CN208046449U

CN208046449U - A kind of start-up circuit of low conduction voltage drop

Info

Publication number: CN208046449U
Application number: CN201820273918.7U
Authority: CN
Inventors: 郑典清; 冯刚; 李树佳
Original assignee: Mornsun Guangzhou Science and Technology Ltd
Current assignee: Mornsun Guangzhou Science and Technology Ltd
Priority date: 2018-02-26
Filing date: 2018-02-26
Publication date: 2018-11-02
Anticipated expiration: 2028-02-26

Abstract

The utility model provides a kind of start-up circuit of low conduction voltage drop, input voltage can be measured in real time, when detecting input voltage less than setting voltage value, N-MOS pipes are connected, so that the output voltage of start-up circuit and the pressure difference of input voltage are extremely low, ensure that rear class booster circuit starts voltage and follows input voltage substantially；When detecting input voltage higher than setting voltage value, start-up circuit output voltage is limited in the work input voltage range of late-class circuit by voltage limiting circuit work.

Description

A kind of start-up circuit of low conduction voltage drop

Technical field

The utility model is related to a kind of start-up circuit, more particularly to a kind of start-up circuit of low conduction voltage drop.

Background technology

Start-up circuit is widely used in field of switch power.In Switching Power Supply product, no matter primary power source (AC-DC convert Device) or secondary power supply (DC-DC converter), it is required for obtaining energy from input terminal, and provide a metastable power supply Voltage is rear class control circuit or control IC power supplies, thus by control circuit work come driving switch break-make, control inductive Device periodically transmits energy.

In general Switching Power Supply, when starting voltage less than control circuit or control IC minimums to solve input voltage, control Circuit processed or control IC are unable to normal condition because that can not obtain sufficiently high supply voltage, cause corresponding Switching Power Supply Two-stage power supply circuit (such as Fig. 1 structures), first order circuit can be used to arrive wide input voltage limitation clamper for the problem of cannot be started up One lower voltage value, second level circuit by booster circuit (such as BOOST circuits) by prime boost in voltage to meet control Circuit or the normal working voltage of control IC work so that switch power supply system can start work.But due to voltage clamping The pressure drop of circuit input and output side itself is larger so that the input supply voltage of second level booster circuit reduces, and leads to second Grade booster circuit can not work normally, final so that in low input, can not IC normal power supplies in order to control.

As shown in Figure 2 (load is rear class booster circuit), circuit operation principle is conventional voltage clamp circuit scheme：Product Be powered moment, the emitter current of triode Q1 conducting, triode Q1 charges to capacitance C2 rapidly, when capacitance C2 voltages (namely The output plus terminal of start-up circuit is supplied to the voltage of the feeder ear Vcc of control IC) the voltage stabilizing value that rises to zener diode D1 subtracts When going the base stage of triode Q1 with emitter conduction voltage drop, stabilization is not further added by by Vcc voltage, reaches boosting electricity in Vcc voltage When the operating voltage of road, booster circuit is started to work, it is established that rear class control circuit or the supply voltage for controlling IC, but circuit In operating on low voltage, triode Q1 is operated in amplification region, and pressure drop is larger on triode Q1 and resistance R2, reduces Vcc under low pressure Voltage value, cause second level booster circuit that can not work normally so that switch power supply system is difficult to when Vin is relatively low Start.With other kinds of regulator circuit or voltage clamp circuit, it also will appear the problem that pressure difference is excessive under low pressure.

In conclusion wide-voltage range Switching Power Supply start-up circuit is confined in industry at present：It is powered using two-stage electric The product of road scheme or single-stage power supply circuit scheme, first order voltage clamp circuit will appear input and output pressure difference mistake under low pressure Greatly so that the problem of booster circuit or rear class control circuit can not start cannot be satisfied the startup from extremely low voltage to high voltage Voltage range.

Utility model content：

Have in view of that, the utility model proposes a kind of start-up circuits of low conduction voltage drop, can be carried out to input voltage real When detect, when detect input voltage less than setting voltage value when, N-MOS pipes conducting so that the output voltage of start-up circuit with The pressure difference of input voltage is extremely low, ensures that rear class booster circuit starts voltage and follows input voltage substantially；When detecting input voltage When higher than setting voltage value, start-up circuit output voltage is limited in the work of rear class booster circuit by voltage limiting circuit work In input voltage range.

The utility model itself be lost it is extremely low, when input voltage be low-voltage when, driving circuit itself be lost it is relatively low, simultaneously Because being managed using N-MOS, the N-MOS pipes saturation conduction in operating on low voltage, the conducting resistance of start-up circuit is extremely low；In high-pressure work When, voltage limiting circuit can be used satisfaction and lower voltage stabilizing or pressure limiting circuit be lost, and had both ensured and has started electricity under high input voltage The normal work on road, and reduce the loss of start-up circuit work.

A kind of start-up circuit of low conduction voltage drop described in the utility model, including voltage limiting circuit, N-MOS pipe and drive Dynamic circuit.The visible Fig. 3 of concrete principle block diagram.

The input terminal of the driving circuit connects input voltage vin, is generated after carrying out voltage sample to input voltage vin Voltage Vg is controlled, the control voltage Vg is exported to the grid of N-MOS pipes, the drain electrode connection input voltage vin of N-MOS pipes, N- The source electrode of MOS pipes is connected to the output end of start-up circuit, powers for late-class circuit；The input terminal of voltage limiting circuit and output End is connected to drain electrode and the source electrode of N-MOS pipes；

The driving circuit, which is equipped with, judges voltage range, judges electricity when the input voltage vin is less than driving circuit When minimum value between pressure area, N-MOS pipes conducting, by the voltage limiting circuit short circuit, the source electrode by N-MOS pipes is Late-class circuit is powered；

When the input voltage vin is when driving circuit judges in voltage range, the N-MOS is managed and the electricity Pressure limiting circuit is all connected, and is that late-class circuit is powered jointly by the source electrode of N-MOS pipes and the output end of voltage limiting circuit；

When the input voltage vin judges the maximum value of voltage range more than driving circuit, the N-MOS pipes close It is disconnected, it is powered for late-class circuit by the output end of the voltage limiting circuit.

Preferably, the voltage limiting circuit is the electricity that input voltage vin is converted to stable output voltage range Clamp circuit is pressed, or input voltage vin is converted to the regulator circuit of fixed output voltage values.

Preferably, the voltage clamp circuit includes the first chip, the input terminal connection input electricity of first chip Press Vin, the ground terminal ground connection of first chip, the source electrode of the output end connection N-MOS pipes of first chip.

Preferably, the regulator circuit includes second resistance, 3rd resistor, the first NPN triode, the first capacitance and Two zener diodes；The second resistance is connected between input voltage vin and the collector of the first NPN triode, described 3rd resistor be connected between input voltage vin and the base stage of the first NPN triode；The base of first NPN triode The cathode of pole connection second zener diode, the output end of the emitter connection driving circuit of the first NPN triode VDD；The anode connection ground of second zener diode；First capacitance connection is in the output end VDD of driving circuit Between ground.

Preferably, the driving circuit includes first resistor and the first zener diode, and the one of the first resistor End is connected to input voltage vin, and the other end of first resistor is connected with the cathode of first zener diode, and connects Output end output control voltage Vg of the point as driving circuit, the anode of the first zener diode and ground connection.

Preferably, the voltage stabilizing value of first zener diode is less than the voltage stabilizing value of the second zener diode.

Preferably, the driving circuit judges the minimum value of voltage range for the voltage stabilizing value of the first zener diode, institute The driving circuit stated judges the maximum value of voltage range for the threshold voltage of the voltage stabilizing value and N-MOS pipes of the first zener diode The sum of.

Compared with prior art, the utility model has following remarkable result：

1, the utility model using N-MOS pipes come the output voltage of start-up circuit when controlling low pressure, to ensure low pressure When start-up circuit output voltage it is almost the same with input voltage, meet the power demands under rear class booster circuit low pressure.

2, the utility model circuit structure use wide input voltage range regulator circuit or clamp circuit composition Voltage limiting circuit, start-up circuit output voltage is not excessively high when to ensure high input voltage, and it is high to meet rear class booster circuit The input voltage range of pressure.

3, the utility model itself is lost extremely low, the voltage limiting circuit formed using low-loss constant current voltage limiting chip, The voltage sample loss of driving circuit is also smaller, will not be lost due to overflow means circuit characteristic increasing circuit itself.

Description of the drawings：

Fig. 1 is the functional block diagram of traditional wide input range start-up circuit for meeting low pressure input；

Fig. 2 is traditional voltage clamp circuit schematic diagram；

Fig. 3 is the principles of the present invention block diagram；

Fig. 4 is the schematic diagram of the utility model first embodiment；

Fig. 5 is the schematic diagram of the utility model second embodiment；

Fig. 6 is the application principle figure of the utility model first embodiment；

Fig. 7 is the application principle figure of the utility model second embodiment.

Specific implementation mode

Fig. 3 shows functional block diagram, it then follows the connection relation of above-mentioned initial technical solution.First branch illustrates this reality With novel 3 had feature：

1, external powering device works normally, and when input voltage judges the minimum value of voltage range less than driving circuit, opens The output voltage of dynamic circuit is with input voltage almost without pressure difference.

2, external powering device work normally, input voltage when driving circuit judges in voltage range, start-up circuit The pressure difference of output voltage and input voltage slowly increases with the increase of input voltage.

3, external powering device works normally, and when input voltage judges the maximum value of voltage range more than driving circuit, opens Dynamic voltage output voltage stabilization is in a voltage value or stablizes in an output voltage range, unrelated with the variation of input voltage.

First embodiment

The voltage limiting circuit, N-MOS pipes and driving circuit of the utility model, the input terminal connection input electricity of driving circuit Vin is pressed, generation control voltage Vg, the control voltage Vg after input voltage vin progress voltage sample are exported to N-MOS pipes The drain electrode of grid, N-MOS pipes connects input voltage vin, and the source electrode of N-MOS pipes is connected to late-class circuit, is supplied for late-class circuit Electricity；The input terminal and output end of voltage limiting circuit are connected to drain electrode and the source electrode of N-MOS pipes.

For each circuit module, above 3 features are specifically described using circuit in detail below in conjunction with attached drawing 4 It is as follows：

N-MOS pipes TR1 selection depletion type N-MOS pipes, being more than a certain negative value VT in Vgs voltages can be connected.

Voltage limiting circuit is a voltage clamp circuit, including constant current voltage limiting chip IC 1 and the first capacitance C1, IC1 tool There is following characteristic：When output voltage VDD is less than setting voltage value, output voltage VDD follows input voltage vin, when output electricity When pressure is higher than limitation voltage value, output voltage VDD is limited in a voltage range less than setting voltage value.

Driving circuit includes first resistor R1 and the first zener diode Z1.

The input terminal of first chip IC 1 is connected with Vin, and the output end VDD of IC1 is connected with late-class circuit, IC1 ground terminals are grounded；The poles D of the N-MOS pipes TR1 are connected with Vin, and the output end VDD of the poles the S connection IC1 of TR1 is simultaneously And late-class circuit is connected jointly, the poles G of TR1 are connected with the cathode of the first zener diode Z1；First electricity One end of resistance R1 is connected to Vin, and the other end is connected with the cathode of the first zener diode Z1, and tie point is as drive The anode of output end output control the voltage Vg, Z1 of dynamic circuit and ground connection；The first capacitance C1 is connected to the output end of IC1 Between VDD and ground.

The course of work of the utility model is described as follows with reference to Fig. 4：

Feature 1 is worked normally for electric installation, when input voltage judges the minimum value of voltage range less than driving circuit, is started Circuit output voltage is with input voltage almost without pressure difference：

When input voltage is not up to the voltage stabilizing value of zener diode Z1, zener diode Z1 is in cut-off state, input electricity Press G, S capacitances and capacitance C1 charging of the Vin by resistance R1 to N-MOS pipes TR1 so that the G of N-MOS pipes TR1 is extremely to GND's Voltage is equal to input voltage vin, and the G pole tensions of N-MOS pipes TR1 are more than S pole tensions, N-MOS pipes TR1 conductings so that start electricity The output voltage on road is with input voltage almost without pressure difference.

Feature 2 is worked normally for electric installation, and input voltage is when driving circuit judges in voltage range, start-up circuit output The pressure difference of voltage and input voltage slowly increases with the increase of input voltage：

When input voltage is gradually increased to the voltage stabilizing value more than zener diode Z1, and the voltage stabilizing less than zener diode Z1 When being worth the voltage value being added with the absolute value of the threshold voltage VT of N-MOS pipes TR1, the output signal Vg voltages of driving circuit For value stabilization in the voltage stabilizing value of zener diode Z1, N-MOS pipes enter amplification region, and electric current is managed and IC1 by N-MOS between Vin and VDD It is common to provide, during Vin slowly rises, the pressure difference between start-up circuit output voltage VDD and Vin follow N-MOS pipes into Enter amplification region and slowly increases.

Feature 3 is worked normally for electric installation, when input voltage judges the maximum value of voltage range more than driving circuit, is started Circuit output voltage is stablized in a voltage value or is stablized in an output voltage range, unrelated with the variation of input voltage：

When input voltage vin judges the maximum value of voltage range more than driving circuit, i.e., input voltage vin is more than voltage stabilizing When the voltage value that the voltage stabilizing value of diode Z1 is added with the threshold voltage VT of N-MOS pipes TR1, N-MOS pipes enter cut-off region, Electric current is only provided by IC1 between Vin and VDD, and start-up circuit output voltage VDD is directly determined by the stabilizing voltage characteristic of IC1, and will Output voltage stabilization is within the scope of the output voltage limiting value of IC1.

Second embodiment

The present embodiment and first embodiment difference lies in：

Voltage limiting circuit is a regulator circuit, including second resistance R2,3rd resistor R3, the first NPN triode Q1, First capacitance C2 and the second zener diode Z2.

The second resistance R2 is connected between input voltage vin and the poles C of the first NPN triode Q1, and described Three resistance R3 are connected between input voltage vin and the poles B of the first NPN triode Q1；The B of first NPN triode Q1 The cathode of the pole connection second zener diode Z2, the poles E connect the output end VDD of driving circuit；Second voltage stabilizing The anode connection ground GND of diode Z2；The first capacitance C1 be connected to the output end VDD of driving circuit and ground GND it Between.

The voltage stabilizing value of first zener diode Z1 need to be less than the voltage stabilizing value of the second zener diode Z2, such as two pole of the first voltage stabilizing The zener diode of pipe Z1 selections 5.1V, the zener diode of the second zener diode Z2 selections 12V.

The course of work of the utility model is described as follows with reference to Fig. 5：

When input voltage is gradually increased to the voltage stabilizing value more than zener diode Z1, and is less than, zener diode Z1's is steady When the voltage value that pressure value is added with the absolute value of the threshold voltage VT of N-MOS pipes TR1, the output signal Vg voltages of driving circuit For value stabilization in the voltage stabilizing value of zener diode Z1, N-MOS pipes enter amplification region, between Vin and VDD electric current by N-MOS manage with by The linear voltage-stabilizing circuit of R2, R3, Q1 and Z2 composition provides jointly, during Vin slowly rises, start-up circuit output voltage Pressure difference between VDD and Vin follows N-MOS pipes to enter amplification region and slowly increase.

When input voltage vin judges the maximum value of voltage range more than driving circuit, i.e., input voltage vin is more than voltage stabilizing When the voltage value that the voltage stabilizing value of diode Z1 is added with the threshold voltage VT of N-MOS pipes TR1, N-MOS pipes enter cut-off region, Electric current is only provided by the linear voltage-stabilizing circuit that R2, R3, Q1 and Z2 are formed between Vin and VDD, and start-up circuit output voltage VDD is straight The stabilizing voltage characteristic decision by R2, R3, Q1 and Z2 linear voltage-stabilizing circuit formed is connect, and by output voltage stabilization in zener diode The voltage stabilizing value of Z1 subtracts the body diode pressure drop of B, E of triode Q1.

Above are merely preferred embodiments of the utility model, it is noted that above-mentioned preferred embodiment should not regard For the limitation of the utility model, on the basis of the utility model Fig. 3 functional block diagrams, for the ordinary skill people of the art Member for, without departing from the spirit and scope of the utility model, can also make it is alternatively improved and retouching, these improve and Retouching is no longer repeated with embodiment here also in the scope of protection of the utility model, and the scope of protection of the utility model should be with Subject to claim limited range.

Claims

1. a kind of start-up circuit of low conduction voltage drop, it is characterised in that：Including N-MOS pipes, driving circuit and voltage limiting circuit；

The input terminal of the driving circuit connects input voltage vin, and control is generated after carrying out voltage sample to input voltage vin Voltage Vg, the control voltage Vg are exported to the grid of N-MOS pipes, and the drain electrode of N-MOS pipes connects input voltage vin, N-MOS pipes Source electrode be connected to the output end of start-up circuit, power for late-class circuit；The input terminal and output end of voltage limiting circuit are distinguished It is connected to drain electrode and the source electrode of N-MOS pipes；

The driving circuit, which is equipped with, judges voltage range, when the input voltage vin judges voltage zone less than driving circuit Between minimum value when, the described voltage limiting circuit short circuit is rear class by the source electrode of N-MOS pipes by N-MOS pipes conducting Circuit is powered；

When the input voltage vin is when driving circuit judges in voltage range, N-MOS pipes and the voltage limit Circuit processed is all connected, and is that late-class circuit is powered jointly by the source electrode of N-MOS pipes and the output end of voltage limiting circuit；

When the input voltage vin judges the maximum value of voltage range more than driving circuit, N-MOS pipes shutdown, It is powered for late-class circuit by the output end of the voltage limiting circuit.

2. a kind of start-up circuit of low conduction voltage drop according to claim 1, it is characterised in that：The voltage limitation electricity Road is input voltage vin to be converted to the voltage clamp circuit of stable output voltage range, or input voltage vin is turned It is changed to the regulator circuit of fixed output voltage values.

3. a kind of start-up circuit of low conduction voltage drop according to claim 2, it is characterised in that：The voltage clamping electricity Road includes the first chip, and the input terminal of first chip connects input voltage vin, and the ground terminal of first chip is grounded, The source electrode of the output end connection N-MOS pipes of first chip.

4. a kind of start-up circuit of low conduction voltage drop according to claim 2, it is characterised in that：The regulator circuit packet Include second resistance, 3rd resistor, the first NPN triode, the first capacitance and the second zener diode；The second resistance connection Between input voltage vin and the collector of the first NPN triode, the 3rd resistor is connected to input voltage vin and Between the base stage of one NPN triode；The moon of base stage connection second zener diode of first NPN triode Pole, the output end VDD of the emitter connection driving circuit of the first NPN triode；The anode of second zener diode connects Ground connection；First capacitance connection is between the output end VDD and ground of driving circuit.

5. a kind of start-up circuit of low conduction voltage drop according to claim 4, it is characterised in that：The driving circuit packet Include first resistor and the first zener diode, one end of the first resistor is connected to input voltage vin, first resistor it is another One end is connected with the cathode of first zener diode, and output end output control electricity of the tie point as driving circuit Press Vg, the plus earth of the first zener diode.

6. a kind of start-up circuit of low conduction voltage drop according to claim 5, it is characterised in that：First voltage stabilizing, two pole The voltage stabilizing value of pipe is less than the voltage stabilizing value of the second zener diode.

7. a kind of start-up circuit of low conduction voltage drop according to claim 6, it is characterised in that：The driving circuit is sentenced The minimum value of disconnected voltage range is the voltage stabilizing value of the first zener diode, and the driving circuit judges the maximum value of voltage range For the sum of the threshold voltage of the voltage stabilizing value and N-MOS pipes of the first zener diode.