CN108173435B - Switch power supply control unit and quasi-resonant switch power supply self-adaptive valley locking circuit - Google Patents
Switch power supply control unit and quasi-resonant switch power supply self-adaptive valley locking circuit Download PDFInfo
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- CN108173435B CN108173435B CN201810128823.0A CN201810128823A CN108173435B CN 108173435 B CN108173435 B CN 108173435B CN 201810128823 A CN201810128823 A CN 201810128823A CN 108173435 B CN108173435 B CN 108173435B
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M3/00—Conversion of dc power input into dc power output
- H02M3/22—Conversion of dc power input into dc power output with intermediate conversion into ac
- H02M3/24—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters
- H02M3/28—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac
- H02M3/325—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal
- H02M3/335—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only
- H02M3/33507—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of the output voltage or current, e.g. flyback converters
- H02M3/33523—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of the output voltage or current, e.g. flyback converters with galvanic isolation between input and output of both the power stage and the feedback loop
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
- H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
- H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
- H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
- H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
- H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
- H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M7/4815—Resonant converters
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
- Y02B70/00—Technologies for an efficient end-user side electric power management and consumption
- Y02B70/10—Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes
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- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Dc-Dc Converters (AREA)
Abstract
The invention provides a quasi-resonance switching power supply self-adaptive valley locking circuit, which comprises: the power supply comprises an input rectifying and filtering circuit, a switching power supply control unit, a transformer T206, an output rectifying and filtering circuit, an output feedback circuit, a power tube N1 and a primary current sampling resistor Rcs; the positive output end of the input rectifying and filtering circuit is connected with the synonym end of the primary winding of the transformer T206, and the negative output end of the input rectifying and filtering circuit is connected with the primary ground; the primary winding of the transformer T206 is connected with the current input end of the power tube N1 in the same name, the current output end of the power tube N1 is connected with one end of the primary current sampling resistor Rcs, and the other end of the primary current sampling resistor Rcs is connected with primary ground; the non-inverting input end of the peak current comparator U230 is connected with one end of the primary current sampling resistor Rcs; the output end of the driving circuit U231 is connected with the switch control end of the power tube N1; the secondary winding of the transformer T206 is connected with an output rectifying and filtering circuit; the circuit avoids abnormal sound of the transformer caused by vibration due to overlarge change of the switching frequency caused by sampling errors.
Description
Technical Field
The invention belongs to the field of integrated circuits; more specifically, the invention provides a novel self-adaptive valley locking circuit of a quasi-resonant switching power supply, and particularly relates to a flyback switching power supply control technology.
Background
With the implementation of new energy efficiency standards and the continuous improvement of the performance of electronic products, higher requirements are put forward on the conversion efficiency and the power density of the switching power supply, and the system cost of the switching power supply is controlled more and more severely, so that the improvement of the conversion efficiency of the switching power supply cannot be implemented simply by increasing the cost and other modes. At present, a quasi-resonance valley conduction technology is generally adopted in the market to reduce the switching loss of a power tube in the switching process, improve the conversion efficiency of a system, reduce the temperature rise of the system, improve the reliability of products and the like.
However, the quasi-resonant valley conduction technology has defects, and is easy to cause abnormal sound phenomenon caused by transformer vibration or problems such as actual deterioration of EMI performance. The above problems are mainly caused by the fact that the switching frequency is discontinuous when the valley is conducted, and the problem that the switching amplitude of the valley is overlarge due to sampling deviation. The problems are common to products currently on the market which adopt the quasi-resonant valley technology.
The quasi-resonant valley conduction technology can greatly reduce the switching loss, is suitable for the development trend of high frequency, small volume and high power density of a switching power supply, and becomes a main flow control technology of the switching power supply in the future, so that the defects of the quasi-resonant valley conduction technology must be overcome.
Disclosure of Invention
The invention aims to overcome the defects in the prior art, provides a self-adaptive valley locking circuit of a quasi-resonant switching power supply, and solves the problem of abnormal sound of a transformer caused by vibration due to overlarge change of switching frequency when the valley is switched. The technical scheme adopted by the invention is as follows:
a switching power supply control unit comprising:
a sample-and-hold module U221, an error amplifier U223, a sawtooth wave generator U224, a PWM comparator U225, a quasi-resonant valley-bottom comparator U242, an NOT gate U243, an NOT gate U227, a valley-bottom lock enabling module U229, a valley-bottom locking module U228, a switch latch U232, a driving circuit U231 and a peak current comparator U230;
the input end of the sample-hold module U221 and the non-inverting input end of the quasi-resonant valley comparator U242 are respectively connected with auxiliary winding voltage division feedback signals; the output end of the sample-hold module U221 is connected with the inverting input end of the error amplifier U223, and the non-inverting input end of the error amplifier U223 is used for regulating the voltage signal V th_FB The method comprises the steps of carrying out a first treatment on the surface of the The output signal Comp of the error amplifier U223 is connected with the inverting input end of the PWM comparator U225, and the sawThe output of the tooth wave generator U224 is connected with the non-inverting input end of the PWM comparator U225; the output end of the PWM comparator U225 is connected with one input end of the NOR gate U227;
the inverting input end of the quasi-resonant valley bottom comparator U242 is connected with the valley bottom discrimination reference signal V th_DEM The method comprises the steps of carrying out a first treatment on the surface of the The output end of the quasi-resonant valley comparator U242 is connected with the other input end of the NOR gate U227 and the input end of the NOR gate U243; the output of the nor gate U227 and the output signal QR of the nor gate U243 are respectively input to the valley lock module U228;
the error amplifier output signal Comp and the power tube switch signal On are respectively input into a valley lock enabling module U229, and a valley lock enabling signal lockEn generated by the valley lock enabling module U229 is input into a valley lock module U228; the power tube switch signal On is input into a valley locking module U228; the power tube conduction trigger signal set output by the output end of the valley locking module U228 is input to the S end of the switch latch U232; the switching latch U232 is an RS trigger, and the R end of the switching latch U232 is connected with the output end of the peak current comparator U230; the non-inverting input end of the peak current comparator U230 is connected with one end of the primary current sampling resistor Rcs, and the inverting input end is connected with the peak current reference signal V th_CS ；
The Q terminal of the switching latch U232 outputs a power tube switching signal On, the power tube switching signal On is input to the input terminal of the driving circuit U231, and the output terminal of the driving circuit U231 is connected to the switching control terminal of the power tube N1.
Further, the valley lock enable module U229 includes: MOS switches K321 and K322, an inverter U313, capacitors C323 and C324, an isolation buffer amplifier U331, a positive voltage bias V332, a negative voltage bias V333, hysteresis comparators U334 and U335, a NOR gate U336 and a counter U337;
the power tube switch signal On is connected with the control end of the MOS switch K321 and the input end of the inverter U313; the output signal Comp of the error amplifier U223 is connected with one end of the MOS switch K321, and the other end of the MOS switch K321 is connected with one end of the MOS switch K322 and is grounded through the capacitor C323; the output end of the inverter U313 is connected with the control end of the MOS switch K322, and the other end of the MOS switch K322 is connected with the input end of the isolation buffer amplifier U331 and is grounded through the capacitor C324;
the output end of the isolation buffer amplifier U331 is connected with the inverting end of the hysteresis comparator U334 through a positive voltage bias V332 respectively, and is connected with the non-inverting end of the hysteresis comparator U335 through a negative voltage bias V333; the same phase of the hysteresis comparator U334 is connected with the output signal Comp of the error amplifier U223; the inverse phase of the hysteresis comparator U335 is connected with the output signal Comp of the error amplifier U223; the output ends of the hysteresis comparators U334 and U335 are respectively connected with two input ends of the NOR gate U336; the output of the NOR gate U336 is connected with the reset end of the counter U337, and the clock end of the counter U337 is connected with the power tube switch signal On; the output of the counter U337 outputs a valley lock enable signal LockEn.
Further, the valley lock enable signal LockEn is also input to the control terminals of the hysteresis comparators U334 and U335, respectively, so as to increase the hysteresis intervals of the hysteresis comparators U334 and U335 when the LockEn signal is at a high level.
Further, the valley lock module U228 includes: d flip-flop U411, counter U415, counter U416, digital comparator U417, selector U418, nor gates U412, U413, nor gate U414;
the clock end of the D trigger U411 is connected with the output signal PWM of the NOR gate U227; the valley lock enable signal lockEn is respectively connected with the reset end of the D trigger U411 and the reset end of the counter U415; the D terminal of the D trigger U411 is connected with a high level;
the Q output of the D flip-flop U411 is connected with one input end of the NOR gate U412 and the selection control end of the selector U418; d flip-flop U411The output end is connected with one input end of the NOR gate U413; the other inputs of nor gates U412 and U413 are connected to the output signal QR of nor gate U243; the output end of the nor gate U412 is connected with the clock end of the counter U415, and the output end of the nor gate U413 is connected with the clock end of the counter U146; the power tube switch signal On is connected with the input end of the NOT gate U414, and the output end of the NOT gate U414 is connected with the reset end of the counter U416; the output ends of the counters U415 and U416 are respectively connected with two input ends of the digital comparator U417; the output end of the digital comparator U417 and the output signal PWM of the NOR gate U227 are respectively connected with two of the selector U418An input end; the output of the selector U148 outputs the power tube on trigger signal ONset.
A quasi-resonant switching power supply self-adaptive valley locking circuit comprising:
the power supply comprises an input rectifying and filtering circuit, the switching power supply control unit, a transformer T206, an output rectifying and filtering circuit, an output feedback circuit, a power tube N1 and a primary current sampling resistor Rcs;
the positive output end of the input rectifying and filtering circuit is connected with the synonym end of the primary winding of the transformer T206, and the negative output end of the input rectifying and filtering circuit is connected with the primary ground;
the primary winding of the transformer T206 is connected with the current input end of the power tube N1 in the same name, the current output end of the power tube N1 is connected with one end of the primary current sampling resistor Rcs, and the other end of the primary current sampling resistor Rcs is connected with primary ground;
the non-inverting input end of the peak current comparator U230 is connected with one end of the primary current sampling resistor Rcs; the output end of the driving circuit U231 is connected with the switch control end of the power tube N1;
the secondary winding of the transformer T206 is connected with an output rectifying and filtering circuit, and the DC voltage is output through the output rectifying and filtering circuit;
the output feedback circuit comprises an output feedback auxiliary winding of the transformer T206, and two ends of the output feedback auxiliary winding are connected with resistors R1 and R2 in series; obtaining an auxiliary winding voltage division feedback signal from the connection point of the series resistors R1 and R2; the auxiliary winding voltage division feedback signal is connected with the input end of the sample-hold module U221 and the non-inverting input end of the quasi-resonant valley-bottom comparator U242.
The invention has the advantages that: the invention obtains the average resonant valley bottom number through the integration process, and uses the average resonant valley bottom number as a reference to pre-judge and control the conduction of the power tube in the next period, thereby avoiding the abnormal sound problem of the transformer caused by vibration due to overlarge change of the switching frequency caused by sampling errors.
Drawings
Fig. 1 is a schematic diagram of quasi-resonant adaptive valley conduction in accordance with the present invention.
Fig. 2 is a schematic diagram of a quasi-resonant switching power supply adaptive valley locking circuit of the present invention.
Fig. 3 is a schematic diagram of the inside of the valley lock enable module of the present invention.
Fig. 4 is a schematic diagram of the interior of the valley lock module of the present invention.
Detailed Description
The invention will be further described with reference to the following specific drawings and examples.
The invention provides a quasi-resonant switching power supply self-adaptive valley locking circuit, as shown in fig. 2, comprising:
an input rectifying and filtering circuit, a switching power supply control unit 220, a transformer T206, an output rectifying and filtering circuit 207, an output feedback circuit 208, a power tube N1 and a primary current sampling resistor Rcs;
the switching power supply control unit 220 is a core of the present invention, and includes: a sample-and-hold module U221, an error amplifier U223, a sawtooth wave generator U224, a PWM comparator U225, a quasi-resonant valley-bottom comparator U242, an NOT gate U243, an NOT gate U227, a valley-bottom lock enabling module U229, a valley-bottom locking module U228, a switch latch U232, a driving circuit U231 and a peak current comparator U230; the on of the power tube N1 is controlled by the output signal of the valley locking module U228, and the off of the power tube N1 is controlled by the output signal of the peak current comparator U230;
the input rectifying and filtering circuit comprises a bridge rectifying circuit formed by diodes D201-D204 and a filtering capacitor C205; the positive output end of the input rectifying and filtering circuit is connected with the synonym end of the primary winding of the transformer T206, and the negative output end of the input rectifying and filtering circuit is connected with the primary ground;
the primary winding of the transformer T206 is connected with the current input end of the power tube N1 in the same name, the current output end of the power tube N1 is connected with one end of the primary current sampling resistor Rcs, and the other end of the primary current sampling resistor Rcs is connected with primary ground; the power tube N1 can adopt an NMOS tube, the drain electrode and the source electrode of the NMOS tube are respectively used as a current input end and a current output end, and the grid electrode of the NMOS tube is used as a switch control end;
the secondary winding of the transformer T206 is connected with an output rectifying and filtering circuit 207, and the DC voltage is output through the output rectifying and filtering circuit 207; the output rectifying and filtering circuit 207 may include a rectifying diode, a filtering capacitor, an output resistor, etc., which are conventional circuits in the prior art and will not be described in detail;
the output feedback circuit 208 comprises an output feedback auxiliary winding of the transformer T206, and two ends of the output feedback auxiliary winding are connected with resistors R1 and R2 in series; obtaining an auxiliary winding voltage division feedback signal 110 from the connection point of the series resistors R1 and R2;
the input end of the sample-hold module U221 and the non-inverting input end of the quasi-resonant valley comparator U242 are respectively connected with the auxiliary winding voltage division feedback signal 110; the output end of the sample-hold module U221 is connected with the inverting input end of the error amplifier U223, and the non-inverting input end of the error amplifier U223 is used for regulating the voltage signal V th_FB The method comprises the steps of carrying out a first treatment on the surface of the The output signal Comp of the error amplifier U223 is connected with the inverting input end of the PWM comparator U225, and the output of the sawtooth wave generator U224 is connected with the non-inverting input end of the PWM comparator U225; the output end of the PWM comparator U225 is connected with one input end of the NOR gate U227;
the inverting input end of the quasi-resonant valley bottom comparator U242 is connected with the valley bottom discrimination reference signal V th_DEM The method comprises the steps of carrying out a first treatment on the surface of the The output end of the quasi-resonant valley comparator U242 is connected with the other input end of the NOR gate U227 and the input end of the NOR gate U243; the output of the nor gate U227 and the output signal QR of the nor gate U243 are respectively input to the valley lock module U228;
the error amplifier output signal Comp and the power tube switch signal On are respectively input into a valley lock enabling module U229, and a valley lock enabling signal lockEn generated by the valley lock enabling module U229 is input into a valley lock module U228; the power tube switch signal On is input into a valley locking module U228; the power tube conduction trigger signal set output by the output end of the valley locking module U228 is input to the S end of the switch latch U232; the switching latch U232 is an RS trigger, and the R end of the switching latch U232 is connected with the output end of the peak current comparator U230; the non-inverting input end of the peak current comparator U230 is connected with one end of the primary current sampling resistor Rcs, and the inverting input end is connected with the peak current reference signal V th_CS ；
The Q end of the switch latch U232 outputs a power tube switch signal On which is added to the switch control end of the power tube N1 through the driving circuit U231;
fig. 1 is a quasi-resonant adaptive valley conduction schematic. The auxiliary winding voltage division feedback signal 110 is sampled and held and then used as an input signal of an error amplifier U223; the output signal 120 of the sawtooth wave generator is used as one input signal of the PWM comparator U225, the output signal Comp of the error amplifier is used as the other input signal of the PWM comparator U225, when the signal 120 crosses the signal Comp, the output signal of the PWM comparator U225 forms the signal 141 from high to low, and the signal 141 is combined with the output signal 150 of the quasi-resonant valley comparator U242 to form the power tube on trigger signal ONset.
When the signal ONset goes from low to high, the sawtooth signal 120 immediately returns to its original state and is ready to generate the next cycle of sawtooth signal, and the output signal of the PWM comparator U225 also immediately inverts as the sawtooth signal 120 changes, forming a negative narrow pulse, as shown by signal 141 in fig. 1.
When there is a deviation in the feedback signal FB, i.e., the sampling of the auxiliary winding divided voltage feedback signal 110, the deviation signal will also be amplified by the error amplifier U223, causing the output value of the error amplifier U223 to deviate as shown by signals 131 and 133 in fig. 1, which will result in a change in the position of the output signal of the PWM comparator U225 as shown by signals 142 and 143 in fig. 1, and a deviation in the power-on signal as shown by signals 162 and 163. And signal 161 is a normal power tube on signal.
Signal 111 corresponds to the average value of the system switching frequency, and when the resonant valley turn-on signals 112 and 113 vary relatively greatly with respect to signal 111, this indicates that the frequency of the switching power supply varies greatly, which can easily lead to abnormal noise problems due to transformer oscillations.
The invention obtains the average value of the output of the error amplifier by integrating the output of the error amplifier and filtering the error component of the amplifier caused by sampling error, and the average value corresponds to the average value of the switching frequency. And superposing positive and negative offset on the output average value of the error amplifier to form a voltage window, comparing the voltage window with the output instantaneous value of the error amplifier, and when the output instantaneous value of the error amplifier falls in the range of the voltage window and continuously keeps a plurality of switching cycles, starting a valley locking mode by the system and increasing the range of the voltage window, so that valley locking unlocking caused by false triggering is avoided. When the output instantaneous quantity of the error amplifier exceeds the range of the increased voltage window, the valley locking and unlocking are carried out, and the system restarts the valley locking process.
The auxiliary winding partial pressure feedback signal 110 is obtained from the auxiliary winding coil through sampling and is maintained in the demagnetizing stage of the transformer through the coil coupling relation of the primary winding and the auxiliary winding of the transformer T206; the sample-and-hold signal is used as the negative feedback input of the error amplifier U223, and the sample-and-hold signal and the reference voltage signal V th_FB After amplification by error amplifier U223, the output error signal automatically achieves loop regulation, indicating that the output load is increased when the output error signal is high, and indicating that the output load is decreased when the output error signal is low.
The output signal Comp of the error amplifier U223 and the sawtooth wave signal generated by the sawtooth wave generator are modulated by a PWM comparator U225, and PWM signals are generated and input to a valley locking module U228; the quasi-resonant valley comparator compares the auxiliary winding voltage division feedback signal 110 with the valley discrimination reference signal V th_DEM Outputting a resonance valley signal as another input of the valley locking module;
the valley lock enable module U229 integrates the output of the error amplifier U223 to filter out the amplifier error output component due to the sampling error, and obtains the output average value of the error amplifier. And superposing positive and negative offset on the output average value of the error amplifier U223 to form a voltage window, comparing the voltage window with the output instantaneous value of the error amplifier U223, when the output instantaneous value of the error amplifier U223 falls in the range of the voltage window and continuously keeps a plurality of switching cycles, outputting a valley lock enabling signal lockEn by a valley lock enabling module and increasing the range of the voltage window, and when the output instantaneous value of the error amplifier U223 exceeds the range of the increased voltage window, unlocking the valley lock, and restarting the valley lock process by the system.
The valley bottom locking module U228 latches the average value of the number of the resonant valleys corresponding to the output integral quantity of the error amplifier, and is used as a reference comparison signal of the digital comparator to be compared with the output of another valley bottom real-time counter (a later counter U416), each period of the valley bottom real-time counter is cleared to be recounted, when the counting period of the other valley bottom real-time counter reaches the latched average value of the number of the resonant valleys, the digital comparator outputs a next period conduction trigger signal, and the self-adaptive valley bottom of the quasi-resonant switching power supply is locked.
The output signal of the valley lock module U228 sets the switch latch U232 to control the conduction of the power tube N1, the reset signal of the switch Guan Suocun U232 is the output of the peak current comparator U230, and the power tube N1 is turned off after reset.
The peak current comparator U230 compares the voltage drop of the power tube end sampling resistor Rcs with the peak current threshold voltage, and outputs a high level signal to reset the switch latch U232, so as to control the turn-off of the power tube.
The specific working process of the invention is described in detail below, namely the implementation of the valley lock enabling module U229 and the valley lock module U228;
after the power tube N1 is turned on, the transformer T206 enters a demagnetizing process, the sample-hold module U221 samples and stores the auxiliary winding voltage division feedback signal 110 as one input signal of the error amplifier U223, and the other input signal of the error amplifier U223 is a reference voltage signal V th_FB The method comprises the steps of carrying out a first treatment on the surface of the Sample-and-hold signal and reference voltage signal V th_FB After being amplified by the error amplifier U223, the output signal Comp is connected to one input terminal of the PWM comparator U225;
the other input signal of the PWM comparator U225 is connected to the output of the sawtooth generator U224; comparing with the output signal Comp of the error amplifier U223, outputting one of the switch control signals;
the other switch control signal is generated by a quasi-resonant valley-bottom comparator U242, one input end of the quasi-resonant valley-bottom comparator U242 is connected with the auxiliary winding voltage division feedback signal 110, and the other input end is connected with the valley-bottom discrimination reference signal V th_DEM . The output signal of the quasi-resonant valley-bottom comparator U242 is used as a synchronous signal for conducting the valley bottom of the power tube, and is combined with the output signal of the PWM comparator U225 through the NOR gate U227 and then is input into the valley-bottom locking module U228.
The valley bottom locking enabling module U229 calculates a switching frequency average value in real time, and when the error obtained by calculating the switching frequency average value is smaller than a set range, the valley bottom locking enabling module U229 outputs a valley bottom locking enabling signal to control the valley bottom locking module U228 to enter a frequency locking process;
after the valley lock enable module U229 sends out the valley lock enable signal, the valley lock module 228 calculates and stores the resonant valley cycle number corresponding to the switching frequency average value, and uses the resonant valley cycle number average value as the resonant valley number average value to be connected to an input terminal of the digital comparator. The other input end of the digital comparator is connected with a valley real-time counter, the valley real-time counter can count again in each switching period, the valley real-time counter is automatically cleared when the power tube is conducted, and counting is started in the resonance process after demagnetization is finished. When the count value of the real-time counter at the bottom of the valley reaches the average value of the number of the resonant valleys, the digital comparator outputs a high-level signal to trigger the power tube to be conducted.
Before the valley lock, the on trigger signal of the power transistor N1 is controlled by the combination of the output of the PWM comparator U225 and the output of the quasi-resonant valley comparator U242.
The turn-off signal of the power tube N1 is generated by the peak current comparator U230; after the power tube N1 is conducted, the primary side inductor enters an excitation state, the inductor current is continuously increased, and when the voltage drop of the inductor current on the sampling resistor Rcs is larger than the peak current reference signal V th_CS When the peak current comparator U230 outputs a high level, the switching register U232 is cleared, and the power transistor N1 is turned off.
The electrical principle of the valley lock enable module U229 is seen in fig. 3; comprising the following steps: MOS switches K321 and K322, an inverter U313, capacitors C323 and C324, an isolation buffer amplifier U331, a positive voltage bias V332, a negative voltage bias V333, hysteresis comparators U334 and U335, a NOR gate U336 and a counter U337;
the power tube switch signal On is connected with the control end of the MOS switch K321 and the input end of the inverter U313; the output signal Comp of the error amplifier U223 is connected with one end of the MOS switch K321, and the other end of the MOS switch K321 is connected with one end of the MOS switch K322 and is grounded through the capacitor C323; the output end of the inverter U313 is connected with the control end of the MOS switch K322, and the other end of the MOS switch K322 is connected with the input end of the isolation buffer amplifier U331 and is grounded through the capacitor C324;
the output end of the isolation buffer amplifier U331 is connected with the inverting end of the hysteresis comparator U334 through a positive voltage bias V332 respectively, and is connected with the non-inverting end of the hysteresis comparator U335 through a negative voltage bias V333; the same phase of the hysteresis comparator U334 is connected with the output signal Comp of the error amplifier U223; the inverse phase of the hysteresis comparator U335 is connected with the output signal Comp of the error amplifier U223; the output ends of the hysteresis comparators U334 and U335 are respectively connected with two input ends of the NOR gate U336; the output of the NOR gate U336 is connected with the reset end of the counter U337, and the clock end of the counter U337 is connected with the power tube switch signal On; the output end of the counter U337 outputs a valley lock enabling signal lockEn;
more preferably, the valley lock enable signal LockEn is further input to the control ends of the hysteresis comparators U334 and U335 respectively, so as to increase the hysteresis intervals of the hysteresis comparators U334 and U335 when the LockEn signal is at a high level;
the signal Comp is the output of the error amplifier U223, the signal On is the signal controlling the power transistor switch, and the inverter U313, the MOS switches K321, K322, and the capacitors C323 and C324 constitute a low frequency integrated circuit. In each switching process, the output signal Comp of the error amplifier U223 is transferred once to the capacitor C324 through the capacitor C323, and the frequency characteristic of the low-frequency integrated circuit depends on the switching frequency and the proportional relationship between the capacitor C323 and the capacitor C324. After the system switch is stable, the voltage on the capacitor C324 is the average value of the output signal Comp of the error amplifier U223.
The isolation buffer amplifier U331 and the positive voltage bias V332, the negative voltage bias V333 constitute a voltage window centered on the integrated voltage as the reference voltages for the hysteresis comparators U334 and U335. The other input signal of the hysteresis comparators U334 and U335 is the output signal Comp of the error amplifier. When the signal Comp of the error amplifier falls within the voltage window range centered on the integrated voltage, the nor gate U336 outputs a high level signal, the counter U337 starts to calculate, and if the nor gate U336 outputs a high level in the continuous 32 switching cycles, the LockEn signal output by the counter U337 is a high level signal, indicating that the valley lock module U228 operates.
When the LockEn signal is at a high level, hysteresis intervals of hysteresis comparators U334 and U335 are increased to increase a voltage window range with integrated voltage as a center, so that valley lock unlocking caused by false triggering is prevented.
The electrical principle of valley lock module U228 is shown in fig. 4, including: d flip-flop U411, counter U415, counter U416, digital comparator U417, selector U418, nor gates U412, U413, nor gate U414;
the clock end of the D trigger U411 is connected with the output signal PWM of the NOR gate U227; the valley lock enable signal lockEn is respectively connected with the reset end of the D trigger U411 and the reset end of the counter U415; the D terminal of the D trigger U411 is connected with a high level;
the Q output of the D flip-flop U411 is connected with one input end of the NOR gate U412 and the selection control end of the selector U418; d flip-flop U411The output end is connected with one input end of the NOR gate U413; the other inputs of nor gates U412 and U413 are connected to the output signal QR of nor gate U243; the output end of the nor gate U412 is connected with the clock end of the counter U415, and the output end of the nor gate U413 is connected with the clock end of the counter U146; the power tube switch signal On is connected with the input end of the NOT gate U414, and the output end of the NOT gate U414 is connected with the reset end of the counter U416; the output ends of the counters U415 and U416 are respectively connected with two input ends of the digital comparator U417; the output end of the digital comparator U417 and the output signal PWM of the NOR gate U227 are respectively connected with two input ends of the selector U418; the output end of the selector U148 outputs a power tube conduction trigger signal ONset;
when the signal LockEn is low, the counter U415 is always in a clear state, and the D flip-flop U411 is cleared.
When the signal LockEn goes high, the counter U415 starts counting, and on the rising edge of the signal PWM from low to high, the output signal 425 of the D flip-flop U411 goes high, the counter U415 stops counting and holds the count value, and the count value of the counter U415 serves as a comparison reference value 427 of the digital comparator U417.
When the power tube switch signal On is at a high level, the counter U416 is cleared; when the power transistor switch signal On is at a low level and the output signal 425 of the D flip-flop U411 becomes at a high level, the counter U416 starts counting, and the output of the counter U416 is taken as the other comparison value 428 of the digital comparator U417. When the comparison value 428 is equal to 427, the digital comparator U417 outputs a high level.
The output signal of the selector U418 is selected by the high-low level of the signal 425, the output signal PWM of the nor gate U227 is output to the signal ONset when the signal 425 is low, and the output signal 429 of the digital comparator U417 is output to the signal ONset when the signal 425 is high.
By way of example only, the present invention has been applied to flyback power converters. It will be appreciated that the invention has a broader range of applications.
Finally, it should be noted that the above-mentioned embodiments are only for illustrating the technical solution of the present invention, and not for limiting the same, and although the present invention has been described in detail with reference to examples, it should be understood by those skilled in the art that modifications and equivalents may be made to the technical solution of the present invention without departing from the spirit and scope of the technical solution of the present invention, and all such modifications and equivalents are intended to be encompassed in the scope of the claims of the present invention.
Claims (5)
1. A switching power supply control unit, comprising:
a sample-and-hold module U221, an error amplifier U223, a sawtooth wave generator U224, a PWM comparator U225, a quasi-resonant valley-bottom comparator U242, an NOT gate U243, an NOT gate U227, a valley-bottom lock enabling module U229, a valley-bottom locking module U228, a switch latch U232, a driving circuit U231 and a peak current comparator U230;
the input end of the sample-hold module U221 and the non-inverting input end of the quasi-resonant valley comparator U242 are respectively connected with auxiliary winding voltage division feedback signals (110); the output end of the sample-hold module U221 is connected with the inverting input end of the error amplifier U223, and the non-inverting input end of the error amplifier U223 is used for regulating the voltage signal V th_FB The method comprises the steps of carrying out a first treatment on the surface of the The output signal Comp of the error amplifier U223 is connected to the inverting input terminal of the PWM comparator U225The output of the sawtooth wave generator U224 is connected with the non-inverting input end of the PWM comparator U225; the output end of the PWM comparator U225 is connected with one input end of the NOR gate U227;
the inverting input end of the quasi-resonant valley bottom comparator U242 is connected with the valley bottom discrimination reference signal V th_DEM The method comprises the steps of carrying out a first treatment on the surface of the The output end of the quasi-resonant valley comparator U242 is connected with the other input end of the NOR gate U227 and the input end of the NOR gate U243; the output of the nor gate U227 and the output signal QR of the nor gate U243 are respectively input to the valley lock module U228;
the error amplifier output signal Comp and the power tube switch signal On are respectively input into a valley lock enabling module U229, and a valley lock enabling signal lockEn generated by the valley lock enabling module U229 is input into a valley lock module U228; the power tube switch signal On is input into a valley locking module U228; the power tube conduction trigger signal set output by the output end of the valley locking module U228 is input to the S end of the switch latch U232; the switching latch U232 is an RS trigger, and the R end of the switching latch U232 is connected with the output end of the peak current comparator U230; the non-inverting input end of the peak current comparator U230 is connected with one end of the primary current sampling resistor Rcs, and the inverting input end is connected with the peak current reference signal V th_CS ；
The Q terminal of the switching latch U232 outputs a power tube switching signal On, the power tube switching signal On is input to the input terminal of the driving circuit U231, and the output terminal of the driving circuit U231 is connected to the switching control terminal of the power tube N1.
2. The switching power supply control unit according to claim 1, wherein,
the valley bottom lock enable module U229 includes: MOS switches K321 and K322, an inverter U313, capacitors C323 and C324, an isolation buffer amplifier U331, a positive voltage bias V332, a negative voltage bias V333, hysteresis comparators U334 and U335, a NOR gate U336 and a counter U337;
the power tube switch signal On is connected with the control end of the MOS switch K321 and the input end of the inverter U313; the output signal Comp of the error amplifier U223 is connected with one end of the MOS switch K321, and the other end of the MOS switch K321 is connected with one end of the MOS switch K322 and is grounded through the capacitor C323; the output end of the inverter U313 is connected with the control end of the MOS switch K322, and the other end of the MOS switch K322 is connected with the input end of the isolation buffer amplifier U331 and is grounded through the capacitor C324;
the output end of the isolation buffer amplifier U331 is connected with the inverting end of the hysteresis comparator U334 through a positive voltage bias V332 respectively, and is connected with the non-inverting end of the hysteresis comparator U335 through a negative voltage bias V333; the same phase of the hysteresis comparator U334 is connected with the output signal Comp of the error amplifier U223; the inverse phase of the hysteresis comparator U335 is connected with the output signal Comp of the error amplifier U223; the output ends of the hysteresis comparators U334 and U335 are respectively connected with two input ends of the NOR gate U336; the output of the NOR gate U336 is connected with the reset end of the counter U337, and the clock end of the counter U337 is connected with the power tube switch signal On; the output of the counter U337 outputs a valley lock enable signal LockEn.
3. The switching power supply control unit according to claim 2, wherein,
the valley lock enable signal LockEn is also input to the control terminals of the hysteresis comparators U334, U335, respectively, to increase the hysteresis intervals of the hysteresis comparators U334, U335 when the LockEn signal is high.
4. The switching power supply control unit according to claim 1, wherein,
the valley lock module U228 includes: d flip-flop U411, counter U415, counter U416, digital comparator U417, selector U418, nor gates U412, U413, nor gate U414;
the clock end of the D trigger U411 is connected with the output signal PWM of the NOR gate U227; the valley lock enable signal lockEn is respectively connected with the reset end of the D trigger U411 and the reset end of the counter U415; the D terminal of the D trigger U411 is connected with a high level;
the Q output of the D flip-flop U411 is connected with one input end of the NOR gate U412 and the selection control end of the selector U418; the Q output of the D flip-flop U411 is connected with one input end of the NOR gate U413; the other inputs of nor gates U412 and U413 are connected to the output signal QR of nor gate U243; the output end of the nor gate U412 is connected with the clock end of the counter U415, and the output end of the nor gate U413 is connected with the clock end of the counter U146; the power tube switch signal On is connected with the input end of the NOT gate U414, and the output end of the NOT gate U414 is connected with the reset end of the counter U416; the output ends of the counters U415 and U416 are respectively connected with two input ends of the digital comparator U417; the output end of the digital comparator U417 and the output signal PWM of the NOR gate U227 are respectively connected with two input ends of the selector U418; the output of the selector U148 outputs the power tube on trigger signal ONset.
5. A quasi-resonant switching power supply self-adaptive valley locking circuit comprising:
an input rectifying and filtering circuit, a switching power supply control unit according to any one of claims 1 to 4, a transformer T206, an output rectifying and filtering circuit (207), an output feedback circuit (208), a power tube N1, and a primary current sampling resistor Rcs;
the positive output end of the input rectifying and filtering circuit is connected with the synonym end of the primary winding of the transformer T206, and the negative output end of the input rectifying and filtering circuit is connected with the primary ground;
the primary winding of the transformer T206 is connected with the current input end of the power tube N1 in the same name, the current output end of the power tube N1 is connected with one end of the primary current sampling resistor Rcs, and the other end of the primary current sampling resistor Rcs is connected with primary ground;
the non-inverting input end of the peak current comparator U230 is connected with one end of the primary current sampling resistor Rcs; the output end of the driving circuit U231 is connected with the switch control end of the power tube N1;
the secondary winding of the transformer T206 is connected with an output rectifying and filtering circuit (207), and the DC voltage is output through the output rectifying and filtering circuit (207);
the output feedback circuit (208) comprises an output feedback auxiliary winding of the transformer T206, and two ends of the output feedback auxiliary winding are connected with resistors R1 and R2 in series; obtaining an auxiliary winding voltage division feedback signal (110) from the connection point of the series resistors R1 and R2; the auxiliary winding voltage division feedback signal (110) is connected with the input end of the sample-hold module U221 and the non-inverting input end of the quasi-resonant valley-bottom comparator U242.
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| CN111565048B (en) * | 2020-06-15 | 2023-05-12 | 深圳职业技术学院 | Logic control system of successive approximation type ADC |
| CN111884494B (en) * | 2020-07-23 | 2021-11-12 | 成都启臣微电子股份有限公司 | Quasi-resonance valley bottom conduction circuit with compensation function |
| CN112332647B (en) * | 2020-11-11 | 2024-07-05 | 富满微电子集团股份有限公司 | Valley locking circuit, chip and power supply based on quasi-resonance control technology |
| CN112701924B (en) | 2020-12-28 | 2022-07-08 | 昂宝电子（上海）有限公司 | Apparatus and method for valley lock in quasi-resonant switching power supplies |
| CN117134617A (en) * | 2022-05-20 | 2023-11-28 | 深圳英集芯科技股份有限公司 | Switching power supply and related charger |
| CN115065254B (en) * | 2022-08-19 | 2022-12-20 | 深圳英集芯科技股份有限公司 | Control device and method of flyback switching power supply and charger |
| CN116388552B (en) * | 2023-06-07 | 2023-09-19 | 梵塔半导体技术(杭州)有限公司 | Switching circuit control method, control chip and switching circuit |
| CN117458889B (en) * | 2023-12-22 | 2024-03-22 | 无锡硅动力微电子股份有限公司 | Flyback switching power supply control circuit |
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