CN102684460B - Frequency soft clamp system for quasi-resonant switching power supply and method - Google Patents
Frequency soft clamp system for quasi-resonant switching power supply and method Download PDFInfo
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Abstract
The invention discloses a frequency soft clamp system for a quasi-resonant switching power supply and a method. The system is used for selecting a certain valley bottom where a power switch within a subsequent set time range is locked for switch-on through detecting the switching frequency within a set time range to achieve the effects that the switching frequency is limited within a certain range, and the power switch is locked in the certain valley bottom for switch-on within the set time range. The frequency soft clamp system for the quasi-resonant switching power supply and the method, which are disclosed by the invention, have the benefits that the power switch can be effectively prevented from being switched on between adjacent two valley bottoms in turn and is locked in the certain valley bottom for switch on within the certain time range, so that the audio frequency noise is effectively avoided, and the switching frequency is limited within the certain range.
Description
Technical field
The invention belongs to integrated circuit art field, relate to a kind of Quasi-resonant switching power supply, relate in particular to a kind of frequency soft clamping system for Quasi-resonant switching power supply; Meanwhile, the invention still further relates to a kind of frequency soft clamping method for Quasi-resonant switching power supply.
Background technology
Along with the development of miniaturization day by day and computer, communication industry and the aerospace etc. of electronic equipment, the requirement of power supply is also improved day by day, the miniaturization of power supply and high frequency have changed into the inevitable development trend of power supply.In the process of Switching Power Supply miniaturization and high frequency, switching loss is a key factor of its development of restriction.The switching loss of tradition pulse-width adjustment Switching Power Supply in the time of high-frequency work can not further improve its switching frequency, thereby volume can not reduce.In recent years, the various soft switch techniques that reduce HF switch loss have been subject to people's favor, and soft switch technique makes HF switch pipe be operated in zero switching state, thereby has greatly reduced switching loss, has improved the efficiency of switch converters.Quasi-resonant switching technology combines the advantage of harmonic technology and PWM technology, has represented a developing direction of Switching Power Supply.
The advantage of quasi-resonant switching has comprised reduction conduction loss, reduces and increases but shortcoming is frequency with load.The turn-off power loss of transducer becomes seriously with the increase of frequency, and especially in the time of underloading, above-mentioned effect can lower efficiency.General quasi-resonant switching has adopted a kind of " frequency clamper " to make up the intrinsic this defect of quasi-resonance controller.Controller need to be waited for the shortest time, corresponding peak frequency, and then switch conducting in the time of next trough, this method can improve the efficiency under underloading.
Fig. 1 has shown a quasi resonant convertor system that is widely used in Switching Power Supply, turns direct current (DC) for exchanging (AC).This system comprises: front end electromagnetic interface filter, full-bridge rectification, power controller, transformer, auxiliary winding divider resistance, primary side MOS switch and current sense resistor, secondary commutation filtering, and isolation feedback compensation network.
Fig. 2 has shown a Quasi-resonant switching power supply controller that adopts traditional hard pincers frequently to control that can be applied in Fig. 1, and main modular comprises: PWM comparator, lead-edge-blanking, the lowest point detector, pincers timer, rest-set flip-flop frequently, and driving stage.The lowest point detector is used for detecting the lowest point of the free LC harmonic wave of the parasitic capacitance of main inductance and power switch after transformer demagnetization, and the lowest point detector is in the lowest point of this harmonic wave or approach the pulse signal of moment output of the lowest point.Pincers are timer frequently, timing in the time that power switch is opened at every turn, and meter, to special time output signal, allows the lowest point detector to trigger rest-set flip-flop, thereby again opens power switch.
But the Quasi-resonant switching power supply controller that the traditional hard pincers of this employing are controlled frequently, in the time of pincers frequency, be very easy in turn in adjacent two the lowest point conductings (as shown in Figure 3), switching frequency changes violent, thereby produces the spectrum component of audio frequency, so very easily produce audio-frequency noise.
Summary of the invention
Technical problem to be solved by this invention is: a kind of frequency soft clamping system for Quasi-resonant switching power supply is provided, can effectively avoid audio-frequency noise, and switching frequency is limited to certain scope.
In addition, the present invention also provides a kind of frequency soft clamping method for Quasi-resonant switching power supply, can effectively avoid audio-frequency noise, and switching frequency is limited to certain scope.
For solving the problems of the technologies described above, the present invention adopts following technical scheme:
A kind of frequency soft clamping system for Quasi-resonant switching power supply, described system is by detecting the switching frequency within the scope of setting-up time, select follow-up setting-up time scope internal power switch lock and fix on certain the lowest point conducting, be limited to certain scope and in setting-up time, be locked in certain the lowest point conducting to reach switching frequency.
As a preferred embodiment of the present invention, described frequency soft clamping system comprises:
The lowest point detector, in order to detect the lowest point of the free LC harmonic wave of the parasitic capacitance of main inductance and power switch after transformer demagnetization, the lowest point detector is in the lowest point of this harmonic wave or approach the pulse signal of moment output of the lowest point;
Controller is selected in the lowest point, in order to by detecting the switching frequency within the scope of setting-up time, characterizes and need open trigger signal generator to a power switch in the control signal of which the lowest point conducting in follow-up setting-up time scope output;
Power switch is opened trigger signal generator, in order to according to the output of the selected controller of the output of described the lowest point detector and the lowest point, selectes the selected the lowest point output triggering signal of controller in the lowest point, opens in order to trigger power switch.
As a preferred embodiment of the present invention, described frequency soft clamping system comprises:
Oscillator, with thinking that bidirectional counter provides clock signal;
First frequency comparator, whether the frequency that is used for adjudicating Gate port is lower than first frequency signal f_ref_L; Gate port, for driving signal output port, is used for driving power switch, the conducting of power ratio control switch and closing;
Second frequency comparator, in order to the frequency of adjudicating Gate port whether higher than second frequency signal f_ref_H;
Soft pincers are bidirectional counter frequently, in order to according to second frequency comparator and the output of first frequency comparator, starts its output carry out or add one or subtract an operation in each clock cycle; If all receive the sign frequency that is second frequency comparator higher than the signal of second frequency signal f_ref_H within the whole clock cycle, start the output of bidirectional counter frequently of soft pincers in the next cycle so and add an operation; If the sign frequency that at least receives a first frequency comparator within the whole clock cycle is less than the signal of first frequency signal f_ref_L, starts the output of bidirectional counter frequently of soft pincers in the next cycle so and subtract an operation;
The lowest point detector, in order to detect the lowest point of the free LC harmonic wave of the parasitic capacitance of main inductance and power switch after transformer demagnetization, the lowest point detector is in the lowest point of this harmonic wave or approach the pulse signal of moment output of the lowest point;
Power switch is opened trigger signal generator, in order to according to the output of the lowest point detector and the output of bidirectional counter frequently of soft pincers, when in the soft pincers bidirectional counter output valve corresponding the lowest point moment frequently, exports a triggering number, opens in order to trigger power switch.
As a preferred embodiment of the present invention, described frequency soft clamping system comprises:
N frequency divider, in order to the input signal of Gate port is carried out to frequency division N time, frequency division output signal provides clock signal as bidirectional counter;
First frequency comparator, in order to the frequency of adjudicating Gate port whether lower than first frequency signal f_ref_L; Gate port, for driving signal output port, is used for driving power switch, the conducting of power ratio control switch and closing;
Second frequency comparator, in order to the frequency of adjudicating Gate port whether higher than second frequency signal f_ref_H;
Soft pincers frequently bidirectional counter, according to second frequency comparator and the output of first frequency comparator, start its output in each clock cycle and carry out or add one or subtract an operation; If all receive the sign frequency that is second frequency comparator higher than the signal of second frequency signal f_ref_H within the whole clock cycle, start the output of bidirectional counter frequently of soft pincers in the next cycle so and add an operation; If the sign frequency that at least receives a first frequency comparator within the whole clock cycle is less than the signal of first frequency signal f_ref_L, starts the output of bidirectional counter frequently of soft pincers in the next cycle so and subtract an operation;
The lowest point detector is used for detecting the lowest point of the free LC harmonic wave of the parasitic capacitance of main inductance and power switch after transformer demagnetization, and the lowest point detector is in the lowest point of this harmonic wave or approach the pulse signal of moment output of the lowest point;
Power switch is opened trigger signal generator according to the output of the lowest point detector and the output of bidirectional counter frequently of soft pincers, when in the soft pincers bidirectional counter output valve corresponding the lowest point moment frequently, exports a triggering number, opens in order to trigger power switch.
As a preferred embodiment of the present invention, described frequency soft clamping system comprises:
Reference frequency generator, in order to according to the input signal of FB port, for first frequency comparator and second frequency comparator provide reference signal first frequency signal f_ref_L, second frequency signal f_ref_H, reference signal first frequency signal f_ref_L, second frequency signal f_ref_H are subject to FB port controlling; FB port is feedback port, in order to receiving feedback signals;
N frequency divider, in order to the input signal of Gate port is carried out to frequency division N time, frequency division output signal provides clock signal as bidirectional counter; Gate port, for driving signal output port, is used for driving power switch, the conducting of power ratio control switch and closing;
First frequency comparator, in order to the frequency of adjudicating Gate port whether lower than first frequency signal f_ref_L;
Second frequency comparator, in order to the frequency of adjudicating Gate port whether higher than second frequency signal f_ref_H;
Soft pincers are bidirectional counter frequently, in order to according to second frequency comparator and the output of first frequency comparator, starts its output carry out or add one or subtract an operation in each clock cycle; If all receive the sign frequency that is second frequency comparator higher than the signal of second frequency signal f_ref_H within the whole clock cycle, start the output of bidirectional counter frequently of soft pincers in the next cycle so and add an operation; If the sign frequency that at least receives a first frequency comparator within the whole clock cycle is less than the signal of first frequency signal f_ref_L, starts the output of bidirectional counter frequently of soft pincers in the next cycle so and subtract an operation;
The lowest point detector, in order to detect the lowest point of the free LC harmonic wave of the parasitic capacitance of main inductance and power switch after transformer demagnetization, the lowest point detector is in the lowest point of this harmonic wave or approach the pulse signal of moment output of the lowest point;
Power switch is opened trigger signal generator, in order to according to the output of the lowest point detector and the output of bidirectional counter frequently of soft pincers, when in the soft pincers bidirectional counter output valve corresponding the lowest point moment frequently, exports a triggering number, opens in order to trigger power switch.
As a preferred embodiment of the present invention, described frequency soft clamping system comprises: PWM comparator, lead-edge-blanking, rest-set flip-flop, overcurrent protector, soft start, driving stage, reference frequency generator, N frequency divider, first frequency comparator, second frequency comparator, bidirectional counter, the lowest point detector, power switch is opened trigger signal generator;
Reference frequency generator is according to the input signal of FB port, for first frequency comparator and second frequency comparator provide reference signal first frequency signal f_ref_L, second frequency signal f_ref_H, reference signal first frequency signal f_ref_L, second frequency signal f_ref_H are subject to FB port controlling; FB port is feedback port, in order to receiving feedback signals;
N time frequency divider carries out frequency division N time to the input signal of Gate port, and frequency division output signal provides clock signal as bidirectional counter; Gate port, for driving signal output port, is used for driving power switch, the conducting of power ratio control switch and closing;
Whether the frequency that first frequency comparator is used for adjudicating Gate is lower than first frequency signal f_ref_L;
Whether the frequency that second frequency comparator is used for adjudicating Gate is higher than second frequency signal f_ref_H;
Soft pincers frequently bidirectional counter, according to second frequency comparator and the output of first frequency comparator, start its output in each clock cycle and carry out or add one or subtract an operation; If all receive the sign frequency that is second frequency comparator higher than the signal of second frequency signal f_ref_H within the whole clock cycle, start the output of bidirectional counter frequently of soft pincers in the next cycle and add an operation; If the sign frequency that at least receives a first frequency comparator within the whole clock cycle is less than the signal of first frequency signal f_ref_L, starts the output of bidirectional counter frequently of soft pincers in the next cycle and subtract an operation;
The lowest point detector is used for detecting the lowest point of the free LC harmonic wave of the parasitic capacitance of main inductance and power switch after transformer demagnetization, and the lowest point detector is in the lowest point of this harmonic wave or approach the pulse signal of moment output of the lowest point;
Power switch is opened trigger signal generator according to the output of the lowest point detector and the output of bidirectional counter frequently of soft pincers, when in the soft pincers bidirectional counter output valve corresponding the lowest point moment frequently, exports a triggering number, opens in order to trigger power switch.
A kind of frequency soft clamping method for Quasi-resonant switching power supply, described method is by detecting the switching frequency within the scope of setting-up time, select follow-up setting-up time scope internal power switch lock and fix on certain the lowest point conducting, be limited to certain scope and in setting-up time, be locked in certain the lowest point conducting to reach switching frequency.
As a preferred embodiment of the present invention, described frequency soft clamping method comprises the steps:
The lowest point detector detects the lowest point of main inductance and the free LC harmonic wave of the parasitic capacitance of power switch after transformer demagnetization, the lowest point detector in the lowest point of this harmonic wave or the moment that approaches the lowest point export a pulse signal;
The selected controller in the lowest point, by detecting the switching frequency within the scope of setting-up time, characterizes and need open trigger signal generator to a power switch in the control signal of which the lowest point conducting in follow-up setting-up time scope output;
Power switch is opened trigger signal generator according to the output of the selected controller of the output of described the lowest point detector and the lowest point, and in the lowest point, the selected the lowest point output triggering signal of selected controller, opens in order to trigger power switch.
As a preferred embodiment of the present invention, described frequency soft clamping method comprises the steps:
Oscillator provides clock signal for bidirectional counter;
Whether the frequency of first frequency comparator decision Gate port is lower than first frequency signal f_ref_L; Gate port, for driving signal output port, is used for driving power switch, the conducting of power ratio control switch and closing;
Whether the frequency of second frequency comparator decision Gate port is higher than second frequency signal f_ref_H;
Soft pincers frequently bidirectional counter, according to second frequency comparator and the output of first frequency comparator, start its output in each clock cycle and carry out or add one or subtract an operation; If all receive the sign frequency that is second frequency comparator higher than the signal of second frequency signal f_ref_H within the whole clock cycle, start the output of bidirectional counter frequently of soft pincers in the next cycle so and add an operation; If the sign frequency that at least receives a first frequency comparator within the whole clock cycle is less than the signal of first frequency signal f_ref_L, starts the output of bidirectional counter frequently of soft pincers in the next cycle so and subtract an operation;
The lowest point detector detects the lowest point of main inductance and the free LC harmonic wave of the parasitic capacitance of power switch after transformer demagnetization, the lowest point detector in the lowest point of this harmonic wave or the moment that approaches the lowest point export a pulse signal;
Power switch is opened trigger signal generator according to the output of the lowest point detector and the output of bidirectional counter frequently of soft pincers, when in the soft pincers bidirectional counter output valve corresponding the lowest point moment frequently, exports a triggering number, opens in order to trigger power switch.
As a preferred embodiment of the present invention, described frequency soft clamping method comprises the steps:
N time frequency divider carries out frequency division N time to the input signal of Gate port, and frequency division output signal provides clock signal as bidirectional counter; Gate port, for driving signal output port, is used for driving power switch, the conducting of power ratio control switch and closing;
Whether the frequency of first frequency comparator decision Gate port is lower than first frequency signal f_ref_L;
Whether the frequency of second frequency comparator decision Gate port is higher than second frequency signal f_ref_H;
Soft pincers frequently bidirectional counter, according to second frequency comparator and the output of first frequency comparator, start its output in each clock cycle and carry out or add one or subtract an operation; If all receive the sign frequency that is second frequency comparator higher than the signal of second frequency signal f_ref_H within the whole clock cycle, start the output of bidirectional counter frequently of soft pincers in the next cycle so and add an operation; If the sign frequency that at least receives a first frequency comparator within the whole clock cycle is less than the signal of first frequency signal f_ref_L, starts the output of bidirectional counter frequently of soft pincers in the next cycle so and subtract an operation;
The lowest point detector is used for detecting the lowest point of the free LC harmonic wave of the parasitic capacitance of main inductance and power switch after transformer demagnetization, and the lowest point detector is in the lowest point of this harmonic wave or approach the pulse signal of moment output of the lowest point;
Power switch is opened trigger signal generator according to the output of the lowest point detector and the output of bidirectional counter frequently of soft pincers, when in the soft pincers bidirectional counter output valve corresponding the lowest point moment frequently, exports a triggering number, opens in order to trigger power switch.
As a preferred embodiment of the present invention, described frequency soft clamping method comprises the steps:
Reference frequency generator is according to the input signal of FB port, for first frequency comparator and second frequency comparator provide reference signal first frequency signal f_ref_L, second frequency signal f_ref_H, reference signal first frequency signal f_ref_L, second frequency signal f_ref_H are subject to FB port controlling; FB port is feedback port, in order to receiving feedback signals;
N time frequency divider carries out frequency division N time to the input signal of Gate port, and frequency division output signal provides clock signal as bidirectional counter; Gate port, for driving signal output port, is used for driving power switch, the conducting of power ratio control switch and closing;
Whether the frequency of first frequency comparator decision Gate port is lower than first frequency signal f_ref_L;
Whether the frequency of second frequency comparator decision Gate port is higher than second frequency signal f_ref_H;
Soft pincers frequently bidirectional counter, according to second frequency comparator and the output of first frequency comparator, start its output in each clock cycle and carry out or add one or subtract an operation; If all receive the sign frequency that is second frequency comparator higher than the signal of second frequency signal f_ref_H within the whole clock cycle, start the output of bidirectional counter frequently of soft pincers in the next cycle so and add an operation; If the sign frequency that at least receives a first frequency comparator within the whole clock cycle is less than the signal of first frequency signal f_ref_L, starts the output of bidirectional counter frequently of soft pincers in the next cycle so and subtract an operation;
The lowest point detector detects the lowest point of main inductance and the free LC harmonic wave of the parasitic capacitance of power switch after transformer demagnetization, the lowest point detector in the lowest point of this harmonic wave or the moment that approaches the lowest point export a pulse signal;
Power switch is opened trigger signal generator according to the output of the lowest point detector and the output of bidirectional counter frequently of soft pincers, when in the soft pincers bidirectional counter output valve corresponding the lowest point moment frequently, exports a triggering number, opens in order to trigger power switch.
As a preferred embodiment of the present invention, described frequency soft clamping method comprises the steps:
Reference frequency generator is according to the input signal of FB port, for first frequency comparator and second frequency comparator provide reference signal first frequency signal f_ref_L, second frequency signal f_ref_H, reference signal first frequency signal f_ref_L, second frequency signal f_ref_H are subject to FB port controlling;
N time frequency divider carries out frequency division N time to the input signal of Gate port, and frequency division output signal provides clock signal as bidirectional counter;
Whether the frequency of first frequency comparator decision Gate is lower than first frequency signal f_ref_L;
Whether the frequency of second frequency comparator decision Gate is higher than second frequency signal f_ref_H;
Soft pincers frequently bidirectional counter, according to second frequency comparator and the output of first frequency comparator, start its output in each clock cycle and carry out or add one or subtract an operation; If all receive the sign frequency that is second frequency comparator higher than the signal of second frequency signal f_ref_H within the whole clock cycle, start the output of bidirectional counter frequently of soft pincers in the next cycle and add an operation; If the sign frequency that at least receives a first frequency comparator within the whole clock cycle is less than the signal of first frequency signal f_ref_L, starts the output of bidirectional counter frequently of soft pincers in the next cycle and subtract an operation;
The lowest point detector detects the lowest point of main inductance and the free LC harmonic wave of the parasitic capacitance of power switch after transformer demagnetization, the lowest point detector in the lowest point of this harmonic wave or the moment that approaches the lowest point export a pulse signal;
Power switch is opened trigger signal generator according to the output of the lowest point detector and the output of bidirectional counter frequently of soft pincers, when in the soft pincers bidirectional counter output valve corresponding the lowest point moment frequently, exports a triggering number, opens in order to trigger power switch.
Beneficial effect of the present invention is: the frequency soft clamping system and method for Quasi-resonant switching power supply that the present invention proposes, can effectively avoid power switch in turn in two adjacent the lowest point conductings, within the scope of certain hour, be locked in certain the lowest point conducting, thereby effectively avoided audio-frequency noise, and switching frequency is limited to certain scope.
Brief description of the drawings
Fig. 1 is the circuit diagram that is widely used in the quasi resonant convertor system of Switching Power Supply.
Fig. 2 adopts traditional hard pincers circuit diagram of the Quasi-resonant switching power supply controller of control frequently.
Fig. 3 is traditional hard frequency control mode schematic diagram in two adjacent the lowest point conductings in the time of pincers frequency that clamps.
Fig. 4 is the circuit diagram of the present invention for the frequency soft clamping system of Quasi-resonant switching power supply.
Fig. 5 is embodiment bis-medium frequency soft clamping systems circuit diagrams in one application.
Fig. 6 is embodiment tri-medium frequency soft clamping systems circuit diagrams in one application.
Fig. 7 is embodiment tetra-medium frequency soft clamping systems circuit diagrams in one application.
Fig. 8 is embodiment five medium frequency soft clamping systems circuit diagrams in one application.
Embodiment
Describe the preferred embodiments of the present invention in detail below in conjunction with accompanying drawing.
Embodiment mono-
The present invention has disclosed a kind of frequency soft clamping system for Quasi-resonant switching power supply, by detecting the switching frequency of (as comprising one or more time cycles) within the scope of certain hour, select next time range and (as comprise one or more time cycles, can be identical or different with the time range detecting) internal power switch lock fixes on certain the lowest point conducting, thereby reaches the object that switching frequency is limited to certain scope and is locked within a certain period of time certain the lowest point conducting.
Refer to Fig. 4, described frequency soft clamping system comprises that controller is selected in the lowest point detector, the lowest point, power switch is opened trigger signal generator.Wherein, the lowest point detector is used for detecting the lowest point of the free LC harmonic wave of the parasitic capacitance of main inductance and power switch after transformer demagnetization, and the lowest point detector is in the lowest point of this harmonic wave or approach the pulse signal of moment output of the lowest point.The selected controller in the lowest point is by detecting the switching frequency within the scope of certain hour, under time range output characterize and need open trigger signal generator to power switch in the control signal of which the lowest point conducting.Power switch is opened trigger signal generator according to the output of the selected controller of the output of the lowest point detector and the lowest point, and in the lowest point, the selected the lowest point output triggering signal of selected controller, opens in order to trigger power switch.
The present invention also discloses a kind of frequency soft clamping method for Quasi-resonant switching power supply, and described frequency soft clamping method comprises the steps:
The lowest point detector detects the lowest point of main inductance and the free LC harmonic wave of the parasitic capacitance of power switch after transformer demagnetization, the lowest point detector in the lowest point of this harmonic wave or the moment that approaches the lowest point export a pulse signal;
The selected controller in the lowest point, by detecting the switching frequency within the scope of setting-up time, characterizes and need open trigger signal generator to a power switch in the control signal of which the lowest point conducting in follow-up setting-up time scope output;
Power switch is opened trigger signal generator according to the output of the selected controller of the output of described the lowest point detector and the lowest point, and in the lowest point, the selected the lowest point output triggering signal of selected controller, opens in order to trigger power switch.
Embodiment bis-
Refer to Fig. 5, Fig. 5 is a specific embodiment according to thought of the present invention.This frequency soft clamping system that is used for Quasi-resonant switching power supply comprises: oscillator, and frequency comparator-L, frequency comparator-H, bidirectional counter, the lowest point detector, power switch is opened trigger signal generator.
Oscillator provides clock signal for bidirectional counter.Whether the frequency that frequency comparator-L is used for adjudicating Gate port is lower than f_ref_L.Whether the frequency that frequency comparator-H is used for adjudicating Gate port is higher than f_ref_H.Gate port, for driving signal output port, is used for driving power switch, the conducting of power ratio control switch and closing.Soft pincers frequently bidirectional counter, according to frequency comparator-H and frequency comparator-L output, start its output in each clock cycle and carry out or add one or subtract an operation; If all receive the sign frequency that is frequency comparator-H higher than the signal of f_ref_H within the whole clock cycle, start the output of bidirectional counter frequently of soft pincers in the next cycle so and add an operation; If the sign frequency that at least receives a frequency comparator-L within the whole clock cycle is less than the signal of f_ref_L, starts the output of bidirectional counter frequently of soft pincers in the next cycle so and subtract an operation.The lowest point detector is used for detecting the lowest point of the free LC harmonic wave of the parasitic capacitance of main inductance and power switch after transformer demagnetization, and the lowest point detector is in the lowest point of this harmonic wave or approach the pulse signal of moment output of the lowest point.Power switch is opened trigger signal generator according to the output of the lowest point detector and the output of bidirectional counter frequently of soft pincers, when in the soft pincers bidirectional counter output valve corresponding the lowest point moment frequently, exports a triggering number, opens in order to trigger power switch.
The present invention also discloses a kind of frequency soft clamping method for Quasi-resonant switching power supply, and described frequency soft clamping method comprises the steps:
Oscillator provides clock signal for bidirectional counter;
Whether the frequency of first frequency comparator decision Gate port is lower than first frequency signal f_ref_L; Gate port, for driving signal output port, is used for driving power switch, the conducting of power ratio control switch and closing.
Whether the frequency of second frequency comparator decision Gate port is higher than second frequency signal f_ref_H;
Soft pincers frequently bidirectional counter, according to second frequency comparator and the output of first frequency comparator, start its output in each clock cycle and carry out or add one or subtract an operation; If all receive the sign frequency that is second frequency comparator higher than the signal of second frequency signal f_ref_H within the whole clock cycle, start the output of bidirectional counter frequently of soft pincers in the next cycle so and add an operation; If the sign frequency that at least receives a first frequency comparator within the whole clock cycle is less than the signal of first frequency signal f_ref_L, starts the output of bidirectional counter frequently of soft pincers in the next cycle so and subtract an operation;
The lowest point detector detects the lowest point of main inductance and the free LC harmonic wave of the parasitic capacitance of power switch after transformer demagnetization, the lowest point detector in the lowest point of this harmonic wave or the moment that approaches the lowest point export a pulse signal;
Power switch is opened trigger signal generator according to the output of the lowest point detector and the output of bidirectional counter frequently of soft pincers, when in the soft pincers bidirectional counter output valve corresponding the lowest point moment frequently, exports a triggering number, opens in order to trigger power switch.
Embodiment tri-
Fig. 6 is another specific embodiment according to thought of the present invention.This frequency soft clamping system that is used for Quasi-resonant switching power supply comprises: N frequency divider, and frequency comparator-L, frequency comparator-H, bidirectional counter, the lowest point detector, power switch is opened trigger signal generator.
N time frequency divider carries out frequency division N time to the input signal of Gate port, and frequency division output signal provides clock signal as bidirectional counter.Gate port, for driving signal output port, is used for driving power switch, the conducting of power ratio control switch and closing.Whether the frequency that frequency comparator-L is used for adjudicating Gate is lower than f_ref_L.Whether the frequency that frequency comparator-H is used for adjudicating Gate is higher than f_ref_H.Soft pincers frequently bidirectional counter, according to frequency comparator-H and frequency comparator-L output, start its output in each clock cycle and carry out or add one or subtract an operation; If all receive the sign frequency that is frequency comparator-H higher than the signal of f_ref_H within the whole clock cycle, start the output of bidirectional counter frequently of soft pincers in the next cycle so and add an operation; If the sign frequency that at least receives a frequency comparator-L within the whole clock cycle is less than the signal of f_ref_L, starts the output of bidirectional counter frequently of soft pincers in the next cycle so and subtract an operation.The lowest point detector is used for detecting the lowest point of the free LC harmonic wave of the parasitic capacitance of main inductance and power switch after transformer demagnetization, and the lowest point detector is in the lowest point of this harmonic wave or approach the pulse signal of moment output of the lowest point.Power switch is opened trigger signal generator according to the output of the lowest point detector and the output of bidirectional counter frequently of soft pincers, when in the soft pincers bidirectional counter output valve corresponding the lowest point moment frequently, exports a triggering number, opens in order to trigger power switch.
The present invention also discloses a kind of frequency soft clamping method for Quasi-resonant switching power supply, and described frequency soft clamping method comprises the steps:
N time frequency divider carries out frequency division N time to the input signal of Gate port, and frequency division output signal provides clock signal as bidirectional counter; Gate port, for driving signal output port, is used for driving power switch, the conducting of power ratio control switch and closing.
Whether the frequency of first frequency comparator decision Gate port is lower than first frequency signal f_ref_L;
Whether the frequency of second frequency comparator decision Gate port is higher than second frequency signal f_ref_H;
Soft pincers frequently bidirectional counter, according to second frequency comparator and the output of first frequency comparator, start its output in each clock cycle and carry out or add one or subtract an operation; If all receive the sign frequency that is second frequency comparator higher than the signal of second frequency signal f_ref_H within the whole clock cycle, start the output of bidirectional counter frequently of soft pincers in the next cycle so and add an operation; If the sign frequency that at least receives a first frequency comparator within the whole clock cycle is less than the signal of first frequency signal f_ref_L, starts the output of bidirectional counter frequently of soft pincers in the next cycle so and subtract an operation;
The lowest point detector is used for detecting the lowest point of the free LC harmonic wave of the parasitic capacitance of main inductance and power switch after transformer demagnetization, and the lowest point detector is in the lowest point of this harmonic wave or approach the pulse signal of moment output of the lowest point;
Power switch is opened trigger signal generator according to the output of the lowest point detector and the output of bidirectional counter frequently of soft pincers, when in the soft pincers bidirectional counter output valve corresponding the lowest point moment frequently, exports a triggering number, opens in order to trigger power switch.
Embodiment tetra-
Fig. 7 is another specific embodiment of inventing according to thought of the present invention.This system comprises: reference frequency generator, and N frequency divider, frequency comparator-L, frequency comparator-H, bidirectional counter, the lowest point detector, power switch is opened trigger signal generator.
Reference frequency generator is according to the input signal of FB port, and for frequency comparator-H and frequency comparator-L provide reference signal f_ref_L, f_ref_H, reference signal f_ref_L, f_ref_H are controlled by FB.FB port is feedback port, in order to receiving feedback signals; Conventionally receive optocoupler, receive the feedback signal of being sent by optocoupler.N time frequency divider carries out frequency division N time to the input signal of Gate, and frequency division output signal provides clock signal as bidirectional counter.Whether the frequency that frequency comparator-L is used for adjudicating Gate port is lower than f_ref_L.Whether the frequency that frequency comparator-H is used for adjudicating Gate port is higher than f_ref_H.Gate port, for driving signal output port, is used for driving power switch, the conducting of power ratio control switch and closing.Soft pincers frequently bidirectional counter, according to frequency comparator-H and frequency comparator-L output, start its output in each clock cycle and carry out or add one or subtract an operation; If all receive the sign frequency that is frequency comparator-H higher than the signal of f_ref_H within the whole clock cycle, start the output of bidirectional counter frequently of soft pincers in the next cycle so and add an operation; If the sign frequency that at least receives a frequency comparator-L within the whole clock cycle is less than the signal of f_ref_L, starts the output of bidirectional counter frequently of soft pincers in the next cycle so and subtract an operation.The lowest point detector is used for detecting the lowest point of the free LC harmonic wave of the parasitic capacitance of main inductance and power switch after transformer demagnetization, and the lowest point detector is in the lowest point of this harmonic wave or approach the pulse signal of moment output of the lowest point.Power switch is opened trigger signal generator according to the output of the lowest point detector and the output of bidirectional counter frequently of soft pincers, when in the soft pincers bidirectional counter output valve corresponding the lowest point moment frequently, exports a triggering number, opens in order to trigger power switch.
The present invention also discloses a kind of frequency soft clamping method for Quasi-resonant switching power supply, and described frequency soft clamping method comprises the steps:
Reference frequency generator is according to the input signal of FB port, for first frequency comparator and second frequency comparator provide reference signal first frequency signal f_ref_L, second frequency signal f_ref_H, reference signal first frequency signal f_ref_L, second frequency signal f_ref_H are subject to FB port controlling;
N time frequency divider carries out frequency division N time to the input signal of Gate port, and frequency division output signal provides clock signal as bidirectional counter;
Whether the frequency of first frequency comparator decision Gate port is lower than first frequency signal f_ref_L;
Whether the frequency of second frequency comparator decision Gate port is higher than second frequency signal f_ref_H;
Soft pincers frequently bidirectional counter, according to second frequency comparator and the output of first frequency comparator, start its output in each clock cycle and carry out or add one or subtract an operation; If all receive the sign frequency that is second frequency comparator higher than the signal of second frequency signal f_ref_H within the whole clock cycle, start the output of bidirectional counter frequently of soft pincers in the next cycle so and add an operation; If the sign frequency that at least receives a first frequency comparator within the whole clock cycle is less than the signal of first frequency signal f_ref_L, starts the output of bidirectional counter frequently of soft pincers in the next cycle so and subtract an operation;
The lowest point detector detects the lowest point of main inductance and the free LC harmonic wave of the parasitic capacitance of power switch after transformer demagnetization, the lowest point detector in the lowest point of this harmonic wave or the moment that approaches the lowest point export a pulse signal;
Power switch is opened trigger signal generator according to the output of the lowest point detector and the output of bidirectional counter frequently of soft pincers, when in the soft pincers bidirectional counter output valve corresponding the lowest point moment frequently, exports a triggering number, opens in order to trigger power switch.
Embodiment five
Fig. 8 is another specific embodiment of inventing according to the thought of figure tetra-.This system comprises: PWM comparator, lead-edge-blanking, rest-set flip-flop, overcurrent protector, soft start, driving stage, reference frequency generator, N frequency divider, frequency comparator-L; frequency comparator-H; bidirectional counter, the lowest point detector, power switch is opened trigger signal generator.
Reference frequency generator is according to the input signal of FB, and for frequency comparator-H and frequency comparator-L provide reference signal f_ref_L, f_ref_H, reference signal f_ref_L, f_ref_H are controlled by FB.FB port is feedback port, in order to receiving feedback signals; Conventionally receive optocoupler, receive the feedback signal of being sent by optocoupler.N time frequency divider carries out frequency division N time to the input signal of Gate port, and frequency division output signal provides clock signal as bidirectional counter.Whether the frequency that frequency comparator-L is used for adjudicating Gate is lower than f_ref_L.Whether the frequency that frequency comparator-H is used for adjudicating Gate port is higher than f_ref_H.Gate port, for driving signal output port, is used for driving power switch, the conducting of power ratio control switch and closing.Soft pincers frequently bidirectional counter, according to frequency comparator-H and frequency comparator-L output, start its output in each clock cycle and carry out or add one or subtract an operation; If all receive the sign frequency that is frequency comparator-H higher than the signal of f_ref_H within the whole clock cycle, start the output of bidirectional counter frequently of soft pincers in the next cycle so and add an operation; If the sign frequency that at least receives a frequency comparator-L within the whole clock cycle is less than the signal of f_ref_L, starts the output of bidirectional counter frequently of soft pincers in the next cycle so and subtract an operation.The lowest point detector is used for detecting the lowest point of the free LC harmonic wave of the parasitic capacitance of main inductance and power switch after transformer demagnetization, and the lowest point detector is in the lowest point of this harmonic wave or approach the pulse signal of moment output of the lowest point.Power switch is opened trigger signal generator according to the output of the lowest point detector and the output of bidirectional counter frequently of soft pincers, when in the soft pincers bidirectional counter output valve corresponding the lowest point moment frequently, exports a triggering number, opens in order to trigger power switch.
The present invention also discloses a kind of frequency soft clamping method for Quasi-resonant switching power supply, and described frequency soft clamping method comprises the steps:
Reference frequency generator is according to the input signal of FB port, for first frequency comparator and second frequency comparator provide reference signal first frequency signal f_ref_L, second frequency signal f_ref_H, reference signal first frequency signal f_ref_L, second frequency signal f_ref_H are subject to FB port controlling;
N time frequency divider carries out frequency division N time to the input signal of Gate port, and frequency division output signal provides clock signal as bidirectional counter;
Whether the frequency of first frequency comparator decision Gate is lower than first frequency signal f_ref_L;
Whether the frequency of second frequency comparator decision Gate is higher than second frequency signal f_ref_H;
Soft pincers frequently bidirectional counter, according to second frequency comparator and the output of first frequency comparator, start its output in each clock cycle and carry out or add one or subtract an operation; If all receive the sign frequency that is second frequency comparator higher than the signal of second frequency signal f_ref_H within the whole clock cycle, start the output of bidirectional counter frequently of soft pincers in the next cycle and add an operation; If the sign frequency that at least receives a first frequency comparator within the whole clock cycle is less than the signal of first frequency signal f_ref_L, starts the output of bidirectional counter frequently of soft pincers in the next cycle and subtract an operation;
The lowest point detector detects the lowest point of main inductance and the free LC harmonic wave of the parasitic capacitance of power switch after transformer demagnetization, the lowest point detector in the lowest point of this harmonic wave or the moment that approaches the lowest point export a pulse signal;
Power switch is opened trigger signal generator according to the output of the lowest point detector and the output of bidirectional counter frequently of soft pincers, when in the soft pincers bidirectional counter output valve corresponding the lowest point moment frequently, exports a triggering number, opens in order to trigger power switch.
In sum, the frequency soft clamping system and method for Quasi-resonant switching power supply that the present invention proposes, can effectively avoid power switch in turn in two adjacent the lowest point conductings, within the scope of certain hour, be locked in certain the lowest point conducting, thereby effectively avoided audio-frequency noise, and switching frequency is limited to certain scope.
Here description of the invention and application is illustrative, not wants scope of the present invention to limit in the above-described embodiments.Here the distortion of disclosed embodiment and change is possible, and for those those of ordinary skill in the art, the various parts of the replacement of embodiment and equivalence are known.Those skilled in the art are noted that in the situation that not departing from spirit of the present invention or substantive characteristics, and the present invention can be with other form, structure, layout, ratio, and realize with other assembly, material and parts.In the situation that not departing from the scope of the invention and spirit, can carry out other distortion and change to disclosed embodiment here.
Claims (9)
1. the frequency soft clamping system for Quasi-resonant switching power supply, it is characterized in that, described system is by detecting the switching frequency within the scope of setting-up time, select follow-up setting-up time scope internal power switch lock and fix on certain the lowest point conducting, be limited to certain scope and in setting-up time, be locked in certain the lowest point conducting to reach switching frequency;
Described frequency soft clamping system comprises:
The lowest point detector, in order to detect the lowest point of the free LC harmonic wave of the parasitic capacitance of main inductance and power switch after transformer demagnetization, the lowest point detector is in the lowest point of this harmonic wave or approach the pulse signal of moment output of the lowest point;
Controller is selected in the lowest point, in order to by detecting the switching frequency within the scope of setting-up time, characterizes and need open trigger signal generator to a power switch in the control signal of which the lowest point conducting in follow-up setting-up time scope output;
Power switch is opened trigger signal generator, in order to according to the output of the selected controller of the output of described the lowest point detector and the lowest point, selectes the selected the lowest point output triggering signal of controller in the lowest point, opens in order to trigger power switch.
2. the frequency soft clamping system for Quasi-resonant switching power supply according to claim 1, is characterized in that:
Described frequency soft clamping system comprises:
Oscillator, with thinking that bidirectional counter provides clock signal;
First frequency comparator, whether the frequency that is used for adjudicating Gate port is lower than first frequency signal f_ref_L; Gate port, for driving signal output port, is used for driving power switch, the conducting of power ratio control switch and closing;
Second frequency comparator, in order to the frequency of adjudicating Gate port whether higher than second frequency signal f_ref_H;
Soft pincers are bidirectional counter frequently, in order to according to second frequency comparator and the output of first frequency comparator, starts its output carry out or add one or subtract an operation in each clock cycle; If all receive the sign frequency that is second frequency comparator higher than the signal of second frequency signal f_ref_H within the whole clock cycle, start the output of bidirectional counter frequently of soft pincers in the next cycle so and add an operation; If the sign frequency that at least receives a first frequency comparator within the whole clock cycle is less than the signal of first frequency signal f_ref_L, starts the output of bidirectional counter frequently of soft pincers in the next cycle so and subtract an operation;
The lowest point detector, in order to detect the lowest point of the free LC harmonic wave of the parasitic capacitance of main inductance and power switch after transformer demagnetization, the lowest point detector is in the lowest point of this harmonic wave or approach the pulse signal of moment output of the lowest point;
Power switch is opened trigger signal generator, in order to according to the output of the lowest point detector and the output of bidirectional counter frequently of soft pincers, when in the soft pincers bidirectional counter output valve corresponding the lowest point moment frequently, exports a triggering number, opens in order to trigger power switch.
3. the frequency soft clamping system for Quasi-resonant switching power supply according to claim 1, is characterized in that:
Described frequency soft clamping system comprises:
N frequency divider, in order to the input signal of Gate port is carried out to frequency division N time, frequency division output signal provides clock signal as bidirectional counter; Gate port, for driving signal output port, is used for driving power switch, the conducting of power ratio control switch and closing;
First frequency comparator, in order to the frequency of adjudicating Gate port whether lower than first frequency signal f_ref_L;
Second frequency comparator, in order to the frequency of adjudicating Gate port whether higher than second frequency signal f_ref_H;
Soft pincers frequently bidirectional counter, according to second frequency comparator and the output of first frequency comparator, start its output in each clock cycle and carry out or add one or subtract an operation; If all receive the sign frequency that is second frequency comparator higher than the signal of second frequency signal f_ref_H within the whole clock cycle, start the output of bidirectional counter frequently of soft pincers in the next cycle so and add an operation; If the sign frequency that at least receives a first frequency comparator within the whole clock cycle is less than the signal of first frequency signal f_ref_L, starts the output of bidirectional counter frequently of soft pincers in the next cycle so and subtract an operation;
The lowest point detector is used for detecting the lowest point of the free LC harmonic wave of the parasitic capacitance of main inductance and power switch after transformer demagnetization, and the lowest point detector is in the lowest point of this harmonic wave or approach the pulse signal of moment output of the lowest point;
Power switch is opened trigger signal generator according to the output of the lowest point detector and the output of bidirectional counter frequently of soft pincers, when in the soft pincers bidirectional counter output valve corresponding the lowest point moment frequently, exports a triggering number, opens in order to trigger power switch.
4. the frequency soft clamping system for Quasi-resonant switching power supply according to claim 1, is characterized in that:
Described frequency soft clamping system comprises:
Reference frequency generator, in order to according to the input signal of FB port, for first frequency comparator and second frequency comparator provide reference signal first frequency signal f_ref_L, second frequency signal f_ref_H, reference signal first frequency signal f_ref_L, second frequency signal f_ref_H are subject to FB port controlling; FB port is feedback port, in order to receiving feedback signals;
N frequency divider, in order to the input signal of Gate port is carried out to frequency division N time, frequency division output signal provides clock signal as bidirectional counter;
First frequency comparator, in order to the frequency of adjudicating Gate port whether lower than first frequency signal f_ref_L; Gate port, for driving signal output port, is used for driving power switch, the conducting of power ratio control switch and closing;
Second frequency comparator, in order to the frequency of adjudicating Gate port whether higher than second frequency signal f_ref_H;
Soft pincers are bidirectional counter frequently, in order to according to second frequency comparator and the output of first frequency comparator, starts its output carry out or add one or subtract an operation in each clock cycle; If all receive the sign frequency that is second frequency comparator higher than the signal of second frequency signal f_ref_H within the whole clock cycle, start the output of bidirectional counter frequently of soft pincers in the next cycle so and add an operation; If the sign frequency that at least receives a first frequency comparator within the whole clock cycle is less than the signal of first frequency signal f_ref_L, starts the output of bidirectional counter frequently of soft pincers in the next cycle so and subtract an operation;
The lowest point detector, in order to detect the lowest point of the free LC harmonic wave of the parasitic capacitance of main inductance and power switch after transformer demagnetization, the lowest point detector is in the lowest point of this harmonic wave or approach the pulse signal of moment output of the lowest point;
Power switch is opened trigger signal generator, in order to according to the output of the lowest point detector and the output of bidirectional counter frequently of soft pincers, when in the soft pincers bidirectional counter output valve corresponding the lowest point moment frequently, exports a triggering number, opens in order to trigger power switch.
5. the frequency soft clamping system for Quasi-resonant switching power supply according to claim 1, is characterized in that:
Described frequency soft clamping system comprises: PWM comparator, lead-edge-blanking, rest-set flip-flop, overcurrent protector, soft start, driving stage, reference frequency generator, N frequency divider, first frequency comparator, second frequency comparator, bidirectional counter, the lowest point detector, power switch is opened trigger signal generator;
Reference frequency generator is according to the input signal of FB port, for first frequency comparator and second frequency comparator provide reference signal first frequency signal f_ref_L, second frequency signal f_ref_H, reference signal first frequency signal f_ref_L, second frequency signal f_ref_H are subject to FB port controlling; FB port is feedback port, in order to receiving feedback signals;
N time frequency divider carries out frequency division N time to the input signal of Gate port, and frequency division output signal provides clock signal as bidirectional counter;
Whether the frequency that first frequency comparator is used for adjudicating Gate is lower than first frequency signal f_ref_L;
Whether the frequency that second frequency comparator is used for adjudicating Gate is higher than second frequency signal f_ref_H;
Soft pincers frequently bidirectional counter, according to second frequency comparator and the output of first frequency comparator, start its output in each clock cycle and carry out or add one or subtract an operation; If all receive the sign frequency that is second frequency comparator higher than the signal of second frequency signal f_ref_H within the whole clock cycle, start the output of bidirectional counter frequently of soft pincers in the next cycle and add an operation; If the sign frequency that at least receives a first frequency comparator within the whole clock cycle is less than the signal of first frequency signal f_ref_L, starts the output of bidirectional counter frequently of soft pincers in the next cycle and subtract an operation;
The lowest point detector is used for detecting the lowest point of the free LC harmonic wave of the parasitic capacitance of main inductance and power switch after transformer demagnetization, and the lowest point detector is in the lowest point of this harmonic wave or approach the pulse signal of moment output of the lowest point;
Power switch is opened trigger signal generator according to the output of the lowest point detector and the output of bidirectional counter frequently of soft pincers, when in the soft pincers bidirectional counter output valve corresponding the lowest point moment frequently, exports a triggering number, opens in order to trigger power switch.
6. the frequency soft clamping method for Quasi-resonant switching power supply, it is characterized in that, described method is by detecting the switching frequency within the scope of setting-up time, select follow-up setting-up time scope internal power switch lock and fix on certain the lowest point conducting, be limited to certain scope and in setting-up time, be locked in certain the lowest point conducting to reach switching frequency;
Described frequency soft clamping method comprises the steps:
The lowest point detector detects the lowest point of main inductance and the free LC harmonic wave of the parasitic capacitance of power switch after transformer demagnetization, the lowest point detector in the lowest point of this harmonic wave or the moment that approaches the lowest point export a pulse signal;
The selected controller in the lowest point, by detecting the switching frequency within the scope of setting-up time, characterizes and need open trigger signal generator to a power switch in the control signal of which the lowest point conducting in follow-up setting-up time scope output;
Power switch is opened trigger signal generator according to the output of the selected controller of the output of described the lowest point detector and the lowest point, and in the lowest point, the selected the lowest point output triggering signal of selected controller, opens in order to trigger power switch.
7. the frequency soft clamping method for Quasi-resonant switching power supply according to claim 6, is characterized in that:
Described frequency soft clamping method comprises the steps:
Oscillator provides clock signal for bidirectional counter;
Whether the frequency of first frequency comparator decision Gate port is lower than first frequency signal f_ref_L; Gate port, for driving signal output port, is used for driving power switch, the conducting of power ratio control switch and closing;
Whether the frequency of second frequency comparator decision Gate port is higher than second frequency signal f_ref_H;
Soft pincers frequently bidirectional counter, according to second frequency comparator and the output of first frequency comparator, start its output in each clock cycle and carry out or add one or subtract an operation; If all receive the sign frequency that is second frequency comparator higher than the signal of second frequency signal f_ref_H within the whole clock cycle, start the output of bidirectional counter frequently of soft pincers in the next cycle so and add an operation; If the sign frequency that at least receives a first frequency comparator within the whole clock cycle is less than the signal of first frequency signal f_ref_L, starts the output of bidirectional counter frequently of soft pincers in the next cycle so and subtract an operation;
The lowest point detector detects the lowest point of main inductance and the free LC harmonic wave of the parasitic capacitance of power switch after transformer demagnetization, the lowest point detector in the lowest point of this harmonic wave or the moment that approaches the lowest point export a pulse signal;
Power switch is opened trigger signal generator according to the output of the lowest point detector and the output of bidirectional counter frequently of soft pincers, when in the soft pincers bidirectional counter output valve corresponding the lowest point moment frequently, exports a triggering number, opens in order to trigger power switch.
8. the frequency soft clamping method for Quasi-resonant switching power supply according to claim 6, is characterized in that:
Described frequency soft clamping method comprises the steps:
N time frequency divider carries out frequency division N time to the input signal of Gate port, and frequency division output signal provides clock signal as bidirectional counter; Gate port, for driving signal output port, is used for driving power switch, the conducting of power ratio control switch and closing;
Whether the frequency of first frequency comparator decision Gate port is lower than first frequency signal f_ref_L;
Whether the frequency of second frequency comparator decision Gate port is higher than second frequency signal f_ref_H;
Soft pincers frequently bidirectional counter, according to second frequency comparator and the output of first frequency comparator, start its output in each clock cycle and carry out or add one or subtract an operation; If all receive the sign frequency that is second frequency comparator higher than the signal of second frequency signal f_ref_H within the whole clock cycle, start the output of bidirectional counter frequently of soft pincers in the next cycle so and add an operation; If the sign frequency that at least receives a first frequency comparator within the whole clock cycle is less than the signal of first frequency signal f_ref_L, starts the output of bidirectional counter frequently of soft pincers in the next cycle so and subtract an operation;
The lowest point detector is used for detecting the lowest point of the free LC harmonic wave of the parasitic capacitance of main inductance and power switch after transformer demagnetization, and the lowest point detector is in the lowest point of this harmonic wave or approach the pulse signal of moment output of the lowest point;
Power switch is opened trigger signal generator according to the output of the lowest point detector and the output of bidirectional counter frequently of soft pincers, when in the soft pincers bidirectional counter output valve corresponding the lowest point moment frequently, exports a triggering number, opens in order to trigger power switch.
9. the frequency soft clamping method for Quasi-resonant switching power supply according to claim 6, is characterized in that:
Described frequency soft clamping method comprises the steps:
Reference frequency generator is according to the input signal of FB port, for first frequency comparator and second frequency comparator provide reference signal first frequency signal f_ref_L, second frequency signal f_ref_H, reference signal first frequency signal f_ref_L, second frequency signal f_ref_H are subject to FB port controlling; FB port is feedback port, in order to receiving feedback signals;
N time frequency divider carries out frequency division N time to the input signal of Gate port, and frequency division output signal provides clock signal as bidirectional counter; Gate port, for driving signal output port, is used for driving power switch, the conducting of power ratio control switch and closing;
Whether the frequency of first frequency comparator decision Gate port is lower than first frequency signal f_ref_L;
Whether the frequency of second frequency comparator decision Gate port is higher than second frequency signal f_ref_H;
Soft pincers frequently bidirectional counter, according to second frequency comparator and the output of first frequency comparator, start its output in each clock cycle and carry out or add one or subtract an operation; If all receive the sign frequency that is second frequency comparator higher than the signal of second frequency signal f_ref_H within the whole clock cycle, start the output of bidirectional counter frequently of soft pincers in the next cycle so and add an operation; If the sign frequency that at least receives a first frequency comparator within the whole clock cycle is less than the signal of first frequency signal f_ref_L, starts the output of bidirectional counter frequently of soft pincers in the next cycle so and subtract an operation;
The lowest point detector detects the lowest point of main inductance and the free LC harmonic wave of the parasitic capacitance of power switch after transformer demagnetization, the lowest point detector in the lowest point of this harmonic wave or the moment that approaches the lowest point export a pulse signal;
Power switch is opened trigger signal generator according to the output of the lowest point detector and the output of bidirectional counter frequently of soft pincers, when in the soft pincers bidirectional counter output valve corresponding the lowest point moment frequently, exports a triggering number, opens in order to trigger power switch.
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| CN103391010B (en) * | 2013-07-25 | 2015-10-21 | 深圳市明微电子股份有限公司 | A kind of Switching Power Supply driving chip and switch power source driving circuit |
| CN103701316B (en) * | 2013-12-30 | 2017-03-15 | 杭州士兰微电子股份有限公司 | A kind of quasi-resonance inverse excitation type converter and its controller and control method |
| TWI555314B (en) * | 2015-01-22 | 2016-10-21 | 通嘉科技股份有限公司 | Frequency controller of a power converter and related frequency control method |
| CN105071662B (en) * | 2015-08-26 | 2018-01-05 | 矽力杰半导体技术(杭州)有限公司 | The switching power source control circuit and control method of a kind of quasi-resonant mode |
| WO2017074305A1 (en) * | 2015-10-26 | 2017-05-04 | Dialog Semiconductor Inc. | Adaptive valley mode switching |
| US10069426B2 (en) * | 2016-03-12 | 2018-09-04 | Semiconductor Components Industries, Llc | Active clamp flyback converter |
| JP6853745B2 (en) * | 2017-07-21 | 2021-03-31 | 新日本無線株式会社 | Switching power supply |
| CN107742984B (en) * | 2017-09-28 | 2020-01-21 | 广州金升阳科技有限公司 | Wave trough control circuit and wave trough control method |
| CN109067213B (en) * | 2018-08-08 | 2019-12-20 | 苏州博创集成电路设计有限公司 | Switching power supply controller in quasi-resonance mode and control method |
| CN110677018B (en) * | 2019-10-31 | 2021-01-05 | 矽力杰半导体技术(杭州)有限公司 | Control circuit, control method and switching converter |
| CN111130352A (en) * | 2019-12-24 | 2020-05-08 | 安克创新科技股份有限公司 | Control method of flyback switching power supply |
| 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 |
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Denomination of invention: Frequency soft clamping system and method for quasi resonant switching power supply Effective date of registration: 20230317 Granted publication date: 20140716 Pledgee: Bank of China Limited by Share Ltd. Foshan branch Pledgor: FOSHAN SIFIRST TECHNOLOGIES Ltd. Registration number: Y2023980035214 |