CN2728101Y

CN2728101Y - Short circuit protection circuit based on P channel MOSFET

Info

Publication number: CN2728101Y
Application number: CN 200420088441
Authority: CN
Inventors: 方志群; 张晓鸿; 张军永
Original assignee: SHENZHEN SHANXING COMPUTER CO Ltd
Current assignee: SHENZHEN SHANXING COMPUTER CO Ltd
Priority date: 2004-09-21
Filing date: 2004-09-21
Publication date: 2005-09-21
Anticipated expiration: 2014-09-21

Abstract

The utility model relates to a short circuit protection circuit based on P channel MOSFET for power equipment, comprising a P channel MOSFET and load. The drain electrode of the MOSFET is connected with the load; the source electrode of the MOSFET is connected with the input terminal; the load is grounded. The utility model is characterized in that: a PNP transistor is connected between the source electrode of the MOSFET and the grid; the emitter electrode of the transistor is connected with the source electrode of the MOSFET, and the collector electrode of the transistor is connected with the grid of the MOSFET; the transistor is arranged with the branch circuit of the bias current; a capacitor is connected between the emitter electrode of the transistor and the base electrode; a diode is connected between the drain electrode of the MOSFET and the base electrode of the transistor; the anode of the diode is connected with the drain electrode of the MOSFET; the terminal of the branch circuit of the bias current is connected in series with an optical coupler which is triggered and conducted through a trigger switch; the base electrode of the transistor is connected in series with one or two step-down diodes. The utility model has no additional power consumption, low cost, high reaction sensitivity, and high anti-interference capability.

Description

Short-circuit protection circuit based on the P-channel metal-oxide-semiconductor field effect transistor

Technical field

The utility model relates to power-supply device, relates in particular to a kind of short-circuit protection circuit based on the P-channel metal-oxide-semiconductor field effect transistor.

Background technology

Metal oxide semiconductor field effect tube; be that MOSFET is a kind of one pole type voltage controlled element; it is very fast that it has switching speed; high input impedance and low drive current; the safety operation area is big; no second breakdown problem; drain current has good advantages such as thermal stability for negative temperature coefficient; general short-circuit protection circuit often adopts current transformer to detect electric current or external sample resistance detects voltage; the typical circuit figure that passes through sample resistance detection voltage as shown in Figure 1, its operation principle is as follows:

When connecting load LOAD, direct current Vcc+5V voltage is by resistance R 6, R2 dividing potential drop, at fixing magnitude of voltage of comparator AR positive input input, during the circuit operate as normal, this magnitude of voltage is higher than the negative input voltage value of setting, comparator AR exports high potential, by resistance R 7 current limlitings, make triode Q1 conducting, after the triode Q1 conducting, power input voltage Vin forms the loop by resistance R 1, resistance R 9 and triode Q1, gets a magnitude of voltage at the grid of MOSFET Q, make MOSFET Q conducting, the circuit operate as normal.When load LOAD overcurrent or short circuit, detect on the resistance R 4 and detect the voltage that is higher than set point, this voltage is higher than the positive input voltage; by resistance R 5 input comparator AR negative-phase inputs, comparator AR upset, output electronegative potential; triode Q1 turn-offs; the grid voltage of MOSFET Q raises, and MOSFET Q turn-offs, and circuit has just obtained protection; this design circuit complexity; cost is higher, and it is big to detect ohmically excessive power drain, and reaction is sensitive inadequately.

Summary of the invention

The purpose of this utility model is to provide that a kind of cost is low, power consumption is little, and sensitive short-circuit protection circuit based on the P-channel metal-oxide-semiconductor field effect transistor, to remedy defective of the prior art.

The technical scheme that the utility model adopted is: this short-circuit protection circuit based on the P-channel metal-oxide-semiconductor field effect transistor, comprise P-channel metal-oxide-semiconductor field effect transistor MOSFET and load, the MOSFET drain electrode links to each other with load, the MOSFET source electrode links to each other with input, load ground connection, it is characterized in that: be connected the PNP triode between described MOSFET source electrode and the grid, described transistor emitter links to each other with the MOSFET source electrode, and described transistor collector links to each other with the MOSFET grid; Described triode is provided with the bias current branch road; Be connected with electric capacity between described transistor emitter and the base stage; Be connected with diode between described MOSFET drain electrode and the transistor base, the anode of this diode links to each other with the MOSFET drain electrode;

Comprise resistance R 01 and resistance R 02 in the described bias current branch road, resistance R 01 is connected between transistor emitter and the base stage, and resistance R 02 is connected between triode Q01 base stage and the ground wire, and transistor collector connects resistance R 03 to the bias current branch road;

Described bias current branch road end is in series with optocoupler, and described optocoupler is by the trigger switch triggering and conducting;

Described transistor base serial connection buck diode;

Described transistor base is connected in series two or more buck diodes;

Described load LOAD two ends also are connected to light-emitting diode.

The utility model beneficial effect is: in the utility model; be connected the PNP triode between MOSFET source electrode and the grid; transistor emitter links to each other with the MOSFET source electrode; transistor collector links to each other with the MOSFET grid; be connected capacitor C 01 between transistor emitter and the base stage; and be connected with diode D03 between MOSFET drain electrode and the transistor base; the anode of this diode D03 links to each other with the MOSFET drain electrode; at work; the voltage of capacitor C 01 slowly raises; delay the conducting of triode; the remain off state; make the low level that is of transistor collector; be that the MOSFET grid voltage is a low level; make the MOSFET conducting; the high level that is produced in drain electrode after the MOSFET conducting; D03 acts on transistor base by diode; make triode continue remain off; therefore; in the utility model; normal operating conditions makes the triode self-locking; power consumption is very little; and mostly be conventional discrete component in the circuit greatly; cost is lower; when load short circuits; MOSFET drain voltage moment is zero; diode D03 oppositely ends, and capacitor C 01 continues charging, and is very fast; the triode conducting; the MOSFET grid voltage raises rapidly, thereby MOSFET ends rapidly; realize short-circuit protection; because MOSFET drain voltage instantaneous variation almost directly acts on triode, the change in voltage of consequent transistor collector is directly fed back on the MOSFET grid, so; the utility model is quick on the draw; in a word, the utility model need not detect no extra power loss by resistance sampling; circuit is simple; cost is low, the reaction sensitivity height, and antijamming capability is strong; be particularly suitable for the demanding industrial control field of interference free performance; the utility model can also descend the unshorting fault in working order, after fault is got rid of, can reset to control by optocoupler and restart.

Description of drawings

Fig. 1 is the typical circuit figure that detects voltage in the prior art by sample resistance;

Fig. 2 is the utility model circuit theory diagrams.

Embodiment

With embodiment the utility model is described in further detail with reference to the accompanying drawings below:

According to Fig. 2, the utility model comprises the P-channel metal-oxide-semiconductor field effect transistor, be MOSFET Q and load LOAD, MOSFET Q drain electrode links to each other with load LOAD, MOSFET Q source electrode links to each other with input Vin, and load LOAD ground connection is connected PNP triode Q01 between MOSFET Q source electrode and the grid, triode Q01 emitter links to each other with MOSFET Q source electrode, and triode Q01 collector electrode links to each other with MOSFET Q grid.

As shown in Figure 2, triode Q01 base stage serial connection buck diode D01, triode Q01 emitter promptly is connected with capacitor C 01 between end points C and the triode Q01 emitter by being connected with capacitor C 01 between this buck diode D01 and the base stage.

As shown in Figure 2, be connected with diode D03 between MOSFET Q drain electrode and the triode Q01 base stage, be i.e. be connected with diode D03 between end points C and the MOSFET Q drain electrode, the anode of diode D03 links to each other with MOSFET Q drain electrode.

As shown in Figure 2, triode Q01 is provided with bias current branch road 1, comprise resistance R 01 and resistance R 02 in the bias current branch road 1, resistance R 01 is connected between triode Q01 emitter and the base stage, resistance R 02 is connected between triode Q01 base stage and the ground wire G, triode Q01 collector electrode connects resistance R 03 to bias current branch road 1, wherein, bias current branch road 1 end is in series with optocoupler U01, optocoupler U01 is by trigger switch S01 triggering and conducting, as shown in Figure 2, excitation diode among the optocoupler U01 and trigger switch S01 are in series, the route divider resistance R06 that excitation diode and trigger switch S01 are constituted, the branch pressure side of R05 obtains the dividing potential drop of voltage vcc.

Load LOAD two ends also are connected to light-emitting diode D04, and this light-emitting diode D04 and resistance R 04 are in series, light-emitting diode D04 minus earth line G.

Operation principle of the present utility model is as follows:

As shown in Figure 2, voltage vcc is constant input, when input Vin has the voltage input, because the voltage at electrochemical capacitor C01 two ends can not suddenly change, the voltage of end points C slowly raises, electrical potential difference between end points C and input Vin is during less than certain threshold values, this threshold values be specially buck diode D01 and PNP triode Q01 emitter junction conduction voltage drop and, PNP triode Q01 can not conducting, so the voltage drop the when electromotive force of triode Q01 collector electrode is optocoupler U01 conducting is approximately 0.5V, promptly MOSFET Q grid voltage is 0.5V, at this moment, P channel mosfet Q can conducting.

After the MOSFET Q conducting, MOSFET Q drain voltage is the conduction voltage drop that input Vin voltage deducts MOSFET Q, simultaneously, MOSFET Q drain voltage acts on end points C by diode D03, end points C voltage is elevated, triode Q01 is ended, circuit is in normal operating conditions, when circuit was in normal operating conditions, light-emitting diode D04 lighted.

When load LOAD short circuit; MOSFET Q drain voltage moment is zero; diode D03 oppositely ends, and electrochemical capacitor C01 continues charging, and is very fast; electrical potential difference is greater than aforementioned threshold values between end points C and the input Vin; triode Q01 conducting, MOSFET Q grid voltage raises rapidly, reaches the conduction voltage drop that input Vin voltage deducts triode Q01; so MOSFET Q ends rapidly, realize short-circuit protection.

As shown in Figure 2, can directly check load LOAD this moment, the unshorting fault, and fault can be passed through trigger switch S1 reset circuit after getting rid of, and circuit again can operate as normal.

In the utility model, triode Q01 base stage can be connected in series two or more buck diodes according to the needs of circuit working point setting, and is consistent with the above as for structure, the principle of other parts, repeats no more herein.

Claims

1. short-circuit protection circuit based on the P-channel metal-oxide-semiconductor field effect transistor; comprise P-channel metal-oxide-semiconductor field effect transistor MOSFET (Q) and load (LOAD); MOSFET (Q) drain electrode links to each other with load (LOAD); MOSFET (Q) source electrode links to each other with input (Vin); load (LOAD) ground connection is characterized in that:

Be connected PNP triode (Q01) between described MOSFET (Q) source electrode and the grid, described triode (Q01) emitter links to each other with MOSFET (Q) source electrode, and described triode (Q01) collector electrode links to each other with MOSFET (Q) grid; Described triode (Q01) is provided with bias current branch road (1);

Be connected with electric capacity (C01) between described triode (Q01) emitter and the base stage;

Be connected with diode (D03) between described MOSFET (Q) drain electrode and triode (Q01) base stage, the anode of diode (D03) links to each other with MOSFET (Q) drain electrode.

2. the short-circuit protection circuit based on the P-channel metal-oxide-semiconductor field effect transistor according to claim 1; it is characterized in that: comprise resistance (R01) and resistance (R02) in the described bias current branch road (1); resistance (R01) is connected between triode (Q01) emitter and the base stage; resistance (R02) is connected between triode (Q01) base stage and the ground wire (G), and triode (Q01) collector electrode connects resistance (R03) to bias current branch road (1).

3. the short-circuit protection circuit based on the P-channel metal-oxide-semiconductor field effect transistor according to claim 1 and 2; it is characterized in that: described bias current branch road (1) end is in series with optocoupler (U01), and described optocoupler (U01) is by trigger switch (S01) triggering and conducting.

4. the short-circuit protection circuit based on the P-channel metal-oxide-semiconductor field effect transistor according to claim 1 is characterized in that: described triode (Q01) base stage serial connection buck diode (D01).

5. the short-circuit protection circuit based on the P-channel metal-oxide-semiconductor field effect transistor according to claim 1 is characterized in that: described triode (Q01) base stage is connected in series two or more buck diodes.

6. the short-circuit protection circuit based on the P-channel metal-oxide-semiconductor field effect transistor according to claim 1 is characterized in that: described load (LOAD) two ends also are connected to light-emitting diode (D04).