Switching power supply and control method for switching power supply

Abstract

A switching power supply and a control method for the switching power supply, belonging to the technical field of integrated circuits. A secondary-side control circuit is coupled to a secondary side of a transformer (T1) of the switching power supply; a primary-side control circuit uses the transformer (T1) to receive a feedback signal (Vfb) that reflects an output voltage of the switching power supply, decodes encoded information by means of a change of the feedback signal (Vfb), and controls the switching power supply to match the power supply requirement of a load device. The switching power supply performs transmission by means of the transformer (T1) rather than an optocoupler, so as to prevent the parameter drift of the optocoupler caused by a signal processing circuit, a technological process or an environmental change from resulting in invalid or incomplete request information received by a primary-side control chip, thereby increasing the code transmission success rate of the primary-side control circuit and saving overall system costs. In the primary-side control circuit, the transformer (T1) is used to receive the feedback signal (Vfb) and the encoded information is decoded only by means of the change of the feedback signal (Vfb) so as to match the power supply requirement of the load device, thereby simplifying decoding operation processes.

Description

A switching power supply and a control method for the switching power supply

[0001] This application claims priority to the Chinese patent application filed with the China Patent Office on July 21, 2023, with application number 202310904247.5 and invention name “A switching power supply and a control method for a switching power supply”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present invention relates to the technical field of integrated circuits, and in particular to a switching power supply and a control method for the switching power supply. Background Art

[0003] In existing fast charging solutions, the primary side control chip receives the voltage or current request information from the device to be charged (such as a mobile terminal device) through the secondary side control chip, and then adjusts the output voltage, current and other information of the switching power supply in real time through the optocoupler device to feed back the request information from the terminal device from the secondary side to the primary side.

[0004] For existing fast charging solutions, consumer electronics are produced in large quantities and are more susceptible to interference from the extreme parameters of optocoupler devices. Due to system signal processing circuit design, process problems or environmental changes, the parameters of the optocoupler devices drift, and the request information received by the primary control chip may be incomplete or even not received, resulting in invalid information and affecting the charging of the device to be charged. In addition, the addition of optocoupler devices also increases the cost of the system accordingly.

[0005] Therefore, how to save system costs and prevent the primary-side control chip from receiving incomplete information or failing to receive information is urgently needed to be solved by those skilled in the art.

[0006] Summary of the Invention

[0007] The purpose of the present invention is to provide a switching power supply and a control method for the switching power supply to solve the technical problems that the existing switching power supply increases the system cost accordingly through the use of optical coupling devices, and the information received by the primary side control chip is incomplete or cannot be received.

[0008] To solve the above technical problems, the present invention provides a switching power supply for supplying power to a load device, comprising:

[0009] a secondary side control circuit coupled to the secondary side of the transformer of the switching power supply, configured to receive a power supply demand signal of the load device and encode the power supply demand signal to generate coded information;

[0010] The primary side control circuit utilizes the transformer to receive a feedback signal reflecting the output voltage of the switching power supply, decodes the coded information according to changes in the feedback signal, and controls the switching power supply to match the power supply requirements of the load device.

[0011] Preferably, the process of determining the change of the feedback signal includes:

[0012] The primary-side control circuit receives, by means of the transformer, a width value of the feedback signal of the current control cycle corresponding to the conduction time of the secondary-side control circuit;

[0013] Acquiring a width value of the feedback signal in a previous control cycle, wherein the width value of the feedback signal in the previous control cycle is stored in the primary-side control circuit;

[0014] The change of the feedback signal is determined according to a relationship between a difference between the width values ​​of the feedback signal in the current control cycle and the previous control cycle and a threshold.

[0015] Preferably, the primary-side control circuit decodes the coded information through changes in the feedback signal, including:

[0016] When the acquired difference is greater than the threshold, the primary-side control circuit decodes the coded information sent by the secondary-side control circuit to obtain a first level signal;

[0017] When the acquired difference is less than or equal to the threshold, the primary-side control circuit decodes the coded information sent by the secondary-side control circuit to obtain a second level signal.

[0018] Preferably, the process of determining the change of the feedback signal includes:

[0019] The primary-side control circuit receives, by means of the transformer, a width value of the feedback signal of the current control cycle corresponding to the conduction time of the secondary-side control circuit;

[0020] Acquire a width value of the feedback signal of a previous control cycle, and primary currents of the current control cycle and the previous control cycle, wherein the width value of the feedback signal of the previous control cycle is stored in the primary control circuit;

[0021] The change of the feedback signal is determined according to a relationship between a width value of the feedback signal in the current control cycle and the previous control cycle and a ratio determined between the primary current in the current control cycle and the previous control cycle.

[0022] Preferably, the primary-side control circuit decodes the coded information through changes in the feedback signal, including:

[0023] When the ratio corresponding to the current control period obtained is smaller than the ratio corresponding to the previous control period, the primary-side control circuit decodes the coded information sent by the secondary-side control circuit to obtain a first level signal;

[0024] When the primary-side control circuit obtains that the ratio corresponding to the current control period is equal to the ratio corresponding to the previous control period, the primary-side control circuit decodes the coded information sent by the secondary-side control circuit to obtain a second level signal.

[0025] Preferably, the secondary side control circuit includes a synchronous rectifier diode, and the process of determining the coded information includes:

[0026] The secondary-side control circuit controls the synchronous rectifier diode to delay turning off for a preset time when receiving the power supply requirement signal of the load device, and encodes the power supply requirement signal to obtain the encoding information.

[0027] Preferably, the secondary side control circuit includes a synchronous rectifier diode, and the process of determining the coded information includes:

[0028] When receiving the power supply requirement signal of the load device, the secondary side control circuit encodes the power supply requirement signal to obtain the coding information within the secondary conduction time after controlling the synchronous rectifier diode to be turned off.

[0029] Preferably, the secondary side control circuit includes a secondary side detection circuit, and the process of determining the secondary conduction time of the synchronous rectifier diode includes:

[0030] The secondary side detection circuit is used to detect the moment when the output voltage signal of the secondary side control circuit changes from a low-level signal state, and rises to a high-level signal state, and controls the time interval from the second conduction of the synchronous rectifier diode to the low-level state as the secondary conduction time.

[0031] Preferably, the primary-side control circuit includes a primary-side detection circuit, and the process of determining the change of the feedback signal includes:

[0032] The primary side detection circuit is used to detect that the feedback signal drops and is lower than a reference value, and obtain the relationship between the current feedback signal and the reference value within a specified time to determine the change of the current feedback signal.

[0033] Preferably, the primary-side control circuit decodes the coded information through changes in the feedback signal, including:

[0034] When the primary-side control circuit obtains that the current feedback signal exceeds the reference value again within the specified time, the primary-side control circuit decodes the coded information sent by the secondary-side control circuit to obtain a first level signal;

[0035] When the primary-side control circuit does not obtain that the current feedback signal exceeds the reference value again within the specified time, the primary-side control circuit decodes the coded information sent by the secondary-side control circuit to obtain a second level signal.

[0036] Preferably, the secondary side control circuit and the primary side control circuit respectively utilize a multiplexed PIN pin and change the resistance value of the resistor connected to the multiplexed PIN pin to determine the specified time, wherein there is a mapping relationship between the change in the resistance value of the resistor connected to the multiplexed PIN pin and the change in the specified time.

[0037] Preferably, the secondary side control circuit further includes a voltage detection circuit;

[0038] The voltage detection circuit is used to obtain a corresponding voltage value change according to the current value of the VCC PIN pin of the secondary side control circuit, wherein the voltage value change is used to represent the resistance value change of the resistor.

[0039] To solve the above technical problems, the present invention further provides a control method for a switching power supply, wherein the switching power supply is used to supply power to a load device, and comprises a secondary side control circuit and a primary side control circuit, wherein the secondary side control circuit is coupled to the secondary side of a transformer of the switching power supply;

[0040] Controlling the secondary side control circuit to receive the power supply demand signal of the load device and encode the power supply demand signal to generate coded information;

[0041] The primary side control circuit is controlled to utilize the transformer to receive a feedback signal reflecting the output voltage of the switching power supply, decode the coded information according to the change of the feedback signal, and control the switching power supply to match the power supply requirement of the load device.

[0042] Preferably, the process of determining the change of the feedback signal includes:

[0043] Utilizing the transformer to receive a width value of the feedback signal of the current control cycle corresponding to the conduction time of the secondary side control circuit;

[0044] Acquiring a width value of the feedback signal in a previous control cycle, wherein the width value of the feedback signal in the previous control cycle is stored in the primary-side control circuit;

[0045] The change of the feedback signal is determined according to a relationship between a difference between the width values ​​of the feedback signal in the current control cycle and the previous control cycle and a threshold.

[0046] Preferably, decoding the encoded information by using the change of the feedback signal includes:

[0047] When the acquired difference is greater than the threshold, decoding the coded information sent by the secondary-side control circuit to obtain a first level signal;

[0048] When the acquired difference is less than or equal to the threshold, the coded information sent by the secondary-side control circuit is decoded to obtain a second level signal.

[0049] Preferably, the process of determining the change of the feedback signal includes:

[0050] Utilizing the transformer to receive a width value of the feedback signal of the current control cycle corresponding to the conduction time of the secondary side control circuit;

[0051] Acquire a width value of the feedback signal of a previous control cycle, and primary currents of the current control cycle and the previous control cycle, wherein the width value of the feedback signal of the previous control cycle is stored in the primary control circuit;

[0052] The change of the feedback signal is determined according to a relationship between a width value of the feedback signal in the current control cycle and the previous control cycle and a ratio determined between the primary current in the current control cycle and the previous control cycle.

[0053] Preferably, decoding the encoded information by using the change of the feedback signal includes:

[0054] When the obtained ratio corresponding to the current control cycle is smaller than the ratio corresponding to the previous control cycle, decoding the coded information sent by the secondary-side control circuit to obtain a first level signal;

[0055] When it is obtained that the ratio corresponding to the current control cycle is equal to the ratio corresponding to the previous control cycle, the coded information sent by the secondary side control circuit is decoded to obtain a second level signal.

[0056] Preferably, the secondary side control circuit includes a synchronous rectifier diode, and the process of determining the coded information includes:

[0057] When receiving the power supply requirement signal of the load device, the synchronous rectifier diode is controlled to be turned off with a delay of a preset time, and the power supply requirement signal is encoded to obtain the encoding information.

[0058] Preferably, the secondary side control circuit includes a synchronous rectifier diode, and the process of determining the coded information includes:

[0059] During the secondary conduction time after the synchronous rectifier diode is controlled to be turned off when receiving the power supply demand signal of the load device, the power supply demand signal is encoded to obtain the encoding information.

[0060] Preferably, the secondary side control circuit includes a secondary side detection circuit, and the process of determining the secondary conduction time of the synchronous rectifier diode includes:

[0061] The secondary conduction time is determined based on the detection of the moment when the output voltage signal of the secondary control circuit changes from a low-level signal state to a high-level signal state, and the time interval from the moment when the synchronous rectifier diode is controlled to fall to the low-level state after the secondary conduction is controlled is used as the secondary conduction time.

[0062] Preferably, the primary-side control circuit includes a primary-side detection circuit, and the process of determining the change of the feedback signal includes:

[0063] It is detected that, starting from the moment when the feedback signal drops and is lower than the reference value, a relationship between the current feedback signal and the reference value is obtained within a specified time to determine a change in the current feedback signal.

[0064] Preferably, decoding the encoded information by using the change of the feedback signal includes:

[0065] When it is obtained that the current feedback signal exceeds the reference value again within the specified time, decoding the coded information sent by the secondary-side control circuit to obtain a first level signal;

[0066] When the current feedback signal is not obtained to exceed the reference value again within the specified time, the coded information sent by the secondary-side control circuit is decoded to obtain a second level signal.

[0067] Preferably, the specified time is determined by changing the resistance value of the resistor connected to the multiplexed PIN pin corresponding to the secondary side control circuit and the primary side control circuit, wherein there is a mapping relationship between the change in the resistance value of the resistor connected to the multiplexed PIN pin and the change in the specified time.

[0068] Preferably, the secondary side control circuit further includes a voltage detection circuit;

[0069] A corresponding voltage value change is obtained by detecting the current value of the VCC PIN pin of the secondary side control circuit, wherein the voltage value change is used to represent the resistance value change of the resistor.

[0070] Preferably, after receiving the feedback signal by using the transformer, the method further includes:

[0071] Presetting the start bit and end check bit corresponding to the coded information;

[0072] The decoded information is obtained by decoding the encoded information through the change of the feedback signal, the start bit and the end check bit.

[0073] The present invention provides a switching power supply for supplying power to a load device, comprising: a secondary-side control circuit coupled to the secondary side of a transformer of the switching power supply, configured to receive a power demand signal from the load device and encode the power demand signal to generate coded information; and a primary-side control circuit, configured to utilize the transformer to receive a feedback signal reflecting the output voltage of the switching power supply, decode the coded information based on changes in the feedback signal, and control the switching power supply to match the power demand of the load device. The switching power supply is transmitted via the transformer, eliminating the need for an optocoupler device. This avoids parameter drift of the optocoupler device due to changes in the signal processing circuit, process, or environment, which could render the request information received by the primary-side control chip invalid or incomplete. This improves the primary-side control circuit's code transmission success rate and reduces overall system cost. Furthermore, within the primary-side control circuit, the transformer is used to receive the feedback signal, and the coded information is decoded solely based on changes in the feedback signal to match the power demand of the load device, simplifying the decoding process.

[0074] In addition, the present invention also provides a control method for a switching power supply, which has the same beneficial effects as the above-mentioned switching power supply. BRIEF DESCRIPTION OF THE DRAWINGS

[0075] In order to more clearly illustrate the embodiments of the present invention, the following is a brief introduction to the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0076] FIG1 is a schematic diagram of the structure of an existing switching power supply;

[0077] FIG2 is a schematic structural diagram of a switching power supply provided by an embodiment of the present invention;

[0078] FIG3 is a schematic diagram showing a change in the ratio of an on-time to a peak current signal provided by an embodiment of the present invention;

[0079] FIG4 is a schematic diagram showing another change in the ratio of the on-time to the peak current signal provided by an embodiment of the present invention;

[0080] FIG5 is a schematic diagram of voltage rise information detection of a feedback signal provided by the present invention;

[0081] FIG6 is a flow chart of a method for controlling a switching power supply provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0082] The following will provide a clear and complete description of the technical solutions in the embodiments of the present invention, with reference to the accompanying drawings. It should be understood that the described embodiments are merely some, and not all, of the embodiments of the present invention. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort are intended to fall within the scope of protection of the present invention.

[0083] The core of the present invention is to provide a switching power supply and a control method for the switching power supply to solve the technical problems that the existing switching power supply increases the system cost accordingly through the use of optocoupler devices, and the information received by the primary side control chip is incomplete or cannot be received.

[0084] In order to enable those skilled in the art to better understand the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific implementation methods.

[0085] It should be noted that Figure 1 is a structural diagram of an existing switching power supply, which uses an optocoupler device U2. It is extremely susceptible to factors such as temperature. If the limit parameters of the optocoupler device U2 are exceeded, the request information received by the primary side control chip U1 may be incomplete or even not received.

[0086] FIG2 is a schematic diagram of the structure of a switching power supply provided by an embodiment of the present invention. As shown in FIG2 , the switching power supply is used to supply power to a load device. The secondary-side control circuit is coupled to the secondary side of the transformer of the switching power supply and is used to receive a power demand signal from the load device and encode the power demand signal to generate coded information.

[0087] The primary side control circuit uses a transformer to receive the feedback signal reflecting the output voltage of the switching power supply, decodes the encoded information through the changes in the feedback signal, and controls the switching power supply to match the power supply requirements of the load equipment.

[0088] It should be noted that Figure 2 is only an embodiment of a switching power supply, used to illustrate the working principle between the secondary control circuit and the primary control circuit of the switching power supply of the present invention. It can also be a structural diagram of other switching power supplies, as long as the switching power supply uses a transformer instead of an optocoupler device for signal transmission. The switching power supply includes a secondary control circuit and a primary control circuit. As shown in Figure 2, the switching power supply includes a filter, a rectifier bridge BD1, input capacitors C1 and C2, a control chip U5 for the primary control circuit, a primary current sampling resistor R1 (including R1A, R1B, and R1C), a secondary synchronous rectifier diode Q2, a control chip U6 for the secondary control circuit, a USB interface, a transformer T1 (including a primary winding Np, a secondary winding Ns, and an auxiliary winding Na), and an output capacitor C21.

[0089] The primary-side control circuit's control chip U5 is located on the primary side of the switching power supply's transformer. It controls the on / off switching of the first power switch Q1 and transfers energy to the secondary-side control circuit's control chip U6 via transformer T1. The secondary-side control circuit's control chip U6 is connected to a load device, and the secondary-side control circuit is coupled to the secondary side of the switching power supply's transformer. The secondary-side control circuit receives a power demand signal from the load device. There are no specific requirements for when the power demand signal is acquired or triggered. The load device can proactively provide the power demand signal, or the secondary-side control circuit can receive a signal from the load device in real time. If the current signal differs from the previous cycle's signal, or if a specific level signal is received, it is determined to be a power demand signal. This power demand signal is encoded within the secondary-side control circuit to generate coded information.

[0090] After the coded information is generated within the secondary control circuit, it is transmitted to the primary control circuit via the transformer. The primary control circuit then receives the coded information via the transformer. The voltage across transformer T1's auxiliary winding Na is fed through resistor R7 to produce a feedback signal, Vfb. This output feedback signal represents the output voltage of the switching power supply and serves as a feedback control signal. This signal is then fed into the primary control circuit via the FB pin for control. This embodiment decodes the coded information based on changes in the feedback signal to control the switching power supply to match the power requirements of the load device.

[0091] It can be understood that in this embodiment, the decoding of the encoded information can be completed only through the signal parameters of a feedback signal. Compared with the existing primary side control circuit of the switching power supply, which needs to be set to generate a corresponding detection signal under a specific scenario to decode the encoded information, this embodiment does not need to limit the specific scenario. As long as the feedback signal changes, the encoded information can be decoded according to the feedback signal itself, so as to save and simplify the decoding procedure.

[0092] The corresponding parameter for the change of the feedback signal can be the width value of the feedback signal itself or the change of the feedback signal caused by the width value of the feedback signal and other related parameters. The first two types only cause the feedback signal to change during decoding. The feedback signal can also be changed in combination with the secondary side control circuit corresponding to the encoding and the primary side control circuit corresponding to the decoding. There is no limitation here and it can be set according to actual conditions.

[0093] A switching power supply provided by an embodiment of the present invention is used to supply power to a load device. The switching power supply includes: a secondary-side control circuit coupled to the secondary side of a transformer of the switching power supply, configured to receive a power demand signal from the load device and encode the power demand signal to generate coded information; and a primary-side control circuit, configured to utilize the transformer to receive a feedback signal reflecting the output voltage of the switching power supply, decode the coded information based on changes in the feedback signal, and control the switching power supply to match the power demand of the load device. The switching power supply is transmitted through the transformer without the need for an optocoupler, thus avoiding the situation where parameter drift of the optocoupler due to changes in the signal processing circuit, process, or environment could render the request information received by the primary-side control chip invalid or incomplete. This improves the transmission success rate of the primary-side control circuit and reduces the cost of the entire system. Furthermore, within the primary-side control circuit, the transformer is used to receive the feedback signal, and the coded information is decoded solely based on changes in the feedback signal to match the power demand of the load device, simplifying the decoding process.

[0094] Based on the above embodiment, as an embodiment, in a primary-side control circuit corresponding to decoding, a process of changing a feedback signal determined based on the feedback signal itself includes:

[0095] The primary side control circuit uses a transformer to receive the width value of the feedback signal of the current control cycle corresponding to the conduction time of the secondary side control circuit;

[0096] Obtaining a width value of a feedback signal of a previous control cycle, wherein the width value of the feedback signal of the previous control cycle is stored in a primary-side control circuit;

[0097] The change of the feedback signal is determined according to the relationship between the difference between the width values ​​of the feedback signal in the current control cycle and the previous control cycle and the threshold.

[0098] Specifically, the primary control circuit uses a transformer to receive the width value of the feedback signal of the current control cycle corresponding to the conduction time of the secondary control circuit, and obtains the width value of the feedback signal of the previous control cycle. The width value of the feedback signal of the previous control cycle is stored in the primary control circuit. As long as the width value of the feedback signal of a control cycle is received, it will be stored in the primary control circuit. In addition, considering that the storage space of the primary control circuit is limited, the feedback signals of each control cycle can be stored in a rolling manner. For example, only the signal parameters of the feedback signals of the first N control cycles including the current latest control cycle are stored. There is no limitation here and it can be set according to actual conditions.

[0099] The widths of the feedback signals between two adjacent control cycles are compared to determine their difference. Whether this difference is positive or negative is not specified; as long as there is a corresponding difference between the widths of the feedback signals between two adjacent control cycles, it is sufficient. It should be noted that since the difference was previously expressed as a negative or positive value, it is converted to an absolute value here. The relationship between this difference and a threshold is then determined to determine changes in the feedback signal.

[0100] Based on the above embodiment, as an embodiment, the primary-side control circuit decodes the encoded information through changes in the feedback signal, including:

[0101] When the acquired difference is greater than the threshold, the primary-side control circuit decodes the coded information sent by the secondary-side control circuit to obtain a first level signal;

[0102] When the acquired difference is less than or equal to the threshold, the primary-side control circuit decodes the coded information sent by the secondary-side control circuit to obtain a second level signal.

[0103] Specifically, the primary-side control circuit determines whether the difference is greater than a threshold value. If so, the coded information sent by the secondary-side control circuit is decoded to obtain a first level signal. If the difference is less than or equal to the threshold value, the coded information sent by the secondary-side control circuit is decoded to obtain a second level signal. The first level signal is different from the second level signal.

[0104] Figure 3 is a schematic diagram of a change in the ratio of the on-time to the peak current signal provided by an embodiment of the present invention, and Figure 4 is a schematic diagram of another change in the ratio of the on-time to the peak current signal provided by an embodiment of the present invention. Figure 3 represents a light load condition, and Figure 4 represents a heavy load condition. As shown in Figures 3 and 4, the black solid line represents the working waveform of the signal under normal working conditions, and the gray solid line represents the working waveform of the signal after the secondary side control circuit sends the coded information. From top to bottom, in the waveform diagram, the first is the waveform diagram of the feedback signal of the primary side control circuit, the second is the signal waveform diagram of the secondary side control circuit, the third is the pulse width modulation (PWM) signal waveform diagram of the switching power supply, and the fourth is the signal diagram of the switching power supply.

[0105] Under normal working conditions, the on-time of the width value Tons of the feedback signal is a constant value ΔT1, and the secondary side synchronous rectification controller delays the shutdown ΔT ds (ΔT ds =ΔT2-ΔT1), which will cause the on-time to change from the on-time ΔT1 of the previous control cycle to the on-time ΔT2 of the current control cycle. By comparing the difference between the on-time of the current cycle and the on-time of the previous control cycle, the difference is compared with the threshold. If the detected difference is greater than the threshold, it is considered that the secondary side has sent a logic high level to the primary side. If the detected difference is less than or equal to the threshold, it is considered that the secondary side has sent a logic low level to the primary side.

[0106] The threshold can be set based on empirical values ​​or obtained through extensive experimentation. However, the threshold has upper and lower limits. The minimum value must be sufficient to prevent the primary control circuit from misinterpreting it as a coding signal under normal system fluctuations, and the maximum value must be sufficient to not affect the normal operation of the system. As long as these two conditions are met, the system is sufficient.

[0107] The embodiment of the present invention provides a method for determining the change of the feedback signal based on the relationship between the width value of the feedback signal and the threshold value in two adjacent control cycles. The change of the feedback signal is determined only by the width value of the feedback signal, thereby improving the decoding rate and simplifying the decoding procedure.

[0108] Based on the above embodiment, as an embodiment, in a primary-side control circuit corresponding to decoding, a process in which the width value of the feedback signal and the feedback signal determined by other relevant parameters change includes:

[0109] The primary side control circuit uses a transformer to receive the width value of the feedback signal of the current control cycle corresponding to the conduction time of the secondary side control circuit;

[0110] Obtaining a width value of a feedback signal of a previous control cycle, and primary currents of a current control cycle and a previous control cycle, wherein the width value of the feedback signal of the previous control cycle is stored in the primary control circuit;

[0111] The change of the feedback signal is determined according to the relationship between the width value of the feedback signal of the current control cycle and the previous control cycle and the ratio determined by the primary current of the current control cycle and the previous control cycle.

[0112] Specifically, the primary control circuit utilizes a transformer to receive the width of the feedback signal of the current control cycle corresponding to the conduction time of the secondary control circuit, and simultaneously obtains the stored width of the feedback signal of the previous control cycle, as well as the primary currents of the current control cycle and the previous cycle. The primary current in this embodiment is the peak current signal in the primary control circuit. Under normal circumstances, the ratio of the width of the feedback signal corresponding to the conduction time to the primary current is a constant. When the secondary synchronous rectification controller sends codeword information, the width of the feedback signal corresponding to the conduction time becomes longer.

[0113] The change in the feedback signal is determined by the change in the ratio of the feedback signal width to the primary current between two adjacent control cycles. If the ratio of the feedback signal width to the primary current in the current control cycle is the same as the ratio of the feedback signal width to the primary current in the previous control cycle, it indicates that the feedback signal has not changed. If they are different, it indicates that the feedback signal has changed.

[0114] As an embodiment, the primary-side control circuit decodes the encoded information through changes in the feedback signal, including:

[0115] When the ratio corresponding to the current control cycle obtained is smaller than the ratio corresponding to the previous control cycle, the primary side control circuit decodes the coded information sent by the secondary side control circuit to obtain a first level signal;

[0116] When the primary-side control circuit obtains that the ratio corresponding to the current control cycle is equal to the ratio corresponding to the previous control cycle, the primary-side control circuit decodes the coded information sent by the secondary-side control circuit to obtain a second level signal.

[0117] Specifically, when the primary-side control circuit obtains that the ratio corresponding to the current control cycle is less than the ratio corresponding to the previous control cycle, it indicates that the ratio of the current control cycle has decreased, and its on-time has been extended. The coded information sent by the secondary-side control circuit is decoded to obtain a first level signal, confirming that the secondary side has sent codeword information. When the primary-side control circuit obtains that the ratio corresponding to the current control cycle is equal to the ratio corresponding to the previous control cycle, the coded information sent by the secondary-side control circuit is decoded to obtain a second level signal. The ratio remains unchanged, and the second level signal is used to mark that the first level signal and the second level signal are different.

[0118] The ratio of the feedback signal width to the primary current is as follows:

[0119] Among them, I pk is the primary current, T ons is the width of the feedback signal, n is the number of turns of the transformer, V out is the output voltage of the primary control circuit, and L is the inductance value of the primary control circuit.

[0120] Normally, the parameter on the right side of the above relationship does not change and is a constant. If the ratio of the width of the feedback signal to the primary current decreases to a certain extent, for example, reaches a ratio threshold, it indicates that the secondary control circuit is sending coded information to the primary control circuit.

[0121] The embodiment of the present invention provides that the feedback signal determined by the ratio of the width value of the feedback signal to the primary current changes, so that the change of the feedback signal is authoritative, the decoding rate is improved, and the decoding procedure is simplified.

[0122] Based on the above embodiment, as an embodiment, the secondary side control circuit includes a synchronous rectifier diode, and the process of determining the coded information includes:

[0123] The secondary side control circuit controls the synchronous rectifier diode to delay turning off for a preset time when receiving the power supply demand signal of the load device, and encodes the power supply demand signal to obtain coded information.

[0124] Specifically, as shown in Figure 2, a synchronous rectifier diode Q2 is connected in parallel with capacitor C22 and resistor R22. Upon receiving a power demand signal from a load device, the secondary-side control circuit controls the synchronous rectifier diode to delay its off-state for a preset time. In the above embodiment, changes in the feedback signal are reflected during decoding. However, in the secondary-side control circuit, the power demand signal is encoded to obtain coded information by controlling the delayed off-state of the synchronous rectifier diode. Simultaneously, the delayed off-state of the synchronous rectifier diode causes changes in the on-time of the feedback signal, which in turn causes changes in the feedback signal. In this embodiment, the coded information is decoded based on changes in the feedback signal to match the power demand of the load device.

[0125] It should be noted that the preset time can be 0 or a time greater than 0. If it is 0, it is determined that the synchronous rectifier diode is not currently controlled to delay shutdown. There is no limitation on the setting of the preset time, and the specific preset time data can be determined according to actual conditions.

[0126] The embodiment of the present invention provides a method for determining the change of the feedback signal in decoding of the primary-side control circuit. It is necessary to control the synchronous rectifier diode in the secondary-side control circuit to delay turning off to receive the corresponding coded information, so as to realize decoding of the coded information.

[0127] In the above embodiment, the change of the feedback signal is determined only during decoding of the primary-side control circuit. As another embodiment, in a combination of a secondary-side control circuit corresponding to encoding and a primary-side control circuit corresponding to decoding, the secondary-side control circuit includes a synchronous rectifier diode, and the process of determining the encoding information includes:

[0128] When receiving the power supply demand signal of the load device, the secondary side control circuit encodes the power supply demand signal to obtain coded information within the secondary conduction time after controlling the synchronous rectifier diode to be turned off.

[0129] Specifically, when the secondary control circuit receives the power demand signal of the load device, it controls the secondary conduction time after the synchronous rectifier diode is turned off, and encodes the power demand signal to obtain coded information. In the case of an abnormal shutdown state, the synchronous rectifier diode will be turned on for a period of time after being turned off. Between the two conduction time intervals, the feedback signal reflected in the primary control circuit will cause a pit to appear in the waveform of the feedback signal. In the above embodiment, the synchronous rectifier diode of the secondary control circuit is in a normal shutdown state. In other cases of abnormal shutdown state, the secondary conduction time must also be considered. Therefore, this embodiment is based on the coded information determined in the abnormal shutdown situation.

[0130] The secondary side control circuit provided in the embodiment of the present invention determines the coded information by controlling the secondary conduction time after the synchronous rectifier diode is turned off. This takes into account different aspects, so that the obtained coded information is more comprehensive, facilitating the subsequent decoding process.

[0131] Based on the above embodiment, as an embodiment, the secondary-side control circuit includes a secondary-side detection circuit, and the process of determining the secondary-side conduction time of the synchronous rectifier diode includes:

[0132] The secondary side detection circuit is used to detect the moment when the output voltage signal of the secondary side control circuit changes from a low-level signal state, and starts timing from rising to a high-level signal state, and controls the time interval from the synchronous rectifier diode falling to a low-level state after the secondary conduction as the secondary conduction time.

[0133] Figure 5 is a schematic diagram of a feedback signal voltage rise detection method provided by the present invention. As shown in the second waveform diagram of Figure 5, the secondary-side detection circuit detects the moment when the output voltage signal of the secondary-side control circuit changes from a low-level state, that is, gradually changes to a high-level state. The timing starts when the signal rises to the high-level signal state, and the time interval corresponding to the time when the synchronous rectifier diode falls to a low-level state after the secondary conduction is controlled as the secondary conduction time, which is the conduction time t2-t3 in the figure. This is mapped to the third PWM diagram, which is the PWM box after the pit appears after the abnormal shutdown.

[0134] The vertical axis in the first waveform diagram in Figure 5 is Among them, N a is the auxiliary winding on the primary side of the transformer in Figure 2, N S It is the secondary winding on the secondary side of the transformer in Figure 2.

[0135] Accordingly, as an embodiment, in the primary detection circuit, the process of determining the change of the feedback signal of the primary control circuit includes:

[0136] The primary side detection circuit is used to detect the moment when the feedback signal drops and is lower than the reference value, and obtain the relationship between the current feedback signal and the reference value within a specified time to determine the change of the current feedback signal.

[0137] Combined with the waveform diagram of the feedback signal of the first primary side control circuit in Figure 5, starting from the moment when the feedback signal is detected to drop and is lower than the reference value, the relationship between the current feedback signal and the reference value is obtained within a specified time to determine the change of the current feedback signal.

[0138] Specifically, the relationship between the current feedback signal and the reference value is tracked in real time. The specific relationship is not limited. For example, if the current feedback signal remains below the reference value, the current feedback signal remains unchanged. If the current feedback signal changes to a high level again and exceeds the reference value, it indicates that a higher signal appears during the secondary on-time of the current delayed shutdown, indicating that the secondary control circuit has transmitted coded information to the primary control circuit. The reference value in Figure 5 is 0, but it can also be other values. In this embodiment, the reference value of 0 allows for a more intuitive display of the waveform changes.

[0139] As an embodiment, the primary-side control circuit decodes the encoded information through changes in the feedback signal, including:

[0140] When the primary side control circuit obtains that the current feedback signal exceeds the reference value again within the specified time, the primary side control circuit decodes the coded information sent by the secondary side control circuit to obtain a first level signal;

[0141] When the primary-side control circuit does not obtain that the current feedback signal exceeds the reference value again within the specified time, the coding information sent by the secondary-side control circuit is decoded to obtain a second level signal.

[0142] Specifically, when the primary side control circuit obtains that the current feedback signal exceeds the reference value again within the specified time, the coded information sent by the secondary side control circuit is decoded to obtain a first level signal; when the current feedback signal does not exceed the reference value again within the specified time, the coded information sent by the secondary side control circuit is decoded to obtain a second level signal.

[0143] For example, the timing starts at t1 when the secondary chip detects Vdet transitioning from the negative half-axis to the positive half-axis. After T1 (T1 = t2 - t1), the voltage is turned on at t2 for 200ns (approximately 35ns at high voltage) and ends at t3. Taking the primary chip as an example, t1 is the moment when the voltage starts to decrease from a high level, t2 is the moment when the feedback signal intersects the voltage rise information, and t3 is the moment when the voltage rise information reaches its peak after the delayed shutdown.

[0144] The action logic of the primary side control chip detects the moment when the feedback signal goes from a high level below the feedback signal threshold, and determines whether the voltage rise information of the feedback signal will exceed the feedback signal threshold again within a specified time. If so, it means that the secondary side has transmitted a logic high level signal to the primary side. If not, it means a logic low level signal.

[0145] It should be noted that the calculation formula for the specified time is:

[0146] Among them, L p is the inductance of the primary control circuit, C oss is the capacitance value of the parasitic capacitance of the synchronous rectifier diode.

[0147] As an embodiment, for changes in the specified time, the secondary side control circuit and the primary side control circuit respectively utilize the multiplexed PIN pin and change the resistance value of the resistor connected to the multiplexed PIN pin to determine the specified time, wherein there is a mapping relationship between the change in the resistance value of the resistor connected to the multiplexed PIN pin and the change in the specified time.

[0148] Specifically, this is achieved by configuring the secondary-side control circuit and the primary-side control circuit to utilize a multiplexed PIN pin, respectively, and then changing the resistance of the resistor connected to that multiplexed PIN pin. Referring to Figure 2 , the resistance of the Vdet pin changes over time, T2, to adapt to different systems. To determine how the resistance change changes over time, a functional mapping relationship between the resistance change and the length of the change over a specified time period can be established within the respective control circuit chips. This functional mapping relationship is not limited in this embodiment; existing functional relationships can be used, or custom functional relationships can be constructed, depending on the actual situation.

[0149] In addition, in the secondary side control circuit, for the change in the specified time, as an embodiment, the secondary side control circuit further includes a voltage detection circuit;

[0150] The voltage detection circuit is used to obtain a corresponding voltage value change according to the current value of the VCC PIN pin of the secondary side control circuit, wherein the voltage value change is used to represent the resistance value change of the resistor.

[0151] Specifically, by changing the current value of the VCC PIN pin of the secondary side control circuit and charging a fixed capacitor with the current, different voltage values ​​will be obtained to achieve voltage value changes. The voltage value change can represent the resistance change of the resistor.

[0152] The embodiment of the present invention provides a method for determining a change in the feedback signal corresponding to a change in the secondary conduction, thereby increasing the flexibility of the detection method and improving the accuracy of the detection.

[0153] FIG6 is a flow chart of a method for controlling a switching power supply according to an embodiment of the present invention. As shown in FIG6 , the method is applied to a switching power supply, wherein the switching power supply is used to supply power to a load device and includes a secondary-side control circuit and a primary-side control circuit. The secondary-side control circuit is coupled to the secondary side of a transformer of the switching power supply.

[0154] S11: Control the secondary side control circuit to receive the power supply demand signal of the load device and encode the power supply demand signal to generate coded information;

[0155] S12: Control the primary side control circuit, use the transformer to receive the feedback signal reflecting the output voltage of the switching power supply, decode the encoded information through the change of the feedback signal, and control the switching power supply to match the power supply demand of the load device.

[0156] Specifically, the secondary-side control circuit receives a power demand signal from a load device and encodes it to generate coded information. The encoding algorithm is not specified here and can be selected based on actual circumstances. The primary-side control circuit utilizes a transformer to receive a feedback signal reflecting the output voltage of the switching power supply. The coded information is decoded solely based on changes in the feedback signal to control the switching power supply to match the power supply requirements of the load device.

[0157] An embodiment of the present invention provides a control method for a switching power supply, which is used to supply power to a load device. The method includes a secondary control circuit and a primary control circuit. The secondary control circuit is coupled to the secondary side of a transformer of the switching power supply, controls the secondary control circuit to receive a power demand signal from the load device, and encodes the power demand signal to generate coded information. The primary control circuit is controlled to receive a feedback signal reflecting the output voltage of the switching power supply via the transformer, decode the coded information based on changes in the feedback signal, and control the switching power supply to match the power demand of the load device. The switching power supply control method utilizes a transformer for transmission, eliminating the need for an optocoupler device. This avoids parameter drift of the optocoupler device due to changes in the signal processing circuit, process, or environment, which could result in invalid or incomplete request information received by the primary control chip. This improves the success rate of code transmission in the primary control circuit and reduces overall system cost. Furthermore, within the primary control circuit, the transformer is used to receive the feedback signal, and the coded information is decoded solely based on changes in the feedback signal to match the power demand of the load device, simplifying the decoding process.

[0158] Based on the above embodiment, as an embodiment, the process of determining the change of the feedback signal includes:

[0159] The transformer is used to receive the width value of the feedback signal of the current control cycle corresponding to the conduction time of the secondary side control circuit;

[0160] Obtaining a width value of a feedback signal of a previous control cycle, wherein the width value of the feedback signal of the previous control cycle is stored in a primary-side control circuit;

[0161] The change of the feedback signal is determined according to the relationship between the difference between the width values ​​of the feedback signal in the current control cycle and the previous control cycle and the threshold.

[0162] As an embodiment, decoding the encoded information by using a change in the feedback signal includes:

[0163] When the acquired difference is greater than the threshold, decoding the coded information sent by the secondary side control circuit to obtain a first level signal;

[0164] When the acquired difference is less than or equal to the threshold, the coded information sent by the secondary-side control circuit is decoded to obtain a second level signal.

[0165] As an embodiment, the process of determining the change of the feedback signal includes:

[0166] The transformer is used to receive the width value of the feedback signal of the current control cycle corresponding to the conduction time of the secondary side control circuit;

[0167] Obtaining a width value of a feedback signal of a previous control cycle, and primary currents of a current control cycle and a previous control cycle, wherein the width value of the feedback signal of the previous control cycle is stored in the primary control circuit;

[0168] The change of the feedback signal is determined according to the relationship between the width value of the feedback signal of the current control cycle and the previous control cycle and the ratio determined by the primary current of the current control cycle and the previous control cycle.

[0169] As an embodiment, decoding the encoded information by using a change in the feedback signal includes:

[0170] When the ratio corresponding to the current control cycle is smaller than the ratio corresponding to the previous control cycle, decoding the coded information sent by the secondary side control circuit to obtain a first level signal;

[0171] When it is obtained that the ratio corresponding to the current control cycle is equal to the ratio corresponding to the previous control cycle, the coded information sent by the secondary side control circuit is decoded to obtain a second level signal.

[0172] In one embodiment, the secondary side control circuit includes a synchronous rectifier diode, and the process of determining the coded information includes:

[0173] When receiving a power supply demand signal from a load device, the synchronous rectifier diode is controlled to be turned off with a delay of a preset time, and the power supply demand signal is encoded to obtain encoding information.

[0174] In one embodiment, the secondary side control circuit includes a synchronous rectifier diode, and the process of determining the coded information includes:

[0175] When receiving the power supply demand signal of the load device, during the secondary conduction time after the synchronous rectifier diode is controlled to be turned off, the power supply demand signal is encoded to obtain encoding information.

[0176] As an embodiment, the secondary side control circuit includes a secondary side detection circuit, and the process of determining the secondary conduction time of the synchronous rectifier diode includes:

[0177] The secondary conduction time is the time interval from the moment when the output voltage signal of the secondary side control circuit changes from a low level signal state to a high level signal state. The time interval from the moment when the synchronous rectifier diode is controlled to fall to a low level state after the secondary conduction is controlled is used as the secondary conduction time.

[0178] As an embodiment, the primary-side control circuit includes a primary-side detection circuit, and the process of determining the change of the feedback signal includes:

[0179] Starting from the moment when the self-feedback signal drops and is lower than the reference value, the relationship between the current feedback signal and the reference value is obtained within a specified time to determine the change of the current feedback signal.

[0180] As an embodiment, decoding the encoded information by using a change in the feedback signal includes:

[0181] When the current feedback signal is obtained to exceed the reference value again within the specified time, the coded information sent by the secondary side control circuit is decoded to obtain a first level signal;

[0182] When the current feedback signal is not obtained to exceed the reference value again within the specified time, the coded information sent by the secondary side control circuit is decoded to obtain a second level signal.

[0183] As an embodiment, the specified time is determined by changing the resistance value of the resistor connected to the multiplexed PIN pin corresponding to the secondary side control circuit and the primary side control circuit, wherein there is a mapping relationship between the change in the resistance value of the resistor connected to the multiplexed PIN pin and the change in the specified time.

[0184] As an embodiment, the secondary side control circuit further includes a voltage detection circuit;

[0185] The corresponding voltage change is obtained by detecting the current value of the VCC PIN pin of the secondary side control circuit, wherein the voltage change is used to represent the resistance change of the resistor.

[0186] The control method of the switching power supply in the above embodiment corresponds to the embodiment of the switching power supply, which will not be described in detail here, and reference may be made to the above corresponding embodiment.

[0187] As an embodiment, after receiving the feedback signal by using the transformer, the method further includes:

[0188] Pre-set the start bit and end check bit corresponding to the coded information;

[0189] The encoded information is decoded by using the changes in the feedback signal, the start bit and the end check bit to obtain the decoded information.

[0190] Specifically, in order to improve the accuracy of the received coded information, the entire coded information is pre-set with multiple start bits and end check bits to prepare for the decoding work on the primary side. By setting special start bits and end check bits, the primary side control circuit under normal working conditions will parse the coded information according to the changes in the feedback signal, the start bit and the end check bit to obtain the decoded information. That is, the data packet containing the special start bit and end check bit can parse the coded information that the secondary side control circuit wants to send to the primary side control circuit, and then perform voltage and current adjustment.

[0191] The above is a detailed introduction to a switching power supply and a control method for a switching power supply provided by the present invention. The various embodiments in the specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same and similar parts between the various embodiments can be referred to each other. For the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part description. It should be pointed out that for ordinary technicians in this technical field, without departing from the principle of the present invention, the present invention can also be improved and modified in several ways, and these improvements and modifications also fall within the scope of protection of the claims of the present invention.

[0192] It should also be noted that, in this specification, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of additional identical elements in the process, method, article, or apparatus comprising the element.

Claims

1. A switching power supply for supplying power to a load device, characterized in that: include: A secondary side control circuit, coupled to the secondary side of the transformer of the switching power supply, for receiving a power supply demand signal of the load device and encoding the power supply demand signal to generate coding information; The primary side control circuit utilizes the transformer to receive a feedback signal reflecting the output voltage of the switching power supply, decodes the coded information through changes in the feedback signal, and controls the switching power supply to match the power supply demand of the load device.

2. The switching power supply according to claim 1, characterized in that: The process of determining the change of the feedback signal includes: The primary side control circuit uses the transformer to receive the width value of the feedback signal of the current control cycle corresponding to the secondary side control circuit during the conduction time; Acquire a width value of the feedback signal of a previous control cycle, wherein the width value of the feedback signal of the previous control cycle is stored in the primary control circuit; The change of the feedback signal is determined according to the relationship between the difference between the width values ​​of the feedback signal in the current control cycle and the previous control cycle and a threshold.

3. The switching power supply according to claim 2, characterized in that: The primary side control circuit decodes the coded information through the change of the feedback signal, including: When the difference value obtained by the primary control circuit is greater than the threshold value, the primary control circuit decodes the coded information sent by the secondary control circuit to obtain a first level signal; When the acquired difference is less than or equal to the threshold, the primary-side control circuit decodes the coded information sent by the secondary-side control circuit to obtain a second level signal.

4. The switching power supply according to claim 1, characterized in that: The process of determining the change of the feedback signal includes: The primary side control circuit uses the transformer to receive the width value of the feedback signal of the current control cycle corresponding to the secondary side control circuit during the conduction time; Acquire the width value of the feedback signal of the previous control cycle, the primary current of the current control cycle and the previous control cycle, wherein the width value of the feedback signal of the previous control cycle is stored in the primary control circuit; The change of the feedback signal is determined according to the relationship between the width value of the feedback signal in the current control cycle and the previous control cycle and the ratio determined by the primary current in the current control cycle and the previous control cycle.

5. The switching power supply according to claim 4, characterized in that: The primary side control circuit decodes the coded information through the change of the feedback signal, including: When the ratio corresponding to the current control cycle obtained by the primary control circuit is smaller than the ratio corresponding to the previous control cycle, the primary control circuit decodes the coded information sent by the secondary control circuit to obtain a first level signal; When the primary-side control circuit obtains that the ratio corresponding to the current control cycle is equal to the ratio corresponding to the previous control cycle, the primary-side control circuit decodes the coded information sent by the secondary-side control circuit to obtain a second level signal.

6. The switching power supply according to any one of claims 2 to 5, characterized in that: The secondary side control circuit includes a synchronous rectifier diode, and the process of determining the coded information includes: The secondary side control circuit controls the synchronous rectifier diode to perform a delayed shutdown for a preset time when receiving the power supply requirement signal of the load device, and encodes the power supply requirement signal to obtain the encoding information.

7. The switching power supply according to claim 1, characterized in that: The secondary side control circuit includes a synchronous rectifier diode, and the process of determining the coded information includes: When receiving the power demand signal of the load device, the secondary side control circuit controls the synchronous rectifier diode to be turned off during the secondary conduction time, and encodes the power demand signal to obtain the coding information.

8. The switching power supply according to claim 7, characterized in that: The secondary side control circuit includes a secondary side detection circuit, and the process of determining the secondary conduction time of the synchronous rectifier diode includes: The secondary side detection circuit is used to detect the moment when the output voltage signal of the secondary side control circuit changes from a low level signal state, and rises to a high level signal state, and controls the time interval from the second conduction of the synchronous rectifier diode to the low level state as the secondary conduction time.

9. The switching power supply according to claim 8, characterized in that: The primary side control circuit includes a primary side detection circuit, and the process of determining the change of the feedback signal includes: The primary detection circuit is used to detect that the feedback signal decreases and is lower than a reference value, and obtain the relationship between the current feedback signal and the reference value within a specified time to determine the change of the current feedback signal.

10. The switching power supply according to claim 9, characterized in that: The primary side control circuit decodes the coded information through the change of the feedback signal, including: When the primary-side control circuit obtains that the current feedback signal exceeds the reference value again within the specified time, the primary-side control circuit decodes the coded information sent by the secondary-side control circuit to obtain a first level signal; When the primary-side control circuit does not obtain that the current feedback signal exceeds the reference value again within the specified time, the primary-side control circuit decodes the coded information sent by the secondary-side control circuit to obtain a second level signal.

11. The switching power supply according to claim 10, characterized in that: The secondary side control circuit and the primary side control circuit respectively utilize a multiplexed PIN pin and change the resistance value of a resistor connected to the multiplexed PIN pin to determine the specified time, wherein a mapping relationship exists between the change in the resistance value of the resistor connected to the multiplexed PIN pin and the change in the specified time.

12. The switching power supply according to claim 11, characterized in that: The secondary side control circuit also includes a voltage detection circuit; The voltage detection circuit is used to obtain a corresponding voltage value change according to the current value of the VCC PIN pin of the secondary control circuit, wherein the voltage value change is used to represent the resistance value change of the resistor.

13. A method for controlling a switching power supply, characterized in that: The switching power supply is used to supply power to a load device, and comprises a secondary side control circuit and a primary side control circuit, wherein the secondary side control circuit is coupled to the secondary side of a transformer of the switching power supply; Controlling the secondary side control circuit to receive the power supply demand signal of the load device, and encoding the power supply demand signal to generate coding information; The primary control circuit is controlled to use the transformer to receive a feedback signal reflecting the output voltage of the switching power supply, decode the coded information through changes in the feedback signal, and control the switching power supply to match the power supply demand of the load device.

14. The control method of the switching power supply according to claim 13, characterized in that: The process of determining the change of the feedback signal includes: Using the transformer to receive the width value of the feedback signal of the current control cycle corresponding to the conduction time of the secondary side control circuit; Acquire a width value of the feedback signal of a previous control cycle, wherein the width value of the feedback signal of the previous control cycle is stored in the primary control circuit; The change of the feedback signal is determined according to the relationship between the difference between the width values ​​of the feedback signal in the current control cycle and the previous control cycle and a threshold.

15. The control method of the switching power supply according to claim 14, characterized in that: Decoding the encoded information by means of a change in the feedback signal includes: When the acquired difference is greater than the threshold, decoding the coded information sent by the secondary side control circuit to obtain a first level signal; When the acquired difference is less than or equal to the threshold, the coded information sent by the secondary side control circuit is decoded to obtain a second level signal.

16. The control method of the switching power supply according to claim 13, characterized in that: The process of determining the change of the feedback signal includes: Using the transformer to receive the width value of the feedback signal of the current control cycle corresponding to the conduction time of the secondary side control circuit; Acquire the width value of the feedback signal of the previous control cycle, the primary current of the current control cycle and the previous control cycle, wherein the width value of the feedback signal of the previous control cycle is stored in the primary control circuit; The change of the feedback signal is determined according to the relationship between the width value of the feedback signal in the current control cycle and the previous control cycle and the ratio determined by the primary current in the current control cycle and the previous control cycle.

17. The control method of the switching power supply according to claim 16, characterized in that: Decoding the encoded information by means of a change in the feedback signal includes: When the ratio corresponding to the current control cycle obtained is smaller than the ratio corresponding to the previous control cycle, decoding the coded information sent by the secondary side control circuit to obtain a first level signal; When it is obtained that the ratio corresponding to the current control cycle is equal to the ratio corresponding to the previous control cycle, the coded information sent by the secondary side control circuit is decoded to obtain a second level signal.

18. The control method of the switching power supply according to any one of claims 14 to 17, characterized in that: The secondary side control circuit includes a synchronous rectifier diode, and the process of determining the coded information includes: When receiving the power supply requirement signal of the load device, the synchronous rectifier diode is controlled to be turned off with a delay of a preset time, and the power supply requirement signal is encoded to obtain the encoding information.

19. The control method of the switching power supply according to claim 13, characterized in that: The secondary side control circuit includes a synchronous rectifier diode, and the process of determining the coded information includes: When receiving the power supply demand signal of the load device, the power supply demand signal is encoded to obtain the encoding information within the secondary conduction time after the synchronous rectifier diode is controlled to be turned off.

20. The control method of the switching power supply according to claim 19, characterized in that: The secondary side control circuit includes a secondary side detection circuit, and the process of determining the secondary conduction time of the synchronous rectifier diode includes: It is detected that the output voltage signal of the secondary control circuit changes from a low-level signal state and rises to a high-level signal state, and the time interval from the synchronous rectifier diode being controlled to fall to the low-level state after the secondary conduction is used as the secondary conduction time.

21. The control method of the switching power supply according to claim 20, characterized in that: The primary side control circuit includes a primary side detection circuit, and the process of determining the change of the feedback signal includes: It is detected that from the moment when the feedback signal decreases and is lower than the reference value, the relationship between the current feedback signal and the reference value is obtained within a specified time to determine the change of the current feedback signal.

22. The control method of the switching power supply according to claim 21, characterized in that: Decoding the encoded information by means of a change in the feedback signal includes: When it is obtained within the specified time that the current feedback signal exceeds the reference value again, decoding the coded information sent by the secondary side control circuit to obtain a first level signal; When the current feedback signal is not obtained to exceed the reference value again within the specified time, the coded information sent by the secondary side control circuit is decoded to obtain a second level signal.

23. The control method of the switching power supply according to claim 22, characterized in that: The specified time is determined by changing the resistance value of the resistor connected to the multiplexed PIN pin corresponding to the secondary control circuit and the primary control circuit, wherein there is a mapping relationship between the change in the resistance value of the resistor connected to the multiplexed PIN pin and the change in the specified time.

24. The control method of the switching power supply according to claim 23, characterized in that: The secondary side control circuit also includes a voltage detection circuit; A corresponding voltage value change is obtained by detecting the current value of the VCC PIN pin of the secondary side control circuit, wherein the voltage value change is used to characterize the resistance value change of the resistor.

25. The control method of the switching power supply according to claim 13, characterized in that: After receiving the feedback signal by using the transformer, the method further includes: Presetting the start bit and the end check bit corresponding to the coded information; The encoded information is decoded by decoding the encoded information through the change of the feedback signal, the start bit and the end check bit to obtain the decoded information.

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