terminal is lower than the threshold value (when the voltage sampling terminal is short-circuited), the switch driving unit 10 is turned off, and the switch units are turned off. Finally the control unit IC1 turns on the switch drive unit 10 every 20 s. The trial process continues for 30s, during which the control unit IC1 detects the voltage at the voltage output terminal and, if the voltage is normal, controls the switch driving unit 10 to be continuously turned on so that each switch unit 20 is normally turned on to supply power; if the voltage is less than the threshold value, it indicates that the fault causing the short circuit still exists, the switch unit 20 is in the current limiting state, and the switch driving unit 10 is controlled to be turned off after 30ms, so as to avoid the switch transistor from being burnt out due to the long-term conduction of the switch unit 20.

In a specific embodiment, the control unit IC1 is implemented by an MCU, the voltage sampling terminal is connected to an ADC module or an interrupt pin inside the MCU, and the control output terminal is a GPIO of the MCU. When the control output terminal outputs a high level, the switch driving unit 10 is turned on.

In one embodiment, the base bias circuit 11 includes a first capacitor C1, an eighth resistor R8, and a ninth resistor R9. The eighth resistor R8 and the first capacitor C1 are connected in parallel between the base and the emitter of the driving transistor Q1 and are grounded. One end of the ninth resistor R9 is connected with the base of the driving transistor Q1, and the other end is connected with the control output end.

In one embodiment, the voltage dividing filter circuit 30 includes a sixth resistor R6, a tenth resistor R10, and a first capacitor C2. The sixth resistor R6 is connected between the voltage output terminal and the voltage sampling terminal. The tenth resistor R10 and the first capacitor C2 are connected in parallel between the voltage sampling terminal and the ground terminal GND.

In one embodiment, the sampling resistors R2 and R11 have a resistance of 45m Ω to 55m Ω, the first bias resistors R1 and R12 have a resistance of 25 Ω to 35 Ω, and the pull-down resistor R7 has a resistance of about 10K Ω. This parameter is chosen such that the maximum current of the switching unit 20 can be limited to around 12A when the voltage at the voltage input is 36V.

The above embodiments of the present invention do not limit the scope of the present invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. The utility model provides a short-circuit protection module with current-limiting function which characterized in that: the device comprises a switch driving unit, a control unit and at least two switch units; each switch unit is connected in parallel between a voltage input end and a voltage output end;

2. The short-circuit protection module with current limiting function according to claim 1, wherein: the base electrode biasing circuit comprises a first capacitor, an eighth resistor and a ninth resistor; the eighth resistor and the first capacitor are connected in parallel between the base electrode and the emitter electrode of the driving triode; one end of the ninth resistor is connected with the base electrode of the driving triode, and the other end of the ninth resistor is connected with the control output end.

3. The short-circuit protection module with current limiting function according to claim 1, wherein: the voltage division filter circuit comprises a sixth resistor, a tenth resistor and a second capacitor; the sixth resistor is connected between the voltage output end and the voltage sampling end; the tenth resistor and the second capacitor are connected in parallel between the voltage sampling terminal and the ground terminal.

4. The short-circuit protection module with current limiting function according to claim 1, wherein: in the switching unit, the sampling resistor has a resistance value of 45m Ω to 55m Ω, and the first bias resistor has a resistance value of 25 Ω to 35 Ω.