CN207753898U - A kind of output overvoltage protection circuit based on floating ground BUCK frameworks - Google Patents

A kind of output overvoltage protection circuit based on floating ground BUCK frameworks Download PDF

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Publication number
CN207753898U
CN207753898U CN201721838419.XU CN201721838419U CN207753898U CN 207753898 U CN207753898 U CN 207753898U CN 201721838419 U CN201721838419 U CN 201721838419U CN 207753898 U CN207753898 U CN 207753898U
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semiconductor
oxide
metal
output
output end
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不公告发明人
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Shanghai Canrui Technology Co Ltd
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Shanghai Canrui Technology Co Ltd
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Abstract

The utility model provides a kind of output overvoltage protection circuit based on floating ground BUCK frameworks, including:Inductance L0, a termination positive voltage output end, other end ground connection;Resistance R3, a termination negative voltage output end;Diode D5, anode connect negative voltage output end;Resistance R0, the other end of a termination L0 and the cathode of D5, the other end of another termination R3;Operational amplifier, positive input terminate the one end R0;Metal-oxide-semiconductor M1, grid connect the output end of amplifier, and source electrode connects the negative input end of amplifier;Resistance R1, the source electrode of a termination M1, another termination R0 other ends;Current mirror module, the drain electrode of input termination M1, output end are grounded by a capacitance C0;Voltage detection module, first input end connect the output end of current mirror module, and the second input terminal receives a switch control signal, and third input terminal receives a demagnetization detection signal.The utility model is avoided that the false triggering and failure of overvoltage protection, moreover it is possible to interference of the load higher-order of oscillation to external equipment is avoided under the premise of not increasing peripheral component.

Description

A kind of output overvoltage protection circuit based on floating ground BUCK frameworks
Technical field
The utility model is related to field of LED drive more particularly to a kind of output over-voltage protections based on floating ground BUCK frameworks Circuit.
Background technology
LED drive chip usually requires integrated output over-voltage protection function to prevent the excessively high damage of output voltage under abnormal conditions Bad circuit.When the output end of LED drive circuit open circuit or over-pressed exception, LED drive chip must trigger output overvoltage guarantor Protective function turns off output power pipe to control the further up of output voltage, otherwise can make output voltage lasting raising out of control, To which the limit pressure resistance beyond device causes system failure.
With universal and cost the reduction of LED applications, badly, therefore the environment of LED driving applications also becomes increasingly complex When in face of various extreme cases the defencive function of inevitable requirement chip can under the premise of not influencing normal use it is reliable in time Triggering, to effective protection circuit.Currently, common overvoltage protection scheme have it is following two:The first, is adopted by electric resistance partial pressure The voltage at sample demagnetization phase inductance both ends monitors output voltage, when detecting the voltage at inductance both ends higher than pre- in demagnetization phase If overvoltage threshold when, trigger overvoltage protection;Second, by setting minimum demagnetization time, when output voltage rises, electricity in chip The sense demagnetization time is gradually reduced, and output over-voltage protection is then triggered when the minimum demagnetization time that the demagnetization time is less than setting.
Said program has the following problems:(1) two schemes are not direct sampling and outputting voltages, when the demagnetization of inductance Between be as short as being less than the minimum turn-off time that chip interior allows and can not then trigger overvoltage protection, i.e., output over-voltage protection fails;(2) There are false triggering overvoltage protection is easy when noise jamming in electric resistance partial pressure sampling for the first scheme;Second scheme is in input voltage Too low excitation can cause to demagnetize when inadequate the time is too short and that all there is false triggering in false triggering overvoltage protection, i.e. both schemes can Can, it is easy to cause lamp sudden strain of a muscle.
For overvoltage protection failure and the problem of false triggering, disclosed in patent application CN201711403476.X improved Overvoltage protection scheme.As shown in Figure 1, inductance L0 is arranged between the anode and LED- of sustained diode 5 program, in this way Chip (shown in core frame) can directly sample the output voltage between LED+ to LED- by external resistance R4 and internal resistance R0. When output voltage increases, the electric current for flowing through resistance R4 and internal resistance R0 also increases, Rovp pins relative to chip gnd Negative pressure is also more negative, and chip interior will flow through R0's by operational amplifier amp, metal-oxide-semiconductor M1, metal-oxide-semiconductor M2, metal-oxide-semiconductor M3, resistance R1 Resistance R2 is flowed through after current mirror sampling, the voltage generated on resistance R2 will be compared with internal reference voltage vref.Work as output When voltage is increased to overvoltage threshold, comparator comp outputs OVP=1 triggers overvoltage protection.Although the program can be detected directly Output voltage, and reliably trigger overvoltage protection in time in output overvoltage, but due to output loading and switching node, that is, core It is connected directly at gnd to piece, causes output loading with the switching node higher-order of oscillation.When output loading externally has parasitic capacitance When, system will generate external equipment interference.
In this regard, the patent application is further improved.It is specific as shown in Fig. 2, by inductance L0 with moving on to chip gnd with Between LED+, chip arrives the voltage of LED- by internal resistance R0, non-essential resistance R4, R5 detection chip, and the voltage is with power Fluctuating signal is presented in pipe M0 break-makes.Due to inductance be energy storage original paper lead to direct current resistance exchange, so chip to LED- pulsation believe Number direct current average value still be equal to LED+ to LED- between output voltage.Therefore by chip indirectly with R4, R5 Filter capacitor C3 so that small ripple approximate DC is presented in the fluctuating signal decaying of chip Rovp pins, and chip interior is close by this again The triggering overvoltage protection compared with internal vref is added in after the current sample mirror image processing on R0 like DC voltage.Although program energy Fig. 1 higher-order of oscillation interference problems caused by load is connected with switching node are enough avoided, but need to increase electricity in chip periphery Capacitance is hindered, to increase circuit cost.
Utility model content
In view of the above shortcomings of the prior art, the purpose of this utility model is to provide a kind of based on floating ground BUCK frameworks Output overvoltage protection circuit, effectively to avoid the false triggering and failure of overvoltage protection, in the same of reliably triggering output over-voltage protection When, moreover it is possible to interference of the load higher-order of oscillation to external equipment is avoided under the premise of not increasing peripheral component cost.
To achieve the goals above, the utility model adopts the following technical solution:
A kind of output overvoltage protection circuit based on floating ground BUCK frameworks is used in LED drive circuit, the protection circuit packet It includes:
Inductance L0, one terminate positive voltage output end, other end ground connection;
Resistance R3, one terminate negative voltage output end;
Diode D5, anode connect negative voltage output end;
Resistance R0, one terminate the other end of inductance L0 and the cathode of diode D5, the other end of another terminating resistor R3;
Operational amplifier, one end of positive input terminal connecting resistance R0;
Metal-oxide-semiconductor M1, grid connect the output end of the operational amplifier, and source electrode connects the negative input of the operational amplifier End;
Resistance R1, one terminate the source electrode of the metal-oxide-semiconductor M1, the other end of another termination resistance R0;
Current mirror module, input terminate the drain electrode of the metal-oxide-semiconductor M1, and output end is grounded by a capacitance C0;And
Voltage detection module, first input end connect the output end of the current mirror module, and the second input terminal receives a control The switch control signal of the output power pipe M0 is made, third input terminal receives a demagnetization detection signal, the voltage detecting mould Root tuber exports overvoltage protection letter according to the voltage signal of the capacitance C0, the switch control signal and the demagnetization detection signal Number.
Further, the voltage detection module includes:
Or door or, first input end receive the switch control signal, the second input terminal receives an over-pressed comparison signal;
Metal-oxide-semiconductor M4, grid receive the voltage signal of the capacitance C0, and drain electrode connects power end by a current source I1;
Metal-oxide-semiconductor M5, grid connect described or door output end, and drain electrode connects the grid of the metal-oxide-semiconductor M4, and source electrode passes through an electricity Stream source I0 is grounded;
Resistance R4, one terminate the source electrode for stating metal-oxide-semiconductor M4, other end ground connection;
Metal-oxide-semiconductor M6, drain electrode connect the source electrode of the metal-oxide-semiconductor M4, source electrode ground connection;
Phase inverter inv0, input terminate the drain electrode of the metal-oxide-semiconductor M4, and the grid of the output termination metal-oxide-semiconductor M6 is simultaneously defeated Go out the over-pressed comparison signal;
Trigger, first input end connect the output end of the phase inverter inv0, and the second input terminal receives the demagnetization inspection Survey signal;
Phase inverter inv1, input terminate the output end of the trigger, and output end exports the overvoltage protection signal.
Further, the trigger includes:
NAND gate nand0, first input end connect the output end of the phase inverter inv0, and output terminates the phase inverter The input terminal of inv1;
NAND gate nand1, first input end connect the output end of the NAND gate nand0, described in the second input terminal receives Demagnetization detection signal, output terminate the second input terminal of the NAND gate nand0.
Further, the current mirror module includes:
Metal-oxide-semiconductor M2, source electrode connect power end, and drain electrode connects the drain electrode of the metal-oxide-semiconductor M1;And
Metal-oxide-semiconductor M3, grid connect grid and the drain electrode of the metal-oxide-semiconductor M2, and source electrode connects power end, and drain electrode connects the voltage ratio Compared with the first input end of module.
Further, the resistance R0, operational amplifier, metal-oxide-semiconductor M1, resistance R1, current mirror module, resistance R2 and voltage Detection module is integrated in LED drive chip.
By using above-mentioned technical proposal, the utility model has the advantages that compared with the prior art:
The utility model can effectively avoid the false triggering of overvoltage protection and fail and reliably trigger output over-voltage protection, It is avoided that the higher-order of oscillation caused by load is connected directly with switching node simultaneously, and need not additionally increase resistance electricity Hold, to reduce system cost.
Description of the drawings
Fig. 1 is the circuit diagram of an example of prior art output overvoltage protection circuit;
Fig. 2 is the circuit diagram of another example of prior art output overvoltage protection circuit;
Fig. 3 is that the circuit of one embodiment of output overvoltage protection circuit of the utility model based on floating ground BUCK frameworks is former Reason figure;
Fig. 4 is the circuit diagram of one embodiment of voltage detection module in Fig. 3;
Fig. 5 is the oscillogram of key node in Fig. 4.
Specific implementation mode
The utility model is above-mentioned and/or additional aspect and advantage from the following description of the accompanying drawings of embodiments will Become apparent and is readily appreciated that.
The output voltage overvoltage of LED drive circuit, the utility model are provided based on floating ground BUCK frameworks in order to prevent Output overvoltage protection circuit.As shown in figure 4, the overvoltage crowbar is connected in LED drive circuit, including setting is driven in LED Dynamic inductance L0, resistance R3 and the diode D5 of chip (chip is as shown in dashed box) outside further includes being arranged in LED drive chip Resistance R0, operational amplifier amp, metal-oxide-semiconductor M1, capacitance C0, resistance R1, the current mirror module that is made of metal-oxide-semiconductor M2 and M3 with And voltage detection module 1.Wherein, the connection relation between each element is as follows:A termination positive voltage output end LED+ of inductance L0, The ground pin gnd (abbreviation chip) of another chip termination and the output power pipe M0 that LED drive circuit is connect by resistance Rcs Source electrode;A termination negative voltage output end LED- of resistance R3, a Rovp pins of another chip termination;The anode of diode D5 Negative voltage output end LED- is met, cathode is with connecing chip;A chip termination of resistance R0, the Rovp pins of another chip termination; One end of the positive input terminal connecting resistance R0 of operational amplifier amp;The grid of metal-oxide-semiconductor M1 connects the output end of operational amplifier amp, source Pole connects the negative input end of operational amplifier amp;The source electrode of a termination metal-oxide-semiconductor M1 of resistance R1, another terminating resistor R0's is another End;The source electrode of metal-oxide-semiconductor M2 meets power end vdda, and drain electrode connects the drain electrode of metal-oxide-semiconductor M1;The grid of metal-oxide-semiconductor M3 connects the grid of metal-oxide-semiconductor M2 And drain electrode, source electrode meet power end vdda;The top crown of capacitance C0 connects the drain electrode of metal-oxide-semiconductor M3, bottom crown ground connection;Voltage detection module 1 first input end connects the drain electrode of metal-oxide-semiconductor M3, and the second input terminal receives the switch control of a control output power pipe M0 conducting shutdowns Signal swon processed, third input terminal receive the demagnetization detection signal tdfinb generated inside LED drive chip, output end output One overvoltage protection signal ovp, voltage detection module 1 is used to come temporarily in demagnetization detection signal tdfinb, by detecting Vovp electricity Pressure come sentence LED drive circuit whether output overvoltage.
In the present invention, the internal structure of voltage detection module 1 is as shown in figure 4, include:Or door or, first is defeated Enter end and receive switch control signal swon, the second input terminal receives over-pressed comparison signal ovpcomp, ovpcomp an initial value and is 0;Metal-oxide-semiconductor M4, grid receive the voltage Vovp of capacitance C0, and drain electrode connects power end by a current source I1;Metal-oxide-semiconductor M5, grid Pole connects or the output end of door or, and drain electrode connects the grid of metal-oxide-semiconductor M4, and source electrode is grounded by a current source I0;Resistance R4, one termination State the source electrode of metal-oxide-semiconductor M4, other end ground connection;Metal-oxide-semiconductor M6, drain electrode connect the source electrode of metal-oxide-semiconductor M4, source electrode ground connection;Phase inverter inv0, It inputs the drain electrode of termination metal-oxide-semiconductor M4, and the grid of output termination metal-oxide-semiconductor M6 simultaneously exports aforementioned over-pressed comparison signal ovpcomp;It touches Device is sent out, first input end connects the output end of phase inverter inv0, and the second input terminal receives demagnetization detection signal tdfinb;Phase inverter Inv1, the output end of input end in contact hair device, output end output over-voltage protection signal ovp.Wherein, trigger includes:With it is non- Door nand0, first input end connect the output end of phase inverter inv0, and output end connects the input terminal of phase inverter inv1;NAND gate Nand1, first input end connect the output end of NAND gate nand0, and the second input terminal receives demagnetization detection signal tdfinb, output Terminate the second input terminal of NAND gate nand0.
The operation principle of the utility model is as follows:
It is well known that the output voltage Vout=Vin*D for BUCK frameworks, wherein Vin is input voltage, and D is defeated Go out the duty ratio of power tube M0 break-makes.Therefore, in entire switch periods, the sampling to output voltage is exactly to Vin*D in fact Sampling.
Due to being pulsed negative pressure between LED- to chip gnd, when power tube M0 is connected, which is-Vin, then right It is-Vin/ (R3+R0) that Rovp pins, which extract electric current,.The electric current passes through operational amplifier amp, metal-oxide-semiconductor M1, metal-oxide-semiconductor M2, metal-oxide-semiconductor M3 and resistance R1 generate the electric current for flowing to capacitance C0.When power tube M0 is turned off, voltages of the LED- to chip between gnd is continuous The pressure drop for flowing diode D5, can be approximately 0, and it is 0 to extract electric current to Rovp pins.Therefore in entire switch periods, to Rovp The average pumping electric current of pin reflects output voltage.
In entire switch periods, electric current that Rovp pins sample after metal-oxide-semiconductor M2 and M3 mirror image with voltage detecting mould Pull-down current I0 inside block 1 compares, and voltage Vovp is generated on capacitance C0.Voltage detection module 1 is used for capacitance C0's Voltage Vovp is detected.When Vovp is higher than Vthn+I1*R4 (Vthn is the threshold voltage of metal-oxide-semiconductor M4), ovpcomp is triggered =1;When Vovp is less than Vthn, ovpcomp=0 is triggered.Because Vovp from low to high when, ovpcomp is initially 0, then Vovp The threshold value higher than M4 pipes is needed to add the pressure drop on R4 that can just M4 be made to be connected, ovpcomp overturnings are 1.When Vovp from high to low when, Ovpcomp initial values are 1, R4 short-circuit by M6, and Vovp needs the threshold value less than M4 that can just turn it off, and ovpcomp overturnings are 0.
During power tube is connected, it is more than I0 to the electric current of C0 chargings, then Vovp is increased beyond threshold value Vthn+I1*R4, touches Send out ovpcomp=1.During power tube turns off, the charging current of C0 is equal to 0, and pull-down current I0 pulls down Vovp, when under Vovp When being pulled to Vthn, stops drop-down and keep Vovp, and trigger ovpcomp=0.Therefore when each switch period starts, capacitance C0 is It is to be started to charge up from Vovp=Vthn, is discharged at Vthn.
If output voltage increases, Vin*D also increases, and the average pumping electric current that Rovp pins sample also increases, chip The electric current that inside flows to capacitance C0 is consequently increased.Voltage on capacitance C0 shows as the Vovp during power tube is connected and rises, Since output voltage increases after power tube shutdown, the demagnetization time reduces, and the fall times of I0 also reduce.It is flat when charging to C0 When equal electric current is more than I0, Vovp can not be pulled down to Vthn by I0 before demagnetization terminates, and ovpcomp detects signal in demagnetization Tdfinb is always maintained at high level when arriving, to trigger overvoltage protection OVP.
The action relationships of each key job node of the utility model are described in detail with reference to the waveform of Fig. 5:
It is obtained by the pumping current sample to Rovp pins to the electric current I_M3 of capacitance C0 charging, there is electricity in when switch conduction Stream, electric current is 0 when switch OFF.
Vovp voltages are in switch conduction, since charging current rises more than discharge current I0, when more than Vthn+I1* When R4 threshold values, ovpcomp=1 is triggered.
Vovp in switch OFF, discharged by discharge current I0 and declined by charging current 0, when dropping to Vthn, touches Send out ovpcomp=0, shutdown pull-down current I0, Vovp holding.
Tdfinb is that demagnetization detection model overturns as low level, and trigger swon=1, subsequent swon at the end of demagnetization Tdfinb is reset to high level by=1.
When output voltage increases, the demagnetization time reduces, and duty ratio increases, the average pumping that Vout=Vin*D, Rovp are detected Electric current increases.Vovp will be unable to drop to Vthn within the demagnetization time, as tdfinb=0 and ovpcomp=1, then trigger Press protection signal ovp.
It is above-described, only it is some embodiments of the utility model, it is noted that for the common of the art For technical staff, without departing from the principle of this utility model, several improvements and modifications can also be made, these improvement The scope of protection of the utility model is also should be regarded as with retouching.

Claims (5)

1. a kind of output overvoltage protection circuit based on floating ground BUCK frameworks, which is characterized in that the protection circuit includes:
Inductance L0, one terminate positive voltage output end, other end ground connection;
Resistance R3, one terminate negative voltage output end;
Diode D5, anode connect negative voltage output end;
Resistance R0, one terminate the other end of inductance L0 and the cathode of diode D5, the other end of another terminating resistor R3;
Operational amplifier, one end of positive input terminal connecting resistance R0;
Metal-oxide-semiconductor M1, grid connect the output end of the operational amplifier, and source electrode connects the negative input end of the operational amplifier;
Resistance R1, one terminate the source electrode of the metal-oxide-semiconductor M1, the other end of another termination resistance R0;
Current mirror module, input terminate the drain electrode of the metal-oxide-semiconductor M1, and output end is grounded by a capacitance C0;And
Voltage detection module, first input end connect the output end of the current mirror module, and the second input terminal receives a control one The switch control signal of output power pipe M0, third input terminal receive one demagnetization detection signal, the voltage detection module according to Voltage signal, the switch control signal and the demagnetization detection signal of the capacitance C0 exports an overvoltage protection signal.
2. the output overvoltage protection circuit according to claim 1 based on floating ground BUCK frameworks, which is characterized in that the electricity Pressure detection module include:
Or door or, first input end receive the switch control signal, the second input terminal receives an over-pressed comparison signal;
Metal-oxide-semiconductor M4, grid receive the voltage signal of the capacitance C0, and drain electrode connects power end by a current source I1;
Metal-oxide-semiconductor M5, grid connect described or door output end, and drain electrode connects the grid of the metal-oxide-semiconductor M4, and source electrode passes through a current source I0 is grounded;
Resistance R4, one terminate the source electrode for stating metal-oxide-semiconductor M4, other end ground connection;
Metal-oxide-semiconductor M6, drain electrode connect the source electrode of the metal-oxide-semiconductor M4, source electrode ground connection;
Phase inverter inv0, input terminate the drain electrode of the metal-oxide-semiconductor M4, and output terminates the grid of the metal-oxide-semiconductor M6 and exports institute State over-pressed comparison signal;
Trigger, first input end connect the output end of the phase inverter inv0, and the second input terminal receives the demagnetization detection letter Number;
Phase inverter inv1, input terminate the output end of the trigger, and output end exports the overvoltage protection signal.
3. the output overvoltage protection circuit according to claim 2 based on floating ground BUCK frameworks, which is characterized in that described to touch Sending out device includes:
NAND gate nand0, first input end connect the output end of the phase inverter inv0, and output terminates the phase inverter inv1's Input terminal;
NAND gate nand1, first input end connect the output end of the NAND gate nand0, and the second input terminal receives the demagnetization Signal is detected, output terminates the second input terminal of the NAND gate nand0.
4. the output overvoltage protection circuit according to claim 1 based on floating ground BUCK frameworks, which is characterized in that the electricity Flowing mirror module includes:
Metal-oxide-semiconductor M2, source electrode connect power end, and drain electrode connects the drain electrode of the metal-oxide-semiconductor M1;And
Metal-oxide-semiconductor M3, grid connect grid and the drain electrode of the metal-oxide-semiconductor M2, and source electrode connects power end, and drain electrode connects the voltage detecting mould The first input end of block.
5. the output overvoltage protection circuit according to claim 1 based on floating ground BUCK frameworks, which is characterized in that the electricity Resistance R0, operational amplifier, metal-oxide-semiconductor M1, resistance R1, current mirror module, resistance R2 and voltage detection module are integrated in LED driving cores In piece.
CN201721838419.XU 2017-12-25 2017-12-25 A kind of output overvoltage protection circuit based on floating ground BUCK frameworks Withdrawn - After Issue CN207753898U (en)

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Application Number Priority Date Filing Date Title
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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN107979895A (en) * 2017-12-25 2018-05-01 上海灿瑞科技股份有限公司 A kind of output overvoltage protection circuit based on floating ground BUCK frameworks
CN111665890A (en) * 2019-03-08 2020-09-15 深圳市必易微电子有限公司 Floating type constant voltage circuit
CN115955085A (en) * 2023-03-10 2023-04-11 晶艺半导体有限公司 Drive circuit, drive method thereof, control circuit and power supply chip

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN107979895A (en) * 2017-12-25 2018-05-01 上海灿瑞科技股份有限公司 A kind of output overvoltage protection circuit based on floating ground BUCK frameworks
CN107979895B (en) * 2017-12-25 2024-01-05 上海灿瑞科技股份有限公司 Output overvoltage protection circuit based on floating BUCK framework
CN111665890A (en) * 2019-03-08 2020-09-15 深圳市必易微电子有限公司 Floating type constant voltage circuit
CN115955085A (en) * 2023-03-10 2023-04-11 晶艺半导体有限公司 Drive circuit, drive method thereof, control circuit and power supply chip

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