Control method, circuit, and switching power supply

Abstract

In the field of switching power supplies, the present invention provides a control method, circuit, and switching power supply that can improve the accuracy of control. [Solution] The resonant period signal of the switching power supply is detected in real time, and a delay time is superimposed on the resonant period signal. The control signal is then used to control the conduction of the primary power switching transistor of the switching power supply within a predetermined range near the target valley of the resonant waveform, based on 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 changes with time within a certain range, and the second parameter is a function related to the resonant period of the switching power supply.

Description

[Technical Field]

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

[0002] In a flyback switching power supply system, when the primary power switching transistor is switched off, the secondary diode conducts, and the energy stored in the transformer begins to transfer to the secondary side. When the energy transfer is complete, the secondary diode turns off, and at this time, a damping resonance occurs between the excitation inductance in the transformer and the parasitic capacitance of the primary power switching transistor, and this resonance is maintained until the next primary power switching transistor conducts.

[0003] To reduce wear on primary-side power switching transistors, existing technologies typically control the conduction of the primary-side power switching transistors using a quasi-resonant (QR) mode of valley lockout. Specifically, by controlling the conduction of one of the valleys in 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) at this time is quite large), wear on the primary-side power switching transistor can be reduced and system efficiency can be improved. However, if the same valley in the resonant waveform is selected to conduct the primary-side power switching transistor each time the system is in operation, the system's switching frequency remains constant, and at this time, the system's EMI (Electromagnetic Interference) performance deteriorates.

[0004] To further improve the system's EMI performance, a jitter frequency of the negative half-period resonant period is superimposed in QR mode. Specifically, the primary-side power switching transistors are controlled to conduct at any time within the negative half-period where the selected valley is located. For example, if the selected valley is the second valley, the primary-side power switching transistors can be controlled to conduct to the left of the second valley at any time within the negative half-period range, or to the right of the second valley at any time within the negative half-period range. The specific implementation method involves detecting the zero point before the second valley in the resonant waveform and then controlling the conduction of the primary-side power switching transistors with a predetermined delay (this predetermined time is a change value and does not exceed half of the resonant period, thus ensuring that the time at which the primary-side power switching transistors conduct is within the negative half-period where the second valley is located), thereby changing the system's switching frequency and improving the system's EMI performance.

[0005] However, for flyback switching power supply systems with a wide input range and multi-stage voltage output, the corresponding resonant periods differ under different input / output voltage and load conditions. Therefore, when controlling the primary-side power switching transistor using the above method, there is a possibility that the primary-side power switching transistor will conduct during the positive half-period of the resonant waveform. In other words, with existing technologies, it is not possible to precisely conduct the primary-side power switching transistor at any point during the negative half-period of the selected valley, resulting in poor accuracy. [Overview of the Initiative]

[0006] The object of this application is to provide a control method, circuit, and switching power supply for a switching power supply, thereby enabling real-time detection of the resonant period signal of the switching power supply and improving control accuracy by controlling the primary power switching transistor of the switching power supply to reliably conduct within a predetermined range near the target valley based on the resonant period signal and delay time of the switching power supply.

[0007] To solve the above technical problems, the control method for a switching power supply provided in this application is: To detect the resonant period signal of the aforementioned switching power supply in real time, The control signal includes superimposing a delay time on the resonant period signal, thereby controlling the conduction of the primary power switching transistor of the switching power supply within a predetermined range near the target valley of the resonant waveform, based on the resonant period signal and the delay signal. Of these, the delay time is related to the first parameter and the second parameter, the first parameter being a set value that changes with 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 periodic change function related to the first parameter, By superimposing a delay time onto the aforementioned resonant period signal, the control signal is made to control the conduction of the primary power switching transistor of the switching power supply within a predetermined range near the target valley of the resonant waveform, based on the resonant period signal and the delay signal. When the function value of the periodic transformation function associated with the first parameter is zero, the second parameter is adjusted to make the control signal correspond to the center, left, or right reference position of the target valley in the resonant waveform, based on the resonant period signal and the delay signal. Superimposing the function value of the periodic change function of the first parameter on the reference position to control the conduction of the primary side power switching transistor of the switching power supply within a predetermined range of the target value in the control signal.

[0009] Preferably, adjusting the second parameter includes obtaining the resonance period of the resonance waveform, and self-adaptively adjusting the second parameter based on the resonance period to control the conduction of the primary side power switching transistor at the target value in the control signal.

[0010] Preferably, obtaining the resonance period of the resonance waveform includes obtaining the sum of the time between some consecutive values or consecutive peaks or consecutive zero-crossing points in the resonance waveform, and calculating the resonance period based on the sum of the time and the number of the values or the peaks or the zero-crossing points.

[0011] Preferably, adjusting the second parameter includes obtaining the operating parameters of the switching power supply at a predetermined time interval, and determining the second parameter based on the mapping relationship between the operating parameters and the pre-set operating parameters - the second parameter.

[0012] Preferably, after obtaining the operating parameters of the switching power supply at a predetermined time interval, further judging whether a change has occurred in the operating parameters, and if a change has occurred, proceeding to the step of determining the second parameter based on the mapping relationship between the operating parameters and the pre-set operating parameters - the second parameter.

[0013] Preferably, judging whether a change has occurred in the operating parameters includes To determine whether or not a change has occurred in the level of the aforementioned operating parameter, This includes determining that a change has occurred in the operating parameter if a change has occurred in the aforementioned level.

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

[0015] Preferably, the operating parameters include the primary input voltage and secondary output voltage of the switching power supply, Obtaining the operating parameters of the aforementioned switching power supply is, When the primary power switching transistor conducts, 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. The process includes calculating 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 conducts, Of these, the auxiliary winding and the primary winding share a common base.

[0016] Preferably, when the operating parameter includes a load value, Obtaining the operating parameters of the aforementioned switching power supply is, To obtain the switching frequency of the primary power switching transistor in the switching power supply, This includes determining the load value based on the switching frequency, Of these, the load value is positively correlated with the switching frequency.

[0017] Preferably, by superimposing a delay time on the resonance period signal, the control signal is made to control the conduction of the primary power switching transistor of the switching power supply within a predetermined range near the target valley of the resonance waveform, based on the resonance period signal and the delay signal. After determining the target valley based on the load value of the switching power supply, the zero-crossing point of the valley immediately preceding the target valley is detected. This includes delaying the control signal corresponding to the previous zero-crossing point by the aforementioned delay time to determine the conduction time, and causing the control signal to control the conduction of the primary-side power switching transistor at the aforementioned conduction time.

[0018] To solve the above technical problems, the control circuit of the switching power supply provided in this application is: A detection unit for real-time detection of the resonant period signal of the switching power supply, By superimposing a delay time on the resonant period signal, the control signal includes a control unit for controlling the conduction of the primary power switching transistor of the switching power supply within a predetermined range near the target valley of the resonant waveform, based on the resonant period signal and the delay signal. Of these, the delay time is related to the first parameter and the second parameter, the first parameter being a set value that changes with 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 is When the function value of the periodic transformation function associated with the first parameter is zero, the second parameter is adjusted to cause the control signal to correspond to the center, left, or right reference position of the target valley in the resonant waveform, based on the resonant period signal and the delay signal, and a resonant valley correspondence circuit is provided. The control signal includes a jitter frequency circuit that superimposes the function value of the periodic change function of the first parameter onto the reference position to control the conduction of the primary 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 invention further provides a switching power supply that includes a control circuit for the switching power supply described above.

[0021] This invention provides a method for controlling a switching power supply and relates to the technical field of switching power supplies. In this method, the resonant period signal of the switching power supply is detected in real time, and a delay time is superimposed on the resonant period signal. The control signal is then used to control the conduction of the primary-side power switching transistor of the switching power supply within a predetermined range near the target valley of the resonant waveform, based on the resonant period 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 changes with time within a certain range, and the second parameter being a function related to the resonant period of the switching power supply. This invention demonstrates that the resonant period signal of the switching power supply can be detected in real time, and that the primary-side power switching transistor of the switching power supply is controlled to reliably conduct within a predetermined range near the target valley based on the resonant period signal and the delay time, thereby improving the accuracy of the control.

[0022] This invention 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 the switching power supply described above.

[0023] To more clearly explain the technical methods in the embodiments of the present invention, the prior art and drawings necessary for use in the embodiments are briefly introduced below. However, the drawings in the following description represent only a few embodiments of the present invention, and it will be obvious to those skilled in the art that other drawings can be obtained based on these drawings without any creative work. [Brief explanation of the drawing]

[0024] [Figure 1a] This is a schematic diagram of the first waveform in the conventional technology. [Figure 1b] This is a schematic diagram of the second waveform in the conventional technology. [Figure 2] This is a flowchart of the control method for the switching power supply provided in this invention. [Figure 3] This is a schematic diagram of the partial configuration of the switching power supply provided in this application. [Figure 4] This is a schematic diagram of the waveform provided in this application. [Figure 5] This is a control circuit diagram for the switching power supply provided in this application. [Figure 6a] This is a schematic diagram of the operating waveform of the switching power supply provided in this application. [Figure 6b] This is a circuit diagram for generating the resonant period signal provided in this application. [Figure 6c] This is a circuit diagram of the control signal provided in this application. [Figure 6d] This is a schematic waveform diagram of a periodic function related to the first parameter provided in this application. [Figure 6e] This is a schematic waveform diagram when the first primary-side power switching transistor provided in this application conducts on the left side of the target valley. [Figure 6f] This is a schematic waveform diagram when the first primary-side power switching transistor provided in this application conducts in the target valley. [Figure 6g] This is a schematic waveform diagram when the first primary-side power switching transistor provided in this application conducts on the right side of the target valley. [Figure 7a] This is another schematic diagram of the operating waveform of the switching power supply provided in this application. [Figure 7b] This is a circuit diagram of another control signal provided in this application. [Figure 7c] This is a schematic diagram of the function related to the second parameter provided in this application. [Figure 7d] This is a schematic waveform diagram when the second primary-side power switching transistor provided in this application conducts on the left side of the target valley. [Figure 7e] This is a schematic waveform diagram when the second primary-side power switching transistor provided in this application conducts in the target valley. [Figure 7f] This is a schematic waveform diagram when the second primary-side power switching transistor provided in this application conducts on the right side of the target valley. [Figure 8]This is a block diagram of the control circuit configuration for the switching power supply provided in this application. [Modes for carrying out the invention]

[0025] The core of this invention is to provide a control method, circuit, and switching power supply for a switching power supply, thereby enabling real-time detection of the resonant period signal of the switching power supply and improving control accuracy by controlling the primary-side power switching transistor of the switching power supply to reliably conduct within a predetermined range near the target valley based on the resonant period signal and delay time of the switching power supply.

[0026] To further clarify the purpose, technical methods, and advantages of the embodiments of this application, the technical methods of the embodiments are described below in clear and complete terms, in conjunction with the drawings of the embodiments. However, it is clear that the embodiments described are only a portion of the embodiments of this application, not all of them. All other embodiments obtained by a person skilled in the art, based on the embodiments of this application and without any creative work, fall within the scope of protection of this application.

[0027] Referring to Figures 1a and 1b, Figure 1a is a schematic diagram of the first waveform in the prior art, and Figure 1b is a schematic diagram of the second waveform in the prior art. In Figures 1a and 1b, the left side represents the conduction time of the primary power switching transistor, the relatively high portion in the middle represents the conduction time of the secondary switching transistor, and the attenuated sinusoidal waveform on the right is the resonant waveform generated after the secondary switching transistor is shut off. In both Figures 1a and 1b, the primary power switching transistor is controlled to conduct during the negative half-period of the third valley. However, experimental results using the control method in the prior art show that the primary power switching transistor in Figure 1a conducts at a point slightly to the left of the third valley during the negative half-period, and the primary power switching transistor in Figure 1b conducts near the left side of the third valley, and even at the position of the second peak, thus failing to satisfy the requirement of conduction during the negative half-period.

[0028] Referring to Figure 2, Figure 2 is a flowchart of the control method for the switching power supply provided in this application, and this method is S11 detects the resonant period signal of the switching power supply in real time, Specifically, the resonant period signal here represents the resonant signal of the switching power supply, and more specifically, it can represent the state of the zero-crossing point of the resonant waveform (for example, when the resonant waveform is in a positive half-period, the resonant period signal is at a high level, and when the resonant waveform is in a negative half-period, the resonant period signal is at a low level). Specifically, refer to Tdem in the first and second embodiments below, S11, S12 includes superimposing a delay time on the resonant period signal, thereby causing the control signal to control the conduction of the primary power switching transistor of the switching power supply within a predetermined range near the target valley of the resonant waveform based on the resonant period signal and the delay signal. Of these, the delay time is related to the first and second parameters; the first parameter is a set value that changes over time within a certain range, and the second parameter is a function related to the resonant period of the switching power supply.

[0029] After detecting the resonant period signal as described above, a delay time is superimposed after one of the resonant periods. This causes the control signal generated in the resonant period signal portion to be controlled so that, after the delay time, the primary power switching transistor conducts within a predetermined range near the target valley of the resonant waveform.

[0030] Specifically, in order to improve the EMI performance of the system, the primary-side power switching transistor of this invention conducts at different positions within the negative half-cycle where the target valley is located in two adjacent periods. Of these, the predetermined range of the target valley does not exceed the negative half-cycle in which the target valley is located; that is, 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 periods, and the positions of the two adjacent conductions are different.

[0031] The above delay time is related to the first and second parameters, and the first parameter is a setting that changes with time, while the second parameter is a function related to the resonant period. Therefore, in the control method of the present invention, by determining the delay time based on the resonant period, the conduction time of the primary-side power switching transistor can be determined, thereby increasing the reliability of conduction of the primary-side power switching transistor.

[0032] In a preferred embodiment, the predetermined range is related to a periodic change function associated with the first parameter, By superimposing a delay time on the resonant period signal, the control signal can be used to control the conduction of the primary power switching transistor of the switching power supply within a predetermined range near the target valley of the resonant waveform, based on the resonant period signal and the delay signal. When the function value of the periodic transformation function associated with the first parameter is zero, the second parameter is adjusted to make the control signal correspond to the center, left, or right reference position of the target valley in the resonant waveform, based on the resonant period signal and the delay signal. This includes superimposing the function value of the periodic change function of the first parameter onto a reference position, thereby causing the control signal to control the conduction of the primary 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 jitter frequency amount in the delay time (in a specific embodiment, the first parameter is m in Figure 6d, and the periodic change function related to the first parameter is Ij(m) in Figure 6d), the action of the first parameter is to ensure conduction within the range near the target valley of the primary-side power switching transistor, and to prevent it from being fixed at one position in 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 Figure 6d is zero, then m is 1 or 2*2)x-2 or 2 x This means that the amount of jitter frequency superimposed on the delay time is zero, i.e., at this time the primary power switching transistor conducts precisely at the target valley portion or at a reference position either to the left or right of the target valley. Therefore, if the primary power switching transistor does not conduct precisely at the reference position at this time, it means that the second parameter is inaccurate. In other words, by choosing to adjust the second parameter when the function value of the periodic change function corresponding to the first parameter is zero, it is guaranteed that after the amount of jitter frequency is superimposed, the primary power switching transistor will conduct precisely at some point within a predetermined range near the target valley.

[0035] In the above, after aligning the control signal with a reference position near the target valley, a function of a periodic change related to the first parameter is superimposed based on the reference position, and the control signal is periodically moved near the reference position. By controlling the conduction of the primary-side power switching transistor based on this control signal, the primary-side switching transistor oscillates and conducts near the reference position. In a specific embodiment, the reference position is the center of the target valley.

[0036] As a preferred embodiment, adjusting the second parameter is: To obtain the resonant period of the resonant waveform, This includes adjusting a second parameter based on the resonant period to enable the control signal to control the conduction of the primary-side power switching transistor in the target valley.

[0037] Specifically, since the second parameter is a function related to the resonance period (specifically, the second parameter can be denoted as k, as shown in the embodiment below), one means of adjusting the second parameter in this application is to self-adaptively adjust the second parameter based on the resonance waveform, and the objective is to control the control signal to conduct accurately at the center of the target valley or at a reference position to the left or right when the function value of the periodic change function corresponding to the first parameter is zero.

[0038] As a preferred embodiment, obtaining the resonant period of the resonant waveform is This involves calculating the sum of time intervals between a series of valleys or peaks, or series of zero-crossing points, in the resonant waveform. This includes calculating the resonant period based on the sum of time and the number of valleys, peaks, or zero-crossing points.

[0039] The objective of this embodiment is to calculate the resonant period through a specific implementation method for obtaining the resonant period, specifically based on the sum of the time between several consecutive peaks and valleys in the resonant waveform, or the sum of the time between several consecutive valleys, or the sum of the time between several 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 times of N consecutive zero-crossing points is t1, then the resonant period T = 2t1 / N (each period has two zero-crossing points: 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 times of n consecutive valleys is t2, then the resonant period T = t2 / n. The formula for calculating the peak is the same as for the valleys, so it will not be described again in this application.

[0041] To ensure the accuracy and reliability of switching power supply control, this invention detects the resonant period of the switching power supply at regular time intervals and updates the resonant period of the switching power supply as needed, so that the second parameter can be adjusted based on the most recently detected resonant period at that time.

[0042] As a preferred embodiment, adjusting the second parameter is: To acquire the operating parameters of the switching power supply at predetermined time intervals, This includes determining the second parameter based on the mapping relationship between the operating parameter and the pre-set operating parameter and the second parameter.

[0043] The objective of this embodiment is to provide another implementation method for adjusting the second parameter. Specifically, in this invention, a mapping relationship between a pre-set operating parameter and a second parameter is pre-set. After determining the operating parameter of the switching power supply, the mapping relationship between the pre-set operating parameter and the delay time can be searched based on the operating parameter of the switching power supply, and the second parameter corresponding to the operating parameter can be determined. Subsequently, by adjusting the delay time based on this second parameter, the control signal is controlled so that the primary-side power switching transistor reliably conducts in the target valley when the function value of the periodic change function corresponding to the first parameter is zero.

[0044] As a preferred embodiment, after acquiring the operating parameters of the switching power supply at predetermined time intervals, To determine whether or not a change has occurred in the operating parameters, This includes, if a change occurs, proceeding to a step of determining the second parameter based on the operating parameter and the mapping relationship between the pre-set operating parameter and the second parameter.

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

[0046] As a preferred embodiment, determining whether or not a change has occurred in the operating parameters is: To determine whether or not a change has occurred in the level of the operating parameters, This includes determining that a change has occurred in the operating parameters if a change in the level has occurred.

[0047] Specifically, in order to prevent triggering confirmation of the second parameter when the change in the operating parameter is extremely small, the second parameter needs to be confirmed frequently, which significantly increases the power consumption of the processor.

[0048] Therefore, in this application, the operating parameters are divided into different levels. In this case, the specific implementation method for determining whether or not a change has occurred in the operating parameters is to determine whether or not a change has occurred in the level of the operating parameters, and if a change has occurred, to determine that a change has occurred in the operating parameters. At this point, the step of determining the second parameter is triggered for the first time, thus preventing the step of determining the second parameter from being triggered frequently and reducing the power consumption of the processor to some extent.

[0049] In a preferred embodiment, the operating parameters include one or more combinations 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 implementation method of the operating parameters. Specifically, the operating parameters may be, but are not limited to, the primary input voltage, secondary output voltage, and load value of the switching power supply.

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

[0052] As a preferred embodiment, when the operating parameters include the primary input voltage and secondary output voltage of the switching power supply, Obtaining the operating parameters of a switching power supply is When the primary power switching transistor conducts, 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. This includes calculating 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 conducts, Of these, the auxiliary winding and the primary winding share a common base.

[0053] The objective of this embodiment is to limit the specific implementation method for calculating the primary input voltage and 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 conducts. Specifically, one can refer to Figure 3, which is a schematic diagram of the partial configuration of the switching power supply provided in this application. The primary input voltage is calculated based on the pull-up resistor R flowing through the terminal of the auxiliary winding. DEM This is derived by detecting, and specifically,

[0054]

number

[0055] And of these, Vin is the primary input voltage, I DEMAG R is the current across the pull-up resistor. DEM is 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.

[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 conducts. Specifically, refer to Figure 4, which is a schematic waveform diagram provided in this application. Among these, the secondary output voltage is calculated based on the voltage of the auxiliary winding, the voltage of the auxiliary winding, and the number of turns of the secondary winding. DEM This is obtained by detecting the voltage. Of these, Tons is the time period when the secondary switching transistor conducts, Toff is the time period when the secondary switching transistor is closed but the primary power switching transistor for the next cycle has not yet conducted (i.e., the time period when resonance occurs), and Gate / Tonp in Figure 4 is the time period when the primary power switching transistor conducts. At this time,

[0057]

number

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

[0059] A preferred embodiment is when the operating parameters include a load value, Obtaining the operating parameters of a switching power supply is To obtain the switching frequency of the primary power switching transistor in the switching power supply, This includes determining the load value based on the switching frequency, Of these, the load value is positively correlated with the switching frequency.

[0060] The objective of this embodiment is to limit the specific implementation method for determining the load value. Specifically, the load value of the switching power supply at a given time is determined based on the switching frequency of the primary-side power switching transistor in the switching power supply. Of these, the switching frequency of the primary-side power switching transistor exhibits a positive correlation with the load value. Specifically, the switching period of the primary-side power switching transistor is the conduction time of the primary-side power switching transistor + the conduction time of the secondary-side switching transistor + the resonance time (specifically, the time period from the start of resonance until the primary-side power switching transistor conducts at the determined target valley). Currently, when the load on the switching power supply is relatively light, a valley towards the end of the resonance waveform is selected, and in this case, the corresponding switching period is relatively large and the switching frequency is relatively small. When the load on the switching power supply is relatively heavy, a valley towards the beginning of the resonance waveform is selected, and in this case, the corresponding switching period is relatively small and the switching frequency is relatively large. Therefore, when it is necessary to determine the load value of the switching power supply, it is sufficient to determine it based on the switching frequency of the primary-side power switching transistor at that time.

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

[0062] As a preferred embodiment, by superimposing a delay time on the resonant period signal, the control signal is made to control the conduction of the primary power switching transistor of the switching power supply within a predetermined range near the target valley of the resonant waveform, based on the resonant period signal and the delay signal. After determining the target valley based on the load value of the switching power supply, the zero-crossing point of the valley immediately preceding the target valley is detected, This includes delaying the control signal corresponding to the previous zero-crossing point by a delay period 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 position of the target valley is determined by detecting the zero-crossing point of the resonant waveform. Specifically, the method for determining the conduction time involves determining the valley preceding the target valley, detecting the zero-crossing point time preceding the determined valley, and delaying the delay time, i.e., the conduction time, based on that zero-crossing point time. This conduction time is any time near the target valley. Through the method in this application, the target valley can be accurately determined, and by constantly adjusting the conduction frequency of the primary-side power switching transistor in the switching power supply, it is possible to avoid keeping the frequency of the primary-side power switching transistor constant and thereby improve the EMI performance of the switching power supply.

[0064] The design objective of this application is to control the primary power switch to conduct during the negative half-period of the target valley, and to that end, this application provides two embodiments. Referring to Figures 5 and 6a to 6g as the first embodiment, Figure 5 is a control circuit diagram of the switching power supply provided in this application, Figure 6a is a schematic diagram of the operating waveform of the switching power supply provided in this application, Figure 6b is a circuit diagram of the resonant period signal provided in this application, Figure 6c is a circuit diagram of the control signal provided in this application, and Figure 6d is a schematic waveform of the periodic function related to the first parameter provided in this application. The first embodiment is described below.

[0065] Among them, Tdem in FIG. 6a is the result of comparing DEMAG in FIG. 6b with 0V. That is, Tdem is a signal characterizing the zero-crossing point of the resonance waveform. In this embodiment, Tdem is used as the above-mentioned resonance period signal. Vds in FIG. 6a is the resonance 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 CLK and outputs the count result m within the range of 1 to 2 x and can loop count. When m = 2 x after the next CLK, m = 1 (m is the above-mentioned first parameter). By realizing D to I in FIG. 6c, as shown in FIG. 6d, m can be converted into the output current Ij(m), where the range of Ij(m) is 2 x-2 *Istep to -(2 x-2 -1)*Istep (where Ij(m) here is a periodic function related to the above-mentioned first parameter).

[0067] The Valley Lockout module selects the conduction of the nth Valley based on the load of the switching power supply (the specific position is the COMP voltage in FIG. 5) (that is, the valley lockout is determined by the load).

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

[0069] The (n - 1)th Tdem n-1After the rising edge, delay t d (m,k) then the nth Tpulse n (Tpulse n =Tdem n-1 +t d (m,k)) is generated. Of these, t d The specific implementation method for (m,k) is t d (m,k) = C*Vref / [Ij(m)+It(k)] is acceptable.

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

[0071] m=1 or m=2*2 x-2 If so, Tpulse n This corresponds to conduction at a reference position in the negative half-cycle of the target valley, and the specific reference position can be the target valley. Furthermore, 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] Figure 6e is a schematic waveform diagram when the first primary-side power switching transistor provided in this application conducts on the left side of the target valley. In this case, m=2 x-2 Ij(m) is a positive value, and Tpulse is to the left of the reference position (target valley).

[0073] Figure 6f is a schematic waveform diagram when the first primary-side power switching transistor provided in this application conducts in the target valley. In this case, 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 schematic waveform diagram when the first primary-side power switching transistor provided in this application conducts on the right side of the target valley. In this case, 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 this application, Figure 7b is a circuit diagram of another control signal provided in this application, and Figure 7c is a schematic diagram of a function related to the second parameter provided in this application. The second embodiment is described below.

[0076] In this embodiment, the DLL (Delay-Locked Loop) principle is adopted, and Tpulse n The order relationship between the (rising edge) and the reference signal is compared, and td(m,k) is dynamically adjusted so that when m is some fixed value (the function value of the function corresponding to m is zero), Tpulse n It's being adapted for volleyball.

[0077] When Tdem is sampled and Tmid (Tdem falling edge + 0.75 * tdem) is generated 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 relative positions of the rising edge of Tpulse and the falling edge of Tmid are compared, and the range of k is set to 1-2 in accordance with the SW period. y Adjust to (where y is the value of the counter).

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

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

[0081] Ultimately, td(m,k) is dynamically adjusted after a slight period, resulting in m=1 or m=2*2 x-2 When this occurs (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 resonant period during mode switching.

[0082] m=1 or m=2*2 x-2 In this case (the function value of the periodic function corresponding to the first parameter is zero), Tpulse n This corresponds to conduction at a reference position in a negative half-cycle of the target valley, and the specific reference position may be the target valley. Moreover, since Ij(m) changes periodically, it is possible to realize conduction in the negative half-cycle region of the target valley of the primary-side power switching transistor.

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

[0084] Figure 7e is a schematic waveform diagram when the second primary-side power switching transistor provided in this application conducts in the target valley. In this case, m=1 or 2*2 x-2 Ij(m) is zero, and Tpulse is at the reference position (target valley).

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

[0086] To solve the above technical problems, the present invention further provides a control circuit for a switching power supply. Referring to Figure 8, Figure 8 is a block diagram of the configuration of the control circuit for a switching power supply provided in the present invention, and the circuit is as follows: A detection unit 81 for real-time detection of the resonant period signal of a switching power supply, By superimposing a delay time on the resonant period signal, the control signal includes a control unit 82 for controlling the conduction of the primary power switching transistor of the switching power supply within a predetermined range near the target valley of the resonant waveform, based on the resonant period signal and the delay signal. Of these, the delay time is related to the first and second parameters; the first parameter is a set value that changes over time within a certain range, and the second parameter is a function related to the resonant period of the switching power supply.

[0087] As a preferred embodiment, the control unit is: If the function value of the periodic transformation function associated with the first parameter is zero, the second parameter is adjusted to create a resonant valley matching circuit that corresponds the control signal to the center or left or right reference position of the target valley in the resonant waveform, based on the resonant period signal and the delay signal. The control signal includes a jitter frequency circuit that superimposes the function value of a periodic change function of the first parameter onto a reference position to control the conduction of the primary 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, so it will not be repeated in this application.

[0089] To solve the above technical problems, this application further provides a switching power supply including the control circuit for the switching power supply described above. A description of the switching power supply can be found in the above-described embodiment, and will not be repeated here.

[0090] It should be further explained that, in this specification, 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 order between these entities or operations. Also, the terms "encompass," "include," or any other variations of the terms cover non-exclusive inclusion, so that a process, method, article, or equipment containing a set of elements may not only include those elements, but also other elements not explicitly listed, or elements specific to that kind of process, method, article, or equipment. Unless further limitations are given, the elements limited by the phrase "containing one..." do not preclude the existence of yet another identical element within a process, method, article, or equipment containing the aforementioned element.

[0091] The above description of the published embodiments is intended to enable those skilled in the art to implement or use the present invention. Various modifications to these embodiments are obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments in circumstances that do not depart from the spirit or scope of the present invention. Therefore, the present invention is not limited to these embodiments shown herein, but is intended to conform to the broadest extent that is consistent with the principles and new features disclosed herein.

Claims

1. In a control method for a switching power supply, Real-time detection of the resonant period signal of a switching power supply, The control signal includes superimposing a delay time on the resonant period signal, thereby controlling the conduction of the primary power switching transistor of the switching power supply within a predetermined range near the target valley of the resonant waveform, based on the resonant period signal and the delay signal. The delay time is related to a first parameter and a second parameter, wherein 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. Control methods for switching power supplies.

2. The predetermined range is related to the periodic change function associated with the first parameter, By superimposing a delay time on the aforementioned resonant period signal, the control signal is made to control the conduction of the primary power switching transistor of the switching power supply within a predetermined range near the target valley of the resonant waveform, based on the aforementioned resonant period signal and the delay signal. When the function value of the periodic transformation function associated with the first parameter is zero, the second parameter is adjusted to make the control signal correspond to the center, left, or right reference position of the target valley in the resonant waveform, based on the resonant period signal and the delay signal. The control signal is characterized by superimposing the function value of the periodic change function of the first parameter onto the reference position, thereby controlling the conduction of the primary power switching transistor of the switching power supply within a predetermined range of the target valley. A method for controlling a switching power supply according to claim 1.

3. Adjusting the second parameter mentioned above To obtain the resonant period of the aforementioned resonant waveform, The method is characterized by including the following: adjusting a second parameter based on the resonance period to enable the control signal to control the conduction of the primary power switching transistor in the target valley. A method for controlling a switching power supply according to claim 2.

4. To obtain the resonant period of the aforementioned resonant waveform, Obtaining the sum of time between several consecutive valleys, consecutive peaks, or consecutive zero-crossing points in the aforementioned resonant waveform, The method is characterized by including calculating the resonance period based on the sum of the aforementioned times and the number of valleys, peaks, or zero-crossing points. A method for controlling a switching power supply according to claim 3.

5. Adjusting the second parameter mentioned above The operation parameters of the switching power supply are acquired at predetermined time intervals, The method is characterized by determining the second parameter based on the mapping relationship between the aforementioned operating parameter and the pre-set operating parameter and the second parameter, A 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, further, To determine whether or not a change has occurred in the aforementioned operating parameters, The process is characterized by including, if a change occurs, proceeding to a step of determining the second parameter based on the mapping relationship between the operation parameter and the pre-set operation parameter and the second parameter, A method for controlling a switching power supply according to claim 5.

7. To determine whether or not a change has occurred in the aforementioned operating parameters, To determine whether or not a change has occurred in the level of the aforementioned operating parameter, The features include determining that a change has occurred in the operating parameter if a change has occurred in the aforementioned level, A method for controlling a switching power supply according to claim 6.

8. The method for controlling a switching power supply according to 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. If the aforementioned operating parameters include the primary input voltage and secondary output voltage of the switching power supply, To obtain the operating parameters of the aforementioned switching power supply, When the primary power switching transistor conducts, 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. The process includes calculating 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 conducts, The auxiliary winding and the primary winding are characterized by having a common base. A method for controlling a switching power supply according to claim 8.

10. If the aforementioned operating parameter includes a load value, To obtain the operating parameters of the aforementioned switching power supply, To obtain the switching frequency of the primary power switching transistor in the switching power supply, This includes determining the load value based on the switching frequency, The load value is characterized in that it is positively correlated with the switching frequency. A method for controlling a switching power supply according to claim 8.

11. By superimposing a delay time on the aforementioned resonant period signal, the control signal is made to control the conduction of the primary power switching transistor of the switching power supply within a predetermined range near the target valley of the resonant waveform, based on the aforementioned resonant period signal and the delay signal. After determining the target valley based on the load value of the switching power supply, the zero-crossing point of the valley immediately preceding the target valley is detected. The control signal corresponding to the previous zero-crossing point is delayed by the aforementioned delay time, and the conduction time is set to this delay time, thereby causing the control signal to control the conduction of the primary-side power switching transistor at the aforementioned conduction time. A method for controlling a switching power supply according to any one of claims 1 to 10.

12. In the control circuit of a switching power supply, A detection unit for real-time detection of the resonant period signal of the switching power supply, By superimposing a delay time on the resonant period signal, the control signal includes a control unit for controlling the conduction of the primary power switching transistor of the switching power supply within a predetermined range near the target valley of the resonant waveform, based on the resonant period signal and the delay signal. The delay time is related to a first parameter and a second parameter, wherein 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. Control circuit for a switching power supply.

13. The control unit, When the function value of the periodic transformation function associated with the first parameter is zero, the second parameter is adjusted to cause the control signal to correspond to the center, left, or right reference position of the target valley in the resonant waveform, based on the resonant period signal and the delay signal, and a resonant valley correspondence circuit is provided. The control signal is characterized by superimposing the function value of the periodic change function of the first parameter onto the reference position, and including a jitter frequency circuit for controlling the conduction of the primary power switching transistor of the switching power supply within a predetermined range of the target valley. The control circuit for a switching power supply according to claim 12.

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

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