High-efficiency and high-precision isolated multi-output power supply structure and working method

Abstract

The invention provides a high-efficiency and high-precision isolated multi-output power supply structure and a working method, and the structure comprises a square wave circuit with fixed duty ratio output, a switch MOS tube Q1, a reset diode D4, a first transformer T1, a second transformer T2, a third transformer T3, and a three-way output circuit unit which is internally provided with a synchronous buck chip. By adopting the circuit structure, the problem of load imbalance among three paths of output is solved, the three paths of output can be independently loaded or unloaded, and the output voltage precision is high; the back stage adopts a synchronous buck chip, so that the conversion efficiency is high, and the product loss is small; meanwhile, the circuit structure is simplified, the number of used components is small, and miniaturization integration of the circuit is facilitated.

Description

Technical Field

[0001] The invention belongs to the technical field of power supply, and relates to a high-efficiency, high-precision isolated multi-channel output power supply structure and a working method. Background Art

[0002] With the development of electronic technology, modern electronic devices are becoming increasingly complex, and the required power supply voltages vary from 2.5V to 12V. In the early days, people combined several independent DC / DC converters together to obtain multi-channel output power supplies. This method is not only costly but also bulky, and cannot meet the needs of modularization and miniaturization of modern electronic equipment. Therefore, multi-channel output technology is widely used. There are two types of miniaturized multi-channel output power supply design schemes: single-ended flyback and flybuck. The single-ended flyback topology has a simple circuit, a small number of components, and does not require an additional magnetic reset circuit on the primary side of the transformer, which can meet the requirements of miniaturization. In a multi-channel output environment, the low-voltage and high-current circuit is usually used as the main circuit for feedback, and the auxiliary output is only stabilized by controlling the number of transformer turns. For example Figure 1 It is a single-ended flyback switching power supply with two outputs, V O1 For the main output, V O2 For auxiliary output, when V O1 When the input voltage or load changes, the duty cycle is changed through the feedback loop so that V O1 Has a higher voltage regulation accuracy; while V O2 It is an open-loop system. When the input voltage or load changes, the duty cycle cannot be changed. The output voltage will drift and cannot meet the requirements of high-precision output voltage. Figure 2 As shown in the figure, a multi-winding transformer can be used to generate a multi-winding isolated output, which is simple to use and has few external components. Flybuck can stabilize the primary output, and the secondary isolated output can "follow" the stabilized primary output. Factors such as input and output voltage duty cycle and transformer leakage inductance will reduce the secondary output voltage regulation performance. This solution is only used in situations where the input voltage and output voltage meet a certain duty cycle.

[0003] The existing single-ended flyback multi-channel output solution is suitable for the occasions where each channel load is balanced. Only the main channel output is feedback controlled, and the other outputs are kept relatively stable according to the voltage balance relationship of the transformer winding. When the multi-channel load is unbalanced, the auxiliary channel output voltage will have a large deviation and cannot meet the high-precision output voltage requirements; the flybuck multi-channel output solution is simple and easy to use, and is convenient for miniaturization and integration, but the secondary output voltage regulation performance is restricted by factors such as input and output duty cycle and transformer leakage inductance. Summary of the invention

[0004] In view of the problems existing in the prior art, the present invention provides a high-efficiency, high-precision isolated multi-channel output power supply structure and working method, designs a circuit solution for unbalanced use of loads on each channel in a multi-channel output environment, meets the requirements of high-precision output voltage and good cross-regulation rate, and considers the requirements of product miniaturization and integration at the same time, requiring the circuit structure to be as simple as possible.

[0005] The present invention is achieved through the following technical solutions: A high-efficiency, high-precision isolated multi-output power supply structure, including: A square wave circuit with a fixed duty cycle output, a switch MOS tube Q1, a reset diode D4, a first transformer T1, a second transformer T2, a third transformer T3 and a three-way output circuit unit; The square wave circuit with fixed duty cycle output is connected to one end of the driver U2, the other end of the driver U2 is connected to the gate of the switch MOS tube Q1, and the drain of the switch MOS tube Q1 is respectively connected to the 6 ends on one side of the primary winding of the first transformer T1, the second transformer T2 and the third transformer T3; The terminal 5 on one side of the primary winding of the first transformer T1 and the second transformer T2 is connected to the input voltage terminal Vin; The secondary winding sides of the first transformer T1, the second transformer T2 and the third transformer T3 are respectively connected to the input end of each output circuit unit; the output end of each output circuit unit is connected to the output voltage end; The 2 ends on both sides of the primary windings of the first transformer T1, the second transformer T2 and the third transformer T3 are connected to the anode of the reset diode D4; the cathode of the reset diode D4 is connected to the 5 end on one side of the primary winding of the third transformer T3, and a synchronous buck chip is provided in the three-way output circuit unit.

[0006] Preferably, the square wave circuit with fixed duty cycle output includes a multivibrator U1, an external resistor and a first capacitor C1; One end of the first capacitor C1 is connected to the input voltage terminal Vin, and the other end of the first capacitor C1 is grounded GNDin; One end of the multivibrator U1 is connected to the input voltage terminal Vin, and the other end of the multivibrator U1 is connected to the driver U2; the multivibrator U1 is connected to an external resistor.

[0007] Preferably, the output circuit unit includes a first output circuit unit, a second output circuit unit and a third output circuit unit; One end of the first output circuit unit is connected to the secondary winding side of the first transformer T1, and the other end of the first output circuit unit is connected to the first voltage output Vo1 end; One end of the second output circuit unit is connected to the secondary winding side of the second transformer T2, and the other end of the first output circuit unit is connected to the second voltage output Vo2 end; One end of the third output circuit unit is connected to the secondary winding side of the third transformer T3, and the other end of the third output circuit unit is connected to the third voltage output Vo3 end.

[0008] Preferably, the first output circuit unit includes a first rectifier tube D1, a first synchronous buck chip U3, a first filter capacitor C6 and a second capacitor C12; The cathode of the first rectifier tube D1 is connected to one end of the first filter capacitor C6 and the first synchronous buck chip U3; The anode of the first rectifier tube D1 is connected to the 3 end of the secondary winding side of the first transformer T1; the 4 end of the secondary winding side of the first transformer T1 is connected to the other end of the first filter capacitor C6, the first synchronous buck chip U3, one end of the second capacitor C12 and the negative end of the first voltage output Vo1; the other end of the first synchronous buck chip U3 and the second capacitor C12 is connected to the positive end of the first voltage output Vo1.

[0009] Preferably, the second output circuit unit includes a second rectifier tube D2, a second synchronous buck chip U4, a second filter capacitor C7 and a third capacitor C13; The cathode of the second rectifier tube D2 is connected to one end of the second filter capacitor C7 and the second synchronous buck chip U4; The anode of the second rectifier tube D2 is connected to the 3 end of the secondary winding side of the second transformer T2; the 4 end of the secondary winding side of the second transformer T2 is connected to the other end of the second filter capacitor C7, the second synchronous buck chip U4, one end of the third capacitor C13 and the negative end of the second voltage output Vo2; the other end of the second synchronous buck chip U4 and the third capacitor C13 is connected to the positive end of the second voltage output Vo2.

[0010] Preferably, the third output circuit unit includes a third rectifier tube D3, a third synchronous buck chip U5, a third filter capacitor C8 and a fourth capacitor C14; The cathode of the third rectifier tube D3 is connected to one end of the third filter capacitor C8 and the third synchronous buck chip U5; The anode of the third rectifier tube D3 is connected to the 3rd end of the secondary winding side of the third transformer T3; the 4th end of the secondary winding side of the third transformer T3 is connected to the other end of the third filter capacitor C8, the third synchronous buck chip U5, one end of the fourth capacitor C14; and the negative end of the third voltage output Vo3; the other end of the third synchronous buck chip U5 and the fourth capacitor C13 is connected to the positive end of the third voltage output Vo3.

[0011] Preferably, one end of both sides of the primary windings of the first transformer T1 , the second transformer T2 and the third transformer T3 are grounded.

[0012] Preferably, the multi-channel output power supply structure adopts a two-stage cascade structure, the first stage realizes multi-channel low-impedance isolated output of the power supply, and the second stage realizes voltage stabilization control of each channel.

[0013] Preferably, the multi-output power supply structure adopts a single-ended forward topology. A method for operating a high-efficiency, high-precision isolated multi-output power supply structure, comprising: The square wave circuit with fixed duty cycle output is driven by driver U2 to control the on and off of the switch MOS tube Q1. When the square wave circuit with fixed duty cycle output is at a high level, the switch MOS tube Q1 is turned on, and the energy of the first transformer T1, the second transformer T2 and the third transformer T3 is transferred from the primary winding side to the secondary winding side. The induced voltage on the secondary winding side is rectified and filtered by the three-way output circuit unit, and then outputs a high-precision output voltage through the synchronous buck chip; When the square wave circuit with a fixed duty cycle output is at a low level, the control switch MOS tube Q1 is turned off, the same-name terminals of the first transformer T1, the second transformer T2 and the third transformer T3 are at a low level, the reset diode D4 is turned on, the magnetic cores of the first transformer T1, the second transformer T2 and the third transformer T3 are reset, the rectification on the secondary winding side of the first transformer T1, the second transformer T2 and the third transformer T3 is turned off, and the output terminal of the synchronous buck chip of the three-way output circuit unit is discharged to provide a stable output voltage.

[0014] Compared with the prior art, the present invention has the following beneficial technical effects: The present invention provides a high-efficiency, high-precision isolated multi-channel output power supply structure, including a square wave circuit with a fixed duty cycle output, a switch MOS tube Q1, a reset diode D4, a first transformer T1, a second transformer T2, a third transformer T3 and a three-channel output circuit unit, wherein a synchronous buck chip is arranged in the three-channel output circuit unit, and the circuit structure is adopted to solve the problem of load imbalance between the three-channel outputs, and the three-channel outputs can be loaded or unloaded separately, and the output voltage precision is high; the back stage adopts a synchronous buck chip, which has high conversion efficiency and low product loss; at the same time, the circuit structure is simplified, the number of components used is small, and the miniaturization integration of the circuit is convenient. The present invention is improved according to the single-ended forward topology structure, omitting the energy storage inductor and the freewheeling diode, and adopting a fixed duty cycle signal drive. Since the single-ended forward power topology only retains the output rectifier diode, when the front-stage power switch is turned on, the energy of the primary power supply is first coupled through the transformer winding, and then directly output through the rectifier diode, with extremely small input impedance, and the load change has the least effect on the output voltage, which is particularly suitable for the front-stage power output in the cascade topology. Under a fixed duty cycle, the output voltage of the first-stage isolated power conversion will change with the input voltage. Therefore, a high-efficiency synchronous buck chip is used for secondary voltage regulation, which has extremely high conversion efficiency compared to linear voltage regulation.

[0015] Furthermore, the present invention adopts a two-stage cascade structure, the first stage realizes multi-channel low-impedance isolated output of the power supply, and the second stage realizes voltage stabilization control of each channel, which not only improves the efficiency and stability of power management, but also enhances the adaptability and reliability of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a two-way output single-ended flyback switching power supply in the prior art; Figure 2 A multi-channel output flybuck converter according to the prior art; Figure 3 This is the schematic diagram of the multi-channel output power supply structure; Figure 4 This is a diagram showing an application example of the multi-output power supply structure of the present invention. DETAILED DESCRIPTION

[0017] The present invention is further described in detail below in conjunction with specific embodiments, which are intended to explain the present invention rather than to limit it.

[0018] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0019] The present invention provides a high-efficiency, high-precision isolated multi-channel output power supply structure. The multi-channel output circuit design scheme of the present invention is suitable for situations where the load between the multi-channel outputs is unbalanced and the voltage and current regulation rate requirements are high. The present invention adopts a two-stage cascade structure, the first stage realizes the multi-channel low-impedance isolated output of the power supply, and the second stage realizes the voltage stabilization control of each channel. Specifically, it is improved according to the single-ended forward topology structure, omitting the energy storage inductor and the freewheeling diode, and adopting a fixed duty cycle signal drive. Since the single-ended forward power topology only retains the output rectifier diode, when the front-stage power switch is turned on, the energy of the primary power supply is first coupled through the transformer winding, and then directly output through the rectifier diode, with extremely small input impedance, and the load change has the least effect on the output voltage, which is particularly suitable for the front-stage power output in the cascade topology. Under a fixed duty cycle, the output voltage of the first-stage isolated power conversion will change with the input voltage, so a high-efficiency synchronous buck chip is used for secondary voltage stabilization, which has extremely high conversion efficiency compared to linear voltage stabilization.

[0020] Line plan such as Figure 3 As shown, it includes a multivibrator (U1), a driver (U2), a switch MOS tube (Q1), a synchronous buck buck chip (a first synchronous buck buck chip U3, a second synchronous buck buck chip U4, and a third synchronous buck buck chip U5), capacitors (a first capacitor C1, a first filter capacitor C6, a second filter capacitor C7, a third filter capacitor C8, a second capacitor C12, a third capacitor C13, and a fourth capacitor C14), rectifiers (a first rectifier D1, a second rectifier D2, and a third rectifier D3), and transformers (a first transformer T1, a second transformer T2, and a third transformer T3).

[0021] The multivibrator U1 and peripheral resistors and capacitors form a square wave circuit with a fixed duty cycle output. The input voltage terminal Vin is connected to one end of the first capacitor C1, the multivibrator U1, the 5th terminal of the primary winding side of the first transformer T1 and the 5th terminal of the primary winding side of the second transformer T2. The other end of the first capacitor C1 is connected to the ground GNDin. The 6th terminal of the primary winding side of the first transformer T1 is connected to the drain of the switch MOS tube Q1, the 6th terminal of the primary winding side of the second transformer T2 and the 6th terminal of the primary winding side of the third transformer T3. The multivibrator U1 is connected to the power driver U2. The power driver U2 is connected to the gate of the switch tube Q1. The source of the switch MOS tube Q1 is connected to the ground GNDin. The primary winding side end 1 of the first transformer T1 is connected to the ground GNDin, and the primary winding sides 2 ends of the first transformer T1, the second transformer T2 and the third transformer T3 are connected to the anode of the reset diode D4; the cathode of the reset diode D4 is connected to the primary winding side end 5 of the third transformer T3; the primary winding side end 1 of the second transformer T2 is connected to the ground GNDin; The primary winding side end 1 of the third transformer T3 is connected to the ground GNDin; the secondary winding side end 3 of the first transformer T1 is connected to the anode of the first rectifier D1; the cathode of the first rectifier D1 is connected to one end of the first filter capacitor C6 and the first synchronous buck chip U3; the secondary winding side end 4 of the first transformer T1, the other end of the first filter capacitor C6, the first synchronous buck chip U3, and one end of the second capacitor C12 are connected to the negative end of the first voltage output Vo1; the first synchronous buck chip U3 and the other end of the second capacitor C12 are connected to the positive end of the first voltage output Vo1; The secondary winding side 3 end of the second transformer T2 is connected to the anode of the second rectifier D2; the cathode of the second rectifier D2 is connected to one end of the second filter capacitor C7 and the second synchronous buck chip U4; the secondary winding side 4 end of the second transformer T2, the other end of the second filter capacitor C7, the second synchronous buck chip U4, and one end of the third capacitor C13 are all connected to the negative end of the second voltage output Vo2; The second synchronous buck chip U4 and the other end of the third capacitor C13 are connected to the positive end of the second voltage output Vo2; the secondary winding side 3 end of the third transformer T3 is connected to the anode of the third rectifier D3; The cathode of the third rectifier tube D3 is connected to the third filter capacitor C8 and the third synchronous buck chip U5; The secondary winding side 4 end of the third transformer T3, the other end of the third filter capacitor C8, the third synchronous buck chip U5, and one end of the fourth capacitor C13 are connected to the negative end of the third voltage output Vo3; the third synchronous buck chip U5 and the other end of the fourth capacitor C13 are connected to the positive end of the third voltage output Vo3.

[0022] Synchronous buck chips usually contain two power MOSFETs (metal oxide semiconductor field effect transistors), one as a high-side switch (usually called the upper tube) and the other as a low-side switch (usually called the lower tube). These two MOSFETs are alternately turned on and off under the drive of the control signal to achieve voltage conversion. Working principle: When the high-side switch is turned on, the input voltage charges the inductor and the inductor current increases; when the high-side switch is turned off, the low-side switch is turned on, and the current in the inductor continues to flow through the low-side switch, while providing energy to the load. By adjusting the on-time ratio of the high-side switch and the low-side switch (i.e., the duty cycle), the output voltage can be controlled.

[0023] The present invention adopts a two-stage cascade structure, the first stage realizes multi-channel low-impedance isolated output of the power supply, and the second stage realizes voltage stabilization control of each channel. The first stage realizes multi-channel low-impedance isolated output of the power supply, effectively isolates the electrical connection between the input power supply and each output, and improves the safety and stability of the system. The low-impedance design ensures that the power supply can efficiently and stably provide the required electrical energy to each load, reducing the loss in the energy transmission process. Secondly, the second stage realizes voltage stabilization control of each channel, and through the precise voltage regulation mechanism, the stability and accuracy of the output voltage of each channel are guaranteed. This not only meets the strict voltage requirements of different loads, but also improves the power quality of the entire system, ensuring the normal operation and performance of the load equipment.

[0024] The working process of the high-efficiency, high-precision isolated multi-channel output power supply structure of the present invention is as follows: The square wave circuit with fixed duty cycle output controls the on and off of the switch MOS tube Q1 after passing through the driver U2. When the square wave circuit output is high level, the switch MOS tube Q1 is turned on, and the energy of the first transformer T1, the second transformer T2 and the third transformer T3 is transferred from the primary to the secondary. The secondary induced voltage is rectified by the first rectifier tube D1, the second rectifier tube D2, and the third rectifier tube D3, and filtered by the first filter capacitor C6, the second filter capacitor C7, and the third filter capacitor C8. The first synchronous buck chip U3, the second synchronous buck chip U4, and the third synchronous buck chip U5 provide high-precision output. Output voltage, multiple outputs are independent of each other, and any output voltage is not affected by the loading conditions of other outputs; when the square wave circuit outputs a low level, the switch MOS tube Q1 is turned off, the same-name terminals of the transformers T1, T2, and T3 are low level, the reset diode D4 is turned on, the magnetic core is reset, the first rectifier tube D1, the second rectifier tube D2, and the third rectifier tube D3 of the transformer secondary are rectified and turned off, and the second capacitor C12, the third capacitor C13, and the fourth capacitor C14 at the output terminals of the first synchronous buck chip U3, the second synchronous buck chip U4, and the third synchronous buck chip U5 are discharged to provide a stable output voltage.

[0025] Example 1 like Figure 4 As shown, the circuit adopts a single-ended forward topology structure and a fixed duty cycle drive. When the power switch MOS tube Q1 is turned on, the primary winding energy of the first transformer T1, the second transformer T2 and the third transformer T3 is directly transmitted to the secondary, and is input to the Buck chip after filtering and rectification by the first rectifier tube D1, the second rectifier tube D2 and the third rectifier tube D3, and is secondary stabilized by the first synchronous buck chip U3, the second synchronous buck chip U4 and the third synchronous buck chip U5; when the power switch MOS tube Q1 is turned off, the first rectifier tube D1, the second rectifier tube D2 and the third rectifier tube D3 are turned off, the reset diode D4 is turned on, and the first transformer T1, the second transformer T2 and the third transformer T3 perform magnetic core reset through the third winding.

[0026] When the input voltage varies between 4.5V and 5.5V, the output voltage of the corresponding rectifier tube is shown in Table 1.

[0027] Table 1 Rectifier output voltage under different input voltage and output load

[0028] As shown in Table 1, when the input voltage changes between 4.5V and 5.5V, the output voltage of the rectifier tube changes by about 2V. In order to further optimize the circuit regulation index, a Buck chip is added at the output end. The conversion efficiency of this chip can be as high as 96%, achieving high-efficiency secondary voltage regulation. The circuit performance index is shown in Table 2.

[0029] Table 2 Sample circuit performance indicators

[0030] Furthermore, the present invention has been verified through actual experiments. The circuit parameters used in the experiment are: input voltage 4.5V~5.5V, typical input voltage 5V, three-way output voltage is 5V, maximum output current is 0.5A, switching frequency is 300kHz, voltage and current regulation rate is less than 1%, efficiency can reach 78%, input, output and three-way output are isolated from each other, and the isolation voltage is greater than 500V.

[0031] Example 2 The invention is implemented as follows Figure 4 As shown, the input voltage range of this embodiment is 4.5V to 5.5V, the typical input voltage is 5V, the three output voltages are all 5V, the load current is 0.5A, the maximum output power is 7.5W, the current regulation rate is not greater than 3%, and the input and output, and the three outputs are isolated from each other. The circuit includes a square wave generator, a power driver, a power transformer, an output rectifier filter, and a secondary voltage regulator, which are the same as the circuit structure of the present invention.

[0032] The high-efficiency, high-precision multi-channel output circuit solution proposed above has been put into the design of 5V series DC / DC converters. The circuit is simple and reliable, the number of components is small, the conversion efficiency is high, and it meets the requirements of small circuit size, high efficiency and high density.

[0033] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0034] It should be noted that when a component is referred to as being "fixed to" another component, it may be directly on the other component or there may be a central component. When a component is considered to be "connected to" another component, it may be directly connected to the other component or there may be a central component at the same time. When a component is considered to be "set on" another component, it may be directly set on the other component or there may be a central component at the same time.

[0035] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which the present invention belongs. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0036] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Any ordinary technician in the industry can smoothly implement the present invention as shown in the drawings and described above. However, any equivalent changes, modifications and evolutions made by technicians familiar with the profession without departing from the scope of the technical solution of the present invention using the technical content disclosed above are all equivalent embodiments of the present invention. At the same time, any equivalent changes, modifications and evolutions made to the above embodiments based on the essential technology of the present invention are still within the protection scope of the technical solution of the present invention.

Claims

1. A high-efficiency, high-precision isolated multi-output power supply structure, characterized in that: include, A square wave circuit with a fixed duty cycle output, a switch MOS tube Q1, a reset diode D4, a first transformer T1, a second transformer T2, a third transformer T3 and a three-way output circuit unit; The square wave circuit with fixed duty cycle output is connected to one end of the driver U2, the other end of the driver U2 is connected to the gate of the switch MOS tube Q1, and the drain of the switch MOS tube Q1 is respectively connected to the 6 ends on one side of the primary winding of the first transformer T1, the second transformer T2 and the third transformer T3; The terminals 5 on one side of the primary windings of the first transformer T1 and the second transformer T2 are connected to the input voltage terminal Vin; The secondary winding sides of the first transformer T1, the second transformer T2 and the third transformer T3 are respectively connected to the input end of each output circuit unit; The output end of each output circuit unit is connected to the output voltage end; The 2 ends on both sides of the primary windings of the first transformer T1, the second transformer T2 and the third transformer T3 are connected to the anode of the reset diode D4; the cathode of the reset diode D4 is connected to the 5 end on one side of the primary winding of the third transformer T3, and a synchronous buck chip is provided in the three-way output circuit unit.

2. A high-efficiency, high-precision isolated multi-output power supply structure according to claim 1, characterized in that: The square wave circuit with fixed duty cycle output includes a multivibrator U1, an external resistor and a first capacitor C1; One end of the first capacitor C1 is connected to the input voltage terminal Vin, and the other end of the first capacitor C1 is grounded GNDin; One end of the multivibrator U1 is connected to the input voltage terminal Vin, and the other end of the multivibrator U1 is connected to the driver U2; the multivibrator U1 is connected to an external resistor.

3. The high-efficiency, high-precision isolated multi-output power supply structure according to claim 1, characterized in that: The output circuit unit comprises a first output circuit unit, a second output circuit unit and a third output circuit unit; One end of the first output circuit unit is connected to the secondary winding side of the first transformer T1, and the other end of the first output circuit unit is connected to the first voltage output Vo1 end; One end of the second output circuit unit is connected to the secondary winding side of the second transformer T2, and the other end of the first output circuit unit is connected to the second voltage output Vo2 end; One end of the third output circuit unit is connected to the secondary winding side of the third transformer T3, and the other end of the third output circuit unit is connected to the third voltage output Vo3 end.

4. A high-efficiency, high-precision isolated multi-output power supply structure according to claim 3, characterized in that: The first output circuit unit includes a first rectifier tube D1, a first synchronous buck chip U3, a first filter capacitor C6 and a second capacitor C12; The cathode of the first rectifier tube D1 is connected to one end of the first filter capacitor C6 and the first synchronous buck chip U3; The anode of the first rectifier tube D1 is connected to the 3 end of the secondary winding side of the first transformer T1; the 4 end of the secondary winding side of the first transformer T1 is connected to the other end of the first filter capacitor C6, the first synchronous buck chip U3, one end of the second capacitor C12 and the negative end of the first voltage output Vo1; the other end of the first synchronous buck chip U3 and the second capacitor C12 is connected to the positive end of the first voltage output Vo1.

5. The high-efficiency, high-precision isolated multi-output power supply structure according to claim 3, characterized in that: The second output circuit unit includes a second rectifier tube D2, a second synchronous buck chip U4, a second filter capacitor C7 and a third capacitor C13; The cathode of the second rectifier tube D2 is connected to one end of the second filter capacitor C7 and the second synchronous buck chip U4; The anode of the second rectifier tube D2 is connected to the 3 end of the secondary winding side of the second transformer T2; the 4 end of the secondary winding side of the second transformer T2 is connected to the other end of the second filter capacitor C7, the second synchronous buck chip U4, one end of the third capacitor C13 and the negative end of the second voltage output Vo2; the other end of the second synchronous buck chip U4 and the third capacitor C13 is connected to the positive end of the second voltage output Vo2.

6. The high-efficiency, high-precision isolated multi-output power supply structure according to claim 3, characterized in that: The third output circuit unit includes a third rectifier tube D3, a third synchronous buck chip U5, a third filter capacitor C8 and a fourth capacitor C14; The cathode of the third rectifier tube D3 is connected to one end of the third filter capacitor C8 and the third synchronous buck chip U5; The anode of the third rectifier tube D3 is connected to the 3rd end of the secondary winding side of the third transformer T3; the 4th end of the secondary winding side of the third transformer T3 is connected to the other end of the third filter capacitor C8, the third synchronous buck chip U5, one end of the fourth capacitor C14 and the negative end of the third voltage output Vo3; the other end of the third synchronous buck chip U5 and the fourth capacitor C13 is connected to the positive end of the third voltage output Vo3.

7. The high-efficiency, high-precision isolated multi-output power supply structure according to claim 1, characterized in that: Ends 1 of both sides of the primary windings of the first transformer T1 , the second transformer T2 and the third transformer T3 are grounded.

8. The high-efficiency, high-precision isolated multi-output power supply structure according to claim 1, characterized in that: The multi-channel output power supply structure adopts a two-stage cascade structure, the first stage realizes multi-channel low-impedance isolated output of the power supply, and the second stage realizes voltage stabilization control of each channel.

9. The high-efficiency, high-precision isolated multi-output power supply structure according to claim 1, characterized in that: The multi-channel output power supply structure adopts a single-ended forward topology structure.

10. A working method of a high-efficiency, high-precision isolated multi-output power supply structure, based on the high-efficiency, high-precision isolated multi-output power supply structure according to any one of claims 1 to 9, characterized in that: include, The square wave circuit with fixed duty cycle output is driven by driver U2 to control the on and off of the switch MOS tube Q1; When the square wave circuit with fixed duty cycle output is at a high level, the switch MOS tube Q1 is turned on, and the energy of the first transformer T1, the second transformer T2 and the third transformer T3 is transferred from the primary winding side to the secondary winding side. The induced voltage on the secondary winding side is rectified and filtered by the three-way output circuit unit, and then outputs a high-precision output voltage through the synchronous buck chip; When the square wave circuit with a fixed duty cycle output is at a low level, the control switch MOS tube Q1 is turned off, the same-name terminals of the first transformer T1, the second transformer T2 and the third transformer T3 are at a low level, the reset diode D4 is turned on, the magnetic cores of the first transformer T1, the second transformer T2 and the third transformer T3 are reset, the rectification on the secondary winding side of the first transformer T1, the second transformer T2 and the third transformer T3 is turned off, and the output terminal of the synchronous buck chip of the three-way output circuit unit is discharged to provide a stable output voltage.

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