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 its frequency shaking control circuit

technical field

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

Background technique

Working in quasi-resonant mode of the switching power supply can reduce the drain voltage of the switch tube from the off state to the on state, reduce the conduction loss of the switch tube, reduce the stress of the switch tube, and improve the system efficiency. However, in the actual application of switching power supply, it is possible to control the switching tube from the off state to the on state ( The working mode of the switching power supply in this case is called the quasi-resonant jitter valley conduction mode), but under other loads, when a fixed number of resonance valleys of the resonant voltage are detected in consecutive switching cycles, the switching tube is controlled to turn off from The state changes to the conducting state (the mode of operation of the switching power supply in this case is called quasi-resonant single valley conduction mode). When the switching power supply works in the quasi-resonant single valley conduction mode, the system operating frequency is fixed, which leads to the distribution of the single frequency working energy of the switching power supply is too concentrated, and the high-order harmonic energy generated is relatively large, which will pass through the printed circuit board. Or the wires discharge a large amount of electromagnetic radiation in a concentrated manner, causing certain electromagnetic radiation damage to the human body and causing serious electromagnetic interference to other electronic equipment.

Contents of the invention

The frequency shaking control circuit for a quasi-resonant switching power supply according to an embodiment of the present invention is configured to: generate a quasi-resonant valley detection signal based on a resonance voltage characterization signal representing a resonance voltage on an auxiliary winding of a transformer in a quasi-resonant switching power supply ; Based on the output feedback control signal related to the output voltage of the quasi-resonant switching power supply, generate an upper clamp frequency control signal for controlling the maximum operating frequency of the quasi-resonant switching power supply; based on the guide for controlling the switching tube in the quasi-resonant switching power supply The pulse width modulation signal of on and off is used to generate a valley insertion enable signal; and based on the quasi-resonance valley detection signal, the upper clamp frequency control signal, and the valley insertion enable signal, generate a switching tube for controlling the quasi-resonance switching power supply The conduction control signal that changes from the off state to the on state, wherein, the switching tubes in the quasi-resonant switching power supply have different moments from the off state to the on state in the switching cycle when the valley insertion enable signal is in the active state At the moment when the valley-slip enable signal is in the inactive state from the off state to the on state in the switching cycle.

The frequency shaking control circuit for a quasi-resonant switching power supply according to an embodiment of the present invention is configured to: generate a quasi-resonant valley detection signal based on a resonance voltage characterization signal representing a resonance voltage on an auxiliary winding of a transformer in a quasi-resonant switching power supply ; Based on the output feedback control signal related to the output voltage of the quasi-resonant switching power supply, generate an upper clamp frequency control signal for controlling the maximum operating frequency of the quasi-resonant switching power supply; based on the quasi-resonant valley bottom detection signal, generate a valley insertion enable signal; And based on the quasi-resonant valley bottom detection signal, the clamp frequency control signal, and the valley insertion enable signal, generate a conduction control signal for controlling the switching tube in the quasi-resonant switching power supply from an off state to a conduction state, wherein, The switching tube in the quasi-resonant switching power supply changes from the off state to the on state in the switching cycle when the valley insertion enable signal is in the valid state, which is different from the time when the valley insertion enable signal is in the invalid state from the off state to the switch cycle. The moment when the state changes to the on state.

Description of drawings

The present invention can be better understood from the following description of specific embodiments of the present invention in conjunction with the accompanying drawings, wherein:

Figure 1 shows the circuit schematic diagram of a traditional quasi-resonant switching power supply.

FIG. 2 shows working waveform diagrams of multiple signals when the quasi-resonant switching power supply shown in FIG. 1 works in the quasi-resonant single valley conduction mode.

FIG. 3 shows a spectrum energy distribution diagram of the quasi-resonant switching power supply shown in FIG. 1 operating in the quasi-resonant single valley conduction mode.

FIG. 4 shows a schematic circuit diagram of a frequency shaking control circuit for a quasi-resonant switching power supply according to an embodiment of the present invention.

FIG. 5 shows an example waveform diagram of multiple signals when the frequency shaking control circuit shown in FIG. 4 adopts a fixed multi-period counting method to realize the frequency shaking control scheme of valley bottoming.

FIG. 6 shows an example waveform diagram of multiple signals when the frequency shaking control circuit shown in FIG. 4 adopts a pseudo-random multi-cycle counting method to realize the frequency shaking control scheme of valley bottoming.

FIG. 7 shows a schematic circuit diagram of a frequency shaking control circuit for a quasi-resonant switching power supply according to another embodiment of the present invention.

FIG. 8 shows an example waveform diagram of multiple signals when the frequency shaking control circuit shown in FIG. 7 adopts the method of comparing adjacent fixed multi-period counting valley numbers to realize the valley bottoming frequency shaking control scheme.

FIG. 9 shows an example waveform diagram of multiple signals when the frequency shaking control circuit shown in FIG. 7 adopts the method of comparing adjacent pseudo-random multi-period counting valley numbers to implement the valley insertion frequency shaking control scheme.

FIG. 10 shows a spectrum distribution diagram when a fixed multi-period counting method or an adjacent fixed multi-period counting valley-bottom number comparison method is used to realize the frequency-jittering scheme for bottoming out valleys.

FIG. 11 shows a spectrum distribution diagram when a pseudo-random multi-period counting method or an adjacent pseudo-random multi-period counting valley number comparison method is used to implement the valley-inserting frequency shaking scheme.

Detailed ways

Features and exemplary embodiments of various aspects of the invention will be described in detail below. In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the present 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 only to provide a better understanding of the present invention by showing examples of the present invention. The present invention is by no means limited to any specific configurations and algorithms presented below, but 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.

Figure 1 shows the circuit schematic diagram of a traditional quasi-resonant switching power supply. In the quasi-resonant switching power supply 100 shown in FIG. 1, when the switch 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 switch tube Q1 is in the off state In the off state, the energy stored in the primary winding of the transformer T1 is transmitted to the load through the secondary winding of the transformer T1. In addition, when the switch tube Q1 is in the off state, the auxiliary winding voltage Vaux on the auxiliary winding of the transformer T1 can represent the resonant voltage on the primary winding of the transformer T1, and the auxiliary winding voltage Vaux passes through the upper bias resistor Rup and the lower bias resistor Rdw The voltage division of the resonant voltage can generate the characteristic voltage Vaux‵ of the resonant voltage; by comparing the characteristic voltage Vaux‵ of the resonant voltage with the threshold voltage Vref, the quasi-resonant valley detection signal Qr_on can be obtained; based on the output related to the output voltage Vout of the quasi-resonant switching power supply 100 The feedback control signal FB_d can generate an upper clamping frequency control signal Qr_max for controlling the maximum operating frequency of the quasi-resonant switching power supply 100; based on the upper clamping frequency control signal Qr_max and the quasi-resonant valley detection signal Qr_on, it can be generated for controlling the switching tube Q1 from off to off. The conduction control signal Tri_on from the off state to the on state; based on the conduction control signal Tri_on, a pulse width modulation (PWM) signal for controlling the on and off of the switch tube Q1 can be generated to realize the accurate control of the switch tube Q1. Resonant valley conduction control.

Fig. 2 has shown the operating wave diagram of a plurality of signals when the quasi-resonant switching power supply shown in Fig. 1 works in the quasi-resonant single valley conduction mode, wherein, N1=N2=N3=N4, the system in this case The operating frequency is fixed at f1. FIG. 3 shows a spectrum energy distribution diagram of the quasi-resonant switching power supply shown in FIG. 1 operating in the 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 a single switching frequency and its higher harmonics is very high, and the external electromagnetic radiation energy of the system at this time is very high. .

In view of the above situation, a quasi-resonant switching power supply and its frequency shaking control circuit according to an embodiment of the present invention are proposed, which can solve the problem that the quasi-resonant switching power supply operates in a quasi-resonant single valley conduction mode, the system operating frequency is fixed, and the external electromagnetic radiation Problems that are too large to meet current EMC standards for switching power supplies.

FIG. 4 shows a schematic circuit diagram of a frequency shaking control circuit for a quasi-resonant switching power supply according to an embodiment of the present invention. The frequency shaking control circuit 400 for a quasi-resonant switching power supply shown in FIG. 4 is configured to: generate quasi-resonant valley detection based on the resonant voltage characterization signal Vaux‵ representing the resonance voltage on the auxiliary winding of the transformer in the quasi-resonant switching power supply Signal Qr_on; based on the output feedback control signal FB_d related to the output voltage of the quasi-resonant switching power supply, generate an upper clamp frequency control signal Qr_max for controlling the maximum operating frequency of the quasi-resonant switching power supply; The PWM signal of the on and off of the switch tube generates the valley insertion enable signal Valley_insert_ENA; and based on the quasi-resonance valley detection signal Qr_on, the upper clamp frequency control signal Qr_max, and the valley insertion enable signal Valley_insert_ENA, generate a quasi-resonance control signal A conduction control signal Tri_on for switching the switch tube in the switching power supply from an off state to an on state. Here, the switching tube in the quasi-resonant switching power supply changes from the off state to the on state in the switching period when the valley insertion enable signal Valley_insert_ENA is in the active state, which is different from the switching period when the valley insertion enable signal Valley_insert_ENA is in the inactive state. the moment when it changes from the off state to the on state.

In some embodiments, during the switching period when the valley insertion enable signal Valley_insert_ENA is inactive, when the clamp frequency control signal Qr_max is in the active state and the quasi-resonant valley detection signal Qr_on indicates that the auxiliary winding of the transformer in the quasi-resonant switching power supply is on When the resonant voltage reaches the mth resonance valley, the conduction control signal Tri_on controls the switch tube in the quasi-resonant switching power supply to change from off state to on state. In the switching period when the valley insertion enable signal Valley_insert_ENA is in the active state, when the clamp frequency control signal Qr_max is in the active state and the quasi-resonant valley detection signal Qr_on indicates that the resonance voltage on the auxiliary winding of the transformer in the quasi-resonant switching power supply reaches the mth When there are +n resonance valleys, the conduction 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 both 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 generated by dividing the auxiliary winding voltage Vaux on the auxiliary winding of the transformer in the quasi-resonant switching power supply through the upper bias resistor Rup and the lower bias resistor Rdw. The resonant voltage characterizes the voltage, and the frequency shaking 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 resonant voltage characterizing voltage Vaux‵ with the threshold voltage Vref.

In some embodiments, as shown in FIG. 4 , the frequency shaking control circuit 400 for a quasi-resonant switching power supply is further configured to generate the valley insertion enable signal Valley_insert_ENA by counting the switching cycles of the PWM signal.

In some embodiments, as shown in FIG. 4 , the frequency shaking control circuit 400 for a quasi-resonant switching power supply is further configured to: based on the quasi-resonant valley detection signal Qr_on, the upper clamping control signal Qr_max, and the valley insertion enable signal Valley_insert_ENA generates the quasi-resonant valley conduction signal Qr_on‵; and generates the conduction control signal Tri_on based on the quasi-resonance valley conduction signal Qr_on‵, wherein the conduction control signal Tri_on is used to control the switching tube in the quasi-resonant switching power supply in the current switching cycle When the resonant voltage on the auxiliary winding of the transformer in the quasi-resonant switching power supply reaches a predetermined number of resonance valleys, it changes from the off state to the on state.

FIG. 5 shows an example waveform diagram of multiple signals when the frequency shaking control circuit shown in FIG. 4 adopts a fixed multi-period counting method to realize the frequency shaking control scheme of valley bottoming. As shown in FIG. 4 and FIG. 5 , in some embodiments, whenever the count of the switching period of the PWM signal reaches N, the valley insertion enable signal Valley_insert_ENA is in the active state in the N+1th switching period of the PWM signal, Wherein, N is a fixed integer greater than or equal to 1. In each switching cycle when the valley insertion enable signal Valley_insert_ENA is in an inactive state, when the clamp frequency control signal Qr_max is in an active state and the quasi-resonant valley detection signal Qr_on indicates that the resonance voltage on the auxiliary winding of the transformer in the quasi-resonant switching power supply reaches At the bottom of the mth resonant valley, the PWM signal changes from low level to high level, so that the switching tube in the quasi-resonant switching power supply changes from off state to on state, and m is an integer greater than or equal to 1. In the switching period when the valley insertion enable signal Valley_insert_ENA is in the active state, when the clamp frequency control signal Qr_max is in the active state and the quasi-resonant valley detection signal Qr_on indicates that the resonance voltage on the auxiliary winding of the transformer in the quasi-resonant switching power supply reaches the mth At +1 resonance valley, the PWM signal changes from low level to high level, so that the switching tube in the quasi-resonant switching power supply changes from off state to on state. By adopting a frequency-shaking control scheme with fixed multi-cycle counting, the system operating frequency of the quasi-resonant switching power supply changes periodically in the manner of f1->f2->f1->f2.

FIG. 6 shows an example waveform diagram of multiple signals when the frequency shaking control circuit shown in FIG. 4 adopts a pseudo-random multi-cycle counting method to realize the frequency shaking control scheme of valley bottoming. As shown in FIG. 4 and FIG. 6, in some embodiments, when the count of the switching period of the PWM signal reaches N1, the valley insertion enable signal Valley_insert_ENA is in the active state in the N1+1th switching period of the PWM signal, and After the N1+1th switching period of the PWM signal ends, when the recount of the switching period of the PWM signal reaches N2, the valley insertion enable signal Valley_insert_ENA is in the active state in the N2+1th switching period of the PWM signal, and N1 and N2 are both 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 counting valley enable control unit. In each switching cycle when the valley insertion enable signal Valley_insert_ENA is in an inactive state, when the clamp frequency control signal Qr_max is in an active state and the quasi-resonant valley detection signal Qr_on indicates that the resonance voltage on the auxiliary winding of the transformer in the quasi-resonant switching power supply reaches At the bottom of the mth resonant valley, the PWM signal changes from low level to high level, so that the switching tube in the quasi-resonant switching power supply changes from off state to on state, and m is an integer greater than or equal to 1. In the switching period when the valley insertion enable signal Valley_insert_ENA is in the active state, when the clamp frequency control signal Qr_max is in the active state and the quasi-resonant valley detection signal Qr_on indicates that the resonance voltage on the auxiliary winding of the transformer in the quasi-resonant switching power supply reaches the mth At +1 resonance valley, the PWM signal changes from low level to high level, so that the switching tube in the quasi-resonant switching power supply changes from off state to on state. By adopting the pseudo-random multi-cycle counting frequency shaking control scheme, the system operating frequency of the quasi-resonant switching power supply changes randomly without a fixed period in the manner of f3->f4->f3->f4.

FIG. 7 shows a schematic circuit diagram of a frequency shaking control circuit for a quasi-resonant switching power supply according to another embodiment of the present invention. The frequency shaking control circuit 700 for a quasi-resonant switching power supply shown in FIG. 7 is configured to: generate quasi-resonant valley detection based on the resonance voltage characterization signal Vaux‵ representing the resonance voltage on the auxiliary winding of the transformer in the quasi-resonant switching power supply Signal Qr_on; based on the output feedback control signal FB_d related to the output voltage of the quasi-resonant switching power supply, an upper clamp frequency control signal Qr_max for controlling the maximum operating frequency of the quasi-resonant switching power supply is generated; based on the quasi-resonant valley bottom detection signal Qr_on, an insertion The valley enable signal Valley_insert_ENA1; and based on the quasi-resonant valley detection signal Qr_on, the upper clamp frequency control signal Qr_max, and the valley insertion enable signal Valley_insert_ENA1, are generated to control the switching tube in the quasi-resonant switching power supply from off state to on State conduction control signal Tri_on. Here, the switching tube in the quasi-resonant switching power supply changes from the off state to the on state in the switching cycle when the valley insertion enable signal Valley_insert_ENA1 is in an active state, which is different from the switching cycle when the valley insertion enable signal Valley_insert_ENA1 is in an invalid state. the moment when it changes from the off state to the on state.

In some embodiments, during the switching period when the valley insertion enable signal Valley_insert_ENA1 is inactive, when the clamp frequency control signal Qr_max is in the active state and the quasi-resonant valley detection signal Qr_on indicates that the auxiliary winding of the transformer in the quasi-resonant switching power supply is on When the resonant voltage reaches the mth resonance valley, the conduction control signal Tri_on controls the switch tube in the quasi-resonant switching power supply to change from off state to on state. In the switching period when the valley insertion enable signal Valley_insert_ENA1 is in the active state, when the clamp frequency control signal Qr_max is in the active state and the quasi-resonant valley detection signal Qr_on indicates that the resonance voltage on the auxiliary winding of the transformer in the quasi-resonant switching power supply reaches the mth When there are +n resonance valleys, the conduction 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 both m and n are integers greater than or equal to 1.

In some embodiments, as shown in FIG. 7, the resonant voltage characteristic signal Vaux‵ is generated by dividing the auxiliary winding voltage Vaux on the auxiliary winding of the transformer in the quasi-resonant switching power supply through the upper bias resistor Rup and the lower bias resistor Rdw. The resonant voltage represents a voltage, and the frequency shaking control circuit 700 for a quasi-resonant switching power supply is further configured to generate a quasi-resonant valley detection signal Qr_on by comparing a resonant voltage representative voltage Vaux‵ with a threshold voltage Vref.

In some embodiments, as shown in FIG. 7 , the frequency shaking control circuit 700 for a quasi-resonant switching power supply is further configured as: an auxiliary winding of a transformer in a quasi-resonant switching power supply indicated by aligning the resonance valley detection signal Qr_on Count and compare the number of resonant valleys in each switching period of the resonant voltage on the adjacent switching period to generate the valley insertion enabling signal Valley_insert_ENA1 .

In some embodiments, as shown in FIG. 7 , the frequency shaking control circuit 700 for a quasi-resonant switching power supply is further configured to: based on the quasi-resonant valley detection signal Qr_on, the upper clamping control signal Qr_max, and the valley insertion enable signal Valley_insert_ENA1 generates the quasi-resonant valley conduction signal Qr_on‵; and generates the conduction control signal Tri_on based on the quasi-resonance valley conduction signal Qr_on‵, wherein the conduction control signal Tri_on is used to control the switching tube in the quasi-resonant switching power supply in the current switching cycle When the resonant voltage on the auxiliary winding of the transformer in the quasi-resonant switching power supply reaches a predetermined number of resonance valleys, it changes from the off state to the on state.

FIG. 8 shows an example waveform diagram of multiple signals when the frequency shaking control circuit shown in FIG. 7 adopts the method of comparing adjacent fixed multi-period counting valley numbers to realize the valley bottoming frequency shaking control scheme. As shown in FIGS. 7 and 8 , in some embodiments, whenever the quasi-resonant valley detection signal Qr_on indicates that the resonant voltage on the auxiliary winding of the transformer in the quasi-resonant switching power supply is in the adjacent T switching periods When the number of resonance valleys in each switching cycle is equal, the valley insertion enable signal Valley_insert_ENA1 is active in the next switching cycle immediately after the T switching cycles, and T is a fixed integer greater than or equal to 1. That is to say, count and compare the number of resonance valleys in each switching period of the resonance voltage on the auxiliary winding of the transformer in the quasi-resonant switching power supply based on the quasi-resonance valley detection signal Qr_on , if the resonant voltage on the auxiliary winding of the transformer in the quasi-resonant switching power supply has the same number of resonance valleys in each switching cycle in adjacent T switching cycles (for example, X1=X2 or X3=X4), then In the next switching cycle immediately after the T switching cycles, the valley insertion enable signal Valley_insert_ENA1 is in the active state, otherwise (for example, X1≠X2 or X3≠X4) in the next switching cycle immediately after the T switching cycles The valley insertion enable signal Valley_insert_ENA1 is in an invalid state in one switching cycle. In each switching cycle when the valley insertion enable signal Valley_insert_ENA1 is in an inactive state, when the clamp frequency control signal Qr_max is in an active state and the quasi-resonant valley detection signal Qr_on indicates that the resonance voltage on the auxiliary winding of the transformer in the quasi-resonant switching power supply reaches At the bottom of the mth resonant valley, the PWM signal changes from low level to high level, so that the switching tube in the quasi-resonant switching power supply changes from off state to on state, and m is an integer greater than or equal to 1. In the switching period when the valley insertion enable signal Valley_insert_ENA1 is in the active state, when the clamp frequency control signal Qr_max is in the active state and the quasi-resonant valley detection signal Qr_on indicates that the resonance voltage on the auxiliary winding of the transformer in the quasi-resonant switching power supply reaches the mth At +1 resonance valley, the PWM signal changes from low level to high level, so that the switching tube in the quasi-resonant switching power supply changes from off state to on state. It should be noted here that after the end of the current switching cycle in which the valley insertion enable signal Valley_insert_ENA1 is in the active state and before the start of the next switching cycle, the valley insertion enable signal Valley_insert_ENA1 needs to be reset to an inactive state. By adopting the frequency-shaking control scheme of valley insertion and bottom number comparison of adjacent fixed multi-period counting, the system operating frequency of the quasi-resonant switching power supply changes periodically in the manner of f5->f6->f5->f6.

FIG. 9 shows an example waveform diagram of multiple signals when the frequency shaking control circuit shown in FIG. 7 adopts the method of comparing adjacent pseudo-random multi-period counting valley numbers to implement the valley insertion frequency shaking control scheme. As shown in FIG. 7 and FIG. 9 , in some embodiments, when the quasi-resonant valley detection signal Qr_on indicates that the resonant voltage on the auxiliary winding of the transformer in the quasi-resonant switching power supply is in each of the adjacent T1 switching cycles When the number of resonant valleys in a switching period is not equal, the valley insertion enable signal Valley_insert_ENA1 is in an invalid state in the next switching period immediately after the T1 switching period, and immediately after the T1 switching period After the end of the next switching period, when the quasi-resonant valley detection signal Qr_on indicates that the resonance voltage on the auxiliary winding of the transformer in the quasi-resonant switching power supply is in the resonance valley in each switching period of the adjacent T2 switching periods When the numbers are equal, the valley insertion enable signal Valley_insert_ENA1 is in the active state in the next switching cycle immediately after the T2 switching cycles, T1 and T2 are both integers greater than or equal to 1 and T1≠T2. Here, T1 and T2 may be random numbers generated by a pseudo-random timing generator. That is to say, the resonance voltage on the auxiliary winding of the transformer in the quasi-resonant switching power supply is compared with the number of resonance valleys Y1 and Y2 in each switching cycle of adjacent T1 switching cycles, if Y1=Y2, Then the valley insertion enable signal Valley_insert_ENA1 is in a valid state in the next switching period immediately after the T1 switching period, otherwise the valley insertion enabling signal Valley_insert_ENA1 is in the next switching period immediately after the T1 switching period is in an invalid state. Next, compare the numbers Y3, Y4, and Y5 of the resonance valleys in each switching cycle of the resonant voltage on the auxiliary winding of the transformer in the adjacent T2 switching cycles, if Y3=Y4 = Y5, then the valley insertion enable signal Valley_insert_ENA1 is in an active state in the next switching cycle immediately after the T2 switching cycles, otherwise the valley insertion enable signal is in the next switching cycle immediately after the T1 switching cycles The enable signal Valley_insert_ENA1 is inactive. Through the above-mentioned frequency-shaking control scheme using adjacent pseudo-random multi-period counting valley bottom numbers, the system operating frequency of the switching power supply has no fixed period change in the way of f7->f8->f7->f8 (because T1 and T2 is a random number).

Through the frequency shaking control circuit for the quasi-resonant switching power supply according to the embodiment of the present invention, the quasi-resonant switching power supply can be operated in the quasi-resonant jitter valley conduction mode under a certain fixed load, so that the system of the quasi-resonant switching power supply can work The frequency varies regularly or randomly over successive switching cycles. Through the above valley bottoming frequency shaking control scheme, the energy distribution of the quasi-resonant switching power supply can not be concentrated on a single frequency, but the energy of the quasi-resonant switching power supply can be dispersed and distributed on multiple fundamental frequencies.

FIG. 10 shows a spectrum distribution diagram when a fixed multi-period counting method or an adjacent fixed multi-period counting valley-bottom number comparison method is used to realize the frequency-jittering scheme for bottoming out valleys. FIG. 11 shows a spectrum distribution diagram when a pseudo-random multi-period counting method or an adjacent pseudo-random multi-period counting valley number comparison method is used to implement the valley-inserting frequency shaking scheme. It can be seen that, through the above-mentioned valley bottoming frequency shaking control scheme, the energy of the quasi-resonant switching power supply can be distributed on multiple fundamental frequencies, and there are more high-frequency harmonic components, so that the energy radiated by the quasi-resonant switching power supply is greatly reduced, and finally meets the electromagnetic compatibility requirements of switching power supplies.

It should be noted that the frequency shaking control circuit for a quasi-resonant switching power supply according to an embodiment of the present invention can be applied to applications that use buck (BUCK), boost (BOOST), buck-boost (BUCK-BOOST), flyback ( Flyback), forward (Forward), and switching power supplies with asymmetrical half-bridge topologies.

The present invention may be embodied in other specific forms without departing from its spirit and essential characteristics. For example, the algorithms described in certain embodiments may be modified without departing from the basic spirit of the invention in terms of system architecture. Therefore, the present embodiments are to be considered in all respects as illustrative rather than restrictive, the scope of the present invention is defined by the appended claims rather than the above description, and, within the meaning and equivalents of the claims, All changes in scope are thereby embraced within the scope of the invention.

Claims (15)

1. A frequency shaking control circuit for a quasi-resonant switching power supply, configured to: Generating a quasi-resonant valley detection signal based on a resonant voltage characterization signal representing a resonant voltage on an auxiliary winding of a transformer in the quasi-resonant switching power supply; generating an upper clamping control signal for controlling the maximum operating frequency of the quasi-resonant switching power supply based on an output feedback control signal related to the output voltage of the quasi-resonant switching power supply; Generating a valley insertion 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 Based on the quasi-resonant valley bottom detection signal, the upper frequency clamp control signal, and the valley insertion enable signal, generate a switch tube for controlling the quasi-resonant switching power supply from an off state to a conduction state status of the turn-on control signal, where the The switching tube in the quasi-resonant switching power supply changes from the off state to the on state in the switching period when the valley insertion enabling signal is in an active state, which is different from when the valley insertion enabling signal is inactive. The moment in the switching cycle of the state from the off state to the on state. 2. The frequency shaking control circuit for a quasi-resonant switching power supply according to claim 1, further configured as: The valley insertion enable signal is generated by counting the switching period of the pulse width modulation signal. 3. The frequency shaking control circuit for a quasi-resonant switching power supply according to claim 2, wherein, whenever the count of the switching period of the pulse width modulation signal reaches N, at the Nth of the pulse width modulation signal The valley insertion enable signal is in an active state during +1 switching period, and N is a fixed integer greater than or equal to 1. 4. The frequency shaking control circuit for a quasi-resonant switching power supply according to claim 2, wherein, when the count of the switching cycle of the pulse width modulation signal reaches N1, at the N1+th of the pulse width modulation signal The valley insertion enable signal is in a valid state in one switching cycle, and After the N1+1th switching cycle of the PWM signal ends, when the recount of the switching cycle of the PWM signal reaches N2, in the N2+1th switching cycle of the PWM signal The valley insertion enable signal described in is in a valid state, both N1 and N2 are integers greater than or equal to 1 and N1≠N2. 5. The frequency shaking control circuit for a quasi-resonant switching power supply according to claim 4, wherein N1 and N2 are random numbers generated by a pseudo-random timing generator. 6. The frequency shaking control circuit for a quasi-resonant switching power supply according to claim 1, further configured as: 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-plugging enable signal; and The conduction control signal is generated based on the quasi-resonant valley-bottom conduction signal, wherein the conduction control signal is used to control the switching tube in the quasi-resonant switching power supply to operate in the transformer in the current switching cycle When the resonance voltage on the auxiliary winding reaches a predetermined number of resonance valleys, it changes from the off state to the on state. 7. The frequency shaking control circuit for a quasi-resonant switching power supply according to claim 1, wherein, in the switching period in which the valley insertion enable signal is in an invalid state, when the upper frequency clamping control signal is in an active state And when the quasi-resonant valley detection signal indicates that the resonance voltage on the auxiliary winding of the transformer reaches the mth resonance valley, the conduction control signal controls the switching tube in the quasi-resonant switching power supply from the off state to becomes conductive, and During the switching period when the valley insertion enabling signal is in the active state, when the upper frequency clamping control signal is in the active state and the quasi-resonant valley detection signal indicates that the resonance voltage on the auxiliary winding of the transformer reaches the m+th When there are n resonance valley bottoms, the conduction control signal controls the switch tube in the quasi-resonant switching power supply to change from an off state to an on state, and both m and n are integers greater than or equal to 1. 8. A frequency shaking control circuit for a quasi-resonant switching power supply, configured to: Generating a quasi-resonant valley detection signal based on a resonant voltage characterization signal representing a resonant voltage on an auxiliary winding of a transformer in the quasi-resonant switching power supply; generating an upper clamping control signal for controlling the maximum operating frequency of the quasi-resonant switching power supply based on an output feedback control signal related to the output voltage of the quasi-resonant switching power supply; Generating a valley insertion enable signal based on the quasi-resonant valley detection signal; and Based on the quasi-resonant valley bottom detection signal, the upper frequency clamp control signal, and the valley insertion enable signal, generate a signal for controlling the switching tube in the quasi-resonant switching power supply from an off state to a conduction state turn-on control signal, where The switching tube in the quasi-resonant switching power supply changes from the off state to the on state in the switching period when the valley insertion enabling signal is in an active state, which is different from when the valley insertion enabling signal is inactive. The moment in the switching cycle of the state from the off state to the on state. 9. The frequency shaking control circuit for a quasi-resonant switching power supply according to claim 8, further configured as: Generates the Enable signal for valley insertion. 10. The frequency shaking control circuit for a quasi-resonant switching power supply according to claim 9, wherein whenever the quasi-resonant valley detection signal indicates that the resonance voltage on the auxiliary winding of the transformer is at adjacent T When the number of resonance valleys in each switching period in the T switching periods is equal, the valley insertion enabling signal is in an active state in the next switching period immediately after the T switching periods, and T is greater than or A fixed integer equal to 1. 11. The frequency shaking control circuit for a quasi-resonant switching power supply according to claim 9, wherein when the quasi-resonant valley detection signal indicates that the resonance voltage on the auxiliary winding of the transformer is within the adjacent T1 When the number of resonance valleys in each switching period in the switching period is equal, the valley insertion enabling signal is in an active state in the next switching period immediately after the T1 switching periods, and After the end of the next switching cycle immediately after the T1 switching cycles, when the quasi-resonant valley bottom detection signal indicates that the resonant voltage on the auxiliary winding of the transformer is in the adjacent T2 switching cycles When the number of resonance valleys in each switching cycle is equal, the valley insertion enable signal is in an active state in the next switching cycle immediately after the T2 switching cycles, and both T1 and T2 are greater than or equal to 1 integer and T1≠T2. 12. The frequency shaking control circuit for a quasi-resonant switching power supply according to claim 11, wherein T1 and T2 are random numbers generated by a pseudo-random timing generator. 13. The frequency shaking control circuit for a quasi-resonant switching power supply according to claim 8, further configured as: 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-plugging enable signal; and The conduction control signal is generated based on the quasi-resonant valley-bottom conduction signal, wherein the conduction control signal is used to control the switching tube in the quasi-resonant switching power supply to operate in the transformer in the current switching cycle When the resonance voltage on the auxiliary winding reaches a predetermined number of resonance valleys, it changes from the off state to the on state. 14. The frequency shaking control circuit for a quasi-resonant switching power supply according to claim 8, wherein, in the switching cycle in which the valley insertion enable signal is in an invalid state, when the upper clamping control signal is in an active state And when the quasi-resonant valley detection signal indicates that the resonance voltage on the auxiliary winding of the transformer reaches the mth resonance valley, the conduction control signal controls the switching tube in the quasi-resonant switching power supply from the off state to becomes conductive, and During the switching period when the valley insertion enabling signal is in the active state, when the upper frequency clamping control signal is in the active state and the quasi-resonant valley detection signal indicates that the resonance voltage on the auxiliary winding of the transformer reaches the m+th When there are n resonance valley bottoms, the conduction control signal controls the switch tube in the quasi-resonant switching power supply to change from an off state to an on state, and both m and n are integers greater than or equal to 1. 15. A quasi-resonant switching power supply, comprising the frequency shaking control circuit for a quasi-resonant switching power supply according to any one of claims 1 to 14.

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