Alternating current and direct current dual-purpose power supply circuit with wide input range

Abstract

An AC-DC dual-purpose power supply circuit with a wide input range belongs to the field of AC-DC dual-purpose power supplies and comprises a power supply protection circuit, a filtering module, a DC series negative feedback voltage stabilization module and an AC bridge rectifier module. An alternating current input power supply passes through the power supply protection circuit and the filtering module and then is input into the alternating current bridge rectifier module, and alternating current is rectified into direct current. A direct-current input power supply passes through the power supply protection circuit and the filtering module and then is input into the direct-current series negative feedback voltage stabilization module to reduce the voltage, then the voltage is combined with direct current output by the alternating-current bridge rectifier module, and finally direct-current output stable voltage is achieved. The circuit solves the problems that an existing alternating-current and direct-current dual-purpose power supply circuit is narrow in input voltage range and cannot be directly applied to an industrial site, the power supply circuit is simplified, the manufacturing cost is reduced, the weight is reduced, use is safe and reliable, and the requirements of the actual complex industrial site are met.

Description

Technical Field

[0001] The utility model relates to the technical field of an AC / DC dual-purpose power supply, in particular to an AC / DC dual-purpose power supply circuit with a wide input range. Background Art

[0002] The AC / DC dual-purpose power supply circuit is a power supply circuit that is compatible with AC and DC inputs. The same circuit can adapt to both AC 220V power supply and DC 24V power supply, which can effectively solve the problem of AC and DC compatibility in power supply.

[0003] The key problem that the AC / DC dual-purpose power supply circuit needs to solve is the input range of the power supply. At present, some small instruments or equipment that meet the requirements of AC / DC dual-purpose power supply circuits are designed and used, and the input AC voltage range is generally 198-235.4V , the input DC voltage range is generally 18-28V, the input voltage range requirements are strict, and the adaptability range is narrow. However, in industrial sites, the AC voltage range provided is generally 160V-250V, and the DC voltage range is generally 15V-30V. Therefore, the above-mentioned AC / DC dual-purpose power supply circuit cannot be directly applied in the complex industrial sites in reality. They generally adopt the addition of components such as inverters and transformers in the circuit to adapt to the needs of the site, where the inverter converts the input DC power into AC power, and the transformer steps up or down the voltage according to the transformer turns ratio. These added components will cause the overall design of the above-mentioned AC / DC dual-purpose power supply circuit to be complex, large in size, heavy in weight, and high in cost. Or in order to simplify circuit design, reduce weight and lower costs, the user designs the power circuit of the instrument to be a DC 24V input, and then configures an AC 220V to DC 24V device at the industrial site where there is no DC power supply. Although this method reduces the complexity of the power circuit, reduces the weight of the power supply components and reduces the cost, it loses the convenience of AC and DC compatibility in the power supply, and is not a true AC / DC dual-purpose power circuit. Summary of the invention

[0004] In order to solve the problems of narrow input voltage adaptation range in existing AC / DC dual-purpose power supply circuits, complex overall circuit after adding inverters and transformers, heavy weight and high cost, the utility model provides an AC / DC dual-purpose power supply circuit with a wide input range. By integrating an AC bridge rectifier module with a DC series negative feedback voltage stabilizing module, compatible AC and DC power supplies can be achieved, effectively solving the problem that the input voltage range of existing AC / DC dual-purpose power supply circuits is narrow and cannot be directly used in industrial sites. It has a wider input voltage range and can be used directly on site, thereby simplifying the power supply circuit, reducing the manufacturing cost, reducing the weight, and being safe and reliable to use, meeting the needs of complex real industrial sites.

[0005] The specific technical scheme is: a wide input range AC / DC dual-purpose power supply circuit, including a power supply protection circuit, a filter module, an AC bridge rectifier module and a DC series negative feedback voltage regulator module; the filter module is respectively connected to the power supply protection circuit, the DC series negative feedback voltage regulator module and the AC bridge rectifier module, and the DC series negative feedback voltage regulator module and the AC bridge rectifier module are connected to each other; the power supply protection circuit is used for circuit breaking protection, overload protection and overvoltage protection of the circuit; the filter module is used to filter the clutter in the input power supply; the AC bridge rectifier module is used to convert the input AC power into DC power; the DC series negative feedback voltage regulator module is used to reduce and adjust the input DC power, and after combining with the DC power output by the AC bridge rectifier module, the DC output stable voltage.

[0006] The power supply protection circuit is composed of a capacitor C1, a varistor RP, a gas discharge tube DT, a fuse F and a current limiting resistor R1; the specific circuit connection is that the capacitor C1, the varistor RP, and the gas discharge tube DT are connected in parallel at both ends of the power supply in sequence, one end of the fuse F is connected to the capacitor C1, the varistor RP, and the end of the gas discharge tube DT connected to the positive pole of the power supply, and the other end of the fuse F is connected in series with one end of the current limiting resistor R.

[0007] The filter module consists of a discharge resistor R2, a capacitor C2, and an inductor L; the specific circuit connection is that one end of the discharge resistor R2 is respectively connected to pin 2 of the inductor L and the other end of the current limiting resistor R1, the other end of the discharge resistor R2 is respectively connected to pin 1 of the inductor L and the negative pole of the power terminal, and the two ends of the capacitor C2 are respectively connected to pins 3 and 4 of the inductor L.

[0008] The AC bridge rectifier module is composed of a voltage-dividing capacitor C3, a rectifier bridge D1, a filter capacitor C4 and a filter capacitor C5; the specific circuit connection is that one end of the voltage-dividing capacitor C3 is connected to pin 3 of the inductor L, and the other end is connected to pin 3 of the rectifier bridge D1, pin 2 of the rectifier bridge D1 is grounded, pin 4 is connected to pin 4 of the inductor L, and pin 1 is respectively connected to the positive ends of the filter capacitor C4 and the filter capacitor C5, and the negative ends of the filter capacitor C4 and the filter capacitor C5 are respectively grounded.

[0009] The DC series negative feedback voltage stabilization module is composed of a voltage stabilizing diode D5, a resistor R8, a sampling resistor R6, a resistor R7, a capacitor C6, a capacitor C7, an operational amplifier UA, a voltage stabilizing diode D4, a transistor Q2, a diode D3, a field effect transistor Q1, a switching diode D2, a current limiting resistor R5, a resistor R4 and a resistor R3; the specific circuit connection is that the positive electrode of the voltage stabilizing diode D5 is respectively connected to pin 3 of the forward input terminal of the operational amplifier UA and one end of the resistor R8, the negative electrode of the voltage stabilizing diode D5 is connected to the output Vout, and the other end of the resistor R8 is grounded; one end of the sampling resistor R6 is connected to the output Vout, and the other end of the sampling resistor R6 is respectively connected to pin 2 of the reverse input terminal of the operational amplifier UA and one end of the resistor R7, and the other end of the resistor R7 is grounded; the positive electrode of the power supply of the operational amplifier UA is connected to the output Vout and one end of the capacitor C6, and the operational amplifier UA The negative electrode of the power supply and the other end of the capacitor C6 are grounded, one end of the capacitor C7 is connected to the output terminal 1 pin of the operational amplifier UA, and the other end of the capacitor C7 is connected to the reverse input terminal 2 pin of the operational amplifier UA; the positive electrode of the switching diode D2 is connected to one end of the resistor R3, the negative electrode of the switching diode D2 is connected to the drain (D) of the field effect transistor Q1, the source (S) of the field effect transistor Q1 is connected to one end of the current limiting resistor R5, the gate (G) of the field effect transistor Q1 is connected to one end of the resistor R4, and the other end of the current limiting resistor R5 is respectively connected to the positive electrode of the diode D3 and the output Vout; the other end of the resistor R4 is respectively connected to the other end of the resistor R3, the negative electrode of the diode D3 and the collector of the transistor Q2; the emitter of the transistor Q2 is connected to the negative electrode of the voltage-stabilizing diode D4, and the positive electrode of the voltage-stabilizing diode D4 is grounded; the base of the transistor Q2 is connected to the output terminal 1 pin of the operational amplifier UA.

[0010] The DC series negative feedback voltage stabilization module consists of a reference circuit, a sampling circuit, a comparison circuit, and an adjustment circuit; the reference circuit includes a voltage stabilizing diode D5 and a resistor R8, which are used to provide a reference voltage; the sampling circuit includes a sampling resistor R6 and a resistor R7, which are used to obtain a sampling voltage; the comparison circuit includes a capacitor C6, a capacitor C7, and an operational amplifier UA, which are used to compare the reference voltage and the sampling voltage; the adjustment circuit includes a voltage stabilizing diode D4, a transistor Q2, a diode D3, a field effect transistor Q1, a switching diode D2, a current limiting resistor R5, a resistor R4, and a resistor R3, which are used to adjust the conduction degree of the field effect transistor Q1 according to the comparison result to keep the output voltage stable.

[0011] The beneficial effects of the utility model are: 1. Compatible with AC and DC power supply, with a wide input voltage application range. The utility model effectively solves the problem of AC and DC compatibility in power supply, and the input AC voltage range is 20V-250V, and the input DC voltage range is 14V-60V ，It can be directly applied to the existing industrial field environment with AC voltage range of 160V-250V and DC voltage range of 15V-30V.

[0012] 2. Simplified the design of the power supply circuit and reduced the production cost. The components used in this patent are common components such as diodes, field effect transistors, and operational amplifiers. Compared with the existing AC / DC dual-purpose power supply circuits that use complex circuits such as inverters and transformers, the circuit design is simple and the component cost is low.

[0013] 3. Reduced the volume and weight of components. The transformer used in the existing AC / DC dual-purpose power supply circuit is generally 10*10*6, and needs to be made by copper wire winding, which is large in size and heavy in weight. The circuit designed by the utility model uses ordinary components, is small in size and light in weight, and can be applied to instruments with power consumption less than 3W, meeting the power supply requirements of small instruments and electrical equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is the circuit composition block diagram;

[0015] Figure 2 It is a circuit schematic. DETAILED DESCRIPTION

[0016] The utility model is further described below in conjunction with the accompanying drawings.

[0017] Figure 1 Is the circuit block diagram, such as Figure 1 As shown, a wide input range AC / DC dual-purpose power supply circuit includes AC input / DC input, power protection circuit, filter module, AC bridge rectifier module, DC series negative feedback voltage regulator module and DC output. AC input / DC input is used to connect AC and DC power supplies, and the two power supplies share a terminal. The power protection circuit is used to protect the subsequent circuit from being burned by the high voltage power supply when there is an excessive current in the circuit. The filter module can filter the clutter in the input power supply. The AC bridge rectifier module can realize the conversion of AC power into DC power. The DC series negative feedback voltage regulator module reduces the input DC voltage and adjusts the output voltage in real time according to the input voltage. The output DC power is combined with the DC power converted by the AC bridge rectifier module to output a stable DC voltage. The AC input power is input into the AC bridge rectifier module after passing through the power protection circuit and the filter module to rectify the AC power into DC power; the DC input power is input into the DC series negative feedback voltage regulator module to reduce the voltage after passing through the power protection circuit and the filter module, and then integrated with the DC power output by the AC bridge rectifier module, and finally the DC output is a stable voltage.

[0018] Figure 2 Is the circuit schematic, such as Figure 2As shown, the input power is divided into AC and DC. The AC voltage input range is 20V-250V, and the DC voltage input range is 14V-60V. The two power supplies share the same power terminal 19-253VAC / 14-60VDC.

[0019] The power protection circuit is composed of capacitor C1, surge protection varistor RP, lightning protection gas discharge tube DT, fuse F and current limiting resistor R1. Capacitor C1, varistor RP and gas discharge tube DT are connected in parallel at both ends of the power supply terminal. One end of fuse F is connected to the end of capacitor C1, varistor RP and gas discharge tube DT connected to the positive pole of the power supply terminal, and the other end of fuse F is connected in series with one end of current limiting resistor R. After the input AC / DC voltage is protected by capacitor C1, varistor RP and gas discharge tube DT, it is protected and current limited by fuse F and current limiting resistor R1.

[0020] The filter module is composed of a discharge resistor R2, a capacitor C2, and an inductor L. One end of the discharge resistor R2 is connected to the 2nd foot of the inductor L and the other end of the current limiting resistor R1 respectively, the other end of the discharge resistor R2 is connected to the 1st foot of the inductor L and the negative electrode of the power terminal respectively, and the two ends of the capacitor C2 are connected to the 3rd foot and the 4th foot of the inductor L respectively. The filter module can filter the clutter in the subsequent circuit. The input voltage after current limiting passes through the filter module and the clutter in the voltage is filtered out.

[0021] The AC bridge rectifier module consists of a voltage divider capacitor C3, a rectifier bridge D1, a filter capacitor C4 and a filter capacitor C5. One end of the voltage divider capacitor C3 is connected to pin 3 of the inductor L, and the other end is connected to pin 3 of the rectifier bridge D1; pin 2 of the rectifier bridge D1 is grounded, pin 4 is connected to pin 4 of the inductor L, and pin 1 is connected to the positive ends of the filter capacitor C4 and the filter capacitor C5 respectively; the negative ends of the filter capacitor C4 and the filter capacitor C5 are grounded respectively. The DC input voltage cannot pass through this module. After the AC 220V input voltage passes through the power protection circuit and the filter module, it is divided by the voltage divider capacitor C3. A part of the AC voltage falls on the voltage divider capacitor C3, and the other part of the AC voltage is full-wave rectified by the rectifier bridge D1 to shape the AC voltage into a DC voltage, and then output through the filter capacitor C4 and the filter capacitor C5. The output voltage is Vout.

[0022] The DC series negative feedback voltage regulator module consists of a reference circuit, a sampling circuit, a comparison circuit, and an adjustment circuit. The reference circuit consists of a voltage regulator diode D5 and a resistor R8, the sampling circuit consists of a sampling resistor R6 and a resistor R7, the comparison circuit consists of a capacitor C6, a capacitor C7, and an operational amplifier UA, and the adjustment circuit consists of a voltage regulator diode D4, a transistor Q2, a diode D3, a field effect transistor Q1, a switching diode D2, a current limiting resistor R5, a resistor R4, and a resistor R3. The positive electrode of the voltage regulator diode D5 in the reference circuit is respectively connected to the 3rd pin of the forward input terminal of the operational amplifier UA and one end of the resistor R8, the negative electrode of the voltage regulator diode D5 is connected to the output Vout, and the other end of the resistor R8 is grounded. One end of the sampling resistor R6 in the sampling circuit is connected to the output Vout, and the other end of the sampling resistor R6 is respectively connected to the 2nd pin of the reverse input terminal of the operational amplifier UA and one end of the resistor R7, and the other end of the resistor R7 is grounded. In the comparison circuit, the positive electrode of the power supply of the operational amplifier UA is connected to the output Vout and one end of the capacitor C6, the negative electrode of the power supply of the operational amplifier UA and the other end of the capacitor C6 are grounded, one end of the capacitor C7 is connected to the output terminal 1 of the operational amplifier UA, and the other end of the capacitor C7 is connected to the 2nd pin of the reverse input terminal of the operational amplifier UA. In the adjustment circuit, the positive electrode of the switching diode D2 is connected to one end of the resistor R3, the negative electrode of the switching diode D2 is connected to the drain (D) of the field effect transistor Q1, the source (S) of the field effect transistor Q1 is connected to one end of the current limiting resistor R5, the gate (G) of the field effect transistor Q1 is connected to one end of the resistor R4, and the other end of the current limiting resistor R5 is respectively connected to the positive electrode of the diode D3 and the output Vout. The other end of the resistor R4 is respectively connected to the other end of the resistor R3, the negative electrode of the diode D3 and the collector of the transistor Q2. The emitter of the transistor Q2 is connected to the negative electrode of the voltage-stabilizing diode D4, and the positive electrode of the voltage-stabilizing diode D4 is grounded. The base of the transistor Q2 is connected to the output terminal 1 of the operational amplifier UA.

[0023] When the DC input voltage is protected and limited by the power protection circuit, and then filtered by the filter module, the field effect tube Q1 is turned on by the switch diode D2 and the resistors R3 and R4, and the voltage of the field effect tube Q1 passes through the current limiting resistor R5 to form the output voltage Vout. The reference voltage in the reference circuit is the reference voltage V1 provided by the voltage stabilizing diode D5, which is input to the positive input terminal 3 of the operational amplifier UA. The sampling resistors R6 and R7 in the sampling circuit divide the output voltage Vout to obtain the sampling voltage V2, which is input to the reverse input terminal 2 of the operational amplifier UA. The operational amplifier UA in the comparison circuit compares the input reference voltage V1 with the sampling voltage V2, and adjusts the conduction degree of the field effect tube Q1 through the transistor Q2 to keep the voltage of Vout stable. When the output voltage Vout increases, the sampling voltage V2 also increases, resulting in a smaller difference between the sampling voltage V2 and the reference voltage V1. The output voltage of the operational amplifier is input to the base of the transistor Q2. At the same time, the input DC power supply inputs part of the current to the collector of the transistor Q2 through the resistor R3, so that the transistor Q2 is turned on, and the transistor Q2 always works in the amplification area. Because the difference between the sampling voltage V2 and the reference voltage V1 becomes smaller, the output current of the operational amplifier becomes smaller. Due to the effect of the voltage zener diode D4, the collector current of the transistor Q2 is reduced, thereby reducing the conduction degree of the field effect transistor Q1 and reducing the output voltage Vout. When the output voltage Vout decreases, the sampling voltage V2 also decreases, resulting in a larger difference between the sampling voltage V2 and the reference voltage V1. The output voltage of the operational amplifier is input to the base of the transistor Q2, the transistor Q2 is turned on, and the transistor Q2 always works in the amplification area. Because the difference between the sampling voltage V2 and the reference voltage V1 increases, the output current of the operational amplifier increases. Due to the action of the voltage-stabilizing diode D4, the collector current of the transistor Q2 increases, thereby enhancing the conduction degree of the field-effect transistor Q1 and increasing the output voltage Vout.

[0024] The overall working process of the utility model circuit is:

[0025] When the input power is 220V AC, after being protected by capacitor C1, surge protection varistor RP, and lightning protection gas discharge tube DT, the current passes through fuse F and current limiting resistor R1 and then flows into common mode inductor L for filtering, and then is divided by voltage divider capacitor C3. Most of the AC voltage falls on voltage divider capacitor C3, and a small part of the AC voltage is shaped into DC voltage through rectifier bridge D1, and then connected to the output voltage Vout through filter capacitor C4 and filter capacitor C5.

[0026] When the input power supply is 24V DC, after being protected by capacitor C1, surge protection varistor RP, and lightning protection gas discharge tube DT, the current flows through fuse F and current limiting resistor R1, flows into common mode inductor L for filtering, and then flows into switching diode D2 and resistors R3 and R4, turning on field effect tube Q1, and field effect tube Q1 outputs voltage Vout. When Vout passes through sampling resistor R6 and resistor R7 for voltage sampling, the sampling voltage V2 is input to the reverse input terminal of operational amplifier UA. Vout passes through voltage zener diode D5, and the reference voltage V1 provided by voltage zener diode D5 is input to the forward input terminal of operational amplifier UA. Operational amplifier UA compares the input reference voltage V1 with the sampling voltage V2, and adjusts the conduction degree of field effect tube Q1 through transistor Q2 to keep the voltage of Vout stable. When the output voltage Vout increases, the sampling voltage V2 also increases, causing the difference between the sampling voltage V2 and the reference voltage V1 to become smaller. The output voltage of the operational amplifier is input to the base of the transistor Q2, and the transistor Q2 is turned on. Due to the action of the voltage-stabilizing diode D4, the collector voltage of the transistor Q2 decreases, thereby reducing the conduction degree of the field-effect transistor Q1, reducing the output voltage Vout, and thus the output voltage Vout remains stable.

Claims

1. An AC / DC dual-purpose power supply circuit with a wide input range, characterized in that: It includes a power protection circuit, a filter module, an AC bridge rectifier module and a DC series negative feedback voltage stabilization module; The filtering module is respectively connected to the power protection circuit, the DC series negative feedback voltage stabilization module and the AC bridge rectifier module, and the DC series negative feedback voltage stabilization module and the AC bridge rectifier module are connected to each other; The power protection circuit is used for circuit breaking protection, overload protection and overvoltage protection; The filtering module is used to filter the clutter in the input power supply; The AC bridge rectifier module is used to convert the input AC power into DC power; The DC series negative feedback voltage stabilization module is used to reduce and adjust the input DC power, and after being combined with the DC power output by the AC bridge rectifier module, a DC output stable voltage is obtained.

2. The AC / DC dual-purpose power supply circuit with a wide input range according to claim 1, characterized in that: The power protection circuit is composed of a capacitor C1, a varistor RP, a gas discharge tube DT, a fuse F and a current limiting resistor R1; the specific circuit connection is that the capacitor C1, the varistor RP, and the gas discharge tube DT are connected in parallel at both ends of the power supply in sequence, one end of the fuse F is connected to the capacitor C1, the varistor RP, and the end of the gas discharge tube DT connected to the positive electrode of the power supply, and the other end of the fuse F is connected in series with one end of the current limiting resistor R.

3. The AC / DC dual-purpose power supply circuit with a wide input range according to claim 1, characterized in that: The filtering module is composed of a discharge resistor R2, a capacitor C2, and an inductor L; the specific circuit connection is that one end of the discharge resistor R2 is respectively connected to the 2nd foot of the inductor L and the other end of the current limiting resistor R1, the other end of the discharge resistor R2 is respectively connected to the 1st foot of the inductor L and the negative pole of the power terminal, and the two ends of the capacitor C2 are respectively connected to the 3rd foot and the 4th foot of the inductor L.

4. The AC / DC dual-purpose power supply circuit with a wide input range according to claim 1, characterized in that: The AC bridge rectifier module is composed of a voltage-dividing capacitor C3, a rectifier bridge D1, a filter capacitor C4 and a filter capacitor C5; the specific circuit connection is that one end of the voltage-dividing capacitor C3 is connected to the 3rd pin of the inductor L, and the other end is connected to the 3rd pin of the rectifier bridge D1, the 2nd pin of the rectifier bridge D1 is grounded, the 4th pin is connected to the 4th pin of the inductor L, and the 1st pin is respectively connected to the positive end of the filter capacitor C4 and the filter capacitor C5, and the negative end of the filter capacitor C4 and the filter capacitor C5 are respectively grounded.

5. The AC / DC dual-purpose power supply circuit with a wide input range according to claim 1, characterized in that: The DC series negative feedback voltage stabilization module is composed of a voltage stabilizing diode D5, a resistor R8, a sampling resistor R6, a resistor R7, a capacitor C6, a capacitor C7, an operational amplifier UA, a voltage stabilizing diode D4, a transistor Q2, a diode D3, a field effect transistor Q1, a switching diode D2, a current limiting resistor R5, a resistor R4 and a resistor R3; the specific circuit connection is that the positive electrode of the voltage stabilizing diode D5 is respectively connected to pin 3 of the forward input end of the operational amplifier UA and one end of the resistor R8, the negative electrode of the voltage stabilizing diode D5 is connected to the output Vout, and the other end of the resistor R8 is grounded; one end of the sampling resistor R6 is connected to the output Vout, and the other end of the sampling resistor R6 is respectively connected to pin 2 of the reverse input end of the operational amplifier UA and one end of the resistor R7, and the other end of the resistor R7 is grounded; the positive electrode of the power supply of the operational amplifier UA is connected to the output Vout and one end of the capacitor C6, and the operational amplifier The negative electrode of the power supply of UA and the other end of the capacitor C6 are grounded, one end of the capacitor C7 is connected to the output terminal 1 of the operational amplifier UA, and the other end of the capacitor C7 is connected to the reverse input terminal 2 of the operational amplifier UA; the positive electrode of the switching diode D2 is connected to one end of the resistor R3, the negative electrode of the switching diode D2 is connected to the drain (D) of the field effect transistor Q1, the source (S) of the field effect transistor Q1 is connected to one end of the current limiting resistor R5, the gate (G) of the field effect transistor Q1 is connected to one end of the resistor R4, and the other end of the current limiting resistor R5 is respectively connected to the positive electrode of the diode D3 and the output Vout; the other end of the resistor R4 is respectively connected to the other end of the resistor R3, the negative electrode of the diode D3 and the collector of the transistor Q2; the emitter of the transistor Q2 is connected to the negative electrode of the voltage-stabilizing diode D4, and the positive electrode of the voltage-stabilizing diode D4 is grounded; the base of the transistor Q2 is connected to the output terminal 1 of the operational amplifier UA.

6. The AC / DC dual-purpose power supply circuit with a wide input range according to claim 1, characterized in that: The DC series negative feedback voltage stabilization module is composed of a reference circuit, a sampling circuit, a comparison circuit, and an adjustment circuit; the reference circuit includes a voltage stabilizing diode D5 and a resistor R8, which are used to provide a reference voltage; the sampling circuit includes a sampling resistor R6 and a resistor R7, which are used to obtain a sampling voltage; the comparison circuit includes a capacitor C6, a capacitor C7 and an operational amplifier UA, which are used to compare the reference voltage and the sampling voltage; the adjustment circuit includes a voltage stabilizing diode D4, a transistor Q2, a diode D3, a field effect transistor Q1, a switching diode D2, a current limiting resistor R5, a resistor R4 and a resistor R3, which are used to adjust the conduction degree of the field effect transistor Q1 according to the comparison result to keep the output voltage stable.

Images