CN205681306U - The soft starting circuit that a kind of belt current compensates - Google Patents

Abstract

This utility model discloses the soft starting circuit that a kind of belt current compensates, and it includes soft starting circuit and the current compensation circuit being electrically connected with each other；Described soft starting circuit is used for start-up circuit, and described current compensation circuit is for carrying out current compensation to soft starting circuit；Wherein, soft starting circuit includes PMOS MP1, PMOS MP2, bias current sources Ibs, PNP triode QP1 and electric capacity C1；The source electrode of described PMOS MP1 connects supply voltage, the grid of PMOS MP1 is connected with the input of the drain electrode of PMOS MP1, the grid of PMOS MP2 and bias current sources Ibs, the output head grounding of bias current sources Ibs, the source electrode of PMOS MP2 connects supply voltage, the drain electrode of PMOS MP2 connects the emitter stage of PNP triode QP1, the base stage of PNP triode QP1 is connected with top crown and the current compensation circuit of electric capacity C1, the bottom crown of C1 and the grounded collector of PNP triode QP1.

Description

The soft starting circuit that a kind of belt current compensates

Technical field

This utility model relates to electronic technology field, the soft starting circuit compensated particularly to a kind of belt current.

Background technology

Soft starting circuit is widely used in field of switch power, to improve the stability of Switching Power Supply, it is to avoid Switching Power Supply Startup stage damage Switching Power Supply due to the sudden change (such as surge current) of voltage or electric current.

Existing soft starting circuit charging current when high temperature reduces, and output voltage is not high enough, causes the circuit can not be normal Start.

Therefore, how to design a soft starting circuit, with solve existing soft starting circuit under the high temperature conditions can not be normal A difficult problem for work, is industry problem demanding prompt solution.

Utility model content

Therefore, for above-mentioned problem, the utility model proposes the soft starting circuit that a kind of belt current compensates, this circuit exists On the basis of existing soft starting circuit, add a current compensation circuit, by current compensation circuit, soft starting circuit is carried out High temperature current compensation, so that soft starting circuit the most still can normally work, and ensures that circuit is in high and low temperature condition Under can normally work, thus solve prior art and know deficiency.

In order to solve above-mentioned technical problem, the technical scheme that this utility model is used is as follows:

The soft starting circuit that a kind of belt current compensates, including the soft starting circuit being electrically connected with each other and current compensation electricity Road；Described soft starting circuit is used for start-up circuit, and described current compensation circuit is for carrying out current compensation to soft starting circuit；Its In, soft starting circuit includes PMOS MP1, PMOS MP2, bias current sources Ibs, PNP triode QP1 and electric capacity C1；Described The source electrode of PMOS MP1 connects supply voltage, the grid of PMOS MP1 and the drain electrode of PMOS MP1, the grid of PMOS MP2 and The input of bias current sources Ibs connects, the output head grounding of bias current sources Ibs, and the source electrode of PMOS MP2 connects power supply electricity Pressure, the drain electrode of PMOS MP2 connects the emitter stage of PNP triode QP1, the base stage of PNP triode QP1 and the top crown of electric capacity C1 And current compensation circuit connects, the bottom crown of C1 and the grounded collector of PNP triode QP1.

Described current compensation circuit includes PMOS MP3, PMOS MP4, soft start outfan Vss and NMOS tube MN1；Institute The source electrode stating PMOS MP3 connects supply voltage, the grid of PMOS MP3 and the grid of PMOS MP4, the drain electrode of PMOS MP4 And the drain electrode of NMOS tube MN1 connects, the drain electrode of PMOS MP3 and the base stage of PNP triode QP1, the top crown of electric capacity C1 and soft Starting outfan Vss to connect, the source electrode of PMOS MP4 connects supply voltage, and the grid of PMOS MP4 and drain electrode connect, PMOS The drain electrode of MP4 connects the drain electrode of NMOS tube MN1, the grid of NMOS tube MN1 and source electrode and connects, the source ground of NMOS tube MN1.

This utility model uses such scheme, compared with prior art, has the advantages that

1, this utility model uses current compensation circuit that soft starting circuit is carried out high temperature current compensation, it is achieved at high temperature Soft starting circuit still can normally work, it is ensured that circuit can normally work under the conditions of high and low temperature；

2, the technical scheme that this utility model is used is simple, with low cost, has good practicality.

Accompanying drawing explanation

Fig. 1 is the theory structure schematic diagram of the soft starting circuit that a kind of belt current of the present utility model compensates.

Detailed description of the invention

In conjunction with the drawings and specific embodiments, this utility model is further illustrated.

Seeing Fig. 1, the soft starting circuit that a kind of belt current of this utility model compensates, including soft starting circuit 100 and electric current Compensate circuit 200；Soft starting circuit 100 and current compensation circuit 200 are sequentially electrically connected with；Soft starting circuit 100 is used for starting Circuit, current compensation circuit 200 is for carrying out current compensation to soft starting circuit.

As a specific embodiment, seeing Fig. 1, soft starting circuit 100 includes PMOS MP1, PMOS MP2, partially Put current source Ibs, PNP triode QP1 and electric capacity C1；The source electrode of PMOS MP1 connects supply voltage, the grid of PMOS MP1 with The input of the drain electrode of PMOS MP1, the grid of PMOS MP2 and bias current sources Ibs connects, bias current sources Ibs defeated Going out and hold ground connection, the source electrode of PMOS MP2 connects supply voltage, and the drain electrode of PMOS MP2 connects the emitter stage of PNP triode QP1, The base stage of PNP triode QP1 is connected with top crown and the current compensation circuit of electric capacity C1, the bottom crown of C1 and PNP triode QP1 Grounded collector.

Current compensation circuit includes PMOS MP3, PMOS MP4, soft start outfan Vss and NMOS tube MN1；PMOS The source electrode of MP3 connects supply voltage, the grid of PMOS MP3 and the grid of PMOS MP4, the drain electrode of PMOS MP4 and NMOS tube The drain electrode of MN1 connects, the drain electrode of PMOS MP3 and the base stage of PNP triode QP1, the top crown of electric capacity C1 and soft start output End Vss connects, and the source electrode of PMOS MP4 connects supply voltage, and the grid of PMOS MP4 and drain electrode connect, the drain electrode of PMOS MP4 Connect the drain electrode of NMOS tube MN1, the grid of NMOS tube MN1 and source electrode to connect, the source ground of NMOS tube MN1.

Illustrate its operation logic in detail below.

Assume that in soft starting circuit 100, the size of current of bias current sources is Ibs, transistor (PMOS or NMOS) unit plane Long-pending gate oxide capacitance is Cox, and the hole mobility of PMOS is μ_p, the breadth length ratio of PMOS MPx is (W/L)_MPx, NMOS The electron mobility of pipe is μ_n, the breadth length ratio of NMOS tube MNx is (W/L)_MNx, x is 1,2,3,4.

Seeing soft starting circuit 100 in Fig. 1, its operation principle is: when supply voltage VDD powers on, current offset source Ibs Start normal work, owing to PMOS MP1 and PMOS MP2 constitute current-mirror structure, i.e. PMOS MP2 mirror image PMOS MP1 In electric current (wherein, the size of current in PMOS MP1 is Ibs), then have:

I_MP2:I_MP1=(W/L)_MP2:(W/L)_MP1； (1)

In formula, I_MP2For flowing through the drain current of PMOS MP2, I_MP1For flowing through the drain current of PMOS MP1；

Now, PNP triode QP1 turns on, its emitter current

I_E,QP1=I_MP2； (2)

Its base current I_B,QP1Start electric capacity C1 is charged, and I_B,QP1And I_E,QP1There is a following relation:

I_E,QP1=β * I_B,QP1+(1+β)*I_CBO,QP1； (3)

In formula, β is the current gain of PNP triode QP1；I_CBO,QP1The reverse saturated electricity of colelctor electrode for PNP triode QP1 Stream.

In conjunction with formula (1) (2) (3), available:

Because β > > 1, then have:

$I_{B,QP1}=\frac{{(W/L)}_{MP2}}{\mathrm{\β}{(W/L)}_{MP1}}*I_{bs}-I_{CBO,QP1};---\left(4\right)$

From formula (4), electric capacity C1 is charged by the base current of PNP triode QP1, its size I_B,QP1With PMOS MP1 Breadth length ratio, size of current IBS of bias current sources, the currentgainβ of PNP triode QP1 and PNP tri-pole with PMOS MP2 Pipe QP1 colelctor electrode reverse saturation current I_CBO,QP1Relevant, and two of which variable β and I_CBO,QP1All there is positive temperature coefficient, because of This, under conditions of size of current IBS of PMOS MP1 and the breadth length ratio of PMOS MP2 and bias current sources is certain, along with temperature Degree rises, I_B,QP1Can be gradually reduced, when this circuit height startup temperature, owing to charging current is the least, when less than starting pipe (Vss institute Drive pipe) leakage current time circuit can be made normally to start；When this circuit starts to start from low temperature, warm again after startup Degree raises, then I_CBO,QP1Being gradually increased, a part of electric charge on C1 is held in power down of releasing, so that soft start outfan Vss Power down, causes circuit abnormality.

Therefore, for the problems referred to above, the most still can normally work to realize soft starting circuit, it is ensured that circuit exists Can normally work under the conditions of high and low temperature.This utility model uses current compensation circuit that soft starting circuit is carried out high temperature electric current Compensate, it is achieved at high temperature soft starting circuit still can normally work.Ensure that circuit can normal work under the conditions of high and low temperature Make.

Specific works principle is as follows:

See current compensation circuit 200 in Fig. 1, the grid source short circuit of NMOS tube MN1, and connect with ground end GND, can regard as It is the reverse PN junction diode being connected with GND, its reverse current (that is, the drain current I of NMOS tube MN1_D,MN1) the most not with Backward voltage changes, and it has positive temperature characterisitic.Therefore when high temperature, I_D,MN1Can increase, then, by PMOS MP3 and The current-mirror structure of PMOS MP4, utilizes the PMOS MP3 mirror image to PMOS MP4, and electric capacity C1 carries out current compensation, mends Repaying electric current is:

$I_{D,MP3}=\frac{{(W/L)}_{MP3}}{{(W/L)}_{MP4}}*I_{D,MN1}---\left(5\right)$

In formula, I_D,MP4Drain current for PMOS MP4；

From formula (5), this current compensation circuit can be by increasing PMOS MP3 and the ratio of PMOS MP4 breadth length ratio Value, increases the compensation electric current of electric capacity C1, so that the temperature spot that soft start outfan Vss starts power down moves to higher temperature Dynamic, it is achieved under high temperature, start-up circuit still can normally work.

Although specifically show and describe this utility model in conjunction with preferred embodiment, but those skilled in the art should This is understood, in the spirit and scope of the present utility model limited without departing from appended claims, in form and details On this utility model can be made a variety of changes, be protection domain of the present utility model.

Claims (2)

1. the soft starting circuit that a belt current compensates, it is characterised in that: include soft starting circuit and the electricity being electrically connected with each other Stream compensates circuit；Described soft starting circuit is used for start-up circuit, and described current compensation circuit is for carrying out electricity to soft starting circuit Stream compensates；Wherein, soft starting circuit includes PMOS MP1, PMOS MP2, bias current sources Ibs, PNP triode QP1 and electricity Hold C1；The source electrode of described PMOS MP1 connects supply voltage, the grid of PMOS MP1 and the drain electrode of PMOS MP1, PMOS The grid of MP2 and the input of bias current sources Ibs connect, the output head grounding of bias current sources Ibs, the source of PMOS MP2 Pole connects supply voltage, and the drain electrode of PMOS MP2 connects the emitter stage of PNP triode QP1, the base stage of PNP triode QP1 and electric capacity The top crown of C1 and current compensation circuit connect, the bottom crown of C1 and the grounded collector of PNP triode QP1.

The soft starting circuit that belt current the most according to claim 1 compensates, it is characterised in that: described current compensation circuit bag Include PMOS MP3, PMOS MP4, soft start outfan Vss and NMOS tube MN1；The source electrode of described PMOS MP3 connects power supply electricity Pressure, the grid of PMOS MP3 is connected with the drain electrode of the grid of PMOS MP4, the drain electrode of PMOS MP4 and NMOS tube MN1, PMOS The drain electrode of pipe MP3 is connected with base stage, the top crown of electric capacity C1 and the soft start outfan Vss of PNP triode QP1, PMOS MP4 Source electrode connect supply voltage, the grid of PMOS MP4 and drain electrode connect, PMOS MP4 drain electrode connect NMOS tube MN1 leakage Pole, the grid of NMOS tube MN1 and source electrode connect, the source ground of NMOS tube MN1.