A flyback converter control system

Abstract

This application provides a flyback converter control system, relating to the field of power converter technology. The control system includes: a primary-side circuit, a primary-side control module, a transformer, a secondary-side circuit, and a secondary-side control module. During the switching process from no-load or very light-load conditions to full-load conditions, the secondary-side control module detects the output voltage. If the output voltage is less than a first preset threshold, the secondary-side control module sends an activation signal to the primary-side control module through the transformer. The primary-side control module generates a corresponding frequency and a corresponding conduction time based on the activation signal to control the primary-side switching transistor in the primary-side circuit, making the output voltage match the rated output voltage corresponding to the full-load condition. This application provides a technical solution to address the technical problems of lag in the converter's response to load changes and low overall power conversion efficiency of the system.

Description

Technical Field

[0001] This application relates to the field of power converter technology, and in particular to a flyback converter control system. Background Technology

[0002] As one of the most widely used power converters in the field of low- and medium-power power electronic conversion, the flyback converter is widely used in various low- and medium-power power supply scenarios such as consumer electronics, industrial control, and smart homes due to its advantages such as simple topology, competitive hardware cost, and excellent power conversion efficiency. The basic circuit topology of the flyback converter mainly consists of three parts: the primary side circuit, the isolation transformer, and the secondary side circuit. It is the core device for realizing isolated power transmission and voltage conversion.

[0003] Depending on the location of the control loop, flyback converters can be broadly classified into two categories: secondary-regulated (SSR) flyback converters and primary-regulated (PSR) flyback converters. SSR flyback converters directly sample the output voltage on the secondary side and transmit the control signal from the secondary side to the primary side using isolation devices such as optocouplers. This controls the on / off state of the primary-side switching transistors, achieving output voltage regulation while ensuring electrical isolation between the primary and secondary sides. However, this type of converter requires dedicated isolation devices such as optocouplers in its control loop, which not only increases the number of hardware components and the complexity of transformer design but also increases overall hardware cost and equipment size. Furthermore, the photoelectric conversion performance of optocouplers degrades over time and under varying operating conditions, easily leading to decreased control signal transmission accuracy and consequently reducing the long-term reliability of the converter, limiting its application in scenarios with stringent cost and stability requirements.

[0004] To address the aforementioned shortcomings of SSR flyback converters, PSR flyback converters were developed. These converters eliminate isolation devices such as optocouplers, indirectly sampling the secondary-side output voltage through the auxiliary winding of the isolation transformer. The control loop is integrated into the primary side, eliminating the need for additional cross-isolation layer signal transmission components. This significantly simplifies the circuit structure, reduces the number of hardware components, and effectively lowers the design, production, and manufacturing costs of the equipment. Simultaneously, it improves the converter's structural compactness and operational reliability, making it the mainstream choice for current low-to-medium power supply scenarios.

[0005] However, existing PSR flyback converters still have many technical defects in practical applications, which restrict their performance improvement and application scenario expansion. Specifically, these defects are as follows: First, the dynamic response performance is poor. Since the primary-side controller can only complete the output voltage sampling once in the secondary freewheeling phase of each switching cycle, when the output voltage fluctuation is detected, it needs to be delayed until the next switching cycle to make a control response. The control process has an inherent delay, which causes the converter to respond lagging to load changes. Second, the system energy loss is high. Existing PSR flyback converters usually need to connect a virtual load in parallel on the output side to consume the excess energy generated by the primary side under no-load or very light-load conditions and maintain the output voltage stability. However, this virtual load is still in working state when the converter is working under normal load, which will continue to generate additional energy loss and significantly reduce the overall power conversion efficiency of the system. Summary of the Invention

[0006] This application provides a flyback converter control system as a technical solution to solve the technical problems of the aforementioned converter's lag response to load changes and the low overall power conversion efficiency of the system.

[0007] This application provides a flyback converter control system, the control system comprising: a primary side circuit, a primary side control module, a transformer, a secondary side circuit, and a secondary side control module; The primary side circuit and the primary side control module are both connected to the primary winding of the transformer, and the secondary side circuit and the secondary side control module are both connected to the secondary winding of the transformer. During the process of the control system switching from no-load or very light-load conditions to full-load conditions, the secondary-side control module is used to detect the output voltage. When the output voltage is less than a first preset threshold, the secondary-side control module is used to send an activation signal to the primary-side control module through the transformer. The primary-side control module is used to generate a corresponding conduction frequency and a corresponding conduction time based on the activation signal, and control the primary-side switching transistor in the primary-side circuit according to the conduction frequency and the conduction time, so that the output voltage is adapted to the rated output voltage corresponding to the full-load condition. The primary-side control module is used to sample the output voltage. When the system is determined to be in an unloaded or extremely light-load condition based on the output voltage, the module reduces the operating frequency of the primary-side switch to the lowest frequency and maintains it for a first preset delay. After the first preset delay, the module controls the primary-side switch to turn off, so that the primary-side control module and the primary-side circuit enter an extremely low-power mode. The primary-side control module is also used to generate a sleep signal after the primary-side switch is turned off, and send the sleep signal to the secondary-side control module through the transformer so that the control system enters an ultra-low power mode.

[0008] In one optional implementation, the primary-side circuit includes a primary-side switching transistor, an auxiliary winding, a power supply diode, and a first filter capacitor. The auxiliary winding and the primary winding of the transformer are wound together on the core of the transformer. One end of the auxiliary winding is grounded and the other end of the auxiliary winding is connected to the anode of the power supply diode. The cathode of the power supply diode is connected to the first plate of the first filter capacitor, and the second plate of the first filter capacitor is grounded. Both the primary-side control module and the auxiliary winding are connected to the connection node of the power supply diode. The primary-side control module is used to sample the output voltage through the auxiliary winding. The drain of the primary-side switching transistor is connected to the primary winding of the transformer, the source is grounded, and the control terminal is connected to the primary-side control module. The primary-side control module is used to generate a primary drive signal based on the sampled output voltage; the primary drive signal is used to control the on and off of the primary-side switching transistor.

[0009] In one optional implementation, the secondary-side control circuit includes a second filter capacitor and a secondary-side switching transistor. One end of the secondary winding of the transformer is connected to the drain of the secondary-side switching transistor, and the other end is connected to the first plate of the second filter capacitor; the source of the secondary-side switching transistor and the second plate of the second filter capacitor are connected and then grounded. The control terminal of the secondary-side switch is connected to the drive output terminal of the secondary-side control module; The secondary-side control module is connected to the secondary winding of the transformer and is used to detect the output voltage and sleep signal.

[0010] In one optional implementation, during the process of the control system switching from the no-load condition or the very light-load condition to the full-load condition, the secondary-side control module is used to detect the output voltage. When the output voltage is less than the first preset threshold, the secondary-side control module outputs a high-level signal to control the secondary-side switch to be pre-turned on, so as to generate a first alternating current in the secondary winding of the transformer. The transformer is used to generate a first alternating magnetic flux in the magnetic core based on the first alternating current; The auxiliary winding of the transformer is used to induce a first characteristic ringing signal corresponding to the first alternating magnetic flux through magnetic core coupling, and transmits the first characteristic ringing signal as the activation signal to the primary side control module.

[0011] In one optional implementation, the secondary-side control module is further configured to determine, according to the hibernation command, whether the control system switches to the no-load condition or the extremely light-load condition, and after a second preset delay, enable the secondary-side control module and the secondary-side circuit to enter an extremely low-power mode, at which time the system enters the extremely low-power mode.

[0012] In one optional implementation, the secondary-side control module includes a secondary-side controller and a secondary-side voltage holding unit; the secondary-side controller is connected to the secondary-side voltage holding unit. The secondary-side controller is used to send an enable signal to the secondary-side voltage holding unit when the control system enters the ultra-low power mode, so as to start the secondary-side voltage holding unit. The secondary-side voltage holding unit is used to detect the output voltage. When the output voltage is less than the second preset threshold, it sends a power replenishment and conduction command to the primary-side control module through the transformer. After receiving the power replenishment command, the primary-side control module controls the primary-side switch to turn on once, so that the output voltage rises back to the preset voltage range corresponding to the ultra-low power mode.

[0013] In one optional implementation, the secondary-side control module further includes a discharge unit; the secondary-side controller is also connected to the discharge unit. The voltage holding unit is also used to send a discharge command to the secondary controller when the output voltage is greater than a third preset threshold. The secondary-side controller is used to control the operation of the discharge module according to the discharge command, so that the output voltage drops to a preset voltage range corresponding to the ultra-low power mode.

[0014] In one optional implementation, the primary-side control module includes a signal detection module and a primary-side controller, wherein the primary-side controller is connected to the signal detection module and the control terminal of the primary-side switching transistor. The primary-side controller is used to control the primary-side switch to turn on at the lowest operating frequency when the control system switches to the no-load condition or the extremely light-load condition, and to turn off the primary-side switch after maintaining the lowest operating frequency for a first preset delay, and to transmit the generated sleep signal to the secondary-side controller through the transformer. The secondary-side controller is used to send an enable signal to the secondary-side voltage holding unit when the sleep signal is detected, so as to start the secondary-side voltage holding unit and the system enters an ultra-low power mode. When the control system is in the ultra-low power mode and the system is connected to a load, the secondary-side controller is used to shut down the secondary-side voltage holding unit when the drop value of the output voltage is greater than a preset detection threshold, and to generate a first characteristic ringing signal in the transformer by controlling the secondary-side switching transistor to pre-turn on, which is then transmitted to the signal detection module of the primary-side control module as an activation signal. The primary-side controller is used to control the primary-side switch to turn on at a preset operating frequency after the signal detection module receives the activation signal, so that the system exits the ultra-low power mode.

[0015] In one alternative implementation, when the system transitions from a full-load condition to an unloaded or very light-load condition, the primary-side controller is used to gradually reduce the current operating frequency of the primary-side switching transistor to a preset switching frequency threshold. The primary-side controller is also used to control the primary-side circuit and the primary-side control module to enter an ultra-low power mode after the switching frequency of the primary-side switch is lower than a preset switching frequency threshold and continues for a first preset duration. After the primary-side circuit and the primary-side control module enter the ultra-low power mode, the secondary-side controller is used to control the secondary-side circuit and the secondary-side control module to enter the ultra-low power mode if the switching frequency of the primary-side switch is continuously detected to be lower than the preset switching frequency threshold within a second preset time period. At this time, the system enters the ultra-low power mode.

[0016] In one optional embodiment, the primary-side control module further includes a primary-side power supply voltage holding unit and a primary-side voltage detection unit; and the primary-side controller is connected to both the primary-side power supply voltage holding unit and the primary-side voltage detection unit. When the system is in an ultra-low power mode, the primary-side controller is used to turn off the primary-side switching transistor and turn on the primary-side power supply voltage holding unit and the primary-side voltage detection unit. The primary-side power supply voltage holding unit is used to provide a minimum operating voltage to the primary-side controller when the system is in an ultra-low power mode and the primary-side switch is in the off state. When the primary side voltage detection unit detects that the supply voltage of the primary side controller drops to a preset minimum sustaining threshold, the primary side controller is used to control the primary side switch to turn on with the minimum sustaining power so as to supply power to the primary side controller through the auxiliary winding of the transformer. When the voltage detection unit detects that the supply voltage of the primary-side controller rises back to the preset maximum maintenance threshold, the primary-side controller controls the primary-side switch to turn off.

[0017] In one optional implementation, the secondary-side control module further includes a secondary-side voltage detection unit, which is connected to the secondary-side controller; the secondary-side voltage detection unit is also connected to the output port of the system for detecting the output voltage. When the secondary-side control module enters an ultra-low power mode, the secondary-side controller enables the secondary-side voltage holding unit and the secondary-side voltage detection unit. The secondary-side controller is used to send a power replenishment signal to the primary-side controller through the transformer when the output voltage is detected by the secondary-side voltage detection unit to drop to a preset voltage threshold. After receiving the power replenishment signal, the primary-side controller turns on the primary-side switch until the output voltage rises back to the preset voltage threshold, at which point it turns off the primary-side switch.

[0018] In one optional implementation, when the system is in an ultra-low power mode and the secondary-side voltage detection unit detects that the output voltage has dropped to the secondary activation threshold voltage, the secondary-side controller is used to control the secondary-side circuit and the secondary-side control module to exit the ultra-low power mode, and to generate a first characteristic ringing signal in the transformer as an activation signal by controlling the pre-turn-on of the secondary-side switch, which is then transmitted to the primary-side controller. The primary-side controller is used to control the primary-side circuit and the primary-side control module to exit the ultra-low power mode after receiving the activation signal, waiting for a preset primary detection shielding time, and identifying the ringing signal within a preset activation signal identification window. It then controls the primary-side switch to turn on with a preset operating frequency and duty cycle so that the output voltage returns to the normal operating range.

[0019] With the above technical solution, the flyback converter control system provided in this application embodiment uses the secondary-side control module to directly detect the output voltage as the trigger for operating condition switching, solving the delay problem of indirect sampling by the primary side in the prior art. When the system switches from no-load / very light-load to full-load and the output voltage drops to the first preset threshold, the secondary side can trigger an activation signal and transmit it to the primary side through the transformer. After receiving the activation signal, the primary-side control module generates a conduction frequency and conduction time adapted to the full-load operating condition, and controls the primary-side switching transistor to operate. There is no need to wait for the sampling and response process of the original switching cycle of the primary side, eliminating the inherent control delay of the PSR flyback converter in the prior art and realizing a fast response to load switching. At the same time, by detecting the output voltage in real time by the secondary side, the dynamic change from no-load / very light-load to full-load can be accurately captured, avoiding a serious drop in output voltage due to the increased detection cycle, greatly improving the stability of the output voltage during large dynamic load switching, and enabling the output voltage to quickly adapt to the rated value of the full-load operating condition, ensuring the normal start-up and operation of electrical equipment.

[0020] Furthermore, existing PSR flyback converters require a virtual load to be connected in parallel on the output side to consume excess energy from the primary winding in order to maintain stable output voltage under no-load / very light-load conditions. However, this virtual load continues to operate under normal load conditions, introducing irreversible additional energy loss. In the embodiments of this application, when the system switches from a full-load condition to a no-load / very light-load condition, the primary-side control module, upon determining that the system is in a no-load or very light-load condition, first reduces the operating frequency of the switching transistor to the lowest frequency and maintains it for a first preset delay to avoid false triggering by instantaneous load fluctuations. Then, it turns off the primary-side switching transistor, controlling the primary-side control module and the primary-side circuit to enter an ultra-low-power mode, thereby enabling the system to enter an ultra-low-power mode. During this process, the primary-side control module stops invalid waveform generation through frequency reduction, delay, and shutdown steps, eliminating the generation of excess primary energy under no-load / very light-load conditions from the root, without the need for virtual loads to consume energy. At the same time, in the ultra-low power mode, the system only maintains necessary detection and control functions, with no additional energy loss paths. Compared with traditional solutions, it not only retains the output voltage stability under no-load / very light-load conditions, but also eliminates the additional losses caused by virtual loads, significantly improving the system's power conversion efficiency under all operating conditions and optimizing efficiency under light-load and no-load conditions.

[0021] Furthermore, in this embodiment, when switching from full load to no load / very light load, the primary side, upon determining that the system is in no load or very light load condition, does not directly turn off the switching transistor. Instead, it first reduces the frequency to the minimum and maintains it for a first preset delay. This delay confirmation avoids false triggering of the very low power mode caused by instantaneous load fluctuations. When switching from no load / very light load to full load, the secondary side uses the output voltage being less than a first preset threshold as the trigger condition for the activation signal. Based on the quantitative detection of voltage drop, it achieves accurate determination of the operating condition switch, avoiding false activation caused by noise and small voltage fluctuations. This enables the system to accurately identify the actual load condition changes and achieve smooth switching between sleep, activation, and normal operation modes, improving the stability and adaptability of the system in actual industrial scenarios. Attached Figure Description

[0022] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0023] Figure 1 This is a schematic diagram of the structure of a flyback converter control system provided in an embodiment of the present invention; Figure 2 A schematic diagram of the primary / secondary coordinated control logic of a flyback converter control system during operating condition switching, provided in an embodiment of this application; Figure 3 A diagram illustrating the dynamic switching process of a flyback converter control system from normal operating mode to ultra-low power sleep mode, provided in an embodiment of the present invention. Figure 4 A flowchart of voltage maintenance and activation triggering logic for a flyback converter control system in sleep mode, provided by an embodiment of the present invention; Figure 5 A flowchart illustrating the activation triggering logic of a flyback converter control system in sleep mode, provided in an embodiment of the present invention; Figure 6 A schematic diagram of two energy replenishment processes in sleep mode for a flyback converter control system provided in an embodiment of the present invention; Figure 7 This is a diagram illustrating the dynamic activation process of a flyback converter control system switching from an ultra-low power mode to a normal operating mode, as provided in an embodiment of the present invention.

[0024] Figure description: 101 - Primary side circuit, 102 - Primary side control module, 201 - Secondary side control circuit, 202 - Secondary side control module, 30 - Transformer, 40 - EMI and rectifier input module. Detailed Implementation

[0025] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present invention.

[0026] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of this application. It is understood that the terms “first,” “second,” etc., as used herein may be used to describe various information or data, but these elements are not limited by these terms. These terms are only used to distinguish first information from another type of information. For example, without departing from the scope of this application, first action information may be referred to as second action information, and similarly, second action information may be referred to as first action information. Both first action information and second action information are action information, but they are not the same action information.

[0027] In this document, it should be understood that the terminology used is for convenience of understanding only and does not imply any limitation on its meaning. Furthermore, any number of elements in the accompanying drawings is for illustrative purposes only and not for limitation, and any naming is for distinction only and has no limiting meaning.

[0028] As one of the most widely used power converters in the field of low- and medium-power power electronic conversion, the flyback converter is widely used in various low- and medium-power power supply scenarios such as consumer electronics, industrial control, and smart homes due to its advantages such as simple topology, competitive hardware cost, and excellent power conversion efficiency. The basic circuit topology of the flyback converter mainly consists of three parts: the primary side circuit, the isolation transformer, and the secondary side circuit. It is the core device for realizing isolated power transmission and voltage conversion.

[0029] Depending on the location of the control loop, flyback converters can be broadly classified into two categories: secondary-regulated (SSR) flyback converters and primary-regulated (PSR) flyback converters. SSR flyback converters directly sample the output voltage on the secondary side and transmit the control signal from the secondary side to the primary side using isolation devices such as optocouplers. This controls the on / off state of the primary-side switching transistors, achieving output voltage regulation while ensuring electrical isolation between the primary and secondary sides. However, this type of converter requires dedicated isolation devices such as optocouplers in its control loop, which not only increases the number of hardware components and the complexity of transformer design but also increases overall hardware cost and equipment size. Furthermore, the photoelectric conversion performance of optocouplers degrades over time and under varying operating conditions, easily leading to decreased control signal transmission accuracy and consequently reducing the long-term reliability of the converter, limiting its application in scenarios with stringent cost and stability requirements.

[0030] To address the aforementioned shortcomings of SSR flyback converters, PSR flyback converters were developed. These converters eliminate isolation devices such as optocouplers, indirectly sampling the secondary-side output voltage through the auxiliary winding of the isolation transformer. The control loop is integrated into the primary side, eliminating the need for additional cross-isolation layer signal transmission components. This significantly simplifies the circuit structure, reduces the number of hardware components, and effectively lowers the design, production, and manufacturing costs of the equipment. Simultaneously, it improves the converter's structural compactness and operational reliability, making it the mainstream choice for current low-to-medium power supply scenarios.

[0031] However, existing PSR flyback converters still have many technical defects in practical applications, which restrict their performance improvement and application scenario expansion. Specifically, these defects are as follows: First, the dynamic response performance is poor. Since the primary-side controller can only complete the output voltage sampling once in the secondary freewheeling phase of each switching cycle, when the output voltage fluctuation is detected, it needs to be delayed until the next switching cycle to make an adjustment response. The control process has an inherent delay, which causes the converter to respond lagging to load changes. Second, the output voltage stability is poor when the load is dynamically switched. Especially in the case of switching from no-load / very light load to full load, the voltage detection cycle of the primary-side controller in the very light load mode becomes significantly longer, which makes it impossible to accurately capture the dynamic changes of the load. This can easily cause a serious drop in output voltage, affecting the normal start-up and operation of electrical equipment. Third, the system has high energy loss. Existing PSR flyback converters usually need to connect a virtual load in parallel on the output side to consume the excess energy generated by the primary side under no-load or very light-load conditions and maintain the stability of the output voltage. However, this virtual load is still in operation when the converter is working under normal load, and will continue to generate additional energy loss, which greatly reduces the overall power conversion efficiency of the system.

[0032] Based on the above description, the technical concept of this application embodiment is as follows: Addressing the technical problems of poor dynamic response, large voltage fluctuations during load switching, and additional losses introduced by virtual loads in PSR flyback converters, a control system composed of a primary-side circuit, a primary-side control module, a transformer, a secondary-side circuit, and a secondary-side control module is proposed. This system allows the secondary-side control module to directly detect the output voltage as the basis for operating condition switching. When switching from no-load / very light-load to full-load, the secondary side detects that the output voltage is lower than a first preset threshold and sends an activation signal to the primary side through the transformer. The primary side then generates a frequency and conduction time adapted to the full-load condition and controls the primary-side switching transistor to quickly match the rated output voltage. When switching from full-load to no-load / very light-load, the primary-side control module, based on the output voltage, determines that the system is in no-load or very light-load condition, reduces the switching transistor frequency to the minimum and delays it before turning off the switching transistor to allow the system to enter an ultra-low power mode.

[0033] Reference Figure 1 and Figure 2 This application provides a flyback converter control system, which includes: a primary side circuit, a primary side control module 102, a transformer 30, a secondary side circuit, and a secondary side control module 202. The primary side circuit and the primary side control module 102 are both connected to the primary winding Np of the transformer 30, and the secondary side circuit and the secondary side control module 202 are both connected to the secondary winding Ns of the transformer 30. During the process of the control system switching from no-load or very light-load conditions to full-load conditions, the secondary-side control module is used to detect the output voltage of the secondary-side circuit. When the output voltage is less than a first preset threshold, the secondary-side control module is used to send an activation signal to the primary-side control module through the transformer 30. Based on the activation signal, the primary-side control module generates a corresponding conduction frequency and conduction time, and controls the primary-side switching transistor Q1 in the primary-side circuit according to the conduction frequency and conduction time, so that the output voltage is adapted to the rated output voltage corresponding to the full-load condition. The primary-side control module 102 samples the output voltage. When it is determined that the system is in an unloaded or extremely light-load condition based on the output voltage, it reduces the operating frequency of the primary-side switch Q1 to the lowest frequency and maintains it for a first preset delay. After the first preset delay, it controls the primary-side switch Q1 to turn off, so that the primary-side control module 102 and the primary-side circuit 101 enter an extremely low-power mode. The primary-side control module 102 is also used to generate a sleep signal after the primary-side switch Q1 is turned off, and send the sleep signal to the secondary-side control module 102 through the transformer so that the control system enters an ultra-low power mode.

[0034] In this embodiment, the system further includes an EMI filter (Electromagnetic Interference filter) and a rectifier input module 40. The EMI and rectifier input module 40 is the front-end energy input of the entire power supply, responsible for converting the AC input into a stable DC bus voltage to provide energy for the primary-side circuit and the transformer. The AC input (L / N) of the EMI and rectifier input module 40, after rectification by the rectifier bridge and filtering by the filter capacitor, outputs a DC bus voltage that is directly connected to the upper end of the primary winding Np of the high-frequency transformer. This DC bus voltage provides the operating power for the primary-side power switch Q1. The drain of Q1 is connected to the lower end of Np, and the source is grounded. The primary-side control module controls the conduction and turn-off of Q1 by driving its gate (DRV_P), thereby controlling the current flow through the primary winding Np and realizing energy storage and transfer in the transformer.

[0035] The upper end of the primary winding Np of the transformer is directly connected to the DC bus output terminal of the rectifier input module, and the lower end is connected to the drain of the power switch Q1. When Q1 is turned on, the DC bus voltage is applied across Np, the current rises linearly, and energy is stored in the transformer core in the form of a magnetic field. When Q1 is turned off, the energy in the core is released to the secondary circuit through the secondary winding Ns. One end of the auxiliary winding Naux is connected to the power supply circuit of the primary control module, and its induced voltage provides operating power to the primary control module when Q1 is turned off.

[0036] The primary side circuit serves as the power input and primary energy conversion unit of the converter. One end is connected to an external power supply, and the other end is electrically connected to the primary side control module 102 and the primary winding Np of the transformer 30, respectively. Its core component is the primary side switch Q1. The on and off states of this switch directly determine the energy output efficiency and frequency of the primary side and it is the execution component for primary side energy regulation.

[0037] The primary-side control module 102, as the primary-side control component, is electrically connected to the primary-side circuit 101 and the primary winding Np of the transformer 30. It is used to receive control signals transmitted by the secondary-side control module 202 and generate corresponding control parameters (switching frequency, conduction time) based on the signal instructions, thereby driving the primary-side switch Q1 to turn on and off. It is also responsible for triggering the system to enter or exit the ultra-low power mode.

[0038] Transformer 30 connects the primary and secondary sides to achieve isolated transmission of electrical energy and coupled transmission of control signals. Its primary winding Np is connected to the primary side circuit 101 and the primary side control module 102 to receive electrical energy input from the primary side and perform electromagnetic energy conversion. Its secondary winding Ns is connected to the secondary side circuit 201 and the secondary side control module 202 to transmit the converted electrical energy to the secondary side. At the same time, with the help of magnetic core coupling, it transmits control signals such as activation signals sent from the secondary side to the primary side without the need for additional optocouplers or other isolation devices.

[0039] The secondary side circuit 201 serves as an energy output unit. One end is connected to the secondary winding Ns of the transformer 30 to receive the electromagnetic energy transmitted by the transformer 30 and perform rectification and filtering. The other end is connected to the load to provide a stable output voltage to the load. Its working status is monitored and regulated in real time by the secondary side control module 202 to ensure that the output voltage is adapted to the load's operating conditions.

[0040] The secondary-side control module 202 is electrically connected to the secondary-side circuit and the secondary winding Ns of the transformer 30. It is used to detect the output voltage of the secondary-side circuit in real time, determine the operating condition switching state of the system based on the change of the output voltage, and generate corresponding control commands. These commands are then transmitted to the primary-side control module 102 through the magnetic core coupling of the transformer 30 to achieve coordinated control of the primary and secondary sides.

[0041] Based on the above structure, when a load is connected (switching from no-load / very light-load to full-load), the output voltage of the secondary side circuit 201 will drop due to sudden load changes and a surge in energy demand. At this time, the secondary side control module 202 continuously monitors the output voltage of the secondary side circuit 201 in real time, dynamically monitoring the changes in output voltage to capture the signal of the operating condition switching. During the dynamic monitoring process, the secondary side control module 202 compares the detected real-time output voltage with a preset first preset threshold (this threshold is the minimum output voltage threshold adapted to the full-load operating condition; if it is lower than this threshold, the normal operation requirements of the full-load load cannot be met). When the detected output voltage is less than the first preset threshold, the secondary side control module 202 determines that the system has entered the switching process from no-load / very light-load to full-load, immediately generates an activation signal, and transmits it to the transformer core through the secondary winding Ns of the transformer 30. With the help of the magnetic core coupling, the activation signal is transmitted contactlessly to the primary winding Np of the transformer 30, and then to the primary side control module 102.

[0042] After receiving the activation signal from the secondary side, the primary-side control module 102 identifies the operating condition switching requirement and generates control parameters adapted to the full-load operating condition based on the instructions of the activation signal, namely the corresponding conduction frequency and the conduction time of the primary-side switch Q1.

[0043] The primary-side control module 102 transmits the generated conduction frequency and conduction time signals to the primary-side switch Q1 of the primary-side circuit, controlling the primary-side switch Q1 to conduct and turn off according to these parameters. By adjusting the switching frequency and conduction time, the energy input to the primary winding Np of the transformer 30 is changed, and then coupled to the secondary side through the transformer 30, so that the output voltage of the secondary-side circuit can quickly recover and finally adapt to the rated output voltage corresponding to the full-load condition, ensuring stable operation under full load and completing the entire activation control process.

[0044] When the load condition of the control system switches from full load to no load or very light load, the system energy demand drops sharply. At this time, sleep control needs to be activated to avoid unnecessary energy generation from invalid waveforms on the primary side, eliminate the additional losses of virtual load, and achieve low power consumption operation. The specific control process is as follows: The primary-side control module is used to sample the output voltage. When the sampled output voltage shows a significant increase (due to reduced load, lower energy demand, and excess energy on the secondary side), and the voltage change pattern indicates that the control system has switched from full-load to no-load or very light-load conditions, an ultra-low power consumption preparation action is executed: First, the operating frequency of the primary-side switching transistor Q1 is reduced to a preset minimum operating frequency (this frequency is the switching frequency corresponding to the lowest power consumption of the system, which can minimize energy loss); at the same time, if the minimum operating frequency is maintained for a first preset delay, this delay is designed to prevent false triggering, to confirm the authenticity of the condition switch, to avoid false sleep caused by instantaneous load fluctuations, and to ensure the reliability of the sleep command.

[0045] After the first preset delay ends, the primary-side control module 102 confirms that the system is indeed under no-load or very light-load conditions, and then controls the primary-side switch Q1 in the primary-side circuit to turn off. After the primary-side switch Q1 is turned off, the primary side stops inputting energy to the primary winding Np of the transformer 30. At this time, the primary side sends a sleep signal to the secondary side through the transformer. After receiving the sleep signal, the secondary-side control module 202 only maintains the necessary detection functions, thereby enabling the entire control system to enter an extremely low-power mode. In this mode, the system power consumption is reduced to the minimum, achieving extremely low power consumption, while eliminating the need for virtual loads to consume excess energy and eliminating the additional losses caused by virtual loads.

[0046] It should be understood that the sleep signal is the signal generated by the transformer after the primary side switch Q1 is turned off. The embodiments of this application do not limit the form of the signal. As long as it is a signal generated by the transformer after the primary side switch Q1 is turned off, it is within the protection scope of the embodiments of this application.

[0047] Existing PSR flyback converters require a virtual load to be connected in parallel on the output side to consume excess energy from the primary winding in order to maintain stable output voltage under no-load / very light-load conditions. However, this virtual load continues to operate under normal load conditions, introducing irreversible additional energy loss. In the embodiments of this application, when the system switches from a full-load condition to a no-load / very light-load condition, the primary-side control module, upon determining that the system is in a no-load or very light-load condition, first reduces the operating frequency of the switching transistor to the lowest frequency and maintains it for a first preset delay to avoid false triggering by instantaneous load fluctuations. Then, it turns off the primary-side switching transistor Q1, controlling the primary-side control module and the primary-side circuit to enter an ultra-low-power mode, thereby enabling the system to enter an ultra-low-power mode. During this process, the primary side stops invalid waveforms through frequency reduction, delay, and shutdown steps, eliminating the generation of excess primary energy under no-load / very light-load conditions from the root, without the need for virtual loads to consume energy. At the same time, in the ultra-low power mode, the system only maintains necessary detection and control functions, with no additional energy loss paths. Compared with traditional solutions, it not only retains the output voltage stability under no-load / very light-load conditions, but also eliminates the additional losses caused by virtual loads, significantly improving the system's power conversion efficiency under all operating conditions and optimizing efficiency under light-load and no-load conditions.

[0048] Furthermore, in this embodiment, when switching from full load to no load / very light load, the primary side, upon determining that the system is in no load or very light load condition, does not directly turn off the switching transistor. Instead, it first reduces the frequency to the minimum and maintains it for a first preset delay. This delay confirmation avoids false triggering of the extremely low power mode caused by instantaneous load fluctuations. When switching from no load / very light load to full load, the primary side uses the output voltage as the trigger condition. Based on the quantitative detection of voltage drop, it achieves accurate determination of the operating condition switch, avoiding false activation caused by noise and small voltage fluctuations. This enables the system to accurately identify the actual load condition changes and achieve smooth switching between sleep, activation, and normal operation modes, improving the stability and adaptability of the system in actual industrial scenarios.

[0049] In one alternative implementation, refer to Figure 1 The primary side circuit 101 includes a primary side switch Q1, an auxiliary winding Naux, a power supply diode D1, and a first filter capacitor C1.

[0050] The auxiliary winding Naux and the primary winding Np of the transformer 30 are wound together on the magnetic core of the transformer 30. One end of the auxiliary winding Naux is grounded, and the other end of the auxiliary winding Naux is connected to the anode of the power supply diode D1. The cathode of the power supply diode D1 is connected to the first plate of the first filter capacitor C1, and the second plate of the first filter capacitor C1 is grounded. The primary-side control module 102 is connected to the connection node between the auxiliary winding Naux and the power supply diode D1. The primary-side control module 102 is used to sample the output voltage through the auxiliary winding Naux. The drain of the primary-side switch Q1 is connected to the primary winding Np of the transformer 30, the source is grounded, and the control terminal is connected to the primary-side control module 102. The primary-side control module 102 is used to generate a primary drive signal based on the sampled output voltage; the primary drive signal is used to control the on and off of the primary-side switch Q1.

[0051] In this embodiment, the primary-side switch Q1 is used to control the on / off state of primary-side energy. It can be a power switching device (such as a MOSFET). Its drain is connected to one end of the primary winding Np of the transformer 30 to receive the electrical energy transmitted by the primary winding Np. Its source is directly grounded to form the common terminal of the current loop. Its control terminal is connected to the drive output terminal of the primary-side control module 102 to receive the primary drive signal output by the primary-side control module 102. By changing the high and low levels of the primary drive signal, it realizes its own on / off control, thereby regulating the energy output rhythm of the primary side.

[0052] The auxiliary winding Naux and the primary winding Np of transformer 30 are wound with a common magnetic core and do not directly participate in the main power transmission; they are used for voltage sampling and power supply. Their connection method is as follows: one end is directly grounded to ensure a stable potential reference; the other end is connected to the anode of the power supply diode D1, forming a node for voltage output and transmission. This node also serves as the sampling and power supply input node for the primary-side control module 102. Because the auxiliary winding Naux and the primary winding Np share a common magnetic core, their voltage changes have a fixed coupling ratio, and the voltage of the auxiliary winding Naux can indirectly reflect the change in the secondary-side output voltage.

[0053] For example, the primary-side control module samples the output voltage signal through the auxiliary winding, and the primary-side controller generates a corresponding primary drive signal DRV_P to control the primary-side switch Q1. During the Q1 turn-on phase, the primary magnetizing inductor stores energy, and the primary current increases linearly until it rises to the maximum current threshold, at which point Q1 turns off. During the Q1 turn-off phase, the inductor releases the stored energy, and the secondary current decreases linearly. During this phase, the primary-side control module can obtain the secondary output voltage information by detecting the auxiliary winding voltage, and its calculation formula is as follows:

[0054] Where VFB is the sampling voltage of the primary winding, Naux is the number of turns of the auxiliary winding, Ns is the number of turns of the secondary winding, Vo is the output voltage, Vf is the voltage drop of the secondary diode, and k is the sampling coefficient of VFB.

[0055] The power supply diode D1, acting as a unidirectional conductor and rectifier, stabilizes the output voltage of the auxiliary winding Naux, preventing reverse current surges from damaging circuit components. Its anode is connected to the end of the auxiliary winding Naux furthest from ground, and its cathode is connected to the first plate of the first filter capacitor C1. Utilizing the diode's unidirectional conductivity, it allows only the forward voltage generated by the auxiliary winding Naux to pass through, blocking reverse current and ensuring the stability of subsequent power supply and sampling voltage.

[0056] The first filter capacitor C1, acting as a filter and energy storage device, filters and stabilizes the voltage output from the power supply diode D1, providing a stable operating power supply to the primary-side control module 102. Its first plate is connected to the cathode of the power supply diode D1, receiving the voltage after rectification by the diode; its second plate is directly grounded, sharing a common ground with the source ground and the auxiliary winding Naux ground, forming a filter circuit. Through its own charging and discharging characteristics, it filters out high-frequency ripple in the output voltage of the auxiliary winding Naux, keeping the voltage output to the primary-side control module 102 stable and preventing ripple interference with the sampling accuracy and drive signal generation accuracy of the primary-side control module 102.

[0057] In addition, the sampling and power supply input terminals of the primary side control module 102 are both connected to the connection node of the auxiliary winding Naux and the power supply diode D1. On the one hand, the voltage signal of the auxiliary winding Naux is collected through this node to realize indirect sampling of the output voltage; on the other hand, the power supply after being regulated by the first filter capacitor C1 is received through this node to ensure its own stable operation. Its drive output terminal is connected to the control terminal of the primary side switch Q1 to output the primary drive signal and control the switching on and off of the switch.

[0058] The operation of the primary side circuit 101 is as follows: When the system starts, the primary winding Np of transformer 30 is connected to the input power supply. Since the auxiliary winding Naux and the primary winding Np share the same magnetic core, the electromagnetic energy generated by the primary winding Np after being energized will be coupled to the auxiliary winding Naux through the magnetic core, causing the auxiliary winding Naux to generate a voltage of the corresponding proportion. This voltage is output through the auxiliary winding Naux to the connection node with the power supply diode D1. Through the unidirectional conductivity of the power supply diode D1, the reverse current is blocked and the initial rectification is completed, and the voltage is output to the first filter capacitor C1. The first filter capacitor C1 performs high-frequency ripple filtering on this voltage and outputs a stable DC voltage to the primary side control module 102, providing a continuous and stable operating power supply for the primary side control module 102, ensuring that it can normally complete functions such as sampling, signal processing and drive signal generation.

[0059] It should be understood that, since the auxiliary winding Naux and the primary winding Np share a common core, their voltage amplitudes and trends exhibit a fixed coupling ratio. Furthermore, the primary winding Np and the secondary winding Ns also have a fixed coupling relationship. Therefore, the voltage signal induced by the auxiliary winding Naux has a clear correspondence with the output voltage of the secondary circuit (the coupling ratio can be preset through the winding turns ratio). The primary-side control module 102, through its connection nodes with the auxiliary winding Naux and the power supply diode D1, acquires the voltage signal of the auxiliary winding Naux in real time. This sampled signal undergoes internal signal processing and conversion to indirectly obtain the actual output voltage value of the secondary circuit, completing the indirect sampling of the output voltage without contact or isolation devices.

[0060] The primary-side control module 102 analyzes and processes the acquired auxiliary winding Naux voltage signal, and generates a corresponding primary drive signal (high and low level pulse signal) based on the current system operating conditions (normal operation, sleep, activation) and output voltage requirements. This primary drive signal is transmitted to the control terminal of the primary-side switch Q1 through the drive output terminal of the primary-side control module 102. When the drive signal is high, the primary-side switch Q1 is turned on, the primary winding Np is connected to the input power supply, and begins to store electromagnetic energy. When the drive signal is low, the primary-side switch Q1 is turned off, and the electromagnetic energy stored in the primary winding Np is coupled to the secondary winding Ns through the magnetic core to power the secondary circuit. By switching the high and low levels of the primary drive signal, the on and off duration and frequency of the primary-side switch Q1 are controlled, thereby regulating the energy storage and release rhythm of the primary winding Np and achieving stable control of the secondary output voltage.

[0061] Based on the above description, compared to the SSR flyback converter which requires additional isolation devices such as optocouplers to achieve secondary voltage sampling and signal transmission, the primary side circuit 101 of this circuit adopts the auxiliary winding Naux common core coupling method, and indirectly samples the secondary output voltage through the auxiliary winding Naux. It does not require optocouplers, additional sampling links or other isolation or sampling components, which greatly reduces the number of hardware components and simplifies the topology of the primary side circuit.

[0062] Furthermore, the primary-side circuit 101 includes a power supply diode D1 and a first filter capacitor C1. The power supply diode D1 can achieve unidirectional rectification, blocking reverse current surges and preventing the reverse voltage output from the auxiliary winding Naux from damaging the primary-side control module 102. The first filter capacitor C1 can filter out high-frequency ripple in the output voltage of the auxiliary winding Naux, providing a stable and interference-free power supply for the primary-side control module 102. This ensures that the primary-side control module 102 can stably complete functions such as sampling, signal processing, and drive signal generation, avoiding problems such as control logic disorder and abnormal switching transistor drive caused by unstable power supply. At the same time, the auxiliary winding Naux and the primary winding Np are wound with a common magnetic core, and their coupling ratio is fixed. This allows the voltage signal sampled by the auxiliary winding Naux to accurately reflect the changes in the secondary-side output voltage with small sampling errors. This provides a reliable basis for the primary-side control module 102 to generate accurate primary drive signals, ensuring stable regulation of the output voltage.

[0063] Furthermore, refer to Figure 1 The secondary-side control circuit 201 includes a second filter capacitor C2 and a secondary-side switching transistor Q2. One end of the secondary winding Ns of the transformer 30 is connected to the drain of the secondary-side switch Q2, and the other end is connected to the first plate of the second filter capacitor C2; the source of the secondary-side switch Q2 and the second plate of the second filter capacitor C2 are connected and then grounded. The control terminal of the secondary-side switch Q2 is connected to the drive output terminal of the secondary-side control module; The secondary-side control module is connected to the secondary winding Ns of the transformer 30 and is used to detect the output voltage and the sleep signal.

[0064] In this embodiment, the secondary-side switch Q2 serves as the actuator for secondary-side energy on / off and freewheeling control. It can be a synchronous rectifier switching device (such as a synchronous rectifier MOSFET). Its drain is connected to one end of the secondary winding Ns of the transformer 30 to receive the electromagnetic energy coupled and transferred from the secondary winding Ns of the transformer 30. Its source is connected to the second plate of the second filter capacitor C2 and grounded together. Its control terminal is connected to the drive output terminal of the secondary-side control module 202 to receive the secondary drive signal output by the secondary-side control module 202. By changing the high and low levels of the drive signal, it realizes its own on / off control, thereby regulating the energy freewheeling and output on the secondary side.

[0065] The second filter capacitor C2, acting as a filter and energy storage device on the secondary side, is used to rectify, filter, stabilize, and store the induced voltage output from the secondary winding Ns of transformer 30, providing a stable output voltage for the load and assisting in maintaining stable output voltage in ultra-low power mode. Its connection method is as follows: the first plate is connected to the end of the secondary winding Ns of transformer 30 furthest from the drain of the secondary-side switch Q2, directly receiving the electromagnetic energy coupled out by the secondary winding Ns of transformer 30; the second plate is connected to the source of the secondary-side switch Q2 and then grounded together, forming a complete filter circuit.

[0066] Furthermore, the detection input terminal of the secondary-side control module 202 is directly connected to the secondary winding Ns of the transformer 30, eliminating the need for additional sampling components. It can acquire the voltage signal of the secondary winding Ns in real time, thereby detecting the actual output voltage of the secondary-side circuit. Its drive output terminal is connected to the control terminal of the secondary-side switch Q2, used to output a secondary drive signal to control the turn-on and turn-off timing of the secondary-side switch Q2. Simultaneously, the secondary-side control module 202 can couple with the magnetic core through the secondary winding Ns of the transformer 30 to transmit activation signal commands to the primary-side control module 102 and receive sleep signals sent by the primary side, thus completing primary / secondary coordinated control.

[0067] Based on the above, when the system is in normal operating mode, the primary-side switch Q1 turns on and off according to a preset frequency and conduction time. The electromagnetic energy stored in the primary winding Np is coupled to the secondary winding Ns through the magnetic core of the transformer 30. The secondary winding Ns induces an AC voltage of corresponding amplitude. At this time, the secondary-side control module 202 outputs a corresponding secondary drive signal to control the secondary-side switch Q2 to turn on and off according to a timing complementary to that of the primary-side switch Q1. When the primary-side switch Q1 is off, the secondary-side switch Q2 is on. The energy induced in the secondary winding Ns forms a freewheeling circuit through the secondary-side switch Q2 and is transmitted to the second filter capacitor C2. The second filter capacitor C2 rectifies and filters the AC voltage with high-frequency ripple, outputting a stable DC voltage to the load and providing a stable power supply. At the same time, the secondary-side control module 202 collects the output voltage in real time through the connection node with the secondary winding Ns, monitors the load condition, and provides a basis for determining the operating condition.

[0068] When the system enters the ultra-low power mode, the primary-side controller disables the output voltage sampling and loop function, and the switch Q1 is turned off, resulting in extremely low load energy demand. The secondary-side control module 202 only maintains the output voltage detection function, and the secondary-side switch Q2 is in the off state. The second filter capacitor C2 relies on its own energy storage to maintain the stability of the output voltage and prevent the output voltage from dropping rapidly. When the secondary-side control module 202 detects that the output voltage has dropped to a preset threshold, it controls the secondary-side switch Q2 to turn on in advance, generating a characteristic ringing signal. This signal is then sent to the primary side via the magnetic core coupling of the transformer 30 to trigger primary-side energy replenishment. After the output voltage recovers, the secondary-side switch Q2 is turned off again, maintaining the low-power operation of the ultra-low power mode.

[0069] When a load is suddenly connected (switching from no-load / very light-load to full-load), the output voltage drops rapidly. When the secondary-side control module 202 detects that the output voltage is lower than the first preset threshold, it immediately exits the ultra-low power mode. At the same time, it generates a ringing signal by pre-turning on the gate of the secondary-side switch Q2, which is used as an activation signal and transmitted to the primary side through the magnetic core coupling of the transformer 30. After the primary side responds and starts to generate waves and transfer energy to the secondary winding Ns, the secondary-side control module 202 adjusts the secondary drive signal to control the secondary-side switch Q2 to resume normal conduction and turn-off timing. In conjunction with the second filter capacitor C2, it completes rectification and filtering, quickly increasing the output voltage to the full-load rated value to meet the load requirements.

[0070] In other words, regardless of the system's operating condition, the secondary-side control module 202 can detect the output voltage in real time through its connection with the secondary winding Ns. When an abnormal drop in output voltage is detected (switching from no-load / very light-load to full-load, insufficient energy), the operating condition is determined to switch, and an activation signal is generated to provide a basis for primary / secondary coordinated control.

[0071] Based on the above description, the secondary-side control circuit 201 uses only two core components: the secondary-side switch Q2 and the second filter capacitor C2. Its simple structure eliminates the need for complex sampling links or isolation devices, reducing the number of secondary-side hardware components, simplifying the secondary-side circuit topology, and lowering hardware procurement and assembly costs. Furthermore, the secondary-side control module 202 is directly connected to the secondary winding Ns of transformer 30, eliminating the need for additional sampling resistors or coupling devices. It can directly acquire the voltage signal of the secondary winding Ns, thereby detecting real-time changes in the secondary-side output voltage. The sampling path is short, there is no additional signal attenuation, and the sampling accuracy is high, effectively solving the defect of indirect sampling delay on the primary side of existing PSR flyback converters. This direct sampling design enables the secondary-side control module 202 to capture output voltage fluctuations, quickly determine the operating condition switching state, and promptly generate activation signals. This provides accurate and rapid triggering basis for primary / secondary coordinated control, avoiding problems such as excessive output voltage fluctuations and false triggering caused by operating condition detection lag, ensuring the reliability and speed of operating condition switching.

[0072] Optionally, during the process of the control system switching from no-load or very light-load conditions to full-load conditions, the secondary-side control module is used to detect the output voltage through the secondary winding Ns of the transformer 30. When the output voltage is less than a first preset threshold, the secondary-side control module 202 outputs a high-level signal to control the secondary-side switch Q2 to be pre-turned on, so as to generate a first alternating current in the secondary winding Ns of the transformer 30. The transformer 30 is used to generate a first alternating magnetic flux in the magnetic core based on the first alternating current; The auxiliary winding Naux of the transformer 30 is used to induce a first characteristic ringing signal corresponding to the first alternating magnetic flux through magnetic core coupling, and the first characteristic ringing signal is transmitted to the primary side control module 102 as the activation signal.

[0073] In this embodiment, when the control system is in an unloaded condition (no load connected) or an extremely light load condition (load power is much lower than the rated power), the system enters an extremely low power consumption mode. The primary-side switch Q1 is turned off, and energy is no longer input to the primary winding Np of the transformer 30. The secondary-side control module 202 only maintains the output voltage detection function, the secondary-side switch Q2 is turned off, and the second filter capacitor C2 maintains the output voltage basically stable by relying on its own energy storage. At this time, the primary-side control module 102 only maintains the minimum power consumption operation through the VDD voltage holding unit, waiting for the activation signal from the secondary side to trigger activation.

[0074] When a load is suddenly connected (i.e., the system switches from no-load / very light-load conditions to full-load conditions), the energy demand on the secondary side increases sharply. The energy stored in the second filter capacitor C2 alone cannot maintain the stability of the output voltage, causing the output voltage to drop rapidly. At this time, an activation signal is triggered on the secondary side and transmitted to the primary side control module 102 to instruct the primary side to exit the ultra-low power mode and start energy replenishment.

[0075] Based on the above description, in this embodiment, the generation of the activation signal is directly triggered by the secondary-side control module 202: the secondary-side control module 202 directly detects the output voltage without primary-side sampling and feedback. Once the output voltage is lower than the first preset threshold, the secondary-side switch Q2 can be pre-turned on immediately to quickly generate the activation signal. At the same time, the signal transmission relies on the magnetic core coupling of the transformer 30, eliminating the need for signal conversion by isolation devices such as optocouplers. The transmission speed is fast and there is no additional delay, eliminating the inherent control delay of the prior art, realizing a fast response to large dynamic load switching, and effectively avoiding severe drops in output voltage.

[0076] Furthermore, the secondary-side control module 202 is also used to determine whether the control system is in an unloaded or extremely light-load condition based on the sleep signal, and after confirmation by a second preset delay, control the secondary-side control module 202 and the secondary-side circuit 201 to enter an extremely low-power mode. At this time, the system enters the extremely low-power mode.

[0077] In this embodiment, when the control system is under full load, the primary-side switch Q1 operates according to the appropriate frequency and conduction time, transferring energy to the secondary-side winding Ns through the primary winding Np of the transformer 30. The secondary-side switch Q2 conducts in a complementary timing sequence to provide a freewheeling current. The second filter capacitor C2 rectifies and filters the voltage to provide a stable rated voltage to the load. The secondary-side control module 202 continuously monitors the output voltage and monitors the load condition in real time to ensure that the output voltage is adapted to the full load requirements.

[0078] When the load is disconnected (no-load condition) or the load power drops sharply (extremely light load condition), the energy demand on the secondary side decreases significantly. If the primary side continues to generate waveforms normally, it will lead to excess energy on the secondary side and an abnormal rise in output voltage. At this time, the primary side control module controls the primary side switch Q1 to stop invalid waveform generation and enter a low-power state based on the sampled output voltage. It also generates a sleep signal, which is transmitted to the secondary side control module 202 through the transformer. Ultimately, this switches the entire system to an extremely low-power mode, achieving energy saving and output voltage stability.

[0079] Specifically, when the system switches from full load to no load / very light load, the load energy demand decreases sharply. The energy transferred from the primary side to the secondary side cannot be consumed by the load, resulting in excess energy on the secondary side and a rapid increase in output voltage (above the rated output voltage under full load). The primary side control module 201 captures this abnormal voltage rise signal through real-time sampling and initially determines that the system may have entered no load or very light load conditions. To avoid misjudgments caused by instantaneous load fluctuations (such as the load momentarily disconnecting and quickly connecting under full load conditions, which is a normal fluctuation and does not require triggering sleep mode), the primary side control module 102 does not immediately generate an ultra-low power standby command after initially determining the no load / very light load condition. Instead, it initiates a first preset delay and enters the delay confirmation stage. It should be understood that the duration of this first preset delay can both avoid false triggering due to instantaneous fluctuations and quickly respond to the actual change in operating conditions.

[0080] After the first preset delay, the primary-side control module controls the primary-side switch Q1 to turn off and sends a sleep signal to the secondary-side control module through the transformer. Upon receiving the sleep signal and after a second preset delay, the secondary-side control module 202 turns off the secondary-side switch Q2. During the second preset delay, the secondary-side control module 202 continuously monitors the output voltage to ensure it remains within the no-load / light-load threshold range without significant drop. Once the second preset delay ends and the confirmation is successful, the secondary-side control module 202 controls the secondary side to enter an ultra-low power mode, at which point the entire system enters ultra-low power mode.

[0081] As described above, after the primary-side switch Q1 is turned off, the primary side only maintains the signal detection module and the primary-side controller at the lowest power consumption. The secondary-side control module 202 only maintains the output voltage detection function and enables the second filter capacitor C2 to store energy to maintain the output voltage. When the secondary-side switch Q2 is turned off, the entire control system officially enters the ultra-low power consumption mode, completing the smooth switch from full-load condition to no-load / ultra-light-load condition.

[0082] Based on the above description, in this embodiment, when the system enters an unloaded / very light load condition, the primary side receives a command and stops invalid waveform transmission and turns off the switching transistor, no longer transferring excess energy to the secondary side. Therefore, the output voltage can be maintained stably without the need for a virtual load to consume energy. Furthermore, this embodiment eliminates the virtual load, removing the additional losses it causes and improving the system's energy conversion efficiency under unloaded and very light load conditions.

[0083] In one optional implementation, the secondary-side control module 202 includes a secondary-side controller and a secondary-side voltage holding unit; the secondary-side controller is connected to the secondary-side voltage holding unit. When the control system is in an ultra-low power mode, the secondary-side controller is used to send an enable signal to the secondary-side voltage holding unit to start the secondary-side voltage holding unit. The secondary side voltage holding unit is used to detect the output voltage. When the output voltage is less than the second preset threshold, it sends a power replenishment and conduction command to the primary side control module 102 through the transformer 30. After receiving the power replenishment command, the primary-side control module 102 controls the primary-side switch Q1 to be turned on once, so that the output voltage rises back to the preset voltage range corresponding to the ultra-low power mode.

[0084] In this embodiment, when the control system enters the ultra-low power mode, the secondary-side controller recognizes the current operating condition as ultra-low power mode and sends an enable signal to the secondary-side voltage holding unit connected to it. This enable signal is a low-power trigger signal, used only to start the secondary-side voltage holding unit, and does not need to be maintained at a continuous high level, in order to meet the low power requirements of the ultra-low power mode. After receiving the enable signal, the secondary-side voltage holding unit enters the real-time output voltage detection state; when it does not receive the enable signal, the secondary-side voltage holding unit is in a sleep state, does not consume additional energy, and further reduces the power consumption of the system under all operating conditions.

[0085] After the secondary-side voltage holding unit is activated, it detects the secondary-side output voltage without requiring additional sampling components, ensuring detection accuracy while simplifying the structure. The secondary-side voltage holding unit incorporates a built-in power replenishment trigger determination logic, comparing the real-time detected output voltage with a preset second threshold. This second threshold is the minimum maintenance threshold for the output voltage in ultra-low power mode; below this threshold, the output voltage cannot meet the load standby requirements and may trigger a system malfunction. When the secondary-side voltage holding unit detects that the output voltage is less than the second preset threshold, it determines that the current output voltage has dropped to a critical state and immediately triggers primary-side power replenishment, entering the power replenishment turn-on command generation process.

[0086] Upon determining that energy replenishment is needed, the secondary-side voltage holding unit immediately generates an energy replenishment turn-on command. This command is an energy replenishment control signal in the ultra-low power mode. The command means that the primary-side control module 102 controls the primary-side switch Q1 to turn on once, replenishing a small amount of energy to the secondary side, causing the output voltage to rise back to the preset voltage range corresponding to the ultra-low power mode. After energy replenishment is completed, the system immediately returns to sleep mode. It is worth noting that the signal of this energy replenishment turn-on command is ensured to match the detection logic in the primary-side ultra-low power mode, while avoiding confusion with other commands to prevent accidental activation or sleep switching, thus ensuring control reliability.

[0087] Consistent with the transmission logic of the activation signal, the transmission of the power-on command relies on the electromagnetic coupling characteristics of the common magnetic core of the primary, secondary, and auxiliary windings of transformer 30. No additional optocouplers or other isolation devices are required, which fits the design of the PSR flyback converter with its simple topology and lack of additional isolation components, while ensuring the isolation and reliability of signal transmission.

[0088] After the secondary-side voltage holding unit generates a power-on command, it transmits the command to the secondary-side controller. The secondary-side controller then controls the secondary-side switch Q2 to output a dedicated characteristic drive signal (short-time, single pre-on action). After the secondary-side switch Q2 is short-time pre-on, a third alternating current is generated in the secondary winding Ns of transformer 30. This current excites a third alternating magnetic flux in the core of transformer 30. Through the core coupling effect, this third alternating magnetic flux induces a corresponding third characteristic ringing signal in the primary-side auxiliary winding Naux. This signal is filtered by the primary-side power supply diode D1 and the first filter capacitor C1 to remove noise, and then transmitted to the primary-side control module 102 through the connection node between the auxiliary winding Naux and the primary-side control module 102. Upon receiving the power-on command, the primary-side control module 102, in conjunction with the current ultra-low power mode operating state, executes a power-on action: controlling the primary-side switch Q1 to conduct once, so that the output voltage recovers to the preset range of the ultra-low power mode, avoiding the increase in power consumption caused by continuous conduction.

[0089] After the primary-side switch Q1 is turned on once, the primary-side input power supply stores a small amount of energy in the transformer 30 core through the primary winding Np. This energy is then transferred to the secondary winding Ns via core coupling and rectified and filtered by the second filter capacitor C2 to replenish the stored energy. When the output voltage rises back to the preset voltage range corresponding to the ultra-low power mode (above the second preset threshold), the primary-side switch Q1 is automatically turned off, and the primary-side control module 102 returns to the lowest power consumption operating state in the ultra-low power mode, waiting for the next energy replenishment command. At the same time, the secondary-side voltage holding unit continuously monitors the output voltage. When it detects that the output voltage has risen back to the preset range, it stops generating the energy replenishment turn-on command, returns to the real-time monitoring state, and waits for the output voltage to drop back to the second preset threshold to trigger the next energy replenishment.

[0090] Based on the above description, the secondary-side voltage holding unit in this embodiment detects the output voltage in real time in the ultra-low power mode. When the voltage drops to the second preset threshold, it promptly triggers a single energy replenishment on the primary side to replenish a small amount of energy to the secondary side, so that the output voltage can quickly recover to the preset range of the ultra-low power mode. This effectively avoids the problem of continuous output voltage drop and ensures that the output voltage in the ultra-low power mode is always stable within the reasonable range required for load standby, thereby improving the stability and reliability of the system's sleep state.

[0091] Furthermore, the secondary-side control module 202 also includes a discharge unit; the secondary-side controller is also connected to the discharge unit. The voltage holding unit is also used to send a discharge command to the secondary controller when the output voltage is greater than a third preset threshold. The secondary-side controller is used to control the operation of the discharge module according to the discharge command, so that the output voltage drops to a preset voltage range corresponding to the ultra-low power mode.

[0092] In this embodiment, the secondary voltage holding unit may have built-in overvoltage determination logic, which compares the real-time detected output voltage with a preset third preset threshold. The third preset threshold is the maximum limit threshold of the output voltage in the ultra-low power mode. When the output voltage exceeds this threshold, it exceeds the preset range of the ultra-low power mode, and discharge control needs to be activated.

[0093] When the secondary-side voltage holding unit detects that the output voltage exceeds a third preset threshold, it determines that the current output voltage is abnormally high and needs to dissipate excess energy. It then sends a dissipation command to the connected secondary-side controller. This command is a voltage over-limit control signal in ultra-low power mode, instructing the secondary-side controller to activate the dissipation unit, dissipate excess energy on the secondary side, and reduce the output voltage to the preset voltage range corresponding to ultra-low power mode. Upon receiving the dissipation command, the secondary-side controller responds and executes a driving action: it outputs a driving signal to the connected dissipation unit, controlling the dissipation unit to switch from sleep mode to working mode, thus activating the energy dissipation function.

[0094] It is worth noting that the discharge power of the discharge unit is precisely matched, and it can only consume excess energy that exceeds the preset voltage range of the ultra-low power mode, without excessive energy consumption causing a significant voltage drop. At the same time, the discharge unit adopts a low-power design, and its own energy loss during operation is extremely low, avoiding the introduction of additional power consumption burden due to discharge regulation.

[0095] During the operation of the discharge unit, the secondary-side voltage holding unit continuously monitors the output voltage and provides real-time feedback on voltage changes to the secondary-side controller. When the output voltage drops to the preset voltage range corresponding to the ultra-low power mode (i.e., below the third preset threshold and above the second preset threshold), the secondary-side voltage holding unit immediately stops sending discharge commands to the secondary-side controller and sends back a normal voltage signal. After receiving the normal voltage signal, the secondary-side controller stops outputting drive signals to the discharge unit, controls the discharge unit to stop working, and returns to sleep mode. At this time, the output voltage stabilizes within the preset range of the ultra-low power mode.

[0096] Based on the above description, the bleeder unit and the secondary-side voltage holding unit work together to form a complete bidirectional control closed loop: when the output voltage is less than the second preset threshold, the secondary-side voltage holding unit triggers energy replenishment to boost the voltage; when the output voltage is greater than the third preset threshold, the bleeder unit triggers discharge to reduce the voltage, ensuring that the output voltage remains stable within the preset range corresponding to the ultra-low power mode. This improves the stability of the output voltage in the ultra-low power mode, ensuring the standby reliability of the load and the safety of the secondary-side devices.

[0097] In one alternative implementation, refer to Figure 2 The primary-side control module 102 includes a signal detection module and a primary-side controller. The primary-side controller is connected to the signal detection module and the control terminal of the primary-side switch Q1. The primary-side controller is used to control the primary-side switch Q1 to turn on at the lowest operating frequency when the control system switches to the no-load condition or the extremely light-load condition, and to turn off the primary-side switch Q1 after maintaining the lowest operating frequency for a first preset delay, and to transmit a sleep signal to the secondary-side controller through the transformer 30. The secondary-side controller is used to send an enable signal to the secondary-side voltage holding unit when the sleep signal is detected, so as to start the secondary-side voltage holding unit and make the fluctuation of the output voltage less than a preset fluctuation range when the system enters the ultra-low power mode.

[0098] When the control system is in the ultra-low power mode and the system is connected to a load, the secondary-side controller is used to shut down the secondary-side voltage holding unit when the drop value of the output voltage is greater than a preset detection threshold, and to pre-turn on the secondary-side switch Q2 to generate a first characteristic ringing signal in the transformer 30, which is then transmitted to the signal detection module of the primary-side control module 102 as an activation signal. The primary-side controller is used to control the primary-side switch Q1 to turn on at a preset operating frequency after the signal detection module receives the activation signal, so that the system exits the ultra-low power mode.

[0099] In this embodiment, the signal detection module is used to receive various characteristic signals transmitted by the secondary side through the magnetic core coupling of the transformer 30, and to perform preliminary filtering and identification of the signals to eliminate noise interference, and then transmit the identified valid signals to the primary side controller.

[0100] One end of the primary-side controller is connected to the signal detection module to receive the valid signals transmitted by it; the other end is connected to the control terminal of the primary-side switch Q1, and outputs a drive signal to control the conduction, turn-off and operating frequency of the primary-side switch Q1; at the same time, it can transmit a sleep signal (when switching from no-load / very light-load to sleep) to the secondary-side controller through the magnetic core coupling of transformer 30, realizing bidirectional signal interaction between the primary and secondary-side controllers.

[0101] In this embodiment, the primary-side controller adjusts the operating frequency of the primary-side switch Q1 to a preset minimum operating frequency. This minimum operating frequency is the lowest power consumption frequency under no-load / very light-load conditions, maintaining only the primary-side control module 102 at its lowest power consumption to avoid unnecessary energy loss from invalid waveforms. Simultaneously, it controls the primary-side switch Q1 to maintain operation at this minimum operating frequency for a first preset delay. This first preset delay ensures that sleep triggering only corresponds to actual no-load / very light-load conditions, preventing the system from mistakenly entering a very low-power mode and improving the reliability of sleep triggering. Furthermore, the brief frequency reduction operation avoids primary-side voltage fluctuations caused by the direct turn-off of the primary-side switch Q1, ensuring the stability of the primary-side circuit.

[0102] After the first preset delay ends, the primary side controller confirms that there is no fluctuation in the operating condition, controls the primary side switch Q1 to turn off, and stops inputting energy to the primary winding Np of transformer 30; at the same time, the primary side controller transmits a sleep signal to the secondary side controller through the magnetic core coupling of transformer 30. This signal is used to indicate that the primary side has completed the sleep preparation and instructs the secondary side to start the ultra-low power mode.

[0103] The secondary-side controller monitors the induced signal of the secondary winding Ns of transformer 30 in real time. When it detects the sleep signal transmitted from the primary side, it confirms that the system is about to enter the ultra-low power mode and sends an enable signal to the secondary-side voltage holding unit to start the secondary-side voltage holding unit, so that the fluctuation of the output voltage when the system enters the ultra-low power mode is less than the preset fluctuation range. At this time, the secondary-side switch Q2 is turned off, the discharge unit is in sleep state, the second filter capacitor C2 maintains the output voltage by its own energy storage, the primary-side switch Q1 is turned off, and the primary-side control module 102 only maintains the signal detection module and its own minimum power consumption operation. The entire control system officially enters the ultra-low power mode. During the operation of the system, when the system is connected to a load (i.e., switching from the ultra-low power mode to the full load / normal load condition), the load consumes a large amount of energy instantly, and the energy stored in the second filter capacitor C2 is released rapidly, causing the secondary-side output voltage to drop rapidly. The secondary-side controller monitors this output voltage change in real time and monitors the drop value of the output voltage.

[0104] The preset fluctuation range is the maximum allowable fluctuation of the output voltage when the system enters the ultra-low power sleep mode. It should be understood that after the system enters the ultra-low power mode, the primary side has shut down the control loop and no longer actively detects the output voltage. However, the output voltage cannot drop too quickly, otherwise the load will restart, reset, or malfunction. At this time, the secondary side voltage holding unit is responsible for stabilizing the output voltage.

[0105] The secondary-side controller compares the output voltage drop with a preset detection threshold. If the drop exceeds the threshold, it is determined that a real load is connected, and system activation is triggered. At this time, the secondary-side controller shuts down the secondary-side voltage holding unit. Furthermore, the secondary-side controller pre-turns on the secondary-side switch Q2, generating a first alternating current in the secondary winding Ns of transformer 30. This current excites the magnetic core to generate a first alternating magnetic flux. Through the magnetic core coupling, a first characteristic ringing signal (i.e., activation signal) is induced in the primary-side auxiliary winding Naux. This activation signal, after being filtered by the primary-side power supply diode D1 and the first filter capacitor C1 to remove noise, is transmitted to the signal detection module of the primary-side control module 102.

[0106] After receiving the activation signal, the signal detection module identifies it and transmits it to the primary-side controller. After confirming the activation request, the primary-side controller immediately adjusts the primary drive signal to control the primary-side switch Q1 to turn on at a preset operating frequency. At the same time, the primary-side switch Q1 operates according to the on-time of the adapted load, and the secondary-side controller controls the secondary-side switch Q2 to restore the normal on / off timing. The output voltage quickly rises back to the rated range, and the system exits the ultra-low power mode and enters the normal operating mode.

[0107] The preset operating frequency is a fixed frequency used when the primary-side switching transistor resumes operation after the system is woken up from the ultra-low power sleep mode.

[0108] Based on the above description, when the system's ultra-low power mode is triggered, the primary-side controller first reduces the switching frequency to the minimum, maintains it for the first preset delay, and then turns it off, rather than turning it off directly. This avoids a sharp drop in the secondary-side voltage caused by a sudden interruption of primary-side energy, and ensures that the output voltage smoothly transitions to the preset range of the ultra-low power mode. When activated, the primary-side controller drives the switching transistor to conduct at a preset operating frequency to achieve rapid energy replenishment. Combined with the normal timing of the secondary-side switching transistor Q2 and the filtering effect of the second filter capacitor C2, the output voltage quickly rises back to the rated value, avoiding voltage drop when the load is connected and ensuring normal load startup. At the same time, the secondary-side voltage holding unit is turned off first during activation to avoid conflict between energy replenishment and activation energy replenishment, further improving voltage stability.

[0109] Furthermore, when the system transitions from a full-load condition to an unloaded or very light-load condition, the primary-side controller is used to gradually reduce the current operating frequency of the primary-side switch Q1 to a preset switching frequency threshold. The primary-side controller is also used to control the primary-side circuit and the primary-side control module 102 to enter an ultra-low power mode after the switching frequency of the primary-side switch Q1 is lower than a preset switching frequency threshold and continues for a first preset duration. After the primary-side circuit and the primary-side control module 102 enter the ultra-low power mode, the secondary-side controller is used to control the secondary-side circuit and the secondary-side control module 202 to enter the ultra-low power mode if the switching frequency of the primary-side switch Q1 is continuously detected to be lower than the preset switching frequency threshold within a second preset time period. At this time, the system enters the ultra-low power mode.

[0110] In this embodiment, when the system switches from full load to very light load, the energy demand on the secondary side decreases sharply, and the energy transferred from the primary side to the secondary side cannot be consumed by the load, resulting in an abnormal rise in the output voltage on the secondary side. After the primary side controller detects the abnormal voltage, it recognizes that the system has switched from full load to very light load and initiates the process of reducing the operating frequency of the primary side switching transistor Q1.

[0111] It is worth noting that in this embodiment, the primary-side controller does not directly cut off the primary-side switch Q1, but gradually reduces the current operating frequency of the primary-side switch Q1 (from the full-load rated frequency to near the preset switching frequency threshold). This avoids sudden frequency changes that could cause a sharp change in the magnetic flux of the transformer 30 core, leading to problems such as primary / secondary voltage spikes and electromagnetic interference. Simultaneously, the primary-side controller controls the primary-side switch Q1 to maintain on / off operation at each reduced operating frequency level until the frequency drops to the preset switching frequency threshold. Then, it maintains the reduced operating frequency for a first preset duration. The core function of this first preset duration is to provide a buffer time for the primary-side circuit, adapting to the energy demands of extremely light load conditions, while filtering instantaneous load fluctuations to prevent false sleep caused by rapid frequency reduction and insufficient adaptation to the operating conditions.

[0112] Furthermore, during the operation of the primary-side switch Q1 at a reduced operating frequency, the primary-side controller monitors its own output switching frequency in real time and continuously compares it with a preset switching frequency threshold. The preset switching frequency threshold is the critical frequency for the primary side to enter the ultra-low power mode. When it is below this threshold, the energy output of the primary-side switch Q1 can match the minimum requirements of the ultra-light load condition.

[0113] It is worth noting that when the primary-side controller detects that the switching frequency of the primary-side switch Q1 is lower than a preset switching frequency threshold, it does not immediately trigger sleep mode. Instead, it initiates a first preset duration of delay confirmation to continuously monitor whether the switching frequency remains below the threshold. If, within the first preset duration, the switching frequency remains below the preset switching frequency threshold without significant rebound, confirming that the system is indeed stably operating under extremely light load conditions rather than experiencing instantaneous fluctuations, the primary-side controller determines that the primary-side sleep mode conditions are met. At this time, the primary-side controller executes a sleep trigger command, controlling the primary-side circuit and the primary-side control module 102 to enter an extremely low power consumption mode. The primary-side switch Q1 stops its normal on / off operation and remains in the off state. The primary-side control module 102 only retains the minimum power consumption monitoring function, stops transferring energy to the secondary side, and only maintains its own extremely low power consumption operation, waiting for the activation signal or power replenishment command from the secondary side.

[0114] While the primary side enters the ultra-low power mode, the secondary side controller indirectly obtains the actual operating frequency of the primary side switch Q1 by detecting the induced signal of the secondary winding Ns of transformer 30. Furthermore, the secondary side controller continuously monitors the operating frequency of the primary side switch Q1 for a second preset duration to confirm whether the frequency of the primary side switch Q1 remains below a preset switching frequency threshold. If, within the second preset duration, the switching frequency of the primary side switch Q1 is continuously detected to be below the preset switching frequency threshold, and there are no signs of activation, the secondary side controller determines that the primary side has stably entered sleep mode, thus meeting the secondary side sleep condition. It should be understood that this second preset duration is used to ensure that both the primary and secondary sides enter sleep mode, avoiding a situation where the primary side has not yet stably entered sleep mode while the secondary side has, leading to the inability to transmit subsequent power replenishment commands to the primary side and abnormal output voltage.

[0115] After confirming the second preset delay duration is correct, the secondary-side controller executes the sleep trigger command, controlling the secondary-side circuit (secondary-side switch Q2, second filter capacitor C2, etc.) and the secondary-side control module 202 to enter the ultra-low power mode. The secondary-side switch Q2 remains off. The secondary-side controller disables unnecessary detection functions and only maintains minimum output voltage detection. At the same time, the secondary-side controller sends an enable signal to the secondary-side voltage holding unit to start the secondary-side voltage holding unit, which is used for energy replenishment triggering when the output voltage drops in the ultra-low power mode.

[0116] At this point, both the primary and secondary sides have entered the ultra-low power mode, and the entire control system has officially entered the complete ultra-low power mode, maintaining ultra-low power operation. The output voltage is detected in real time only through the secondary side voltage holding unit to adapt to the minimum energy requirements of extremely light load conditions.

[0117] Specifically, refer to Figure 3 This illustrates the dynamic switching process of the flyback converter control system from normal operating mode to ultra-low power sleep mode.

[0118] When the system is in normal operating mode, if the load suddenly switches to no load (or switches from full load to very light load), the Load (load switch trigger) signal drops rapidly from high level to low level, indicating a sharp drop in energy demand. At this time, the primary-side control module 102 will immediately start to reduce the operating frequency of the switching transistor to avoid excessive energy causing output voltage overshoot.

[0119] The frequency of the drain-source voltage (Vds) of the primary-side switch Q1 gradually decreases to adapt the primary side to extremely light load conditions. When the frequency falls below a preset switching frequency threshold and remains below it for a first preset duration, the primary side determines that the system has entered a stable extremely light load condition and triggers primary-side sleep mode. At this point, the Vds waveform completely disappears, indicating that the primary-side switch Q1 is completely turned off and stops transferring energy to the transformer 30.

[0120] During the initial stage of primary-side frequency reduction, the secondary-side output voltage (Vo) may overshoot due to excess energy, exceeding the overshoot threshold Vo_th2. The secondary side will continuously verify this state within a second preset time period (e.g., if the primary-side switching frequency is continuously lower than the preset switching frequency threshold and the output voltage is continuously higher than Vo_th2), and trigger secondary-side sleep mode after confirmation. When both the primary and secondary sides enter sleep mode, the system enters ultra-low power sleep mode.

[0121] At this point, the output voltage no longer depends on the primary side waveform for maintenance, but is determined by the energy storage of the output capacitor and the secondary side voltage holding unit. The waveform is a slowly decaying DC voltage.

[0122] Optionally, the primary-side control module 102 further includes a primary-side power supply voltage holding unit and a primary-side voltage detection unit; and the primary-side controller is connected to both the primary-side power supply voltage holding unit and the primary-side voltage detection unit. When the system is in an ultra-low power mode, the primary-side controller is used to turn off the primary-side switch Q1 and turn on the primary-side power supply voltage holding unit and the primary-side voltage detection unit. The primary-side power supply voltage holding unit is used to provide a minimum operating voltage to the primary-side controller when the system is in an ultra-low power mode and the primary-side switch Q1 is in the off state. When the primary side voltage detection unit detects that the supply voltage of the primary side controller drops to a preset minimum sustaining threshold, the primary side controller is used to control the primary side switch Q1 to turn on with the minimum sustaining power so as to supply power to the primary side controller through the auxiliary winding Naux of the transformer 30. When the voltage detection unit detects that the supply voltage of the primary side controller rises back to the preset maximum maintenance threshold, the primary side controller controls the primary side switch Q1 to turn off.

[0123] In this embodiment, the primary-side power supply voltage holding unit provides a minimum operating voltage to the primary-side controller in ultra-low power mode, with the primary-side switch Q1 off. This maintains the primary-side controller's ultra-low power standby, ensuring it can normally receive secondary-side signals and control related units, without participating in power supply during normal operation. Its connection is unidirectional with the primary-side controller and is only turned on / off by the primary-side controller's control signals.

[0124] The primary-side voltage detection unit is used to detect the supply voltage of the primary-side controller in real time, capture voltage dips and rises, and feed the detection results back to the primary-side controller in real time, providing a basis for the energy replenishment and turn-on / off of the primary-side switch Q1. Its connection is bidirectional with the primary-side controller; one end detects the supply voltage of the primary-side controller, and the other end transmits the detection signal to the primary-side controller to receive its turn-on / off control.

[0125] Reference Figure 4 During the continuous ultra-low power mode, the energy stored in the primary side power supply voltage holding unit or the residual energy on the primary side will be gradually consumed, resulting in a decrease in its output operating current, which in turn causes the power supply voltage of the primary side controller to drop slowly. The primary side voltage detection unit captures this drop trend in real time. When it detects that the power supply voltage VDD of the primary side controller drops to the preset minimum holding threshold VDD_th1, it immediately sends an undervoltage feedback signal to the primary side controller.

[0126] After receiving the feedback signal, the primary-side controller determines that the current power supply to the primary-side controller is insufficient and temporary power replenishment needs to be initiated to avoid abnormal operation. Subsequently, the primary-side controller controls the primary-side switch Q1 to conduct with the minimum sustaining power. The minimum sustaining power is different from the power output in normal operation mode and active mode. It can only provide a small amount of power replenishment to the primary-side controller, which is enough to restore the supply voltage to a safe range, avoiding energy loss caused by excessive power replenishment, and balancing power supply stability and low power consumption.

[0127] During the process of primary-side switch Q1 being turned on to replenish power at the minimum sustaining power, the primary-side voltage detection unit continuously monitors the supply voltage VDD of the primary-side controller and provides real-time feedback on the voltage recovery status to the primary-side controller. When it detects that the supply voltage VDD of the primary-side controller has recovered to the preset maximum sustaining threshold VDD_th2, it immediately sends a normal voltage feedback signal to the primary-side controller.

[0128] Upon receiving the feedback signal, the primary-side controller immediately determines that the current power supply to the primary-side controller is sufficient and no further energy replenishment is needed. It then controls the primary-side switch Q1 to turn off, stopping the transfer of energy to the auxiliary winding Naux, and the energy replenishment operation ends. At this time, the primary-side power supply voltage holding unit returns to normal and continues to provide the primary-side controller with the minimum operating voltage. The primary-side voltage detection unit continues to monitor the power supply voltage in real time, waiting to trigger energy replenishment when the power supply voltage drops again.

[0129] Based on the above description, in this embodiment, the primary-side power supply voltage holding unit provides a continuous minimum operating voltage to the primary-side controller, ensuring that it can stably standby in ultra-low power mode; the primary-side voltage detection unit monitors the power supply voltage in real time, and when the voltage drops to the minimum holding threshold, it promptly triggers the primary-side switch Q1 to temporarily replenish power, ensuring that the power supply voltage of the primary-side controller is always maintained within a safe range, avoiding problems such as hibernation failure and inability to activate caused by insufficient power supply, and greatly improving the stability and reliability of ultra-low power mode.

[0130] Furthermore, the primary-side controller controls the primary-side switch Q1 to replenish power with the minimum sustaining power. The replenishing power is only sufficient to meet the replenishing needs of the primary-side controller, without transferring excess energy, thus reducing energy loss during the replenishment process. At the same time, the primary-side power supply voltage holding unit only provides the minimum operating voltage and has extremely low energy consumption. The two work together to achieve stable power supply to the primary-side controller and strictly control the overall power consumption of the primary side, further optimizing the low-power performance of the system in the ultra-low power mode.

[0131] In one optional implementation, the secondary-side control module 202 further includes a secondary-side voltage detection unit, which is connected to the secondary-side controller; the secondary-side voltage detection unit is also connected to the system's output port for detecting the output voltage. When the secondary-side control module enters an ultra-low power mode, the secondary-side controller enables the secondary-side voltage holding unit and the secondary-side voltage detection unit. The secondary-side controller is used to send a power replenishment signal to the primary-side controller through the transformer 30 when the secondary-side voltage detection unit detects that the output voltage has dropped to a preset voltage threshold. After receiving the power replenishment signal, the primary-side controller turns on the primary-side switch Q1 until the output voltage rises back to the preset voltage threshold, at which point it turns off the primary-side switch Q1.

[0132] In this embodiment, the secondary-side voltage detection unit is used to detect the secondary-side output voltage as the basis for determining output voltage drop. It transmits the real-time detected output voltage signal to the secondary-side controller, providing support for the generation of the replenishment signal. It operates only in ultra-low power mode when the primary-side switch Q1 is off; in normal operating mode, it is in a dormant state to reduce energy consumption. Its connection is bidirectional: one end is directly connected to the secondary winding Ns of transformer 30, directly acquiring the DC output voltage from the secondary winding Ns and filtered by the second filter capacitor C2. This results in a short sampling path and no signal attenuation, ensuring detection accuracy. The other end is connected to the secondary-side controller, receiving both the enable / disable signal from the secondary-side controller and providing real-time feedback of the detected output voltage data to the secondary-side controller.

[0133] In the embodiments of this application, reference is made to Figure 5 When the system enters the ultra-low power mode, after the primary-side controller controls the primary-side switch Q1 to turn off, the primary side stops transferring energy to the secondary side. The secondary-side controller recognizes the current operating condition and performs an enabling action: sending enable signals to the secondary-side voltage detection unit and the secondary-side voltage holding unit respectively, starting the two units to enter the working state. At this time, the secondary-side controller itself maintains low power operation, only receiving feedback signals from the secondary-side voltage detection unit and generating relevant control commands.

[0134] After receiving the enable signal, the secondary-side voltage detection unit starts the output voltage detection function. Due to its direct connection with the secondary winding Ns of transformer 30, it can acquire the secondary-side output voltage in real time. During the detection process, the secondary-side voltage detection unit continuously feeds back the real-time acquired output voltage data to the secondary-side controller.

[0135] After receiving the real-time output voltage data from the secondary-side voltage detection unit, the secondary-side controller compares it with a preset voltage threshold. If the real-time detected output voltage V0 is lower than the preset voltage threshold V, the controller will take action. 0— When the output voltage drops to a critical state, it is determined that the secondary-side power transistor needs to be pre-turned on to generate a replenishment signal. This requires initiating primary-side replenishment to prevent the load from malfunctioning due to continued voltage drops or system erroneous activation. Specifically, this replenishment signal instructs the primary-side control module 102 to turn on the primary-side switch Q1, replenishing energy to the secondary side and causing the output voltage to rise back to a preset voltage threshold, maintaining voltage stability in the ultra-low power mode.

[0136] After the secondary-side controller generates the energy replenishment signal, it controls the secondary-side switch Q2 to perform a short-time pre-turn-on action, converting the energy replenishment signal into a characteristic electrical signal that can be transmitted through magnetic core coupling: after the secondary-side switch Q2 is turned on for a short time, an alternating current is generated in the secondary winding Ns of transformer 30. This current excites the magnetic core of transformer 30 to generate an alternating magnetic flux. Through the magnetic core coupling effect, a corresponding characteristic ringing signal is induced in the primary-side auxiliary winding Naux.

[0137] The characteristic ringing signal is filtered by the primary-side power supply diode D1 and the first filter capacitor C1 to remove noise, and then transmitted to the signal detection module of the primary-side control module 102. The signal detection module quickly identifies the signal as a power replenishment signal and transmits it to the primary-side controller to complete the transmission of the power replenishment signal.

[0138] After receiving the energy replenishment signal from the signal detection module, the primary-side controller responds to the energy replenishment request and executes the energy replenishment action: it controls the primary-side switch Q1 to turn on, and the primary-side input power supply inputs energy to the primary winding Np of transformer 30 through the primary-side switch Q1. This energy is transferred to the secondary winding Ns through magnetic core coupling. After being rectified and filtered by the second filter capacitor C2, it replenishes the stored energy in the capacitor, thereby increasing the secondary-side output voltage. At this time, the conduction time of the primary-side switch Q1 is determined by the recovery of the secondary-side output voltage, rather than a fixed time, to ensure accurate energy replenishment and avoid excessive energy replenishment.

[0139] During the energy replenishment process of the primary-side switch Q1 being turned on, the secondary-side voltage detection unit continuously monitors the secondary-side output voltage and feeds back the voltage recovery data to the secondary-side controller in real time. The secondary-side controller continuously compares the real-time output voltage with the preset voltage threshold. When it detects that the output voltage has recovered to the preset voltage threshold, it determines that the energy replenishment is complete and sends an energy replenishment stop signal to the primary-side controller through the magnetic core coupling of transformer 30.

[0140] After receiving the energy replenishment stop signal, the primary-side controller controls the primary-side switch Q1 to turn off, stopping the transfer of energy to the secondary side, and the energy replenishment process officially ends. At this time, the secondary-side output voltage stabilizes at the preset voltage threshold, the energy stored in the second filter capacitor C2 recovers to a reasonable range, the secondary-side voltage detection unit continues to detect the output voltage in real time, the secondary-side voltage holding unit maintains its working state, and the secondary-side controller returns to low-power standby, waiting for the next output voltage drop to trigger the energy replenishment process again, forming a cyclic regulation.

[0141] Based on the above description, in this embodiment, after the primary-side switch Q1 is turned off, the secondary-side controller simultaneously enables the secondary-side voltage detection unit and the secondary-side voltage holding unit, avoiding response delays caused by detection lag or insufficient energy replenishment preparation. Simultaneously, the secondary-side voltage detection unit adopts a real-time detection-real-time feedback mode. Once the voltage is detected to drop to a preset threshold, the secondary-side controller can immediately generate an energy replenishment signal, which is quickly transmitted to the primary side to trigger the energy replenishment action. This avoids the output voltage remaining below the preset threshold for extended periods, ensuring stable power supply to the load in extremely low-power mode, improving the reliability of load standby, and preventing problems such as abnormal load standby and data loss due to excessively low voltage. It is particularly suitable for small and medium-power electrical equipment with high requirements for standby voltage stability.

[0142] In one example, refer to Figure 6 The output shows the two power replenishment processes of the PS flyback converter in sleep mode: In the first power replenishment (VDD hold-triggered, T1 stage), the primary-side supply voltage (VDD) slowly drops to the preset minimum hold-up threshold VDD_th due to its own power consumption, triggering the primary-side VDD hold-up mechanism. The drain-source voltage (Vds) of the primary-side switch Q1 generates a brief waveform, which replenishes power to the primary-side control module 102 through the auxiliary winding Naux of transformer 30, causing the VDD voltage to rise again. The duration of this process is T1, which is the cycle in which the primary side completes one VDD power replenishment.

[0143] The second energy replenishment (Vo hold trigger, T2 stage): Due to load leakage, the secondary-side output voltage (Vo) slowly drops to the preset voltage threshold Vo_th, triggering the secondary-side Vo hold mechanism. The secondary-side controller briefly pre-turns on the secondary-side switch Q2 (SRG), generating a ringing signal and sending an energy replenishment command to the primary side. The primary-side switch Q1 then briefly emits a waveform again, replenishing energy to the secondary side, causing the Vo voltage to rise again. The duration of this process is T2, which is the cycle of one Vo energy replenishment triggered on the secondary side.

[0144] Optionally, when the system is in an ultra-low power mode and the secondary-side voltage detection unit detects that the output voltage has dropped to the secondary activation threshold voltage, the secondary-side controller controls the secondary-side circuit and the secondary-side control module 202 to exit the ultra-low power mode, and pre-turns on the secondary-side switch Q2 to generate a first characteristic ringing signal in the transformer 30 as an activation signal, which is then transmitted to the primary-side controller. The primary-side controller is used to control the primary-side circuit and the primary-side control module 102 to exit the ultra-low power mode when it receives the activation signal, waits for a preset primary detection shielding time, and identifies the ringing signal within a preset activation signal identification window. It then controls the primary-side switch Q1 to turn on with a preset operating frequency and duty cycle so that the output voltage returns to the normal operating range.

[0145] In this embodiment, the secondary activation threshold voltage is lower than the preset voltage threshold for energy replenishment in the ultra-low power mode (only energy replenishment is triggered, not activated) and lower than the minimum voltage required for normal standby of the load. Specifically, when the output voltage drops to this threshold, the load can no longer maintain normal standby by energy replenishment on the primary side alone. The system needs to completely exit the ultra-low power mode to provide sufficient energy to the load in normal working condition and avoid load abnormalities.

[0146] When the secondary-side voltage detection unit detects a continuous drop in output voltage, eventually falling to the secondary activation threshold voltage, it immediately sends a feedback signal to the secondary-side controller indicating that the voltage has dropped to the activation threshold, thus explicitly triggering the activation requirement. The secondary-side controller sends activation signals to each component of the secondary-side circuit and the secondary-side control module 202, controlling each component to exit the ultra-low power sleep state and resume normal operation: the secondary-side voltage holding unit stops working, the secondary-side voltage detection unit is disabled, and the secondary-side controller itself also exits the low-power state and enters normal operation mode.

[0147] The secondary-side controller synchronously controls the secondary-side switch Q2 to perform a pre-turn-on action. Through the short-term pre-turn-on of the secondary-side switch Q2, a first alternating current is generated in the secondary winding Ns of transformer 30. This current excites the core of transformer 30 to generate a first alternating magnetic flux. Relying on the coupling characteristics of the core, a first characteristic ringing signal is induced in the primary-side auxiliary winding Naux.

[0148] After receiving the activation signal, the primary controller first enters a preset primary detection shielding period. This period is a short delay time, the purpose of which is to filter out noise interference generated during the transmission of the activation signal and false signals caused by signal attenuation, so as to prevent the primary controller from misidentifying the interference signal as a valid activation signal and causing false activation.

[0149] After the primary detection shielding period ends, the primary-side controller initiates a preset activation signal recognition window. This window is a signal recognition interval of fixed duration. Only within this interval will the primary-side controller continuously recognize the signals transmitted by the signal detection module and determine whether they are valid activation signals (i.e., whether they completely match the characteristics of the first characteristic ringing signal). If a ringing signal matching the characteristics is continuously recognized within the recognition window, it is determined to be a valid activation request, and the primary-side activation process is initiated. If no valid signal is recognized, or the recognized signal does not match the characteristics, it is determined to be an interference signal, and the primary side continues to maintain an extremely low power consumption mode to avoid false activation.

[0150] When the primary-side controller confirms the recognition of a valid activation signal within the activation signal recognition window, it immediately executes the primary-side activation action, controlling the primary-side circuit and control module to exit the ultra-low power mode. Among these actions, the primary-side power supply voltage holding unit stops working, the primary-side voltage detection unit switches to the detection frequency of the normal working mode, and the signal detection module restores normal signal reception and recognition efficiency.

[0151] After the primary side is activated, the primary side controller controls the primary side switch Q1 to conduct at a preset operating frequency and duty cycle. Through the high-frequency, high-duty-cycle conduction action, the primary side input power supply quickly transfers a large amount of energy to the primary winding Np of transformer 30. This energy is quickly transferred to the secondary winding Ns through magnetic core coupling. After being rectified and filtered by the second filter capacitor C2, it provides sufficient energy to the load and quickly compensates for the drop in output voltage.

[0152] The secondary-side controller works synchronously and collaboratively, controlling the secondary-side switch Q2 to achieve complementary conduction and freewheeling with the primary-side switch Q1 according to the timing sequence of the normal operating mode. The secondary-side voltage detection unit continuously monitors the output voltage and feeds it back to the primary / secondary-side controllers in real time. When the primary-side controller indirectly obtains through the signal detection module that the output voltage has returned to the normal operating range (i.e., the rated supply voltage range of the load), it gradually adjusts the operating frequency and duty cycle of the primary-side switch Q1, switching it from the maximum state to the rated state adapted to the current load, maintaining stable output voltage. The entire system then officially exits the ultra-low power mode, resumes normal operation, and completes the full activation process.

[0153] Reference Figure 7 This illustrates the dynamic activation process of the PSR flyback converter control system switching from an ultra-low power sleep mode to a normal operating mode. The process includes: Load connection and voltage drop (T1 stage): When a load is suddenly connected (the Load signal changes from low to high), the output voltage Vo is maintained only by the output capacitor and then drops rapidly. When Vo drops to the secondary activation threshold Vwake, the activation process is triggered.

[0154] Secondary-side activation signal transmission (secondary activation stage): The secondary-side controller exits sleep mode and pre-turns on the gate (SRG) of the secondary-side switch Q2, generating a characteristic ringing signal in transformer 30. This ringing signal is transmitted to the primary auxiliary winding Naux via magnetic core coupling, serving as an activation signal to request loop takeover from the primary winding.

[0155] Primary-side detection and response (T2 phase): After a period of detection shielding, the primary-side controller opens the activation signal recognition window. Upon detecting a ringing signal within the window, it immediately exits the sleep state and emits waves at a preset operating frequency and duty cycle to quickly replenish energy to the secondary side.

[0156] The system resumed normal operation, and the output voltage Vo recovered to the normal operating range with rapid recharging from the primary side. The primary and secondary side control modules resumed full-function operation, and the system switched from sleep mode to normal loop control mode.

[0157] Based on the above description, under no-load / very light-load conditions, the control system can maintain stable output voltage without virtual load through primary and secondary sleep control and hysteresis energy compensation mechanism, and the system standby power consumption is controlled below 5mW. The primary and secondary communication methods are coupled by transformers. Through anti-interference design such as delay determination and shielding time setting, the switching between sleep and active states of the primary and secondary sides is realized. Through a collaborative control mechanism that actively detects load dynamics and provides rapid primary response by the secondary controller, the system's dynamic performance is significantly improved when switching from no-load to full-load conditions.

[0158] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a cycle, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such cycle, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the cycle, method, article, or apparatus that includes said element.

[0159] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A flyback converter control system, characterized in that, The control system includes: a primary side circuit, a primary side control module, a transformer, a secondary side circuit, and a secondary side control module. The primary side circuit and the primary side control module are both connected to the primary winding of the transformer, and the secondary side circuit and the secondary side control module are both connected to the secondary winding of the transformer. During the process of the control system switching from no-load or very light-load conditions to full-load conditions, the secondary-side control module is used to detect the output voltage. When the output voltage is less than a first preset threshold, the secondary-side control module is used to send an activation signal to the primary-side control module through the transformer. The primary-side control module is used to generate a corresponding conduction frequency and a corresponding conduction time based on the activation signal, and control the primary-side switching transistor in the primary-side circuit according to the conduction frequency and the conduction time, so that the output voltage is adapted to the rated output voltage corresponding to the full-load condition. The primary-side control module is used to sample the output voltage. When the system is determined to be in an unloaded or extremely light-load condition based on the output voltage, the module reduces the operating frequency of the primary-side switch to the lowest frequency and maintains it for a first preset delay. After the first preset delay, the module controls the primary-side switch to turn off, so that the primary-side control module and the primary-side circuit enter an extremely low-power mode. The primary-side control module is also used to generate a sleep signal after the primary-side switch is turned off, and send the sleep signal to the secondary-side control module through the transformer so that the control system enters an ultra-low power mode.

2. The control system according to claim 1, characterized in that, The primary-side circuit includes a primary-side switching transistor, an auxiliary winding, a power supply diode, and a first filter capacitor. The auxiliary winding and the primary winding of the transformer are wound together on the core of the transformer. One end of the auxiliary winding is grounded and the other end of the auxiliary winding is connected to the anode of the power supply diode. The cathode of the power supply diode is connected to the first plate of the first filter capacitor, and the second plate of the first filter capacitor is grounded. Both the primary-side control module and the auxiliary winding are connected to the connection node of the power supply diode. The primary-side control module is used to sample the output voltage through the auxiliary winding. The drain of the primary-side switching transistor is connected to the primary winding of the transformer, the source is grounded, and the control terminal is connected to the primary-side control module. The primary-side control module is used to generate a primary drive signal based on the sampled output voltage; the primary drive signal is used to control the on and off of the primary-side switching transistor.

3. The control system according to claim 2, characterized in that, The secondary-side control circuit includes a second filter capacitor and a secondary-side switching transistor; One end of the secondary winding of the transformer is connected to the drain of the secondary-side switching transistor, and the other end is connected to the first plate of the second filter capacitor; the source of the secondary-side switching transistor and the second plate of the second filter capacitor are connected and then grounded. The control terminal of the secondary-side switch is connected to the drive output terminal of the secondary-side control module; The secondary-side control module is connected to the secondary winding of the transformer and is used to detect the output voltage and the sleep signal.

4. The control system according to claim 3, characterized in that, During the process of the control system switching from the no-load condition or the very light load condition to the full-load condition, the secondary-side control module is used to detect the output voltage. When the output voltage is less than the first preset threshold, the secondary-side control module outputs a high-level signal to control the secondary-side switch to be pre-turned on, so as to generate a first alternating current in the secondary winding of the transformer. The transformer is used to generate a first alternating magnetic flux in the magnetic core based on the first alternating current; The auxiliary winding of the transformer is used to induce a first characteristic ringing signal corresponding to the first alternating magnetic flux through magnetic core coupling, and transmits the first characteristic ringing signal as the activation signal to the primary side control module.

5. The control system according to claim 3, characterized in that, The secondary-side control module is also used to determine whether the control system switches to the no-load condition or the extremely light-load condition based on the sleep signal, and after a second preset delay, the secondary-side control module and the secondary-side circuit enter the extremely low-power mode. At this time, the system enters the extremely low-power mode.

6. The control system according to claim 3, characterized in that, The secondary-side control module includes a secondary-side controller and a secondary-side voltage holding unit; the secondary-side controller is connected to the secondary-side voltage holding unit. The secondary-side controller is used to send an enable signal to the secondary-side voltage holding unit when the control system enters the ultra-low power mode, so as to start the secondary-side voltage holding unit. The secondary-side voltage holding unit is used to detect the output voltage. When the output voltage is less than the second preset threshold, it sends a power replenishment and conduction command to the primary-side control module through the transformer. After receiving the power replenishment command, the primary-side control module controls the primary-side switch to turn on once, so that the output voltage rises back to the preset voltage range corresponding to the ultra-low power mode.

7. The control system according to claim 6, characterized in that, The secondary-side control module also includes a discharge unit; the secondary-side controller is also connected to the discharge unit. The voltage holding unit is also used to send a discharge command to the secondary controller when the output voltage is greater than a third preset threshold. The secondary-side controller is used to control the operation of the discharge module according to the discharge command, so that the output voltage drops to a preset voltage range corresponding to the ultra-low power mode.

8. The control system according to claim 6, characterized in that, The primary-side control module includes a signal detection module and a primary-side controller, and the primary-side controller is connected to the signal detection module and the control terminal of the primary-side switching transistor. The primary-side controller is used to control the primary-side switch to turn on at the lowest operating frequency when the control system switches to the no-load condition or the extremely light-load condition, and to turn off the primary-side switch after maintaining the lowest operating frequency for a first preset delay, and to transmit the generated sleep signal to the secondary-side controller through the transformer. The secondary-side controller is used to send an enable signal to the secondary-side voltage holding unit when the sleep signal is detected, so as to start the secondary-side voltage holding unit and make the fluctuation of the output voltage less than a preset fluctuation range when the system enters the ultra-low power mode. When the control system is in the ultra-low power mode and the system is connected to a load, the secondary-side controller is used to control the secondary-side switch to pre-turn on to generate a first characteristic ringing signal in the transformer when the drop value of the output voltage is greater than a preset detection threshold. This signal is then transmitted to the signal detection module of the primary-side control module as an activation signal. The primary-side controller is used to control the primary-side switch to turn on at a preset operating frequency after the signal detection module receives the activation signal, so that the system exits the ultra-low power mode.

9. The system according to claim 8, characterized in that, When the system transitions from a full-load condition to an unloaded or extremely light-load condition, the primary-side controller is used to gradually reduce the current operating frequency of the primary-side switching transistor to a preset switching frequency threshold. The primary-side controller is also used to control the primary-side circuit and the primary-side control module to enter an ultra-low power mode after the switching frequency of the primary-side switch is lower than a preset switching frequency threshold and continues for a first preset duration. After the primary-side circuit and the primary-side control module enter the ultra-low power mode, the secondary-side controller is used to control the secondary-side circuit and the secondary-side control module to enter the ultra-low power mode if the switching frequency of the primary-side switch is continuously detected to be lower than the preset switching frequency threshold within a second preset time period. At this time, the system enters the ultra-low power mode.

10. The system according to claim 9, characterized in that, The primary-side control module further includes a primary-side power supply voltage holding unit and a primary-side voltage detection unit; and the primary-side controller is connected to both the primary-side power supply voltage holding unit and the primary-side voltage detection unit. When the system is in an ultra-low power mode, the primary-side controller is used to turn off the primary-side switching transistor and turn on the primary-side power supply voltage holding unit. The primary-side power supply voltage holding unit is used to provide the primary-side controller with a minimum operating voltage when the system is in an ultra-low power mode and the primary-side switch is in a non-loop control state. When the primary side voltage detection unit detects that the supply voltage of the primary side controller drops to a preset minimum sustaining threshold, the primary side controller is used to control the primary side switch to turn on with the minimum sustaining power so as to supply power to the primary side controller through the auxiliary winding of the transformer. When the voltage detection unit detects that the supply voltage of the primary-side controller rises back to the preset maximum maintenance threshold, the primary-side controller controls the primary-side switch to turn off.

11. The system according to claim 10, characterized in that, The secondary-side control module further includes a secondary-side voltage detection unit, which is connected to the secondary-side controller; the secondary-side voltage detection unit is also connected to the output port of the system for detecting the output voltage. When the secondary-side control module enters an ultra-low power mode, the secondary-side controller enables the secondary-side voltage holding unit and the secondary-side voltage detection unit. The secondary-side controller is used to send a power replenishment signal to the primary-side controller through the transformer when the output voltage is detected by the secondary-side voltage detection unit to drop to a preset voltage threshold. After receiving the power replenishment signal, the primary-side controller turns on the primary-side switch until the output voltage rises back to the preset voltage threshold, at which point it turns off the primary-side switch.

12. The system according to claim 11, characterized in that, When the system is in an ultra-low power mode and the secondary side voltage detection unit detects that the output voltage has dropped to the secondary activation threshold voltage, the secondary side controller controls the secondary side circuit and the secondary side control module to exit the ultra-low power mode, and generates a first characteristic ringing signal in the transformer as an activation signal by controlling the secondary side switch to pre-turn on, and transmits it to the primary side controller. The primary-side controller is used to control the primary-side circuit and the primary-side control module to exit the ultra-low power mode after receiving the activation signal, waiting for a preset primary detection shielding time, and identifying the ringing signal within a preset activation signal identification window. It then controls the primary-side switch to turn on with a preset operating frequency and duty cycle so that the output voltage returns to the normal operating range.

Images