CN218473031U

CN218473031U - Microprocessor controlled isolated AC-DC power supply

Info

Publication number: CN218473031U
Application number: CN202222483219.4U
Authority: CN
Inventors: 严益强
Original assignee: Guangdong Planning and Designing Institute of Telecommunications Co Ltd
Current assignee: Guangdong Planning and Designing Institute of Telecommunications Co Ltd
Priority date: 2022-09-19
Filing date: 2022-09-19
Publication date: 2023-02-10
Anticipated expiration: 2032-09-19

Abstract

The utility model relates to an isolated form alternating current-to-direct current power supply of microprocessor control, including input, output, DC-DC keep apart transform unit and step-down unit, the input of power is used for being connected in order to get the electricity with alternating current power supply electricity, and the output of power is used for connecting the load, and the input of power keeps apart the output that transform unit connects the power through step-down unit and DC-DC in proper order. Its isolation transform part is removed the low pressure side by traditional switching power supply high-voltage terminal, and adopt the electric capacity charge-discharge to realize keeping apart completely, the not enough of traditional switching power supply circuit has been avoided, no longer need the great ferrite core of volume isolation transformer and capacity and withstand voltage very high electrolytic capacitor, therefore, the switch tube capacity has been reduced, electrolytic capacitor is withstand voltage, thereby, the volume has significantly reduced, the efficiency is promoted, the cost is reduced, the system stability is improved, and because efficiency improves, compare in traditional switching power supply, the fin volume also very big reduction, in low-low consumption is used, can save the fin even.

Description

Microprocessor controlled isolated AC-DC power supply

Technical Field

The utility model relates to a switching power supply technical field, in particular to microprocessor control's isolated form exchanges and changes DC power supply.

Background

The switching power supply uses electronic switching devices (such as transistors, field effect transistors, thyristor, etc.) to continuously switch on and off the electronic switching devices through a control circuit, and the electronic switching devices perform pulse modulation on input voltage, thereby realizing DC/AC and DC/DC voltage conversion, and adjustable and automatic voltage stabilization of output voltage.

Switching power supplies generally have three modes of operation: frequency, pulse width fixed mode, frequency fixed, pulse width variable mode, frequency, pulse width variable mode. The former working mode is mainly used for DC/AC inverter power supply or DC/DC voltage conversion; the latter two operating modes are commonly used for switching regulated power supplies.

The conventional switching power supply needs larger allowance in a switching tube, an EMC filter circuit, a high-voltage capacitor and the like to ensure the normal operation of a system, so that the problems of larger volume, higher cost, lower efficiency and lower system stability of the conventional switching power supply are caused.

SUMMERY OF THE UTILITY MODEL

The utility model aims at providing a microprocessor control's isolated form exchanges and changes DC power supply, reduces switching power supply at the surplus of switch tube, EMC filter circuit, high-voltage capacitor demand.

Therefore, the microprocessor-controlled isolated AC-DC power supply comprises an input end, an output end, a DC-DC isolation conversion unit and a voltage reduction unit, wherein the input end of the power supply is electrically connected with an AC power supply to obtain electricity, the output end of the power supply is electrically connected with a load, and the input end of the power supply is electrically connected with the output end of the power supply sequentially through the voltage reduction unit and the DC-DC isolation conversion unit.

Furthermore, the device also comprises an EMC unit, an overcurrent and overvoltage protection unit, a full-wave rectification unit, a PWM unit, a dummy load and secondary voltage protection unit, a DC-DC isolation conversion unit, a micro-power supply unit and a microprocessor MCU unit;

the input end of the power supply is electrically connected to the output end of the power supply through an EMC unit, an overcurrent and overvoltage protection unit, a full-wave rectification unit, a PWM unit, a voltage reduction unit, a dummy load and secondary voltage protection unit and a DC-DC isolation conversion unit in sequence;

the microprocessor MCU unit is electrically connected with the PWM unit and the DC-DC isolation conversion unit, and the output end of the voltage reduction unit is electrically connected with the microprocessor MCU unit through the micropower power supply unit.

Further, the DC-DC isolation conversion unit includes an MOS transistor M3, an MOS transistor M4, a triode Q2, a triode Q3, a pull-up resistor R2, a pull-up resistor R3, a capacitor C3, a pull-down resistor R8, a pull-down resistor R10, a capacitor C4, and a capacitor C5;

the MOS tube M3 and the MOS tube M4 are both P-channel MOS tubes, the triode Q2 and the triode Q3 are both NPN type triodes, the source electrode of the MOS tube M3 is electrically connected with the positive electrode of the input end of the DC-DC isolation conversion unit, the drain electrode of the MOS tube M3 is electrically connected with the source electrode of the MOS tube M4, and the drain electrode of the MOS tube M4 is electrically connected with the positive electrode of the output end of the DC-DC isolation conversion unit;

the grid electrode of the MOS tube M3 is electrically connected with the collector electrode of the triode Q2, the emitter of the triode Q2 is electrically connected with the negative electrode of the input end of the DC-DC isolation conversion unit, the base electrode of the triode Q2 is electrically connected with the microprocessor MCU unit through the current limiting resistor R7, the two ends of the pull-down resistor R7 are respectively electrically connected with the base electrode of the triode Q2 and the negative electrode of the input end of the DC-DC isolation conversion unit, the two ends of the pull-up resistor R2 are respectively electrically connected with the grid electrode of the MOS tube M3 and the positive electrode of the input end of the DC-DC isolation conversion unit,

the grid electrode of the MOS tube M4 is electrically connected with the collector electrode of the triode Q3, the emitter of the triode Q3 is electrically connected with the negative electrode of the input end of the DC-DC isolation conversion unit, the base electrode of the triode Q3 is electrically connected with the MCU unit through the current-limiting resistor R9, the two ends of the pull-down resistor R9 are respectively electrically connected with the base electrode of the triode Q3 and the negative electrode of the input end of the DC-DC isolation conversion unit, the two ends of the pull-up resistor R2 are respectively electrically connected with the grid electrode of the MOS tube M4 and the source electrode of the MOS tube M4, and the negative electrode of the output end of the DC-DC isolation conversion unit is electrically connected with the negative electrode of the input end of the DC-DC isolation conversion unit;

one end of the capacitor C3 is electrically connected with the drain electrode of the MOS transistor M3, the other end of the capacitor C3 is electrically connected with the negative electrode of the input end of the DC-DC isolation conversion unit, and two ends of the capacitor C4 and the capacitor C5 are respectively electrically connected with the positive electrode and the negative electrode of the output end of the DC-DC isolation conversion unit.

Further, the overcurrent and overvoltage protection unit comprises a fuse BX1, a negative impedance thermistor NTC and a piezoresistor VR1, wherein the positive electrode of the input end of the overcurrent and overvoltage protection unit is electrically connected to the positive electrode of the output end through the fuse BX1 and the negative impedance thermistor NTC in sequence, one end of the piezoresistor VR1 is electrically connected with a node between the fuse BX1 and the negative impedance thermistor NTC, the other end of the piezoresistor VR1 is electrically connected with the negative electrode of the input end, and the negative electrode of the output end of the overcurrent and overvoltage protection unit is electrically connected with the negative electrode of the output end of the overcurrent and overvoltage protection unit.

Further, the dummy load and secondary voltage protection unit comprises a capacitor C1, a capacitor C2, an indicator light LED1 and a bidirectional clamping diode TVS1;

two ends of the capacitor C1, the capacitor C2 and the bidirectional clamping diode TVS1 are respectively and electrically connected with the positive electrode of the input end of the dummy load and the secondary voltage protection unit and the negative electrode of the input end of the dummy load and the secondary voltage protection unit, the positive electrode of the indicator light LED1 is electrically connected with the positive electrode of the input end of the secondary voltage protection unit, the negative electrode of the indicator light LED1 is electrically connected with the negative electrodes of the input ends of the dummy load and the secondary voltage protection unit, the positive electrode of the input end of the secondary voltage protection unit is electrically connected with the positive electrode of the output end of the secondary voltage protection unit, and the negative electrode of the input end of the secondary voltage protection unit is electrically connected with the negative electrode of the output end of the secondary voltage protection unit.

Further, the voltage reduction unit is specifically an L _ D voltage reduction and soft start unit, and includes an energy storage inductor L1, a freewheeling diode D5, an MOS transistor M2, a resistor R13, a capacitor C9, and a zener diode Z1;

one end of an energy storage inductor L1 is electrically connected with the anode of the input end of the L _ D voltage reduction and soft start unit, the other end of the energy storage inductor L1 is electrically connected with the drain electrode of an MOS tube M2, the MOS tube M2 is specifically an N-channel MOS tube, the source electrode of the MOS tube M2 is electrically connected with the anode of the output end of the L _ D voltage reduction and soft start unit, the grid electrode is electrically connected with the cathode of the output end of the L _ D voltage reduction and soft start unit through a capacitor C9, one end of a resistor R13 is electrically connected with the drain electrode of the MOS tube M2, the other end of the resistor R13 is electrically connected with the grid electrode of the MOS tube M2, the cathode of a voltage stabilizing diode Z1 is electrically connected with the grid electrode of the MOS tube M2, the anode is electrically connected with the anode of the input end of the L _ D voltage reduction and soft start unit, the anode of an input end of a freewheeling diode D5 is electrically connected with the cathode of the input end of the L _ D voltage reduction and soft start unit, the cathode of the input end of the L _ D voltage reduction and soft start unit is electrically connected with the cathode of the output end of the soft start unit.

Further, the overcurrent and overvoltage protection unit comprises a fuse BX1, a negative impedance thermistor NTC and a piezoresistor VR1, wherein the positive electrode of the input end of the overcurrent and overvoltage protection unit is electrically connected to the positive electrode of the output end of the overcurrent and overvoltage protection unit through the fuse BX1 and the negative impedance thermistor NTC in sequence, one end of the piezoresistor VR1 is electrically connected with a node between the fuse BX1 and the negative impedance thermistor NTC, the other end of the piezoresistor VR1 is electrically connected with the negative electrode of the input end of the overcurrent and overvoltage protection unit, and the negative electrode of the input end of the overcurrent and overvoltage protection unit is electrically connected with the negative electrode of the output end of the overcurrent and overvoltage protection unit.

Further, the PWM unit includes an MOS transistor M1, a pull-up resistor R1, a thermistor Rt1, a transistor Q1 and a pull-down resistor R12, the positive electrode of the input terminal of the PWM unit is electrically connected to the positive electrode of the output terminal of the PWM unit through the MOS transistor M1, the MOS transistor M1 is a P-channel MOS transistor, the source electrode of the MOS transistor M1 is electrically connected to the positive electrode of the input terminal of the PWM unit, the drain electrode of the MOS transistor M is electrically connected to the positive electrode of the output terminal of the PWM unit, the gate electrode of the MOS transistor Q1 is electrically connected to the collector electrode of the transistor Q1, one end of the pull-up resistor R1 is electrically connected to the positive electrode of the input terminal of the PWM unit, the other end of the pull-up resistor R1 is electrically connected to the collector electrode of the transistor Q1, the base electrode of the transistor Q1 is electrically connected to the microprocessor MCU unit through a current limiting resistor R6, the emitter electrode of the transistor Q1 is electrically connected to the negative electrode of the input terminal of the PWM unit, one end of the pull-down resistor R12 is electrically connected to the base electrode of the transistor Q1, the emitter of the transistor Q1 is electrically connected to the negative electrode of the PWM unit, the thermistor Rt1 is attached to the MOS transistor M1, and the thermistor MCU is electrically connected to the microprocessor unit.

The dummy load and secondary voltage protection unit is electrically connected with the DC-DC isolation conversion unit after passing through the voltage and current acquisition unit, and the microprocessor MCU unit is electrically connected with the voltage and current sampling unit.

Furthermore, the device also comprises an input key unit and a display screen unit, wherein the microprocessor MCU unit is electrically connected with the input key unit and the display screen unit.

Has the advantages that: the utility model provides an isolated form AC of microprocessor control changes DC power supply, its isolation transform part moves to the low pressure side, and adopt electric capacity charge-discharge to realize the isolation completely, the not enough of traditional switching power supply circuit has been avoided, no longer need the great isolation transformer of high volume and the high container of capacity and withstand voltage very high, therefore, at the switch tube capacity, obtain great reduction in the aspect of withstand voltage's requirement, thereby, the volume has significantly reduced, the efficiency has been promoted, the cost is reduced, the system stability has been improved, and because efficiency improves, compare in traditional switching power supply, the fin volume also very big reduction, in middle-low power consumption uses, can save the fin even.

The foregoing description is only an overview of the technical solutions of the present invention, and in order to make the technical means of the present invention more clearly understood, the present invention may be implemented in accordance with the contents of the description, and in order to make the above and other objects, features, and advantages of the present invention more clearly understood, the following description will particularly refer to specific embodiments of the present invention.

Drawings

Various other advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiments. The drawings are only for purposes of illustrating the preferred embodiments and are not to be construed as limiting the invention. Also, like reference numerals are used to refer to like parts throughout the drawings. In the drawings:

fig. 1 shows a schematic diagram of a unit module of a microprocessor-controlled isolated ac-to-dc power supply according to the present invention;

fig. 2 is a schematic circuit diagram of a microprocessor controlled isolated ac to dc power supply of the present invention;

fig. 3 shows a circuit schematic of an EMC unit of the invention;

fig. 4 shows a schematic circuit diagram of the over-current and over-voltage protection unit of the present invention;

fig. 5 shows a schematic circuit diagram of a full-wave rectification unit of the present invention;

fig. 6 shows a circuit schematic of a PWM unit of the present invention;

fig. 7 shows a circuit schematic diagram of the L _ D buck and soft start unit of the present invention;

fig. 8 shows a schematic circuit diagram of the dummy load and the secondary voltage protection unit of the present invention;

fig. 9 shows a schematic circuit diagram of the voltage current sampling unit of the present invention;

fig. 10 shows a circuit schematic of a DC-DC isolated conversion unit of the present invention;

fig. 11 shows a schematic circuit diagram of a micropower power supply unit of the present invention;

fig. 12 shows a schematic circuit diagram of the MCU unit, the input key unit and the display unit of the present invention.

Detailed Description

Exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be embodied in various forms and should not be limited by the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

The traditional switch power supply isolation is realized by converting 220V into a low-voltage transformer, and because the isolation transformer can generate counter electromotive force, correspondingly, serious problems are brought to a switch tube and electromagnetic interference. Therefore, the conventional switching power supply needs a large margin in a switching tube, an EMC filter circuit, a high-voltage capacitor and the like to ensure the normal operation of the system.

For this reason, referring to fig. 1-2, the microprocessor-controlled isolated ac-to-DC power supply of this embodiment includes an input terminal, an output terminal, an EMC unit, an over-current and over-voltage protection unit, a full-wave rectification unit, a PWM unit, an L _ D step-down and soft-start unit, a dummy load and secondary voltage protection unit, a voltage and current sampling unit, a DC-DC isolation conversion unit, a micro-power supply unit, a microprocessor MCU unit, an input key unit, and a display unit, wherein the input terminal is electrically connected to the output terminal through the EMC unit, the over-current and over-voltage protection unit, the full-wave rectification unit, the PWM unit, the L _ D step-down and soft-start unit, the dummy load and secondary voltage protection unit, the voltage and current sampling unit, and the DC-DC isolation conversion unit in sequence, thereby forming a main loop, the microprocessor MCU unit is electrically connected to the PWM unit of the main loop unit to control its operation, the voltage and current sampling unit is electrically connected to obtain sampling signals of voltage and current, and the output terminal of the L _ D step-down and soft-start unit is electrically connected to the microprocessor MCU unit through the micro-power supply unit to supply the microprocessor MCU.

Referring to fig. 3, the EMC unit specifically includes an existing EMC chip U1, an input end of which is used as an input end of an ac-to-dc power supply to electrically connect an external input power supply, in this embodiment, the EMC chip U1 is specifically the EMC chip of model 810911001, and the EMC chip adopts a common mode, a differential mode choke coil, an X capacitor, and a Y capacitor, which are widely used, to eliminate electromagnetic interference, thereby preventing a stray signal in an input 220 v ac line from interfering with a system, and also preventing multiple harmonic signals generated by a system high-frequency high-voltage switch from being coupled into an input-side high-voltage line, which affects the purity of the high-voltage power supply.

See fig. 4, the overcurrent and overvoltage protection unit includes a fuse BX1, a negative impedance thermistor NTC and a varistor VR1, the positive electrode of the input end of the overcurrent and overvoltage protection unit is electrically connected to the positive electrode of the output end through the fuse BX1 and the negative impedance thermistor NTC in sequence, one end of the varistor VR1 is electrically connected to the node between the fuse BX1 and the negative impedance thermistor NTC, and the other end of the varistor VR1 is electrically connected to the negative electrode of the input end, so that the fuse completes overcurrent protection, the negative impedance thermistor NTC limits the charging current of the capacitor when the fuse is powered on for the first time, and the varistor suppresses surge voltage interference of lightning, for example.

Referring to fig. 5, the full-wave rectification unit is specifically a bridge rectifier circuit, and specifically includes diodes D1, D2, D3, and D4, where an anode of the diode D1 is electrically connected to an anode of an input terminal of the bridge rectifier circuit, a cathode of the diode D1 is electrically connected to an anode of an output terminal of the bridge rectifier circuit, an anode of the diode D2 is electrically connected to a cathode of an input terminal of the bridge rectifier circuit, a cathode of the diode D2 is electrically connected to an anode of an output terminal of the bridge rectifier circuit, an anode of the diode D3 is electrically connected to a cathode of an output terminal of the bridge rectifier circuit, a cathode of the diode D3 is electrically connected to an anode of an input terminal of the bridge rectifier circuit, an anode of the diode D4 is electrically connected to a cathode of an input terminal of the bridge rectifier circuit, and a cathode of the diode D4 is electrically connected to a cathode of an input terminal of the bridge rectifier circuit.

Referring to fig. 6, the PWM unit includes a MOS transistor M1, a pull-up resistor R1, a thermistor Rt1, a transistor Q1 and a pull-down resistor R12, the positive electrode of the input terminal of the PWM unit is electrically connected to the positive electrode of the output terminal of the PWM unit through the MOS transistor M1, the MOS transistor M1 is a P-channel MOS transistor, the source electrode of the MOS transistor M1 is electrically connected to the positive electrode of the input terminal of the PWM unit, the drain electrode of the MOS transistor M is electrically connected to the positive electrode of the output terminal of the PWM unit, the gate electrode of the transistor Q1 is electrically connected to the collector electrode of the transistor Q1, one end of the pull-up resistor R1 is electrically connected to the positive electrode of the input terminal of the PWM unit, the other end of the pull-up resistor R1 is electrically connected to the collector electrode of the transistor Q1, the base electrode of the transistor Q1 is electrically connected to the MCU unit through a current limiting resistor R6, the emitter of the transistor Q1 is electrically connected to the negative electrode of the input terminal of the PWM unit, the microprocessor MCU unit controls the on-off of the transistor M1 by controlling the base voltage of the transistor Q1, the thermistor is attached to monitor the input terminal of the MOS transistor M1, and the thermistor Rt1 is electrically connected to monitor the heat of the transistor M1, thereby controlling the microprocessor MCU, and to collect the parameters of the microprocessor, and to control the microprocessor.

Referring to fig. 7, the L _ D buck and soft start unit includes an energy storage inductor L1, a freewheeling diode D5, a MOS transistor M2, a resistor R13, a capacitor C9, and a zener diode Z1, wherein one end of the L energy storage inductor L1 is electrically connected to an anode of an input end of the L _ D buck and soft start unit, and the other end is electrically connected to a drain of the MOS transistor M2, the MOS transistor M2 is specifically an N-channel MOS transistor, a source of the MOS transistor M2 is electrically connected to an anode of an output end of the L _ D buck and soft start unit, a gate of the MOS transistor M2 is electrically connected to a cathode of the L _ D buck and soft start unit through the capacitor C9, one end of the resistor R13 is electrically connected to a drain of the MOS transistor M2, and the other end of the MOS transistor M2, a cathode of the zener diode Z1 is electrically connected to a gate of the MOS transistor M2, an anode of the MOS transistor Z1 is electrically connected to an anode of the input end of the L _ D buck and soft start unit, an anode of the freewheeling diode D buck and soft start a charging circuit, and a charging circuit of the MOS transistor M2 is configured to limit a voltage of the charging circuit after the voltage of the MOS transistor M2 is turned on.

Referring to fig. 8, the dummy load and secondary voltage protection unit includes a capacitor C1, a capacitor C2, a resistor R4, an indicator light LED1 and a bidirectional clamping diode TVS1, wherein two ends of the capacitor C1, the capacitor C2 and the bidirectional clamping diode TVS1 are respectively electrically connected to an anode of an input terminal of the dummy load and secondary voltage protection unit and a cathode of an input terminal of the dummy load and secondary voltage protection unit, one end of the resistor R4 is electrically connected to an anode of an input terminal of the dummy load and secondary voltage protection unit, the other end is electrically connected to an anode of the indicator light LED1, and a cathode of the indicator light LED1 is electrically connected to a cathode of an input terminal of the dummy load and secondary voltage protection unit. The capacitors C1 and C2 form a filter circuit for smoothly outputting ripples of direct current signals, the bidirectional clamping diode TVS1 has the characteristics of large over-state current and high reaction speed, and is used as a secondary voltage protection unit to bear a second protection line of overvoltage protection, and the resistor R4 and the indicator light LED1 are connected in series to be used as a direct current output indicator light and bear the effect of being a dummy load, so that the PWM circuit can normally work.

See fig. 9, the voltage and current sampling unit includes a sampling resistor RS1, the resistance of the sampling resistor RS1 is specifically 0.1 ohm, one end of the sampling resistor RS1 is electrically connected to the positive electrode of the input end of the voltage and current sampling unit, the other end of the sampling resistor RS1 is electrically connected to the positive electrode of the output end of the voltage and current sampling unit, and both ends of the sampling resistor RS1 are electrically connected to the microprocessor MCU unit, so that the sampling signal is sent to the microprocessor MCU unit, and when the microprocessor MCU unit detects that the circuit or the current exceeds the threshold, the PWM signal is turned off, and an alarm indication is sent.

Referring to fig. 10, the DC-DC isolation and conversion unit includes an MOS transistor M3, an MOS transistor M4, a transistor Q2, a transistor Q3, a pull-up resistor R2, a pull-up resistor R3, a capacitor C3, a pull-down resistor R8, a pull-down resistor R10, a capacitor C4, and a capacitor C5, where the MOS transistor M3 and the MOS transistor M4 are both P-channel MOS transistors, the transistor Q2 and the transistor Q3 are both NPN-type transistors, a source of the MOS transistor M3 is electrically connected to an anode of an input terminal of the DC-DC isolation and conversion unit, a drain of the MOS transistor M3 is electrically connected to a source of the MOS transistor M4, a drain of the MOS transistor M4 is electrically connected to an anode of an output terminal of the DC-DC isolation and conversion unit, a gate of the MOS transistor M3 is electrically connected to a collector of the transistor Q2, and a transmitter of the transistor Q2 is electrically connected to a cathode of the input terminal of the DC-DC isolation and conversion unit, the base electrode of the triode Q2 is electrically connected with the microprocessor MCU unit through the current-limiting resistor R7, the two ends of the pull-down resistor R7 are respectively and electrically connected with the base electrode of the triode Q2 and the negative electrode of the input end of the DC-DC isolation conversion unit, the two ends of the pull-up resistor R2 are respectively and electrically connected with the grid electrode of the MOS tube M3 and the positive electrode of the input end of the DC-DC isolation conversion unit, the grid electrode of the MOS tube M4 is electrically connected with the collector electrode of the triode Q3, the emitter of the triode Q3 is electrically connected with the negative electrode of the input end of the DC-DC isolation conversion unit, the base electrode of the triode Q3 is electrically connected with the microprocessor MCU unit through the current-limiting resistor R9, the two ends of the pull-down resistor R9 are respectively and electrically connected with the base electrode of the triode Q3 and the negative electrode of the input end of the DC-DC isolation conversion unit, and the two ends of the pull-up resistor R2 are respectively and electrically connected with the grid electrode of the MOS tube M4 and the source electrode of the MOS tube M4;

one end of the capacitor C3 is electrically connected with the drain electrode of the MOS transistor M3, the other end of the capacitor C3 is electrically connected with the negative electrode of the input end of the DC-DC isolation conversion unit, and two ends of the capacitor C4 and the capacitor C5 are respectively electrically connected with the positive electrode and the negative electrode of the output end of the DC-DC isolation conversion unit, so that the output voltage is stabilized.

The MOS tubes M3 and M4 are in a disconnected state in a default mode, and the microprocessor MCU unit controls the on-off of the MOS tubes M3 and M4 by controlling the on-off of the triodes Q2 and Q3.

Referring to fig. 11, the micro power supply unit includes a micro power linear regulator chip LD0.

Referring to fig. 12, the MCU unit of the microprocessor adopts a general microprocessor, which adopts RISC instruction set, and is built-in with a working frequency of 0-20MHz oscillating circuit, EPROM, EEPROM, RAM, watchdog, low voltage detection, 10-bit ADC, reference voltage and at least 2 comparators.

The key input end element comprises keys K1, K2 and K3, the keys K1, K2 and K3 are respectively and electrically connected with the microprocessor MCU unit, and the display screen unit adopts a 256X 64LCD display screen and can display two lines of 32X 32 lattice characters.

The microprocessor-controlled isolated AC-DC power supply of the embodiment adopts single-chip microcomputer control to replace a special power supply control chip, and has strong flexibility and low cost;

the traditional PWM switching power supply framework is changed, the PWM power supply framework is optimized, a coupling transformer (including a self-excitation type, a flyback type and the like) with large volume and weight ratio and a high-voltage capacitor are eliminated, and the volume is greatly reduced under the same power;

the soft start and double current-limiting protection circuit is adopted, so that key components are prevented from being charged and struck by heavy current, the reliability and the stability of the system are improved, the EMI (electro-magnetic interference) is greatly reduced, and the EMI design is simplified;

because of the adoption of the singlechip control, the system can automatically select the optimal operation mode according to the detected parameters such as voltage, current and the like. (frequency conversion or fat width modulation mode), the operation mode dynamically changes in real time under the condition of ensuring output voltage and current, so that the system works in the optimal state, the heat productivity is reduced, and the system efficiency is improved;

a high-power switching tube temperature detection sensor is adopted, and when the temperature exceeds a set threshold value, an operation mode of automatic speed regulation is realized;

the safe operation of the system is ensured, the highest working frequency of the switch is 1MHz, the DC part works below 20V, the volumes of a switch tube, an inductor and a capacitor are greatly reduced, and the cost is reduced;

the on-off mode of the capacitor is directly controlled, power isolation is realized, noise generated by transformer isolation is thoroughly eliminated, PWM and a series voltage reduction circuit are integrated, power ripples are well eliminated, and a clean power supply is obtained;

the system adopts a singlechip with an internal ADC and a comparator, has the functions of overcurrent and overvoltage detection and control, ensures the safety and stability of the system, is provided with an EMC module, reduces the volume, adapts to the input voltage range of 90-260V, has the output voltage adjustable range of 2.0-20V/5A, can meet the requirements of most terminals of the Internet of things, and is wide in application.

It should be finally noted that the above embodiments are only intended to illustrate the technical solution of the present invention and not to limit the scope of the present invention, and although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced with other equivalents without departing from the spirit and scope of the technical solution of the present invention.

Claims

1. An isolated AC-to-DC power supply controlled by a microprocessor is characterized in that: the power supply comprises an input end, an output end, a DC-DC isolation conversion unit and a voltage reduction unit, wherein the input end of the power supply is electrically connected with an alternating current power supply to get electricity, the output end of the power supply is connected with a load, and the input end of the power supply is connected with the output end of the power supply sequentially through the voltage reduction unit and the DC-DC isolation conversion unit.

2. The microprocessor controlled isolated ac to dc power supply of claim 1, wherein: the device also comprises an EMC unit, an overcurrent and overvoltage protection unit, a full-wave rectification unit, a PWM unit, a dummy load and secondary voltage protection unit, a DC-DC isolation conversion unit, a micro-power supply unit and a microprocessor MCU unit;

3. The microprocessor controlled isolated ac to dc power supply of claim 2, wherein: the DC-DC isolation conversion unit comprises an MOS tube M3, an MOS tube M4, a triode Q2, a triode Q3, a pull-up resistor R2, a pull-up resistor R3, a capacitor C3, a pull-down resistor R8, a pull-down resistor R10, a capacitor C4 and a capacitor C5;

the grid of the MOS tube M3 is electrically connected with the collector of the triode Q2, the emitter of the triode Q2 is electrically connected with the negative electrode of the input end of the DC-DC isolation conversion unit, the base electrode of the triode Q2 is electrically connected with the MCU unit through the current limiting resistor R7, the two ends of the pull-down resistor R7 are respectively electrically connected with the base electrode of the triode Q2 and the negative electrode of the input end of the DC-DC isolation conversion unit, the two ends of the pull-up resistor R2 are respectively electrically connected with the grid of the MOS tube M3 and the positive electrode of the input end of the DC-DC isolation conversion unit,

4. The microprocessor-controlled isolated ac-to-dc power supply of claim 2, wherein: the overcurrent and overvoltage protection unit comprises a fuse BX1, a negative impedance thermistor NTC and a piezoresistor VR1, the positive electrode of the input end of the overcurrent and overvoltage protection unit is electrically connected to the positive electrode of the output end through the fuse BX1 and the negative impedance thermistor NTC in sequence, one end of the piezoresistor VR1 is electrically connected with a node between the fuse BX1 and the negative impedance thermistor NTC, the negative electrode of the input end is electrically connected with the other end of the piezoresistor VR1, and the negative electrode of the output end of the overcurrent and overvoltage protection unit is electrically connected with the negative electrode of the output end of the overcurrent and overvoltage protection unit.

5. The microprocessor-controlled isolated ac-to-dc power supply of claim 2, wherein: the dummy load and secondary voltage protection unit comprises a capacitor C1, a capacitor C2, an indicator light LED1 and a bidirectional clamping diode TVS1;

two ends of the capacitor C1, the capacitor C2 and the bidirectional clamping diode TVS1 are respectively and electrically connected with the positive pole of the input end of the dummy load and the secondary voltage protection unit and the negative pole of the input end of the dummy load and the secondary voltage protection unit, the positive pole of the indicator light LED1 is electrically connected with the positive pole of the input end of the secondary voltage protection unit, the negative pole of the indicator light LED1 is electrically connected with the negative poles of the input ends of the dummy load and the secondary voltage protection unit, the positive pole of the input end of the secondary voltage protection unit is electrically connected with the positive pole of the output end of the secondary voltage protection unit, and the negative pole of the input end of the secondary voltage protection unit is electrically connected with the negative pole of the output end of the secondary voltage protection unit.

6. The microprocessor-controlled isolated ac-to-dc power supply of claim 2, wherein: the voltage reduction unit is specifically an L _ D voltage reduction and soft start unit and comprises an energy storage inductor L1, a freewheeling diode D5, an MOS (metal oxide semiconductor) tube M2, a resistor R13, a capacitor C9 and a voltage stabilizing diode Z1;

one end of an energy storage inductor L1 is electrically connected with the anode of the input end of the L _ D voltage reduction and soft start unit, the other end of the energy storage inductor L1 is electrically connected with the drain electrode of an MOS tube M2, the MOS tube M2 is specifically an N-channel MOS tube, the source electrode of the MOS tube M2 is electrically connected with the anode of the output end of the L _ D voltage reduction and soft start unit, the grid electrode is electrically connected with the cathode of the output end of the L _ D voltage reduction and soft start unit through a capacitor C9, one end of a resistor R13 is electrically connected with the drain electrode of the MOS tube M2, the other end of the resistor R13 is electrically connected with the grid electrode of the MOS tube M2, the cathode of a voltage stabilizing diode Z1 is electrically connected with the grid electrode of the MOS tube M2, the anode is electrically connected with the anode of the input end of the L _ D voltage reduction and soft start unit, the anode of a freewheeling diode D5 is electrically connected with the cathode of the input end of the L _ D voltage reduction and soft start unit, the cathode of the input end of the L _ D voltage reduction and soft start unit is electrically connected with the cathode of the output end of the L _ D voltage reduction and soft start unit.

7. The microprocessor controlled isolated ac to dc power supply of claim 2, wherein: the overcurrent and overvoltage protection unit comprises a fuse BX1, a negative impedance thermistor NTC and a piezoresistor VR1, the positive electrode of the input end of the overcurrent and overvoltage protection unit is electrically connected to the positive electrode of the output end of the overcurrent and overvoltage protection unit through the fuse BX1 and the negative impedance thermistor NTC in sequence, one end of the piezoresistor VR1 is electrically connected with a node between the fuse BX1 and the negative impedance thermistor NTC, the other end of the piezoresistor VR1 is electrically connected with the negative electrode of the input end of the overcurrent and overvoltage protection unit, and the negative electrode of the input end of the overcurrent and overvoltage protection unit is electrically connected with the negative electrode of the output end of the overcurrent and overvoltage protection unit.

8. The microprocessor controlled isolated ac to dc power supply of claim 2, wherein: the PWM unit comprises an MOS (metal oxide semiconductor) tube M1, a pull-up resistor R1, a thermistor Rt1, a triode Q1 and a pull-down resistor R12, wherein the anode of the input end of the PWM unit is electrically connected to the anode of the output end of the PWM unit through the MOS tube M1, the MOS tube M1 is a P-channel MOS tube, the source electrode of the MOS tube is electrically connected with the anode of the input end of the PWM unit, the drain electrode of the MOS tube is electrically connected with the anode of the output end of the PWM unit, the grid electrode of the MOS tube Q1 is electrically connected with the collector electrode of the triode Q1, one end of the pull-up resistor R1 is electrically connected with the anode of the input end of the PWM unit, the other end of the pull-up resistor R1 is electrically connected with the collector electrode of the triode Q1, the base electrode of the triode Q1 is electrically connected with the microprocessor MCU unit through a current-limiting resistor R6, the emitter electrode of the triode Q1 is electrically connected with the cathode of the input end of the PWM unit, one end of the pull-down resistor R12 is electrically connected with the cathode of the input end of the PWM unit, the base electrode of the triode Q1, the emitter of the thermistor Rt1 is electrically connected with the cathode of the input end of the PWM unit, the thermistor Rt1 is attached to the MOS tube M1, and the MCU unit, and the thermistor Rt1 is electrically connected with the MCU unit.

9. The microprocessor controlled isolated ac to dc power supply of claim 2, wherein: the pseudo load and the secondary voltage protection unit are electrically connected with the DC-DC isolation conversion unit after passing through the voltage and current acquisition unit, and the microprocessor MCU unit is electrically connected with the voltage and current sampling unit.

10. The microprocessor controlled isolated ac to dc power supply of claim 2, wherein: the MCU unit of the microprocessor is electrically connected with the input key unit and the display screen unit.