Control method and circuit for switch power source, and switch power source

Abstract

A control method and circuit for a switch power source, and a switch power source, which relate to the technical field of switch power sources. In the solution, a resonance period signal of a switch power source is detected in real time; and a delay time is superimposed on the resonance period signal, so that a control signal controls a primary-side power switch tube of the switch power source to turn on within a preset range near a target valley of a resonance waveform according to the resonance period signal and a delay signal, wherein the delay time is related to a first parameter and a second parameter, the first parameter being a set value that changes over time within a certain range, and the second parameter being a function related to a resonance period of the switch power source. It can be seen that in the present application, the resonance period signal of the switch power source can be detected in real time, and the primary-side power switch tube of the switch power source can be controlled to reliably turn on within the preset range near the target valley according to the resonance period signal of the switch power source and the delay time, such that the control accuracy is improved.

Description

A control method and circuit for a switching power supply, and a switching power supply Technical Field

[0001] The present invention relates to the technical field of switching power supplies, and in particular to a control method and circuit for a switching power supply, and a switching power supply. Background Art

[0002] In a flyback switching power supply system, after the primary power switch turns off, the secondary diode turns on, and the energy stored in the transformer begins to transfer to the secondary side. After the energy transfer is complete, the secondary diode turns off, and the transformer's magnetizing inductance and the parasitic capacitance of the primary power switch produce a decaying resonance. This resonance persists until the primary power switch turns on again.

[0003] To reduce the loss of the primary power switch, the prior art typically uses a valley-locked QR (quasi-resonant) mode to control the primary power switch to conduct. Specifically, the primary power switch is controlled to conduct at a valley of the resonant waveform (when the primary power switch is a MOS transistor, the Vds of the MOS (metal-oxide-semiconductor field-effect transistor) transistor is relatively large at this time). This can reduce the loss of the primary power switch and thereby improve the efficiency of the system. However, during system operation, if the same valley of the resonant waveform is selected each time to turn on the primary power switch, the system's switching frequency will remain unchanged. In this case, the system's EMI (electromagnetic interference) performance will be poor.

[0004] In order to further improve the EMI performance of the system, the negative half-cycle resonant period frequency jittering is superimposed on the QR mode, specifically to control the primary power switch tube to be turned on at any moment in the negative half-cycle where the selected valley is located. For example, when the selected valley is the second valley, the primary power switch tube can be controlled to be turned on at any moment on the left side of the second valley and within the negative half-cycle range, or to be turned on at any moment on the right side of the second valley and within the negative half-cycle range. The specific implementation method is: when the zero point before the second valley in the resonant waveform is detected, the primary power switch tube is controlled to be turned on by a preset delay time (this preset time is a variable value and is not greater than 1 / 2 of the resonant period to ensure that the primary power switch tube is turned on in the negative half-cycle where the second valley is located), so that the switching frequency of the system is variable, thereby improving the EMI performance of the system.

[0005] However, for a flyback switching power supply system with a wide input range and multiple voltage outputs, the corresponding resonant periods are different under different input / output voltages and different load conditions. Therefore, when using the above method to control the conduction of the primary power switch tube, it is possible that the primary power switch tube will be turned on in the positive half cycle of the resonant waveform. That is, the method in the prior art cannot make the primary power switch tube accurately turned on at a certain moment in the negative half cycle of the selected valley bottom, and the accuracy is poor.

[0006] Summary of the Invention

[0007] The purpose of this application is to provide a control method, circuit and switching power supply of a switching power supply, which can detect the resonant periodic signal of the switching power supply in real time, and control the primary power switch tube of the switching power supply to reliably turn on within a preset range near the target valley bottom according to the resonant periodic signal and delay time of the switching power supply, thereby improving the accuracy of control.

[0008] To solve the above technical problems, the present application provides a control method for a switching power supply, comprising:

[0009] Real-time detection of the resonant periodic signal of the switching power supply;

[0010] A delay time is superimposed on the resonant periodic signal so that the control signal controls the primary power switch of the switching power supply to be turned on within a preset range near the target valley bottom of the resonant waveform according to the resonant periodic signal and the delay signal;

[0011] The delay time is related to a first parameter and a second parameter, the first parameter is a set value that changes with time within a certain range, and the second parameter is a function related to the resonant period of the switching power supply.

[0012] Preferably, the preset range is related to a periodic variation function related to the first parameter;

[0013] A delay time is superimposed on the resonant periodic signal so that the control signal controls the primary power switch tube of the switching power supply to be turned on within a preset range near the target valley bottom of the resonant waveform according to the resonant periodic signal and the delay signal, including:

[0014] When the function value of the periodic transformation function related to the first parameter is zero, adjusting the second parameter so as to make the control signal correspond to a reference position at the center, left side, or right side of a target valley in the resonant waveform according to the resonant period signal and the delay signal;

[0015] The function value of the periodic variation function of the first parameter is superimposed on the reference position, so that the control signal controls the primary power switch tube of the switching power supply to be turned on within a preset range of the target valley.

[0016] Preferably, adjusting the second parameter includes:

[0017] Obtaining a resonance period of the resonance waveform;

[0018] The second parameter is adaptively adjusted according to the resonant period, so that the control signal controls the primary power switch to be turned on at the target valley bottom.

[0019] Preferably, obtaining the resonance period of the resonance waveform includes:

[0020] Obtaining the time between a plurality of consecutive troughs or consecutive peaks or consecutive zero crossings in the resonant waveform;

[0021] The resonance period is calculated according to the time and the number of the troughs or the peaks or the zero-crossing points.

[0022] Preferably, adjusting the second parameter includes:

[0023] Obtaining operating parameters of the switching power supply at preset time intervals;

[0024] The second parameter is determined according to the operating parameter and a mapping relationship between the preset operating parameter and the second parameter.

[0025] Preferably, after obtaining the operating parameters of the switching power supply at preset time intervals, the method further includes:

[0026] Determining whether the operating parameters have changed;

[0027] If there is a change, the step of determining the second parameter according to the working parameter and the mapping relationship between the preset working parameter and the second parameter is entered.

[0028] Preferably, determining whether the operating parameter has changed includes:

[0029] determining whether the level of the operating parameter has changed;

[0030] If the level changes, it is determined that the operating parameter has changed.

[0031] Preferably, the operating parameters include a combination of one or more of the primary input voltage, the secondary output voltage and the load value of the switching power supply.

[0032] Preferably, the operating parameters include the primary input voltage and the secondary output voltage of the switching power supply;

[0033] Obtaining operating parameters of the switching power supply includes:

[0034] When the primary power switch tube is turned on, the primary input voltage is calculated according to the voltage of the auxiliary winding, the number of turns of the auxiliary winding and the number of turns of the primary winding;

[0035] When the secondary switch is turned on, the secondary output voltage is calculated according to the voltage of the auxiliary winding, the number of turns of the auxiliary winding and the number of turns of the secondary winding;

[0036] The auxiliary winding and the primary winding share a common ground.

[0037] Preferably, when the operating parameter includes a load value;

[0038] Obtaining operating parameters of the switching power supply includes:

[0039] Obtaining the switching frequency of the primary power switch tube in the switching power supply;

[0040] determining the load value according to the switching frequency;

[0041] The load value is positively correlated with the switching frequency.

[0042] Preferably, a delay time is superimposed on the resonant periodic signal so that the control signal controls the primary power switch of the switching power supply to be turned on within a preset range near the target valley bottom of the resonant waveform according to the resonant periodic signal and the delay signal, including:

[0043] After determining the target valley according to the load value of the switching power supply, detecting a previous zero-crossing point of a valley previous to the target valley;

[0044] The moment when the control signal corresponding to the previous zero-crossing point is delayed by the delay time is used as the turn-on moment, so that the control signal controls the primary power switch tube to be turned on at the turn-on moment.

[0045] To solve the above technical problems, the present application also provides a control circuit of a switching power supply, comprising:

[0046] A detection unit, configured to detect the resonant periodic signal of the switching power supply in real time;

[0047] a control unit, configured to superimpose a delay time on the resonant periodic signal so that the control signal controls the primary power switch of the switching power supply to turn on within a preset range near a target valley bottom of the resonant waveform according to the resonant periodic signal and the delayed signal;

[0048] The delay time is related to a first parameter and a second parameter, the first parameter is a set value that changes with time within a certain range, and the second parameter is a function related to the resonant period of the switching power supply.

[0049] Preferably, the control unit comprises:

[0050] a resonance valley corresponding circuit, configured to adjust the second parameter when the function value of the periodic transformation function associated with the first parameter is zero, so that the control signal corresponds to a reference position at the center, left side, or right side of a target valley in the resonance waveform based on the resonance period signal and the delay signal;

[0051] The frequency jittering circuit is used to superimpose the function value of the periodic variation function of the first parameter on the reference position, so that the control signal controls the primary power switch tube of the switching power supply to be turned on within a preset range of the target valley.

[0052] In order to solve the above technical problems, the present application also provides a switching power supply, including the control circuit of the switching power supply described above.

[0053] The present application provides a control method for a switching power supply, which relates to the technical field of switching power supplies. In this solution, the resonant periodic signal of the switching power supply is detected in real time; a delay time is superimposed on the resonant periodic signal, so that the control signal controls the primary power switch tube of the switching power supply to be turned on within a preset range near the target valley bottom of the resonant waveform according to the resonant periodic signal and the delay signal, wherein the delay time is related to a first parameter and a second parameter, and the first parameter is a set value that changes with time within a certain range, and the second parameter is a function related to the resonant period of the switching power supply. It can be seen that the present application can detect the resonant periodic signal of the switching power supply in real time, and control the primary power switch tube of the switching power supply to be reliably turned on within a preset range near the target valley bottom according to the resonant periodic signal and the delay time of the switching power supply, thereby improving the accuracy of control.

[0054] The present application also provides a control circuit for a switching power supply and a switching power supply, which have the same beneficial effects as the control method for the switching power supply described above. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the prior art and the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0056] FIG1a is a schematic diagram of a first waveform in the prior art;

[0057] FIG1b is a second waveform diagram in the prior art;

[0058] FIG2 is a flow chart of a method for controlling a switching power supply provided by the present application;

[0059] FIG3 is a schematic diagram of a partial structure of a switching power supply provided by the present application;

[0060] FIG4 is a waveform diagram provided by the present application;

[0061] FIG5 is a control schematic diagram of a switching power supply provided by the present application;

[0062] FIG6a is a schematic diagram of operating waveforms of a switching power supply provided by the present application;

[0063] FIG6 b is a schematic diagram of a method for generating a resonant periodic signal provided by the present application;

[0064] FIG6c is a schematic diagram of a control signal provided by the present application;

[0065] FIG6 d is a waveform diagram of a periodic function related to the first parameter provided in this application;

[0066] FIG6e is a waveform diagram of the first primary power switch tube provided by the present application being turned on on the left side of the target valley;

[0067] FIG6 f is a waveform diagram of the first primary power switch tube provided by the present application being turned on at the target valley bottom;

[0068] FIG6g is a waveform diagram of the first primary power switch tube provided by the present application being turned on on the right side of the target valley;

[0069] FIG7 a is a schematic diagram of another operating waveform of the switching power supply provided by the present application;

[0070] FIG7 b is a schematic diagram of another control signal provided by the present application;

[0071] FIG7c is a schematic diagram of a function related to a second parameter provided by the present application;

[0072] FIG7 d is a waveform diagram of the second primary power switch tube provided by the present application being turned on on the left side of the target valley;

[0073] FIG7e is a waveform diagram of the second primary power switch tube provided by the present application being turned on at the target valley bottom;

[0074] FIG7f is a waveform diagram of the second primary power switch tube provided by the present application being turned on on the right side of the target valley;

[0075] FIG8 is a structural block diagram of a control circuit of a switching power supply provided in the present application. DETAILED DESCRIPTION

[0076] The core of this application is to provide a control method, circuit and switching power supply of a switching power supply, which can detect the resonant periodic signal of the switching power supply in real time, and control the primary power switch tube of the switching power supply to reliably turn on within a preset range near the target valley bottom according to the resonant periodic signal and delay time of the switching power supply, thereby improving the accuracy of control.

[0077] To make the purpose, technical solutions, and advantages of the embodiments of this application more clear, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the drawings in the embodiments of this application. Obviously, the described embodiments are part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0078] Please refer to Figures 1a and 1b. Figure 1a is a schematic diagram of the first waveform in the prior art, and Figure 1b is a schematic diagram of the second waveform in the prior art. In Figures 1a and 1b, the left side represents the conduction time of the primary power switch tube, the higher middle portion represents the conduction time of the secondary switch tube, and the attenuated sinusoidal waveform on the right side represents the resonant waveform generated after the secondary switch tube is turned off. Both Figures 1a and 1b control the primary power switch tube to conduct in the negative half-cycle of the third valley. However, the experimental results using the control method in the prior art are as follows: in Figure 1a, the primary power switch tube conducts in the negative half-cycle position slightly to the left of the third valley, while in Figure 1b, the primary power switch tube conducts in a position close to or even at the second peak on the left side of the third valley, which does not meet the negative half-cycle conduction requirement.

[0079] Please refer to FIG. 2 , which is a flow chart of a method for controlling a switching power supply provided by the present application. The method includes:

[0080] S11: Real-time detection of the resonant periodic signal of the switching power supply;

[0081] Specifically, the resonant periodic signal here represents the resonant signal of the switching power supply, which can specifically represent the situation where the resonant waveform passes through the zero point (such as when the resonant waveform is in the positive half cycle, the resonant periodic signal is high level, and when the resonant waveform is in the negative half cycle, the resonant periodic signal is low level). For details, please refer to Tdem in the following first and second embodiments.

[0082] S12: superimposing a delay time on the resonant periodic signal so that the control signal controls the primary power switch of the switching power supply to turn on within a preset range near the target valley bottom of the resonant waveform according to the resonant periodic signal and the delay signal;

[0083] The delay time is related to a first parameter and a second parameter. The first parameter is a set value that changes with time within a certain range, and the second parameter is a function related to the resonance period of the switching power supply.

[0084] After the above-mentioned detection of the resonant periodic signal, a delay time is superimposed after a certain resonant period, so that the control signal generated at the resonant periodic signal controls the primary power switch tube to turn on within a preset range near the target valley bottom of the resonant waveform after the delay time.

[0085] Specifically, to improve the EMI performance of the system, the primary power switch tube in the present application is turned on at different positions in the negative half-cycle of the target valley in two adjacent cycles. The preset range of the target valley does not exceed the negative half-cycle of the target valley. That is, the "turning on within the preset range of the target valley" here means controlling the primary power switch tube to oscillate and turn on within the preset range of the target valley in different cycles, with the turn-on position being different between two adjacent cycles.

[0086] Since the above-mentioned delay time is related to the first parameter and the second parameter, and the first parameter is a setting that changes with time, and the second parameter is a function related to the resonant period, the control method in the present application can determine the delay time according to the resonant period to determine the conduction time of the primary power switch tube, thereby improving the reliability of the conduction of the primary power switch tube.

[0087] As a preferred embodiment, the preset range is related to a periodic variation function related to the first parameter;

[0088] A delay time is superimposed on the resonant periodic signal so that the control signal controls the primary power switch of the switching power supply to turn on within a preset range near the target valley bottom of the resonant waveform according to the resonant periodic signal and the delay signal, including:

[0089] When the function value of the periodic transformation function related to the first parameter is zero, adjusting the second parameter so as to make the control signal correspond to a reference position at the center, left side, or right side of the target valley in the resonant waveform according to the resonant period signal and the delay signal;

[0090] The function value of the periodically varying function of the first parameter is superimposed on the reference position, so that the control signal controls the primary power switch tube of the switching power supply to be turned on within a preset range of the target valley.

[0091] Specifically, when the periodic change function corresponding to the above-mentioned first parameter is related to the preset range, it can be specifically when the periodic change function is a frequency jittering amount in the delay time (in a specific embodiment, the first parameter is m in Figure 6d, and the periodic change function related to the first parameter is Ij(m) in Figure 6d), the role of the first parameter is to ensure that the primary power switch tube is turned on within a range near the target valley bottom, so that it is not fixed at one position of the target valley bottom.

[0092] At this time, if the function value of the periodic variation function corresponding to the first parameter is zero (that is, when the corresponding Ij(m) in FIG6d is zero, then m can be 1 or 2*2 x-2 or 2 x ), indicating that the frequency jittering amount superimposed in the delay time is zero, that is, at this time, the primary power switch tube should be accurately turned on at the target valley bottom or at any reference position to the left or right of the target valley bottom. Therefore, if the primary power switch tube is not accurately turned on at the reference position at this time, it means that the second parameter is inaccurate. Therefore, when the function value of the periodic variation function corresponding to the first parameter is zero, the second parameter is adjusted to ensure that after the frequency jittering amount is superimposed, the primary power switch tube can be accurately turned on at any time within a preset range near the target valley bottom.

[0093] After aligning the control signal with a reference position near the target valley, a periodically varying function related to the first parameter is superimposed on the reference position, causing the control signal to periodically shift near the reference position. Consequently, when the primary power switch is turned on based on this control signal, the primary switch oscillates around the reference position. In one embodiment, the reference position is the center of the target valley.

[0094] As a preferred embodiment, adjusting the second parameter includes:

[0095] Obtain the resonant period of the resonant waveform;

[0096] The second parameter is adaptively adjusted according to the resonance period so that the control signal controls the primary power switch tube to be turned on at the target valley bottom.

[0097] Specifically, since the second parameter is a function related to the resonant period (specifically, refer to the following embodiment, the second parameter is k), therefore, one way to adjust the second parameter in the present application is: adaptively adjust the second parameter according to the resonant waveform, the purpose of which is to make the control signal accurately turned on at the reference position on the left or right side of the target valley center or the periodic change function corresponding to the first parameter when the function value is zero.

[0098] As a preferred embodiment, obtaining the resonant period of the resonant waveform includes:

[0099] Obtain the time between several consecutive troughs or consecutive peaks or consecutive zero crossings in the resonant waveform;

[0100] Calculate the resonant period based on the time and the number of troughs, peaks or zero crossings.

[0101] This embodiment aims to obtain the resonance period through a specific implementation method. Specifically, the resonance period can be calculated based on the time between several consecutive peaks and peaks, or the time between several consecutive troughs and troughs, or the time between several consecutive zero crossings in the resonance waveform, as well as the corresponding number of peaks, or the number of troughs or the number of zero crossings.

[0102] For example, if the sum of the time of N consecutive zero crossings is t1, then the resonant period T = 2t1 / N (there are two zero crossings in each cycle, one from the positive half cycle to the negative half cycle, and one from the negative half cycle to the positive half cycle). For example, if the sum of the time of n consecutive troughs is t2, then the resonant period T = t2 / n. The calculation method for peaks is the same as that for troughs, and this application will not repeat it here.

[0103] In order to ensure the accuracy and reliability of the control of the switching power supply, in this application, the resonance period of the switching power supply is detected at regular intervals to update the resonance period of the switching power supply at any time, so as to adjust the second parameter according to the latest resonance period detected at the moment.

[0104] As a preferred embodiment, adjusting the second parameter includes:

[0105] Obtaining the operating parameters of the switching power supply at preset intervals;

[0106] The second parameter is determined according to the working parameter and the mapping relationship between the preset working parameter and the second parameter.

[0107] This embodiment provides another method for adjusting a second parameter. Specifically, a mapping relationship between a preset operating parameter and a second parameter is preset. After determining the operating parameters of the switching power supply, the preset operating parameter-delay time mapping relationship is searched based on the operating parameters of the switching power supply to determine the second parameter corresponding to the operating parameter. The delay time is then adjusted based on this second parameter so that when the function value of the periodically varying function corresponding to the first parameter reaches zero, the control signal controls the primary power switch to reliably conduct at the target valley.

[0108] As a preferred embodiment, after obtaining the operating parameters of the switching power supply at predetermined intervals, the method further includes:

[0109] Determine whether the working parameters have changed;

[0110] If there is a change, the step of determining the second parameter according to the working parameter and the mapping relationship between the preset working parameter and the second parameter is entered.

[0111] Specifically, in this embodiment, the cause of the change in the second parameter is typically a change in the operating parameters of the switching power supply. Therefore, the present application also detects the operating parameters of the switching power supply and, when a change occurs, proceeds to the step of determining the second parameter. If the time interval between two consecutive operating parameter detections is sufficiently short, this is equivalent to real-time monitoring of the operating parameters of the switching power supply.

[0112] As a preferred embodiment, determining whether the operating parameters have changed includes:

[0113] Determine whether the level of the working parameters has changed;

[0114] If the level changes, it is determined that the working parameters have changed.

[0115] Specifically, in order to prevent the determination of the second parameter from being triggered when the change in the operating parameter is extremely small, the second parameter needs to be determined frequently, which consumes a lot of power in the processor.

[0116] Therefore, in this application, the working parameters are divided into different levels. At this time, the specific implementation method of judging whether the working parameters have changed is: judging whether the level of the working parameters has changed, and when it has changed, it is determined that the working parameters have changed. Only then is the step of determining the second parameter triggered, avoiding frequent triggering of the step of determining the second parameter, which can reduce the power consumption of the processor to a certain extent.

[0117] As a preferred embodiment, the operating parameters include a combination of one or more of the primary input voltage, the secondary output voltage and the load value of the switching power supply.

[0118] This embodiment aims to limit the specific implementation of the operating parameters. Specifically, the operating parameters may be, but are not limited to, the primary input voltage, secondary output voltage, and load value of the switching power supply.

[0119] Among them, the range of the primary input voltage can be but is not limited to 90VAc~265Vac, and the range of the output voltage can be but is not limited to 3.3V~21V. When the working parameters are divided into levels as mentioned above, the value ranges of the primary input voltage, the secondary output voltage and the load value can be divided into several gears (levels) according to actual needs. The specific division method is not specifically limited in this application.

[0120] As a preferred embodiment, the operating parameters include the primary input voltage and the secondary output voltage of the switching power supply;

[0121] Get the operating parameters of the switching power supply, including:

[0122] When the primary power switch is turned on, the primary input voltage is calculated based on the voltage of the auxiliary winding, the number of turns of the auxiliary winding and the number of turns of the primary winding;

[0123] When the secondary switch is turned on, the secondary output voltage is calculated based on the voltage of the auxiliary winding, the number of turns of the auxiliary winding and the number of turns of the secondary winding;

[0124] The auxiliary winding and the primary winding share a common ground.

[0125] This embodiment aims to limit the specific implementation method of calculating the primary input voltage and the secondary output voltage. Specifically, the specific method of calculating the primary input voltage can be to calculate the primary input voltage based on the voltage of the auxiliary winding, the number of turns of the auxiliary winding and the number of turns of the primary winding when the primary power switch tube is turned on. Specifically, refer to Figure 3, which is a partial structural diagram of a switching power supply provided by this application. The primary input voltage is detected by the pull-up resistor R DEM Derivation, specifically: Among them, Vin is the primary input voltage, I DEMAG is the current on the pull-up resistor, R DEM is the pull-up resistor connected to the auxiliary winding, Np is the number of turns of the primary winding, and Na is the number of turns of the auxiliary winding.

[0126] The specific method for calculating the secondary output voltage is to calculate the secondary output voltage according to the voltage of the auxiliary winding, the number of turns of the auxiliary winding, and the number of turns of the secondary winding when the secondary switch tube is turned on. For details, please refer to Figure 4, which is a waveform diagram provided by this application. The secondary output voltage is obtained by detecting V DEM The voltage is obtained. Among them, Tons is the time period when the secondary side switch tube is turned on, Toff is the time period when the secondary side switch tube is turned off but the primary side power switch tube of the next cycle has not yet turned on (that is, the time period when resonance occurs), and Gate\Tonp in Figure 4 is the time period when the primary side power switch tube is turned on. At this time, Wherein, Vo is the secondary output voltage, Vaux is the voltage on the auxiliary winding when the secondary switch is turned on, Na is the number of turns of the auxiliary winding, and Ns is the number of turns of the secondary winding.

[0127] As a preferred embodiment, when the operating parameter includes a load value;

[0128] Get the operating parameters of the switching power supply, including:

[0129] Get the switching frequency of the primary power switch tube in the switching power supply;

[0130] Determine the load value according to the switching frequency;

[0131] Among them, the load value is positively correlated with the switching frequency.

[0132] This embodiment aims to limit the specific implementation method of determining the load value. Specifically, the load value of the current switching power supply is determined according to the switching frequency of the primary power switch tube in the switching power supply. Among them, the switching frequency of the primary power switch tube is positively correlated with the load value. Specifically, the switching period of the primary power switch tube is the primary power switch tube conduction time + the secondary power switch tube conduction time + the resonance time (specifically, the time period between the start of resonance and the turn-on of the primary power switch tube in the determined target valley). Currently, when the switching power supply is lightly loaded, the valley at the back of the resonance waveform is selected. At this time, the corresponding switching period is larger and the switching frequency is smaller. When the switching power supply is heavily loaded, the valley at the front of the resonance waveform is selected. At this time, the corresponding switching period is smaller and the switching frequency is larger. Therefore, if it is necessary to determine the load value carried by the switching power supply, it is only necessary to determine it according to the switching frequency of the current primary power switch tube.

[0133] Of course, the above is only one implementation method provided by this embodiment. The load value may also be directly detected by a detection device, and this application does not limit this.

[0134] As a preferred embodiment, a delay time is superimposed on the resonant periodic signal so that the control signal controls the primary power switch of the switching power supply to turn on within a preset range near the target valley bottom of the resonant waveform according to the resonant periodic signal and the delay signal, including:

[0135] After determining the target valley according to the load value of the switching power supply, detecting the previous zero-crossing point of the previous valley before the target valley;

[0136] The moment when the control signal corresponding to the previous zero-crossing point is delayed by the delay time is used as the turn-on moment, so that the control signal controls the primary power switch tube to be turned on at the turn-on moment.

[0137] Specifically, the determination of the turn-on moment in the present application can be divided into several steps. First, the zero-crossing point of the resonant waveform is detected to determine the position of the target valley. The specific method for determining the turn-on moment is: determine a valley before the target valley, and then detect a zero-crossing moment before the determined valley, and the moment of delaying the delay time according to this zero-crossing moment is the turn-on moment, and the turn-on moment is any moment near the target valley. Through the method in the present application, the target valley can be accurately determined, and the turn-on frequency of the primary power switch tube in the switching power supply can be continuously adjusted to avoid the frequency of the primary power switch tube remaining unchanged, thereby improving the EMI performance of the switching power supply.

[0138] The design goal of this application is to control the primary power switch to conduct in the negative half-cycle of the target valley. To this end, this application provides two embodiments. For the first embodiment, please refer to Figures 5 and 6a-6g. Figure 5 is a control principle diagram of a switching power supply provided by this application, Figure 6a is a schematic diagram of the operating waveform of a switching power supply provided by this application, Figure 6b is a schematic diagram of a resonant periodic signal generation provided by this application, Figure 6c is a schematic diagram of a control signal provided by this application, and Figure 6d is a waveform diagram of a periodic function related to the first parameter provided by this application. The first embodiment is described as follows:

[0139] Tdem in Figure 6a is the result of comparing DEMAG in Figure 6b with 0V. That is, Tdem is a signal representing the zero-crossing point of the resonant waveform. In this embodiment, Tdem is used as the resonant period signal described above. Vds in Figure 6a is the resonant waveform of the primary power switch.

[0140] In Figure 6c, the input CLK of the x-bits jitter counter can be an oscillator output or a SW signal. The x-bits jitter counter counts CLK and outputs the count result m, where m ranges from 1 to 2x. The x-bits jitter counter can count cyclically, with m = 2 x When m=1 after the next CLK (m is the first parameter described above), the implementation of D to I in FIG6c can be shown in FIG6d, where m is converted into output current Ij(m), where the range of Ij(m) is 2 x-2 *Istep~-(2 x-2 -1)*Istep (where Ij(m) is the above-mentioned periodic function related to the first parameter).

[0141] The Valley Lockout module selects the nth valley to conduct according to the load of the switching power supply (specifically, the COMP voltage in Figure 5); (that is, the valley lockout is determined by the load).

[0142] The Current Table module detects the primary input voltage and the secondary output voltage through DEMAG. Based on the primary input voltage, the secondary output voltage and the target Valley(n), it selects the preset output current It(k), so that m=1 or m=2*2. x-2 When Tpulse (control signal) corresponds to the valley bottom, if the primary input voltage, secondary output voltage, and system load remain unchanged, then k (the second parameter) remains unchanged.

[0143] In the n-1th Tdem n-1 After the rising edge, after a delay of t d(m,k), generates the nth Tpulse n (Tpulse n =Tdem n-1 +t d (m,k)). Where, t d The specific implementation of (m,k) can be: d (m,k)=C*Vref / [Ij(m)+It(k)].

[0144] At the nth Tpulse n On the rising edge, the primary power switch is turned on.

[0145] If m=1 or m=2*2 x-2 When Tpulse n It is turned on at the reference position of the negative half cycle corresponding to the target valley bottom. The specific reference position can be the target valley bottom, and Ij(m) changes periodically, so that the primary power switch tube can be oscillated and turned on in the negative half cycle area.

[0146] FIG6e is a waveform diagram of the first primary power switch tube provided by the present application being turned on on the left side of the target valley. x-2 , Ij(m) is positive, and Tpulse is on the left side of the reference position (target valley bottom).

[0147] FIG6f is a waveform diagram of the first primary power switch tube provided by the present application being turned on at the target valley bottom. At this time, m=1or 2*2 x-2 , Ij(m) is zero, and Tpulse is at the reference position (target valley bottom).

[0148] FIG6g is a waveform diagram of the first primary power switch tube provided by this application being turned on at the right side of the target valley. x-2 , Ij(m) is a negative value, and Tpulse is on the right side of the reference position (target valley bottom).

[0149] For the second embodiment, please refer to FIG. 7a to FIG. 7f . FIG. 7a is a schematic diagram of another operating waveform of the switching power supply provided in the present application. FIG. 7b is a schematic diagram of another control signal provided in the present application. FIG. 7c is a schematic diagram of a function related to the second parameter provided in the present application. The second embodiment is described as follows:

[0150] This embodiment adopts the DLL (Delay-Locked Loop, delay phase-locked loop) principle, comparing Tpulse n (rising edge) and the timing relationship of the reference signal, dynamically adjust td(m,k) so that when m is a certain value (the function value of the function corresponding to m is zero), Tpulse n Corresponding to the bottom.

[0151] Sample Tdem and generate Tmid (Tdem falling edge + 0.75*tdem) based on Tdem. As shown in FIG7a , the falling edge of Tmid corresponds to the valley bottom of the resonant waveform.

[0152] In m=1or m=2*2 x-2 When comparing the position relationship between the rising edge of Tpulse and the falling edge of Tmid, adjust k in each SW cycle, and the range of k is 1 to 2 y (y is the value of the counter).

[0153] If the falling edge of Tmid precedes the rising edge of Tpulse, k n =k n-1 +1;

[0154] If the falling edge of Tmid lags behind the rising edge of Tpulse, k n =k n-1 -1;

[0155] In m≠1and m≠2*2 x-2 Hour, k n =k n-1 .

[0156] The D to I module in Figure 7b, as shown in Figure 7c, converts k into output current It(k). The range of It(k) is Iini~Iini+(2 y -1)*Itune.

[0157] Finally, after several cycles of dynamic adjustment of td(m,k), when m=1or m=2*2 x-2 When (that is, when the function value Ij(m) of the periodic function related to the first parameter m is zero), the rising edge of Tpulse will be at the bottom and dynamically follow the change of the resonant period when the working condition changes.

[0158] If m=1 or m=2*2 x-2 When (the function value of the periodic function corresponding to the first parameter is zero), Tpulse n The primary power switch tube is turned on at the reference position of the negative half cycle corresponding to the target valley bottom. The specific reference position can be the target valley bottom, and Ij(m) changes periodically, so that the primary power switch tube can be turned on in the negative half cycle area of ​​the target valley bottom.

[0159] FIG7d is a waveform diagram of the second primary power switch provided by the present application when it is turned on on the left side of the target valley. x-2 , Ij(m) is positive, and Tpulse is on the left side of the reference position (target valley bottom).

[0160] FIG7e is a waveform diagram of the second primary power switch provided by the present application when it is turned on at the target valley bottom. x-2 , Ij(m) is zero, and Tpulse is at the reference position (target valley bottom).

[0161] FIG7f is a waveform diagram of the second primary power switch provided by the present application being turned on at the right side of the target valley. x-2 , Ij(m) is a negative value, and Tpulse is on the right side of the reference position (target valley bottom).

[0162] To solve the above technical problems, the present application further provides a control circuit for a switching power supply. Please refer to FIG8 , which is a structural block diagram of a control circuit for a switching power supply provided by the present application. The circuit includes:

[0163] The detection unit 81 is used to detect the resonant periodic signal of the switching power supply in real time;

[0164] A control unit 82 is configured to superimpose a delay time on the resonant periodic signal so that the control signal controls the primary power switch of the switching power supply to conduct within a preset range near a target valley bottom of the resonant waveform according to the resonant periodic signal and the delay signal;

[0165] The delay time is related to a first parameter and a second parameter. The first parameter is a set value that changes with time within a certain range, and the second parameter is a function related to the resonance period of the switching power supply.

[0166] As a preferred embodiment, the control unit includes:

[0167] a resonance valley corresponding circuit, configured to adjust a second parameter when the function value of the periodic transformation function associated with the first parameter is zero, so that the control signal corresponds to a reference position at the center, left side, or right side of a target valley in the resonance waveform according to the resonance period signal and the delay signal;

[0168] The frequency jittering circuit is used to superimpose the function value of the periodic variation function of the first parameter on the reference position, so that the control signal controls the primary power switch tube of the switching power supply to be turned on within a preset range of the target valley.

[0169] For an introduction to the control circuit of the switching power supply, please refer to the above embodiments, and this application will not go into details here.

[0170] To solve the above technical problems, the present application further provides a switching power supply, including the above switching power supply control circuit. For an introduction to the switching power supply, please refer to the above embodiments, and this application will not elaborate on them here.

[0171] It should also be noted that, in this specification, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of additional identical elements in the process, method, article, or apparatus comprising the element.

[0172] The above description of the disclosed embodiments is intended to enable one skilled in the art to implement or use the present application. Various modifications to these embodiments will be readily apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application is not limited to the embodiments shown herein, but is intended to conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for controlling a switching power supply, characterized in that: include: Real-time detection of the resonant periodic signal of the switching power supply; A delay time is superimposed on the resonant periodic signal, so that the control signal controls the primary power switch tube of the switching power supply to be turned on within a preset range near the target valley bottom of the resonant waveform according to the resonant periodic signal and the delay signal; The delay time is related to a first parameter and a second parameter, the first parameter is a set value that varies with time within a certain range, and the second parameter is a function related to the resonance period of the switching power supply.

2. The control method of the switching power supply according to claim 1, characterized in that: The preset range is related to a periodic variation function related to the first parameter; A delay time is superimposed on the resonant periodic signal so that the control signal controls the primary power switch tube of the switching power supply to be turned on within a preset range near the target valley bottom of the resonant waveform according to the resonant periodic signal and the delay signal, including: When the function value of the periodic transformation function related to the first parameter is zero, adjusting the second parameter so as to make the control signal correspond to a reference position at the center or the left side or the right side of a target valley bottom in the resonant waveform according to the resonant period signal and the delay signal; The function value of the periodic variation function of the first parameter is superimposed on the reference position, so that the control signal controls the primary power switch tube of the switching power supply to be turned on within a preset range of the target valley bottom.

3. The control method of the switching power supply according to claim 2, characterized in that: Adjusting the second parameter includes: Obtaining a resonance period of the resonance waveform; The second parameter is adaptively adjusted according to the resonance period, so that the control signal controls the primary power switch tube to be turned on at the target valley bottom.

4. The control method of the switching power supply according to claim 3, characterized in that: Obtaining the resonance period of the resonance waveform, comprising: Obtaining the time between a plurality of continuous troughs or continuous peaks or continuous zero crossings in the resonant waveform; The resonance period is calculated according to the time and the number of the troughs or the peaks or the zero-crossing points.

5. The control method of the switching power supply according to claim 2, characterized in that: Adjusting the second parameter includes: Obtaining the operating parameters of the switching power supply at preset intervals; The second parameter is determined according to the working parameter and a mapping relationship between the preset working parameter and the second parameter.

6. The control method of the switching power supply according to claim 5, characterized in that: After obtaining the operating parameters of the switching power supply at preset time intervals, the method further includes: Determining whether the working parameter changes; If there is a change, the step of determining the second parameter according to the working parameter and the mapping relationship between the preset working parameter and the second parameter is entered.

7. The control method of the switching power supply according to claim 6, characterized in that: Determining whether the working parameter has changed includes: determining whether the level of the working parameter has changed; If the level changes, it is determined that the working parameter has changed.

8. The control method of the switching power supply according to claim 5, characterized in that: The operating parameters include a combination of one or more of the primary input voltage, the secondary output voltage and the load value of the switching power supply.

9. The control method of the switching power supply according to claim 8, characterized in that: When the operating parameters include the primary input voltage and the secondary output voltage of the switching power supply; Obtaining the operating parameters of the switching power supply includes: When the primary power switch tube is turned on, the primary input voltage is calculated according to the voltage of the auxiliary winding, the number of turns of the auxiliary winding and the number of turns of the primary winding; When the secondary switch tube is turned on, the secondary output voltage is calculated according to the voltage of the auxiliary winding, the number of turns of the auxiliary winding and the number of turns of the secondary winding; Wherein, the auxiliary winding and the primary winding share a common ground.

10. The control method of the switching power supply according to claim 8, characterized in that: When the operating parameters include a load value; Obtaining the operating parameters of the switching power supply includes: Obtaining the switching frequency of the primary power switch tube in the switching power supply; determining the load value according to the switching frequency; The load value is positively correlated with the switching frequency.

11. The control method of the switching power supply according to any one of claims 1 to 10, characterized in that: A delay time is superimposed on the resonant periodic signal so that the control signal controls the primary power switch tube of the switching power supply to be turned on within a preset range near the target valley bottom of the resonant waveform according to the resonant periodic signal and the delay signal, including: After determining the target valley bottom according to the load value of the switching power supply, detecting a previous zero-crossing point of a valley bottom previous to the target valley bottom; The moment when the control signal corresponding to the previous zero-crossing point is delayed by the delay time is used as the turn-on moment, so that the control signal controls the primary power switch tube to be turned on at the turn-on moment.

12. A control circuit of a switching power supply, characterized in that: include: A detection unit, used for detecting the resonant periodic signal of the switching power supply in real time; A control unit, configured to superimpose a delay time on the resonant periodic signal, so that the control signal controls the primary power switch tube of the switching power supply to conduct within a preset range near the target valley bottom of the resonant waveform according to the resonant periodic signal and the delay signal; The delay time is related to a first parameter and a second parameter, the first parameter is a set value that varies with time within a certain range, and the second parameter is a function related to the resonance period of the switching power supply.

13. The control circuit of the switching power supply according to claim 12, characterized in that: The control unit comprises: A resonance valley corresponding circuit, used for adjusting the second parameter when the function value of the periodic transformation function related to the first parameter is zero, so that the control signal corresponds to a reference position at the center or left or right of the target valley in the resonance waveform according to the resonance period signal and the delay signal; The frequency jittering circuit is used to superimpose the function value of the periodic variation function of the first parameter on the reference position, so that the control signal controls the primary power switch tube of the switching power supply to be turned on within a preset range of the target valley bottom.

14. A switching power supply, characterized in that: A control circuit comprising a switching power supply as claimed in claim 12 or 13.

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