CN105006966B - A kind of Switching Power Supply control chip and inverse-excitation type AC DC converters - Google Patents
A kind of Switching Power Supply control chip and inverse-excitation type AC DC converters Download PDFInfo
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- CN105006966B CN105006966B CN201510222875.0A CN201510222875A CN105006966B CN 105006966 B CN105006966 B CN 105006966B CN 201510222875 A CN201510222875 A CN 201510222875A CN 105006966 B CN105006966 B CN 105006966B
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Abstract
The invention discloses a kind of Switching Power Supply control chip and inverse-excitation type AC DC converters, the Switching Power Supply control chip includes sampling unit, slope compensation unit, PWM comparator units, line voltage compensation control module, line voltage compensation unit, Cycle by Cycle current-limiting protection unit, OR gate, rest-set flip-flop, oscillator and driver element.The Switching Power Supply control chip that the present invention is provided, pass through line voltage compensation control module, detect the ON time of external power metal-oxide-semiconductor, when the ON time is more than the first preset time, in the ON time of next external power metal-oxide-semiconductor, control line voltage compensation unit, make line voltage compensation unit in the second preset time to reference voltage without line voltage compensation；So as to prevent output overcurrent point and recovery point under low pressure to increase with line voltage and increase.Make in each cycle, the ON time of external power metal-oxide-semiconductor is longer, improves power output.
Description
Technical field
The present invention relates to switch power technology field, more particularly to 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 was not reaching to flow point,
The cut-off signals of control chip U1 OUT terminal are by feedback voltage（From the input of FB ends）With primary current detection signal（From CS ends
Input）Control.When output loading reached flow point very much greatly, it is very high that the voltage at control chip U1 FB ends becomes, and now controls
The cut-off signals of chip U1 OUT terminal output are determined by the peak value of primary side inductive current.Due to control chip U1 OUT
There is certain turn-off delay Tdelay in the drive signal of end output, so under different input voltage vins, primary side inductance electricity
Stream peak value can after drive signal shut-off one △ Ipk of superposition=, Lp is primary side inductance.In 85VAC-264VAC voltage model
In enclosing, in order that output overcurrent point/recovery point has uniformity, line voltage compensation has been done to primary side inductive current threshold value.But
Under specific application（Under transformer parameter）, when low pressure is inputted, easily there is big small echo in primary side inductor current signal, referring to figure
2.Occurred that in Fig. 2 in first cycle T in big ripple, second period T and occur that small echo.And it is small in the big small echo
Ripple, its opening time is very short（The K1 corresponding times in second period T）, reason is that its big ripple opening time is very long（First
The K1 corresponding times in individual cycle T）, substantially close to or equal to the maximum ON time Ton_max of switching tube Q, on-Line Voltage compensation
In the presence of, the CS threshold values of its big ripple are also higher, and the CS threshold values in Fig. 2 are exactly that primary side inductive current threshold value is mended by line voltage
Threshold value after repaying.Because the discharge time of big ripple is very short（The K2 corresponding times in first cycle T）, therefore the primary side electricity of small echo
Inducing current signal initial value is very high, substantially encounters CS threshold values once opening, switching tube Q is immediately turned off, total effect equivalent to
Two cycles just open once, and the time opened is only maximum ON time Ton_max, so as to limit power output.
Thus prior art could be improved and improve.
The content of the invention
In view of in place of above-mentioned the deficiencies in the prior art, it is an object of the invention to provide a kind of Switching Power Supply control chip and
Inverse-excitation type AC-DC converter, prevents that output overcurrent point and recovery point increase and increased with line voltage under low pressure, improve output work
Rate.
In order to achieve the above object, this invention takes following technical scheme：
A kind of Switching Power Supply control chip, including oscillator, OR gate, rest-set flip-flop, sampling unit, slope compensation unit,
Line voltage compensation unit, PWM comparator units, Cycle by Cycle current-limiting protection unit, driver element and line voltage compensation control module；
Sampling unit is sampled to primary side inductive current and is exported sampled signal to slope compensation unit and Cycle by Cycle
Current-limiting protection unit；Slope compensation unit is superimposed a rate of rise more than under 1/2nd primary side inductive currents in sampled signal
The ramp signal of drop angle rate, which is exported, gives PWM comparator units；PWM comparator units compare Switching Power Supply control chip FB ends and
The signal of slope compensation unit output, the first input end according to comparative result output pwm signal to OR gate；Line voltage compensation control
Molding block detects the ON time of external power metal-oxide-semiconductor, when the ON time is more than the first preset time, next outer
In the ON time of portion's power MOS pipe, control line voltage compensation unit is in the second preset time to reference voltage without line
Voltage compensation, after the second preset time to reference voltage carry out line voltage compensation；Cycle by Cycle current-limiting protection unit is according to line electricity
Press compensating unit output sampled signal threshold voltage, sampled signal is done Cycle by Cycle current-limiting protection and export to OR gate second
Input；The signal that OR gate is inputted according to first input end and the second input, exports R end of the cut-off signals to rest-set flip-flop,
Oscillator exports S end of the open signal to rest-set flip-flop, and the Q ends of rest-set flip-flop control external power MOS by driver element
The turn-on and turn-off of pipe.
Described Switching Power Supply control chip, wherein, the line voltage compensation control module includes ON time and detects single
Member, timing unit and switch element；
The ON time detection unit, the ON time for detecting external power metal-oxide-semiconductor is big in the ON time
When the first preset time, timing unit is opened；
The timing unit, Continuity signal, controlling switch for after unlatching, receiving next external power metal-oxide-semiconductor
Unit makes line voltage compensation unit to reference voltage without line voltage compensation and starts timing, in leading for outside power MOS pipe
After the logical time is more than the second preset time, controlling switch unit makes line voltage compensation unit enter row line voltage benefit to reference voltage
Repay；
The switch element, line voltage compensation is carried out for control line voltage compensation unit to reference voltage.
Described Switching Power Supply control chip, wherein, the timing unit includes timer.
Described Switching Power Supply control chip, wherein, the switch element includes analog switch, the one of the analog switch
The input of end connecting line voltage compensation unit, the output end of the other end connecting line voltage compensation unit of the analog switch,
The control end of the analog switch and the output end of timing unit are connected.
Described Switching Power Supply control chip, wherein, the PWM comparator units include PWM comparators, the PWM ratios
Normal phase input end compared with device connects the output end of slope compensation unit, and the inverting input of the PWM comparators is Switching Power Supply
The FB ends of control chip, the output end of the PWM comparators connects the first input end of OR gate.
A kind of inverse-excitation type AC-DC converter, wherein, including Switching Power Supply control chip as described above.
Described inverse-excitation type AC-DC converter, wherein, the inverse-excitation type AC-DC converter also includes the first diode, the
Two diodes, the first electric capacity, the second electric capacity, transformer, power MOS pipe, operational amplifier, optocoupler, first resistor, the second electricity
Resistance, 3rd resistor and the 4th resistance；The transformer includes primary side winding, assists winding and vice-side winding；The primary side winding
One end for inverse-excitation type AC-DC converter voltage input end, receive outside input input voltage, the primary side winding it is another
One end connects the drain electrode of power MOS pipe, the OUT terminal of the grid level connection Switching Power Supply control chip of the power MOS pipe, the work(
The CS ends of the source electrode connecting valve power supply control chip of rate metal-oxide-semiconductor, also it is grounded by first resistor；The assists winding and primary side
Winding sensing connection, one end ground connection of the assists winding, the other end of the assists winding connects the positive pole of the first diode,
The Vcc ends of the negative pole connecting valve power supply control chip of first diode, also pass through the first capacity earth；The secondary around
Group is connected with primary side winding sensing, and one end of the vice-side winding connects the positive pole of the second diode, second diode
Negative pole is electric for the first output end of inverse-excitation type AC-DC converter, the one end for connecting the second electric capacity, one end of second resistance and the 3rd
One end of resistance, the other end of the vice-side winding is the second output end of inverse-excitation type AC-DC converter, connects the another of the second electric capacity
One end；The other end of the second resistance connects the first end of opto-coupler chip, and the other end concatenation operation of the 3rd resistor is put
The normal phase input end of big device, also by the inverting input of the 4th resistance concatenation operation amplifier, the operational amplifier it is defeated
Go out the second end of end connection opto-coupler chip, the 3rd end ground connection of the opto-coupler chip, the 4th end connection of the opto-coupler chip is opened
Close the FB ends of power supply control chip, the GND ends ground connection of the Switching Power Supply control chip.
Inverse-excitation type AC-DC converter according to claim 7, it is characterised in that the power MOS pipe is NMOS
Pipe.
The Switching Power Supply control chip provided compared to prior art, the present invention, passes through line voltage compensation control module, inspection
The ON time of external power metal-oxide-semiconductor is surveyed, when the ON time is more than the first preset time, in next external power
In the ON time of metal-oxide-semiconductor, control line voltage compensation unit makes line voltage compensation unit in the second preset time to benchmark electricity
Pressure, so as to prevent output overcurrent point and recovery point under low pressure to increase with line voltage and increase, makes each without line voltage compensation
In the individual cycle, the ON time of external power metal-oxide-semiconductor is longer, improves power output.
Brief description of the drawings
Fig. 1 is the circuit diagram of existing inverse-excitation type AC-DC converter.
Fig. 2 is the oscillogram of primary side inductive current in existing inverse-excitation type AC-DC converter.
The structured flowchart for the Switching Power Supply control chip that Fig. 3 provides for the present invention.
The circuit diagram for the inverse-excitation type AC-DC converter that Fig. 4 provides for the present invention.
Sampled signal CS1 oscillogram in the inverse-excitation type AC-DC converter that Fig. 5 provides for the present invention.
Embodiment
The present invention provides a kind of Switching Power Supply control chip and inverse-excitation type AC-DC converter, passes through line voltage compensation control
Module detects the ON time of external power metal-oxide-semiconductor to judge whether to do line voltage benefit to primary side inductive current in next cycle
Repay, prevent that output overcurrent point and recovery point increase and increased with line voltage under low pressure, improve power output.
To make the purpose of the present invention, technical scheme and effect clearer, clear and definite, develop simultaneously embodiment pair referring to the drawings
The present invention is further described.It should be appreciated that specific embodiment described herein is not used to only to explain the present invention
Limit the present invention.
Referring to Fig. 3, the Switching Power Supply control chip that provides of the present invention, including sampling unit 10, slope compensation unit 20,
PWM comparator units 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.Oscillator U4 each cycles are to external power metal-oxide-semiconductor one
Open signal.
Sampling unit 10 primary side inductive current is sampled and by sampled signal export to slope compensation unit 20 and by
Cycle-by-cycle current limiting protection location 60；Slope compensation unit 20 is superimposed a rate of rise more than 1/2nd primary sides electricity in sampled signal
The ramp signal of inducing current descending slope is exported to PWM comparator units 30；PWM comparator units 30 compare Switching Power Supply control
The signal that the FB ends of chip and slope compensation unit 20 are exported, according to comparative result output pwm signal to the first defeated of OR gate U2
Enter end 1 "；Line voltage compensation control module 40 detects the ON time of external power metal-oxide-semiconductor, is more than first in the ON time
During preset time T 1, in the ON time of next external power metal-oxide-semiconductor, control line voltage compensation unit 50 is default second
Line is entered without line voltage compensation, after the second preset time T 2 to reference voltage V ref to reference voltage V ref in time T2
Voltage compensation；The sampled signal threshold voltage that Cycle by Cycle current-limiting protection unit 60 is exported according to line voltage compensation unit 50, to adopting
Sample signal does Cycle by Cycle current-limiting protection and exports the second input 2 " to OR gate U2；OR gate U2 is according to first input end 1 " and
The signal of two inputs 2 " input, exports R end of the cut-off signals to rest-set flip-flop U3, and oscillator U4 exports open signal and touched to RS
Device U3 S ends are sent out, rest-set flip-flop U3 Q ends control the turn-on and turn-off of external power metal-oxide-semiconductor by driver element 70.
In other words, the sampling unit 10, for sampled signal CS1 to be sampled and exported to primary side inductive current.
The slope compensation unit 20, for being superimposed a rate of rise on sampled signal CS1 more than 1/2nd primary sides
The ramp signal of inductive current descending slope.
The line voltage compensation unit 50, for carrying out line voltage compensation to reference voltage V ref, exports sampled signal threshold
Threshold voltage.Specifically, the line voltage compensation unit 50, for the ON time according to external power metal-oxide-semiconductor, in reference voltage
A negative offset voltage is superimposed on Vref, that is, reduces reference voltage V ref, and the reference voltage V ref reduced is exported.Outside
The ON time of portion's power MOS pipe is shorter, compensates bigger；ON time is longer, compensates smaller.
The PWM comparator units 30, FB ends and slope compensation unit for comparing the Switching Power Supply control chip
The signal of 20 outputs, according to comparative result output pwm signal.Wherein, the PWM comparator units 30 include PWM comparators, institute
The output end of the normal phase input end connection slope compensation unit 20 of PWM comparators is stated, the inverting input of the PWM comparators is
The FB ends of Switching Power Supply control chip, the output end connection OR gate U2 of PWM comparators first input end 1 ".
The Cycle by Cycle current-limiting protection unit 60, for doing Cycle by Cycle current-limiting protection to primary side inductive current peak.Specifically
For the voltage inputted in first input end（Sampled signal CS1）The voltage inputted higher than the second input（Sampled signal threshold value
Voltage or reference voltage V ref）When, export high level；The voltage inputted in first input end is less than the electricity that the second input is inputted
During pressure, low level is exported.
The driver element 70, for driving external power metal-oxide-semiconductor.
Line voltage compensation control module 40, the ON time for detecting external power metal-oxide-semiconductor is big in the ON time
When the first preset time T 1, in the ON time of next external power metal-oxide-semiconductor, control line voltage compensation unit is second
Reference voltage V ref is entered without line voltage compensation, after the second preset time T 2 to reference voltage V ref in preset time T 2
Row line voltage is compensated.Specifically in a cycle that outside power MOS pipe is turned on and off, detecting external power metal-oxide-semiconductor
ON time, the ON time be more than the first preset time T 1 when, next cycle come then, control line voltage mend
Repay unit 50 in the second preset time T 2 to reference voltage V ref without line voltage compensation, after the second preset time T 2 again
Line voltage compensation is carried out to reference voltage V ref.
First preset time T 1 is determined according to the specific application parameter of Switching Power Supply control chip, still, and described
Maximum ON time of one preset time T 1 no more than external power metal-oxide-semiconductor.Second preset time T 2 is set, be in order to
Inductive current one time enough of electric discharge is given, next switch periods are prevented because inductive current is higher, and sampled signal exists
Than relatively low under line voltage compensation signal, so that it is too short this Cyclical power metal-oxide-semiconductor opening time occur.Therefore, described second is pre-
If time T2 determines also according to the specific application parameter of Switching Power Supply control chip.
The input of the sampling unit 10 is the CS ends of Switching Power Supply control chip, the output end of the sampling unit 10
Connect the input of slope compensation unit 20 and the first input end 1 of Cycle by Cycle current-limiting protection unit 60；The line voltage compensation
The input of control module 40 connects the output end of driver element 70, the output end connection of the line voltage compensation control module 40
Line voltage compensation unit 50, the input input reference voltage of the line voltage compensation unit 50, the line voltage compensation unit
Second input 2 of 50 output end connection Cycle by Cycle current-limiting protection unit 60；The output end of the slope compensation unit 20 connects
The first input end 1 ' of PWM comparator units is connect, the second input 2 ' of the PWM comparator units 30 controls for Switching Power Supply
The FB ends of chip, the output end connection OR gate U2 of the PWM comparator units 30 first input end 1 ", the Cycle by Cycle current limliting
The output end connection OR gate U2 of protection location 60 the second input 2 ", the output end connection rest-set flip-flop U3's of the OR gate U2
R ends, the S ends of the oscillator U4 connection rest-set flip-flops U3, the Q ends of the rest-set flip-flop U3 connect the input of driver element 70
End, the output end of the driver element 70 is the OUT terminal of the Switching Power Supply control chip, connects the grid of external power metal-oxide-semiconductor
Level.The CS ends of the Switching Power Supply control chip generally connect the source electrode of external power metal-oxide-semiconductor, the Switching Power Supply control chip
FB ends generally connect the feedback end of external loading, i.e., the input of FB ends is feedback signal.
Also referring to Fig. 4, for ease of illustrating the principle of Switching Power Supply control chip, the Switching Power Supply of the present invention is controlled
Chip U5 is added in conventional inverse-excitation type AC-DC converter circuit.
Can be proved by mathematical derivation, if it is actually detected to primary side inductive current waveform on superposition one rise it is oblique
Rate is more than the ramp signal of primary side inductive current descending slope half, can remove different duty to average primary side inductive current
The perturbation action of size so that the peak inductive current controlled finally converges on average inductor current.So sampling unit 10
By primary side inductive current（CS ends input signal）Sampled signal CS1 is converted into, sampled signal CS1 is defeated by slope compensation unit 20
Go out signal a CS2, CS2 and be sent to the first input end 1 ' of PWM comparator units 30, PWM comparator units 30 export one
Pwm signal.When CS2 signals are higher than the feedback voltage that FB ends are inputted, the pwm signal is high level, and 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 primary side inductive current peak, so sampling letter
Number CS1 is sent to the first input end 1 of Cycle by Cycle current-limiting protection unit 60.In order that the different situation of primary side input voltage VIN
Under, primary side inductive current peak has more preferable uniformity, so carrying out line voltage compensation to internal reference voltage V ref, i.e. logical
Cross line voltage compensation unit 50 and produce a sampled signal threshold voltage, then sampled signal threshold voltage is sent to Cycle by Cycle limit
The second input 2 of protection location 60 is flowed, then Cycle by Cycle current-limiting protection unit 60 exports a signal OCP.Work as sampled signal
CS1 is higher than sampled signal threshold voltage, then OCP signals are high level, are otherwise low level.Final pwm signal and OCP signals
One cut-off signals is exported by OR gate U2（High level）.The open signal of oscillator U4 outputs and the shut-off letter of OR gate U2 outputs
Rest-set flip-flop U3 S ends and R ends number are connected respectively to, the output end of the rest-set flip-flop U3 is that Q ends are connected to driving single 70
Input,.
Under normal circumstances, loop control is to produce open signal by oscillator U4, and PWM comparator units 30 pass through OR gate
U2 exports cut-off signals.When output voltage VO is relatively low or loads very heavy, the FB ends input of the Switching Power Supply control chip U5
Voltage it is high, Switching Power Supply control chip U5 accordingly increases the dutycycle of output signal, makes the energy increase of each cycle transmission,
So that output voltage VO is gradually increased to setting value.When output voltage VO is higher or loads very light, the Switching Power Supply control
The voltage at coremaking piece U5 FB ends declines, and the Switching Power Supply control chip U5 accordingly reduces the dutycycle of output signal, made defeated
Go out voltage VO and be gradually decreased back to setting value.When output load current reached flow point, it is very high that FB is drawn at end, now turns off
Signal is mainly the OCP signals control of the output of Cycle by Cycle current-limiting protection unit 60, in such cases, if continuing to reference voltage
Vref carries out line voltage compensation, then loop control failure, so, may just occur that flow point and recovery point are crossed in output loading
Increase with the increase of line electricity.Due to the presence of wired voltage compensation module 40, when the conducting of external power pipe metal-oxide-semiconductor（Beat
Open）, line voltage compensation control module detects ON time Ton of the external power metal-oxide-semiconductor within this cycle, works as Ton>First presets
During time T1, it is believed that input voltage VIN is very low, in next cycle, the control line of line voltage compensation control module 40 electricity
Compensating unit 50 is pressed not carry out line voltage compensation to reference voltage V ref, now, reference voltage V ref is directly inputted to Cycle by Cycle
It is for the sake of convenience, the second input 2 of Cycle by Cycle current-limiting protection unit 60 is defeated in second input 2 of current-limiting protection unit 60
The signal definition entered is CS threshold voltages（Sampled signal threshold voltage or reference voltage V ref）；When external power metal-oxide-semiconductor
ON time Ton>During the second preset time T 2, the control line voltage compensation unit 50 of line voltage compensation control module 40 is to base
Quasi- voltage Vref carries out line voltage compensation, i.e., described line voltage compensation unit 50 continue to output sampled signal threshold voltage to by
Cycle-by-cycle current limiting protection location 60.So avoid when input voltage VIN is very low, external power metal-oxide-semiconductor opening time Ton is too
Under long or close maximum ON time Ton_max, cause when external power metal-oxide-semiconductor is again turned on because CS threshold voltages are too low
Drive signal is pulled up a horse shut-off, it is impossible to bio-occlusion load output energy.
The sampled signal CS1 for the Switching Power Supply control chip that Fig. 5 provides for present invention oscillogram, due to sampled signal
CS1 corresponding is primary side inductive current, therefore Fig. 5 can reflect change feelings of the primary side inductive current in each switch periods
Condition.In a cycle, external power metal-oxide-semiconductor is opened, and primary side conducting, sampled signal CS1 magnitude of voltage rises（First week
K1 sections in phase T）, opening time Ton1 of the external power metal-oxide-semiconductor in a cycle be more than the first preset time T 1, adopting
When sample signal CS1 magnitude of voltage is more than CS threshold voltages, external power metal-oxide-semiconductor shut-off, sampled signal CS1 magnitude of voltage declines
（K2 sections in first cycle T）, drop to oscillator and export an open signal again
When, external power metal-oxide-semiconductor is opened.Second period is entered, due to the second preset time in second period
To reference voltage V ref without line voltage compensation in T2, therefore, in the second preset time T 2, sampled signal CS1 voltage
Value is no more than reference voltage V ref, and external power metal-oxide-semiconductor would not be turned off；Therefore in second period, external power metal-oxide-semiconductor
Opening time, Ton2 was still longer, it is seen then that in the case where primary side input voltage VIN is very low, the Switching Power Supply that the present invention is provided
Control chip still can export energy with controlling switch circuit to load continuous, improve efficiency.
Referring to Fig. 3, in the Switching Power Supply control chip that the present invention is provided, the line voltage compensation control module includes leading
Logical time detecting unit 410, timing unit 420 and switch element 430.
The ON time detection unit 410, the ON time for detecting external power metal-oxide-semiconductor, in the conducting
Between be more than the first preset time when, open timing unit 420.
The timing unit 420, is opened for after unlatching, receiving the Continuity signal of next external power metal-oxide-semiconductor, control
Closing unit makes line voltage compensation unit to reference voltage V ref without line voltage compensation and starts timing, in external power MOS
After the ON time of pipe is more than the second preset time, controlling switch unit 430 makes line voltage compensation unit 50 to reference voltage
Vref carries out line voltage compensation.Specifically, the timing unit 420 is after the Continuity signal of external power metal-oxide-semiconductor is received, it is defeated
Going out an enable signal closes switch element 430 and starts timing, after the second preset time, exports another and enables signal
Disconnect switch element 430.It is preferred that, the timing unit 420 includes timer.
The switch element 430, line voltage compensation is carried out for control line voltage compensation unit 50 to reference voltage V ref.
Specifically, the switch element 430 is connected in parallel on the input and output end of line voltage compensation unit 50, the switch element 430
By carrying out short circuit to line voltage compensation unit 50, line voltage compensation unit 50 is set not enter row line voltage benefit to reference voltage V ref
Repay.It is preferred that, the switch element 430 includes analog switch K, the analog switch K one end connecting line voltage compensation unit
50 input, the output end of the other end connecting line voltage compensation unit 50 of the analog switch K, the analog switch K's
Control end is connected with the output end of timing unit 420.That is, described timing unit 420, which need to export enable signal, makes analog switch K
Closure disconnects, you can control the line voltage compensation to reference voltage, so as to make sampled signal threshold voltage or benchmark electric
Pressure Vref is input to the second input of Cycle by Cycle current-limiting protection unit 60.
The first input end a of the ON time detection unit 410 is the input of line voltage compensation control module 40, connected
The output end of driver element 70 is connect, the second input b of the ON time detection unit 410 inputs the second preset time letter
Number, the output end of the ON time detection unit 410 connects the Enable Pin of timing unit 420, the letter of the timing unit 420
Number input connects the output end of driver element 70, the output end connecting valve unit 430 of the timing unit 420.
When the drive signal PWM1 that driver element 70 is exported is high, external power metal-oxide-semiconductor is opened, and ON time detection is single
Member 410 detects this cycle inside and outside power MOS pipe ON time Ton, works as Ton>First preset time T 1（Think that VIN is very low）
When, it is high effectively that ON time detection unit 410 exports one to enable signal Tonp, Tonp to timing unit 420.And then when
When next drive signal PWM2 that driver element 70 is exported is high, timing unit 420, which exports an enable signal, closes switch K
Close, i.e., CS threshold voltages do not pass through line voltage compensation unit 50, sampled signal CS1 directly compares with reference voltage V ref.Together
When timing unit 420 start timing, as external power metal-oxide-semiconductor ON time Ton>During the second preset time T 2, timing unit 420
An enable signal, which can be exported, opens switch K, i.e. ON time Ton>CS threshold voltages continue by reference voltage after T2
Vref is produced by line voltage compensation unit 50.So avoid when input voltage VIN is very low, when power MOS pipe is opened
Between it is oversize or close under maximum ON time, cause drive signal to stand because CS threshold values are too low when power MOS pipe is again turned on
Break in Maguan, it is impossible to bio-occlusion load output energy.
Referring to Fig. 4, the present invention also provides a kind of inverse-excitation type AC-DC converter, including as above opening described in an embodiment
Close power supply control chip U5, in addition to the first diode D1, the second diode D2, the first electric capacity C1, the second electric capacity C2, transformer
80th, power MOS pipe Q1, operational amplifier Q2, optocoupler U6, first resistor R1, second resistance R2,3rd resistor R3 and the 4th resistance
R4。
The transformer 80 includes primary side winding Np, assists winding Na and vice-side winding Ns.The one of the primary side winding Np
Hold the voltage input end for inverse-excitation type AC-DC converter, receive the input voltage VIN of outside input, the primary side winding Np's
Other end connection power MOS pipe Q1 drain electrode, the grid level connection Switching Power Supply control chip U5 of power MOS pipe Q1 OUT
End, the source electrode connecting valve power supply control chip U5 of power MOS pipe Q1 CS ends, is also grounded by first resistor R1；Institute
State assists winding Na to be connected with primary side winding Np sensings, one end ground connection of the assists winding Na, the assists winding Na's is another
One end connects the first diode D1 positive pole, the negative pole connecting valve power supply control chip U5 of the first diode D1 Vcc
Hold, also pass through the first electric capacity C1 ground connection；The vice-side winding Ns is connected with primary side winding Np sensings, and the one of the vice-side winding Ns
The second diode D2 of end connection positive pole, the negative pole of the second diode D2 exports for the first of inverse-excitation type AC-DC converter
The one end, second resistance R2 one end and the 3rd resistor R3 that hold, connect the second electric capacity C2 one end, the vice-side winding Ns's is another
One end is the second output end of inverse-excitation type AC-DC converter, the second electric capacity C2 of the connection other end；The second resistance R2's is another
One end connection opto-coupler chip U6 first end c, the 3rd resistor R3 other end concatenation operation amplifier Q2 positive input
Hold, also pass through the 4th resistance R4 concatenation operation amplifiers Q2 inverting input, the output end of the operational amplifier Q2 is connected
Opto-coupler chip U6 the second end d, the opto-coupler chip U6 the 3rd end e ground connection, the 4th end f connections of the opto-coupler chip U6 are opened
Close power supply control chip U5 FB ends, the GND ends ground connection of the Switching Power Supply control chip U5.Wherein, the power MOS pipe Q1
For NMOS tube.Load, the switch electricity are connected between the first output end and the second output end of the inverse-excitation type AC-DC converter
Source control chip U5 is according to load（That is output end voltage Vo）Change, by adjust power MOS pipe Q1 conducting dutycycle to
Load output galvanic current pressure.
Because the operation principle and feature of the inverse-excitation type AC-DC converter have been elaborated in a upper embodiment,
This is repeated no more.
It is understood that for those of ordinary skills, can be with technique according to the invention scheme and its hair
Bright design is subject to equivalent substitution or change, and all these changes or replacement should all belong to the guarantor of appended claims of the invention
Protect scope.
Claims (8)
1. a kind of Switching Power Supply control chip, it is characterised in that including oscillator, OR gate, rest-set flip-flop, sampling unit, slope
Compensating unit, line voltage compensation unit, PWM comparator units, Cycle by Cycle current-limiting protection unit, driver element and line voltage compensation
Control module；
Sampling unit is sampled to primary side inductive current and is exported sampled signal to slope compensation unit and Cycle by Cycle current limliting
Protection location；Slope compensation unit is superimposed a rate of rise more than drop angle under 1/2nd primary side inductive currents in sampled signal
The ramp signal of rate, which is exported, gives PWM comparator units；PWM comparator units compare the FB ends and slope of Switching Power Supply control chip
The signal of compensating unit output, the first input end according to comparative result output pwm signal to OR gate；Line voltage compensation controls mould
Block detects the ON time of external power metal-oxide-semiconductor, when the ON time is more than the first preset time, in next circumferential work
In the ON time of rate metal-oxide-semiconductor, control line voltage compensation unit is in the second preset time to reference voltage without line voltage
Compensate, line voltage compensation is carried out to reference voltage after the second preset time；Cycle by Cycle current-limiting protection unit is mended according to line voltage
The sampled signal threshold voltage of unit output is repaid, Cycle by Cycle current-limiting protection is done to sampled signal and is exported inputting to the second of OR gate
End；The signal that OR gate is inputted according to first input end and the second input, exports R end of the cut-off signals to rest-set flip-flop, vibrates
Device exports S end of the open signal to rest-set flip-flop, and the Q ends of rest-set flip-flop control external power metal-oxide-semiconductor by driver element
Turn-on and turn-off.
2. Switching Power Supply control chip according to claim 1, it is characterised in that the line voltage compensation control module bag
Include ON time detection unit, timing unit and switch element；
The ON time detection unit, the ON time for detecting external power metal-oxide-semiconductor is more than the in the ON time
During one preset time, timing unit is opened；
The timing unit, for after unlatching, receiving Continuity signal, the controlling switch unit of next external power metal-oxide-semiconductor
Make line voltage compensation unit to reference voltage without line voltage compensation and start timing, in the conducting of outside power MOS pipe
Between more than the second preset time after, controlling switch unit make line voltage compensation unit to reference voltage carry out line voltage compensation；
The switch element, line voltage compensation is carried out for control line voltage compensation unit to reference voltage.
3. Switching Power Supply control chip according to claim 2, it is characterised in that the timing unit includes timer.
4. Switching Power Supply control chip according to claim 3, it is characterised in that the switch element is opened including simulation
Close, the input of one end connecting line voltage compensation unit of the analog switch, the other end connecting line electricity of the analog switch
The output end of compensating unit is pressed, the control end of the analog switch and the output end of timing unit are connected.
5. Switching Power Supply control chip according to claim 4, it is characterised in that the PWM comparator units include PWM
Comparator, the normal phase input end of the PWM comparators connects the output end of slope compensation unit, the PWM comparators it is anti-phase
Input is the FB ends of Switching Power Supply control chip, and the output end of the PWM comparators connects the first input end of OR gate.
6. a kind of inverse-excitation type AC-DC converter, it is characterised in that including the Switching Power Supply control as described in claim 1-5 is any
Coremaking piece.
7. inverse-excitation type AC-DC converter according to claim 6, it is characterised in that the inverse-excitation type AC-DC converter is also
Including the first diode, the second diode, the first electric capacity, the second electric capacity, transformer, power MOS pipe, operational amplifier, optocoupler,
First resistor, second resistance, 3rd resistor and the 4th resistance；The transformer include primary side winding, assists winding and secondary around
Group；One end of the primary side winding is the voltage input end of inverse-excitation type AC-DC converter, the input voltage of reception outside input,
The other end of the primary side winding connects the drain electrode of power MOS pipe, the grid level connection Switching Power Supply control core of the power MOS pipe
The OUT terminal of piece, the CS ends of the source electrode connecting valve power supply control chip of the power MOS pipe, is also grounded by first resistor；Institute
State assists winding to be connected with primary side winding sensing, one end ground connection of the assists winding, the other end connection of the assists winding
The positive pole of first diode, the Vcc ends of the negative pole connecting valve power supply control chip of first diode, also pass through first electricity
Hold ground connection；The vice-side winding is connected with primary side winding sensing, and one end of the vice-side winding connects the positive pole of the second diode,
The negative pole of second diode is the first output end of inverse-excitation type AC-DC converter, the one end for connecting the second electric capacity, the second electricity
One end of resistance and one end of 3rd resistor, the other end of the vice-side winding for inverse-excitation type AC-DC converter the second output end,
Connect the other end of the second electric capacity；The other end of the second resistance connects the first end of opto-coupler chip, the 3rd resistor
The normal phase input end of other end concatenation operation amplifier, also pass through the inverting input of the 4th resistance concatenation operation amplifier, institute
The output end for stating operational amplifier connects the second end of opto-coupler chip, the 3rd end ground connection of the opto-coupler chip, the optocoupler core
The FB ends of 4th end connecting valve power supply control chip of piece, the GND ends ground connection of the Switching Power Supply control chip.
8. inverse-excitation type AC-DC converter according to claim 7, it is characterised in that the power MOS pipe is NMOS tube.
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| CN106357110B (en) * | 2016-09-26 | 2018-08-14 | 辉芒微电子（深圳）有限公司 | A kind of BUCK constant voltage drive circuits and BUCK constant-voltage drivers |
| CN106712511B (en) * | 2016-12-30 | 2019-01-29 | 矽力杰半导体技术(杭州)有限公司 | Superaudio mode control circuit, switch converters and its control circuit |
| CN109742737B (en) * | 2019-03-19 | 2023-10-03 | 无锡麟力科技有限公司 | Overcurrent protection circuit based on fixed period switching power supply |
| CN111158265B (en) * | 2020-01-22 | 2023-04-14 | Msj系统有限责任公司 | Simulation device of power management chip |
| CN111585426B (en) * | 2020-05-12 | 2021-07-27 | 西安爱科赛博电气股份有限公司 | Switch-cycle-by-switch-cycle peak current limiting system and method for DC-AC converter |
| CN112054525B (en) * | 2020-08-31 | 2022-09-30 | 深圳供电局有限公司 | Series active power filter |
| CN112290812B (en) * | 2020-10-26 | 2021-11-16 | 深圳市稳先微电子有限公司 | AC-DC control chip and AC-DC flyback controller |
| CN115134970B (en) * | 2022-08-29 | 2022-12-09 | 苏州贝克微电子股份有限公司 | Low-voltage constant-current driving circuit |
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