Switching power supply control method, circuit, and switching power supply

Abstract

The present invention relates to a control method, a circuit, and a switching power supply, which relate to the technical field of switching power supplies. In this method, a resonant periodic signal of a switching power supply is detected in real time, and a delay time is superimposed on the resonant periodic signal, so that a control signal controls the conduction of a primary side power switching transistor of the switching power supply within a predetermined range around a target valley of a resonant waveform based on the resonant periodic signal and the delay signal, in which 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. In this application, the resonant periodic signal of the switching power supply can be detected in real time, and the primary side power switching transistor of the switching power supply is reliably conducted within a predetermined range around a target valley based on the resonant periodic signal and the delay time of the switching power supply, thereby improving the accuracy of control.

Description

[Technical Field]

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

[0002] In a flyback switching power supply system, when the primary-side power switching transistor is turned off, the secondary diode conducts and the energy stored in the transformer starts to transfer to the secondary side. When the energy transfer ends, the secondary diode turns off, and at this time, damped resonance occurs between the exciting inductance in the transformer and the parasitic capacitance of the primary-side power switching transistor, and this resonance is maintained until the next primary-side power switching transistor is turned on.

[0003] To reduce the wear of the primary-side power switching transistor, existing technologies typically use the quasi-resonant (QR) mode of valley lockout to control the conduction of the primary-side power switching transistor. Specifically, controlling the conduction of one of the valley portions of the resonant waveform of the primary-side power switching transistor (if the primary-side power switching transistor is a MOS transistor, the Vds of the MOS (metal-oxide-semiconductor field-effect transistor) is quite large) can reduce the wear of the primary-side power switching transistor and improve system efficiency. However, if the same valley in the resonant waveform is selected every time during system operation to turn on the primary-side power switching transistor, the system's switching frequency will remain constant, which will result in poor EMI (electromagnetic interference) performance.

[0004] To further improve the system's EMI performance, a jitter frequency of the negative half-cycle of the resonant period is superimposed in QR mode. Specifically, the primary-side power switching transistor is controlled to conduct at any time during the negative half-cycle where the selected valley is located. For example, if the selected valley is the second valley, the primary-side power switching transistor can be controlled to conduct at any time on the left side of the second valley within the negative half-cycle, or at any time on the right side of the second valley within the negative half-cycle. Specifically, when the zero point before the second valley in the resonant waveform is detected, the primary-side power switching transistor is controlled to conduct with a predetermined delay (this predetermined time is a variable value that does not exceed half the resonant period, ensuring that the primary-side power switching transistor conducts within the negative half-cycle where the second valley is located), thereby changing the system's switching frequency and improving the system's EMI performance.

[0005] However, in a flyback switching power supply system with a wide input range and multi-stage voltage output, the corresponding resonant period is different under different input / output voltage and load conditions. Therefore, when the above method is used to control the primary side power switching transistor, the primary side power switching transistor may be turned on during the positive half period of the resonant waveform. In other words, the method of the existing technology cannot accurately turn on the primary side power switching transistor at any time during the negative half period of the selected valley, 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 for a switching power supply, which can detect the resonant periodic signal of the switching power supply in real time, and control the primary side power switching transistor of the switching power supply to reliably conduct within a predetermined range around the target valley based on the resonant periodic signal and delay time of the switching power supply, thereby improving the accuracy of control.

[0007] In order to solve the above technical problems, the present application provides a control method for a switching power supply, detecting a resonant periodic signal of the switching power supply in real time; and superimposing a delay time on the resonant periodic signal to cause a control signal to control conduction of a primary side power switching transistor of the switching power supply within a predetermined range around a target valley of a resonant waveform based on the resonant periodic signal and the delay signal, The delay time is related to a first parameter and a second parameter, the first parameter being a set value that varies over time within a certain range, and the second parameter being a function related to the resonant period of the switching power supply.

[0008] Preferably, the predetermined range is related to a periodically varying function related to the first parameter; By superimposing a delay time on the resonant periodic signal, the control signal controls the conduction of the primary side power switching transistor of the switching power supply within a predetermined range around a target valley of a resonant waveform based on the resonant periodic signal and the delay signal, When a function value of a periodic transformation function associated with the first parameter is zero, adjusting the second parameter to cause the control signal to correspond to a reference position of the center or a left or right side of a target valley in the resonant waveform based on the resonant periodic signal and the delay signal; and superimposing a function value of a periodically varying function of the first parameter on the reference position to cause the control signal to control the conduction of a primary side power switching transistor of the switching power supply within a predetermined range of the target valley.

[0009] Preferably, adjusting the second parameter comprises: obtaining a resonance period of the resonance waveform; and self-adaptively adjusting a second parameter based on the resonant period to cause the control signal to control conduction of the primary-side power switching transistor at the target valley.

[0010] Preferably, obtaining the resonance period of the resonance waveform includes: obtaining the sum of the time between a number of consecutive valleys or peaks or zero crossings in the resonant waveform; Calculating the resonant period based on the sum of the times and the number of the valleys, peaks, or zero-crossing points.

[0011] Preferably, adjusting the second parameter comprises: acquiring operating parameters of the switching power supply at predetermined time intervals; determining the second parameter based on the operating parameter and a mapping relationship between the preset operating parameter and the second parameter.

[0012] Preferably, after acquiring the operating parameters of the switching power supply at predetermined time intervals, determining whether a change has occurred in the operating parameter; If a change occurs, proceed to determine the second parameter based on the operating parameter and a preset operating parameter-second parameter mapping relationship.

[0013] Preferably, determining whether a change in the operating parameter has occurred comprises: determining whether a change has occurred in the level of the operating parameter; If a change has occurred in the level, determining that a change has occurred in the operating parameter.

[0014] Preferably, the operating parameters include one or a combination of several of a primary side input voltage, a secondary side output voltage, and a load value of the switching power supply.

[0015] Preferably, when the operating parameters include a primary side input voltage and a secondary side output voltage of the switching power supply, Obtaining the operating parameters of the switching power supply calculating the primary side input voltage based on a voltage of an auxiliary winding, a number of turns of the auxiliary winding, and a number of turns of a primary side winding when the primary side power switching transistor is conductive; calculating the secondary-side output voltage 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 when the secondary-side switching transistor is conductive; Wherein, the auxiliary winding and the primary winding have a common base.

[0016] Preferably, when the operating parameters include a load value, Obtaining the operating parameters of the switching power supply obtaining a switching frequency of the primary side power switching transistor in the switching power supply; determining the load value based on the switching frequency; Wherein, the load value is positively correlated with the switching frequency.

[0017] Preferably, by superimposing a delay time on the resonant periodic signal, the control signal controls the conduction of the primary side power switching transistor of the switching power supply within a predetermined range around a target valley of a resonant waveform based on the resonant periodic signal and the delay signal, determining the target valley based on a load value of the switching power supply, and then detecting a zero crossing point immediately before the valley immediately before the target valley; The time when the control signal corresponding to the immediately preceding zero crossing point is delayed by the delay time is set as a conduction time, and the control signal is made to control the conduction of the primary side power switching transistor at the conduction time.

[0018] In order to solve the above technical problems, the present application provides a control circuit for a switching power supply, a detection unit for detecting a resonant periodic signal of the switching power supply in real time; a control unit for controlling the conduction of a primary side power switching transistor of the switching power supply within a predetermined range around a target valley of a resonant waveform based on the resonant periodic signal and the delay signal by superimposing a delay time on the resonant periodic signal, The delay time is related to a first parameter and a second parameter, the first parameter being a set value that varies over time within a certain range, and the second parameter being a function related to the resonant period of the switching power supply.

[0019] Preferably, the control unit a resonant valley correspondence circuit for adjusting the second parameter when a function value of a periodic transformation function associated with the first parameter is zero, to cause the control signal to correspond to a reference position of the center or a left or right side of a target valley in the resonant waveform based on the resonant periodic signal and the delay signal; and a jitter frequency circuit that superimposes a function value of a periodically varying function of the first parameter on the reference position to cause the control signal to control the conduction of the primary side power switching transistor of the switching power supply within a predetermined range of the target valley.

[0020] To solve the above technical problems, the present application further provides a switching power supply including the above switching power supply control circuit.

[0021] This application provides a control method for a switching power supply, which relates to the technical field of switching power supplies. This method detects a resonant periodic signal of the switching power supply in real time, superimposes a delay time on the resonant periodic signal, and controls the conduction of the primary-side power switching transistor of the switching power supply within a predetermined range around a target valley of the resonant waveform based on the resonant periodic signal and the delay time. The delay time is related to a first parameter and a second parameter, the first parameter being a set value that varies over time within a certain range, and the second parameter being a function related to the resonant period of the switching power supply. This application can detect the resonant periodic signal of the switching power supply in real time, and control the primary-side power switching transistor of the switching power supply to reliably conduct within a predetermined range around the target valley based on the resonant periodic signal and the delay time, thereby improving control accuracy.

[0022] The present application further 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 a switching power supply described above.

[0023] In order to more clearly explain the technical methods in the embodiments of the present invention, the following briefly introduces the prior art and drawings that need to be used in the embodiments. However, the drawings in the following description are only some embodiments of the present invention, and it is obvious that a person skilled in the art can obtain other drawings based on these drawings without performing any creative work. [Brief explanation of the drawings]

[0024] [Figure 1a] FIG. 1 is a schematic diagram of a first waveform in the prior art. [Figure 1b] FIG. 1 is a schematic diagram of a second waveform in the prior art. [Figure 2] 1 is a flowchart of a control method for a switching power supply provided in the present application. [Figure 3] 1 is a schematic diagram of a partial configuration of a switching power supply provided in the present application; [Figure 4] 1 is a schematic diagram of the waveforms provided herein. [Figure 5] 1 is a control circuit diagram of a switching power supply provided in the present application; [Figure 6a] 1 is a schematic diagram of the operation waveforms of a switching power supply provided in the present application; [Figure 6b] FIG. 1 is a circuit diagram for generating a resonant periodic signal provided herein. [Figure 6c] FIG. 2 is a circuit diagram of the control signals provided herein. [Figure 6d] 1 is a waveform schematic diagram of a periodic function related to a first parameter provided herein; [Figure 6e] 1 is a waveform schematic diagram when the first primary-side power switching transistor provided herein conducts to the left of the target valley. [Figure 6f] 1 is a waveform schematic diagram when the first primary-side power switching transistor provided in the present application conducts at a target valley. [Figure 6g] 1 is a waveform schematic diagram when the first primary-side power switching transistor provided herein conducts on the right side of the target valley. [Figure 7a] FIG. 10 is another operating waveform schematic diagram of the switching power supply provided in the present application. [Figure 7b] FIG. 10 is a circuit diagram of another control signal provided herein. [Figure 7c] FIG. 1 is a schematic diagram of a function related to a second parameter provided herein. [Figure 7d] FIG. 10 is a waveform schematic diagram when the second primary-side power switching transistor provided herein conducts to the left of the target valley. [Figure 7e] FIG. 10 is a waveform schematic diagram when the second primary-side power switching transistor provided in the present application conducts at a target valley. [Figure 7f] FIG. 10 is a waveform schematic diagram when the second primary-side power switching transistor provided herein conducts on the right side of the target valley. [Figure 8]1 is a block diagram illustrating a configuration of a control circuit of a switching power supply provided in the present application. DETAILED DESCRIPTION OF THE INVENTION

[0025] The gist of this application is to provide a control method, circuit, and switching power supply for a switching power supply, which can detect the resonant periodic signal of the switching power supply in real time, and control the primary side power switching transistor of the switching power supply to reliably conduct within a predetermined range around the target valley based on the resonant periodic signal and delay time of the switching power supply, thereby improving the accuracy of control.

[0026] In order to clarify the objectives, technical solutions and advantages of the embodiments of the present application, the technical solutions of the embodiments of the present application are described below in detail and completely in conjunction with the drawings of the embodiments of the present application, but it is clear that the described embodiments are only some of the embodiments of the present application and do not represent all of the embodiments of the present application. All other embodiments that can be obtained by those skilled in the art based on the embodiments of the present application without performing any creative work fall within the scope of protection of the present application.

[0027] 1a and 1b, Fig. 1a is a schematic diagram of a first waveform in the prior art, and Fig. 1b is a schematic diagram of a second waveform in the prior art. In Fig. 1a and 1b, the left side represents the conduction time of the primary-side power switching transistor, the relatively high portion in the middle represents the conduction time of the secondary-side switching transistor, and the damped sine waveform on the right side represents the resonant waveform generated after the secondary-side switching transistor is turned off. In both Fig. 1a and 1b, the primary-side power switching transistor is controlled to conduct during the negative half-cycle of the third valley. However, experimental results using the prior art control method showed that the primary-side power switching transistor in Fig. 1a conducts during the negative half-cycle at a point to the left of the third valley, while the primary-side power switching transistor in Fig. 1b conducts close to the left of the third valley and at the second peak, failing to conduct during the negative half-cycle.

[0028] Referring to FIG. 2, FIG. 2 is a flowchart of a control method for a switching power supply provided in the present application, which includes: S11 detects a resonant periodic signal of a switching power supply in real time, Specifically, the resonant periodic signal here represents the resonant signal of the switching power supply, and specifically represents the state of the zero crossing point of the resonant waveform (for example, 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). Specifically, see Tdem in the following first and second embodiments. S11 and and S12, which controls the conduction of the primary side power switching transistor of the switching power supply within a predetermined range around a target valley of the resonant waveform based on the resonant periodic signal and the delay signal by superimposing a delay time on the resonant periodic signal; The delay time is related to a first parameter and a second parameter, the first parameter being a set value that varies over time within a certain range, and the second parameter being a function related to the resonant period of the switching power supply.

[0029] After detecting the resonant periodic signal as described above, a delay time is superimposed after one of the resonant periods, so that the control signal generated in the resonant periodic signal portion controls the primary side power switching transistor to conduct within a predetermined range around the target valley of the resonant waveform after the delay time.

[0030] Specifically, to improve the EMI performance of the system, the primary-side power switching transistor of the present invention conducts at different positions of the negative half cycle where the target valley is located in two adjacent cycles, where the predetermined range of the target valley does not exceed the negative half cycle where the target valley is located, i.e., the conduction within the predetermined range of the target valley here refers to controlling the primary-side power switching transistor to oscillate and conduct within the predetermined range of the target valley in different cycles, and the positions of the conduction in the two adjacent cycles are different.

[0031] The above delay time is related to the first parameter and the second parameter, and the first parameter is a setting that changes over time, and the second parameter is a function related to the resonance period. Therefore, in the control method of the present application, the delay time is determined based on the resonance period, thereby determining the conduction time of the primary side power switching transistor, thereby increasing the reliability of the conduction of the primary side power switching transistor.

[0032] In a preferred embodiment, the predetermined range is associated with a periodically varying function associated with the first parameter; By superimposing a delay time on the resonant periodic signal, the control signal controls the conduction of the primary side power switching transistor of the switching power supply within a predetermined range around the target valley of the resonant waveform based on the resonant periodic signal and the delay signal. When a function value of the periodic transformation function associated with the first parameter is zero, adjusting a second parameter to cause the control signal to correspond to a reference position of the center or a left or right side of a target valley in the resonant waveform based on the resonant periodic signal and the delayed signal; and superimposing a function value of a periodically varying function of the first parameter on a reference position to cause the control signal to control the conduction of the primary side power switching transistor of the switching power supply within a predetermined range of the target valley.

[0033] Specifically, when the periodic change function corresponding to the first parameter is related to a predetermined range, specifically when the periodic change function is one of the jitter frequency amounts of 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 effect of the first parameter is to ensure that the primary side power switching transistor conducts within a range near the target valley, and does not allow it to be fixed at one position of the target valley.

[0034] At this time, if the function value of the periodic change function corresponding to the first parameter is zero (i.e., if the corresponding Ij(m) in FIG. 6d is zero, then m is 1 or 2*2x-2 or 2 x (=0.001) means that the jitter frequency amount superimposed on the delay time is zero, that is, at this time, the primary-side power switching transistor conducts accurately at a reference position either at the target valley portion or on the left or right side of the target valley. Therefore, if the primary-side power switching transistor does not conduct accurately at the reference position at this time, it means that the second parameter is inaccurate. In other words, by selecting to adjust the second parameter when the function value of the periodically varying function corresponding to the first parameter is zero, it is ensured that after the jitter frequency amount is superimposed, the primary-side power switching transistor conducts accurately at any time within a predetermined range around the target valley.

[0035] In the above, the control signal is aligned with a reference position near the target valley, and then a periodic function related to the first parameter is superimposed on the reference position. The control signal is periodically moved near the reference position, and the conduction of the primary-side power switching transistor is controlled based on this control signal, causing the primary-side switching transistor to oscillate near the reference position and become conductive. In a specific embodiment, the reference position is the center of the target valley.

[0036] In a preferred embodiment, adjusting the second parameter comprises: Obtaining a resonance period of the resonance waveform; and self-adaptively adjusting the second parameter based on the resonant period to cause the control signal to control conduction of the primary-side power switching transistor at the target valley.

[0037] Specifically, since the second parameter is a function related to the resonance period (specifically, the second parameter can be k, see the examples below), one means of adjusting the second parameter in the present application is to self-adaptively adjust the second parameter based on the resonance waveform, the purpose of which is to control the control signal to be accurately conducted at a reference position on the center or left or right side of the target valley when the function value of the periodically changing function corresponding to the first parameter is zero.

[0038] In a preferred embodiment, obtaining the resonant period of the resonant waveform comprises: determining the sum of the time between a number of consecutive valleys or peaks or consecutive zero crossings in the resonant waveform; Calculating the resonant period based on the sum of the time and the number of valleys or peaks or zero crossing points.

[0039] The purpose of this embodiment is to calculate the resonance period through a specific implementation method for obtaining the resonance period, specifically, based on the sum of the time between a number of consecutive peaks and valleys in the resonance waveform, or the sum of the time between a number of consecutive valleys, or the sum of the time between a number of consecutive zero-crossing points, and the corresponding number of peaks, or the number of valleys, or the number of zero-crossing points.

[0040] For example, if the sum of the time of N consecutive zero crossing points is t1, then the resonant period T = 2t1 / N (there are two zero crossing points in each period, one from the positive half period to the negative half period, and one from the negative half period to the positive half period). For example, if the sum of the time of n consecutive valleys is t2, then the resonant period T = t2 / n. The formula for calculating the peak is the same as that for the valley, so it will not be described again here.

[0041] In order to ensure the accuracy and reliability of the switching power supply control, in the present application, the resonance period of the switching power supply is detected at regular time intervals and the resonance period of the switching power supply is updated as needed so that the second parameter can be adjusted based on the latest resonance period detected at that time.

[0042] In a preferred embodiment, adjusting the second parameter comprises: acquiring operating parameters of the switching power supply at predetermined time intervals; determining a second parameter based on the operating parameter and a mapping relationship between the preset operating parameter and the second parameter.

[0043] The purpose of this embodiment is to provide another method for adjusting the second parameter. Specifically, in this embodiment, a mapping relationship between a preset operating parameter and a second parameter is preset. After the operating parameters of the switching power supply are determined, the mapping relationship between the preset operating parameter and the delay time can be searched based on the operating parameters of the switching power supply to determine the second parameter corresponding to the operating parameters. Then, the delay time is adjusted based on the 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 switching transistor to ensure conduction at the target valley.

[0044] In a preferred embodiment, after acquiring the operating parameters of the switching power supply at predetermined time intervals, determining whether a change in an operating parameter has occurred; If a change occurs, proceeding to determine the second parameter based on the operating parameter and the preset operating parameter-second parameter mapping relationship.

[0045] Specifically, in this embodiment, the change in the second parameter is usually caused by a change in the operating parameter of the switching power supply. Therefore, in this application, the operating parameter of the switching power supply is also detected, and if a change occurs in the operating parameter, the step of determining the second parameter can proceed. If the time interval between two adjacent detections of the operating parameter is sufficiently short, this is equivalent to monitoring the operating parameter of the switching power supply in real time.

[0046] In a preferred embodiment, determining whether a change in an operating parameter has occurred comprises: determining whether a change in the level of the operating parameter has occurred; and determining that a change has occurred in the operating parameter if a change has occurred in the level.

[0047] Specifically, in order to prevent triggering determination of the second parameter when the change in the operating parameter is very small, the second parameter needs to be determined frequently, which consumes a considerable amount of power from the processor.

[0048] Therefore, in this application, the operating parameters are divided into different levels, and in this case, the specific implementation method for determining whether a change has occurred in the operating parameters is to determine whether a change has occurred in the level of the operating parameters, and if a change has occurred, it is determined that a change has occurred in the operating parameters.Only at this time is the step of determining the second parameter triggered, which prevents the step of determining the second parameter from being triggered frequently and can reduce the power consumption of the processor to a certain extent.

[0049] In a preferred embodiment, the operating parameters include a combination of one or more of the primary input voltage, secondary output voltage, and load value of the switching power supply.

[0050] The purpose of this embodiment is to limit the specific realization method of the operating parameters. Specifically, the operating parameters may be, but are not limited to, the primary input voltage, secondary output voltage, load value, etc. of the switching power supply.

[0051] The range of the primary input voltage may be 90 VAc to 265 VAc, and the range of the output voltage may be 3.3 V to 21 V, but is not limited to these. When dividing the above operating parameters into levels, the ranges of the primary input voltage, secondary output voltage, and load value may be divided into several positions (levels) based on actual demand, and the present application does not particularly limit how they are divided.

[0052] In a preferred embodiment, when the operating parameters include a primary input voltage and a secondary output voltage of a switching power supply, Obtaining the operating parameters of a switching power supply is calculating a primary side input voltage based on a voltage of the auxiliary winding, a number of turns of the auxiliary winding, and a number of turns of the primary winding when the primary side power switching transistor is conducting; calculating a secondary-side output voltage 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 switching transistor is conductive; Among them, the auxiliary winding and the primary winding have a common base.

[0053] The purpose of this embodiment is to define a specific implementation method for calculating the primary input voltage and the secondary output voltage. Specifically, the specific method for calculating the primary input voltage may 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 switching transistor is conductive. Specifically, refer to Figure 3, which is a partial structural schematic diagram of the switching power supply provided in this application. The primary input voltage is calculated by the pull-up resistor R DEM Specifically,

[0054]

number

[0055] where Vin is the primary input voltage, I DEMAG is the current through 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.

[0056] A specific method for calculating the secondary output voltage may be to calculate the secondary output voltage 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 switching transistor is turned on. For example, see FIG. 4, which is a waveform diagram provided in this application. The secondary output voltage is calculated by V during the Tons and Toff periods. DEM Of these, Tons is the time period when the secondary side switching transistor is conducting, Toff is the time period when the secondary side switching transistor is cut off but the primary side power switching transistor of the next cycle is not yet conducting (i.e. the time period when resonance occurs), and Gate / Tonp in Figure 4 is the time period when the primary side power switching transistor is conducting. At this time,

[0057]

number

[0058] where Vo is the secondary output voltage, Vaux is the voltage on the auxiliary winding when the secondary switching transistor is conductive, Na is the number of turns in the auxiliary winding, and Ns is the number of turns in the secondary winding.

[0059] In a preferred embodiment, when the operating parameters include a load value: Obtaining the operating parameters of a switching power supply is Obtaining a switching frequency of a primary side power switching transistor in a switching power supply; determining a load value based on the switching frequency; Among them, the load value is directly correlated with the switching frequency.

[0060] The purpose of this embodiment is to define a specific implementation method for determining the load value. Specifically, the current load value of a switching power supply is determined based on the switching frequency of the primary power switching transistor in the switching power supply. The switching frequency of the primary power switching transistor is positively correlated with the load value. Specifically, the switching period of the primary power switching transistor is the conduction time of the primary power switching transistor + the conduction time of the secondary power switching transistor + the resonance time (i.e., the period from the start of resonance until the primary power switching transistor is turned on at the determined target valley). Currently, when the load of the switching power supply is relatively light, a later valley in the resonance waveform is selected, and the corresponding switching period is relatively large and the switching frequency is relatively small. When the load of the switching power supply is relatively heavy, a later valley in the resonance waveform is selected, and the corresponding switching period is relatively small and the switching frequency is relatively large. Therefore, when the load value of a switching power supply needs to be determined, it can be determined based on the current switching frequency of the primary power switching transistor.

[0061] Of course, the above is only one implementation method provided by this embodiment, and it is also possible to directly detect the load value using a detection device, and this is not limited in this application.

[0062] In a preferred embodiment, by superimposing a delay time on the resonant periodic signal, the control signal controls the conduction of the primary side power switching transistor of the switching power supply within a predetermined range around the target valley of the resonant waveform based on the resonant periodic signal and the delay signal. determining a target valley based on a load value of the switching power supply, and then detecting a zero crossing point one before the valley one before the target valley; The control signal corresponding to the immediately preceding zero crossing point is delayed by the delay time to set the conduction time as the conduction time, thereby causing the control signal to control the conduction of the primary side power switching transistor at the conduction time.

[0063] Specifically, the determination of the conduction time in this 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. Specifically, the method for determining the conduction time is to determine a valley before the target valley, then detect a zero-crossing point before the determined valley, and delay the delay time, i.e., the conduction time, based on the zero-crossing point time. This conduction time is any time around the target valley. This method can accurately determine the target valley, and by constantly adjusting the conduction frequency of the primary power switching transistor in the switching power supply, it is possible to avoid keeping the frequency of the primary power switching transistor constant and improve the EMI performance of the switching power supply.

[0064] The design goal of the present application is to control the primary-side power switch to conduct during the negative half-cycle of the target valley, for which the present application provides two embodiments. Referring to Figures 5 and 6a to 6g as a first embodiment, Figure 5 is a control circuit diagram of a switching power supply provided herein, Figure 6a is a schematic diagram of the operating waveforms of the switching power supply provided herein, Figure 6b is a circuit diagram of a circuit provided herein for generating a resonant periodic signal, Figure 6c is a circuit diagram of a control signal provided herein, and Figure 6d is a schematic waveform diagram of a periodic function related to a first parameter provided herein. The first embodiment is described below.

[0065] 6a is the result of comparing DEMAG in FIG. 6b with 0V, i.e., Tdem is a signal representing the zero crossing point of the resonant waveform. In this embodiment, Tdem is the above-mentioned resonant periodic signal. Vds in FIG. 6a is the resonant waveform on the primary side power switching transistor.

[0066] In FIG. 6c, the input CLK of the x-bits jitter counter may be an oscillator output or a SW signal. The x-bits jitter counter counts the CLK and sets the count result m to 1 to 2. x The x-bits jitter counter can be loop counted, and m=2 x In this case, m=1 (m is the first parameter mentioned above) after the next CLK. By realizing D to I in Figure 6c, m can be converted into the output current Ij(m) as shown in Figure 6d, of which the range of Ij(m) is 2 x-2 *Istep~-(2 x-2 -1)*Istep, where Ij(m) is a periodic function related to the first parameter above.

[0067] The Valley Lockout module selects the conduction of the nth Valley based on the load of the switching power supply (specifically, the COMP voltage in Figure 5) (i.e., the valley lockout is determined by the load).

[0068] The Current Table module detects the primary input voltage and secondary output voltage using DEMAG, and selects the preset output current It(k) based on the primary input voltage, secondary output voltage and target Valley(n), and sets m=1 or m=2*2 x-2 When Tpulse (control signal) corresponds to the valley, if the primary input voltage, secondary output voltage, and system load value do not change, k (second parameter) does not change.

[0069] n-1th Tdem n-1After the rising edge of d (m,k) and the nth Tpulse n (Tpulse n =Tdem n-1 +t d (m,k)) are generated. d The specific realization method of (m,k) is t d (m,k)=C*Vref / [Ij(m)+It(k)].

[0070] nth Tpulse n At the rising edge of , the primary side power switching transistor conducts.

[0071] m=1 or m=2*2 x-2 If so, Tpulse n corresponds to conduction at the reference position of the negative half cycle where the target valley is located, and the specific reference position may be the target valley. Moreover, since Ij(m) changes periodically, it is possible to realize oscillation and conduction in the negative half cycle region of the primary side power switching transistor.

[0072] FIG. 6e is a waveform diagram when the first primary-side power switching transistor provided in the present application is conducting on the left side of the target valley, where m=2 x-2 , Ij(m) is a positive value, and Tpulse is to the left of the reference position (target valley).

[0073] 6f is a waveform diagram when the first primary-side power switching transistor provided in the present application is turned on at the target valley, where m=1 or 2*2 x-2 , Ij(m) is zero and Tpulse is at the reference position (target valley).

[0074] Figure 6g is a waveform diagram when the first primary-side power switching transistor provided in the present application is conducting on the right side of the target valley, where m=3*2 x-2 , Ij(m) is a negative value, and Tpulse is to the right of the reference position (target valley).

[0075] Referring to Figures 7a to 7f as a second embodiment, Figure 7a is a schematic diagram of another operating waveform of the switching power supply provided in the present application, Figure 7b is a circuit diagram of another control signal provided in the present application, and Figure 7c is a schematic diagram of a function related to a second parameter provided in the present application, and the second embodiment is described below.

[0076] In this embodiment, the DLL (Delay-Locked Loop) principle is adopted, and Tpulse n (rising edge) and the reference signal, and dynamically adjust td(m,k) to determine the Tpulse when m is a fixed value (the function value of the function corresponding to m is zero). n It is adapted for volleyball.

[0077] By sampling Tdem and generating Tmid (Tdem falling edge + 0.75 * tdem) based on Tdem, the falling edge of Tmid corresponds to the valley of the resonant waveform, as shown in Figure 7a.

[0078] m=1 or 2*2 x-2 At this time, the positional relationship between the rising edge of Tpulse and the falling edge of Tmid is compared, and the range of k is set to 1 to 2 according to the SW cycle. y (y is the counter value).

[0079] If the Tmid falling edge precedes the Tpulse rising edge, k n =k n-1 +1, k if Tmid falling edge is after Tpulse rising edge n =k n-1 -1, m≠1 and m≠2*2 x-2 In the case of k n =k n-1 is.

[0080] The D to I module in Figure 7b converts k into the output current It(k), as shown in Figure 7c. It(k) ranges from Iini to Iini + (2 y -1)*iTunes.

[0081] Finally, after some period, td(m,k) is dynamically adjusted to m=1 or m=2*2. x-2 (i.e., when the function value Ij(m) of the periodic function related to the first parameter m is zero), the rising edge of Tpulse is located in the valley and dynamically follows the change in the resonance period when the mode is changed.

[0082] m=1 or m=2*2 x-2 If (the function value of the periodic function corresponding to the first parameter is zero), Tpulse n corresponds to conduction at a reference position of a negative half-cycle of a target valley, and the specific reference position can be the target valley. Furthermore, Ij(m) changes periodically, so that conduction in the negative half-cycle region of the target valley of the primary side power switching transistor can be realized.

[0083] Figure 7d is a waveform diagram when the second primary-side power switching transistor provided in the present application is conducting on the left side of the target valley, where m=2 x-2 , Ij(m) is a positive value, and Tpulse is to the left of the reference position (target valley).

[0084] 7e is a waveform diagram of the second primary-side power switching transistor provided in the present application when it is turned on at the target valley. At this time, m=1 or 2*2 x-2 , Ij(m) is zero and Tpulse is at the reference position (target valley).

[0085] 7f is a waveform diagram when the second primary-side power switching transistor provided in the present application is conducting on the right side of the target valley, where m=3*2 x-2 , Ij(m) is a negative value, and Tpulse is to the right of the reference position (target valley).

[0086] In order to solve the above technical problems, the present application further provides a control circuit for a switching power supply. Referring to FIG. 8, FIG. 8 is a block diagram of the control circuit for a switching power supply provided in the present application, and the circuit comprises: a detection unit 81 for detecting the resonant periodic signal of the switching power supply in real time; a control unit 82 for controlling the conduction of the primary side power switching transistor of the switching power supply within a predetermined range around a target valley of the resonant waveform based on the resonant periodic signal and the delay signal by superimposing a delay time on the resonant periodic signal; The delay time is related to a first parameter and a second parameter, the first parameter being a set value that varies over time within a certain range, and the second parameter being a function related to the resonant period of the switching power supply.

[0087] In a preferred embodiment, the control unit comprises: a resonant valley correspondence circuit for adjusting a second parameter when the function value of the periodic transformation function associated with the first parameter is zero, to cause the control signal to correspond to a reference position of the center or a left or right side of the target valley in the resonant waveform based on the resonant periodic signal and the delay signal; and a jitter frequency circuit that superimposes a function value of a periodically varying function of the first parameter on a reference position to cause the control signal to control the conduction of the primary side power switching transistor of the switching power supply within a predetermined range of the target valley.

[0088] The control circuit of the switching power supply can be described by referring to the above embodiment, and therefore will not be described again in this application.

[0089] In order to solve the above technical problems, the present application further provides a switching power supply including the above switching power supply control circuit. The description of the switching power supply can be referred to the above embodiments, and will not be repeated in the present application.

[0090] It should be further explained that, as used herein, relational terms such as "first," "second," etc., are used solely to distinguish one entity or operation from another and do not necessarily require or imply any substantial relationship or sequence between those entities or operations. Furthermore, the terms "comprise," "include," or any other variation thereof, cover non-exclusive inclusions, such that a process, method, article, or facility that includes a set of elements not only includes those elements but may also include other elements not specifically listed or that are inherent in such a process, method, article, or facility. Unless more restrictive, an element defined by the phrase "comprising a..." does not exclude the presence of additional identical elements within the process, method, article, or facility that includes the element.

[0091] The above description of the disclosed embodiments will enable one skilled in the art to make or use the present application. Various modifications to these embodiments will be 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 the present application. Thus, the present application is not intended 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. 1. A method for controlling a switching power supply, comprising: Detecting a resonant periodic signal of a switching power supply in real time; and controlling conduction of a primary-side power switching transistor of the switching power supply within a predetermined range around a target valley of a resonant waveform using a control signal generated based on superimposing a delay time on the resonant periodic signal, the delay time is related to a first parameter and a second parameter, the first parameter is a set value that varies over time within a certain range, and the second parameter is a function related to a resonance period of the switching power supply. A method for controlling a switching power supply.

2. the predetermined range is associated with a periodically varying function associated with the first parameter; using the control signal to control conduction of a primary side power switching transistor of the switching power supply within a predetermined range around a target valley of the resonant waveform; adjusting the second parameter to cause the control signal to correspond to a reference position of the center or a left or right side of a target valley in the resonant waveform when a function value of the periodically varying function associated with the first parameter is zero; and superimposing a function value of a periodically varying function of the first parameter on the reference position, and causing the control signal to control the conduction of the primary side power switching transistor of the switching power supply within a predetermined range of the target valley. The method for controlling a switching power supply according to claim 1 .

3. adjusting the second parameter obtaining a resonance period of the resonance waveform; and self-adaptively adjusting a second parameter based on the resonant period, thereby causing the control signal to control the conduction of the primary-side power switching transistor at the target valley. The method for controlling a switching power supply according to claim 2.

4. obtaining a resonance period of the resonance waveform, obtaining the sum of the time between a number of consecutive valleys or peaks or zero crossings in the resonant waveform; and calculating the resonance period based on the sum of the times and the number of the valleys, the peaks, or the zero crossing points. The method for controlling a switching power supply according to claim 3.

5. adjusting the second parameter acquiring operating parameters of the switching power supply at predetermined time intervals; determining the second parameter based on the operational parameter and a mapping relationship between the preset operational parameter and the second parameter; The method for controlling a switching power supply according to claim 2.

6. After acquiring the operating parameters of the switching power supply at predetermined time intervals, determining whether a change has occurred in the operating parameter; If a change occurs, proceeding to a step of determining the second parameter based on the operating parameter and a mapping relationship between the preset operating parameter and the second parameter. The method for controlling a switching power supply according to claim 5.

7. Determining whether a change has occurred in the operating parameter determining whether a change has occurred in the level of the operating parameter; and determining that a change has occurred in the operating parameter when a change has occurred in the level. The method for controlling a switching power supply according to claim 6.

8. 6. The control method for a switching power supply according to claim 5, wherein the operating parameters include one or a combination of a primary input voltage, a secondary output voltage, and a load value of the switching power supply.

9. When the operating parameters include a primary input voltage and a secondary output voltage of the switching power supply, obtaining operating parameters of the switching power supply; calculating the primary side input voltage based on a voltage of an auxiliary winding, a number of turns of the auxiliary winding, and a number of turns of a primary side winding when the primary side power switching transistor is conductive; calculating the secondary-side output voltage 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 when the secondary-side switching transistor is conductive; The auxiliary winding and the primary winding have a common base. The method for controlling a switching power supply according to claim 8.

10. If the operating parameters include a load value, obtaining operating parameters of the switching power supply; obtaining a switching frequency of the primary side power switching transistor in the switching power supply; determining the load value based on the switching frequency; The load value is positively correlated with the switching frequency. The method for controlling a switching power supply according to claim 8.

11. using the control signal to control conduction of a primary side power switching transistor of the switching power supply within a predetermined range around a target valley of the resonant waveform; determining the target valley based on a load value of the switching power supply, and then detecting a zero crossing point immediately before the valley immediately before the target valley; and setting a time obtained by delaying the control signal corresponding to the immediately preceding zero crossing point by the delay time as a conduction time, thereby causing the control signal to control the conduction of the primary side power switching transistor at the conduction time. The method for controlling a switching power supply according to any one of claims 1 to 10.

12. In a control circuit of a switching power supply, a detection unit for detecting a resonant periodic signal of the switching power supply in real time; using a control signal generated based on superimposing a delay time on the resonant periodic signal, a control unit for controlling conduction of a primary side power switching transistor of the switching power supply within a predetermined range around a target valley of a resonant waveform, the delay time is related to a first parameter and a second parameter, the first parameter is a set value that varies over time within a certain range, and the second parameter is a function related to a resonance period of the switching power supply. Control circuit for switching power supply.

13. The control unit a resonant valley correspondence circuit for adjusting the second parameter when a function value of a periodically varying function associated with the first parameter is zero, to cause the control signal to correspond to a reference position of the center or a left or right side of a target valley in the resonant waveform; and a jitter frequency circuit for superimposing a function value of a periodically varying function of the first parameter on the reference position, and for controlling the control signal to control the conduction of the primary side power switching transistor of the switching power supply within a predetermined range of the target valley.

13. The control circuit for a switching power supply according to claim 12.

14. A switching power supply comprising the control circuit for a switching power supply according to claim 12 or 13.

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