An isolated power supply

Abstract

This invention belongs to the field of power electronics and integrated circuits, specifically providing a novel isolated power supply to solve the problems of system complexity, high system cost, and difficulty in achieving high power density caused by signal isolation devices in traditional isolated power supplies. This invention creatively proposes a novel isolated power supply comprising: an isolation transformer, a power transmission circuit and a control circuit located on the primary side of the isolation transformer, and a rectifier circuit and a feedback circuit located on the secondary side of the isolation transformer. The isolated power supply includes a power transmission state and a feedback state. Through a creative design that alternates between the power transmission state and the feedback state, the power transmission from the primary circuit to the secondary circuit and the signal feedback from the secondary circuit to the primary circuit can both utilize the same isolation transformer. This achieves a stable output voltage without the need for additional signal isolation devices and maintains high conversion efficiency even under light load conditions.

Description

Technical Field

[0001] This invention belongs to the field of power electronics and integrated circuits, and specifically provides an isolated power supply. Technical Background

[0002] With the increasing number of working scenarios for modern electronic devices, isolated power supplies are often used in some applications to avoid the impact of external environmental interference on the safety and stability of electronic devices. Isolation devices can achieve electrical isolation between the main circuit and the secondary circuit, ensuring the safe operation of electronic devices.

[0003] Currently, traditional isolated power supplies such as Figure 1 As shown, a primary-side control scheme is adopted. In order to ensure that the power supply has a stable output voltage under different loads or unstable input voltages, the circuit usually requires feedback control based on the output voltage. The secondary side needs to use additional signal isolation devices (such as optocouplers) to transmit the feedback signal from the secondary circuit back to the primary circuit, thereby controlling the system's operating state. However, signal isolation devices increase system cost and complexity, which is not conducive to achieving high power density. Summary of the Invention

[0004] The purpose of this invention is to provide an isolated power supply that solves the problems of system complexity, high system cost, and difficulty in achieving high power density caused by signal isolation devices in traditional isolated power supplies. This invention creatively proposes an isolated power supply comprising: an isolation transformer, a power transmission circuit and a control circuit located on the primary side of the isolation transformer, and a rectifier circuit and a feedback circuit located on the secondary side of the isolation transformer. The isolated power supply includes a power transmission state and a feedback state. Through the creative design of alternating power transmission and feedback states, the power transmission from the primary circuit to the secondary circuit and the signal feedback from the secondary circuit to the primary circuit can both utilize the same isolation transformer. This achieves a stable output voltage without the need for additional signal isolation devices and maintains high conversion efficiency even under light load conditions.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] An isolated power supply includes: an isolation transformer, a power transmission circuit and a control circuit located on the primary side of the isolation transformer, and a rectifier circuit and a feedback circuit located on the secondary side of the isolation transformer; characterized in that:

[0007] The isolated power supply includes a power transmission state and a feedback state, and the power transmission state and the feedback state alternate.

[0008] The control circuit controls the power transmission circuit to be in power transmission state, and the feedback circuit is in standby state; the power transmission circuit converts the input voltage into alternating voltage to drive the isolation transformer, the isolation transformer transmits the primary side alternating voltage to the secondary side to form the secondary side alternating voltage, and the rectifier circuit converts the secondary side alternating voltage into DC voltage as the secondary side output voltage.

[0009] The control circuit monitors the duration of the power transmission state. When the set duration is reached, the control circuit controls the power transmission circuit to enter a sleep state.

[0010] The feedback circuit monitors the secondary voltage of the isolation transformer. When it is determined that the power transmission circuit has entered a sleep state, the feedback circuit enters a feedback state, generates a secondary feedback signal, and transmits the secondary feedback signal to the secondary side of the isolation transformer. The isolation transformer then transmits the secondary feedback signal to the primary side to form a primary feedback signal.

[0011] The control circuit receives the primary-side feedback signal and monitors the duration of the feedback state. The control circuit adjusts the power transmission circuit according to the primary-side feedback signal and the duration of the feedback state, controlling the power transmission circuit to remain in a sleep state or re-enter the power transmission state.

[0012] Furthermore, the first input port of the power transmission circuit is coupled to the first input voltage port, the second input port of the power transmission circuit is coupled to the second input voltage port, the third input port of the power transmission circuit is coupled to the output terminal of the control circuit, the first output port of the power transmission circuit is coupled to the first port of the primary winding of the isolation transformer, and the second output port of the power transmission circuit is coupled to the second port of the primary winding of the isolation transformer; the first input port of the control circuit is coupled to the first port of the primary winding of the isolation transformer, and the second input port of the control circuit is coupled to the second port of the primary winding of the isolation transformer; the first input port of the rectifier circuit is coupled to the first port of the secondary winding of the isolation transformer, the second input port of the rectifier circuit is coupled to the second port of the secondary winding of the isolation transformer, the first output port of the rectifier circuit is coupled to the positive terminal of the DC output voltage, and the second output port of the rectifier circuit is coupled to the negative terminal of the DC output voltage; the first input port of the feedback circuit is coupled to the positive terminal of the DC output voltage, the second input port of the feedback circuit is coupled to the negative terminal of the DC output voltage, the third input port and the first output port of the feedback circuit are coupled to the first port of the secondary winding of the isolation transformer, and the fourth input port and the second output port of the feedback circuit are coupled to the second port of the secondary winding of the isolation transformer.

[0013] Furthermore, the control circuit includes: a third comparison unit, a fourth comparison unit, an oscillation circuit, a counting circuit, and a control signal generation circuit. The inverting input terminal of the third comparison unit is coupled to a third reference voltage, and the non-inverting input terminal of the third comparison unit serves as the first input port of the control circuit and receives a first primary-side feedback signal. The output terminal of the third comparison unit is coupled to the first input port of the control signal generation circuit. The inverting input terminal of the fourth comparison unit is coupled to a fourth reference voltage, and the non-inverting input terminal of the fourth comparison unit serves as the second input port of the control circuit and receives a second primary-side feedback signal. The output terminal of the fourth comparison unit is coupled to the second input port of the control signal generation circuit. The output terminal of the oscillation circuit is coupled to the input terminal of the counting circuit, and the input terminal of the counting circuit is coupled to the third input port of the control signal generation circuit. The output port of the control signal generation circuit serves as the output terminal of the control circuit, outputting a control signal.

[0014] Furthermore, the oscillation circuit and the counting circuit are used to monitor the duration of the power transmission state and the duration of the feedback state. The third comparison unit and the fourth comparison unit receive the primary-side feedback signal. The oscillation circuit generates a system clock, the counting circuit generates a first set duration and a second set duration based on the system clock, and the control signal generation circuit generates corresponding control signals based on the first set duration and the second set duration. In the power transmission state, within the first set duration, the control signal generation circuit controls the power transmission circuit to be in the power transmission state. In the feedback state, the third comparison unit and the fourth comparison unit compare the signals. If, within the second set duration, the first primary-side feedback signal is greater than the third reference voltage an odd number of times or the second primary-side feedback signal is greater than the fourth reference voltage an odd number of times, the control signal generation circuit controls the power transmission circuit to remain in a sleep state. If the first primary-side feedback signal is greater than the third reference voltage an even number of times or the second primary-side feedback signal input terminal is greater than the fourth reference voltage an even number of times, the control signal generation circuit controls the power transmission circuit to enter the power transmission state.

[0015] The period of the alternating voltage is t1, the first set duration is n1 times the alternating voltage period t1, and the second set duration is n2 times the alternating voltage period t1; the value of n1 ranges from 10 to 20, and the value of n2 ranges from 2 to 3.

[0016] Furthermore, the feedback circuit includes: a voltage sampling circuit, a first comparison unit, a second comparison unit, a feedback state determination circuit, and a signal synthesis circuit; the first input port of the voltage sampling circuit is coupled to the positive terminal of the DC output voltage, the second input port of the voltage sampling circuit is coupled to the negative terminal of the DC output voltage, and the output terminal of the voltage sampling circuit is coupled to the positive input terminal of the first comparison unit and the inverting input terminal of the second comparison unit; the inverting input terminal of the first comparison unit is coupled to a first reference voltage, the output terminal of the first comparison unit is coupled to the first input port of the signal synthesis circuit, the positive input terminal of the second comparison unit is coupled to a second reference voltage, and the output terminal of the second comparison unit is coupled to the second input port of the signal synthesis circuit; the first input port of the feedback state determination circuit is coupled as the third input port of the feedback circuit and inputs a first input signal, the second input port of the feedback state determination circuit is coupled as the fourth input port of the feedback circuit and inputs a second input signal, and the output port of the feedback state determination circuit is coupled to the third input port of the signal synthesis circuit; the first output terminal of the signal synthesis circuit is served as the first output port of the feedback circuit and outputs a first secondary-side feedback signal, and the first output terminal of the signal synthesis circuit is served as the second output port of the feedback circuit and outputs a second secondary-side feedback signal.

[0017] Furthermore, in the feedback circuit, the feedback state determination circuit monitors the secondary voltage of the isolation transformer. When the time duration for which the voltage difference between the first input signal and the second input signal is less than the first voltage threshold exceeds the first time threshold, the power transmission circuit is determined to enter a sleep state, and the feedback circuit enters a feedback state. The first comparison unit compares the output sampled voltage with the first reference voltage. If the output sampled voltage is less than the first reference voltage within a second set time period, the signal synthesis circuit generates a first type of feedback signal. If the output sampled voltage is greater than the first reference voltage within the second set time period, the signal synthesis circuit generates a second type of feedback signal. After the signal synthesis circuit generates a second type of feedback signal once, the second comparator compares the output sampled voltage with the second reference voltage. If the output sampled voltage is less than the second reference voltage, the signal synthesis circuit generates a third type of feedback signal. The first type of feedback signal is a low-level signal, the second type of feedback signal is a high-level single-pulse signal, and the third type of feedback signal is a high-level single-pulse signal.

[0018] The first voltage threshold should be less than one-fifth of the amplitude of the alternating voltage on the secondary winding of the isolation transformer, and the first time threshold should be greater than one-half of the period t1 of the alternating voltage on the secondary winding.

[0019] The signal synthesis circuit includes: a pulse signal generation circuit, a first feedback PMOS transistor, and a second feedback PMOS transistor. The first, second, and third input ports of the pulse signal generation circuit serve as the first, second, and third input ports of the signal synthesis circuit, respectively. The first output terminal of the pulse signal generation circuit is coupled to the gate of the first feedback PMOS transistor, and the second output terminal of the pulse signal generation circuit is coupled to the gate of the second feedback PMOS transistor. The sources of the first and second feedback PMOS transistors are coupled to a DC output voltage. The drain of the first feedback PMOS transistor serves as the first output terminal of the signal synthesis circuit, and the drain of the second feedback PMOS transistor serves as the second output terminal of the signal synthesis circuit. The first and second feedback PMOS transistors are turned on or off according to the output signals of the first comparison unit, the second comparison unit, and the feedback state determination circuit, respectively, generating a first-type feedback signal, a second-type feedback signal, or a third-type feedback signal at the drain of the corresponding feedback PMOS transistor.

[0020] Based on the above technical solution, the beneficial effects of the present invention are as follows:

[0021] This invention provides an isolated power supply that alternates between power transfer and feedback states. This allows the same isolation transformer to be used for both power transfer from the primary circuit to the secondary circuit and signal feedback from the secondary circuit to the primary circuit, ensuring stable output voltage under different load and input voltage conditions. Furthermore, the control mode of this invention reduces the power supply switching frequency under light loads, maintaining high conversion efficiency even under light load conditions. In applications such as isolated switching power supplies, this invention eliminates the need for additional signal isolation devices, further improving power density. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the structure of a traditional isolated power supply in the prior art.

[0023] Figure 2 This is a schematic diagram of the structure of the isolated power supply provided by the present invention.

[0024] Figure 3 This is a schematic diagram of the feedback circuit in the isolated power supply provided by the present invention.

[0025] Figure 4 This is a schematic diagram of the control circuit in the isolated power supply provided by the present invention.

[0026] Figure 5 This is a circuit schematic diagram of an isolated voltage converter based on the present invention.

[0027] Figure 6 The diagram shows the voltage and current waveforms of the isolated voltage converter based on the present invention. Detailed Implementation

[0028] To make the objectives, technical solutions, and beneficial effects of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0029] This embodiment provides an isolated power supply, such as Figure 2 As shown, it specifically includes: an isolation transformer, a power transmission circuit and a control circuit located on the primary side of the isolation transformer, and a rectifier circuit and a feedback circuit located on the secondary side of the isolation transformer. The isolation power supply includes a power transmission state and a feedback state.

[0030] Power transfer status: The control circuit keeps the power transfer circuit in the working state. The power transfer circuit converts the primary input voltage into an alternating voltage, drives the isolation transformer, and the isolation transformer transfers the primary alternating voltage to the secondary side to form the secondary alternating voltage. The rectifier circuit converts the secondary alternating voltage into a DC voltage as the secondary output voltage. The control circuit monitors the duration of the power transfer status, and the feedback circuit is in standby mode and keeps monitoring the secondary voltage of the isolation transformer to determine the status of the power transfer circuit.

[0031] Feedback State: The control circuit keeps the power transmission circuit in a sleep state, and the power transmission circuit outputs high impedance; the feedback circuit is in the working state, generating a secondary feedback signal based on information such as the secondary DC output voltage, and transmitting the secondary feedback signal to the secondary side of the isolation transformer. The isolation transformer transmits the secondary feedback signal to the primary side to form the primary feedback signal. The feedback circuit also monitors the secondary voltage of the isolation transformer to determine the state of the power transmission circuit; the control circuit monitors the duration of the feedback state and maintains monitoring of the primary voltage of the isolation transformer to receive the primary feedback signal.

[0032] Power transmission state switching to feedback state: The control circuit monitors the duration of the power transmission state. After the first set duration is reached, the control circuit controls the power transmission circuit to enter the sleep state, and the power transmission circuit outputs high impedance. The feedback circuit enters the working state and enters the feedback state after determining that the power transmission circuit is in the sleep state by monitoring the secondary voltage of the isolation transformer.

[0033] Feedback state switching to power transmission state: The control circuit monitors the duration of the feedback state and receives the primary-side feedback signal. When the primary-side feedback signal is a first-type feedback signal and the feedback state duration reaches a second set duration, the control circuit controls the power transmission circuit to enter the working state. When the primary-side feedback signal is a first-type feedback signal and the feedback state duration does not reach the second set duration, the control circuit controls the power transmission circuit to remain in the sleep state. When the primary-side feedback signal is a second-type feedback signal, the control circuit controls the power transmission circuit to remain in the sleep state. When the primary-side feedback signal is a third-type feedback signal, the control circuit controls the power transmission circuit to enter the working state. After the feedback circuit determines that the power transmission circuit is in the working state by monitoring the secondary voltage of the isolation transformer, the feedback circuit enters the standby state.

[0034] In an optional embodiment, the period of the alternating voltage is t1, the first set duration is n1 times the alternating voltage period t1, and the second set duration is n2 times the alternating voltage period t1; optionally, the value of n1 is in the range of 10~20, and the value of n2 is in the range of 2~3.

[0035] In an optional embodiment, the first input port of the power transmission circuit is coupled to the first input voltage port, the second input port of the power transmission circuit is coupled to the second input voltage port, the third input port of the power transmission circuit is coupled to the output terminal of the control circuit, the first output port of the power transmission circuit is coupled to the first port of the primary winding of the isolation transformer, and the second output port of the power transmission circuit is coupled to the second port of the primary winding of the isolation transformer; the first input port of the control circuit is coupled to the first port of the primary winding of the isolation transformer, and the second input port of the control circuit is coupled to the second port of the primary winding of the isolation transformer; the first input port of the rectifier circuit is coupled to the first port of the secondary winding of the isolation transformer, the second input port of the rectifier circuit is coupled to the second port of the secondary winding of the isolation transformer, the first output port of the rectifier circuit is coupled to the positive terminal of the DC output voltage, and the second output port of the rectifier circuit is coupled to the negative terminal of the DC output voltage; the first input port of the feedback circuit is coupled to the positive terminal of the DC output voltage, the second input port of the feedback circuit is coupled to the negative terminal of the DC output voltage, the third input port and the first output port of the feedback circuit are coupled to the first port of the secondary winding of the isolation transformer, and the fourth input port and the second output port of the feedback circuit are coupled to the second port of the secondary winding of the isolation transformer.

[0036] In an optional implementation, the feedback circuit is as follows: Figure 3As shown, it includes: a voltage sampling circuit, a first comparison unit, a second comparison unit, a feedback state determination circuit, and a signal synthesis circuit; the first input port of the voltage sampling circuit is coupled to the positive terminal of the DC output voltage, the second input port of the voltage sampling circuit is coupled to the negative terminal of the DC output voltage, and the output terminal of the voltage sampling circuit is coupled to the positive input terminal of the first comparison unit and the inverting input terminal of the second comparison unit; the inverting input terminal of the first comparison unit is coupled to a first reference voltage, the output terminal of the first comparison unit is coupled to the first input port of the signal synthesis circuit, the positive input terminal of the second comparison unit is coupled to a second reference voltage, and the output terminal of the second comparison unit is coupled to the second input port of the signal synthesis circuit; the first input port of the feedback state determination circuit is coupled to a first input signal, the second input port of the feedback state determination circuit is coupled to a second input signal, and the output port of the feedback state determination circuit is coupled to the third input port of the signal synthesis circuit; the first output terminal of the signal synthesis circuit is coupled to the first secondary-side feedback signal output terminal, and the first output terminal of the signal synthesis circuit is coupled to the second secondary-side feedback signal output terminal.

[0037] The feedback circuit generates corresponding secondary-side feedback signals based on the DC output voltage, the first input signal, and the second input signal. The feedback state determination circuit determines whether to enter the feedback state based on the feedback state input signal. When the system enters the feedback state, the first comparison unit compares the output sample voltage with the first reference voltage. If the output sample voltage is less than the first reference voltage within a second set time period, the signal synthesis circuit generates a first-type feedback signal, and the system enters the power transmission state. If the output sample voltage is greater than the first reference voltage within the second set time period, the signal synthesis circuit generates a second-type feedback signal, and the system maintains the feedback state. After the signal synthesis circuit generates a second-type feedback signal once, the second comparator compares the output sample voltage with the second reference voltage. If the output sample voltage is less than the second reference voltage, the signal synthesis circuit generates a third-type feedback signal, and the system enters the power transmission state. More precisely, the feedback circuit can only generate a third-type feedback signal as a secondary-side feedback signal after generating a second-type feedback signal as a secondary-side feedback signal.

[0038] Furthermore, the first type of feedback signal is a low-level signal, the second type of feedback signal is a high-level single-pulse signal, and the third type of feedback signal is a high-level single-pulse signal; the first reference voltage is greater than the second reference voltage.

[0039] Furthermore, the first input signal of the feedback state determination circuit is coupled to the first port of the secondary winding of the isolation transformer, and the second input signal of the feedback state determination circuit is coupled to the second port of the secondary winding of the isolation transformer. When the time length during which the voltage difference between the first input signal and the second input signal is less than the first voltage threshold exceeds the first time threshold, the feedback circuit determines that it has entered the feedback state; otherwise, it does not enter the feedback state. Preferably, the first voltage threshold should be less than one-fifth of the amplitude of the alternating voltage on the secondary winding of the isolation transformer, and the first time threshold should be greater than one-half of the period t1 of the alternating voltage on the secondary winding.

[0040] Furthermore, the signal synthesis circuit includes: a pulse signal generation circuit, a first feedback PMOS transistor, and a second feedback PMOS transistor. The first input port, the second input port, and the third input port of the pulse signal generation circuit are respectively coupled to the first input port, the second input port, and the third input port of the signal synthesis circuit. The first output terminal of the pulse signal generation circuit is coupled to the gate of the first feedback PMOS transistor, and the second output terminal of the pulse signal generation circuit is coupled to the gate of the second feedback PMOS transistor. The sources of the first feedback PMOS transistor and the second feedback PMOS transistor are coupled to the DC output voltage. The drain of the first feedback PMOS transistor is coupled to the first secondary-side feedback signal output terminal, and the drain of the second feedback PMOS transistor is coupled to the second secondary-side feedback signal output terminal.

[0041] The pulse signal generation circuit controls the first feedback PMOS transistor and the second feedback PMOS transistor to turn on and off respectively according to the output signals of the first comparison unit, the second comparison unit and the feedback state determination circuit, thereby generating corresponding first type feedback signal, second type feedback signal and third type feedback signal at the drain of the corresponding feedback PMOS transistor as secondary side feedback signals.

[0042] In an optional implementation, the control circuit is as follows: Figure 4 As shown, the system includes: a third comparison unit, a fourth comparison unit, an oscillation circuit, a counting circuit, and a control signal generation circuit. The inverting input terminal of the third comparison unit is coupled to a third reference voltage, the non-inverting input terminal of the third comparison unit is coupled to a first primary-side feedback signal input terminal, and the output terminal of the third comparison unit is coupled to a first input port of the control signal generation circuit. The inverting input terminal of the fourth comparison unit is coupled to a fourth reference voltage, the non-inverting input terminal of the fourth comparison unit is coupled to a second primary-side feedback signal input terminal, and the output terminal of the fourth comparison unit is coupled to a second input port of the control signal generation circuit. The output terminal of the oscillation circuit is coupled to an input terminal of the counting circuit, and the input terminal of the counting circuit is coupled to a third input port of the control signal generation circuit. The output port of the control signal generation circuit generates a control signal.

[0043] The oscillation circuit and the counting circuit are used to monitor the duration of the power transmission state and the duration of the feedback state. The third comparison unit and the fourth comparison unit receive the primary-side feedback signal to switch the operating state of the control signal generation circuit, thereby controlling the operating state of the power transmission circuit. The oscillation circuit generates a system clock, the counting circuit generates a first set duration and a second set duration based on the system clock, and the control signal generation circuit generates corresponding control signals based on the first set duration and the second set duration. In the power transmission state, the control signal generation circuit controls the power transmission circuit to be in the power transmission state within the first set duration. In the feedback state, the third comparison unit and the fourth comparison unit compare the voltages. If the first primary-side feedback signal is greater than the third reference voltage an odd number of times, or the second primary-side feedback signal is greater than the fourth reference voltage an odd number of times, the control signal generation circuit controls the power transmission circuit to remain in a sleep state. If the first primary-side feedback signal is greater than the third reference voltage an even number of times, or the second primary-side feedback signal input terminal is greater than the fourth reference voltage an even number of times, the control signal generation circuit controls the power transmission circuit to enter the power transmission state.

[0044] Furthermore, the first primary-side feedback signal input terminal is coupled to the first port of the primary winding of the isolation transformer, and the second primary-side feedback signal input terminal is coupled to the second port of the primary winding of the isolation transformer; the first secondary-side feedback signal output terminal is coupled to the first port of the secondary winding of the isolation transformer, and the second secondary-side feedback signal output terminal is coupled to the second port of the secondary winding of the isolation transformer.

[0045] Furthermore, the third reference voltage is equal to the fourth reference voltage.

[0046] Specifically, this embodiment provides an isolated voltage converter based on the aforementioned isolated power supply, such as... Figure 5 As shown, it consists of a power transmission circuit, a control circuit, a rectifier circuit, a feedback circuit, and a load;

[0047] The power transmission circuit includes: a PMOS type first MOSFET P1, a PMOS type second MOSFET P2, an NMOS type third MOSFET N1, an NMOS type fourth MOSFET N2, and a drive signal generation circuit; the sources of the first and second MOSFETs are coupled to the positive terminal of the DC power supply voltage, the sources of the third and fourth MOSFETs are coupled to the negative terminal of the DC power supply voltage, the drains of the first and third MOSFETs are coupled to the first terminal of the primary winding of the transformer, and the drains of the third and fourth MOSFETs are coupled to the second terminal of the primary winding of the transformer; the gates of the first, second, third, and fourth MOSFETs are connected to the drive signal from the drive signal generation circuit; optionally, the control signal set in the embodiment causes the first and fourth MOSFETs to be alternately turned on with the second and third MOSFETs, the voltage across the primary winding of the transformer alternately changes between +VDD and -VDD with time, and the secondary winding induces an alternating voltage as the input voltage of the rectifier circuit;

[0048] The rectifier circuit includes: a PMOS type fifth MOSFET P1, a PMOS type sixth MOSFET P2, an NMOS type seventh MOSFET N1, an NMOS type eighth MOSFET N2, and a rectifier drive circuit; the sources of the fifth and sixth MOSFETs are coupled to the positive terminal of the DC output voltage, the sources of the seventh and eighth MOSFETs are coupled to the negative terminal of the DC output voltage, the drains of the fifth and seventh MOSFETs are coupled to the first terminal of the secondary winding of the transformer, and the drains of the sixth and eighth MOSFETs are coupled to the second terminal of the primary winding of the transformer; the gates of the fifth, sixth, seventh, and eighth MOSFETs are connected to a drive signal from the rectifier drive circuit; the drive signal of the rectifier drive circuit should enable the fifth (or sixth) MOSFET when the drain voltage of the fifth (or sixth) MOSFET is greater than the source voltage, and turn off the fifth (or sixth) MOSFET otherwise; and enable the seventh (or eighth) MOSFET when the source voltage of the seventh (or eighth) MOSFET is greater than the drain voltage, and turn off the seventh (or eighth) MOSFET otherwise, so as to achieve its rectification function;

[0049] Optionally, in the embodiment, the feedback circuit is composed of, for example, Figure 3 The described feedback circuit configuration, in the embodiment, the control circuit consists of... Figure 4 The control circuit described is configured as follows.

[0050] like Figure 6 The figure shown is a voltage and current waveform diagram of this embodiment. It can be seen that the isolated voltage converter realizes the regulation of DC output voltage. The voltage regulation feedback control is completed by the secondary circuit sending a feedback signal to the primary circuit through the power transmission isolation transformer, without the need for additional signal isolation devices.

[0051] The above description is merely a specific embodiment of the present invention. Any feature disclosed in this specification may be replaced by other equivalent or similar features unless otherwise specified. All disclosed features, or steps in all methods or processes, may be combined in any way except for mutually exclusive features and / or steps.

Claims

1. An isolated power supply, comprising: An isolation transformer, a power transmission circuit and a control circuit located on the primary side of the isolation transformer, and a rectifier circuit and a feedback circuit located on the secondary side of the isolation transformer; characterized in that: The isolated power supply includes a power transmission state and a feedback state, and the power transmission state and the feedback state alternate. The control circuit controls the power transmission circuit to be in power transmission state, and the feedback circuit is in standby state; the power transmission circuit converts the input voltage into alternating voltage to drive the isolation transformer, the isolation transformer transmits the primary side alternating voltage to the secondary side to form the secondary side alternating voltage, and the rectifier circuit converts the secondary side alternating voltage into DC voltage as the secondary side output voltage. The control circuit monitors the duration of the power transmission state. When the set duration is reached, the control circuit controls the power transmission circuit to enter a sleep state. The feedback circuit monitors the secondary voltage of the isolation transformer. When it is determined that the power transmission circuit has entered a sleep state, the feedback circuit enters a feedback state, generates a secondary feedback signal, and transmits the secondary feedback signal to the secondary side of the isolation transformer. The isolation transformer then transmits the secondary feedback signal to the primary side to form a primary feedback signal. The control circuit receives the primary-side feedback signal and monitors the duration of the feedback state. The control circuit adjusts the power transmission circuit according to the primary-side feedback signal and the duration of the feedback state, controlling the power transmission circuit to remain in a sleep state or re-enter the power transmission state. The first input port of the power transmission circuit is coupled to the first input voltage port, the second input port of the power transmission circuit is coupled to the second input voltage port, the third input port of the power transmission circuit is coupled to the output terminal of the control circuit, the first output port of the power transmission circuit is coupled to the first port of the primary winding of the isolation transformer, and the second output port of the power transmission circuit is coupled to the second port of the primary winding of the isolation transformer; the first input port of the control circuit is coupled to the first port of the primary winding of the isolation transformer, and the second input port of the control circuit is coupled to the second port of the primary winding of the isolation transformer; the first input port of the rectifier circuit is coupled to the first port of the secondary winding of the isolation transformer, the second input port of the rectifier circuit is coupled to the second port of the secondary winding of the isolation transformer, the first output port of the rectifier circuit is coupled to the positive terminal of the DC output voltage, and the second output port of the rectifier circuit is coupled to the negative terminal of the DC output voltage; the first input port of the feedback circuit is coupled to the positive terminal of the DC output voltage, the second input port of the feedback circuit is coupled to the negative terminal of the DC output voltage, the third input port and the first output port of the feedback circuit are coupled to the first port of the secondary winding of the isolation transformer, and the fourth input port and the second output port of the feedback circuit are coupled to the second port of the secondary winding of the isolation transformer; The control circuit includes: a third comparison unit, a fourth comparison unit, an oscillation circuit, a counting circuit, and a control signal generation circuit. The inverting input terminal of the third comparison unit is coupled to a third reference voltage, and the non-inverting input terminal of the third comparison unit serves as the first input port of the control circuit and receives a first primary-side feedback signal. The output terminal of the third comparison unit is coupled to the first input port of the control signal generation circuit. The inverting input terminal of the fourth comparison unit is coupled to a fourth reference voltage, and the non-inverting input terminal of the fourth comparison unit serves as the second input port of the control circuit and receives a second primary-side feedback signal. The output terminal of the fourth comparison unit is coupled to the second input port of the control signal generation circuit. The output terminal of the oscillation circuit is coupled to the input terminal of the counting circuit, and the input terminal of the counting circuit is coupled to the third input port of the control signal generation circuit. The output port of the control signal generation circuit serves as the output terminal of the control circuit, outputting a control signal. The feedback circuit includes: a voltage sampling circuit, a first comparison unit, a second comparison unit, a feedback state determination circuit, and a signal synthesis circuit; the first input port of the voltage sampling circuit is coupled to the positive terminal of the DC output voltage, the second input port of the voltage sampling circuit is coupled to the negative terminal of the DC output voltage, and the output terminal of the voltage sampling circuit is coupled to the positive input terminal of the first comparison unit and the inverting input terminal of the second comparison unit; the inverting input terminal of the first comparison unit is coupled to a first reference voltage, the output terminal of the first comparison unit is coupled to the first input port of the signal synthesis circuit, the positive input terminal of the second comparison unit is coupled to a second reference voltage, and the output terminal of the second comparison unit is coupled to the second input port of the signal synthesis circuit; the first input port of the feedback state determination circuit is coupled as the third input port of the feedback circuit and inputs a first input signal, the second input port of the feedback state determination circuit is coupled as the fourth input port of the feedback circuit and inputs a second input signal, and the output port of the feedback state determination circuit is coupled to the third input port of the signal synthesis circuit; the first output terminal of the signal synthesis circuit is served as the first output port of the feedback circuit and outputs a first secondary-side feedback signal, and the first output terminal of the signal synthesis circuit is served as the second output port of the feedback circuit and outputs a second secondary-side feedback signal.

2. The isolated power supply according to claim 1, characterized in that, The oscillation circuit and counting circuit are used to monitor the duration of the power transmission state and the duration of the feedback state. The third comparison unit and the fourth comparison unit receive the primary-side feedback signal. The oscillation circuit generates a system clock, the counting circuit generates a first set duration and a second set duration based on the system clock, and the control signal generation circuit generates corresponding control signals based on the first set duration and the second set duration. In the power transmission state, within the first set duration, the control signal generation circuit controls the power transmission circuit to be in the power transmission state. In the feedback state, the third comparison unit and the fourth comparison unit compare the signals. If, within the second set duration, the first primary-side feedback signal is greater than the third reference voltage an odd number of times or the second primary-side feedback signal is greater than the fourth reference voltage an odd number of times, the control signal generation circuit controls the power transmission circuit to remain in a sleep state. If the first primary-side feedback signal is greater than the third reference voltage an even number of times or the second primary-side feedback signal input terminal is greater than the fourth reference voltage an even number of times, the control signal generation circuit controls the power transmission circuit to enter the power transmission state.

3. The isolated power supply according to claim 2, characterized in that, The period of the alternating voltage is t1, the first set duration is n1 times the alternating voltage period t1, and the second set duration is n2 times the alternating voltage period t1; the value of n1 ranges from 10 to 20, and the value of n2 ranges from 2 to 3.

4. The isolated power supply according to claim 1, characterized in that, In the feedback circuit, the feedback state determination circuit monitors the secondary voltage of the isolation transformer. When the time length during which the voltage difference between the first input signal and the second input signal is less than the first voltage threshold exceeds the first time threshold, the feedback circuit enters the feedback state when it is determined that the power transmission circuit has entered the sleep state. The first comparison unit compares the output sampled voltage with the first reference voltage. If the output sampled voltage is less than the first reference voltage within a second set time period, the signal synthesis circuit generates a first type of feedback signal. If the output sampled voltage is greater than the first reference voltage within the second set time period, the signal synthesis circuit generates a second type of feedback signal. After the signal synthesis circuit generates a second type of feedback signal once, the second comparator compares the output sampled voltage with the second reference voltage. If the output sampled voltage is less than the second reference voltage, the signal synthesis circuit generates a third type of feedback signal. The first type of feedback signal is a low-level signal, the second type of feedback signal is a high-level single-pulse signal, and the third type of feedback signal is a high-level single-pulse signal.

5. The isolated power supply according to claim 4, characterized in that, The first voltage threshold should be less than one-fifth of the amplitude of the alternating voltage on the secondary winding of the isolation transformer, and the first time threshold should be greater than one-half of the period t1 of the alternating voltage on the secondary winding.

6. The isolated power supply according to claim 1, characterized in that, The signal synthesis circuit includes: a pulse signal generation circuit, a first feedback PMOS transistor, and a second feedback PMOS transistor. The first, second, and third input ports of the pulse signal generation circuit serve as the first, second, and third input ports of the signal synthesis circuit, respectively. The first output terminal of the pulse signal generation circuit is coupled to the gate of the first feedback PMOS transistor, and the second output terminal of the pulse signal generation circuit is coupled to the gate of the second feedback PMOS transistor. The sources of the first and second feedback PMOS transistors are coupled to a DC output voltage. The drain of the first feedback PMOS transistor serves as the first output terminal of the signal synthesis circuit, and the drain of the second feedback PMOS transistor serves as the second output terminal of the signal synthesis circuit. The first and second feedback PMOS transistors are turned on or off according to the output signals of the first comparison unit, the second comparison unit, and the feedback state determination circuit, respectively, generating a first-type feedback signal, a second-type feedback signal, or a third-type feedback signal at the drain of the corresponding feedback PMOS transistor.

Images