CN116404868A - Quasi-resonant switching power supply and jitter frequency control circuit thereof - Google Patents

Abstract

A quasi-resonant switching power supply and a jitter frequency control circuit thereof are provided. The dither control circuitry is configured to: generating a quasi-resonant valley detection signal based on a resonance voltage characterization signal characterizing a resonance voltage on an auxiliary winding of a transformer in the quasi-resonant switching power supply; generating an upper clamp frequency control signal for controlling a maximum operating frequency of the quasi-resonant switching power supply based on an output feedback control signal related to an output voltage of the quasi-resonant switching power supply; generating a valley-inserted bottom enabling signal based on a pulse width modulation signal for controlling on and off of a switching tube in a quasi-resonant switching power supply; based on the quasi-resonant valley bottom detection signal, the upper clamp frequency control signal, and the valley bottom enable signal, a conduction control signal for controlling a switching tube in the quasi-resonant switching power supply to change from an off state to an on state is generated. The switching tube in the quasi-resonant switching power supply is different in the moment of changing from the off state to the on state in different switching periods when the valley floor enable signal is in the active state and the inactive state.

Description

Quasi-resonant switching power supply and jitter frequency control circuit thereof

Technical Field

The invention relates to the field of circuits, in particular to a quasi-resonant switching power supply and a jitter frequency control circuit thereof.

Background

The switching power supply works in the quasi-resonance mode, so that the drain voltage of the switching tube can be reduced when the switching tube is changed from an off state to an on state, the conduction loss of the switching tube is reduced, and the stress of the switching tube is reduced, thereby improving the system efficiency. However, in practical applications of the switching power supply, it is possible to control the switching tube from an off-state to an on-state when a different number of resonant dips of the resonant voltage on the auxiliary winding of the transformer is detected in successive switching cycles under some loads (the operating mode of the switching power supply in this case is referred to as quasi-resonant dither dip conduction mode), but to control the switching tube from an off-state to an on-state when a fixed number of resonant dips of the resonant voltage is detected in successive switching cycles under other loads (the operating mode of the switching power supply in this case is referred to as quasi-resonant single dip conduction mode). When the switching power supply works in a quasi-resonance single valley conduction mode, the system working frequency is fixed, so that the distribution of single-frequency working energy of the switching power supply is too concentrated, the generated higher harmonic energy is larger, a large amount of electromagnetic radiation can be concentrated through a printed circuit board or a lead, and certain electromagnetic radiation damage is caused to a human body and serious electromagnetic interference is caused to other electronic equipment.

Disclosure of Invention

According to an embodiment of the invention, a jitter control circuit for a quasi-resonant switching power supply is configured to: generating a quasi-resonant valley detection signal based on a resonance voltage characterization signal characterizing a resonance voltage on an auxiliary winding of a transformer in the quasi-resonant switching power supply; generating an upper clamp frequency control signal for controlling a maximum operating frequency of the quasi-resonant switching power supply based on an output feedback control signal related to an output voltage of the quasi-resonant switching power supply; generating a valley-inserted bottom enabling signal based on a pulse width modulation signal for controlling on and off of a switching tube in a quasi-resonant switching power supply; and generating a turn-on control signal for controlling a switching transistor in the quasi-resonant switching power supply to change from an off state to an on state based on the quasi-resonant valley bottom detection signal, the upper clamp frequency control signal, and the valley bottom enable signal, wherein a time at which the switching transistor in the quasi-resonant switching power supply changes from the off state to the on state in a switching period in which the valley bottom enable signal is in an active state is different from a time at which the switching transistor changes from the off state to the on state in a switching period in which the valley bottom enable signal is in an inactive state.

According to an embodiment of the invention, a jitter control circuit for a quasi-resonant switching power supply is configured to: generating a quasi-resonant valley detection signal based on a resonance voltage characterization signal characterizing a resonance voltage on an auxiliary winding of a transformer in the quasi-resonant switching power supply; generating an upper clamp frequency control signal for controlling a maximum operating frequency of the quasi-resonant switching power supply based on an output feedback control signal related to an output voltage of the quasi-resonant switching power supply; generating a valley-inserting bottom enabling signal based on the quasi-resonant valley-bottom detection signal; and generating a turn-on control signal for controlling a switching transistor in the quasi-resonant switching power supply to change from an off state to an on state based on the quasi-resonant valley bottom detection signal, the upper clamp frequency control signal, and the valley bottom enable signal, wherein a time at which the switching transistor in the quasi-resonant switching power supply changes from the off state to the on state in a switching period in which the valley bottom enable signal is in an active state is different from a time at which the switching transistor changes from the off state to the on state in a switching period in which the valley bottom enable signal is in an inactive state.

Drawings

The invention will be better understood from the following description of specific embodiments thereof, taken in conjunction with the accompanying drawings, in which:

fig. 1 shows a schematic circuit diagram of a conventional quasi-resonant switching power supply.

Fig. 2 shows waveforms of the operation of the quasi-resonant switching power supply of fig. 1 in a quasi-resonant single valley conduction mode.

Fig. 3 shows a spectral energy distribution diagram of the quasi-resonant switching power supply of fig. 1 operating in a quasi-resonant single valley conduction mode.

Fig. 4 shows a circuit schematic of a dither control circuit for a quasi-resonant switching power supply, according to an embodiment of the invention.

Fig. 5 shows an exemplary waveform diagram of a plurality of signals when the jitter control circuit shown in fig. 4 implements a frequency-interleaved-floor jitter control scheme using a fixed multi-cycle counting scheme.

Fig. 6 shows an exemplary waveform diagram of a plurality of signals when the jitter control circuit shown in fig. 4 implements a frequency-interleaved-floor jitter control scheme using a pseudo-random multi-cycle counting scheme.

Fig. 7 shows a circuit schematic of a dither control circuit for a quasi-resonant switching power supply, according to another embodiment of the invention.

Fig. 8 is a waveform diagram illustrating an example of signals when the jitter control circuit shown in fig. 7 implements a stuck-at-bottom jitter control scheme using an adjacent fixed multi-cycle count-valley-bottom comparison.

Fig. 9 shows an exemplary waveform diagram of a plurality of signals when the jitter control circuit shown in fig. 7 implements a stuck-at-bottom jitter control scheme using an adjacent pseudo-random multi-cycle count-valley-count comparison scheme.

Fig. 10 shows a spectrum distribution diagram when the frequency-shaking scheme of the bottom of the inserted valley is implemented by adopting a fixed multi-period counting mode or an adjacent fixed multi-period counting valley bottom comparison mode.

Fig. 11 shows a spectrum distribution diagram when the frequency-shaking scheme of the inserted valley bottom is implemented by adopting a pseudo-random multi-period counting mode or an adjacent pseudo-random multi-period counting valley bottom comparison mode.

Detailed Description

Features and exemplary embodiments of various aspects of the invention are described in detail below. In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the invention. It will be apparent, however, to one skilled in the art that the present invention may be practiced without some of these specific details. The following description of the embodiments is merely intended to provide a better understanding of the invention by showing examples of the invention. The present invention is in no way limited to any particular configuration and algorithm set forth below, but rather covers any modification, substitution, and improvement of elements, components, and algorithms without departing from the spirit of the invention. In the drawings and the following description, well-known structures and techniques have not been shown in order to avoid unnecessarily obscuring the present invention.

Fig. 1 shows a schematic circuit diagram of a conventional quasi-resonant switching power supply. In the quasi-resonant switching power supply 100 shown in fig. 1, when the switching tube Q1 is in the on state, the input voltage Vin charges the primary winding of the transformer T1, and the primary winding of the transformer T1 stores energy; when the switching tube Q1 is in the off state, the energy stored in the primary winding of the transformer T1 is transferred to the load through the secondary winding of the transformer T1. In addition, when the switching tube Q1 is in an off state, an auxiliary winding voltage Vaux on an auxiliary winding of the transformer T1 may represent a resonance voltage on a primary winding of the transformer T1, and the auxiliary winding voltage Vaux may generate a resonance voltage representation voltage Vaux by dividing voltages of an upper bias resistor Rup and a lower bias resistor Rdw; the quasi-resonance valley detection signal qr_on can be obtained by comparing the resonance voltage characterization voltage Vaux' with the threshold voltage Vref; the upper clamp frequency control signal qr_max for controlling the maximum operating frequency of the quasi-resonant switching power supply 100 may be generated based on the output feedback control signal fb_d related to the output voltage Vout of the quasi-resonant switching power supply 100; on the basis of the upper clamp control signal qr_max and the quasi-resonant valley detection signal qr_on, a turn-on control signal tri_on for controlling the switching transistor Q1 to be turned from the off state to the on state may be generated; a Pulse Width Modulation (PWM) signal for controlling the on and off of the switching tube Q1 may be generated based on the on control signal tri_on, to implement quasi-resonant valley on control of the switching tube Q1.

Fig. 2 shows waveforms of operation of the signals of the quasi-resonant switching power supply of fig. 1 when operated in the quasi-resonant single valley conduction mode, where n1=n2=n3=n4, in which case the system operating frequency is fixed at f1. Fig. 3 shows a spectral energy distribution diagram of the quasi-resonant switching power supply of fig. 1 operating in a quasi-resonant single valley conduction mode. It can be seen that since the system operating frequency of the quasi-resonant switching power supply 100 shown in fig. 1 remains constant, the peak energy of the single switching frequency and its higher harmonics is high, and the system is now high in energy of electromagnetic radiation to the outside.

In view of the above, the quasi-resonant switching power supply and the jitter frequency control circuit thereof according to the embodiments of the present invention can solve the problem that the quasi-resonant switching power supply works in a quasi-resonant single-valley conduction mode, the system working frequency is fixed, and the electromagnetic radiation to the outside is too large to meet the current electromagnetic compatibility standard of the switching power supply.

Fig. 4 shows a circuit schematic of a dither control circuit for a quasi-resonant switching power supply, according to an embodiment of the invention. The dither control circuitry 400 for a quasi-resonant switching power supply shown in fig. 4 is configured to: generating a quasi-resonant valley detection signal qr_on based on a resonant voltage characterization signal Vaux' that characterizes a resonant voltage on an auxiliary winding of a transformer in the quasi-resonant switching power supply; generating an upper clamp frequency control signal qr_max for controlling a maximum operating frequency of the quasi-resonant switching power supply based on an output feedback control signal fb_d related to an output voltage of the quasi-resonant switching power supply; generating a Valley bottom enable signal valley_insert_ena based on a PWM signal for controlling on and off of a switching transistor in a quasi-resonant switching power supply; and generating an on control signal tri_on for controlling a switching tube in the quasi-resonant switching power supply to be changed from an off state to an on state based on the quasi-resonant Valley detection signal qr_on, the upper clamp frequency control signal qr_max, and the Valley insertion enabling signal valley_insert_ena. Here, the switching transistor in the quasi-resonant switching power supply changes from the off state to the on state in the switching period in which the Valley bottom enable signal valley_insert_ena is in an active state, differently from the off state to the on state in the switching period in which the Valley bottom enable signal valley_insert_ena is in an inactive state.

In some embodiments, in a switching period in which the Valley bottom enable signal valley_insert_ena is in an inactive state, when the upper clamp control signal qr_max is in an active state and the quasi-resonant Valley bottom detection signal qr_on indicates that the resonant voltage on the auxiliary winding of the transformer in the quasi-resonant switching power supply reaches the mth resonant Valley bottom, the on control signal tri_on controls the switching transistor in the quasi-resonant switching power supply to change from an off state to an on state. In a switching period in which the Valley bottom enable signal valley_insert_ena is in an active state, when the upper clamp frequency control signal qr_max is in an active state and the quasi-resonant Valley bottom detection signal qr_on indicates that the resonant voltage on the auxiliary winding of the transformer in the quasi-resonant switching power supply reaches the m+n-th resonant Valley bottom, the on control signal tri_on controls the switching tube in the quasi-resonant switching power supply to change from an off state to an on state, and m and n are integers greater than or equal to 1.

In some embodiments, as shown in fig. 4, the resonance voltage characterization signal Vaux is a resonance voltage characterization voltage generated by dividing an auxiliary winding voltage Vaux on an auxiliary winding of a transformer in the quasi-resonant switching power supply by an upper bias resistor Rup and a lower bias resistor Rdw, and the dither control circuit 400 for the quasi-resonant switching power supply is further configured to generate the quasi-resonant valley detection signal qr_on by comparing the resonance voltage characterization voltage Vaux with a threshold voltage Vref.

In some embodiments, as shown in fig. 4, the dither control circuitry 400 for a quasi-resonant switching power supply is further configured to generate the Valley-enable signal Valley-insert-ENA by counting the switching cycles of the PWM signal.

In some embodiments, as shown in fig. 4, the dither control circuitry 400 for a quasi-resonant switching power supply is further configured to: generating a quasi-resonant Valley conduction signal qr_on' based on the quasi-resonant Valley detection signal qr_on, the upper clamp control signal qr_max, and the Valley insertion enabling signal valley_insert_ena; and generating a conduction control signal tri_on based on the quasi-resonant valley conduction signal qr_on, wherein the conduction control signal tri_on is used to control a switching tube in the quasi-resonant switching power supply to change from an off state to an on state when a resonant voltage on an auxiliary winding of a transformer in the quasi-resonant switching power supply reaches a predetermined number of resonant valleys in a current switching period.

Fig. 5 shows an exemplary waveform diagram of a plurality of signals when the jitter control circuit shown in fig. 4 implements a frequency-interleaved-floor jitter control scheme using a fixed multi-cycle counting scheme. As shown in fig. 4 and 5, in some embodiments, the Valley bottom enable signal valley_insert_ena is active in the n+1th switching cycle of the PWM signal whenever the count of switching cycles of the PWM signal reaches N, where N is a fixed integer greater than or equal to 1. In each switching cycle in which the Valley bottom enable signal valley_insert_ena is in an inactive state, when the upper clamp frequency control signal qr_max is in an active state and the quasi-resonant Valley bottom detection signal qr_on indicates that the resonant voltage on the auxiliary winding of the transformer in the quasi-resonant switching power supply reaches the mth resonant Valley bottom, the PWM signal changes from a low level to a high level, so that the switching tube in the quasi-resonant switching power supply changes from an off state to an on state, and m is an integer greater than or equal to 1. In a switching period in which the Valley bottom enable signal valley_insert_ena is in an active state, when the upper clamp frequency control signal qr_max is in an active state and the quasi-resonant Valley bottom detection signal qr_on indicates that the resonant voltage on the auxiliary winding of the transformer in the quasi-resonant switching power supply reaches the (m+1) -th resonant Valley bottom, the PWM signal changes from a low level to a high level, so that the switching tube in the quasi-resonant switching power supply changes from an off state to an on state. By adopting the fixed multicycle counting frequency-jittering control scheme, the system working frequency of the quasi-resonant switching power supply is periodically changed according to the mode of f1- > f2- > f1- > f 2.

Fig. 6 shows an exemplary waveform diagram of a plurality of signals when the jitter control circuit shown in fig. 4 implements a frequency-interleaved-floor jitter control scheme using a pseudo-random multi-cycle counting scheme. As shown in fig. 4 and 6, in some embodiments, when the count of switching cycles of the PWM signal reaches N1, the Valley bottom enable signal valley_insert_ena is in an active state in the nth 1+1 switching cycle of the PWM signal, and after the nth 1+1 switching cycle of the PWM signal ends, when the recounting of switching cycles of the PWM signal reaches N2, the Valley bottom enable signal valley_insert_ena is in an active state in the nth 2+1 switching cycle of the PWM signal, both N1 and N2 being integers greater than or equal to 1 and n1+.n2. Here, N1 and N2 may be random numbers generated by a pseudo random timing generator within the multi-cycle count-up-and-down-enable control unit. In each switching cycle in which the Valley bottom enable signal valley_insert_ena is in an inactive state, when the upper clamp frequency control signal qr_max is in an active state and the quasi-resonant Valley bottom detection signal qr_on indicates that the resonant voltage on the auxiliary winding of the transformer in the quasi-resonant switching power supply reaches the mth resonant Valley bottom, the PWM signal changes from a low level to a high level, so that the switching tube in the quasi-resonant switching power supply changes from an off state to an on state, and m is an integer greater than or equal to 1. In a switching period in which the Valley bottom enable signal valley_insert_ena is in an active state, when the upper clamp frequency control signal qr_max is in an active state and the quasi-resonant Valley bottom detection signal qr_on indicates that the resonant voltage on the auxiliary winding of the transformer in the quasi-resonant switching power supply reaches the (m+1) -th resonant Valley bottom, the PWM signal changes from a low level to a high level, so that the switching tube in the quasi-resonant switching power supply changes from an off state to an on state. By adopting the false random multicycle counting frequency-shaking control scheme, the system working frequency of the quasi-resonant switching power supply has no fixed cycle random change in a mode of f3- > f4- > f3- > f 4.

Fig. 7 shows a circuit schematic of a dither control circuit for a quasi-resonant switching power supply, according to another embodiment of the invention. The dither control circuitry 700 for a quasi-resonant switching power supply shown in fig. 7 is configured to: generating a quasi-resonant valley detection signal qr_on based on a resonant voltage characterization signal Vaux' that characterizes a resonant voltage on an auxiliary winding of a transformer in the quasi-resonant switching power supply; generating an upper clamp frequency control signal qr_max for controlling a maximum operating frequency of the quasi-resonant switching power supply based on an output feedback control signal fb_d related to an output voltage of the quasi-resonant switching power supply; generating a Valley bottom enable signal valley_insert_ena1 based on the quasi-resonant Valley bottom detection signal qr_on; and generating an on control signal tri_on for controlling a switching tube in the quasi-resonant switching power supply to be changed from an off state to an on state based on the quasi-resonant Valley detection signal qr_on, the upper clamp frequency control signal qr_max, and the Valley insertion enabling signal valley_insert_ena1. Here, the switching transistor in the quasi-resonant switching power supply changes from the off-state to the on-state in the switching period in which the Valley-fill enable signal valley_insert_ena1 is in an active state, differently from the off-state to the on-state in the switching period in which the Valley-fill enable signal valley_insert_ena1 is in an inactive state.

In some embodiments, in a switching period in which the Valley bottom enable signal valley_insert_ena1 is in an inactive state, when the upper clamp control signal qr_max is in an active state and the quasi-resonant Valley bottom detection signal qr_on indicates that the resonant voltage on the auxiliary winding of the transformer in the quasi-resonant switching power supply reaches the mth resonant Valley bottom, the on control signal tri_on controls the switching transistor in the quasi-resonant switching power supply to change from an off state to an on state. In a switching period in which the Valley bottom enable signal valley_insert_ena1 is in an active state, when the upper clamp frequency control signal qr_max is in an active state and the quasi-resonant Valley bottom detection signal qr_on indicates that the resonant voltage on the auxiliary winding of the transformer in the quasi-resonant switching power supply reaches the m+nth resonant Valley bottom, the on control signal tri_on controls the switching tube in the quasi-resonant switching power supply to change from an off state to an on state, and m and n are integers greater than or equal to 1.

In some embodiments, as shown in fig. 7, the resonance voltage characterization signal Vaux is a resonance voltage characterization voltage generated by dividing an auxiliary winding voltage Vaux on an auxiliary winding of a transformer in the quasi-resonant switching power supply by an upper bias resistor Rup and a lower bias resistor Rdw, and the dither control circuit 700 for the quasi-resonant switching power supply is further configured to generate the quasi-resonant valley detection signal qr_on by comparing the resonance voltage characterization voltage Vaux with a threshold voltage Vref.

In some embodiments, as shown in fig. 7, the dither control circuitry 700 for a quasi-resonant switching power supply is further configured to: the Valley bottom enable signal valley_insert_ena1 is generated by counting and comparing the number of resonant valleys in each of the adjacent plurality of switching cycles aligned with the resonant voltage on the auxiliary winding of the transformer in the quasi-resonant switching power supply indicated by the resonant Valley bottom detection signal qr_on.

In some embodiments, as shown in fig. 7, the dither control circuitry 700 for a quasi-resonant switching power supply is further configured to: generating a quasi-resonant Valley conduction signal qr_on' based on the quasi-resonant Valley detection signal qr_on, the upper clamp control signal qr_max, and the Valley insertion enabling signal valley_insert_ena1; and generating a conduction control signal tri_on based on the quasi-resonant valley conduction signal qr_on, wherein the conduction control signal tri_on is used for controlling a switching tube in the quasi-resonant switching power supply to change from an off state to an on state when a resonant voltage on an auxiliary winding of a transformer in the quasi-resonant switching power supply reaches a predetermined number of resonant valleys in a current switching period.

Fig. 8 is a waveform diagram illustrating an example of signals when the jitter control circuit shown in fig. 7 implements a stuck-at-bottom jitter control scheme using an adjacent fixed multi-cycle count-valley-bottom comparison. As shown in fig. 7 and 8, in some embodiments, whenever the resonant voltage on the auxiliary winding of the transformer in the quasi-resonant switching power supply, indicated by the quasi-resonant Valley detection signal qr_on, is equal in number to the resonant Valley in each of the adjacent T switching cycles, the Valley-fill enable signal valley_insert_ena1 is in an active state in the next switching cycle immediately following the T switching cycles, T being a fixed integer greater than or equal to 1. That is, the resonant voltage on the auxiliary winding of the transformer in the quasi-resonant switching power supply is counted and compared in the number of resonant dips in each of the adjacent T switching cycles based on the quasi-resonant dip detection signal qr_on, and if the resonant voltage on the auxiliary winding of the transformer in the quasi-resonant switching power supply is equal in the number of resonant dips in each of the adjacent T switching cycles (for example, x1=x2 or x3=x4), the dip enable signal valley_insert_ena1 is in an active state in the next switching cycle immediately after the T switching cycles, otherwise (for example, x1+notex2or x3+notex4) the dip enable signal valley_insert_ena1 is in an inactive state in the next switching cycle immediately after the T switching cycles. In each switching cycle in which the Valley bottom enable signal valley_insert_ena1 is in an inactive state, when the upper clamp frequency control signal qr_max is in an active state and the quasi-resonant Valley bottom detection signal qr_on indicates that the resonant voltage on the auxiliary winding of the transformer in the quasi-resonant switching power supply reaches the mth resonant Valley bottom, the PWM signal changes from a low level to a high level, so that the switching tube in the quasi-resonant switching power supply changes from an off state to an on state, and m is an integer greater than or equal to 1. In a switching period in which the Valley bottom enable signal valley_insert_ena1 is in an active state, when the upper clamp frequency control signal qr_max is in an active state and the quasi-resonant Valley bottom detection signal qr_on indicates that the resonant voltage on the auxiliary winding of the transformer in the quasi-resonant switching power supply reaches the (m+1) -th resonant Valley bottom, the PWM signal changes from a low level to a high level, so that the switching tube in the quasi-resonant switching power supply changes from an off state to an on state. It is noted here that the Valley bottom enable signal valley_insert_ena1 needs to be reset to an inactive state after the end of the current switching period in which the Valley bottom enable signal valley_insert_ena1 is in an active state and before the start of the next switching period. By adopting the frequency-jitter control scheme of the trough bottom of the adjacent fixed multicycle counting trough bottom comparison mode, the system working frequency of the quasi-resonant switching power supply is periodically changed according to the mode of f5- > f6- > f5- > f 6.

Fig. 9 shows an exemplary waveform diagram of a plurality of signals when the jitter control circuit shown in fig. 7 implements a stuck-at-bottom jitter control scheme using an adjacent pseudo-random multi-cycle count-valley-count comparison scheme. As shown in fig. 7 and 9, in some embodiments, when the number of resonant dips on the auxiliary winding of the transformer in the quasi-resonant switching power supply indicated by the quasi-resonant dip detection signal qr_on in each of the adjacent T1 switching cycles is unequal, the dip enable signal valley_insert_ena1 is in an inactive state in the next switching cycle immediately after the T1 switching cycles, and when the number of resonant dips on the auxiliary winding of the transformer in the quasi-resonant switching power supply indicated by the quasi-resonant dip detection signal qr_on in each of the adjacent T2 switching cycles is equal after the end of the next switching cycle immediately after the T1 switching cycles, the dip enable signal valley_ena1 is in an active state in the next switching cycle immediately after the T2 switching cycles, and both T1 and T2 are integers equal to or greater than 1 and T2. Here, T1 and T2 may be random numbers generated by a pseudo random timing generator. That is, the resonant voltages on the auxiliary windings of the transformers in the aligned resonant switching power supply are compared in the numbers Y1 and Y2 of resonant dips in each of the adjacent T1 switching cycles, and if y1=y2, the dip enable signal valley_insert_ena1 is in an active state in the next switching cycle immediately after the T1 switching cycles, otherwise the dip enable signal valley_insert_ena1 is in an inactive state in the next switching cycle immediately after the T1 switching cycles. Next, the number Y3, Y4, and Y5 of resonant floors in each of the adjacent T2 switching cycles is compared aligning the resonant voltage on the auxiliary winding of the transformer in the resonant switching power supply, and if y3=y4=y5, the floor enable signal valley_insert_ena1 is in an active state in the next switching cycle immediately after the T2 switching cycles, otherwise the floor enable signal valley_insert_ena1 is in an inactive state in the next switching cycle immediately after the T1 switching cycles. By adopting the frequency-jitter control scheme of the trough bottom in the adjacent pseudo-random multi-period counting trough bottom comparison mode, the system working frequency of the switching power supply has no fixed period change in the mode of f7- > f8- > f7- > f8 (because T1 and T2 are random numbers).

According to the jitter frequency control circuit for the quasi-resonant switching power supply, the quasi-resonant switching power supply can work in a quasi-resonant jitter valley conduction mode under a certain fixed load, so that the system working frequency of the quasi-resonant switching power supply is changed regularly or randomly in a plurality of continuous switching cycles. By the frequency jitter control scheme of the valley insertion bottom, the energy distribution of the quasi-resonant switching power supply is not concentrated on a single frequency, but the energy of the quasi-resonant switching power supply is scattered and distributed on a plurality of fundamental frequencies.

Fig. 10 shows a spectrum distribution diagram when the frequency-shaking scheme of the bottom of the inserted valley is implemented by adopting a fixed multi-period counting mode or an adjacent fixed multi-period counting valley bottom comparison mode. Fig. 11 shows a spectrum distribution diagram when the frequency-shaking scheme of the inserted valley bottom is implemented by adopting a pseudo-random multi-period counting mode or an adjacent pseudo-random multi-period counting valley bottom comparison mode. According to the frequency jitter control scheme of the inserted valley bottom, the energy of the quasi-resonant switching power supply can be distributed on a plurality of fundamental frequencies and has more high-frequency harmonic components, so that the energy of the quasi-resonant switching power supply to external radiation is greatly reduced, and finally the electromagnetic compatibility requirement of the switching power supply is met.

It should be noted that the jitter control circuit for a quasi-resonant switching power supply according to the embodiment of the present invention may be applied to switching power supplies adopting topologies such as BUCK (BUCK), BOOST (BOOST), BUCK-BOOST (BUCK), flyback (Flyback), forward (Forward), and asymmetric half-bridge.

The present invention may be embodied in other specific forms without departing from its spirit or essential characteristics. For example, the algorithms described in particular embodiments may be modified without departing from the basic spirit of the invention. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

Claims (15)

1. A dither control circuitry for a quasi-resonant switching power supply configured to:

generating a quasi-resonant valley detection signal based on a resonant voltage characterization signal characterizing a resonant voltage on an auxiliary winding of a transformer in the quasi-resonant switching power supply;

generating an upper clamp frequency control signal for controlling a maximum operating frequency of the quasi-resonant switching power supply based on an output feedback control signal related to an output voltage of the quasi-resonant switching power supply;

generating a valley-fill enable signal based on a pulse width modulation signal for controlling on and off of a switching tube in the quasi-resonant switching power supply; and

generating a conduction control signal for controlling the switching tube in the quasi-resonant switching power supply to change from an off state to an on state based on the quasi-resonant valley detection signal, the upper clamp frequency control signal, and the valley inserting bottom enable signal, wherein

The switching tube in the quasi-resonant switching power supply is different from the moment of changing from the off state to the on state in the switching period when the valley bottom enabling signal is in the active state.

2. The dither control circuitry for a quasi-resonant switching power supply of claim 1 further configured to:

and generating the valley-inserting bottom enabling signal by counting the switching period of the pulse width modulation signal.

3. The dither control circuitry for a quasi-resonant switching power supply of claim 2 wherein the valley floor enable signal is in an active state every time a count of switching cycles of the pulse width modulated signal reaches N, N being a fixed integer greater than or equal to 1, in an n+1th switching cycle of the pulse width modulated signal.

4. The dither control circuitry for a quasi-resonant switching power supply of claim 2 wherein the valley bottom enable signal is in an active state in an N1+1 th switching period of the pulse width modulated signal when a count of switching periods of the pulse width modulated signal reaches N1, and

when the recounting of the switching period of the pulse width modulation signal reaches N2 after the N1+1 switching period of the pulse width modulation signal is finished, the valley-inserted bottom enable signal is in an active state in the N2+1 switching period of the pulse width modulation signal, N1 and N2 are integers greater than or equal to 1 and n1+.n2.

5. The dither control circuitry for a quasi-resonant switching power supply of claim 4 wherein N1 and N2 are random numbers generated by a pseudo-random timing generator.

6. The dither control circuitry for a quasi-resonant switching power supply of claim 1 further configured to:

generating a quasi-resonant valley bottom conduction signal based on the quasi-resonant valley bottom detection signal, the upper clamp frequency control signal and the valley inserting bottom enabling signal; and

and generating the conduction control signal based on the quasi-resonant valley conduction signal, wherein the conduction control signal is used for controlling the switching tube in the quasi-resonant switching power supply to change from an off state to an on state when the resonant voltage on the auxiliary winding of the transformer reaches a preset number of resonant valleys in the current switching period.

7. The jitter control circuit for a quasi-resonant switching power supply of claim 1 wherein, in a switching period in which the insertion bottom enable signal is in an inactive state, when the upper clamp control signal is in an active state and the quasi-resonant bottom detection signal indicates that a resonant voltage on an auxiliary winding of the transformer reaches an mth resonant bottom, the turn-on control signal controls the switching tube in the quasi-resonant switching power supply to change from an off state to an on state, and

in the switching period that the insertion valley bottom enabling signal is in an effective state, when the upper clamp frequency control signal is in an effective state and the quasi-resonant valley bottom detection signal indicates that the resonant voltage on the auxiliary winding of the transformer reaches the (m+n) th resonant valley bottom, the switching control signal controls the switching tube in the quasi-resonant switching power supply to be changed from an off state to an on state, and m and n are integers which are larger than or equal to 1.

8. A dither control circuitry for a quasi-resonant switching power supply configured to:

generating a quasi-resonant valley detection signal based on a resonant voltage characterization signal characterizing a resonant voltage on an auxiliary winding of a transformer in the quasi-resonant switching power supply;

generating an upper clamp frequency control signal for controlling a maximum operating frequency of the quasi-resonant switching power supply based on an output feedback control signal related to an output voltage of the quasi-resonant switching power supply;

generating a valley floor enable signal based on the quasi-resonant valley floor detection signal; and

generating a conduction control signal for controlling a switching tube in the quasi-resonant switching power supply to change from an off state to an on state based on the quasi-resonant valley bottom detection signal, the upper clamp frequency control signal, and the valley inserting bottom enable signal, wherein

The switching tube in the quasi-resonant switching power supply is different from the moment of changing from the off state to the on state in the switching period when the valley bottom enabling signal is in the active state.

9. The dither control circuitry for a quasi-resonant switching power supply of claim 8 further configured to:

the valley floor enable signal is generated by counting and comparing the number of resonant valleys in each of a plurality of adjacent switching cycles of a resonant voltage on an auxiliary winding of the transformer indicated by the quasi-resonant valley floor detection signal.

10. The jitter control circuit for a quasi-resonant switching power supply of claim 9 wherein the dip enable signal is in an active state in a next switching period immediately after the T switching periods whenever the number of resonant dips on the auxiliary winding of the transformer indicated by the quasi-resonant dip detect signal is equal in each of the adjacent T switching periods, T being a fixed integer greater than or equal to 1.

11. The jitter control circuit for a quasi-resonant switching power supply of claim 9 wherein, when the number of resonant dips in each of adjacent T1 switching cycles of the resonant voltage on the auxiliary winding of the transformer indicated by the quasi-resonant dip detection signal is equal, the dip enable signal is in an active state in the next switching cycle immediately after the T1 switching cycles, and

when the number of resonance dips in each of the adjacent T2 switching cycles of the resonant voltage on the auxiliary winding of the transformer indicated by the quasi-resonance dip detection signal is equal after the end of the next switching cycle immediately after the T1 switching cycles, the dip enable signal is in an active state in the next switching cycle immediately after the T2 switching cycles, both T1 and T2 are integers greater than or equal to 1 and t1+.t2.

12. The dither control circuitry for a quasi-resonant switching power supply of claim 11 wherein T1 and T2 are random numbers generated by a pseudo-random timing generator.

13. The dither control circuitry for a quasi-resonant switching power supply of claim 8 further configured to:

generating a quasi-resonant valley bottom conduction signal based on the quasi-resonant valley bottom detection signal, the upper clamp frequency control signal and the valley inserting bottom enabling signal; and

and generating the conduction control signal based on the quasi-resonant valley conduction signal, wherein the conduction control signal is used for controlling the switching tube in the quasi-resonant switching power supply to change from an off state to an on state when the resonant voltage on the auxiliary winding of the transformer reaches a preset number of resonant valleys in the current switching period.

14. The jitter control circuit for a quasi-resonant switching power supply of claim 8 wherein, in a switching period in which the insertion bottom enable signal is in an inactive state, when the upper clamp control signal is in an active state and the quasi-resonant bottom detection signal indicates that a resonant voltage on an auxiliary winding of the transformer reaches an mth resonant bottom, the turn-on control signal controls the switching tube in the quasi-resonant switching power supply to change from an off state to an on state, and

in the switching period that the insertion valley bottom enabling signal is in an effective state, when the upper clamp frequency control signal is in an effective state and the quasi-resonant valley bottom detection signal indicates that the resonant voltage on the auxiliary winding of the transformer reaches the (m+n) th resonant valley bottom, the switching control signal controls the switching tube in the quasi-resonant switching power supply to be changed from an off state to an on state, and m and n are integers which are larger than or equal to 1.

15. A quasi-resonant switching power supply comprising the dither control circuitry for a quasi-resonant switching power supply of any one of claims 1 to 14.

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