CN204559393U - A kind of Switching Power Supply control chip and inverse-excitation type AC-DC converter - Google Patents
A kind of Switching Power Supply control chip and inverse-excitation type AC-DC converter Download PDFInfo
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- CN204559393U CN204559393U CN201520282962.0U CN201520282962U CN204559393U CN 204559393 U CN204559393 U CN 204559393U CN 201520282962 U CN201520282962 U CN 201520282962U CN 204559393 U CN204559393 U CN 204559393U
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Abstract
The utility model discloses a kind of Switching Power Supply control chip and inverse-excitation type AC-DC converter, described Switching Power Supply control chip comprises sampling unit, slope compensation unit, PWM comparator unit, line voltage compensation control module, line voltage compensation unit, Cycle by Cycle current-limiting protection unit or door, rest-set flip-flop, oscillator and driver element.The Switching Power Supply control chip that the utility model provides, by line voltage compensation control module, detect the ON time of external power metal-oxide-semiconductor, when described ON time is greater than the first Preset Time, in the ON time of next external power metal-oxide-semiconductor, control line voltage compensation unit, makes line voltage compensation unit not carry out line voltage compensation to reference voltage in the second Preset Time; Thus output overcurrent point and recovery point increase with line voltage and increase under preventing low pressure.Make in each cycle, the ON time of external power metal-oxide-semiconductor is all longer, improves power output.
Description
Technical field
The utility model relates to switch power technology field, particularly a kind of Switching Power Supply control chip and inverse-excitation type AC-DC converter.
Background technology
Fig. 1 is the circuit diagram of a traditional inverse-excitation type AC-DC converter.When load output did not reach flow point, the cut-off signals of the OUT end of control chip U1 is controlled by feedback voltage (holding input from FB) and primary current detection signal (hold from CS and input).When output loading reached very greatly flow point, it is very high that the voltage of the FB of control chip U1 end became, and the cut-off signals that now the OUT end of control chip U1 exports is decided by the peak value of former limit inductive current.There is certain turn-off delay Tdelay in the drive singal exported due to the OUT end of control chip U1, so under different input voltage vin, former limit inductive current peak can superposition a △ Ipk=, Lp be former limit inductance after drive singal turns off.In the voltage range of 85VAC-264VAC, in order to make output overcurrent point/recovery point have consistency, line voltage compensation is done to former limit inductive current threshold value.But under specific application (under transformer parameter), during low pressure input, easily there is large small echo, see Fig. 2 in former limit inductor current signal.What occur in first cycle T in Fig. 2 is large ripple, and what occur in second period T is small echo.And the small echo in this large small echo, its opening time very short (time that in second period T, K1 is corresponding), reason is its large ripple opening time very long (time that in first cycle T, K1 is corresponding), basic close to or equal the maximum ON time Ton_max of switching tube Q, under the effect that on-Line Voltage compensates, the CS threshold value of its large ripple is also higher, and the CS threshold value in Fig. 2 is exactly the threshold value of former limit inductive current threshold value after line voltage compensation.Due to the discharge time of large ripple very short (time that in first cycle T, K2 is corresponding), therefore the former limit inductor current signal initial value of small echo is very high, substantially CS threshold value is encountered once opening, switching tube Q turns off immediately, total effect is equivalent to two cycles and just opens once, and the time of opening is only maximum ON time Ton_max, thus limit power output.
Thus prior art need to improve.
Utility model content
In view of above-mentioned the deficiencies in the prior art part, the purpose of this utility model is to provide a kind of Switching Power Supply control chip and inverse-excitation type AC-DC converter, prevents output overcurrent point and recovery point under low pressure from increasing with line voltage and increasing, improves power output.
In order to achieve the above object, the utility model takes following technical scheme:
A kind of Switching Power Supply control chip, comprises oscillator or door and rest-set flip-flop, also comprises:
For sampling to former limit inductive current and exporting the sampling unit of sampled signal CS1;
The slope compensation unit of the ramp signal of 1/2nd former limit inductive current descending slopes is greater than for superposing a rate of rise on sampled signal CS1;
For carrying out line voltage compensation to reference voltage, export the line voltage compensation unit of sampled signal threshold voltage;
For the signal that FB end and the slope compensation unit of more described Switching Power Supply control chip export, according to the PWM comparator unit of comparative result output pwm signal;
For doing the Cycle by Cycle current-limiting protection unit of Cycle by Cycle current-limiting protection to former limit inductive current peak;
For driving the driver element of external power metal-oxide-semiconductor;
For detecting the ON time of external power metal-oxide-semiconductor, when described ON time is greater than the first Preset Time, in the ON time of next external power metal-oxide-semiconductor, control line voltage compensation unit does not carry out line voltage compensation to reference voltage, reference voltage is carried out to the line voltage compensation control module of line voltage compensation after the second Preset Time in the second Preset Time;
The input of described sampling unit is the CS end of Switching Power Supply control chip, and the output of described sampling unit connects the input of slope compensation unit and the first input end of Cycle by Cycle current-limiting protection unit, the input of described line voltage compensation control module connects the output of driver element, the output connecting line voltage compensation unit of described line voltage compensation control module, the input input reference voltage of described line voltage compensation unit, the output of described line voltage compensation unit connects the second input of Cycle by Cycle current-limiting protection unit, the output of described slope compensation unit connects the first input end of PWM comparator unit, second input of described PWM comparator unit is the FB end of Switching Power Supply control chip, the output connection of described PWM comparator unit or the first input end of door, the output connection of described Cycle by Cycle current-limiting protection unit or the second input of door, output that is described or door connects the R end of rest-set flip-flop, described oscillator connects the S end of rest-set flip-flop, the Q end of described rest-set flip-flop connects the input of driver element, the output of described driver element is the OUT end of described Switching Power Supply control chip, connect the grid level of external power metal-oxide-semiconductor.
Described Switching Power Supply control chip, wherein, described line voltage compensation control module comprises:
For detecting the ON time of external power metal-oxide-semiconductor, when described ON time is greater than the first Preset Time, open the ON time detecting unit of timing unit;
For after unlatching, receive the Continuity signal of next external power metal-oxide-semiconductor, control switch unit makes line voltage compensation unit not carry out line voltage compensation to reference voltage and start timing, after the ON time of outside power MOS pipe is more than the second Preset Time, control switch unit makes line voltage compensation unit carry out the timing unit of line voltage compensation to reference voltage;
For control line voltage compensation unit, reference voltage is carried out to the switch element of line voltage compensation.
Described Switching Power Supply control chip, wherein, described timing unit comprises timer.
Described Switching Power Supply control chip, wherein, described switch element comprises analog switch, the input of one end connecting line voltage compensation unit of described analog switch, the output of the other end connecting line voltage compensation unit of described analog switch, the control end of described analog switch is connected with the output of timing unit.
Described Switching Power Supply control chip, wherein, described PWM comparator unit comprises PWM comparator, the normal phase input end of described PWM comparator connects the output of slope compensation unit, the inverting input of described PWM comparator is the FB end of Switching Power Supply control chip, the output connection of described PWM comparator or the first input end of door.
A kind of inverse-excitation type AC-DC converter, wherein, comprises Switching Power Supply control chip as above.
Described inverse-excitation type AC-DC converter, wherein, described inverse-excitation type AC-DC converter also comprises the first diode, the second diode, the first electric capacity, the second electric capacity, transformer, power MOS pipe, operational amplifier, optocoupler, the first resistance, the second resistance, the 3rd resistance and the 4th resistance; Described transformer comprises former limit winding, auxiliary winding and vice-side winding; One end of described former limit winding is the voltage input end of inverse-excitation type AC-DC converter, the input voltage of the outside input of reception, the other end of described former limit winding connects the drain electrode of power MOS pipe, the grid level of described power MOS pipe connects the OUT end of Switching Power Supply control chip, and the CS of the source electrode connecting valve power supply control chip of described power MOS pipe holds, also by the first grounding through resistance; Described auxiliary winding is responded to former limit winding and is connected, one end ground connection of described auxiliary winding, the other end of described auxiliary winding connects the positive pole of the first diode, and the Vcc of the negative pole connecting valve power supply control chip of described first diode holds, also by the first capacity earth; Described vice-side winding is responded to former limit winding and is connected, one end of described vice-side winding connects the positive pole of the second diode, the negative pole of described second diode be inverse-excitation type AC-DC converter the first output, connect one end of one end of the second electric capacity, one end of the second resistance and the 3rd resistance, the other end of described vice-side winding is the second output of inverse-excitation type AC-DC converter, the other end connecting the second electric capacity; The other end of described second resistance connects the first end of opto-coupler chip, the ref of the other end concatenation operation amplifier of described 3rd resistance holds, also by the anode of the 4th resistance concatenation operation amplifier, the negative electrode of described operational amplifier connects the second end of opto-coupler chip, 3rd end ground connection of described opto-coupler chip, the FB end of the 4th end connecting valve power supply control chip of described opto-coupler chip, the GND of described Switching Power Supply control chip holds ground connection.
Described inverse-excitation type AC-DC converter, wherein, described power MOS pipe is NMOS tube.
Compared to prior art, the Switching Power Supply control chip that the utility model provides, by line voltage compensation control module, detect the ON time of external power metal-oxide-semiconductor, when described ON time is greater than the first Preset Time, in the ON time of next external power metal-oxide-semiconductor, control line voltage compensation unit, line voltage compensation unit is made not carry out line voltage compensation to reference voltage in the second Preset Time, thus output overcurrent point and recovery point increase with line voltage and increase under preventing low pressure, make in each cycle, the ON time of external power metal-oxide-semiconductor is all longer, improve power output.
Accompanying drawing explanation
Fig. 1 is the circuit diagram of existing inverse-excitation type AC-DC converter.
Fig. 2 is the oscillogram of limit, existing inverse-excitation type AC-DC converter Central Plains inductive current.
The structured flowchart of the Switching Power Supply control chip that Fig. 3 provides for the utility model.
The circuit diagram of the inverse-excitation type AC-DC converter that Fig. 4 provides for the utility model.
The oscillogram of sampled signal CS1 in the inverse-excitation type AC-DC converter that Fig. 5 provides for the utility model.
Embodiment
The utility model provides a kind of Switching Power Supply control chip and inverse-excitation type AC-DC converter, the ON time being detected external power metal-oxide-semiconductor by line voltage compensation control module judges whether to do line voltage compensation at next cycle to former limit inductive current, prevent output overcurrent point and recovery point under low pressure from increasing with line voltage and increasing, improve power output.
For making the purpose of this utility model, technical scheme and effect clearly, clearly, referring to the accompanying drawing embodiment that develops simultaneously, the utility model is further described.Should be appreciated that specific embodiment described herein only in order to explain the utility model, and be not used in restriction the utility model.
Refer to Fig. 3; the Switching Power Supply control chip that the utility model provides, comprises sampling unit 10, slope compensation unit 20, PWM comparator unit 30, line voltage compensation control module 40, line voltage compensation unit 50, Cycle by Cycle current-limiting protection unit 60 or door U2, rest-set flip-flop U3, oscillator U4 and driver element 70.Described oscillator U4 each cycle is to external power metal-oxide-semiconductor start signal.
Sampling unit 10 is sampled to former limit inductive current and sampled signal is exported to slope compensation unit 20 and Cycle by Cycle current-limiting protection unit 60; Slope compensation unit 20 superposes the ramp signal that a rate of rise is greater than 1/2nd former limit inductive current descending slopes and exports to PWM comparator unit 30 in sampled signal; PWM comparator unit 30 compares the signal that the FB end of Switching Power Supply control chip and slope compensation unit 20 export, according to comparative result output pwm signal to or the first input end 1 of door U2 "; Line voltage compensation control module 40 detects the ON time of external power metal-oxide-semiconductor, when described ON time is greater than the first preset time T 1, in the ON time of next external power metal-oxide-semiconductor, control line voltage compensation unit 50 does not carry out line voltage compensation to reference voltage V ref, after the second preset time T 2, carries out line voltage compensation to reference voltage V ref in the second preset time T 2; The sampled signal threshold voltage that Cycle by Cycle current-limiting protection unit 60 exports according to line voltage compensation unit 50, does Cycle by Cycle current-limiting protection to sampled signal and exports to or second input 2 of door U2 "; Or door U2 is according to first input end 1 " and the second input 2 " signal that inputs, export cut-off signals to hold to the R of rest-set flip-flop U3, oscillator U4 exports start signal and holds to the S of rest-set flip-flop U3, and the Q end of rest-set flip-flop U3 controls the turn-on and turn-off of external power metal-oxide-semiconductor by driver element 70.
In other words, described sampling unit 10, for sampling to former limit inductive current and export sampled signal CS1.
Described slope compensation unit 20, is greater than the ramp signal of 1/2nd former limit inductive current descending slopes for superposing a rate of rise on sampled signal CS1.
Described line voltage compensation unit 50, for carrying out line voltage compensation to reference voltage V ref, exports sampled signal threshold voltage.Concrete, described line voltage compensation unit 50, for the ON time according to external power metal-oxide-semiconductor, the bucking voltage that superposition one is negative on reference voltage V ref, namely reduces reference voltage V ref, and the reference voltage V ref that will reduce exports.The ON time of external power metal-oxide-semiconductor is shorter, compensates larger; ON time is longer, compensates less.
Described PWM comparator unit 30, the signal that FB end and slope compensation unit 20 for more described Switching Power Supply control chip export, according to comparative result output pwm signal.Wherein, described PWM comparator unit 30 comprises PWM comparator, the normal phase input end of described PWM comparator connects the output of slope compensation unit 20, the inverting input of described PWM comparator is the FB end of Switching Power Supply control chip, the output connection of described PWM comparator or the first input end 1 of door U2 ".
Described Cycle by Cycle current-limiting protection unit 60, for doing Cycle by Cycle current-limiting protection to former limit inductive current peak.Specifically for, when voltage (sampled signal threshold voltage or reference voltage V ref) that the voltage (sampled signal CS1) of first input end input inputs higher than the second input, export high level; When the voltage that the voltage of first input end input inputs lower than the second input, output low level.
Described driver element 70, for driving external power metal-oxide-semiconductor.
Line voltage compensation control module 40, for detecting the ON time of external power metal-oxide-semiconductor, when described ON time is greater than the first preset time T 1, in the ON time of next external power metal-oxide-semiconductor, control line voltage compensation unit does not carry out line voltage compensation to reference voltage V ref, after the second preset time T 2, carries out line voltage compensation to reference voltage V ref in the second preset time T 2.Specifically for, in the one-period of outside power MOS pipe conducting and closedown, detect the ON time of external power metal-oxide-semiconductor, when described ON time is greater than the first preset time T 1, come then at next cycle, control line voltage compensation unit 50 does not carry out line voltage compensation to reference voltage V ref, after the second preset time T 2, carries out line voltage compensation again to reference voltage V ref in the second preset time T 2.
The application parameter that described first preset time T 1 is concrete according to Switching Power Supply control chip is determined, but described first preset time T 1 can not exceed the maximum ON time of external power metal-oxide-semiconductor.Described second preset time T 2 is set, in order to the time enough that discharges to inductive current, prevent next switch periods higher, and lower under sampled signal on-Line Voltage compensating signal due to inductive current, thus occur that this Cyclical power metal-oxide-semiconductor opening time is too short.Therefore, the same application parameter concrete according to Switching Power Supply control chip of described second preset time T 2 is determined.
The input of described sampling unit 10 is the CS end of Switching Power Supply control chip, and the output of described sampling unit 10 connects the input of slope compensation unit 20 and the first input end 1 of Cycle by Cycle current-limiting protection unit 60, the input of described line voltage compensation control module 40 connects the output of driver element 70, the output connecting line voltage compensation unit 50 of described line voltage compensation control module 40, the input input reference voltage of described line voltage compensation unit 50, the output of described line voltage compensation unit 50 connects the second input 2 of Cycle by Cycle current-limiting protection unit 60, the output of described slope compensation unit 20 connects the first input end 1 ' of PWM comparator unit, the FB that second input 2 ' of described PWM comparator unit 30 is Switching Power Supply control chip holds, the output connection of described PWM comparator unit 30 or the first input end 1 of door U2 ", the output connection of described Cycle by Cycle current-limiting protection unit 60 or second input 2 of door U2 ", output that is described or door U2 connects the R end of rest-set flip-flop U3, described oscillator U4 connects the S end of rest-set flip-flop U3, the Q end of described rest-set flip-flop U3 connects the input of driver element 70, the output of described driver element 70 is the OUT end of described Switching Power Supply control chip, connect the grid level of external power metal-oxide-semiconductor.The CS end of described Switching Power Supply control chip connects the source electrode of external power metal-oxide-semiconductor usually, and the FB end of described Switching Power Supply control chip connects the feedback end of external loading usually, and namely the input of FB end is feedback signal.
Seeing also Fig. 4, for ease of setting forth the principle of Switching Power Supply control chip, Switching Power Supply control chip U5 of the present utility model being joined in conventional inverse-excitation type AC-DC converter circuit.
Can be proved by mathematical derivation, if superpose the ramp signal that a rate of rise is greater than former limit inductive current descending slope half on the actual former limit inductive current waveform detected, the perturbation action of different duty to average former limit inductive current size can be removed, make controlled peak inductive current finally converge on average inductor current.So former limit inductive current (CS holds input signal) is converted into sampled signal CS1 by sampling unit 10, sampled signal CS1 exports a signal CS2 by slope compensation unit 20, first input end 1 ', the PWM comparator unit 30 that CS2 is sent to PWM comparator unit 30 exports a pwm signal.When the feedback voltage that CS2 signal inputs higher than FB end, described pwm signal is high level, otherwise pwm signal is low level.In order to protect external power pipe metal-oxide-semiconductor, Cycle by Cycle current-limiting protection is done to former limit inductive current peak, so sampled signal CS1 is sent to the first input end 1 of Cycle by Cycle current-limiting protection unit 60.When in order to make former limit input voltage VIN different; former limit inductive current peak has better consistency; so carry out line voltage compensation to inner reference voltage V ref; namely; a sampled signal threshold voltage is produced by line voltage compensation unit 50; then sampled signal threshold voltage is sent to the second input 2 of Cycle by Cycle current-limiting protection unit 60, and then Cycle by Cycle current-limiting protection unit 60 exports a signal OCP.When sampled signal CS1 is higher than sampled signal threshold voltage, then OCP signal is high level, otherwise is low level.Final pwm signal and OCP signal by or door U2 export a cut-off signals (high level).Oscillator U4 export start signal and or door U2 export cut-off signals be connected respectively to rest-set flip-flop U3 S end and R end, the output of described rest-set flip-flop U3 and Q end be connected to drive list 70 input.
Under normal circumstances, loop controls to be produce start signal by oscillator U4, and PWM comparator unit 30 is passed through or door U2 exports cut-off signals.When output voltage VO is on the low side or load is very heavy, the voltage of the FB end input of described Switching Power Supply control chip U5 is high, the corresponding duty ratio increasing output signal of Switching Power Supply control chip U5, the energy that each cycle is transmitted increases, thus makes output voltage VO be elevated to set point gradually.When output voltage VO is higher or load is very light, the voltage drop of the FB end of described Switching Power Supply control chip U5, the corresponding duty ratio reducing output signal of described Switching Power Supply control chip U5, makes output voltage VO reduce gradually and gets back to set point.When output load current reached flow point; FB end is very high by what draw; now cut-off signals mainly Cycle by Cycle current-limiting protection unit 60 export OCP signal controlling; in such cases; if continue, line voltage compensation is carried out to reference voltage V ref; then loop controls to lose efficacy, and so talks about, and just may there will be output loading and cross flow point and recovery point and increase with line electricity and increase.Due to the existence of wired voltage compensation module 40, when external power pipe metal-oxide-semiconductor conducting (opening), line voltage compensation control module detects the ON time Ton of external power metal-oxide-semiconductor within this cycle, when Ton> the first preset time T 1, think that input voltage VIN is very low, when next cycle, described line voltage compensation control module 40 control line voltage compensation unit 50 does not carry out line voltage compensation to reference voltage V ref, now, reference voltage V ref is directly inputted in the second input 2 of Cycle by Cycle current-limiting protection unit 60, conveniently, be CS threshold voltage (sampled signal threshold voltage or reference voltage V ref) by the signal definition that the second input 2 of Cycle by Cycle current-limiting protection unit 60 inputs, when ON time Ton> second preset time T 2 of external power metal-oxide-semiconductor, described line voltage compensation control module 40 control line voltage compensation unit 50 couples of reference voltage V ref carry out line voltage compensation, and namely described line voltage compensation unit 50 continues to export sampled signal threshold voltage to Cycle by Cycle current-limiting protection unit 60.Doing so avoids when input voltage VIN is very low, external power metal-oxide-semiconductor opening time Ton is oversize or close under maximum ON time Ton_max, cause because CS threshold voltage is too low drive singal immediately to turn off when external power metal-oxide-semiconductor is opened again, bio-occlusion load can not export energy.
The oscillogram of the sampled signal CS1 of the Switching Power Supply control chip that Fig. 5 provides for the utility model, due to sampled signal CS1 corresponding be former limit inductive current, therefore Fig. 5 can reflect the situation of change of former limit inductive current in each switch periods.In one-period, external power metal-oxide-semiconductor is opened, the conducting of former limit, the magnitude of voltage of sampled signal CS1 rises (the K1 section in first cycle T), the opening time Ton1 of external power metal-oxide-semiconductor in one-period is greater than the first preset time T 1, and when the magnitude of voltage of sampled signal CS1 is more than CS threshold voltage, external power metal-oxide-semiconductor turns off, the magnitude of voltage of sampled signal CS1 declines (the K2 section in first cycle T)
Drop to oscillator when again exporting a start signal, external power metal-oxide-semiconductor is opened.Enter into second period, owing to not carrying out line voltage compensation to reference voltage V ref in the second preset time T 2 of second period, therefore, in the second preset time T 2, the magnitude of voltage of sampled signal CS1 is no more than reference voltage V ref, and external power metal-oxide-semiconductor would not turn off; Therefore in second period, the opening time Ton2 of external power metal-oxide-semiconductor is still longer, visible, when former limit input voltage VIN is very low, the Switching Power Supply control chip that the utility model provides still can export energy to load continuous by control switch circuit, improves efficiency.
Refer to Fig. 3, in the Switching Power Supply control chip that the utility model provides, described line voltage compensation control module comprises ON time detecting unit 410, timing unit 420 and switch element 430.
Described ON time detecting unit 410, for detecting the ON time of external power metal-oxide-semiconductor, when described ON time is greater than the first Preset Time, opens timing unit 420.
Described timing unit 420, for after unlatching, receive the Continuity signal of next external power metal-oxide-semiconductor, control switch unit makes line voltage compensation unit not carry out line voltage compensation to reference voltage V ref and start timing, after the ON time of outside power MOS pipe is more than the second Preset Time, control switch unit 430 makes line voltage compensation unit 50 couples of reference voltage V ref carry out line voltage compensation.Concrete, described timing unit 420, after the Continuity signal receiving external power metal-oxide-semiconductor, exports an enable signal and makes switch element 430 close and start timing, after the second Preset Time, exports another enable signal and switch element 430 is disconnected.Preferably, described timing unit 420 comprises timer.
Described switch element 430, carries out line voltage compensation for control line voltage compensation unit 50 couples of reference voltage V ref.Concrete, described switch element 430 is connected in parallel on input and the output of line voltage compensation unit 50, and described switch element 430, by carrying out short circuit to line voltage compensation unit 50, makes line voltage compensation unit 50 not carry out line voltage compensation to reference voltage V ref.Preferably, described switch element 430 comprises analog switch K, the input of one end connecting line voltage compensation unit 50 of described analog switch K, the output of the other end connecting line voltage compensation unit 50 of described analog switch K, the control end of described analog switch K is connected with the output of timing unit 420.Namely; described timing unit 420 only needs output enable signal analog switch K is closed or disconnects; the line voltage compensation to reference voltage can be controlled, thus sampled signal threshold voltage or reference voltage V ref can be allowed to be input to the second input of Cycle by Cycle current-limiting protection unit 60.
The first input end a of described ON time detecting unit 410 is the input of line voltage compensation control module 40, the output of connection driver element 70, second input b of described ON time detecting unit 410 inputs the second Preset Time signal, the output of described ON time detecting unit 410 connects the Enable Pin of timing unit 420, the signal input part of described timing unit 420 connects the output of driver element 70, the output connecting valve unit 430 of described timing unit 420.
When the drive singal PWM1 that driver element 70 exports is high, external power metal-oxide-semiconductor is opened, ON time detecting unit 410 detects this cycle inside and outside power MOS pipe ON time Ton, when Ton> first preset time T 1(thinks that VIN is very low) time, ON time detecting unit 410 exports an enable signal Tonp to timing unit 420, and Tonp is effectively high.And then when the next drive singal PWM2 exported when driver element 70 is high, timing unit 420 exports an enable signal makes K switch close, namely CS threshold voltage through line voltage compensation unit 50, sampled signal CS1 directly and reference voltage V ref compare.Timing unit 420 starts timing simultaneously, when external power metal-oxide-semiconductor ON time Ton> the second preset time T 2, timing unit 420 can export an enable signal makes K switch open, and namely after ON time Ton>T2, CS threshold voltage continues to be produced through line voltage compensation unit 50 by reference voltage V ref.Doing so avoids when input voltage VIN is very low, the power MOS pipe opening time is oversize or close under maximum ON time, causes drive singal immediately to turn off when power MOS pipe is opened again because CS threshold value is too low, bio-occlusion load can not export energy.
Refer to Fig. 4, the utility model also provides a kind of inverse-excitation type AC-DC converter, comprise the Switching Power Supply control chip U5 as above described in an embodiment, also comprise the first diode D1, the second diode D2, the first electric capacity C1, the second electric capacity C2, transformer 80, power MOS pipe Q1, operational amplifier Q2, optocoupler U6, the first resistance R1, the second resistance R2, the 3rd resistance R3 and the 4th resistance R4.
Described transformer 80 comprises former limit winding Np, auxiliary winding Na and vice-side winding Ns.One end of described former limit winding Np is the voltage input end of inverse-excitation type AC-DC converter, the input voltage VIN of the outside input of reception, the other end of described former limit winding Np connects the drain electrode of power MOS pipe Q1, the grid level of described power MOS pipe Q1 connects the OUT end of Switching Power Supply control chip U5, and the CS of the source electrode connecting valve power supply control chip U5 of described power MOS pipe Q1 holds, also by the first resistance R1 ground connection; Described auxiliary winding Na responds to former limit winding Np and is connected, one end ground connection of described auxiliary winding Na, the other end of described auxiliary winding Na connects the positive pole of the first diode D1, and the Vcc of the negative pole connecting valve power supply control chip U5 of described first diode D1 holds, also by the first electric capacity C1 ground connection; Described vice-side winding Ns responds to former limit winding Np and is connected, one end of described vice-side winding Ns connects the positive pole of the second diode D2, the negative pole of described second diode D2 be inverse-excitation type AC-DC converter the first output, connect one end of one end of the second electric capacity C2, one end of the second resistance R2 and the 3rd resistance R3, the other end of described vice-side winding Ns is the second output of inverse-excitation type AC-DC converter, connects the other end of the second electric capacity C2; The other end of described second resistance R2 connects the first end c of opto-coupler chip U6, the ref of the other end concatenation operation amplifier Q2 of described 3rd resistance R3 holds, also by the anode of the 4th resistance R4 concatenation operation amplifier Q2, the negative electrode of described operational amplifier Q2 connects the second end d of opto-coupler chip U6, the 3rd end e ground connection of described opto-coupler chip U6, the FB end of the 4th end f connecting valve power supply control chip U5 of described opto-coupler chip U6, the GND of described Switching Power Supply control chip U5 holds ground connection.
The model of described operational amplifier Q2 is TL431, there are three pins, be respectively negative electrode, anode and ref end, wherein, the anode of operational amplifier Q2 is connected with the negative terminal exporting Vo, and ref end is the positive input of operational amplifier, and the reverse input end of operational amplifier is built-in, outside does not have pin, does not draw.Described power MOS pipe Q1 is NMOS tube.Load is connected between first output of described inverse-excitation type AC-DC converter and the second output, described Switching Power Supply control chip U5 according to the change of load (i.e. output end voltage Vo), by the duty ratio of regulating power metal-oxide-semiconductor Q1 conducting to the direct voltage of load stable output.
Because the operation principle of described inverse-excitation type AC-DC converter and feature elaborate in a upper embodiment, do not repeat them here.
Be understandable that; for those of ordinary skills; can be equal to according to the technical solution of the utility model and utility model design thereof and replace or change, and all these change or replace the protection range that all should belong to the claim appended by the utility model.
Claims (8)
1. a Switching Power Supply control chip, comprises oscillator or door and rest-set flip-flop, it is characterized in that, also comprise:
For sampling to former limit inductive current and exporting the sampling unit of sampled signal CS1;
The slope compensation unit of the ramp signal of 1/2nd former limit inductive current descending slopes is greater than for superposing a rate of rise on sampled signal CS1;
For carrying out line voltage compensation to reference voltage, export the line voltage compensation unit of sampled signal threshold voltage;
For the signal that FB end and the slope compensation unit of more described Switching Power Supply control chip export, according to the PWM comparator unit of comparative result output pwm signal;
For doing the Cycle by Cycle current-limiting protection unit of Cycle by Cycle current-limiting protection to former limit inductive current peak;
For driving the driver element of external power metal-oxide-semiconductor;
For detecting the ON time of external power metal-oxide-semiconductor, when described ON time is greater than the first Preset Time, in the ON time of next external power metal-oxide-semiconductor, control line voltage compensation unit does not carry out line voltage compensation to reference voltage, reference voltage is carried out to the line voltage compensation control module of line voltage compensation after the second Preset Time in the second Preset Time;
The input of described sampling unit is the CS end of Switching Power Supply control chip, and the output of described sampling unit connects the input of slope compensation unit and the first input end of Cycle by Cycle current-limiting protection unit, the input of described line voltage compensation control module connects the output of driver element, the output connecting line voltage compensation unit of described line voltage compensation control module, the input input reference voltage of described line voltage compensation unit, the output of described line voltage compensation unit connects the second input of Cycle by Cycle current-limiting protection unit, the output of described slope compensation unit connects the first input end of PWM comparator unit, second input of described PWM comparator unit is the FB end of Switching Power Supply control chip, the output connection of described PWM comparator unit or the first input end of door, the output connection of described Cycle by Cycle current-limiting protection unit or the second input of door, output that is described or door connects the R end of rest-set flip-flop, described oscillator connects the S end of rest-set flip-flop, the Q end of described rest-set flip-flop connects the input of driver element, the output of described driver element is the OUT end of described Switching Power Supply control chip, connect the grid level of external power metal-oxide-semiconductor.
2. Switching Power Supply control chip according to claim 1, is characterized in that, described line voltage compensation control module comprises:
For detecting the ON time of external power metal-oxide-semiconductor, when described ON time is greater than the first Preset Time, open the ON time detecting unit of timing unit;
For after unlatching, receive the Continuity signal of next external power metal-oxide-semiconductor, control switch unit makes line voltage compensation unit not carry out line voltage compensation to reference voltage and start timing, after the ON time of outside power MOS pipe is more than the second Preset Time, control switch unit makes line voltage compensation unit carry out the timing unit of line voltage compensation to reference voltage;
For control line voltage compensation unit, reference voltage is carried out to the switch element of line voltage compensation.
3. Switching Power Supply control chip according to claim 2, is characterized in that, described timing unit comprises timer.
4. Switching Power Supply control chip according to claim 3, it is characterized in that, described switch element comprises analog switch, the input of one end connecting line voltage compensation unit of described analog switch, the output of the other end connecting line voltage compensation unit of described analog switch, the control end of described analog switch is connected with the output of timing unit.
5. Switching Power Supply control chip according to claim 4, it is characterized in that, described PWM comparator unit comprises PWM comparator, the normal phase input end of described PWM comparator connects the output of slope compensation unit, the inverting input of described PWM comparator is the FB end of Switching Power Supply control chip, the output connection of described PWM comparator or the first input end of door.
6. an inverse-excitation type AC-DC converter, is characterized in that, comprise as arbitrary in claim 1-5 as described in Switching Power Supply control chip.
7. inverse-excitation type AC-DC converter according to claim 6, it is characterized in that, described inverse-excitation type AC-DC converter also comprises the first diode, the second diode, the first electric capacity, the second electric capacity, transformer, power MOS pipe, operational amplifier, optocoupler, the first resistance, the second resistance, the 3rd resistance and the 4th resistance; Described transformer comprises former limit winding, auxiliary winding and vice-side winding; One end of described former limit winding is the voltage input end of inverse-excitation type AC-DC converter, the input voltage of the outside input of reception, the other end of described former limit winding connects the drain electrode of power MOS pipe, the grid level of described power MOS pipe connects the OUT end of Switching Power Supply control chip, and the CS of the source electrode connecting valve power supply control chip of described power MOS pipe holds, also by the first grounding through resistance; Described auxiliary winding is responded to former limit winding and is connected, one end ground connection of described auxiliary winding, the other end of described auxiliary winding connects the positive pole of the first diode, and the Vcc of the negative pole connecting valve power supply control chip of described first diode holds, also by the first capacity earth; Described vice-side winding is responded to former limit winding and is connected, one end of described vice-side winding connects the positive pole of the second diode, the negative pole of described second diode be inverse-excitation type AC-DC converter the first output, connect one end of one end of the second electric capacity, one end of the second resistance and the 3rd resistance, the other end of described vice-side winding is the second output of inverse-excitation type AC-DC converter, the other end connecting the second electric capacity; Described in the first end of the other end connection opto-coupler chip of described second resistance, the ref of the other end concatenation operation amplifier of the 3rd resistance holds, also by the anode of the 4th resistance concatenation operation amplifier, the negative electrode of described operational amplifier connects the second end of opto-coupler chip, 3rd end ground connection of described opto-coupler chip, the FB end of the 4th end connecting valve power supply control chip of described opto-coupler chip, the GND of described Switching Power Supply control chip holds ground connection.
8. inverse-excitation type AC-DC converter according to claim 7, is characterized in that, described power MOS pipe is NMOS tube.
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| CN201520282962.0U CN204559393U (en) | 2015-05-05 | 2015-05-05 | A kind of Switching Power Supply control chip and inverse-excitation type AC-DC converter |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109039113A (en) * | 2018-07-18 | 2018-12-18 | 深圳市稳先微电子有限公司 | A kind of Switching Power Supply and its control chip |
| CN109039093A (en) * | 2018-09-29 | 2018-12-18 | 杰华特微电子（杭州）有限公司 | Isolation type switching power supply and its control method |
-
2015
- 2015-05-05 CN CN201520282962.0U patent/CN204559393U/en active Active
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109039113A (en) * | 2018-07-18 | 2018-12-18 | 深圳市稳先微电子有限公司 | A kind of Switching Power Supply and its control chip |
| CN109039093A (en) * | 2018-09-29 | 2018-12-18 | 杰华特微电子（杭州）有限公司 | Isolation type switching power supply and its control method |
| CN109039093B (en) * | 2018-09-29 | 2024-01-23 | 杰华特微电子股份有限公司 | Isolation type switching power supply and control method thereof |
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