A multi-output flyback converter and control method

Abstract

The application discloses a multi-output flyback converter and a control method. The converter comprises a switching tube, a transformer and an energy transfer circuit. The transformer comprises a primary winding and at least two secondary windings. The switching tube is connected to the primary winding. The at least two secondary windings comprise a first secondary winding and a second secondary winding. The first secondary winding is connected to a non-feedback port, and the second secondary winding is connected to a feedback port. The energy transfer circuit comprises at least a DCDC circuit. An input end of the energy transfer circuit is connected to the non-feedback port, and an output end of the energy transfer circuit is connected to the feedback port. When the voltage at the non-feedback port is greater than a first preset voltage, the energy transfer circuit transfers the energy at the non-feedback port to the feedback port by using the DCDC circuit. The excess energy at the non-feedback port is transferred to the feedback port by using the DCDC circuit, so that the energy is effectively utilized, the energy is prevented from being consumed in the form of heat energy, and the power conversion efficiency of the multi-output flyback converter is improved.

Description

Technical Field

[0001] This application relates to the field of power electronics technology, specifically to a multi-output flyback converter and its control method. Background Technology

[0002] In an electrical appliance, different loads require different voltage levels. For example, a fan typically requires 24V, a microcontroller (MCU) typically requires 5V, and the driver of a MOSFET or IGBT requires 15V. Therefore, the power supply in an electrical appliance needs to output different voltage levels.

[0003] Currently, electrical appliances use flyback converters in switching power supplies. Flyback converters have multiple outputs, each with a different voltage and a different secondary winding. Generally, the different turns ratios of the primary winding and the various secondary windings of the transformer are used to output different voltages.

[0004] In closed-loop control of a flyback converter, only one output voltage is typically selected as the closed-loop feedback voltage; this output is called the feedback port, and the others are called non-feedback ports. When the feedback port is heavily loaded and the non-feedback ports are lightly loaded, the energy stored in the primary winding of the transformer increases to maintain voltage stability at the feedback port. Simultaneously, the energy stored in the primary winding is transferred to the secondary winding according to the turns ratio. Since the non-feedback ports are lightly loaded, they consume less energy, and the energy transferred from the primary winding to the non-feedback ports cannot be consumed in time, causing the voltage at the non-feedback ports to rise. Similarly, when the feedback port is lightly loaded and the non-feedback ports are heavily loaded, the energy transferred from the primary winding to the non-feedback ports is rapidly consumed, causing the voltage at the non-feedback ports to drop. These fluctuating voltages at the non-feedback ports can affect the normal operation of downstream loads. To prevent excessively high output voltages from damaging downstream loads, resistors can be added to the non-feedback ports to dissipate energy; however, this method reduces the converter's conversion efficiency. Summary of the Invention

[0005] In view of this, this application provides a multi-output flyback converter and a control method, which can improve the power conversion efficiency of the flyback converter.

[0006] This application provides a multi-output flyback converter, including: a switching transistor, a transformer, and an energy transport circuit;

[0007] A transformer includes a primary winding and at least two secondary windings;

[0008] The switching transistor is connected to the primary winding;

[0009] At least two secondary windings include a first secondary winding and a second secondary winding; the first secondary winding is connected to the non-feedback port, and the second secondary winding is connected to the feedback port.

[0010] The energy transport circuit includes at least a DC-DC circuit, with the input terminal of the energy transport circuit connected to a non-feedback port and the output terminal of the energy transport circuit connected to a feedback port.

[0011] An energy transfer circuit is used to transfer energy from the non-feedback port to the feedback port using a DC-DC circuit when the voltage at the non-feedback port is greater than a first preset voltage.

[0012] Preferably, the energy transfer circuit is further used to transfer energy from the feedback port to the non-feedback port using a DC-DC circuit when the voltage at the non-feedback port is less than the second preset voltage; the first preset voltage is greater than the second preset voltage.

[0013] Preferably, it further includes: a controller;

[0014] The controller is used to control the DC-DC circuit to operate in the forward direction when the voltage at the non-feedback port is greater than a first preset voltage; it is also used to control the DC-DC circuit to operate in the reverse direction when the voltage at the non-feedback port is less than a second preset voltage.

[0015] Preferably, the energy transport circuit further includes: a first hysteresis comparator;

[0016] The positive input terminal of the first hysteresis comparator is connected to the non-feedback port, and the negative input terminal of the first hysteresis comparator is connected to the first preset voltage.

[0017] The output signal of the first hysteresis comparator is connected to the first enable terminal of the DC-DC circuit to enable the DC-DC circuit to operate in the forward direction.

[0018] Preferably, the energy transport circuit further includes: a second hysteresis comparator;

[0019] The positive input of the second hysteresis comparator is connected to the second preset voltage, and the negative input of the second hysteresis comparator is connected to the non-feedback port; the output of the second hysteresis comparator is connected to the second enable terminal of the DC-DC circuit to enable the DC-DC circuit to work in reverse.

[0020] Preferably, there are N non-feedback ports, where N is an integer greater than or equal to 2, and N energy transport circuits, with each non-feedback port corresponding to one of the energy transport circuits.

[0021] Each non-feedback port is connected to the input of the corresponding energy transport circuit; the outputs of all energy transport circuits are connected to the feedback port.

[0022] Preferably, it further includes: a controller; the controller includes a voltage sampling circuit;

[0023] The input terminal of the voltage sampling circuit is connected to a non-feedback port;

[0024] The controller is used to control the DC-DC circuit to work in the forward direction when the sampled voltage value is greater than a first preset voltage, and to control the DC-DC circuit to work in the reverse direction when the sampled voltage value is less than a second preset voltage value.

[0025] Preferably, the DC-DC circuit is a buck chopper circuit, a boost chopper circuit, a buck-boost chopper circuit, a forward converter circuit, a flyback circuit, a half-bridge circuit, a full-bridge circuit, or a push-pull circuit.

[0026] This application also provides a control method for a multi-output flyback converter. The multi-output flyback converter includes: a switching transistor, a transformer, and an energy transport circuit; the transformer includes a primary winding and at least two secondary windings; the switching transistor is connected to the primary winding; the at least two secondary windings include a first secondary winding and a second secondary winding; the first secondary winding is connected to a non-feedback port, and the second secondary winding is connected to a feedback port; the energy transport circuit includes at least a DC-DC converter; the input terminal of the energy transport circuit is connected to the non-feedback port, and the output terminal of the energy transport circuit is connected to the feedback port.

[0027] The methods include:

[0028] Detect the voltage at the non-feedback port;

[0029] When the voltage at the non-feedback port is greater than the first preset voltage, the energy at the non-feedback port is transferred to the feedback port using a DC-DC circuit.

[0030] Preferably, it further includes:

[0031] When the voltage at the non-feedback port is less than the second preset voltage, the energy at the feedback port is transferred to the non-feedback port using a DC-DC circuit; the first preset voltage is greater than the second preset voltage.

[0032] Therefore, this application has the following beneficial effects:

[0033] The multi-output flyback converter improved in this application embodiment can detect the voltage of the non-feedback port in real time and control the operation of the DC-DC circuit according to the voltage of the non-feedback port. When the voltage of the non-feedback port is greater than a first preset voltage, the DC-DC circuit can transfer the excess energy of the non-feedback port to the feedback port, thereby effectively utilizing energy and avoiding energy consumption in the form of heat, thus improving the power conversion efficiency of the multi-output flyback converter. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of a multi-output flyback converter;

[0035] Figure 2 A schematic diagram of a multi-output flyback converter provided in an embodiment of this application;

[0036] Figure 3 A schematic diagram of another multi-output flyback converter provided in the embodiments of this application;

[0037] Figure 4 A schematic diagram of yet another multi-output flyback converter provided in the embodiments of this application;

[0038] Figure 5 A schematic diagram of yet another multi-output flyback converter provided in an embodiment of this application;

[0039] Figure 6 A schematic diagram of another multi-output flyback converter provided in the embodiments of this application;

[0040] Figure 7 A schematic diagram of yet another multi-output flyback converter provided in an embodiment of this application;

[0041] Figure 8 for Figure 7 Corresponding simulation result diagram;

[0042] Figure 9 A schematic diagram of yet another multi-output flyback converter provided in the embodiments of this application;

[0043] Figure 10 for Figure 9 Corresponding simulation result diagram;

[0044] Figure 11 A flowchart illustrating a control method for a multi-output flyback converter provided in this application embodiment. Detailed Implementation

[0045] To help those skilled in the art better understand flyback converters, the working principle of flyback converters will be introduced below with reference to the accompanying drawings.

[0046] See Figure 1 The figure shows a schematic diagram of a multi-output flyback converter.

[0047] The multi-output flyback converter provided in this application includes a controller U1, an oscillation circuit, a feedback circuit, a drive circuit, a buffer circuit, a startup circuit, and a current sampling circuit. It also includes a transformer T1 and multiple secondary output circuits.

[0048] This application does not specifically limit the number of paths in the secondary output. Figure 1The transformer T1 includes three secondary windings. Taking the three secondary outputs as an example, secondary output 1 is a non-feedback port, secondary output 2 is an auxiliary power supply, and secondary output 3 is a feedback port.

[0049] It should be understood that a multi-output flyback converter is a DC-to-DC converter, meaning that with an input voltage of V1, it can output multiple DC voltages.

[0050] The startup circuit and buffer circuit are for starting up and buffering the converter. The oscillation circuit provides the operating frequency for the controller. The drive circuit is controlled by the controller U1 and drives the switching state of the switching transistor Q1.

[0051] The current sampling circuit is used to sample the current of the switching transistor Q1 and feed it back to the controller U1.

[0052] The feedback circuit is used to sample the voltage at the feedback port and feed it back to the controller U1.

[0053] Because the non-feedback port is lightly loaded, it consumes less energy, and the energy transferred from the primary winding to the non-feedback port cannot be consumed in time, which causes the voltage of the non-feedback port to rise. Similarly, when the feedback port is lightly loaded and the non-feedback port is heavily loaded, the energy transferred from the transformer primary winding to the non-feedback port is consumed quickly, which causes the voltage of the non-feedback port to drop.

[0054] For example, when the load on secondary output 3 is heavy and the load on secondary output 1 is light, the voltage of secondary output 1 will increase. As another example, when secondary output 3 is unloaded (no load) and secondary output 1 is heavily loaded, since secondary output 3 acts as a feedback port, the controller U1 will collect the voltage of secondary output 3 and perform closed-loop control. Therefore, the voltage of secondary output 3 will stabilize, causing the voltage of secondary output 1 to drop. The output voltage of the non-feedback ports varies with the load on the feedback ports, causing instability in the output voltage of the non-feedback ports. This phenomenon can be characterized by the cross-regulation rate. The cross-regulation rate refers to the impact of a load on the voltage of one output port of the flyback converter on the voltage of another output port; it is the percentage of the maximum voltage change of that output port to its corresponding rated voltage.

[0055] Typically, a DC-DC converter is added to the subsequent circuitry of a non-feedback port to stabilize the supply voltage. To prevent the DC-DC converter's output voltage from being too low to adequately power the circuit, the output voltage of the non-feedback port is usually much higher than the operating voltage of the final circuit. In this case, when the feedback port is under heavy load, the output voltage of the non-feedback port will become even higher, exceeding the device's allowable operating voltage and causing overvoltage damage to the relevant components.

[0056] To solve the above problems, a common approach is to add a resistor to consume the energy that is not consumed at the output port. However, this will result in energy waste and reduce the efficiency of the converter's power conversion.

[0057] Therefore, this application provides a multi-output flyback converter, including an energy transfer circuit, which can transfer energy from the non-feedback port to the feedback port when needed. Since the feedback port can be closed-loop controlled, this scheme utilizes the excess energy in the non-feedback port without consuming it as heat. This improves the converter's cross-regulation rate and also enhances the converter's power conversion efficiency.

[0058] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, the embodiments of this application will be further described in detail below with reference to the accompanying drawings and specific implementation methods.

[0059] See Figure 2 The figure is a schematic diagram of a multi-output flyback converter provided in an embodiment of this application.

[0060] The multi-output flyback converter provided in this application includes: a switching transistor Q1, a transformer T1, and an energy transport circuit 100;

[0061] Transformer T1 includes a primary winding and at least two secondary windings; Figure 2 The following section will continue to use three secondary windings as an example.

[0062] Switch Q1 is connected to the primary winding; the primary winding is connected to power supply BT1. This application does not specifically limit the source of power supply BT1; it can be a DC power supply or the output of the previous stage conversion circuit.

[0063] At least two secondary windings include a first secondary winding and a second secondary winding; the first secondary winding is connected to the non-feedback port, and the second secondary winding is connected to the feedback port.

[0064] The energy transport circuit 100 includes at least a DC-DC circuit 10. The input terminal of the energy transport circuit 100 is connected to a non-feedback port, and the output terminal of the energy transport circuit 100 is connected to a feedback port.

[0065] This application does not specifically limit the specific implementation of the DC-DC circuit. For example, the DC-DC circuit can be a unidirectional conversion circuit or a bidirectional conversion circuit; furthermore, the DC-DC circuit can be an isolated conversion circuit (including an internal transformer) or a non-isolated conversion circuit. Additionally, the DC-DC circuit can be a boost conversion circuit or a buck conversion circuit. The DC-DC circuit can employ open-loop control, closed-loop control, or any other circuit topology that enables energy flow.

[0066] The energy transfer circuit 100 is used to transfer energy from the non-feedback port to the feedback port using the DC-DC circuit 10 when the voltage at the non-feedback port is greater than a first preset voltage.

[0067] When the non-feedback port is lightly loaded and the feedback port is heavily loaded, the voltage of the non-feedback port will rise. When the voltage of the non-feedback port is greater than the first preset voltage, the DC-DC circuit is activated. The DC-DC circuit 10 is used to flow the energy from the non-feedback port to the feedback port, so that the voltage of the non-feedback port drops to the normal voltage.

[0068] The multi-output flyback converter improved in this application embodiment can detect the voltage of the non-feedback port in real time and control the operation of the DC-DC circuit according to the voltage of the non-feedback port. When the voltage of the non-feedback port is greater than a first preset voltage, the DC-DC circuit can transfer the excess energy of the non-feedback port to the feedback port, thereby effectively utilizing energy and avoiding energy consumption in the form of heat, thus improving the power conversion efficiency of the multi-output flyback converter.

[0069] In addition, the controller U1 can control the switching state of the switching transistor Q1 based on the feedback voltage of the feedback port.

[0070] The multi-output flyback converter provided in this application embodiment can not only transfer energy from the non-feedback port to the feedback port, but also transfer energy from the feedback port to the non-feedback port. That is, the DC-DC circuit is a bidirectional conversion circuit. For details, please refer to [link to documentation]. Figure 2 The energy transfer circuit 100 is also used to transfer the energy from the feedback port to the non-feedback port using the DC-DC circuit 10 when the voltage at the non-feedback port is less than the second preset voltage; the first preset voltage is greater than the second preset voltage.

[0071] The embodiments of this application do not specifically limit the way the DC-DC circuit is triggered. For example, it can be triggered by a controller or by an analog circuit. Two different implementation forms are described below with reference to the accompanying drawings.

[0072] See Figure 3 This figure is a schematic diagram of another multi-output flyback converter provided in an embodiment of this application.

[0073] The multi-output flyback converter provided in this application embodiment further includes a controller U1. The controller U1 can be the controller of the multi-output flyback converter or an external controller. This embodiment uses the controller built into the multi-output flyback converter as an example. The controller can have a built-in voltage sampling circuit, such as a built-in analog-to-digital converter, which can acquire analog voltage and convert it into digital voltage.

[0074] Controller U1 is used to control the DC-DC circuit 10 to operate in the forward direction when the sampled voltage value of the voltage sampling circuit is greater than a first preset voltage, that is, to transfer the energy from the non-feedback port to the feedback port; it is also used to control the DC-DC circuit 10 to operate in the reverse direction when the sampled voltage value is less than a second preset voltage value, that is, to transfer the energy from the feedback port to the non-feedback port. The DC-DC circuit 10 is a bidirectional conversion circuit.

[0075] The multi-output flyback converter provided in this application embodiment can achieve energy transfer without adding any other hardware circuits, except for adding a DC-DC circuit. This avoids the situation where energy is consumed by resistors to reduce voltage when the voltage of some ports is too high, thus avoiding energy loss.

[0076] The following describes how to use analog circuits to trigger the DC-DC converter to start working.

[0077] See Figure 4 This figure is a schematic diagram of another multi-output flyback converter provided in the embodiments of this application.

[0078] In the multi-output flyback converter provided in this application embodiment, the energy transport circuit further includes: a first hysteresis comparator U4;

[0079] The positive input terminal of the first hysteresis comparator U4 is connected to the non-feedback port, and the negative input terminal of the first hysteresis comparator U4 is connected to the first preset voltage VTH1.

[0080] The output signal of the first hysteresis comparator U4 is used to enable the DC-DC circuit 10 to operate in the forward direction. That is, the working principle of the first hysteresis comparator U4 is that when the voltage at the positive input terminal is greater than the voltage at the negative input terminal, the first hysteresis comparator U4 outputs a high level, so the enable signal of the DC-DC circuit 10 is active at a high level. Therefore, when the voltage at the non-feedback port is greater than VTH1, the first hysteresis comparator U4 outputs a high level, the first enable terminal EN1 of the DC-DC circuit 10 is active, and the DC-DC circuit 10 starts to operate in the forward direction, transferring the energy from the non-feedback port to the feedback port. As the transfer progresses, the voltage at the non-feedback port will decrease, and the voltage at the feedback port will increase. However, the voltage at the feedback port is controlled by the controller. The controller adjusts the voltage at the feedback port by controlling the duty cycle or frequency of the switching transistor Q1. Therefore, the entire converter can achieve a new stable output.

[0081] The above describes only how a DC-DC circuit transfers energy from a non-feedback port to a feedback port. Alternatively, a DC-DC circuit can also transfer energy from a feedback port to a non-feedback port. A detailed explanation follows with accompanying diagrams.

[0082] See Figure 5 This figure is a schematic diagram of another multi-output flyback converter provided in an embodiment of this application.

[0083] The multi-output flyback converter provided in this application embodiment further includes a second hysteresis comparator U5 in its energy transport circuit.

[0084] The positive input terminal of the second hysteresis comparator U5 is connected to the second preset voltage VTH2, and the negative input terminal of the second hysteresis comparator U5 is connected to the non-feedback port; the output terminals of the first hysteresis comparator U4 and the second hysteresis comparator U5 are respectively connected to the first enable terminal EN1 and the second enable terminal EN2 of the DC-DC circuit 10.

[0085] It should be understood that only one of the output terminals of the first hysteresis comparator U4 and the second hysteresis comparator U5 can output a high level, thereby triggering the DC-DC converter 10 to start forward or reverse operation. In the multi-output flyback converter provided in this application embodiment, when the voltage of the non-feedback port is greater than VTH1, the first hysteresis comparator U4 triggers the DC-DC converter 10 to operate in the forward direction, and the DC-DC converter 10 transfers energy from the non-feedback port to the feedback port. When the voltage of the non-feedback port is less than VTH2, the second hysteresis comparator U5 triggers the DC-DC converter 10 to operate in the reverse direction, and the DC-DC converter 10 transfers energy from the feedback port to the non-feedback port.

[0086] The following explanation Figure 5 The operating modes of the provided converter.

[0087] (1) When both the non-feedback port and the feedback port are under normal load, the DC-DC circuit 10 is not enabled.

[0088] (2) When the non-feedback port is lightly loaded and the feedback port is heavily loaded, the voltage of the non-feedback port rises. When the voltage is higher than VTH1, the first hysteresis comparator U4 outputs a high level, which causes the DCDC circuit 10 to start working in the forward direction. The energy flows from the non-feedback port to the feedback port, causing the voltage of the non-feedback port to drop to the normal voltage.

[0089] (3) When the non-feedback port is under heavy load and the feedback port is under light load, the voltage of the non-feedback port drops. When the voltage is lower than VTH2, the second hysteresis comparator U5 outputs a high level, which causes the DCDC circuit 10 to start working in reverse. The energy flows from the feedback port to the non-feedback port, causing the voltage of the non-feedback port to rise back to the normal voltage.

[0090] The multi-output flyback converter provided in this application embodiment can realize bidirectional energy flow between the non-feedback port and the feedback port, and can automatically achieve voltage balance when the port load is light. This multi-output flyback converter can improve the situation of excessively high voltage at the non-feedback port, and at the same time improve the situation of excessively low voltage at the non-feedback port, thereby improving its cross-regulation rate.

[0091] The above description only illustrates a single non-feedback port with an energy transport circuit. It should be understood that when a multi-output flyback converter includes multiple non-feedback ports, each non-feedback port can be connected to an energy transport circuit. For example, there can be N non-feedback ports (N being an integer greater than or equal to 2), and N energy transport circuits, with a one-to-one correspondence between each non-feedback port and energy transport circuit. Each non-feedback port is connected to the input terminal of its corresponding energy transport circuit; the output terminals of all energy transport circuits are connected to the feedback port.

[0092] See Figure 6 This figure is a schematic diagram of another multi-output flyback converter provided in an embodiment of this application.

[0093] For ease of understanding and explanation, we will take a multi-output flyback converter with two non-feedback ports as an example. Of course, it can include more non-feedback ports.

[0094] Secondary output 1 and secondary output 4 are both non-feedback ports. These two non-feedback ports are connected to their respective energy transport circuits. The two energy transport circuits have identical structures, which will not be described further here; please refer to [link to relevant documentation]. Figure 5 Introduction.

[0095] See also the secondary side output 1. Figure 5 The details of the secondary output circuit will not be repeated here. Only the operating principle of secondary output 4 will be described. Since the output voltages of secondary output 1 and secondary output 4 may differ—for example, the load corresponding to secondary output 1 may require 12V, while the load corresponding to secondary output 4 may require 5V—the negative input of the first hysteresis comparator U4 corresponding to secondary output 4 is connected to the third preset voltage VTH3, and the negative input of the second hysteresis comparator U5 corresponding to secondary output 4 is connected to the third preset voltage VTH4. VTH3 is greater than VTH4. The remaining operating principles are the same as the energy transport circuit corresponding to secondary output 1, and will not be repeated here.

[0096] It should be noted that energy can be transferred from two non-feedback ports to the feedback port simultaneously. Conversely, energy can be transferred from the feedback port to two non-feedback ports.

[0097] The following section, with reference to the accompanying diagrams, introduces two implementation methods for DC-DC circuits.

[0098] See Figure 7 This figure is a schematic diagram of another multi-output flyback converter provided in an embodiment of this application.

[0099] The DC-DC circuit 10 in the multi-output flyback converter provided in this application embodiment is a flyback circuit.

[0100] Specifically, the DC-DC circuit 10 can be a unidirectional isolated flyback circuit.

[0101] The PWM control chip used in this unidirectional isolated flyback circuit has a built-in hysteresis comparator, which can control the enable operation and thus control the operation of the unidirectional isolated flyback circuit. It belongs to a DC-DC circuit with an EN port.

[0102] The input of this unidirectional isolated flyback circuit is connected to the non-feedback port of the multi-output flyback converter, while the output of the unidirectional isolated flyback circuit is connected to the feedback port. When the unidirectional isolated flyback circuit only transfers energy from the non-feedback port to the feedback port, a diode can be connected between the output of the DC-DC converter and the feedback port to prevent energy from the feedback port from flowing back into the DC-DC converter.

[0103] Figure 8 It shows Figure 7 The corresponding simulation results.

[0104] The DC-DC circuit does not operate when the voltage at the non-feedback port is less than 18V; it starts operating when the voltage at the non-feedback port is greater than 18V, and its output voltage begins to build up, which is called the feedback voltage. The output voltage of this DC-DC circuit is approximately 25V, slightly higher than the voltage at the feedback port, so that energy can flow from the DC-DC circuit into the feedback port.

[0105] When the feedback voltage is higher than the feedback port voltage, a feedback current begins to appear, flowing into the feedback port from the DC-DC circuit. Since excess energy at the non-feedback port is transferred, the voltage at the non-feedback port begins to drop to around 16V and stabilizes, thus improving the situation where the non-feedback port voltage is too high.

[0106] See Figure 9 This figure is a schematic diagram of another multi-output flyback converter provided in the embodiments of this application.

[0107] The DC-DC circuit 10 in the multi-output flyback converter provided in this application embodiment is a push-pull DC-DC circuit.

[0108] The push-pull circuit can be implemented using a unidirectional isolated half-bridge circuit, which is a common DC-DC circuit topology.

[0109] A unidirectional isolated half-bridge circuit consists of an oscillation circuit, a startup circuit, a drive circuit, and a secondary output circuit, with the output voltage controlled in an open-loop manner.

[0110] The PWM control chip used in this unidirectional isolated half-bridge circuit has a built-in hysteresis comparator, which can be controlled to enable the unidirectional isolated half-bridge circuit and thus control the operation of the circuit. It is a DC-DC circuit with an EN port.

[0111] The input of this unidirectional isolated half-bridge circuit is connected to the output of the non-feedback port. When the unidirectional isolated flyback circuit only transfers energy from the non-feedback port to the feedback port, a diode can be connected between the output of the DC-DC circuit and the feedback port to prevent energy from the feedback port from flowing back into the DC-DC circuit. This unidirectional isolated half-bridge circuit also maintains the electrical isolation between the non-feedback port and the feedback port.

[0112] When the voltage at the non-feedback port is higher than 18V, the hysteresis comparator outputs a high level, which enables the DC-DC circuit to work, transferring excess energy from the non-feedback port to the feedback port, thus achieving efficient energy utilization.

[0113] Figure 10 It shows Figure 9 The corresponding simulation results.

[0114] When the voltage at the non-feedback port is less than 18V, the unidirectional isolated half-bridge circuit does not operate. When the output voltage is greater than 18V, the unidirectional isolated half-bridge circuit starts operating, and its output voltage begins to build up; in this application, this output voltage is referred to as the feedback voltage. The output voltage of this unidirectional isolated half-bridge circuit is approximately 25V, slightly higher than the voltage at the feedback port, allowing energy to flow from the unidirectional isolated half-bridge circuit into the feedback port. When the feedback voltage is higher than the voltage at the feedback port, a feedback current begins to appear, flowing from the unidirectional isolated half-bridge circuit into the feedback port. Since excess energy at the non-feedback port is transferred, the voltage at the non-feedback port begins to drop to approximately 16V and stabilizes, thus improving the situation where the voltage at the non-feedback port is too high.

[0115] Based on the multi-output flyback converter provided in the above embodiments, this application also provides a control method for the multi-output flyback converter, which will be described in detail below with reference to the accompanying drawings.

[0116] See Figure 11 The figure is a flowchart of a control method for a multi-output flyback converter provided in an embodiment of this application.

[0117] The control method for a multi-output flyback converter provided in this application embodiment includes: a switching transistor, a transformer, and an energy transport circuit; the transformer includes a primary winding and at least two secondary windings; the switching transistor is connected to the primary winding; the at least two secondary windings include a first secondary winding and a second secondary winding; the first secondary winding is connected to a non-feedback port, and the second secondary winding is connected to a feedback port; the energy transport circuit includes at least a DC-DC converter; the input terminal of the energy transport circuit is connected to the non-feedback port, and the output terminal of the energy transport circuit is connected to the feedback port.

[0118] The methods include:

[0119] S1101: Detects the voltage at the non-feedback port;

[0120] S1102: When the voltage at the non-feedback port exceeds the first preset voltage, the energy at the non-feedback port is transferred to the feedback port using a DC-DC converter. When the voltage at the non-feedback port exceeds the first preset voltage, it indicates that the non-feedback port is under light load while the feedback port is under heavy load. The voltage at the non-feedback port rises until it reaches the first preset voltage, indicating an overvoltage situation, requiring energy transfer. The energy then flows from the non-feedback port to the feedback port, causing the voltage at the non-feedback port to drop back to normal.

[0121] The multi-output flyback converter provided in this application embodiment can realize bidirectional energy flow between the non-feedback port and the feedback port, and can automatically achieve voltage balance when the port load is light. This multi-output flyback converter can improve the situation of excessively high voltage at the non-feedback port, and at the same time improve the situation of excessively low voltage at the non-feedback port, thereby improving its cross-regulation rate.

[0122] Furthermore, the control method provided in this application embodiment can transfer energy from the feedback port to the non-feedback port. Energy transfer is only triggered when the voltage at the non-feedback port falls below a certain value. Therefore, the control method provided in this application embodiment further includes:

[0123] When the voltage at the non-feedback port is less than the second preset voltage, the energy at the feedback port is transferred to the non-feedback port using a DC-DC circuit; the first preset voltage is greater than the second preset voltage.

[0124] When the non-feedback port is under heavy load and the feedback port is under light load, the voltage of the non-feedback port will drop. When the voltage drops to a certain value and undervoltage occurs, the trigger energy flows from the feedback port to the non-feedback port, causing the voltage of the non-feedback port to rise back to the normal voltage.

[0125] The control method provided in this application realizes the transfer of energy between the non-feedback port and the feedback port by detecting the voltage of the non-feedback port. When the voltage of the non-feedback port is too high, the excess energy in the port is transferred to the feedback port for full utilization, instead of being consumed by the resistor. This improves the cross-regulation rate of the multi-output flyback converter and improves the efficiency of the power supply.

[0126] It should be noted that the various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the systems or apparatus disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the descriptions are relatively simple, and relevant parts can be referred to the method section.

[0127] The above description of the disclosed embodiments enables those skilled in the art to make or use this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A multi-output flyback converter, characterized in that, include: Switching transistors, transformers, and energy transport circuits; The transformer includes a primary winding and at least two secondary windings; The switching transistor is connected to the primary winding; The at least two secondary windings include a first secondary winding and a second secondary winding; the first secondary winding is connected to a non-feedback port, and the second secondary winding is connected to a feedback port. The energy transport circuit includes at least a DC-DC circuit, the input terminal of the energy transport circuit is connected to the non-feedback port, and the output terminal of the energy transport circuit is connected to the feedback port; The energy transfer circuit is used to transfer the energy from the non-feedback port to the feedback port using the DC-DC circuit when the voltage at the non-feedback port is greater than a first preset voltage.

2. The converter according to claim 1, characterized in that, The energy transfer circuit is further configured to transfer energy from the feedback port to the non-feedback port using the DC-DC circuit when the voltage at the non-feedback port is less than the second preset voltage; the first preset voltage is greater than the second preset voltage.

3. The converter according to claim 2, characterized in that, Also includes: Controller; The controller is used to control the DC-DC circuit to operate in the forward direction when the voltage at the non-feedback port is greater than a first preset voltage. It is also used to control the DC-DC circuit to operate in reverse when the voltage at the non-feedback port is less than the second preset voltage.

4. The converter according to claim 2, characterized in that, The energy transport circuit further includes: a first hysteresis comparator; The positive input terminal of the first hysteresis comparator is connected to the non-feedback port, and the negative input terminal of the first hysteresis comparator is connected to the first preset voltage. The output signal of the first hysteresis comparator is connected to the first enable terminal of the DC-DC circuit to enable the DC-DC circuit to operate in the forward direction.

5. The converter according to claim 4, characterized in that, The energy transport circuit further includes: a second hysteresis comparator; The positive input terminal of the second hysteresis comparator is connected to the second preset voltage, and the negative input terminal of the second hysteresis comparator is connected to the non-feedback port; the output terminal of the second hysteresis comparator is connected to the second enable terminal of the DC-DC circuit to enable the DC-DC circuit to operate in reverse.

6. The converter according to any one of claims 1-4, characterized in that, There are N non-feedback ports, where N is an integer greater than or equal to 2; there are N energy transport circuits, and each non-feedback port corresponds to one of the energy transport circuits. Each of the non-feedback ports is connected to the input terminal of the corresponding energy transport circuit; the output terminals of all the energy transport circuits are connected to the feedback ports.

7. The converter according to any one of claims 1-3, characterized in that, Also includes: Controller; The controller includes a voltage sampling circuit; The input terminal of the voltage sampling circuit is connected to the non-feedback port; The controller is configured to control the DC-DC circuit to operate in the forward direction when the sampled voltage value of the voltage sampling circuit is greater than a first preset voltage, and to control the DC-DC circuit to operate in the reverse direction when the sampled voltage value is less than a second preset voltage value.

8. The converter according to any one of claims 1-3, characterized in that, The DC-DC circuit can be a buck chopper circuit, a boost chopper circuit, a buck-boost chopper circuit, a forward converter circuit, a flyback circuit, a half-bridge circuit, a full-bridge circuit, or a push-pull circuit.

9. A control method for a multi-output flyback converter, characterized in that, The multi-output flyback converter includes: a switching transistor, a transformer, and an energy transport circuit; the transformer includes a primary winding and at least two secondary windings; the switching transistor is connected to the primary winding; the at least two secondary windings include a first secondary winding and a second secondary winding; the first secondary winding is connected to a non-feedback port, and the second secondary winding is connected to a feedback port; the energy transport circuit includes at least a DC-DC converter; the input terminal of the energy transport circuit is connected to the non-feedback port, and the output terminal of the energy transport circuit is connected to the feedback port; The method includes: Detect the voltage at the non-feedback port; When the voltage at the non-feedback port is greater than a first preset voltage, the energy of the non-feedback port is transferred to the feedback port using the DC-DC circuit.

10. The method according to claim 9, characterized in that, Also includes: When the voltage at the non-feedback port is less than the second preset voltage, the energy of the feedback port is transferred to the non-feedback port using the DC-DC circuit. The first preset voltage is greater than the second preset voltage.

Images