CN218335756U

CN218335756U - Output voltage adjustable power supply with wide working range

Info

Publication number: CN218335756U
Application number: CN202222639930.4U
Authority: CN
Inventors: 王坤; 毛鹏; 王艳杰; 赵君; 许鑫
Original assignee: Nanjing University of Information Science and Technology
Current assignee: Nanjing University of Information Science and Technology
Priority date: 2022-09-30
Filing date: 2022-09-30
Publication date: 2023-01-17
Anticipated expiration: 2032-09-30

Abstract

The utility model discloses a wide working range output voltage adjustable power supply provides one kind and adjusts output voltage through the method that changes the secondary winding number of turns of transformer and does not change the duty cycle, owe overvoltage protection circuit, DCDC Flyback power circuit, output voltage control loop, output excessive pressure overcurrent protection circuit including auxiliary power supply circuit, input. The auxiliary power supply circuit provides required power supply voltage for the input under-overvoltage protection circuit, the DC/DC Flyback power circuit, the output voltage control loop and the output overvoltage and overcurrent protection circuit; the input under-voltage and over-voltage protection circuit is used for protecting the direct-current input voltage within a preset voltage range; the DC/DC Flyback power circuit is used for changing a direct current input voltage into 3 different output voltages; the output overvoltage and overcurrent protection circuit monitors and protects the current and voltage supplied to the load. Through the technical scheme of the utility model, the power not only can be under the condition that does not change the duty cycle a plurality of voltages of output, and power supply range is wider, and the power has output excessive pressure moreover, overcurrent protection function, has higher security.

Description

Output voltage adjustable power supply with wide working range

Technical Field

The utility model belongs to the technical field of switching power supply, concretely relates to wide working range output voltage adjustable power.

Background

The power supply is an important component in electric equipment, and particularly in the research and development of medical instruments and electronic equipment, and test power supplies in various industries such as laboratories and the like, the power supply not only has the characteristics of high efficiency, small volume, high power and the like, but also has good dynamic performance and the capability of providing wide-range adjustability of output voltage. Under the requirement, the switching power supply gradually replaces the traditional linear power supply with the advantages of small volume, light weight, high efficiency and the like, the current power supply with the adjustable output voltage wide range is basically realized by adopting the switching power supply, and the key problem of realizing the adjustment of the output voltage wide range by using the switching power supply is that the duty ratio change range of the converter is very large and possibly exceeds the range which can be borne by the converter, so that the system cannot be realized. Various solutions have been proposed to solve this problem, but still have more or less drawbacks. These schemes can be divided into two broad categories: a variable frequency type and a variable structure type. The variable frequency type can increase the adjustment range by lowering the switching frequency at a low voltage, but the change of the circuit frequency inevitably makes the design of the magnetic element difficult to optimize. The variable structure type mainly comprises two-stage regulation, series-parallel connection topological structures and the like, although the duty ratio regulation range of the variable structure type can be very wide and the regulation precision is high, most circuit structures are complex, and the control mode is complex. This power scheme has designed a structure of becoming simple with control mode's wide output voltage adjustable power of structural type, and it produces different output voltage mainly through changing the secondary winding number of turns, and this has not only guaranteed output voltage can wider, more accurate regulation, still makes the operation and the design of power simpler and more safe.

Disclosure of Invention

The invention aims to: the utility model provides an adjust output voltage through the method that changes the secondary winding number of turns of transformer and not change the duty cycle, this circuit has the output voltage scope of broad, and electric property is stable, and has more extensive application scene. In addition, the power supply has the functions of output overvoltage and overcurrent protection, and has higher safety.

In order to achieve the purpose, the invention provides the following technical scheme: a wide-working-range output voltage adjustable power supply comprises an auxiliary power supply circuit, an input under-overvoltage protection circuit, a DC/DC Flyback power circuit, an output voltage control loop and an output overvoltage and overcurrent protection circuit; the auxiliary power supply circuit gets electricity from the positive electrode and the negative electrode of the direct-current input power supply, the output end of the auxiliary power supply circuit is respectively connected with the input under-overvoltage protection circuit, the DC/DC Flyback power circuit, the output voltage control loop and the output overvoltage overcurrent protection circuit, and the auxiliary power supply circuit respectively provides power supply voltage required by work for the circuits connected with the auxiliary power supply circuit; the input under-overvoltage protection circuit has an input end connected with a direct-current input voltage VDC +, and an output end connected with the positive electrode input end of the DC/DC Flyback power circuit, and is used for protecting the direct-current input voltage within a preset voltage range; the negative electrode input end of the DC/DC Flyback power circuit is connected with a direct-current input voltage VDC-, the positive electrode output end of the DC/DC Flyback power circuit is connected with the input end of an output voltage control loop and used for transmitting voltage signals, the positive electrode output end of the DC/DC Flyback power circuit is connected with the voltage input end and the current input end of an output overvoltage and overcurrent protection circuit and used for transmitting voltage signals and current signals, and the negative electrode output end of the DC/DC Flyback power circuit is connected with the negative electrode input end of a load; the output end of the output voltage control loop is connected with the DC/DC Flyback power circuit, and a signal with variable output voltage is transmitted to the control end of the DC/DC Flyback power circuit so as to control the triggering of the DC/DC Flyback power circuit, thereby forming feedback loops with different output voltages; the DC/DC Flyback power circuit is used for changing a direct current input voltage into 3 different output voltages so as to meet different power supply requirements of loads; the output end of the output overvoltage and overcurrent protection circuit is connected with the anode input end of the load, and the output overvoltage and overcurrent protection circuit monitors and protects the current and the voltage supplied to the load.

Further, the auxiliary power circuit includes a first transformer, an MOS transistor Q1, a capacitor C2, a capacitor C3, a capacitor C4, a capacitor C5, a resistor R1, a diode D1, a three-terminal regulator, and a first control chip, wherein an anode of a primary winding W1 of the first transformer is connected to an anode of a dc input power supply, a cathode of the primary winding W1 of the first transformer is connected to a cathode of the MOS transistor Q1, an S-pole of the MOS transistor Q1 is connected to a cathode of the dc input power supply, and an anode of a secondary winding W2 of the first transformer is grounded to GNDs together with one end of the capacitor C2, one end of the capacitor C3, one end of the capacitor C4, one end of the capacitor C5, and a GND terminal of the three-terminal regulator; diode D1 positive pole is connected respectively to the secondary winding W2 negative pole of first transformer, electric capacity C1 one end, electric capacity C1 other end connecting resistance R1 one end, diode D1 negative pole is connected respectively to the resistance R1 other end, the electric capacity C2 other end, the electric capacity C3 other end, a control chip input, three terminal regulator's VIN end, auxiliary power supply circuit 15V output, MOS pipe Q1's the G utmost point is connected to a control chip output, the electric capacity C4 other end is connected respectively to three terminal regulator's OUT end, the electric capacity C5 other end, the auxiliary power supply circuit 5V output.

Further, the input under-overvoltage protection circuit includes a resistor R2, a resistor R3, a resistor R4, a resistor R5, a resistor R6, a resistor R7, a resistor R8, a resistor R9, a resistor R10, a resistor R11, a resistor R12, a resistor R13, a resistor R14, a capacitor C6, a capacitor C7, a diode D2, a diode D3, a diode D4, a MOS transistor Q2, a comparator U1A, a comparator U1B, an OR gate OR1, a BUZZER1, and a relay RY1, an input end of the input under-overvoltage protection circuit is respectively connected to one end of the resistor R3 and one end of the resistor R4, the other end of the resistor R3 is respectively connected to one end of the resistor R2, one end of the capacitor C6, and one end of the resistor R6, the other end of the resistor R6 is respectively connected to one end of the resistor R10 and a negative input end of the comparator U1A, and the other end of the resistor R2, the capacitor C6 and the other end of the resistor R10 are commonly grounded GNDP; the other end of the resistor R4 is connected with one end of a resistor R5, one end of a capacitor C7 and one end of a resistor R9 respectively, the other end of the resistor R9 is connected with one end of a resistor R13 and the positive input end of the comparator U1B respectively, and the other end of the resistor R5, the other end of the capacitor C7 and the other end of the resistor R13 are grounded GNDP together; the positive input end of the comparator U1A is respectively connected with one end of a resistor R11 and one end of a resistor R7, the other end of the resistor R11 is connected with one end of a resistor R12, the other end of the resistor R7 and one end of a resistor R8 are commonly grounded GNDP, and the other end of the resistor R8 and the other end of the resistor R12 are commonly connected with the negative input end of the comparator U1B; the power supply end of the comparator U1A and the power supply end of the comparator U1B are both connected with the 15V output end of the auxiliary power circuit, the ground ends of the comparator U1A and the comparator U1B are both grounded GNDP, the output end of the comparator U1A is connected with the anode of the diode D2, the output end of the comparator U1B is connected with the anode of the diode D3, the cathode of the diode D2 and the cathode of the diode D3 are respectively connected with two input ends of an OR gate OR1, the output end of the OR gate OR1 is connected with one end of a resistor R14, the other end of the resistor R14 is connected with the G pole of an MOS tube Q2, the S pole of the MOS tube Q2 is grounded GNDP, the D pole of the MOS tube Q2 is respectively connected with the anode of a diode D4, the cathode of a BUZZER BUZZER1 and one end of a coil of a relay RY1, the cathode of the diode BUZZER1 and the other end of the coil of the relay RY1 are commonly connected with the 15V output end of the auxiliary power circuit, and the two ends of the relay RY1 are respectively connected with the anode of a normally closed direct-current input power circuit and the input end of the DC/DC Flyback power circuit.

Further, the aforementioned DC/DC Flyback power circuit includes a second transformer, a MOS transistor Q3, a MOS transistor Q4, a MOS transistor Q5, a MOS transistor Q6, a diode D5, a resistor R15, a resistor R16, a resistor R17, a capacitor C8, a capacitor C9, a dial switch, a second control chip, and an output voltage control loop, where the positive electrode of the primary winding W3 of the second transformer is used as the positive electrode input terminal of the DC/DC Flyback power circuit, the negative electrode of the primary winding W3 of the second transformer is connected to the D electrode of the MOS transistor Q3, the G electrode of the MOS transistor Q3 is connected to the second control chip, the S electrode of the MOS transistor Q3 is connected to one end of the second control chip and one end of the resistor R16, the other end of the resistor R16 is used as the negative electrode input terminal of the DC/DC Flyback power circuit, the negative electrode of the secondary winding W4 of the second transformer is connected to one end of the resistor R15, the anode of the diode D5, the other end of the resistor R15 is connected to one end of the capacitor C8, the other end of the capacitor C8 is respectively connected with a cathode of a diode D5, one end of a capacitor C9, one end of a resistor R17 and an input end of an output voltage control loop, the connection point is used as a positive electrode output end and a current output end of a DC/DC Flyback power circuit, the output end of the output voltage control loop is connected with a second control chip, a D electrode of an MOS tube Q4 is connected with a positive electrode of a secondary winding W4 of the second transformer, a D electrode of the MOS tube Q5 and a D electrode of an MOS tube Q6 are respectively connected with a tap of the secondary winding W4 of the second transformer, S electrodes of the MOS tubes Q4, Q5 and Q6, the other end of the capacitor C9 and the other end of the resistor R17 are commonly grounded GNDS and are simultaneously used as a negative electrode output end of the DC/DC Flyback power circuit, G electrodes of the MOS tubes Q4, Q5 and Q6 are respectively connected with a G1 end, a G2 end and a G3 end of a dial switch, and a power supply end of the dial switch is connected with a 5V output end of an auxiliary power supply circuit.

Further, the output voltage control loop includes a resistor R18, a resistor R19, a resistor R20, a resistor R21, a resistor R22, a resistor R23, a resistor R24, a resistor R25, a resistor R26, a resistor R27, a resistor R28, a resistor R29, a resistor R30, a resistor R31, a resistor R32, a comparator U2A, a comparator U2B, a comparator U2C, a transistor Q7, a transistor Q8, a transistor Q9, a diode D6, a diode D7, a diode D8, a diode D9, a diode D10, a diode D11, a capacitor C10, a capacitor C11, a controllable precision voltage regulator source, and an optocoupler; one end of the resistor R18 is connected with the 5V output end of the auxiliary power supply circuit, the other end of the resistor R18 is respectively connected with the negative electrode input end of the comparator U2A and one end of the resistor R19, the other end of the resistor R19 is respectively connected with the negative electrode input end of the comparator U2B and one end of the resistor R20, the other end of the resistor R20 is respectively connected with the negative electrode input end of the comparator U2C and one end of the resistor R21, the other end of the resistor R21 is grounded GNDS, the positive electrode input ends of the comparator U2A, the comparator U2B and the comparator U2C are respectively connected with the G1 end, the G2 end and the G3 end of the dial switch, the output end of the comparator U2A is connected with the base electrode of the triode Q7 through the resistor R22, the output end of the comparator U2B is connected with the base electrode of the triode Q8 through the resistor R23, and the output end of the comparator U2C is connected with the base electrode of the triode Q9 through the resistor R24; a collector of the triode Q7, a collector of the triode Q8 and a collector of the triode Q9 are jointly used as input ends of an output voltage control loop, an emitter of the triode Q7 is respectively connected with one end of a resistor R27 and one end of a resistor R30, the other end of the resistor R27 is connected with an anode of a diode D8, and the other end of the resistor R30 is connected with an anode of a diode D11; an emitting electrode of the triode Q8 is respectively connected with one end of a resistor R26 and one end of a resistor R29, the other end of the resistor R26 is connected with the anode of a diode D7, and the other end of the resistor R29 is connected with the anode of a diode D10; an emitting electrode of the triode Q9 is respectively connected with one end of a resistor R25 and one end of a resistor R28, the other end of the resistor R25 is connected with the anode of a diode D6, and the other end of the resistor R28 is connected with the anode of a diode D9; the cathode of the diode D6, the cathode of the diode D7 and the cathode of the diode D8 are connected with one end of a resistor R31 and the anode of the optical coupler, the cathode of the diode D9, the cathode of the diode D10 and the cathode of the diode D11 are connected with one end of a resistor R32, one end of a capacitor C10 and the R end of a controllable precise voltage-stabilizing source, the other end of the resistor R32 and the A end of the controllable precise voltage-stabilizing source are grounded together, the K end of the controllable precise voltage-stabilizing source is connected with the other end of the capacitor C10, the other end of the resistor R31 and the cathode of the optical coupler respectively, the collector of the optical coupler is connected with one end of the capacitor C11 and serves as the output end of an output voltage control loop and is connected with a second control chip, and the emitter of the optical coupler and the other end of the capacitor C11 are grounded together.

Further, the output overvoltage and overcurrent protection circuit comprises a resistor R33, a resistor R34, a resistor R35, a resistor R36, a resistor R37, a resistor R38, a resistor R39, a resistor R40, a resistor R41, a resistor R42, a diode D12, a MOS transistor Q10, a comparator U3A, a comparator U3B, an OR gate OR2, a BUZZER2, and a relay RY2; one end of the resistor R33 is used as a voltage input end for outputting the overvoltage and overcurrent protection circuit, the other end of the resistor R33 is respectively connected with one end of the resistor R34 and the anode input end of the comparator U3A, and the other end of the resistor R34 is grounded GNDS; one end of the resistor R35 is used as a current input end for outputting the overvoltage and overcurrent protection circuit, the other end of the resistor R35 is respectively connected with one end of the resistor R36 and the positive input end of the comparator U3B, and the other end of the resistor R36 is grounded GNDS; one end of the resistor R37 is connected with the 5V output end of the auxiliary power supply circuit, the other end of the resistor R37 is respectively connected with one end of the resistor R38 and the negative input end of the comparator U3A, the other end of the resistor R38 is respectively connected with one end of the resistor R39 and the negative input end of the comparator U3B, and the other end of the resistor R39 is grounded GNDS; the power supply end of the comparator U3A and the power supply end of the comparator U3B are both connected with the 5V output end of the auxiliary power supply circuit, and the grounding end of the comparator U3A and the grounding end of the comparator U3B are both grounded GNDS; the output end of the comparator U3A is connected with one end of a resistor R40, the output end of the comparator U3B is connected with one end of a resistor R41, the other end of the resistor R40 and the other end of the resistor R41 are respectively connected with two input ends of an OR gate OR2, the output end of the OR gate OR2 is connected with one end of a resistor R42, the other end of the resistor R42 is connected with a G pole of an MOS tube Q10, an S pole of the MOS tube Q10 is grounded GNDS, a D pole of the MOS tube Q10 is respectively connected with an anode of a diode D12, a cathode of a BUZZER2, one end of a coil of a relay RY2, a cathode of the diode D12, an anode of the BUZZER BUZZER2 and the other end of the coil of the relay RY2 are jointly connected with a 5V output end of an auxiliary power circuit, and two ends of a normally closed switch of the relay RY2 are respectively connected with an output end and an anode input end of a DC/DC Flyback power circuit.

Further, the first control chip adopts a control chip UCC28600.

Further, the aforementioned second control chip adopts the control chip LD5535.

Further, the controllable precise voltage regulator source is a controllable precise voltage regulator source TL431.

Further, the optical coupler adopts an optical coupler CT817.

Has the advantages that:

1. the input voltage range of the power supply scheme is wider, and the application scenes of the power supply are increased to a certain extent;

2. the circuit design scheme can output 3 different voltages under the condition of not changing the duty ratio, and the power supply range is wider;

3. the circuit design scheme can realize the input overvoltage and undervoltage and output overcurrent and overvoltage protection functions, and has higher safety.

Drawings

FIG. 1 is a schematic of an overall architecture;

FIG. 2 is an auxiliary power supply circuit;

FIG. 3 is an input under-voltage protection circuit;

FIG. 4 is a DC/DC Flyback power circuit;

FIG. 5 is an output voltage control loop;

fig. 6 is an output overvoltage overcurrent protection circuit.

Detailed Description

In order to better understand the technical content of the present invention, specific embodiments are described below with reference to the accompanying drawings.

Aspects of the invention are described herein with reference to the accompanying drawings, in which a number of illustrative embodiments are shown. Embodiments of the invention are not limited to those illustrated in the drawings. It is to be understood that the invention is capable of implementation in any of the numerous concepts and embodiments described hereinabove or described in the following detailed description, since the disclosed concepts and embodiments are not limited to any embodiment. In addition, some aspects of the present disclosure may be used alone, or in any suitable combination with other aspects of the present disclosure.

Referring to fig. 1 to 6, the present invention provides a wide working range output voltage adjustable power supply, which is used for providing different output voltages for loads, and comprises an auxiliary power circuit, an input under-overvoltage protection circuit, a DC/DC Flyback power circuit, an output voltage control loop, and an output overvoltage and overcurrent protection circuit; the auxiliary power supply circuit gets electricity from the positive electrode and the negative electrode of the direct-current input power supply, the output end of the auxiliary power supply circuit is respectively connected with the input under-overvoltage protection circuit, the DC/DC Flyback power circuit, the output voltage control loop and the output overvoltage overcurrent protection circuit, and the auxiliary power supply circuit respectively provides power supply voltage required by work for the circuits connected with the auxiliary power supply circuit; the input under-overvoltage protection circuit is used for protecting the direct-current input voltage within a preset voltage range; the negative electrode input end of the DC/DC Flyback power circuit is connected with a direct-current input voltage VDC-, the positive electrode output end of the DC/DC Flyback power circuit is connected with the input end of the output voltage control loop for transmitting voltage signals, meanwhile, the positive electrode output end of the DC/DC Flyback power circuit is connected with the voltage input end and the current input end of the output overvoltage and overcurrent protection circuit for transmitting voltage signals and current signals, and the negative electrode output end of the DC/DC Flyback power circuit is connected with the negative electrode input end of the load; the output end of the output voltage control loop is connected with the DC/DC Flyback power circuit, and a signal with variable output voltage is transmitted to the control end of the DC/DC Flyback power circuit so as to control the triggering of the DC/DC Flyback power circuit, thereby forming feedback loops with different output voltages; the DC/DC Flyback power circuit is used for changing a direct current input voltage into 3 different output voltages so as to meet different power supply requirements of loads; the output end of the output overvoltage and overcurrent protection circuit is connected with the input end of the positive pole of the load, and the output overvoltage and overcurrent protection circuit monitors and protects the current and the voltage which are provided for the load.

In this embodiment, the operating principle of the DC/DC Flyback power circuit is as shown in fig. 4: the direct current input voltage is coupled through primary and secondary windings W3 and W4 of a second transformer to generate output voltage, and the output voltage is changed by changing the number of turns of the secondary winding of the second transformer; 3 MOS tubes Q4, Q5 and Q6 are added on the secondary side of the second transformer and are respectively connected with the secondary side winding of the second transformer by taps to form loops with different numbers of turns of the secondary side winding, the on and off of the MOS tubes Q4, Q5 and Q6 are controlled by a dial switch, namely G poles G1, G2 and G3 corresponding to the 3 MOS tubes are connected with the dial switch which is connected with 5V voltage, the corresponding MOS tubes are switched on when the switch is toggled once, the loops of the secondary side where the MOS tubes are located are switched on, and the corresponding voltage is output according to the number of turns of the secondary side winding.

In this embodiment, the operating principle of the output voltage control loop is as shown in fig. 5: the control loop consists of an optical coupler and a controllable precise voltage-stabilizing source TL431, one path of output voltage forms 2.5V reference voltage at a TL431 reference end through a voltage-dividing resistor, the other path of output voltage enables the optical coupler and the TL431 to work through a current-limiting resistor, and the optical coupler transmits an output voltage signal to a comp pin of a control chip LD5535 through electric-optical-electric conversion to form a feedback loop. 3 controllable voltage feedback loops are used for outputting 3 different voltages of 12V, 24V and 48V; different output voltages flow to the optocoupler and the TL431 through different triodes Q7, Q8 and Q9, the conduction of the triodes Q7, Q8 and Q9 is controlled by high levels output by different comparators U2A, U2B and U2C, the in-phase ends of the comparators U2A, U2B and U2C are respectively connected with G poles G1, G2 and G3 of 3 MOS tubes on the secondary side in a FIyback power circuit and are controlled by a dial switch, and the reverse ends are connected with the voltage after 5V voltage division; when the switch is toggled once, the corresponding comparator can output high level, the triode is conducted, and the corresponding output voltage can enter a feedback loop; meanwhile, the sizes of the divider resistor and the current limiting resistor through which different output voltages flow are different, namely, resistors R25, R26, R27, R28, R29 and R30 are added; diodes D6, D7, D8, D9, D10, D11 are added to prevent loops from forming between the branches.

In this embodiment, the overall circuit operation process is substantially as follows: one path of the direct current voltage generates 15V and 5V voltages through the auxiliary power circuit to provide required power supply voltage for the dial switch, a power chip LD5535 in the control circuit and other auxiliary circuits, so that the circuit can operate stably; one path passes through the input under-voltage and over-voltage protection circuit, and if the input voltage is higher than or lower than a set value, the input protection circuit enables the circuit to be disconnected, so that the circuit is protected. The set voltage flows into a Flyback power circuit controlled by a chip LD5535, the energy is stored in a magnetic core through a primary winding of a second transformer, then the secondary winding of the second transformer is coupled to generate output voltage, the output voltage is controlled through a voltage feedback circuit consisting of an optical coupler and a controllable precise voltage-stabilizing source TL431, and finally the output voltage flows to a load through an output overvoltage and overcurrent protection circuit to supply power to the load.

Although the invention has been described with reference to preferred embodiments, it is not intended to be limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the invention. Therefore, the protection scope of the present invention should be defined by the appended claims.

Claims

1. A wide working range output voltage adjustable power supply is used for providing different output voltages for a load and is characterized by comprising an auxiliary power supply circuit, an input under-overvoltage protection circuit, a DC/DC Flyback power circuit, an output voltage control loop and an output overvoltage and overcurrent protection circuit; the auxiliary power supply circuit gets electricity from the positive electrode and the negative electrode of the direct-current input power supply, the output end of the auxiliary power supply circuit is respectively connected with the input under-overvoltage protection circuit, the DC/DC Flyback power circuit, the output voltage control loop and the output overvoltage overcurrent protection circuit, and the auxiliary power supply circuit respectively provides power supply voltage required by work for the circuits connected with the auxiliary power supply circuit; the input under-overvoltage protection circuit is used for protecting the direct-current input voltage within a preset voltage range; the negative electrode input end of the DC/DC Flyback power circuit is connected with a direct-current input voltage VDC-, the positive electrode output end of the DC/DC Flyback power circuit is connected with the input end of an output voltage control loop and used for transmitting voltage signals, the positive electrode output end of the DC/DC Flyback power circuit is connected with the voltage input end and the current input end of an output overvoltage and overcurrent protection circuit and used for transmitting voltage signals and current signals, and the negative electrode output end of the DC/DC Flyback power circuit is connected with the negative electrode input end of a load; the output end of the output voltage control loop is connected with the DC/DC Flyback power circuit, and a signal with variable output voltage is transmitted to the control end of the DC/DC Flyback power circuit so as to control the triggering of the DC/DC Flyback power circuit, thereby forming feedback loops with different output voltages; the DC/DC Flyback power circuit is used for changing a direct current input voltage into 3 different output voltages so as to meet different power supply requirements of loads; the output end of the output overvoltage and overcurrent protection circuit is connected with the input end of the positive pole of the load, and the output overvoltage and overcurrent protection circuit monitors and protects the current and the voltage which are provided for the load.

2. The power supply with adjustable output voltage of wide operating range according to claim 1, wherein the auxiliary power supply circuit comprises a first transformer, a MOS transistor Q1, a capacitor C2, a capacitor C3, a capacitor C4, a capacitor C5, a resistor R1, a diode D1, a three-terminal regulator, and a first control chip, wherein the positive electrode of a primary winding W1 of the first transformer is connected to the positive electrode of the dc input power supply, the negative electrode of the primary winding W1 of the first transformer is connected to the D electrode of the MOS transistor Q1, the S electrode of the MOS transistor Q1 is connected to the negative electrode of the dc input power supply, and the positive electrode of a secondary winding W2 of the first transformer is commonly grounded with one end of the capacitor C2, one end of the capacitor C3, one end of the capacitor C4, one end of the capacitor C5, and the GND terminal of the three-terminal regulator; diode D1 positive pole is connected respectively to the secondary winding W2 negative pole of first transformer, electric capacity C1 one end, electric capacity C1 other end connecting resistance R1 one end, diode D1 negative pole is connected respectively to the resistance R1 other end, the electric capacity C2 other end, the electric capacity C3 other end, a control chip input, three terminal regulator's VIN end, auxiliary power supply circuit 15V output, MOS pipe Q1's the G utmost point is connected to a control chip output, the electric capacity C4 other end is connected respectively to three terminal regulator's OUT end, the electric capacity C5 other end, auxiliary power supply circuit 5V output.

3. The power supply with adjustable output voltage in a wide operating range according to claim 1, wherein the input under-overvoltage protection circuit comprises a resistor R2, a resistor R3, a resistor R4, a resistor R5, a resistor R6, a resistor R7, a resistor R8, a resistor R9, a resistor R10, a resistor R11, a resistor R12, a resistor R13, a resistor R14, a capacitor C6, a capacitor C7, a diode D2, a diode D3, a diode D4, a MOS transistor Q2, a comparator U1A, a comparator U1B, an OR gate OR1, a BUZZER1, and a relay RY1, an input end of the input under-overvoltage protection circuit is respectively connected with one end of the resistor R3 and one end of the resistor R4, another end of the resistor R3 is respectively connected with one end of the resistor R2, one end of the capacitor C6, and one end of the resistor R6, another end of the resistor R6 is respectively connected with one end of the resistor R10 and one end of the relay RY1, and a negative input end of the comparator U1A, another end of the resistor R2, another end of the capacitor C6 and another end of the resistor R10 are commonly grounded GNDP; the other end of the resistor R4 is connected with one end of a resistor R5, one end of a capacitor C7 and one end of a resistor R9 respectively, the other end of the resistor R9 is connected with one end of a resistor R13 and the positive input end of the comparator U1B respectively, and the other end of the resistor R5, the other end of the capacitor C7 and the other end of the resistor R13 are grounded GNDP together; the positive input end of the comparator U1A is respectively connected with one end of a resistor R11 and one end of a resistor R7, the other end of the resistor R11 is connected with one end of a resistor R12, the other end of the resistor R7 and one end of a resistor R8 are commonly grounded GNDP, and the other end of the resistor R8 and the other end of the resistor R12 are commonly connected with the negative input end of the comparator U1B; the power supply end of the comparator U1A and the power supply end of the comparator U1B are both connected with a 15V output end of the auxiliary power supply circuit, the grounding end of the comparator U1A and the grounding end of the comparator U1B are both grounded GNDP, the output end of the comparator U1A is connected with the anode of the diode D2, the cathode of the diode D2 and the cathode of the diode D3 are respectively connected with two input ends of an OR gate OR1, the output end of the OR gate OR1 is connected with one end of a resistor R14, the other end of the resistor R14 is connected with the G pole of an MOS tube Q2, the S pole of the MOS tube Q2 is grounded GNDP, the D pole of the MOS tube Q2 is respectively connected with the anode of a diode D4, the cathode of a BUZZER BUZZER1 and one end of a coil of a relay 1, the cathode of the diode ZZBUZZD 4, the anode of the BUZZER RY1 and the other end of the coil of the relay RY1 are commonly connected with a 15V output end of the auxiliary power supply circuit, and two ends of an normally closed switch of the relay RY1 are respectively connected with the anode of a direct-current input power supply circuit and an input end of a DC/DC Flyback power circuit.

4. The wide operating range output voltage adjustable power supply of claim 1, the DC/DC Flyback power circuit comprises a second transformer, an MOS tube Q3, an MOS tube Q4, an MOS tube Q5, an MOS tube Q6, a diode D5, a resistor R15, a resistor R16, a resistor R17, a capacitor C8, a capacitor C9, a dial switch, a second control chip and an output voltage control loop, wherein the positive pole of a primary winding W3 of the second transformer is used as the positive pole input end of the DC/DC Flyback power circuit, the negative pole of the primary winding W3 of the second transformer is connected with the D pole of the MOS tube Q3, the G pole of the MOS tube Q3 is connected with the second control chip, the S pole of the MOS tube Q3 is respectively connected with one end of the second control chip and one end of the resistor R16, the other end of the resistor R16 is used as the negative pole input end of the DC/DC Flyback power circuit, the negative pole of a secondary winding W4 of the second transformer is respectively connected with one end of the resistor R15, the anode of the diode D5, the other end of the resistor R15 is connected with one end of the capacitor C8, the other end of the capacitor C8 is respectively connected with one end of the cathode, one end of the capacitor C9, one end of the capacitor R17 and the output voltage control loop, the connection point is used as a positive electrode output end and a current output end of a DC/DC Flyback power circuit, an output end of an output voltage control loop is connected with a second control chip, a D electrode of an MOS tube Q4 is connected with a positive electrode of a secondary winding W4 of a second transformer, a D electrode of an MOS tube Q5 and a D electrode of an MOS tube Q6 are respectively connected with a tap of the secondary winding W4 of the second transformer, S electrodes of the MOS tubes Q4, Q5 and Q6, the other end of a capacitor C9 and the other end of a resistor R17 are commonly grounded GNDS and simultaneously used as a negative electrode output end of the DC/DC Flyback power circuit, G electrodes of the MOS tubes Q4, Q5 and Q6 are respectively connected with a G1 end, a G2 end and a G3 end of a dial switch, and power supply ends of the dial switch are connected with a 5V output end of an auxiliary power supply circuit.

5. The power supply with adjustable output voltage in wide operating range according to claim 4, wherein the output voltage control loop comprises a resistor R18, a resistor R19, a resistor R20, a resistor R21, a resistor R22, a resistor R23, a resistor R24, a resistor R25, a resistor R26, a resistor R27, a resistor R28, a resistor R29, a resistor R30, a resistor R31, a resistor R32, a comparator U2A, a comparator U2B, a comparator U2C, a triode Q7, a triode Q8, a triode Q9, a diode D6, a diode D7, a diode D8, a diode D9, a diode D10, a diode D11, a capacitor C10, a capacitor C11, a controllable precision voltage-stabilizing source and an optical coupler; one end of the resistor R18 is connected with a 5V output end of the auxiliary power supply circuit, the other end of the resistor R18 is respectively connected with a negative electrode input end of the comparator U2A and one end of the resistor R19, the other end of the resistor R19 is respectively connected with a negative electrode input end of the comparator U2B and one end of the resistor R20, the other end of the resistor R20 is respectively connected with a negative electrode input end of the comparator U2C and one end of the resistor R21, the other end of the resistor R21 is grounded GNDS, positive electrode input ends of the comparator U2A, the comparator U2B and the comparator U2C are respectively connected with a G1 end, a G2 end and a G3 end of the dial switch, an output end of the comparator U2A is connected with a base electrode of the triode Q7 through a resistor R22, an output end of the comparator U2B is connected with a base electrode of the triode Q8 through a resistor R23, and an output end of the comparator U2C is connected with a base electrode of the triode Q9 through a resistor R24; a collector of the triode Q7, a collector of the triode Q8 and a collector of the triode Q9 are jointly used as input ends of the output voltage control loop, an emitter of the triode Q7 is respectively connected with one end of a resistor R27 and one end of a resistor R30, the other end of the resistor R27 is connected with an anode of a diode D8, and the other end of the resistor R30 is connected with an anode of a diode D11; an emitting electrode of the triode Q8 is respectively connected with one end of a resistor R26 and one end of a resistor R29, the other end of the resistor R26 is connected with the anode of a diode D7, and the other end of the resistor R29 is connected with the anode of a diode D10; an emitting electrode of the triode Q9 is respectively connected with one end of a resistor R25 and one end of a resistor R28, the other end of the resistor R25 is connected with the anode of a diode D6, and the other end of the resistor R28 is connected with the anode of a diode D9; the cathode of the diode D6, the cathode of the diode D7 and the cathode of the diode D8 are connected with one end of a resistor R31 and the anode of the optocoupler together, the cathode of the diode D9, the cathode of the diode D10 and the cathode of the diode D11 are connected with one end of a resistor R32, one end of a capacitor C10 and the R end of the controllable precise voltage stabilizing source together, the other end of the resistor R32 and the A end of the controllable precise voltage stabilizing source are grounded together, the K end of the controllable precise voltage stabilizing source is connected with the other end of the capacitor C10, the other end of the resistor R31 and the cathode of the optocoupler respectively, the collector of the optocoupler is connected with one end of the capacitor C11 and serves as the output end of the output voltage control loop and is connected with the second control chip, and the emitter of the optocoupler and the other end of the capacitor C11 are grounded together.

6. The power supply with the adjustable output voltage and the wide operating range according to claim 1, wherein the output overvoltage and overcurrent protection circuit comprises a resistor R33, a resistor R34, a resistor R35, a resistor R36, a resistor R37, a resistor R38, a resistor R39, a resistor R40, a resistor R41, a resistor R42, a diode D12, a MOS transistor Q10, a comparator U3A, a comparator U3B, an OR gate OR2, a BUZZER BUZZER2 and a relay RY2; one end of the resistor R33 is used as a voltage input end for outputting the overvoltage and overcurrent protection circuit, the other end of the resistor R33 is respectively connected with one end of the resistor R34 and the anode input end of the comparator U3A, and the other end of the resistor R34 is grounded GNDS; one end of the resistor R35 is used as a current input end for outputting the overvoltage and overcurrent protection circuit, the other end of the resistor R35 is respectively connected with one end of the resistor R36 and the positive input end of the comparator U3B, and the other end of the resistor R36 is grounded GNDS; one end of the resistor R37 is connected with the 5V output end of the auxiliary power supply circuit, the other end of the resistor R37 is respectively connected with one end of the resistor R38 and the negative input end of the comparator U3A, the other end of the resistor R38 is respectively connected with one end of the resistor R39 and the negative input end of the comparator U3B, and the other end of the resistor R39 is grounded GNDS; the power supply end of the comparator U3A and the power supply end of the comparator U3B are both connected with the 5V output end of the auxiliary power supply circuit, and the grounding end of the comparator U3A and the grounding end of the comparator U3B are both grounded GNDS; the output end of the comparator U3A is connected with one end of a resistor R40, the output end of the comparator U3B is connected with one end of a resistor R41, the other end of the resistor R40 and the other end of the resistor R41 are respectively connected with two input ends of an OR gate OR2, the output end of the OR gate OR2 is connected with one end of a resistor R42, the other end of the resistor R42 is connected with a G pole of an MOS (metal oxide semiconductor) tube Q10, an S pole of the MOS tube Q10 is grounded GNDS, a D pole of the MOS tube Q10 is respectively connected with an anode of a diode D12, a cathode of a BUZZER2 and one end of a coil of a relay RY2, a cathode of the diode D12, an anode of the BUZZER BUZZER2 and the other end of the coil of the relay RY2 are jointly connected with a 5V output end of an auxiliary power supply circuit, and two ends of a normally-closed switch of the relay RY2 are respectively connected with an output end of a DC/DC Flyback power circuit and an anode input end of a load.

7. The adjustable power supply with wide operating range and output voltage as claimed in claim 2, wherein the first control chip is a control chip UCC28600.

8. The power supply with adjustable output voltage in wide operating range according to claim 4 or 5, wherein the second control chip is a control chip LD5535.

9. The power supply as claimed in claim 5, wherein the controllable precise voltage regulator is TL431.

10. The power supply with adjustable output voltage of wide working range according to claim 5, wherein the optical coupler adopts an optical coupler CT817.