An output adjustable circuit for switching power supply

Abstract

The invention discloses an output adjustable circuit of a switching power supply, comprising a rectifier circuit, a switching circuit, a filter circuit and a detection comparison circuit; the power input end of the rectifier circuit is connected to a switch transformer of a controlled switching power supply, the output end of the rectifier circuit is connected to the filter circuit, the output end of the filter circuit and the output end of the controlled switching power supply are commonly connected to the input end of the detection comparison circuit, the output end of the detection comparison circuit is connected to the input end of the switching circuit, and the output end of the switching circuit is connected to the switching connection end of the rectifier circuit; the invention switches the series or parallel working mode of the secondary winding rectifier circuit of the switching transformer by detecting the output voltage of the controlled switching power supply, thereby enabling the output voltage of the switching power supply to be adjusted in a wide range, while also working at a better duty cycle, and greatly improving efficiency and reliability.

Description

Technical Field

[0001] The invention relates to the technical field of power electronics, and in particular to a circuit for outputting a switching power supply with a wide adjustable range. Background Art

[0002] With the development of electronic technology and the continuous improvement of people's living standards, people are paying more and more attention to green environmental protection and carbon saving and emission reduction. Therefore, high-tech fields such as photovoltaic power generation, wind power generation, electric vehicles, energy storage, and drones have developed rapidly, and at the same time, this has also put forward more and higher requirements for power electronic switching power supplies. In charging piles, energy storage and other systems, the output voltage of the switching power supply changes continuously with the change of the power of the power battery, which requires the output voltage of the switching power supply to be adjustable over a wide range, and also to have high efficiency and high reliability.

[0003] At present, some switching power supplies in the industry have a narrow output voltage adjustment range, for example: ±10-±20% of the rated voltage, which cannot meet the application of power battery charging and other systems; another part of the switching power supply achieves a wide range of output voltage adjustment by adjusting the working duty cycle over a large range, but this method is at the maximum or minimum duty cycle of the switching power supply when the output voltage is the highest and lowest, which not only reduces the efficiency of the power supply, but also reduces the working reliability. Summary of the invention

[0004] The purpose of the present invention is to provide a circuit for adjusting the output voltage of a switching power supply in a wide range, so as to solve the technical problems existing in the prior art such as narrow adjustable output voltage range, low efficiency and poor reliability of the switching power supply.

[0005] In order to achieve the above object, the present invention provides the following technical solutions:

[0006] A circuit for outputting a switching power supply with a wide adjustable range includes a rectifier circuit, a switching circuit, a filter circuit and a detection and comparison circuit; the power input end of the rectifier circuit is connected to a switch transformer of a controlled switching power supply, the output end of the rectifier circuit is connected to the filter circuit, the output end of the filter circuit and the output end of the controlled switching power supply are commonly connected to the input end of the detection and comparison circuit, the output end of the detection and comparison circuit is connected to the input end of the switching circuit, and the output end of the switching circuit is connected to the switching connection end of the rectifier circuit;

[0007] The detection and comparison circuit is used to detect the output voltage of the controlled switching power supply, and output a control signal to the switching circuit after comparing it with the set reference voltage;

[0008] The switching circuit is used to control the series connection or parallel connection of the rectifier circuit units of the rectifier circuit after isolating and amplifying the control signal sent by the detection and comparison circuit;

[0009] The rectifier circuit is used to rectify and filter the output of the switch transformer of the controlled switch power supply, and at the same time, through the on or off control of the switching circuit, the series or parallel connection of the rectifier circuit units is realized;

[0010] The filter circuit is used to filter the rectified voltage output by the rectifier circuit and then send it to the output end of the controlled switch power supply.

[0011] Compared with the prior art, the technical effects of the present invention are as follows:

[0012] The present invention replaces the secondary of the switch transformer and the output rectifier filter circuit in the controlled switch power supply with a rectifier circuit, a switching circuit, a filter circuit and a detection and comparison circuit, thereby realizing the determination of the working state of the controlled switch power supply according to the level of the output voltage of the controlled switch power supply. When the output voltage is low, the output windings and the rectifier circuit work in parallel, reducing the current stress of each winding and the rectifier circuit, and the switch power supply works at a better duty cycle; when the output voltage is high, the output windings and the rectifier circuit are switched to work in series, which is equivalent to increasing the number of turns of the secondary winding of the transformer and changing the turns ratio of the switch transformer of the switch power supply, so that when the output voltage of the switch power supply is greatly increased, the duty cycle changes very little and still works at a better duty cycle, which enables the output voltage of the switch power supply to be adjusted in a wide range, and at the same time works in a better working state, and the efficiency and reliability are greatly improved.

[0013] The present invention has reliable functions, low cost, flexible and convenient use, is applicable to most switching power supply topologies, can effectively improve the switching power supply output voltage adjustment range, and improve the efficiency and reliability of the switching power supply output voltage at high voltage and low voltage. It is an excellent, simple and practical switching power supply output wide range adjustable circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a structural block diagram of a circuit for outputting a wide range of adjustable switching power supply of the present invention;

[0015] Figure 2 The circuit diagram of the wide-range adjustable output circuit of the switching power supply in Embodiment 1 of the present invention;

[0016] Figure 3 A circuit diagram of a circuit for a switching power supply with a wide adjustable output range in Embodiment 2 of the present invention;

[0017] Figure 4 This is an overall circuit diagram of the switching power supply's output wide-range adjustable circuit in Embodiment 2 of the present invention connected to the controlled switching power supply.

[0018] The present invention is further explained below in conjunction with the accompanying drawings and specific embodiments. DETAILED DESCRIPTION

[0019] like Figure 1 As shown, the output wide-range adjustable circuit of the switching power supply of the present invention comprises a rectifier circuit 1, a switching circuit 2, a filter circuit 3 and a detection and comparison circuit 4; the power input end of the rectifier circuit 1 is connected to the switching transformer of the controlled switching power supply, the output end of the rectifier circuit 1 is connected to the filter circuit 3, the output end of the filter circuit 3 and the output end of the controlled switching power supply are commonly connected to the input end of the detection and comparison circuit 4, the output end of the detection and comparison circuit 4 is connected to the input end of the switching circuit 2, and the output end of the switching circuit 2 is connected to the switching connection end of the rectifier circuit 1.

[0020] The rectifier circuit 1 is composed of two or more rectifier circuit units, the switch circuit 2 is composed of one or more switch circuit units, and the detection and comparison circuit 4 is composed of one or more detection and comparison circuit units.

[0021] The detection and comparison circuit 4 is used to detect the output voltage of the controlled switching power supply, and output a control signal to the switching circuit 2 after comparing it with the set reference voltage;

[0022] The switching circuit 2 is used to isolate and amplify the control signal sent by the detection and comparison circuit 4 to control the opening or closing of the internal power switch, and to control the series connection or parallel connection of the rectifier circuit units of the rectifier circuit 1 according to the opening and closing of the power switch;

[0023] The rectifier circuit 1 is used to rectify and filter the output of the switch transformer of the controlled switch power supply, and at the same time, through the opening or closing of the switching circuit 2, the series or parallel connection of the rectifier circuit units is realized;

[0024] The filter circuit 3 is used to filter the rectified voltage output by the rectifier circuit 1 and then send it to the output end of the controlled switching power supply;

[0025] When the output voltage of the controlled switching power supply is low, all the rectifying circuit units of the rectifying circuit 1 are connected in parallel, and when the output voltage of the controlled switching power supply is high, all the rectifying circuit units of the rectifying circuit 1 are connected in series; this is equivalent to adjusting the number of turns of the secondary winding of the switching transformer according to the output voltage of the controlled switching power supply, that is, changing the turns ratio of the switching transformer of the controlled switching power supply, so that the output voltage of the controlled switching power supply can be adjusted in a wide range, and at the same time, it works at a better working duty cycle, thereby improving efficiency and reliability.

[0026] Embodiment 1:

[0027] The first preferred embodiment of the present invention can be found in Figure 2As shown, in the output wide-range adjustable circuit of the switching power supply provided in this embodiment, the rectifier circuit 1 includes a first rectifier circuit unit 11, a second rectifier circuit unit 12 and a third rectifier circuit unit 13; the first rectifier circuit unit 11 includes a switching transformer secondary winding NS101, diodes D101-D103 and a capacitor C101; the second rectifier circuit unit 12 includes a switching transformer secondary winding NS102, diodes D201-D203 and a capacitor C201; the third rectifier circuit unit 13 includes a switching transformer secondary winding NS301, diodes D301-D303 and a capacitor C301;

[0028] The switching circuit 2 includes a first switching circuit unit 21 and a second switching circuit unit 22; the first switching circuit unit 21 includes a MOS transistor Q401, resistors R401-R402 and a photocoupler U401; the second switching circuit unit 22 includes a MOS transistor Q501, a resistor R501, a resistor R502 and a photocoupler U501;

[0029] The detection comparison circuit 4 includes a first detection comparison circuit unit 41 and a second detection comparison circuit unit 42; the first detection comparison circuit unit 41 includes resistors R601-R605, capacitors C601-C602 and an operational amplifier U601; the second detection comparison circuit unit 42 includes resistors R701-R705, an operational amplifier U701, capacitors C701 and capacitor C702;

[0030] The filter circuit 3 includes L801 and capacitor C801.

[0031] The specific form is:

[0032] The input end of the rectifier circuit 1 is connected to the switch transformer of the controlled switch power supply, and the output end of the filter circuit 3 is connected to the output end of the controlled switch power supply;

[0033] One end of the secondary winding NS101 of the switching transformer is connected to the anode of the diode D101; the other end of the secondary winding NS101 of the switching transformer is connected to the cathode of the diode D103, one end of the capacitor C101, and the drain of the MOS tube Q401; the cathode of the diode D101 is connected to the other end of the capacitor C101 and the anode of the diode D102; the anode of the diode D103 is grounded; the cathode of the diode D102 is connected to the cathode of the diode D202, the cathode of the diode D302, and one end of the inductor L801;

[0034] One end of the secondary winding NS201 of the switching transformer is connected to the anode of the diode D201; the other end of the secondary winding NS201 of the switching transformer is connected to the cathode of the diode D203, one end of the capacitor C201, and the drain of the MOS tube Q501; the cathode of the diode D201 is connected to the other end of the capacitor C201, the anode of the diode D202, the source of the MOS tube Q401, and the emitter of the photocoupler U401; the anode of the diode D203 is grounded;

[0035] One end of the secondary winding NS301 of the switching transformer is connected to the anode of the diode D301; the other end of the secondary winding NS301 of the switching transformer is connected to the cathode of the diode D303 and one end of the capacitor C301; the cathode of the diode D301 is connected to the other end of the capacitor C301, the anode of the diode D302, the source of the MOS tube Q501, and the emitter of the photocoupler U501; the anode of the diode D303 is grounded;

[0036] The gate of MOS tube Q401 is connected to one end of resistor R401 and collector of photocoupler U401; the other end of resistor R401 is connected to auxiliary power supply Vcc2; the anode of photocoupler U401 is connected to one end of resistor R402 and one end of resistor R601; the cathode of photocoupler U401 is grounded; the other end of resistor R402 is grounded;

[0037] The gate of MOS tube Q501 is connected to one end of resistor R501 and the collector of photocoupler U501; the other end of resistor R501 is connected to auxiliary power supply Vcc1; the anode of photocoupler U501 is connected to one end of resistor R502 and one end of resistor R701; the cathode of photocoupler U501 is grounded; the other end of resistor R502 is grounded;

[0038] The other end of the resistor R601 is connected to the output terminal 4 of the operational amplifier U601; the power supply terminal 6 of the operational amplifier U601 is commonly connected to one end of the capacitor C601, one end of the resistor R602, and the reference voltage Vref; the non-inverting input terminal 1 of the operational amplifier U601 is commonly connected to the other end of the resistor R602 and one end of the resistor R604; the inverting input terminal 3 of the operational amplifier U601 is commonly connected to one end of the resistor R603, one end of the resistor R605, and one end of the capacitor C602; the ground terminal 2 of the operational amplifier U601 is grounded; the other end of the capacitor C601 is grounded; the other end of the resistor R603 is connected to the output terminal Vout of the switching power supply; the other end of the resistor R604 is grounded; the other end of the resistor R605 is grounded; the other end of the capacitor C602 is grounded;

[0039] The other end of the resistor R701 is connected to the output terminal 4 of the operational amplifier U701; the power supply terminal 6 of the operational amplifier U701 is commonly connected to one end of the capacitor C701, one end of the resistor R702, and the reference voltage Vref; the non-inverting input terminal 1 of the operational amplifier U701 is commonly connected to the other end of the resistor R702 and one end of the resistor R704; the inverting input terminal 3 of the operational amplifier U701 is commonly connected to one end of the resistor R703, one end of the resistor R705, and one end of the capacitor C702; the ground terminal 2 of the operational amplifier U701 is grounded; the other end of the capacitor C701 is grounded; the other end of the resistor R703 is connected to the output terminal Vout of the switching power supply; the other end of the resistor R704 is grounded; the other end of the resistor R705 is grounded; the other end of the capacitor C702 is grounded;

[0040] The other end of the inductor L801 is connected to one end of the capacitor C801 and the output end Vout of the switching power supply; the other end of the capacitor C801 is grounded.

[0041] The detailed working process of this embodiment is as follows: the output voltage Vout of the controlled switching power supply is sent to the inverting input terminal 3 pin of the operational amplifier U601 after voltage division and filtering by resistors R603, R605 and C602, and is compared with the first preset voltage (for example: 0.25V) set by the reference power supply Vref, resistors R602 and R604 at the inverting input terminal 1 pin of the operational amplifier U601. When the voltage at the inverting input terminal 3 pin of the operational amplifier U601 is lower than the first preset voltage 1, the output terminal 4 pin of the operational amplifier U601 outputs a high level, and after voltage division by resistors R602, R604 and C603, the output voltage Vout of the controlled switching power supply is sent to the inverting input terminal 3 pin of the operational amplifier U601. The light emitting diode and the phototransistor in the photocoupler U401 are turned on. After the photocoupler U401 is turned on, the turn-on voltage provided by the auxiliary power supply Vcc2 to the gate of the MOS tube Q401 through the resistor R401 is short-circuited, so that the drain and source of the MOS tube Q401 are turned off. After the drain and source of the MOS tube Q401 are turned off, the first rectifier circuit unit 11 composed of the secondary winding NS101 of the switching transformer, the diodes D101-D103, and the capacitor C101 and the second rectifier circuit unit 11 composed of the secondary winding NS102 of the switching transformer, the diodes D201-D203, and the capacitor C201 are turned on. The elements 12 form a parallel connection to work, and the rectified voltage after parallel connection is filtered by the filter circuit 3 composed of the inductor L801 and the capacitor C801 and then sent to the output end of the controlled switch power supply to form the output voltage Vout; when the voltage of the 3rd pin of the inverting input end of the operational amplifier U601 is higher than the first preset voltage 1, the 4th pin of the output end of the operational amplifier U601 outputs a low level, and after the voltage is divided by the resistors R602 and R402, the light-emitting diode and the phototransistor in the photocoupler U401 are not turned on. Since the photocoupler U401 is not turned on, the auxiliary power supply Vcc2 is normally supplied to the MOS tube Q401 through the resistor R401. The gate provides a turn-on voltage, and the drain-source of the MOS tube Q401 is turned on. After the drain-source of the MOS tube Q401 is turned on, the first rectifier circuit unit 11 composed of the secondary winding NS101 of the switching transformer, the diodes D101-D103, and the capacitor C101 and the second rectifier circuit unit 12 composed of the secondary winding NS201 of the switching transformer, the diodes D201-D203, and the capacitor C201 form a series connection to work. The rectified voltage after the series connection is filtered by the filter circuit 3 composed of the inductor L801 and the capacitor C801 and sent to the output end of the controlled switching power supply to form the output voltage Vout;

[0042] At the same time, the output voltage Vout of the controlled switching power supply is also sent to the inverting input terminal 3 of the operational amplifier U701 after voltage division and filtering by resistors R703, R705, and C702, and is compared with the second preset voltage (for example: 0.5V) set by the reference power supply Vref, resistors R702, and resistors R704 at the non-inverting input terminal 1 of the operational amplifier U701. When the voltage at the inverting input terminal 3 of the operational amplifier U701 is lower than the second preset voltage, the output terminal 4 of the operational amplifier U701 outputs a high level, and after voltage division by resistors R702 and R702, the photoelectric coupler The light emitting diode and the phototransistor in U501 are turned on. After the photocoupler U501 is turned on, the turn-on voltage provided by the auxiliary power supply Vcc1 to the gate of the MOS tube Q501 through the resistor R501 is short-circuited, causing the drain and source of the MOS tube Q501 to be turned off. After the drain and source of the MOS tube Q501 are turned off, the second rectifier circuit unit 12 composed of the secondary winding NS201 of the switching transformer, diodes D201~D203, and capacitor C201 and the third rectifier circuit unit 1 composed of the secondary winding NS301 of the switching transformer, diodes D301~D303, and capacitor C301 are turned on. 3 forms a parallel connection to work, and the parallel rectified voltage is filtered by the filter circuit composed of inductor L801 and capacitor C801 and sent to the output end of the switching power supply to form the output voltage Vout; when the voltage of the 3rd pin of the inverting input end of the operational amplifier U701 is higher than the second preset voltage, the 4th pin of the output end of the operational amplifier U701 outputs a low level, and after the voltage is divided by resistors R702 and R702, the light-emitting diode and the phototransistor in the photocoupler U501 are turned off. Since the photocoupler U501 is not turned on, the auxiliary power supply Vcc1 is normally connected to the gate of the MOS tube Q501 through the resistor R501. The electrode provides a turn-on voltage, and the drain-source electrode of the MOS tube Q501 is turned on. After the drain-source electrode of the MOS tube Q501 is turned on, the second rectifier circuit unit 12 composed of the secondary winding NS201 of the switching transformer, the diodes D201-D203, and the capacitor C201 and the second rectifier circuit unit 13 composed of the secondary winding NS301 of the switching transformer, the diodes D301-D303, and the capacitor C301 form a series connection to work. The rectified voltage after the series connection is filtered by the filter circuit composed of the inductor L801 and the capacitor C801 and sent to the output end of the switching power supply to form the output voltage Vout;

[0043] Since the rectifier circuit unit can be made to work in series or parallel according to the level of the output voltage of the controlled switching power supply, it is equivalent to adjusting the number of turns of the secondary winding of the switching transformer according to the level of the output voltage of the controlled switching power supply, that is, changing the turns ratio of the switching transformer of the controlled switching power supply, so that the output voltage of the controlled switching power supply can be adjusted over a wide range, and at the same time, it can work at a better duty cycle, thereby improving efficiency and reliability.

[0044] Embodiment 2:

[0045] For the second preferred embodiment of the present invention, please refer to Figure 3 As shown, the control principle is roughly the same as that of the first preferred embodiment, with two main differences: (1) The rectifier circuit 1 is composed of two rectifier circuit units, and the switching circuit 2, the filter circuit 3 and the detection and comparison circuit 4 are respectively composed of a switching circuit unit, a filter circuit unit and a detection and comparison circuit; while in Example 1, the rectifier circuit 1 is composed of three rectifier circuit units, and the switching circuit 2, the filter circuit 3 and the detection and comparison circuit 4 are respectively composed of two switching circuit units, two filter circuit units and two detection and comparison circuits; (2) The rectification method of the secondary of the transformer in the rectifier circuit unit is a typical usage of the forward-excitation in the switching power supply, while the rectification method of the secondary of the transformer in the rectifier circuit unit in Example 1 is a typical usage of the flyback in the switching power supply. The specific form is:

[0046] The rectifier circuit 1 includes a rectifier circuit unit 1a and a rectifier circuit unit 1b; the rectifier circuit unit 1a includes a switching transformer secondary winding NS101, diodes D101-D104, a capacitor C101 and an inductor L101; the rectifier circuit unit 1b includes a switching transformer secondary winding NS102, diodes D201-D204, a capacitor C201 and an inductor L201; the switching circuit 2 includes a MOS tube Q401, a resistor R401, a resistor R402 and a photocoupler U401; the detection and comparison circuit 4 includes resistors R601-R605, an operational amplifier U601, a capacitor C601 and a capacitor C602; the filter circuit 3 includes L801 and a capacitor C801.

[0047] The rectifier circuit 1 is connected to the switch transformer of the controlled switch power supply, and the filter circuit 3 is connected to the output end of the controlled switch power supply;

[0048] One end of the secondary winding NS101 of the switching transformer is connected to the anode of the diode D101; the other end of the secondary winding NS101 of the switching transformer is connected to the cathode of the diode D103, the anode of the diode D104, one end of the capacitor C101, and the drain of the MOS tube Q401; the cathode of the diode D101 is connected to one end of the inductor L101 and the cathode of the diode D104; the other end of the inductor L101 is connected to the other end of the capacitor C101 and the anode of the diode D102; the anode of the diode D103 is grounded; the cathode of the diode D102 is connected to the cathode of the diode D202 and one end of the inductor L801;

[0049] One end of the secondary winding NS201 of the switching transformer is connected to the anode of the diode D201; the other end of the secondary winding NS201 of the switching transformer is connected to the cathode of the diode D203, the anode of the diode D204, and one end of the capacitor C201; the cathode of the diode D201 is connected to one end of the inductor L201 and the cathode of the diode D204; the other end of the inductor L201 is connected to the emitter of the photocoupler U401, the source of the MOS tube Q401, the other end of the capacitor C201, and the anode of the diode D202; the anode of the diode D203 is grounded;

[0050] The gate of MOS tube Q401 is connected to one end of resistor R401 and collector of photocoupler U401; the other end of resistor R401 is connected to auxiliary power supply Vcc1; the anode of photocoupler U401 is connected to one end of resistor R402 and one end of resistor R601; the cathode of photocoupler U401 is grounded; the other end of resistor R402 is grounded;

[0051] The other end of the resistor R601 is connected to the output terminal 4 of the operational amplifier U601; the power supply terminal 6 of the operational amplifier U601 is connected to one end of the capacitor C601, one end of the resistor R602, and the reference voltage Vref; the non-inverting input terminal 1 of the operational amplifier U601 is connected to the other end of the resistor R602 and one end of the resistor R604; the inverting input terminal 3 of the operational amplifier U601 is connected to one end of the resistor R603, one end of the resistor R605, and one end of the capacitor C602; the ground terminal 2 of the operational amplifier U601 is grounded; the other end of the capacitor C601 is grounded; the other end of the resistor R603 is connected to the output terminal Vout of the switching power supply; the other end of the resistor R604 is grounded; the other end of the resistor R605 is grounded; the other end of the capacitor C602 is grounded;

[0052] The other end of the inductor L801 is connected to one end of the capacitor C801 and the output end Vout of the switching power supply; the other end of the capacitor C801 is grounded.

[0053] The overall circuit diagram of this embodiment connected to the controlled switching power supply is as follows Figure 4 As shown, the output wide-range adjustable circuit of the switching power supply of the present invention (including a rectifier circuit 1, a switching circuit 2, a filter circuit 3 and a detection and comparison circuit 4) replaces the conventional switching transformer secondary and output rectifier and filter circuit in the controlled switching power supply, the rectifier circuit 1 is connected to the switching transformer of the controlled switching power supply, and the filter circuit 3 is connected to the output end of the controlled switching power supply.

[0054] The above description is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be conceived by a technician familiar with the field within the technical scope disclosed by the present invention without creative work are all covered by the protection scope of the present invention.

Claims

1. An output adjustable circuit of a switching power supply, characterized in that: The invention comprises a rectifier circuit (1), a switching circuit (2), a filter circuit (3) and a detection comparison circuit (4); the power input end of the rectifier circuit (1) is connected to the switch transformer of the controlled switch power supply, the output end of the rectifier circuit (1) is connected to the filter circuit (3), the output end of the filter circuit (3) and the output end of the controlled switch power supply are connected to the input end of the detection comparison circuit (4), the output end of the detection comparison circuit (4) is connected to the input end of the switching circuit (2), and the output end of the switching circuit (2) is connected to the switch connection end of the rectifier circuit (1); The detection and comparison circuit (4) is used to detect the output voltage of the controlled switch power supply, and output a control signal to the switching circuit (2) after comparing it with a set reference voltage; The switching circuit (2) is used to isolate and amplify the control signal sent by the detection and comparison circuit (4), and then control the series connection or parallel connection of the rectifier circuit units of the rectifier circuit (1); The rectifier circuit (1) is used to rectify and filter the output of the switch transformer of the controlled switch power supply, and at the same time, through the on or off control of the switching circuit (2), the series or parallel connection of the rectifier circuit units is realized; The filter circuit (3) is used to filter the rectified voltage output by the rectifier circuit (1) and then send it to the output end of the controlled switch power supply; The rectifier circuit (1) comprises a first rectifier circuit unit (11), a second rectifier circuit unit (12) and a third rectifier circuit unit (13); the first rectifier circuit unit (11) comprises a switching transformer secondary winding NS101, diodes D101-D103 and a capacitor C101; the second rectifier circuit unit (12) comprises a switching transformer secondary winding NS201, diodes D201-D203 and a capacitor C201; the third rectifier circuit unit (13) comprises a switching transformer secondary winding NS301, diodes D301-D303 and a capacitor C301; The switching circuit (2) comprises a first switching circuit unit (21) and a second switching circuit unit (22); the first switching circuit unit (21) comprises a MOS tube Q401, resistors R401-R402 and a photoelectric coupler U401; the second switching circuit unit (22) comprises a MOS tube Q501, a resistor R501, a resistor R502 and a photoelectric coupler U501; The detection comparison circuit (4) comprises a first detection comparison circuit unit (41) and a second detection comparison circuit unit (42); the first detection comparison circuit unit (41) comprises resistors R601-R605, capacitors C601-C602 and an operational amplifier U601; the second detection comparison circuit unit (42) comprises resistors R701-R705, an operational amplifier U701, a capacitor C701 and a capacitor C702; The filter circuit (3) comprises L801 and capacitor C801; One end of the secondary winding NS101 of the switching transformer is connected to the anode of the diode D101; the other end of the secondary winding NS101 of the switching transformer is connected to the cathode of the diode D103, one end of the capacitor C101, and the drain of the MOS tube Q401; the cathode of the diode D101 is connected to the other end of the capacitor C101 and the anode of the diode D102; the anode of the diode D103 is grounded; the cathode of the diode D102 is connected to the cathode of the diode D202, the cathode of the diode D302, and one end of the inductor L801; One end of the secondary winding NS201 of the switching transformer is connected to the anode of the diode D201; the other end of the secondary winding NS201 of the switching transformer is connected to the cathode of the diode D203, one end of the capacitor C201, and the drain of the MOS tube Q501; the cathode of the diode D201 is connected to the other end of the capacitor C201, the anode of the diode D202, the source of the MOS tube Q401, and the emitter of the photocoupler U401; the anode of the diode D203 is grounded; One end of the secondary winding NS301 of the switching transformer is connected to the anode of the diode D301; The other end of the secondary winding NS301 of the switching transformer is connected to the cathode of the diode D303 and one end of the capacitor C301; the cathode of the diode D301 is connected to the other end of the capacitor C301, the anode of the diode D302, the source of the MOS tube Q501, and the emitter of the photoelectric coupler U501; The anode of diode D303 is grounded; The gate of the MOS tube Q401 is connected to one end of the resistor R401 and the collector of the photocoupler U401; the other end of the resistor R401 is connected to the auxiliary power supply Vcc2; the anode of the photocoupler U401 is connected to one end of the resistor R402 and one end of the resistor R601; the cathode of the photocoupler U401 is grounded; the other end of the resistor R402 is grounded; The gate of the MOS tube Q501 is connected to one end of the resistor R501 and the collector of the photocoupler U501; the other end of the resistor R501 is connected to the auxiliary power supply Vcc1; the anode of the photocoupler U501 is connected to one end of the resistor R502 and one end of the resistor R701; the cathode of the photocoupler U501 is grounded; the other end of the resistor R502 is grounded; The other end of the resistor R601 is connected to the output terminal 4 of the operational amplifier U601; the power supply terminal 6 of the operational amplifier U601 is connected to one end of the capacitor C601, one end of the resistor R602, and the reference voltage Vref; the non-inverting input terminal 1 of the operational amplifier U601 is connected to the other end of the resistor R602 and one end of the resistor R604; the inverting input terminal 3 of the operational amplifier U601 is connected to one end of the resistor R603, one end of the resistor R605, and one end of the capacitor C602; the ground terminal 2 of the operational amplifier U601 is grounded; The other end of capacitor C601 is grounded; the other end of resistor R603 is connected to the output terminal Vout of the switching power supply; the other end of resistor R604 is grounded; the other end of resistor R605 is grounded; the other end of capacitor C602 is grounded; The other end of the resistor R701 is connected to the output terminal 4 of the operational amplifier U701; the power supply terminal 6 of the operational amplifier U701 is commonly connected to one end of the capacitor C701, one end of the resistor R702, and the reference voltage Vref; the non-inverting input terminal 1 of the operational amplifier U701 is commonly connected to the other end of the resistor R702 and one end of the resistor R704; the inverting input terminal 3 of the operational amplifier U701 is commonly connected to one end of the resistor R703, one end of the resistor R705, and one end of the capacitor C702; the ground terminal 2 of the operational amplifier U701 is grounded; the other end of the capacitor C701 is grounded; the other end of the resistor R703 is connected to the output terminal Vout of the switching power supply; the other end of the resistor R704 is grounded; the other end of the resistor R705 is grounded; the other end of the capacitor C702 is grounded; The other end of the inductor L801 is connected to one end of the capacitor C801 and the output end Vout of the switching power supply; the other end of the capacitor C801 is grounded.

2. An output adjustable circuit of a switching power supply, characterized in that: The invention comprises a rectifier circuit (1), a switching circuit (2), a filter circuit (3) and a detection comparison circuit (4); the power input end of the rectifier circuit (1) is connected to the switch transformer of the controlled switch power supply, the output end of the rectifier circuit (1) is connected to the filter circuit (3), the output end of the filter circuit (3) and the output end of the controlled switch power supply are connected to the input end of the detection comparison circuit (4), the output end of the detection comparison circuit (4) is connected to the input end of the switching circuit (2), and the output end of the switching circuit (2) is connected to the switch connection end of the rectifier circuit (1); The detection and comparison circuit (4) is used to detect the output voltage of the controlled switch power supply, and output a control signal to the switching circuit (2) after comparing it with a set reference voltage; The switching circuit (2) is used to isolate and amplify the control signal sent by the detection and comparison circuit (4), and then control the series connection or parallel connection of the rectifier circuit units of the rectifier circuit (1); The rectifier circuit (1) is used to rectify and filter the output of the switch transformer of the controlled switch power supply, and at the same time, through the on or off control of the switching circuit (2), the series or parallel connection of the rectifier circuit units is realized; The filter circuit (3) is used to filter the rectified voltage output by the rectifier circuit (1) and then send it to the output end of the controlled switch power supply; The rectifier circuit (1) comprises a rectifier circuit unit 1a and a rectifier circuit unit 1b; the rectifier circuit unit 1a comprises a switching transformer secondary winding NS101, diodes D101-D104, a capacitor C101 and an inductor L101; the rectifier circuit unit 1b comprises a switching transformer secondary winding NS201, diodes D201-D204, a capacitor C201 and an inductor L201; the switching circuit (2) comprises a MOS tube Q401, a resistor R401, a resistor R402 and a photocoupler U401; the detection and comparison circuit (4) comprises resistors R601-R605, an operational amplifier U601, a capacitor C601 and a capacitor C602; the filter circuit (3) comprises L801 and a capacitor C801; One end of the secondary winding NS101 of the switching transformer is connected to the anode of the diode D101; the other end of the secondary winding NS101 of the switching transformer is connected to the cathode of the diode D103, the anode of the diode D104, one end of the capacitor C101, and the drain of the MOS tube Q401; the cathode of the diode D101 is connected to one end of the inductor L101 and the cathode of the diode D104; the other end of the inductor L101 is connected to the other end of the capacitor C101 and the anode of the diode D102; the anode of the diode D103 is grounded; the cathode of the diode D102 is connected to the cathode of the diode D202 and one end of the inductor L801; One end of the secondary winding NS201 of the switching transformer is connected to the anode of the diode D201; the other end of the secondary winding NS201 of the switching transformer is connected to the cathode of the diode D203, the anode of the diode D204, and one end of the capacitor C201; the cathode of the diode D201 is connected to one end of the inductor L201 and the cathode of the diode D204; the other end of the inductor L201 is connected to the emitter of the photoelectric coupler U401, the source of the MOS tube Q401, the other end of the capacitor C201, and the anode of the diode D202; the anode of the diode D203 is grounded; The gate of the MOS tube Q401 is connected to one end of the resistor R401 and the collector of the photocoupler U401; the other end of the resistor R401 is connected to the auxiliary power supply Vcc1; the anode of the photocoupler U401 is connected to one end of the resistor R402 and one end of the resistor R601; the cathode of the photocoupler U401 is grounded; the other end of the resistor R402 is grounded; The other end of the resistor R601 is connected to the output terminal 4 of the operational amplifier U601; the power supply terminal 6 of the operational amplifier U601 is connected to one end of the capacitor C601, one end of the resistor R602, and the reference voltage Vref; the non-inverting input terminal 1 of the operational amplifier U601 is connected to the other end of the resistor R602 and one end of the resistor R604; the inverting input terminal 3 of the operational amplifier U601 is connected to one end of the resistor R603, one end of the resistor R605, and one end of the capacitor C602; the ground terminal 2 of the operational amplifier U601 is grounded; The other end of capacitor C601 is grounded; the other end of resistor R603 is connected to the output terminal Vout of the switching power supply; The other end of the resistor R604 is grounded; the other end of the resistor R605 is grounded; the other end of the capacitor C602 is grounded; The other end of the inductor L801 is connected to one end of the capacitor C801 and the output end Vout of the switching power supply; the other end of the capacitor C801 is grounded.

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