CN2792013Y

CN2792013Y - Active clamping drive circuit and its back power transistor protective circuit

Info

Publication number: CN2792013Y
Application number: CNU2004201054941U
Authority: CN
Inventors: 李战伟; 王庆棉; 朱红伟
Original assignee: SHENZHEN VAPEL POWER SUPPLY TECHNOLOGY Co Ltd
Current assignee: SHENZHEN VAPEL POWER SUPPLY TECHNOLOGY Co Ltd
Priority date: 2004-12-03
Filing date: 2004-12-03
Publication date: 2006-06-28
Anticipated expiration: 2014-12-03

Abstract

The utility model discloses a protective circuit of an active embedding driving circuit and a reverse power transistor thereof. The protective circuit comprises an amplifying transistor (Q4), a second voltage division resistor (R2) and a third voltage division resistor (R3), wherein one end of the second voltage division resistor is connected with a second conduction pole of the reverse power transistor, and the other end of the second voltage division resistor is connected with the third voltage division resistor, and the other end of the third voltage division resistor is earthed; the input pole of the amplifying transistor is connected with the communal end between the second voltage division resistor and the third voltage division resistor, the output pole of the amplifying transistor is earthed, the biasing pole of the amplifying transistor is connected with the control pole of the reverse power transistor. The utility model uses driving technology, reverse technology and current-limiting technology in the driving of an active embedding type embedding pipe; thus, an excessively high drain current of the reversely amplifying transistor is ideally suppressed, a power transistor is protected and the reliability of active embedding driving is enhanced.

Description

Active inserting position driving circuit and backward power Prective circuit for transistor thereof

[technical field]:

The utility model circuit relates to the drive circuit that is used for field of power supplies, specifically is to be used for active clamped Drive Protecting Circuit.

[background technology]:

Along with power supply being extensive use of in each field; market requires price more and more lower to power supply; reliability requirement is more and more higher; its driving of original active clamped technology is made of chip for driving; cost is higher, is difficult to reduce, perhaps directly by oppositely driving totem-pole amplifier with power field effect pipe; oppositely there is no the better protect device with power field effect pipe, then field effect transistor is possibly because of overcurrent or the too big permanent damages of power consumption.

[summary of the invention]:

The purpose of this utility model overcomes the above problems exactly, provides a kind of and can effectively protect active clamped backward power transistor, prolongs the power supply drive circuit and the transistorized protective circuit of backward power thereof in useful life.

For achieving the above object, the utility model circuit has proposed a kind of active inserting position driving circuit, comprises backward power transistor Q3, pull-up resistor R6, current-limiting resistance R1 and totem-pole amplifier; The described backward power transistor first conducting utmost point connects described pull-up resistor and described totem amplifier in; Described resistance flowing resistance one end connects the described backward power transistor second conducting utmost point, and other end ground connection also comprises current foldback circuit, and its sampling end connects the described backward power transistor second conducting utmost point, and output connects the described backward power transistor controls utmost point.

The disclosed above-mentioned transistorized current foldback circuit of active inserting position driving circuit backward power that is used for of the utility model, comprise amplifier transistor Q4, the second divider resistance R2 and the 3rd divider resistance R3, described second divider resistance, one end connects the described backward power transistor second conducting utmost point, one end connects described the 3rd divider resistance, described the 3rd divider resistance other end ground connection; The described amplifier transistor input utmost point connects the common port of described second divider resistance and the 3rd divider resistance, output stage ground connection, and the biasing utmost point connects the described backward power transistor controls utmost point.Described amplifier transistor is triode or field effect transistor.The preferred NPN triode of described triode.Described current foldback circuit comprises that also the 4th resistance R 4, one ends are connected in the described amplifier transistor biasing utmost point, and the other end connects the common port of second divider resistance, current-limiting resistance.

Above-mentioned active inserting position driving circuit, described backward power transistor Q3 is field effect transistor or triode.

The utility model is set up current foldback circuit, with drive, oppositely and current limiting technique be used for simultaneously among the driving of active clamped clamped pipe, suppressed reverse ideally and protected power transistor, improved the reliability of active clamped driving greatly with the too high leakage level electric current of power transistor; The useful life of having improved power circuit greatly simultaneously.

Circuit is simple and reliable, easily realizes, and is with low cost.

This circuit is tested in active clamped circuit, can suppress to leak the level electric current well, the also checking through producing in batches, and its circuit working is reliable and stable.

[description of drawings]:

Fig. 1 drives the drive circuit figure of usefulness for conventional counter;

Fig. 2 is the circuit theory diagrams of the utility model circuit embodiments one;

Fig. 3 is the circuit theory diagrams of the utility model circuit embodiments two;

Fig. 4 is the circuit theory diagrams of the utility model circuit embodiments three;

Fig. 5 is the circuit theory diagrams of the utility model circuit embodiments four;

Fig. 6 is the active inserting position driving circuit embodiment circuit theory diagrams that adopted Fig. 2 protective circuit.

[embodiment]:

The concrete enforcement circuit of the following drawings is done detailed description to this novel practical circuit.

Embodiment one: the drive signal basically of active-clamp main switch field effect transistor and clamp field effect transistor is antilogical, and physical circuit as shown in Figure 6.Active clamping circuir is in the course of work of reality, and there is certain Dead Time in main switch Q1 between (see figure 6) shutoff and clamped pipe Q2 open, and this Dead Time can obtain by the driving time-delay of regulating Q1.Actual driving DVR signal (PWM ripple) has the 200-300mS time difference with the rising edge of the drive waveforms (VGS) of main switch Q1.PNP triode Q5, Q6 form the totem amplifier, drive signal DVR drives Q3 by R5, in the time of tens nanoseconds, will allow the backward power transistor be power field effect pipe Q3 conducting in this example, but also not conducting of Q1 this moment also has higher voltage (the voltage stack by input voltage and clamped electric capacity is formed) between the drain-source level (DS) of Q1.And the Q2 shutoff is a prerequisite with the Q3 conducting; so when the Q3 conducting; amplitude is the voltage of Vin+Vcl; can be added on the Q3 by current collection level and the ground level (CB joint) of PNP triode Q6; then power field effect pipe Q3 has very big peak current and flows through Q3; this moment, then resistance R 1, power field effect pipe Q3 and PNP triode Q6 may cause permanent damages because of overcurrent if do not protect components and parts.

In this example; between the grid and source electrode of Q3; set up a current foldback circuit; as Fig. 2; shown in Figure 6; pull-up resistor is connected between the drain electrode and power supply VCC of Q3; resistance flowing resistance R1 string is between the source class and ground of power field effect pipe Q3; resistance R 1 plays current limliting and current detecting effect when Q3 opens; after the current sampling of the resistance R of flowing through 1 becomes voltage signal; dividing potential drop through the second divider resistance R2 and the 3rd divider resistance R3; the voltage that obtains on R3 is supplied with the input utmost point of amplifier transistor, and the NPN triode Q4 ground level that promptly adopts in this example is in magnifying state to regulate NPN triode Q4; adjust the grid step voltage of power field effect pipe Q3; make it also be in magnifying state, so just changed the electric current that flows through between power tube drain-source level (DS level), played protective effect.

For example: if for the DC-DC power supply, be input as the situation of 36-72VDC, during stable state, the VDS peak value of main switch Q1 is about

During output abnormality (such as output short-circuit or other situations), the VDS peak value of main switch can rise to (relevant with different other characteristics of open loop duty ratio D level) about 190V, then as not adding current-limiting apparatus, the electric current that this voltage produces on Q3, Q6 branch road is very big, may smash triode Q6 or field effect transistor Q3.Choosing of resistance R 1 will be considered abnormal conditions, as output short-circuit etc.Resistance R 2, R3 and triode Q4 play double protection.Excessive as the Id of Q3, Q4 can be in the amplification situation, drags down the VGS of Q3, makes Q3 be in magnifying state, reduces the voltage of R1 like this, also reaches to reduce Id the effect of protection Q3.

Embodiment two: as shown in Figure 3, this example is that with the difference of embodiment one backward power transistor Q3 adopts the NPN triode, and its base stage is the control utmost point, the second conducting utmost point is that emitter passes through resistance flowing resistance R1 ground connection, and the first conducting utmost point is that collector electrode connects pull-up resistor R6.

Embodiment three: as shown in Figure 4; this example is with the difference of embodiment one; the amplifier transistor Q4 of current foldback circuit adopts field effect transistor; its input utmost point is the common port that grid connects R2, R3; output stage is a source ground, and the biasing utmost point promptly drains and connects the control utmost point of backward power field effect transistor Q3.

Embodiment four: as shown in Figure 5; this example is with the difference of embodiment one; the amplifier transistor Q4 of current foldback circuit adopts field effect transistor; its input utmost point is the common port that grid connects R2, R3; output stage is a source ground, and the biasing utmost point promptly drains and connects the control utmost point of backward power field effect transistor Q3.Backward power transistor Q3 adopts the NPN triode, and its base stage is the control utmost point, and the second conducting utmost point is that emitter passes through resistance flowing resistance R1 ground connection, and the first conducting utmost point is that collector electrode connects pull-up resistor R6.

Claims

1, a kind of active inserting position driving circuit comprises backward power transistor (Q3), pull-up resistor (R6), current-limiting resistance (R1) and totem-pole amplifier; The described backward power transistor first conducting utmost point connects described pull-up resistor and described totem amplifier in; Described resistance flowing resistance one end connects the described backward power transistor second conducting utmost point; other end ground connection; it is characterized in that: also comprise current foldback circuit, its sampling end connects the described backward power transistor second conducting utmost point, and output connects the described backward power transistor controls utmost point.

2, active inserting position driving circuit as claimed in claim 1, it is characterized in that: described current foldback circuit comprises amplifier transistor (Q4), second divider resistance (R2) and the 3rd divider resistance (R3), described second divider resistance, one end connects the described backward power transistor second conducting utmost point, one end connects described the 3rd divider resistance, described the 3rd divider resistance other end ground connection; The described amplifier transistor input utmost point connects the common port of described second divider resistance and the 3rd divider resistance, output stage ground connection, and the biasing utmost point connects the described backward power transistor controls utmost point.

3, active inserting position driving circuit as claimed in claim 2 is characterized in that: described amplifier transistor is triode or field effect transistor.

4, active inserting position driving circuit as claimed in claim 3 is characterized in that: described triode is the NPN triode.

5, as each described active inserting position driving circuit among the claim 2-4; it is characterized in that: described current foldback circuit also comprises the 4th resistance (R4); one end is connected in the described amplifier transistor biasing utmost point, and the other end connects the common port of second divider resistance, current-limiting resistance.

6, as each described active inserting position driving circuit among the claim 1-4, it is characterized in that: described backward power transistor (Q3) is field effect transistor or triode.