CN201426038Y - Switch power over-voltage protection circuit - Google Patents

Switch power over-voltage protection circuit Download PDF

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Publication number
CN201426038Y
CN201426038Y CN2009201359891U CN200920135989U CN201426038Y CN 201426038 Y CN201426038 Y CN 201426038Y CN 2009201359891 U CN2009201359891 U CN 2009201359891U CN 200920135989 U CN200920135989 U CN 200920135989U CN 201426038 Y CN201426038 Y CN 201426038Y
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CN
China
Prior art keywords
voltage
pwm
master controller
comparator
power supply
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Expired - Fee Related
Application number
CN2009201359891U
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Chinese (zh)
Inventor
石良生
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SHENZHEN LUCKY VALLEY TECHNOLOGY Co Ltd
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SHENZHEN LUCKY VALLEY TECHNOLOGY Co Ltd
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Priority to CN2009201359891U priority Critical patent/CN201426038Y/en
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Publication of CN201426038Y publication Critical patent/CN201426038Y/en
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Abstract

The utility model discloses a switch power over-voltage protection circuit, which includes an input voltage detection circuit, a PWM main controller, a power supply providing circuit, a return difference circuit and a capacitor. A voltage comparator is arranged in the PWM main controller, and the reference voltage is provided by the PWM main controller; after being electrified, the power supply sends out voltage to the voltage detection circuit, the detected voltage is feedback to a reversing end of the comparator through a resistor and compared with the reference voltage, and the compared result controls a controlling end of the PWM main controller; and one end of the capacitor is connected with the reversing end of the comparator, while the other end is connected with the PWM main controller. Compared with the prior art, the arrangement of the capacitor can prevent output at the PWM starting moment, and avoid the problem of intermittent output.

Description

The Switching Power Supply overvoltage crowbar
Technical field
The utility model relates to the Switching Power Supply over-voltage protection technology, particularly a kind of Switching Power Supply overvoltage crowbar that can low-cost prevent error starting.
Background technology
In Switching Power Supply, the purpose of overvoltage protection is: (1) prevents that the voltage stress of loop of power circuit is too big when input voltage is higher than the design maximum input voltage, causes power device to damage.(2) prevent that the pretrigger pulse appears in PWM startup input voltage when input voltage is higher than the design maximum input voltage; therefore the sequential that influences load circuit requires overvoltage crowbar under any input voltage waveform; when input voltage was higher than the design maximum input voltage, PWM must no-output.
Traditional overvoltage crowbar of Switching Power Supply is just like two kinds of implementations of Fig. 1, Fig. 3.Though Fig. 1 can solve the variety of issue of overvoltage protection, needing independently to provide the accessory power supply of VCC electric energy, so there is the high problem of cost for this reason.The overvoltage protection mode of Fig. 3, simple in structure, the efficient height, but but there is the problem that power supply is intermittently exported after the overvoltage.
Describe below in conjunction with circuit diagram 1, sequential chart 2 and circuit diagram 3,4 two kinds of overvoltage protection modes commonly used of sequential chart.
First kind of overvoltage protection mode.Circuit diagram 1, signal waveform are as shown in Figure 2.The course of work is as follows: the VCC power supply is independently provided by accessory power supply, deliver to the reverse input end of comparator after input voltage process R1, the R2 dividing potential drop, reference voltage is delivered to the in-phase input end of comparator by R4, when input voltage is higher than the maximum input voltage of design, the backward end voltage of comparator is higher than in-phase end voltage, comparator 1 pin output low level, 1 pin of control PWM, close output pulse (PWM-OUT among Fig. 2), Switching Power Supply no-output (V OUT is 0)
Program process is as follows during Fig. 1 circuit working: power up at T1 moment power supply, so the VIN of comparator backward end rises owing to the reason that capacitor C 1 is arranged is slow, other each point is electronegative potential.T2 starts working for the VCC circuit provides the accessory power supply of electric energy constantly, and VCC voltage begins to rise from 0V, and VREF begins to rise from 0V.T3 moment VCC voltage rises to the minimum operating voltage 3V of comparator, and comparator is started working.This moment, the VREF voltage of VIN voltage ratio in-phase end of comparator backward end was low, so comparator A is output as high voltage, because VCC voltage does not also reach the cut-in voltage of PWM constantly at T3, so PWM is not at this moment for as state.The VIN voltage of T4 moment comparator backward end surpasses the VREF reference voltage of in-phase end, and comparator A is output as electronegative potential.T5 moment VCC voltage reaches the minimum operating voltage of PWM, and VREF2 sets up, because comparator A is output as electronegative potential, thereby causes the 1 pin COMP end of PWM to be dragged down the output of PWM no pulse.
Second kind of overvoltage protection mode.Circuit diagram 3, its main signal waveform such as Fig. 4, the course of work is as follows: R1, R2 form input voltage detection circuit among Fig. 3, and R3, R4, R6, Q1 form the return difference circuit, and R7, C2, D1 composition VCC provide circuit.Voltage comparator is in the PWM master controller, reference voltage is provided by PWM master control device, detect voltage feeds back to comparator by R5 backward end, the accurate voltage 2.5V of end group in the same way that provides with PWM compares, comparative result control COMP end, the COMP end is the control end of PWM master controller, and voltage comparator has been controlled the COMP end, has just controlled the pulse output of PWM.
Fig. 3 exceeds logic timing figure in the working range for input voltage.Describe below in conjunction with Fig. 3.
In the middle of the sequential logic figure of Fig. 3, at T1 constantly, power supply electrifying, VIN voltage rises, and input voltage is through R1, R2 dividing potential drop, and to the charging of the VFB of PWM backward end control end, VCC begins by resistance R 7 to capacitor C 2 chargings by R5.Reach the cut-in voltage 16V of PWM master controller to T2 moment VCC voltage.This moment, VREF set up.Detect voltage through the input after R1, the R2 dividing potential drop and be higher than little by little voltage of the inner amplifier in-phase end of PWM benchmark 2.5V, because amplifier has the relation of input and output multiplication factor, so in the moment that the PWM master controller is opened, the COMP terminal voltage of amplifier can not drag down rapidly.Because the COMP end is the work control end of PWM master controller, so this moment, the PWM master controller had pwm pulse output.The COMP end can the output electronegative potential after the comparator of PWM master controller inside compared a period of time with VFB voltage with inner 2.5V reference voltage.T3-T4 constantly, because master controller does not have pulse output, various power circuits all do not have work, so D1 can not provide energy for PWM, and can not keep the operate as normal of PWM by the energy that R7 provides, so VCC voltage just drops to the shutoff voltage point T4 of PWM master controller from the cut-in voltage point of PWM master controller.Charge to C2 by R7 resistance once more from T4 moment VCC, repeat above-mentioned logical process once more, after input terminal voltage surpasses the design maximum voltage, the logical process of the just continuous repetition foregoing circuit of the circuit of Fig. 6.
All there is shortcoming separately in above-mentioned two kinds of overvoltage protection modes, first kind of overvoltage protection mode circuit complexity, cost height.Second kind of overvoltage protection mode has the intermittently problem of output after having overvoltage.
The utility model content
The purpose of this utility model is to overcome the higher deficiency of conventional switch power supply overvoltage protection cost; a kind of simple in structure, efficient is high, cost is low Switching Power Supply overvoltage crowbar is provided; effectively to avoid power device after exceeding the design voltage scope, to damage, improve the reliability of Switching Power Supply.
A kind of Switching Power Supply overvoltage crowbar; it comprises input voltage detection circuit; the PWM master controller; power supply provides circuit and return difference circuit; be provided with voltage comparator in the PWM master controller; reference voltage is provided by the PWM master controller; behind the described power supply electrifying; output voltage is given input voltage detection circuit; detect voltage feeds back to comparator by a resistance backward end; with reference voltage relatively; the control end of comparative result control PWM master controller; it also comprises an electric capacity, and the described electric capacity one end also backward end of comparator links to each other, and the other end links to each other with the PWM master controller.
The utility model circuit structure is simple, the technical conceive novelty, and design logic is clear, the efficient height, cost is low, the dynamic over-voltage protecting function of over-voltage protecting function and any input voltage uphill process when having quiescent imput voltage.In addition, this overvoltage crowbar is confirmed by experiment that circuit is used in 145-264V and exchanges input; in the AC/DC power supply of 26V/8A, 9V/7A, under various environment, can realize over-voltage protecting function accurately; power initiation and the output voltage waveforms dullness when turn-offing promptly do not have pretrigger or restart.Compare with commonly using, the setting of electric capacity can prevent that starting moment at PWM just has output, avoids taking place the intermittently problem of output.
Below in conjunction with drawings and Examples, the technical solution of the utility model is described in further detail.
Description of drawings
Fig. 1 is present industry first kind of overvoltage crowbar commonly used;
Fig. 2 is present industry first kind of main signal waveforms of overvoltage crowbar commonly used;
Fig. 3 is present industry second kind of overvoltage crowbar commonly used;
Fig. 4 is present industry second kind of main signal waveforms of overvoltage crowbar commonly used;
Fig. 5 is an embodiment of overvoltage crowbar of the present invention;
Fig. 6 is the sequential logic figure that surpasses design load Fig. 5 circuit when powering on when input voltage;
Fig. 7 is as the sequential logic figure of input voltage at normal range (NR) Fig. 5 circuit when powering on.
Embodiment
Below in conjunction with accompanying drawing to this novel being described further.
Shown in Figure 5, the utility model discloses a kind of Switching Power Supply overvoltage crowbar, it comprises that input voltage detection circuit 1, PWM master controller 2, power supply provide circuit 3 and return difference circuit 4, wherein:
Input voltage detection circuit 1 is made up of resistance R 1, resistance R 2.
Be provided with voltage comparator in the PWM master controller, reference voltage is provided by the PWM master controller.
Power supply provides circuit 3 to be made up of resistance R 7, capacitor C 2, diode D1.
Return difference circuit 4 is by resistance R 3, resistance R 4, resistance R 6, triode Q1.
Behind the power supply electrifying, output voltage is given input voltage detection circuit 1, detect voltage feeds back to the comparator in the PWM master controller 2 by resistance R 5 backward end, with reference voltage relatively, comparative result control COMP end, the COMP end is the control end of PWM master controller 2, and voltage comparator has been controlled the COMP end, has also just controlled the pulse output of PWM master controller 2.
Above-mentioned protective circuit also comprises a capacitor C 1, and the capacitor C 1 one ends also backward end of comparator link to each other, and the other end links to each other with PWM master controller 2.
Fig. 6 exceeds logic timing figure in the working range for input voltage.Describe below in conjunction with Fig. 5.
In the middle of the sequential logic figure of Fig. 6 at T1 constantly, power supply electrifying, VIN voltage rises, input voltage is through two resistance R 1, resistance R 2 dividing potential drops of input voltage detection circuit 1, the VFB control end charging of the backward end by the comparator of resistance R 5 in PWM controller 2, VCC begins by resistance R 7 to capacitor C 2 chargings.Reach the cut-in voltage 16V of PWM master controller to T2 moment VCC voltage.This moment, VREF set up, owing to the electric capacity both end voltage can not be suddenlyd change, so by C1 the voltage of the VFB control end of PWM controller is drawn high when VREF sets up.VFB is reverse control end in PWM controller 2 inside, the reference voltage that is provided by the VFB voltage drawn high and PWM master controller inside relatively after, COMP terminal voltage step-down.Because the COMP end is the work control end of PWM master controller, so this moment, the PWM master controller did not have pwm pulse output.In the T3 moment, the VFB voltage of drawing high is owing to have resistance R 2,1 charging of 5 pairs of capacitor C of resistance R, and voltage descends, and is the same with the voltage of resistance R 1, resistance R 2 dividing points to T3 moment VFB point voltage, accurately detects input voltage value.The comparator of PWM master controller 2 inside is relatively exported electronegative potential in the COMP end in the back with VFB voltage with inner 2.5V reference voltage.(VFB voltage is higher than 2.5V when input voltage is higher than working range) T3-T4 constantly, because master controller 2 does not have pulse output, various power circuits all do not have work, so D1 can not provide energy for PWM, and can not keep the operate as normal of PWM controller 2 by the energy that resistance R 7 provides, so VCC voltage just drops to the shutoff voltage point T4 of PWM master controller 2 from the cut-in voltage point of PWM master controller 2.From T4 constantly VCC once more by resistance R 7 resistance to capacitor C 2 chargings, repeat above-mentioned logical process once more, after input terminal voltage surpassed the design maximum voltage, the circuit of Fig. 5 is many times the logical process of repetition foregoing circuit just.
Fig. 7 is the logic timing figure of input voltage in the normal design working range.Describe below in conjunction with Fig. 5.
At T1 constantly, power supply electrifying, VIN voltage rises, and input voltage is through resistance R 1, resistance R 2 dividing potential drops, and to the charging of the VFB of the backward end of PWM master controller 2 control end, VCC begins by resistance R 7 to capacitor C 2 chargings by resistance R 5.Reach the cut-in voltage 16V of PWM master controller 2 to T2 moment VCC voltage.This moment, VREF set up, owing to the electric capacity both end voltage can not be suddenlyd change, so by capacitor C 1 voltage of the VFB control end of PWM controller is drawn high when VREF sets up.VFB is reverse control end in PWM controller inside, the reference voltage that is provided by the VFB voltage drawn high and PWM master controller inside relatively after, COMP terminal voltage step-down.Because the COMP end is the work control end of PWM master controller, so this moment, the PWM master controller did not have pwm pulse output.In the T3 moment, the VFB voltage of drawing high is owing to have resistance R 2,1 charging of 5 pairs of capacitor C of resistance R, and voltage descends, and is the same with the voltage of resistance R 1, resistance R 2 dividing points to T3 moment VFB point voltage, accurately detects input voltage value.(input voltage during in normal range of operation VFB voltage be lower than 2.5V) comparator of PWM master controller inside with VFB voltage with inner 2.5V reference voltage relatively the back in COMP end output high potential, PWM master controller output pwm pulse, each power circuit work, D1 provides energy to VCC, and power supply enters normal operating conditions.
Over-voltage protection method of the present utility model and circuit are confirmed by experiment; this circuit is used in 145-264V and exchanges input; in the AC/DC power supply of 26V/8A, 9V/7A; under various environment; can realize over-voltage protecting function accurately; power initiation and the output voltage waveforms dullness when turn-offing promptly do not have pretrigger or restart.

Claims (1)

1; a kind of Switching Power Supply overvoltage crowbar; it comprises input voltage detection circuit; the PWM master controller; power supply provides circuit and return difference circuit; be provided with voltage comparator in the PWM master controller; reference voltage is provided by the PWM master controller; behind the described power supply electrifying; output voltage is given input voltage detection circuit; detect voltage feeds back to comparator by a resistance backward end; with reference voltage relatively; the control end of comparative result control PWM master controller; it is characterized in that: it also comprises an electric capacity, and described electric capacity one end links to each other with the backward end of comparator, and the other end links to each other with the PWM master controller.
CN2009201359891U 2009-03-30 2009-03-30 Switch power over-voltage protection circuit Expired - Fee Related CN201426038Y (en)

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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN101969722A (en) * 2010-09-27 2011-02-09 海洋王照明科技股份有限公司 LED drive circuit and LED lamp
CN102231536A (en) * 2010-08-08 2011-11-02 浙江上方光伏科技有限公司 Hysteresis power management circuit
CN102709872A (en) * 2012-05-24 2012-10-03 华为技术有限公司 Overvoltage protection control device and method
CN106067675A (en) * 2015-04-23 2016-11-02 旺玖科技股份有限公司 High voltage protection system

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102231536A (en) * 2010-08-08 2011-11-02 浙江上方光伏科技有限公司 Hysteresis power management circuit
CN101969722A (en) * 2010-09-27 2011-02-09 海洋王照明科技股份有限公司 LED drive circuit and LED lamp
CN102709872A (en) * 2012-05-24 2012-10-03 华为技术有限公司 Overvoltage protection control device and method
CN102709872B (en) * 2012-05-24 2014-09-17 华为技术有限公司 Overvoltage protection control device and method
CN106067675A (en) * 2015-04-23 2016-11-02 旺玖科技股份有限公司 High voltage protection system
CN106067675B (en) * 2015-04-23 2019-04-16 旺玖科技股份有限公司 High voltage protection system
US10338652B2 (en) 2015-04-23 2019-07-02 Prolific Technology Inc. High voltage protection system for adjusting duty cycle by using pulse width modulation signal

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GR01 Patent grant
C17 Cessation of patent right
CF01 Termination of patent right due to non-payment of annual fee

Granted publication date: 20100317

Termination date: 20130330