A control method and circuit of a switching power supply and a switching power supply

Abstract

The application discloses a control method and circuit of a switching power supply and the switching power supply, and relates to the technical field of switching power supplies. In the scheme, a resonance period signal of the switching power supply is detected in real time; a delay time is superimposed on the resonance period signal, so that a control signal controls a primary side power switch tube of the switching power supply to be turned on in a preset range near a target valley bottom of a resonance waveform according to the resonance period signal and the delay signal, wherein the delay time is related to a first parameter and a second parameter, the first parameter is a set value that changes with time in a certain range, and the second parameter is a function related to the resonance period of the switching power supply. It can be seen that the resonance period signal of the switching power supply can be detected in real time, and the primary side power switch tube of the switching power supply can be reliably turned on in a preset range near the target valley bottom according to the resonance period signal and the delay time of the switching power supply, so that the control accuracy is improved.

Description

Technical Field

[0001] This invention relates to the field of switching power supply technology, and in particular to a control method, circuit, and switching power supply for a switching power supply. Background Technology

[0002] In a flyback switching power supply system, after the primary-side power switch is turned 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. At this time, the magnetizing inductance in the transformer and the parasitic capacitance of the primary-side power switch will generate a decaying resonance, which will continue until the primary-side power switch turns on again.

[0003] To reduce the losses of the primary-side power switch, existing technologies typically use a valley-locked QR (quasi-resonant) mode to control its conduction. Specifically, controlling the primary-side power switch to conduct at a specific valley in the resonant waveform (when the primary-side power switch is a MOSFET, its Vds is relatively high) can reduce losses and improve system efficiency. However, if the same valley in the resonant waveform is consistently selected to turn on the primary-side power switch during system operation, the switching frequency will remain constant. This results in poor EMI (Electromagnetic Interference) performance.

[0004] To further improve the system's EMI performance, a negative half-cycle resonant period dithering is superimposed on the QR mode. Specifically, this involves controlling the primary-side power switch to turn on at any moment during the negative half-cycle of a selected valley. For example, if the selected valley is the second valley, the primary-side power switch can be controlled to turn on at any moment to the left of the second valley within the negative half-cycle, or at any moment to the right of the second valley within the negative half-cycle. The specific implementation is as follows: when the zero point before the second valley in the resonant waveform is detected, a preset time is used to control the primary-side power switch to turn on (this preset time is a variable value, but not greater than 1 / 2 of the resonant period, to ensure that the primary-side power switch turns on during the negative half-cycle of the second valley), so that the system's switching frequency is variable, thereby improving the system's EMI performance.

[0005] However, for flyback switching power supply systems with wide input range and multiple voltage outputs, the resonant period is different under different input / output voltages and different load conditions. Therefore, when using the above method to control the primary-side power switch to turn on, it is possible to cause the primary-side power switch to turn on during the positive half-cycle of the resonant waveform. In other words, the existing method cannot make the primary-side power switch turn on precisely at a certain moment of the selected valley in the negative half-cycle, resulting in poor accuracy. Summary of the Invention

[0006] The purpose of this application is to provide a control method, circuit, and switching power supply that can detect the resonant period signal of the switching power supply in real time, and control the primary-side power switch of the switching power supply to reliably conduct within a preset range near the target valley based on the resonant period signal and the delay time, thereby improving the accuracy of control.

[0007] To address the aforementioned technical problems, this application provides a control method for a switching power supply, comprising:

[0008] Real-time detection of the resonant period signal of the switching power supply;

[0009] A delay time is superimposed on the resonant periodic signal so that the control signal controls the primary-side power switch of the switching power supply to turn on within a preset range near the target valley of the resonant waveform according to the resonant periodic signal and the delay signal.

[0010] 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 resonant period of the switching power supply.

[0011] Preferably, the preset range is related to a periodic variation function associated with the first parameter;

[0012] A delay time is superimposed on the resonant periodic signal so that the control signal controls the primary-side power switch of the switching power supply to turn on within a preset range near the target valley of the resonant waveform based on the resonant periodic signal and the delay signal, including:

[0013] When the function value of the periodic transformation function related to the first parameter is zero, the second parameter is adjusted so that the control signal corresponds to the reference position of the target valley center or left or right side in the resonant waveform according to the resonant period signal and the delay signal.

[0014] The function value of the periodic variation function of the first parameter is superimposed at the reference position, so that the control signal controls the primary-side power switch of the switching power supply to conduct within a preset range of the target valley.

[0015] Preferably, adjusting the second parameter includes:

[0016] Obtain the resonant period of the resonant waveform;

[0017] The second parameter is adaptively adjusted according to the resonant period so that the control signal controls the primary-side power switch to turn on at the target valley.

[0018] Preferably, obtaining the resonant period of the resonant waveform includes:

[0019] Obtain the time between several consecutive troughs, peaks, or zero-crossings in the resonant waveform;

[0020] The resonance period is calculated based on the time and the number of troughs, peaks, or zero crossings.

[0021] Preferably, adjusting the second parameter includes:

[0022] The operating parameters of the switching power supply are acquired at preset time intervals.

[0023] The second parameter is determined based on the working parameters and the mapping relationship between the preset working parameters and the second parameter.

[0024] Preferably, after acquiring the operating parameters of the switching power supply at preset time intervals, the method further includes:

[0025] Determine whether the operating parameters have changed;

[0026] If a change occurs, proceed to the step of determining the second parameter based on the working parameters and the mapping relationship between the preset working parameters and the second parameter.

[0027] Preferably, determining whether the operating parameters have changed includes:

[0028] Determine whether the level of the operating parameter has changed;

[0029] If the level changes, it is determined that the operating parameters have changed.

[0030] Preferably, the operating parameters include one or more combinations of the primary-side input voltage, secondary-side output voltage, and load value of the switching power supply.

[0031] Preferably, the operating parameters include the primary-side input voltage and the secondary-side output voltage of the switching power supply;

[0032] Obtaining the operating parameters of the switching power supply includes:

[0033] 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.

[0034] When the secondary-side switch is turned on, the secondary-side 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-side winding.

[0035] The auxiliary winding and the primary winding share a common ground.

[0036] Preferably, the operating parameters include a load value;

[0037] Obtaining the operating parameters of the switching power supply includes:

[0038] Obtain the switching frequency of the primary-side power switch transistor in the switching power supply;

[0039] The load value is determined based on the switching frequency;

[0040] The load value is positively correlated with the switching frequency.

[0041] Preferably, a delay time is superimposed on the resonant periodic signal so that the control signal controls the primary-side power switch of the switching power supply to turn on within a preset range near the target valley of the resonant waveform based on the resonant periodic signal and the delay signal, including:

[0042] After determining the target valley based on the load value of the switching power supply, the zero-crossing point of the previous valley is detected.

[0043] The control signal corresponding to the previous zero crossing point is delayed by the delay time as the turn-on time, so that the control signal controls the primary-side power switch to turn on at the turn-on time.

[0044] To address the aforementioned technical problems, this application also provides a control circuit for a switching power supply, comprising:

[0045] A detection unit is used to detect the resonant period signal of the switching power supply in real time;

[0046] A control unit is configured to superimpose a delay time onto the resonant periodic signal, so that the control signal controls the primary-side power switch of the switching power supply to be turned on within a preset range near the target valley of the resonant waveform according to the resonant periodic signal and the delay signal.

[0047] 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 resonant period of the switching power supply.

[0048] Preferably, the control unit includes:

[0049] The resonant valley bottom corresponding circuit is used to adjust the second parameter when the function value of the periodic transformation function related to the first parameter is zero, so as to correspond the control signal with the reference position of the center, left or right of the target valley bottom in the resonant waveform according to the resonant period signal and the delay signal;

[0050] The frequency dithering circuit is used to superimpose the function value of the periodic variation function of the first parameter at the reference position, so that the control signal controls the primary-side power switch of the switching power supply to conduct within a preset range of the target valley.

[0051] To address the aforementioned technical problems, this application also provides a switching power supply, including the control circuit of the switching power supply described above.

[0052] This application provides a control method for a switching power supply, relating to the field of switching power supply technology. In this scheme, the resonant period signal of the switching power supply is detected in real time; a delay time is superimposed on the resonant period signal, so that the control signal controls the primary-side power switch of the switching power supply to conduct within a preset range near the target valley of the resonant waveform according to the resonant period signal and the delay signal. The delay time is related to a first parameter and a second parameter, where 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 resonant period of the switching power supply. Therefore, this application can detect the resonant period signal of the switching power supply in real time and reliably control the primary-side power switch of the switching power supply to conduct within a preset range near the target valley based on the resonant period signal and the delay time, thus improving the accuracy of control.

[0053] This application also provides a control circuit and a switching power supply, which have the same beneficial effects as the control method of the switching power supply described above. Attached Figure Description

[0054] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the prior art and embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0055] Figure 1a This is a schematic diagram of the first waveform in the prior art;

[0056] Figure 1b This is a schematic diagram of the second waveform in the prior art;

[0057] Figure 2A flowchart illustrating a control method for a switching power supply provided in this application;

[0058] Figure 3 A partial structural schematic diagram of a switching power supply provided in this application;

[0059] Figure 4 A waveform diagram provided for this application;

[0060] Figure 5 A control principle diagram of a switching power supply is provided in this application;

[0061] Figure 6a A schematic diagram of the working waveform of a switching power supply provided in this application;

[0062] Figure 6b A schematic diagram of a method for generating a resonant periodic signal provided in this application;

[0063] Figure 6c A schematic diagram of a control signal provided in this application;

[0064] Figure 6d A waveform diagram of the periodic function related to the first parameter provided in this application;

[0065] Figure 6e A waveform diagram showing the first type of primary-side power switch provided in this application conducting on the left side of the target valley bottom;

[0066] Figure 6f A waveform diagram showing the first type of primary-side power switch provided in this application conducting at the target valley.

[0067] Figure 6g A waveform diagram showing the first type of primary-side power switch provided in this application conducting on the right side of the target valley bottom;

[0068] Figure 7a A schematic diagram of another operating waveform of the switching power supply provided in this application;

[0069] Figure 7b A schematic diagram of another control signal is provided for this application;

[0070] Figure 7c A schematic diagram of a function related to the second parameter provided in this application;

[0071] Figure 7d A waveform diagram showing the second type of primary-side power switch provided in this application conducting on the left side of the target valley bottom;

[0072] Figure 7e A waveform diagram showing the second type of primary-side power switch provided in this application conducting at the target valley.

[0073] Figure 7f A waveform diagram showing the second type of primary-side power switch provided in this application conducting on the right side of the target valley;

[0074] Figure 8 This application provides a structural block diagram of a control circuit for a switching power supply. Detailed Implementation

[0075] The core of this application is to provide a control method, circuit, and switching power supply for a switching power supply, which can detect the resonant period signal of the switching power supply in real time, and control the primary-side power switch of the switching power supply to reliably conduct within a preset range near the target valley based on the resonant period signal and the delay time, thereby improving the accuracy of control.

[0076] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0077] Please refer to Figure 1a and 1b , Figure 1a This is a schematic diagram of the first waveform in the prior art. Figure 1b This is a schematic diagram of the second waveform in the prior art. Figure 1a and Figure 1b In the diagram, the left side represents the on-time of the primary-side power switch, the higher middle portion represents the on-time of the secondary-side switch, and the decaying sine wave on the right is the resonant waveform generated after the secondary-side switch is turned off. Figure 1a and Figure 1b Both methods control the primary-side power switch to conduct during the negative half-cycle of the third valley. However, the experimental results using the existing control method are as follows: Figure 1a The power switch on the central side is turned on during the negative half-cycle, slightly to the left of the third valley. Figure 1b The power switch in the middle of the circuit turns on near or even at the second peak to the left of the third trough, which does not meet the requirement of turning on during the negative half-cycle.

[0078] Please refer to Figure 2 , Figure 2 This application provides a flowchart illustrating a control method for a switching power supply, the method comprising:

[0079] S11: Real-time detection of the resonant period signal of the switching power supply;

[0080] Specifically, the resonant periodic signal here represents the resonant signal of the switching power supply. Specifically, it can represent the zero-crossing point of the resonant waveform (e.g., when the resonant waveform is in the positive half-cycle, the resonant periodic signal is at a high level, and when the resonant waveform is in the negative half-cycle, the resonant periodic signal is at a low level). For details, please refer to Tdem in the first and second embodiments below.

[0081] S12: A delay time is superimposed on the resonant period 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 of the resonant waveform according to the resonant period signal and the delay signal.

[0082] The delay time is related to the first parameter and the 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 resonant period of the switching power supply.

[0083] After detecting the resonant period signal as described above, a delay time is superimposed after one of the resonant periods, so that the control signal generated at the resonant period signal controls the primary power switch to conduct within a preset range near the target valley of the resonant waveform after the delay time.

[0084] Specifically, to improve the EMI performance of the system, the primary-side power switch in this application is turned on at different positions in the negative half-cycle of the target valley in two adjacent cycles. The target valley is within a preset range that does not exceed the negative half-cycle of the target valley. In other words, turning on within the preset range of the target valley means controlling the primary-side switch to oscillate and turn on within this preset range in different cycles, with each two adjacent turns being at different positions.

[0085] Since the aforementioned delay time is related to the first parameter and the second parameter, and the first parameter is a setting that changes with time, while the second parameter is a function related to the resonant period, the control method in this application can determine the delay time based on the resonant period to determine the conduction time of the primary-side power switch, thereby improving the reliability of the primary-side power switch conduction.

[0086] As a preferred embodiment, the preset range is related to a periodic variation function associated with the first parameter;

[0087] A delay time is superimposed on the resonant periodic signal so that the control signal controls the primary-side power switch of the switching power supply to turn on within a preset range near the target valley of the resonant waveform, based on the resonant periodic signal and the delay signal. This includes:

[0088] When the function value of the periodic transformation function related to the first parameter is zero, the second parameter is adjusted so that the control signal corresponds to the reference position of the target valley center or left or right side in the resonant waveform according to the resonant period signal and the delayed signal.

[0089] The function value of the periodic variation function of the first parameter is superimposed at the reference position, so that the control signal controls the primary power switch of the switching power supply to conduct within the preset range of the target valley.

[0090] Specifically, when the periodic variation function corresponding to the first parameter is related to a preset range, it can specifically be when the periodic variation function is a frequency dithering amount in the delay time (in a specific embodiment, the first parameter is...). Figure 6d In this context, m is a periodic variation function related to the first parameter. Figure 6d In Ij(m)), the first parameter is used to ensure that the primary power switch is turned on in the range near the target valley bottom, so that it is not fixed at a single position at the target valley bottom.

[0091] At this point, if the function value of the periodic function corresponding to the first parameter is zero (that is, Figure 6d When the corresponding Ij(m) is zero, then m can be 1 or 2*2. x-2 or 2 x The value of '(')' indicates that the frequency dithering added during the delay time is zero. This means that the primary-side power switch should be accurately turned on at the target valley or at any reference position to the left or right of the target valley. Therefore, if the primary-side power switch is not accurately turned on at the reference position, it indicates that the second parameter is inaccurate. Therefore, the second parameter is adjusted when the function value of the periodic variation function corresponding to the first parameter is zero, to ensure that after the frequency dithering is added, the primary-side power switch can accurately turn on at any moment within a preset range near the target valley.

[0092] After aligning the control signal with a reference position near the target valley bottom, a periodically varying function related to the first parameter is then superimposed on the reference position. This causes the control signal to move periodically near the reference position. Consequently, when the primary-side power switch is turned on based on this control signal, the primary-side switch oscillates and turns on near the reference position. In a specific embodiment, the reference position is the center of the target valley bottom.

[0093] In a preferred embodiment, adjusting the second parameter includes:

[0094] Obtain the resonant period of the resonant waveform;

[0095] The second parameter is adaptively adjusted according to the resonant period so that the control signal controls the primary-side power switch to turn on at the target valley.

[0096] Specifically, since the second parameter is a function related to the resonance period (specifically, as shown in the following embodiment, the second parameter is k), one way to adjust the second parameter in this application is to adaptively adjust the second parameter according to the resonance waveform. The purpose is to ensure that when the function value of the periodic change function corresponding to the first parameter is zero, the control signal can be accurately turned on at the reference position at the center, left or right of the target valley.

[0097] As a preferred embodiment, obtaining the resonant period of the resonant waveform includes:

[0098] To obtain the time between several consecutive troughs, peaks, or zero crossings in a resonant waveform;

[0099] The resonant period is calculated based on the time and the number of troughs, peaks, or zero crossings.

[0100] This embodiment aims to provide a specific method for obtaining the resonance period. Specifically, the resonance period can be calculated based on the time between several consecutive peaks in the resonance waveform, or the time between several consecutive troughs, or the time between several consecutive zero crossings, as well as the corresponding number of peaks, troughs, or zero crossings.

[0101] For example, if the time for N consecutive zero-crossings is t1, then the resonance period T = 2t1 / N (each period has two zero-crossings, 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 time for n consecutive troughs is t2, then the resonance period T = t2 / n. The calculation method for peaks is the same as for troughs, and will not be repeated here.

[0102] To ensure the accuracy and reliability of the switching power supply control, this application detects the resonant period of the switching power supply at regular intervals to update the resonant period of the switching power supply in order to adjust the second parameter according to the latest detected resonant period.

[0103] In a preferred embodiment, adjusting the second parameter includes:

[0104] The operating parameters of the switching power supply are acquired at preset intervals.

[0105] The second parameter is determined based on the working parameters and the mapping relationship between the preset working parameters and the second parameter.

[0106] This embodiment aims to provide another way to adjust the second parameter. Specifically, this application has a preset mapping relationship between preset operating parameters and the second parameter. After determining the operating parameters of the switching power supply, the second parameter corresponding to the operating parameters can be determined by looking up the preset operating parameter-delay time mapping relationship based on the operating parameters of the switching power supply. Then, the delay time is adjusted according to this second parameter so that when the function value of the periodic change function corresponding to the first parameter is zero, the control signal controls the primary-side power switch to reliably conduct at the target valley.

[0107] In a preferred embodiment, after acquiring the operating parameters of the switching power supply at preset time intervals, the method further includes:

[0108] Determine if the operating parameters have changed;

[0109] If a change occurs, proceed to the step of determining the second parameter based on the working parameters and the mapping relationship between the preset working parameters and the second parameter.

[0110] Specifically, in this embodiment, the change in the second parameter is usually caused by a change in the operating parameters of the power supply of the switch. Therefore, this application also detects the operating parameters of the switching power supply, and when they change, proceeds to the step of determining the second parameter. When the time interval between two consecutive detections of the operating parameter is sufficiently short, it is equivalent to real-time monitoring of the operating parameters of the switching power supply.

[0111] As a preferred embodiment, determining whether the operating parameters have changed includes:

[0112] Determine whether the level of the working parameters has changed;

[0113] If the level changes, it is determined that the working parameters have changed.

[0114] Specifically, to prevent the determination of the second parameter from being triggered when the change in the working parameters is extremely small, the second parameter needs to be determined frequently, which results in a large power consumption of the processor.

[0115] Therefore, in this application, the operating parameters are divided into different levels. The specific implementation of determining whether the operating parameters have changed is as follows: determine whether the level of the operating parameter has changed, and if it has changed, determine that the operating parameter has changed. Only then is the step of determining the second parameter triggered, thus avoiding the frequent triggering of the step of determining the second parameter, which can reduce the power consumption of the processor to a certain extent.

[0116] As a preferred embodiment, the operating parameters include one or more combinations of the primary-side input voltage, secondary-side output voltage, and load value of the switching power supply.

[0117] This embodiment aims to define the specific implementation method of the operating parameters. Specifically, the operating parameters may be, but are not limited to, the primary side input voltage, secondary side output voltage, and load value of the switching power supply.

[0118] The primary input voltage range may be, but is not limited to, 90Vac to 265Vac, and the output voltage range may be, but is not limited to, 3.3V to 21V. When classifying the operating parameters as described above, the range of primary input voltage, secondary output voltage and load value may be divided into several levels according to actual needs. This application does not make any special restrictions on how to classify them.

[0119] In one preferred embodiment, the operating parameters include the primary-side input voltage and the secondary-side output voltage of the switching power supply;

[0120] Obtain the operating parameters of the switching power supply, including:

[0121] 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.

[0122] 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.

[0123] The auxiliary winding shares a common ground with the primary winding.

[0124] This embodiment aims to define the specific implementation method for calculating the primary-side input voltage and the secondary-side output voltage. Specifically, the primary-side input voltage can be calculated by taking 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-side power switch is turned on. For details, please refer to... Figure 3 , Figure 3 This application provides a partial structural schematic diagram of a switching power supply. The primary input voltage is detected by sensing the current flowing through the pull-up resistor R at the auxiliary winding terminal. DEM The derivation is as follows: Where Vin is the primary input voltage, and I DEMAG R is the current across the pull-up resistor. DEM For the pull-up resistor connected to the auxiliary winding, Np is the number of turns in the primary winding, and Na is the number of turns in the auxiliary winding.

[0125] The specific method for calculating the secondary-side output voltage is to calculate it 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 when the secondary-side switch is turned on. For details, please refer to... Figure 4 , Figure 4A waveform diagram is provided for this application. The secondary output voltage is determined by detecting V during the Tons and Toff periods. DEM The voltage is used to determine this. Here, Tons represents the time period during which the secondary-side switch is on, and Toff represents the time period during which the secondary-side switch is off but the primary-side power switch has not yet turned on in the next cycle (i.e., the period of resonance). Figure 4 In this context, Gate\Tonp represents the time period during which the primary-side power switch is on. Where 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 in the auxiliary winding, and Ns is the number of turns in the secondary winding.

[0126] In a preferred embodiment, the operating parameters include the load value;

[0127] Obtain the operating parameters of the switching power supply, including:

[0128] Obtain the switching frequency of the primary-side power switching transistor in the switching power supply;

[0129] Determine the load value based on the switching frequency;

[0130] Among them, the load value is positively correlated with the switching frequency.

[0131] This embodiment aims to define a specific implementation method for determining the load value. Specifically, the load value of the current switching power supply is determined based on the switching frequency of the primary-side power switch. The switching frequency of the primary-side power switch is positively correlated with the load value. Specifically, the switching period of the primary-side power switch is the sum of the primary-side power switch's on-time, the secondary-side power switch's on-time, and the resonant time (specifically, the time interval from the start of resonance until the primary-side power switch turns on at the determined target valley). Currently, when the switching power supply is lightly loaded, a valley further back in the resonant waveform is selected, resulting in a longer switching period and a lower switching frequency. When the switching power supply is heavily loaded, a valley further forward in the resonant waveform is selected, resulting in a shorter switching period and a higher switching frequency. Therefore, to determine the load value of the switching power supply, it is only necessary to determine it based on the current switching frequency of the primary-side power switch.

[0132] Of course, the above is only one implementation method provided in this embodiment. It is also possible to directly detect the load value through a detection device, etc. This application will not limit it here.

[0133] In a preferred embodiment, a delay time is superimposed on the resonant periodic signal so that the control signal controls the primary-side power switch of the switching power supply to turn on within a preset range near the target valley of the resonant waveform, based on the resonant periodic signal and the delay signal. This includes:

[0134] After determining the target valley based on the load value of the switching power supply, detect the zero-crossing point of the previous valley before the target valley.

[0135] The control signal delay time corresponding to the previous zero crossing point is taken as the turn-on time, so that the control signal controls the primary power switch to turn on at the turn-on time.

[0136] Specifically, determining the turn-on time in this application involves several steps. First, the zero-crossing point of the resonant waveform is detected to determine the location of the target valley. The specific method for determining the turn-on time is as follows: a valley preceding the target valley is identified, and then the zero-crossing point preceding that valley is detected. The turn-on time is determined by delaying the zero-crossing point by a specified time. This turn-on time can be any time near the target valley. Using the method described in this application, the target valley can be accurately determined, and the conduction frequency of the primary-side power switch in the switching power supply can be continuously adjusted to avoid the primary-side power switch frequency remaining constant, thus improving the EMI performance of the switching power supply.

[0137] The design objective of this application is to control the primary-side power switch to conduct during the negative half-cycle at the target valley. To this end, this application provides two embodiments. The first embodiment is described in [reference needed]. Figure 5 , Figures 6a-6g , Figure 5 This application provides a control principle diagram of a switching power supply. Figure 6a This application provides a schematic diagram of the operating waveform of a switching power supply. Figure 6b This application provides a schematic diagram of a method for generating a resonant periodic signal. Figure 6c A schematic diagram of a control signal provided in this application. Figure 6d A waveform diagram of the periodic function related to the first parameter provided in this application. The first embodiment is described as follows:

[0138] in, Figure 6a Tdem in Figure 6b The result of comparing DEMAG with 0V is that Tdem is the signal characterizing the zero-crossing point of the resonant waveform. In this embodiment, Tdem is used as the resonant period signal described above. Figure 6a Vds in the figure represents the resonant waveform on the primary power switch.

[0139] Figure 6c In this context, the input CLK to the x-bits jitter counter can be an oscillator output or an SW signal. The x-bits jitter counter counts CLK and outputs the count result m, where m ranges from 1 to 2. x The x-bitsjitter counter can count cyclically, m=2.x When the next CLK occurs, m = 1 (m is the first parameter described above). Figure 6c The implementation of D to I in China can be as follows: Figure 6d As shown, 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 periodic function related to the first parameter mentioned above).

[0140] Valley Lockout modules are configured according to the load of the switching power supply (specific location). Figure 5 The COMP voltage in the middle selects the nth valley to conduct; (that is, valley lockout is determined by the load).

[0141] The Current Table module detects the primary-side input voltage and secondary-side output voltage using DEMAG; and selects a preset output current It(k) based on the primary-side input voltage, secondary-side output voltage, and target Valley(n), such that m = 1 or m = 2*2. x-2 At this time, Tpulse (control signal) corresponds to the valley. If the primary input voltage, secondary output voltage, and system load remain unchanged, then k (second parameter) remains unchanged.

[0142] In the (n-1)th Tdem n-1 After the rising edge, after a delay t d (m,k), generating the nth Tpulse n (Tpulse n =Tdem n-1 +t d (m,k)). Where t d The specific implementation of (m,k) can be: t d (m,k)=C*Vref / [Ij(m)+It(k)].

[0143] In the nth Tpulse n At the rising edge, the primary power switch is turned on.

[0144] If m = 1 or m = 2*2 x-2 At that time, Tpulse n The primary power switch is turned on at the reference position corresponding to the negative half-cycle of the target valley. The specific reference position can be the target valley. With Ij(m) changing periodically, the primary power switch can be turned on in the negative half-cycle region.

[0145] Figure 6e This is a waveform diagram showing the first type of primary-side power switch provided in this application conducting on the left side of the target valley. At this time, m = 2.x-2 Ij(m) is a positive value, and Tpulse is to the left of the reference position (target valley bottom).

[0146] Figure 6f This is a waveform diagram illustrating the first type of primary-side power switch provided in this application conducting at the target valley. At this time, m = 1 or 2*2. x-2 When Ij(m) is zero, Tpulse is at the reference position (target valley).

[0147] Figure 6g This is a waveform diagram showing the first type of primary-side power switch provided in this application conducting on the right side of the target valley. At this time, m = 3 * 2 x-2 Ij(m) is negative, and Tpulse is to the right of the reference position (target valley bottom).

[0148] Please refer to the second embodiment. Figures 7a-7f , Figure 7a This is a schematic diagram of another operating waveform of the switching power supply provided in this application. Figure 7b A schematic diagram of another control signal is provided for this application. Figure 7c A schematic diagram of a function related to the second parameter provided in this application is shown below, and the second embodiment is described as follows:

[0149] This embodiment uses the DLL (Delay-Locked Loop) principle, compared to Tpulse. n The timing relationship between the rising edge and the reference signal is dynamically adjusted to td(m,k) so that when m is a certain constant (the function value of the function corresponding to m is zero), Tpulse... n Corresponding to the bottom of the valley.

[0150] Sample Tdem and generate Tmid (Tdem falling edge + 0.75 * tdem) based on Tdem, such as... Figure 7a As shown, the falling edge of Tmid corresponds to the valley of the resonant waveform.

[0151] In m=1 or m=2*2 x-2 At that time, compare the positional relationship between the rising edge of Tpulse and the falling edge of Tmid, and adjust k every SW cycle, with k ranging from 1 to 2. y (y is the value of the counter).

[0152] If the falling edge of Tmid leads the rising edge of Tpulse, k n =k n-1 +1;

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

[0154] In m≠1 and m≠2*2 x-2 When, k n =k n-1 .

[0155] Figure 7b The D to I module in, such as Figure 7c As shown, k is converted into the output current It(k). The range of It(k) is Iini~Iini+(2 y -1)*Itune.

[0156] Finally, after several cycles of dynamic adjustment of td(m,k), at m=1 or m=2*2 x-2 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 will dynamically follow the change of the resonance period as the operating conditions change.

[0157] 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 is turned on at the reference position corresponding to the negative half-cycle of the target valley. The specific reference position can be the target valley, and Ij(m) changes periodically, so that the primary power switch can be turned on in the negative half-cycle region of the target valley.

[0158] Figure 7d This is a waveform diagram showing the second type of primary-side power switch provided in this application conducting on the left side of the target valley. At this time, m = 2. x-2 Ij(m) is a positive value, and Tpulse is to the left of the reference position (target valley bottom).

[0159] Figure 7e This is a waveform diagram illustrating the second type of primary-side power switch provided in this application conducting at the target valley. At this time, m = 1 or 2*2. x-2 When Ij(m) is zero, Tpulse is at the reference position (target valley).

[0160] Figure 7f This is a waveform diagram showing the second type of primary-side power switch provided in this application conducting on the right side of the target valley. At this time, m = 3 * 2 x-2 Ij(m) is negative, and Tpulse is to the right of the reference position (target valley bottom).

[0161] To address the aforementioned technical problems, this application also provides a control circuit for a switching power supply, please refer to... Figure 8 , Figure 8 A block diagram of a control circuit for a switching power supply provided in this application is shown. The circuit includes:

[0162] The detection unit 81 is used to detect the resonant period signal of the switching power supply in real time.

[0163] Control unit 82 is used 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 the target valley of the resonant waveform according to the resonant periodic signal and the delay signal.

[0164] The delay time is related to the first parameter and the 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 resonant period of the switching power supply.

[0165] In a preferred embodiment, the control unit includes:

[0166] The resonant valley correspondence circuit is used to adjust 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 the reference position of the center, left or right of the target valley in the resonant waveform according to the resonant period signal and the delay signal.

[0167] The frequency dithering circuit is used to superimpose the function value of the periodic variation function of the first parameter at the reference position, so that the control signal controls the primary power switch of the switching power supply to conduct within a preset range of the target valley.

[0168] For a description of the control circuit of the switching power supply, please refer to the above embodiments; this application will not repeat it here.

[0169] To address the aforementioned technical problems, this application also provides a switching power supply, including the control circuit of the aforementioned switching power supply. For a description of the switching power supply, please refer to the above embodiments; further details will not be repeated here.

[0170] It should also be noted that, in this specification, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0171] The above description of the disclosed embodiments enables those skilled in the art to make or use this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A control method for a switching power supply, characterized in that, include: Real-time detection of the resonant period signal of the switching power supply; A delay time is superimposed on the resonant periodic signal so that the control signal controls the primary-side power switch of the switching power supply to turn on within a preset range near the target valley of the resonant waveform according to the resonant periodic signal and the delay time. 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 resonant period of the switching power supply. The preset range is defined by superimposing the function value of a periodic change function related to the first parameter on the reference position, so that the control signal moves periodically near the reference position, thereby controlling the primary-side power switch to oscillate and conduct near the target valley. The first parameter is a count value m generated by a counter and cyclically changing within a certain range. The periodic change function Ij(m) associated with the first parameter is configured such that: when m takes a first specific value, Ij(m) = 0, so that the control signal is aligned with the center reference position of the target valley bottom; when m takes other values, Ij(m) is positive or negative, so that the control signal moves to the left or right of the center reference position.

2. The control method for a switching power supply as described in claim 1, characterized in that, The preset range is related to the periodic change function associated with the first parameter; A delay time is superimposed on the resonant periodic signal so that the control signal controls the primary-side power switch of the switching power supply to turn on within a preset range near the target valley of the resonant waveform based on the resonant periodic signal and the delay time, including: When the function value of the periodic change function related to the first parameter is zero, the second parameter is adjusted so that the control signal corresponds to the reference position of the target valley center or left or right side in the resonant waveform according to the resonant period signal and the delay time. The function value of the periodic variation function of the first parameter is superimposed at the reference position, so that the control signal controls the primary power switch of the switching power supply to conduct within a preset range of the target valley.

3. The control method for a switching power supply as described in claim 2, characterized in that, Adjusting the second parameter includes: Obtain the resonant period of the resonant waveform; The second parameter is adaptively adjusted according to the resonant period so that the control signal controls the primary-side power switch to turn on at the target valley.

4. The control method for a switching power supply as described in claim 3, characterized in that, Obtaining the resonant period of the resonant waveform includes: Obtain the time between several consecutive troughs, peaks, or zero-crossings in the resonant waveform; The resonance period is calculated based on the time and the number of troughs, peaks, or zero crossings.

5. The control method for a switching power supply as described in claim 2, characterized in that, Adjusting the second parameter includes: The operating parameters of the switching power supply are acquired at preset time intervals. The second parameter is determined based on the working parameters and the mapping relationship between the preset working parameters and the second parameter.

6. The control method for a switching power supply as described in claim 5, characterized in that, After acquiring the operating parameters of the switching power supply at preset time intervals, the method further includes: Determine whether the operating parameters have changed; If a change occurs, proceed to the step of determining the second parameter based on the working parameters and the mapping relationship between the preset working parameters and the second parameter.

7. The control method for a switching power supply as described in claim 6, characterized in that, Determining whether the operating parameters have changed includes: Determine whether the level of the operating parameter has changed; If the level changes, it is determined that the operating parameters have changed.

8. The control method for a switching power supply as described in claim 5, characterized in that, The operating parameters include one or more combinations of the primary input voltage, secondary output voltage, and load value of the switching power supply.

9. The control method for a switching power supply as described in claim 8, characterized in that, The operating parameters include the primary input voltage and secondary output voltage of the switching power supply; Obtaining the operating parameters of the switching power supply includes: 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. When the secondary-side switch is turned on, the secondary-side 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-side winding. The auxiliary winding and the primary winding share a common ground.

10. The control method for a switching power supply as described in claim 8, characterized in that, When the operating parameters include the load value; Obtaining the operating parameters of the switching power supply includes: Obtain the switching frequency of the primary-side power switch transistor in the switching power supply; The load value is determined based on the switching frequency; The load value is positively correlated with the switching frequency.

11. The control method for a switching power supply as described in any one of claims 1-10, characterized in that, A delay time is superimposed on the resonant periodic signal so that the control signal controls the primary-side power switch of the switching power supply to turn on within a preset range near the target valley of the resonant waveform based on the resonant periodic signal and the delay time, including: After determining the target valley based on the load value of the switching power supply, the zero-crossing point of the previous valley is detected. The control signal corresponding to the previous zero crossing point is delayed by the delay time as the turn-on time, so that the control signal controls the primary-side power switch to turn on at the turn-on time.

12. A control circuit for a switching power supply, characterized in that, include: A detection unit is used to detect the resonant period signal of the switching power supply in real time; A control unit is configured to superimpose a delay time onto the resonant periodic signal, so that the control signal controls the primary-side power switch of the switching power supply to be turned on within a preset range near the target valley of the resonant waveform according to the resonant periodic signal and the delay time. 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 resonant period of the switching power supply. The preset range is defined by superimposing the function value of a periodic change function related to the first parameter on the reference position, so that the control signal moves periodically near the reference position, thereby controlling the primary-side power switch to oscillate and conduct near the target valley. The first parameter is a count value m generated by a counter and cyclically changing within a certain range. The periodic change function Ij(m) associated with the first parameter is configured such that: when m takes a first specific value, Ij(m) = 0, so that the control signal is aligned with the center reference position of the target valley bottom; when m takes other values, Ij(m) is positive or negative, so that the control signal moves to the left or right of the center reference position.

13. The control circuit of the switching power supply as described in claim 12, characterized in that, The control unit includes: The resonant valley bottom corresponding circuit is used to adjust the second parameter when the function value of the periodic change function related to the first parameter is zero, so as to correspond the control signal with the reference position of the center, left or right of the target valley bottom in the resonant waveform according to the resonant period signal and the delay time. The frequency dithering circuit is used to superimpose the function value of the periodic variation function of the first parameter at the reference position, so that the control signal controls the primary-side power switch of the switching power supply to conduct within a preset range of the target valley.

14. A switching power supply, characterized in that, Includes the control circuit of the switching power supply as described in claim 12 or 13.

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