阅读说明：本技术 可变交流电压转恒压直流电压的保护电路 (Protection circuit for converting variable alternating current voltage into constant voltage direct current voltage ) 是由 王萌 张妹雄 欧家茂 于 2021-11-09 设计创作，主要内容包括：本发明公开可变交流电压转低压恒压直流电压的保护电路,涉及电压转换电路相关技术领域,包括整流电路,对输入的交流电压进行整流；所述整流电路连接用于电压采样的分压电阻,经过整流的电压通过分压电阻进行分压；分压电阻连接电压比较器,电压比较器的输出端连接光耦控制器,光耦控制器的输出端通过可控硅连接滤波电容,光耦控制器导通使可控硅触发给滤波电容充电,从而控制滤波电压在一定范围内。对交流电整流后,通过电压取样截取馒头波低压部分来控制可控硅对滤波电容的充电达到控制直流电压,整流滤波电容和MOS管都可以选择更低耐压值,因此成本更低,适用范围更广且有利于推广,能够滤除较高的交流峰值电压部分。(The invention discloses a protection circuit for converting variable alternating voltage into low-voltage constant-voltage direct voltage, which relates to the related technical field of voltage conversion circuits and comprises a rectifying circuit, a voltage stabilizing circuit and a voltage stabilizing circuit, wherein the rectifying circuit is used for rectifying the input alternating voltage; the rectifying circuit is connected with a voltage dividing resistor for voltage sampling, and the rectified voltage is divided by the voltage dividing resistor; the voltage divider resistor is connected with the voltage comparator, the output end of the voltage comparator is connected with the optical coupler controller, the output end of the optical coupler controller is connected with the filter capacitor through the silicon controlled rectifier, and the optical coupler controller is switched on to trigger the silicon controlled rectifier to charge the filter capacitor, so that the filter voltage is controlled within a certain range. After alternating current is rectified, the thyristor is controlled to charge the filter capacitor by sampling voltage and intercepting a low-voltage part of a voltage wave to control direct-current voltage, and the rectifier filter capacitor and the MOS tube can both select a lower withstand voltage value, so that the cost is lower, the application range is wider, the popularization is facilitated, and a higher alternating-current peak voltage part can be filtered.)

1. The protection circuit for converting variable alternating voltage into low-voltage constant-voltage direct voltage is characterized by comprising a rectifying circuit, a voltage stabilizing circuit and a voltage stabilizing circuit, wherein the rectifying circuit is used for rectifying the input alternating voltage; the rectifying circuit is connected with a voltage dividing resistor for voltage sampling, and the rectified voltage is divided by the voltage dividing resistor; the voltage divider resistor is connected with the voltage comparator, the output end of the voltage comparator is connected with the optical coupler controller, the output end of the optical coupler controller is connected with the filter capacitor through the silicon controlled rectifier, and the optical coupler controller is switched on to trigger the silicon controlled rectifier to charge the filter capacitor, so that the filter voltage is controlled within a certain range.

2. The protection circuit for converting a variable alternating current voltage into a low-voltage constant-voltage direct current voltage as claimed in claim 1, comprising a rectification circuit I consisting of four rectification diodes D11, signal sampling voltage-dividing resistors R11 and R12, a high-voltage side power supply current-limiting resistor R13, an IC comparator circuit I, a one-way silicon controlled rectifier SCR11, a driving resistor R14, a driving anti-reverse diode D12, an optical coupler MOC3023 and a filter capacitor C12;

the signal sampling voltage-dividing resistors R11 and R12 are connected in series, the first end of the IC comparator circuit I is connected between the signal sampling voltage-dividing resistors R11 and R12, the second end of the IC comparator circuit I is connected with the high-voltage-side power supply current-limiting resistor R13, the third end of the IC comparator circuit I is connected with the rectifying circuit I, and the fourth end of the IC comparator circuit I is connected with the optical coupler I MOC 3023;

the first end of the driving resistor R14 is connected with the optical coupler MOC3023 through a one-way thyristor SCR11, and the second end of the driving resistor R14 is connected with the optical coupler MOC3023 through a driving anti-reverse diode D12.

3. The protection circuit for converting a variable alternating current voltage into a low-voltage constant-voltage direct current voltage as claimed in claim 1, comprising a second rectification circuit consisting of four rectifier diodes D21, an overvoltage detection tube TVS21, a current-limiting resistor R21, a voltage regulator tube TVS22, a current-limiting resistor R26, a pull-down resistor R22, a NOR gate chip II IC, an optical coupler II MOC3023, a pull-down resistor R25, a one-way silicon controlled rectifier II SCR21, a driving resistor R24, a driving anti-reverse diode D22, a filter capacitor C21, a filter resistor R23, a voltage regulator tube TVS23, a current-limiting resistor R27, a filter capacitor C22 and a filter capacitor C23;

the positive pole of the overvoltage detection tube TVS21 is connected with the current-limiting resistor R21, the positive pole of the voltage-stabilizing tube TVS22 is connected with the current-limiting resistor R21, and the negative pole is connected with the positive pole of the overvoltage detection tube TVS21 through the current-limiting resistor R26; one end of the pull-down resistor R22 is connected with the negative electrode of the voltage regulator tube TVS22, and the other end of the pull-down resistor R22 is connected with the positive electrode of the voltage regulator tube TVS 22;

one input end of the NOR gate chip II IC is connected with the negative electrode of the voltage regulator tube TVS22, the other input end of the NOR gate chip II IC is connected with the positive electrode of the voltage regulator tube TVS22, and the output end of the NOR gate chip II IC is connected with the optocoupler two MOC 3023;

the filter resistor R23 and the filter capacitor C21 are connected in series and then connected in parallel with the positive electrode and the negative electrode of the unidirectional silicon controlled rectifier SCR 21; the first end of the driving resistor R24 is connected with the anode of a one-way thyristor secondary SCR21, and the second end of the driving resistor R24 is connected with an optocoupler secondary MOC3023 through a driving anti-reverse diode D22; the negative electrode of the unidirectional silicon controlled rectifier II SCR21 is connected with an optocoupler II MOC 3023;

one end of the current-limiting resistor R27 is connected with the second rectifying circuit, the other end of the current-limiting resistor R27 is connected with the negative electrode of the voltage-regulator tube TVS23, the positive electrode of the voltage-regulator tube TVS23 is connected with the first end of the filter capacitor C22, and the second end of the filter capacitor C22 is connected with the NOR gate chip II IC.

4. The protection circuit for converting a variable alternating current voltage into a low-voltage constant-voltage direct current voltage as claimed in claim 1, comprising a rectifying circuit III consisting of four rectifying diodes D31, a signal sampling voltage-dividing resistor R31, a signal sampling voltage-dividing resistor R32, a high-voltage side power supply current-limiting resistor R36, a filter capacitor C32, an IC comparator III LM393, a voltage regulator TVS31, an optical coupling current-limiting resistor R37, an optical coupling switch three MOSFET, a MOSFET driving resistor R38, a comparator output pull-up resistor R35, a unidirectional silicon controlled rectifier SCR31, a driving resistor R34, a driving anti-reverse diode D32, an optical coupling three MOC3023, a filter capacitor C31, a filter resistor R33 and a filter capacitor C33;

the signal sampling voltage-dividing resistors R31 and R32 are connected in series and then connected in parallel at two ends of a third rectifying circuit, the filter resistor R33 and the filter capacitor C31 are connected in series and then connected in parallel at two ends of a unidirectional silicon controlled rectifier SCR31, the first end of the driving resistor R34 is connected with the anode of the unidirectional silicon controlled rectifier SCR31, and the second end of the driving resistor R34 is connected with a triple MOC3023 optocoupler through a driving anti-reverse diode D32; the comparator output pull-up resistor R35 is connected in parallel with a pin1 interface and a pin8 interface of the IC comparator tri LM 393; one end of a high-voltage side power supply current limiting resistor R36 is connected with the anode of a one-way thyristor SCR31, and the other end of the high-voltage side power supply current limiting resistor R36 is connected with a filter capacitor C32; one end of the optocoupler current limiting resistor R37 is connected with the optocoupler three MOC3023, and the other end of the optocoupler current limiting resistor R37 is connected with the cathode of the voltage regulator tube TVS 31; one end of the MOSFET driving resistor R38 is connected with a pin1 interface of the IC comparator three LM393, and the other end of the MOSFET driving resistor R38 is connected with the optocoupler switch three MOSFET.

5. The protection circuit for converting a variable alternating current voltage into a low-voltage constant-voltage direct current voltage as claimed in claim 1, comprising a rectifier circuit IV consisting of four rectifier diodes D41, a signal sampling divider resistor R41, R42, a high-voltage side power supply current limiting resistor R45, a filter capacitor C42, an integrated comparator IV IC, an optical coupling current limiting resistor R46, a unidirectional silicon controlled rectifier IV SCR41, a driving resistor R44, a driving anti-reverse diode D42, an optical coupling IV MOC3023, a filter capacitor C41, a filter resistor R43, a transformer secondary winding power supply guide diode D43, a current limiting resistor R47 and a filter capacitor C43;

the signal sampling voltage-dividing resistors R41 and R42 are connected in parallel and then are connected in series at two ends of the rectifying circuit IV; the filter resistor R43 and the filter capacitor C41 are connected in series and then connected in parallel at two ends of the unidirectional silicon controlled rectifier four SCR 41; the first end of the driving resistor R44 is connected with the anode of a one-way thyristor four SCR41, and the second end of the driving resistor R44 is connected with an optocoupler four MOC3023 through a driving anti-reverse diode D42; one end of a high-voltage side power supply current limiting resistor R45 is connected with the positive electrode of a one-way Silicon Controlled Rectifier (SCR) 41, and the other end of the high-voltage side power supply current limiting resistor R45 is connected with a filter capacitor C42; the optocoupler current limiting resistor R46 is connected with an optocoupler four MOC 3023; the current limiting resistor R47 is connected with the integrated four-IC through a transformer secondary winding power supply guide diode D43.

Technical Field

The invention relates to the technical field of voltage conversion circuits, in particular to a protection circuit for converting variable alternating-current voltage into constant low-voltage direct-current voltage.

Background

Alternating current power supply lines vary in voltage standard around the world, and the fluctuation ranges of the same voltage standard vary from place to place. For example, indian ac grid voltage fluctuation may range from 190V to 380V; the input voltage range of a normal power supply design is generally 100V to 277V, which brings many challenges to many power supply designs, and the power supply failure rate is even higher.

Among them, surge MOV, rectifier filter capacitor and switch MOS transistor failure rate are the most common. In order to solve the problem in the prior art, the withstand voltage of the MOV rectifier filter capacitor and the MOS transistor has to be raised by a height, so that the cost pressure caused by the rise is obviously huge, and the popularization and the use of the MOV rectifier filter capacitor and the MOS transistor are difficult. Therefore, the variable alternating voltage to constant low-voltage direct voltage protection circuit is particularly provided, the cost is lower, the application range is wider, the popularization is facilitated, the higher alternating peak voltage part can be filtered, the short-time high-voltage fluctuation protection is particularly realized on an alternating current power grid, and meanwhile, the variable alternating voltage to constant low-voltage direct voltage protection circuit is compatible with alternating voltage low-voltage fluctuation.

Disclosure of Invention

The present invention is directed to a protection circuit for converting a variable ac voltage into a constant dc voltage, so as to solve the above-mentioned problems in the prior art.

In order to achieve the purpose, the invention provides the following technical scheme: the rectifier circuit is used for rectifying the input alternating voltage; the rectifying circuit is connected with a voltage dividing resistor for voltage sampling, and the rectified voltage is divided by the voltage dividing resistor; the voltage divider resistor is connected with the voltage comparator, the output end of the voltage comparator is connected with the optical coupler controller, the output end of the optical coupler controller is connected with the filter capacitor through the silicon controlled rectifier, and the optical coupler controller is switched on to trigger the silicon controlled rectifier to charge the filter capacitor, so that the filter voltage is controlled within a certain range.

Preferably, the circuit comprises a rectifying circuit I consisting of four rectifying diodes D11, signal sampling voltage dividing resistors R11 and R12, a high-voltage side power supply current limiting resistor R13, an IC comparator circuit I, a unidirectional silicon controlled rectifier SCR11, a driving resistor R14, a driving anti-reverse diode D12, an optical coupler MOC3023 and a filter capacitor C12;

the signal sampling voltage-dividing resistors R11 and R12 are connected in series, the first end of the IC comparator circuit I is connected between the signal sampling voltage-dividing resistors R11 and R12, the second end of the IC comparator circuit I is connected with the high-voltage-side power supply current-limiting resistor R13, the third end of the IC comparator circuit I is connected with the rectifying circuit I, and the fourth end of the IC comparator circuit I is connected with the optical coupler I MOC 3023;

the first end of the driving resistor R14 is connected with the optical coupler MOC3023 through a one-way thyristor SCR11, and the second end of the driving resistor R14 is connected with the optical coupler MOC3023 through a driving anti-reverse diode D12.

Preferably, the overvoltage detection circuit comprises a second rectifying circuit consisting of four rectifying diodes D21, an overvoltage detection tube TVS21, a current-limiting resistor R21, a voltage-regulator tube TVS22, a current-limiting resistor R26, a pull-down resistor R22, a NOR gate chip II IC, a light-coupled diode MOC3023, a pull-down resistor R25, a one-way Silicon Controlled Rectifier (SCR) 21, a driving resistor R24, a driving anti-reverse diode D22, a filter capacitor C21, a filter resistor R23, a voltage-regulator tube TVS23, a current-limiting resistor R27, a filter capacitor C22 and a filter capacitor C23;

the positive pole of the overvoltage detection tube TVS21 is connected with the current-limiting resistor R21, the positive pole of the voltage-stabilizing tube TVS22 is connected with the current-limiting resistor R21, and the negative pole is connected with the positive pole of the overvoltage detection tube TVS21 through the current-limiting resistor R26; one end of the pull-down resistor R22 is connected with the negative electrode of the voltage regulator tube TVS22, and the other end of the pull-down resistor R22 is connected with the positive electrode of the voltage regulator tube TVS 22;

one input end of the NOR gate chip II IC is connected with the negative electrode of the voltage regulator tube TVS22, the other input end of the NOR gate chip II IC is connected with the positive electrode of the voltage regulator tube TVS22, and the output end of the NOR gate chip II IC is connected with the optocoupler two MOC 3023;

the filter resistor R23 and the filter capacitor C21 are connected in series and then connected in parallel with the positive electrode and the negative electrode of the unidirectional silicon controlled rectifier SCR 21; the first end of the driving resistor R24 is connected with the anode of a one-way thyristor secondary SCR21, and the second end of the driving resistor R24 is connected with an optocoupler secondary MOC3023 through a driving anti-reverse diode D22; the negative electrode of the unidirectional silicon controlled rectifier II SCR21 is connected with an optocoupler II MOC 3023;

one end of the current-limiting resistor R27 is connected with the second rectifying circuit, the other end of the current-limiting resistor R27 is connected with the negative electrode of the voltage-regulator tube TVS23, the positive electrode of the voltage-regulator tube TVS23 is connected with the first end of the filter capacitor C22, and the second end of the filter capacitor C22 is connected with the NOR gate chip II IC.

Preferably, the circuit comprises a rectifying circuit III consisting of four rectifying diodes D31, a signal sampling voltage-dividing resistor R31, a signal 32, a high-voltage side power supply current-limiting resistor R36, a filter capacitor C32, an IC comparator three LM393, a voltage regulator TVS31, an optical coupling current-limiting resistor R37, an optical coupling switch three MOSFET, a MOSFET driving resistor R38, a comparator output pull-up resistor R35, a unidirectional silicon controlled rectifier SCR31, a driving resistor R34, a driving anti-reverse diode D32, an optical coupling three MOC3023, a filter capacitor C31, a filter resistor R33 and a filter capacitor C33;

the signal sampling voltage-dividing resistors R31 and R32 are connected in series and then connected in parallel at two ends of a third rectifying circuit, the filter resistor R33 and the filter capacitor C31 are connected in series and then connected in parallel at two ends of a unidirectional silicon controlled rectifier SCR31, the first end of the driving resistor R34 is connected with the anode of the unidirectional silicon controlled rectifier SCR31, and the second end of the driving resistor R34 is connected with a triple MOC3023 optocoupler through a driving anti-reverse diode D32; the comparator output pull-up resistor R35 is connected in parallel with a pin1 interface and a pin8 interface of the IC comparator tri LM 393; one end of a high-voltage side power supply current limiting resistor R36 is connected with the anode of a one-way thyristor SCR31, and the other end of the high-voltage side power supply current limiting resistor R36 is connected with a filter capacitor C32; one end of the optocoupler current limiting resistor R37 is connected with the optocoupler three MOC3023, and the other end of the optocoupler current limiting resistor R37 is connected with the cathode of the voltage regulator tube TVS 31; one end of the MOSFET driving resistor R38 is connected with a pin1 interface of the IC comparator three LM393, and the other end of the MOSFET driving resistor R38 is connected with the optocoupler switch three MOSFET.

Preferably, the system comprises a rectifying circuit IV consisting of four rectifying diodes D41, a signal sampling voltage-dividing resistor R41, a signal 42, a high-voltage side power supply current-limiting resistor R45, a filter capacitor C42, an integrated comparator IV, an optical coupling current-limiting resistor R46, a unidirectional silicon controlled rectifier IV SCR41, a driving resistor R44, a driving anti-reverse diode D42, an optical coupling IV MOC3023, a filter capacitor C41, a filter resistor R43, a transformer secondary winding power supply guide diode D43, a current-limiting resistor R47 and a filter capacitor C43;

the signal sampling voltage-dividing resistors R41 and R42 are connected in parallel and then are connected in series at two ends of the rectifying circuit IV; the filter resistor R43 and the filter capacitor C41 are connected in series and then connected in parallel at two ends of the unidirectional silicon controlled rectifier four SCR 41; the first end of the driving resistor R44 is connected with the anode of a one-way thyristor four SCR41, and the second end of the driving resistor R44 is connected with an optocoupler four MOC3023 through a driving anti-reverse diode D42; one end of a high-voltage side power supply current limiting resistor R45 is connected with the positive electrode of a one-way Silicon Controlled Rectifier (SCR) 41, and the other end of the high-voltage side power supply current limiting resistor R45 is connected with a filter capacitor C42; the optocoupler current limiting resistor R46 is connected with an optocoupler four MOC 3023; the current limiting resistor R47 is connected with the integrated four-IC through a transformer secondary winding power supply guide diode D43.

Compared with the prior art, the invention has the beneficial effects that: through rectifying AC voltage in advance, later utilize control circuit control voltage to charge to filter capacitor and realize the control to voltage to directly not adopting the great high-pressure filter capacitor of cost pressure and high-pressure MOS pipe, consequently the cost is lower, and application scope is wider and be favorable to promoting, can filter higher AC peak voltage part, especially to the high fluctuation protection of AC electric network short-time, simultaneously can compatible AC voltage low pressure fluctuation.

Drawings

FIG. 1 is a schematic circuit diagram of embodiment 1 of the present invention;

fig. 2 is a schematic diagram of a non-gate dam type bleeder power supply circuit according to embodiment 2 of the present invention;

fig. 3 is a schematic diagram of a topological dam-type bleeder power supply circuit of a power comparator control circuit according to embodiment 3 of the present invention;

fig. 4 is a schematic diagram of a circuit topology integrated optimization circuit according to embodiment 4 of the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Example 1

Referring to fig. 1, the first embodiment provides a protection circuit for converting a variable ac voltage into a low-voltage constant-voltage dc voltage, which includes a rectifier circuit i composed of four rectifier diodes D11, signal sampling voltage-dividing resistors R11 and R12, a high-voltage side power supply current-limiting resistor R13, an IC comparator circuit i, a one-way thyristor SCR11, a driving resistor R14, a driving anti-reverse diode D12, an optocoupler MOC3023, and a filter capacitor C12; the signal sampling voltage-dividing resistors R11 and R12 are connected in series, the first end of the IC comparator circuit I is connected between the signal sampling voltage-dividing resistors R11 and R12, the second end of the IC comparator circuit I is connected with the high-voltage-side power supply current-limiting resistor R13, the third end of the IC comparator circuit I is connected with the rectifying circuit I, and the fourth end of the IC comparator circuit I is connected with the optical coupler I MOC 3023; the first end of the driving resistor R14 is connected with the optical coupler MOC3023 through a one-way thyristor SCR11, and the second end of the driving resistor R14 is connected with the optical coupler MOC3023 through a driving anti-reverse diode D12.

Alternating voltage forms steamed bread waves after passing through the rectifying circuit I, voltage sampling signals are input after being divided by the signal sampling voltage dividing resistors R11 and R12, and compared with the voltage of the IC comparator circuit I (the setting of the signal sampling voltage dividing resistors needs to be determined according to the direct current voltage requirement and the reference voltage of the IC comparator circuit I), the voltage of the steamed bread waves is reduced to a set voltage to trigger a high-level signal output by the IC comparator circuit I to control the conduction of the optical coupler MOC3023, so that the unidirectional silicon controlled rectifier SCR11 is triggered to charge the filter capacitor C12, and the filter voltage is controlled within a certain low-voltage range. The voltage resistance of the one-way thyristor SCR11 and the optical coupler-MOC 3023 depends on the maximum value of the input alternating voltage.

Example 2

Referring to fig. 2, a protection circuit for converting a variable ac voltage into a low-voltage constant-voltage dc voltage is provided in the second embodiment, and includes a second rectifier circuit composed of four rectifier diodes D21, an overvoltage detection transistor TVS21, a current-limiting resistor R21, a voltage regulator TVS22, a current-limiting resistor R26, a pull-down resistor R22, a nor chip two IC, a second opto-coupler MOC3023, a pull-down resistor R25, a second unidirectional silicon controlled rectifier SCR21, a driving resistor R24, a driving anti-reverse diode D22, a filter capacitor C21, a filter resistor R23, a voltage regulator TVS23, a current-limiting resistor R27, a filter capacitor C22, and a C23; the positive pole of the overvoltage detection tube TVS21 is connected with the current-limiting resistor R21, the positive pole of the voltage-stabilizing tube TVS22 is connected with the current-limiting resistor R21, and the negative pole is connected with the positive pole of the overvoltage detection tube TVS21 through the current-limiting resistor R26; one end of the pull-down resistor R22 is connected with the negative electrode of the voltage regulator tube TVS22, and the other end of the pull-down resistor R22 is connected with the positive electrode of the voltage regulator tube TVS 22;

one input end of the NOR gate chip II IC is connected with the negative electrode of the voltage regulator tube TVS22, the other input end of the NOR gate chip II IC is connected with the positive electrode of the voltage regulator tube TVS22, and the output end of the NOR gate chip II IC is connected with the optocoupler two MOC 3023;

the filter resistor R23 and the filter capacitor C21 are connected in series and then connected in parallel with the positive electrode and the negative electrode of the unidirectional silicon controlled rectifier SCR 21; the first end of the driving resistor R24 is connected with the anode of a one-way thyristor secondary SCR21, and the second end of the driving resistor R24 is connected with an optocoupler secondary MOC3023 through a driving anti-reverse diode D22; the negative electrode of the unidirectional silicon controlled rectifier II SCR21 is connected with an optocoupler II MOC 3023;

one end of the current-limiting resistor R27 is connected with the second rectifying circuit, the other end of the current-limiting resistor R27 is connected with the negative electrode of the voltage-regulator tube TVS23, the positive electrode of the voltage-regulator tube TVS23 is connected with the first end of the filter capacitor C22, and the second end of the filter capacitor C22 is connected with the NOR gate chip II IC.

Alternating voltage forms steamed bread waves after passing through the second rectifying circuit, the overvoltage detection tube TVS21 determines a voltage sampling point, a signal exceeding the voltage of the overvoltage detection tube TVS21 is stabilized into a low-level signal by the voltage stabilizing tube TVS22 and is controlled by an NOR gate circuit formed by the NOR gate chip II IC, and the NOR gate chip II IC outputs a high-level control output signal of the two-MOC 3023 optocoupler to trigger the conduction of the one-way silicon controlled rectifier SCR21 to charge the filter capacitor C23 only in a section where the voltage of the alternating current side is lower than the voltage of the overvoltage detection tube TVS21 at each time, so that the filter voltage is controlled within a certain low-voltage range. The withstand voltage of the one-way thyristor SCR21 and the optocoupler two MOC3023 depends on the maximum value of the input alternating current voltage.

Example 3

Referring to fig. 3, a protection circuit for converting a variable ac voltage into a low-voltage constant-voltage dc voltage is provided in the third embodiment, and includes a third rectifier circuit composed of four rectifier diodes D31, a signal sampling voltage-dividing resistor R31, a R32, a high-voltage side power supply current-limiting resistor R36, a filter capacitor C32, an IC comparator three LM393, a voltage regulator TVS31, an optocoupler current-limiting resistor R37, an optocoupler switch three MOSFET, a MOSFET driving resistor R38, a comparator output pull-up resistor R35, a unidirectional silicon controlled SCR31, a driving resistor R34, a driving anti-reflection diode D32, an optocoupler three MOC3023, a filter capacitor C31, a filter resistor R33, and a filter capacitor C33; the signal sampling voltage-dividing resistors R31 and R32 are connected in series and then connected in parallel at two ends of a third rectifying circuit, the filter resistor R33 and the filter capacitor C31 are connected in series and then connected in parallel at two ends of a unidirectional silicon controlled rectifier SCR31, the first end of the driving resistor R34 is connected with the anode of the unidirectional silicon controlled rectifier SCR31, and the second end of the driving resistor R34 is connected with a triple MOC3023 optocoupler through a driving anti-reverse diode D32; the comparator output pull-up resistor R35 is connected in parallel with a pin1 interface and a pin8 interface of the IC comparator tri LM 393; one end of a high-voltage side power supply current limiting resistor R36 is connected with the anode of a one-way thyristor SCR31, and the other end of the high-voltage side power supply current limiting resistor R36 is connected with a filter capacitor C32; one end of the optocoupler current limiting resistor R37 is connected with the optocoupler three MOC3023, and the other end of the optocoupler current limiting resistor R37 is connected with the cathode of the voltage regulator tube TVS 31; one end of the MOSFET driving resistor R38 is connected with a pin1 interface of the IC comparator three LM393, and the other end of the MOSFET driving resistor R38 is connected with the optocoupler switch three MOSFET.

Alternating voltage forms steamed bread waves after passing through the third rectifying circuit, voltage sampling signals are divided by the signal sampling voltage dividing resistors R31 and R32 and then input into the three LM393 of the IC comparator, and the voltage is compared with the three LM393 of the IC comparator (reference voltage is determined by the power supply voltage of the three LM393 of the IC comparator), so that the voltage of the steamed bread waves is reduced to a set voltage to trigger the output high level signal of the three LM393 of the IC comparator to control the three MOSFETs of the optical coupler to be conducted to enable the three MOC3023 of the optical coupler to be conducted, the one-way silicon controlled SCR31 is triggered to charge the filter capacitor C33, and the filter voltage is controlled within a certain low voltage range. The voltage resistance of the one-way thyristor SCR31 and the optocoupler three MOC3023 depends on the maximum value of the input alternating current voltage.

Example 4

Referring to fig. 4, a protection circuit for converting a variable ac voltage into a low-voltage constant-voltage dc voltage is provided in the fourth embodiment, and includes a rectifier circuit four formed by four rectifier diodes D41, a signal sampling voltage-dividing resistor R41, a signal sampling voltage-dividing resistor R42, a high-voltage side power supply current-limiting resistor R45, a filter capacitor C42, an integrated comparator four IC, an optical coupling current-limiting resistor R46, a unidirectional silicon controlled rectifier four SCR41, a driving resistor R44, a driving anti-reverse diode D42, an optical coupling four MOC3023, a filter capacitor C41, a filter resistor R43, a transformer secondary winding power supply guide diode D43, a current-limiting resistor R47, and a filter capacitor C43; the signal sampling voltage-dividing resistors R41 and R42 are connected in parallel and then are connected in series at two ends of the rectifying circuit IV; the filter resistor R43 and the filter capacitor C41 are connected in series and then connected in parallel at two ends of the unidirectional silicon controlled rectifier four SCR 41; the first end of the driving resistor R44 is connected with the anode of a one-way thyristor four SCR41, and the second end of the driving resistor R44 is connected with an optocoupler four MOC3023 through a driving anti-reverse diode D42; one end of a high-voltage side power supply current limiting resistor R45 is connected with the positive electrode of a one-way Silicon Controlled Rectifier (SCR) 41, and the other end of the high-voltage side power supply current limiting resistor R45 is connected with a filter capacitor C42; the optocoupler current limiting resistor R46 is connected with an optocoupler four MOC 3023; the current limiting resistor R47 is connected with the integrated four-IC through a transformer secondary winding power supply guide diode D43.

The protection circuit for converting variable alternating-current voltage into low-voltage constant-voltage direct-current voltage in the fourth embodiment is similar to that in the third embodiment, and is different in that a comparator is integrated into an AC/DC controller, so that the topology is simpler, the cost is lower, and the performance is more stable. Alternating voltage forms steamed bread waves after passing through the rectifying circuit IV, voltage sampling signals are divided by the signal sampling voltage dividing resistors R41 and R42 and then input into a pin2 interface of the integrated comparator IV, the voltage is compared with the integrated comparator IV (reference voltage is determined by internal voltage of the integrated comparator IV), the steamed bread wave voltage is reduced to a set voltage to trigger the integrated comparator IV to output high-level signals to control the four MOC3023 of the optical coupler to be conducted, the unidirectional silicon controlled rectifier SCR41 is triggered to charge the filter capacitor C43, and therefore the filter voltage is controlled within a certain low-voltage range. The voltage resistance of the one-way silicon controlled rectifier SCR41 and the optocoupler four MOC3023 depends on the maximum value of the input alternating voltage.

Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.