CN213547366U - Circuit for effectively inhibiting EMI (electro-magnetic interference) of switching power supply - Google Patents
Circuit for effectively inhibiting EMI (electro-magnetic interference) of switching power supply Download PDFInfo
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- CN213547366U CN213547366U CN202022511384.7U CN202022511384U CN213547366U CN 213547366 U CN213547366 U CN 213547366U CN 202022511384 U CN202022511384 U CN 202022511384U CN 213547366 U CN213547366 U CN 213547366U
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Abstract
The utility model discloses an effectively restrain switching power supply EMI's circuit, this device includes: the transformer leakage inductance detection circuit comprises an alternating current input EMC circuit, a rectifying filter circuit, an A circuit, an output rectifying filter circuit, a C circuit, a transformer coupling driving circuit, a B circuit and a constant voltage circuit, wherein the peak voltage generated by transformer leakage inductance is absorbed by adopting the charging and discharging of a diode, a resistor and a capacitor of the A circuit; the MOS transistor, the diode, the resistor and the capacitor of the circuit B are combined to form a switch starting circuit, so that the voltage change rate when the switching tube is started and the loss when the switching tube is turned off are reduced; through adopting the charge and discharge of the resistor and the capacitor of the C circuit, the peak voltage generated when the diode in the output rectifying and filtering circuit recovers in the reverse direction is absorbed, and the EMI interference of the switching power supply can be effectively inhibited. The utility model relates to an effectively restrain switching power supply EMI's circuit can be applied to wide range and turn over the formula switching power supply to turn over.
Description
Technical Field
The utility model relates to a switching power supply field, concretely relates to effectively restrain switching power supply EMI's circuit.
Background
With the development of technology, electronic products become more and more mainstream products of technological development. In the field of electronic products, a switching power supply is praised as a high-efficiency energy-saving power supply, is a more ideal product under the modern advocation of green environmental protection, represents the development direction of a voltage-stabilized power supply, and has become a mainstream product of the voltage-stabilized power supply. However, the switching power supply is interfered by EMI, and the interference source is mainly and intensively embodied in a power switch device, a transformer and an output rectifier diode, wherein the power switch device enables the voltage change rate and the current change rate to be changed sharply under the influence of high-frequency switch cycle switching and parasitic capacitance of the power switch device, so that the EMI interference intensity is improved; due to the existence of leakage inductance, the high-frequency transformer can generate a very high peak voltage at the moment of switching off the switching power supply, and the peak voltage can affect the EMI (electro-magnetic interference) of the switching power supply; the output rectifying diode also generates a high spike voltage during reverse recovery, which also affects the EMI of the switching power supply. Therefore, in order to effectively suppress the EMI interference of the switching power supply, the utility model relates to a circuit for effectively suppressing the EMI of the switching power supply.
SUMMERY OF THE UTILITY MODEL
The utility model relates to a circuit for effectively inhibiting the EMI of a switching power supply, which absorbs the peak voltage generated by the leakage inductance of a transformer by adopting the charging and discharging of a diode, a resistor and a capacitor of a circuit A; the MOS transistor, the diode, the resistor and the capacitor of the circuit B are combined to form a switch starting circuit, so that the voltage change rate when the switching tube is started and the loss when the switching tube is turned off are reduced; through adopting the charge and discharge of the resistor and the capacitor of the C circuit, the peak voltage generated when the diode in the output rectifying and filtering circuit recovers in the reverse direction is absorbed, and the EMI interference of the switching power supply can be effectively inhibited.
The technical scheme of the utility model is specifically as follows:
a circuit for effectively suppressing EMI in a switching power supply, comprising: the circuit comprises an alternating current input EMC circuit, a rectifying and filtering circuit, an A circuit, an output rectifying and filtering circuit, a C circuit, a transformer coupling driving circuit, a B circuit and a constant voltage circuit.
The alternating current input EMC circuit further comprises a fuse F1, a voltage dependent resistor MOV1, a capacitor CX1, a parallel resistor R1/R1A, a parallel resistor R2/R2A, an inductor LF1 and a thermistor NTC1, wherein one end of the fuse F1 is connected with a live wire of a power input end, and the other end of the fuse F1 is connected with one end of the voltage dependent resistor MOV1, the positive electrode of the capacitor CX1, one end of the parallel resistor R1/R1A and one end of an input end of the inductor LF1 in parallel; one end of the thermistor NTC1 is connected with a zero line of a power input end, the other end of the thermistor NTC1 is connected with the other end of the varistor MOV1, the negative electrode of the capacitor CX1, one end of the parallel resistor R2/R2A and the other end of the input end of the inductor LF1 in parallel, wherein the other end of the parallel resistor R2/R2A is connected with the other end of the parallel resistor R1/R1A in common.
Further, the output end of the inductor LF1 is connected to the input end of a bridge rectifier of a rectifying and filtering circuit, and the rectifying and filtering circuit (2) includes a bridge rectifier and parallel capacitors EC1 and EC2, wherein one end of the output end of the bridge rectifier is connected to the positive terminals of the parallel capacitors EC1 and EC2, and the other end of the output end of the bridge rectifier is grounded to the negative terminals of the parallel capacitors EC1 and EC 2.
The positive terminals of the parallel capacitors EC1 and EC2 are connected with the positive terminals of a parallel resistor R4, a resistor R5 and a capacitor C1 in an A circuit and one end of the input end of a transformer TR1, the A circuit comprises a resistor R4, a resistor R5, a capacitor C1, a resistor R3 and a diode D1, wherein the parallel resistor R4, the resistor R5 and the negative electrode of the capacitor C1 are connected in series with a resistor R3, the other end of the resistor R3 is connected with the negative electrode of a diode D1, the positive terminal of the diode D1 is connected with the other end of the input end of the transformer TR1, and leakage inductance voltage generated by the transformer TR1 when the switch is turned off is absorbed through parallel connection of the resistor and the capacitor and unidirectional conductivity of the diode.
Further, the positive terminal of the circuit A is connected with at least one resistor and at least one capacitor in parallel.
According to the further arrangement, the anode of the diode D1 in the A circuit is connected with the source of a MOS transistor Q1 and the anode of a capacitor C6 of a B circuit in the transformer coupling driving circuit, the B circuit comprises a MOS transistor Q1, a capacitor C6, a diode D3, a resistor R13 and a resistor R12, wherein the cathode of the capacitor C6 is connected with the drain of a MOS transistor Q1, the gate of the MOS transistor Q1 is connected with the anode of a diode D3 and the resistor R13, the cathode of the diode D3 and the other end of the resistor R13 are connected with the resistor R12 in common, and EMI interference suppression and switching tube loss reduction are realized when the switch is switched off through the B circuit.
Further, the Q1 in the B circuit is a MOS transistor or a triode, the source terminal of the Q1 and the positive terminal of the capacitor C6 are connected with at least one resistor in common, and the other end of the resistor is connected with the common terminal of the input terminal of the transformer TR1 and the positive terminal of the diode D1; the source and drain terminals of the Q1 in the B circuit are connected in parallel with at least one capacitor or a series combination of a capacitor and a resistor.
Further, the transformer coupling driving circuit comprises a B circuit, a chip OB2281A, capacitors C2, C3 and EC5, resistors R6, R7, R8, R9, R10, R11 and R14, a diode D2, a photosensitive NPN transistor PH1/2 and an inductor Nf, wherein the '1' terminal of the chip OB2281A is grounded; the '2' terminal of the chip OB2281A is connected with the positive electrode of a capacitor C3 and the collector of the photosensitive NPN transistor PH1/2, and the negative electrode of the capacitor C3 and the emitter of the photosensitive NPN transistor PH1/2 are grounded in common; the "3" terminal of the chip OB2281A is connected to the OTP chip; the '4' terminal of the chip OB2281A is connected with the positive electrode of a capacitor C2 and one end of a resistor R11, the negative electrode of the capacitor C2 is grounded, the other end of the resistor R11 is connected with one end of a parallel resistor R6/R7/R8 and the drain of a MOS transistor Q1, and the other end of the parallel resistor R6/R7/R8 is grounded; the '5' terminal of the chip OB2281A is connected with one end of a resistor R10, one end of a resistor R14 and the anode of a capacitor EC5, the other end of the resistor R10 is connected with one end of a resistor R9, the other end of the resistor R9 is connected with the anode of a diode D1 in the circuit A, the other end of the resistor R14 is connected with the cathode of a diode D2, the anode of the diode D2 is connected with one end of an inductor Nf, and the other end of the inductor Nf is connected with the cathode of the capacitor EC5 in common ground; the "6" terminal of the chip OB2281A is connected to the other end of the resistor R12 in the B circuit.
Further, the output end of the transformer TR1 is connected with the anode of a parallel diode D9/D10 of an output rectifying and filtering circuit and one end of a parallel resistor R15/R16 of a C circuit, wherein the output rectifying and filtering circuit comprises a parallel diode D9/D10, a parallel resistor R15/R16, a capacitor C4 and a parallel capacitor EC3/EC4, the C circuit comprises a parallel resistor R15/R16 and a capacitor C4, the other end of the parallel resistor R15/R16 is connected with the anode of a capacitor C4, the cathode of the capacitor C4 is connected with the anode of a parallel capacitor EC3/EC4, one end of a resistor R21 and a resistor R20 of a constant voltage circuit, the cathode of a parallel diode D9/D10 and the anode of the output end, and the cathode of the parallel capacitor EC3/EC4 is connected with the other end of the output end of the transformer TR1 and the.
It is further provided that at least one of the resistors in the C circuit is connected in parallel, and the other end of the resistor is connected to the positive electrode of the capacitor C4.
Further, the negative electrode of the parallel capacitor EC3/EC4 in the output rectifying and filtering circuit is connected with the negative electrode of the capacitor CY2, the positive electrode of the capacitor CY2 is connected with the negative electrode of the capacitor CY1, and the positive electrode of the capacitor CY1 is connected with the positive electrode of the capacitor C1 in the A circuit.
The constant voltage circuit further comprises resistors R17, R18, R19, R20, R21 and R22, a capacitor C5, a photodiode PH1 and a voltage regulator tube Q2, wherein the other end of the resistor R21 is connected with the resistor R22 and the anode of the photodiode PH1, the other end of the resistor R22 and the cathode of the photodiode PH1 are connected with the resistor R17 and the '3' terminal of the voltage regulator tube Q2 in a sharing mode, the other end of the resistor R17 is connected with the anode of the capacitor C5, the cathode of the capacitor C5 is connected with the '1' terminal of the voltage regulator tube Q2 and one end of the parallel resistor R18/R19, one end of the parallel resistor R18/R19 is connected with the other end of the resistor R20, and the other end of the parallel resistor R18/R19 and the '2' terminal of the voltage regulator tube Q2 are grounded in a sharing mode.
Further, the circuit A, the circuit B and the circuit C can be widely applied to all flyback switching power supplies.
(III) advantageous effects
The utility model relates to a circuit for effectively inhibiting the EMI of a switching power supply, which absorbs the peak voltage generated by the leakage inductance of a transformer by adopting the charging and discharging of a diode, a resistor and a capacitor of a circuit A; the MOS transistor, the diode, the resistor and the capacitor of the circuit B are combined to form a switch starting circuit, so that the voltage change rate when the switching tube is started and the loss when the switching tube is turned off are reduced; through adopting the charge and discharge of the resistor and the capacitor of the C circuit, the peak voltage generated when the diode in the output rectifying and filtering circuit recovers in the reverse direction is absorbed, and the EMI interference of the switching power supply can be effectively inhibited.
Drawings
Fig. 1 is a schematic structural diagram of the circuit for effectively suppressing the EMI of the switching power supply of the present invention.
Reference numerals: 1. an AC input EMC circuit; 2. a rectification filter circuit; 3. an output rectifying filter circuit; 4. a transformer coupling drive circuit; 5. a constant voltage circuit.
Detailed Description
The technical solutions in the embodiments of the present invention will be described clearly and completely with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments in the present invention, all other embodiments obtained by a person skilled in the art without creative work belong to the protection scope of the present invention.
Referring to fig. 1, fig. 1 is a schematic structural diagram of a circuit for effectively suppressing the EMI of the switching power supply according to the present invention.
The utility model provides a pair of effectively restrain switching power supply EMI's circuit, include: the alternating current input EMC circuit 1, the rectifier filter circuit 2, the A circuit, the output rectifier filter circuit 3, the C circuit, the transformer coupling drive circuit 4, the B circuit and the constant voltage circuit 5, wherein the alternating current input EMC circuit 1 comprises a fuse F1, a piezoresistor MOV1, a capacitor CX1, a parallel resistor R1/R1A, a parallel resistor R2/R2A, an inductor LF1 and a thermistor NTC1, one end of the fuse F1 is connected with a live wire of a power input end, and the other end of the fuse F1 is connected with one end of the piezoresistor MOV1, the positive electrode of the capacitor CX1, one end of the parallel resistor R1/R1A and one end of the input end of the inductor LF1 in parallel; one end of the thermistor NTC1 is connected with a zero line of a power input end, the other end of the thermistor NTC1 is connected with the other end of the varistor MOV1, the negative electrode of the capacitor CX1, one end of the parallel resistor R2/R2A and the other end of the input end of the inductor LF1 in parallel, wherein the other end of the parallel resistor R2/R2A is connected with the other end of the parallel resistor R1/R1A in common; the output end of the inductor LF1 is connected with the bridge rectification input end of the rectification filter circuit 2, the rectification filter circuit 2 comprises bridge rectification and parallel capacitors EC1 and EC2, wherein one end of the output end of the bridge rectification is connected with the positive ends of the parallel capacitors EC1 and EC2, and the other end of the output end of the bridge rectification is grounded with the negative ends of the parallel capacitors EC1 and EC 2; the positive terminals of the parallel capacitors EC1 and EC2 are connected with the anodes of a parallel resistor R4, a resistor R5 and a capacitor C1 in an A circuit and one end of the input end of a transformer TR1, the A circuit comprises a resistor R4, a resistor R5, a capacitor C1, a resistor R3 and a diode D1, wherein the parallel resistor R4, the resistor R5 and the cathode of the capacitor C1 are connected with the resistor R3 in series, the other end of the resistor R3 is connected with the cathode of a diode D1, the anode of the diode D1 is connected with the other end of the input end of the transformer TR1, and the leakage inductance spike voltage generated by the transformer TR1 when the switch is turned off is absorbed through the parallel connection of the resistors and the capacitors and the unidirectional conductivity of the diode; an anode of a diode D1 in the a circuit is connected to a source of a MOS transistor Q1 of a B circuit in a transformer coupling driving circuit 4 and an anode of a capacitor C6, the B circuit includes a MOS transistor Q1, a capacitor C6, a diode D3, a resistor R13 and a resistor R12, wherein a cathode of the capacitor C6 is connected to a drain of a MOS transistor Q1, a gate of the MOS transistor Q1 is connected to an anode of a diode D3 and a resistor R13, a cathode of the diode D3 and the other end of the resistor R13 are connected in common to a resistor R12, and when the switch is turned off, the interference of EMI is suppressed and the loss of the switching tube is reduced by the B circuit, wherein the transformer coupling driving circuit 4 includes a B circuit, a diode OB22 2281A, capacitors C2, C3, EC5, resistors R6, R7, R8, R9, R10, R11 and R14, a diode D2, a photosensitive transistor PH1/2 and an inductor nbr 2281A "591" terminal of the NPN 591 is grounded chip "; the '2' terminal of the chip OB2281A is connected with the positive electrode of a capacitor C3 and the collector of the photosensitive NPN transistor PH1/2, and the negative electrode of the capacitor C3 and the emitter of the photosensitive NPN transistor PH1/2 are grounded in common; the "3" terminal of the chip OB2281A is connected to the OTP chip; the '4' terminal of the chip OB2281A is connected with the positive electrode of a capacitor C2 and one end of a resistor R11, the negative electrode of the capacitor C2 is grounded, the other end of the resistor R11 is connected with one end of a parallel resistor R6/R7/R8 and the drain of a MOS transistor Q1, and the other end of the parallel resistor R6/R7/R8 is grounded; the '5' terminal of the chip OB2281A is connected with one end of a resistor R10, one end of a resistor R14 and the anode of a capacitor EC5, the other end of the resistor R10 is connected with one end of a resistor R9, the other end of the resistor R9 is connected with the anode of a diode D1 in the circuit A, the other end of the resistor R14 is connected with the cathode of a diode D2, the anode of the diode D2 is connected with one end of an inductor Nf, and the other end of the inductor Nf is connected with the cathode of the capacitor EC5 in common ground; the "6" terminal of the chip OB2281A is connected to the other end of the resistor R12 in the B circuit; the output end of the transformer TR1 is connected with the anode of the parallel diode D9/D10 of the output rectifying and filtering circuit 3 and one end of the parallel resistor R15/R16 of the C circuit, wherein the output rectifying and filtering circuit 3 comprises the parallel diode D9/D10, the parallel resistor R10/R10, a capacitor C10 and a parallel capacitor EC 10/EC 10, the C circuit comprises the parallel resistor R10/R10 and the capacitor C10, the other end of the parallel resistor R10/R10 is connected with the anode of the capacitor C10, the cathode of the capacitor C10 is connected with the anode of the parallel capacitor EC 10/EC 10, one end of the resistor R10 and one end of the resistor R10 of the constant voltage circuit 5, the cathode of the parallel diode D10/D10 and the output end, the cathode of the parallel capacitor EC 10/EC 10 is connected with the other end of the output terminal of the transformer TR 10, and the cathode of the capacitor CY 10 of the parallel capacitor EC 10/EC 10 in the output rectifying and filtering, the positive electrode of the capacitor CY2 is connected with the negative electrode of the capacitor CY1, and the positive electrode of the capacitor CY1 is connected with the positive electrode of the capacitor C1 in the circuit A; the constant voltage circuit 5 comprises resistors R17, R18, R19, R20, R21 and R22, a capacitor C5, a photodiode PH1 and a voltage regulator tube Q2, wherein the other end of the resistor R21 is connected with the resistor R22 and the anode of the photodiode PH1, the other end of the resistor R22 is connected with the cathode of the photodiode PH1 in common with the resistor R17 and the 3 terminal of the voltage regulator tube Q2, the other end of the resistor R17 is connected with the anode of the capacitor C5, the cathode of the capacitor C5 is connected with the 1 terminal of the voltage regulator tube Q2 and one end of a parallel resistor R18/R19, one end of the parallel resistor R18/R19 is connected with the other end of the resistor R20, and the other end of the parallel resistor R18/R19 is connected with the 2 terminal of the voltage regulator tube Q2 in common ground.
The utility model discloses the theory of operation is implemented specifically: the alternating current power supply is input into the EMC circuit 1 and the rectifying and filtering circuit 2 through alternating current to realize direct current output, and peak voltage generated by leakage inductance of the transformer is absorbed by adding the circuit A. When the switch tube is turned off, a leakage inductance can not be transmitted to the secondary side of the transformer, so that a high peak voltage can be generated, a transmission channel can be provided for the leakage inductance by adding the circuit A, and when the switch tube is turned off, electric energy of the leakage inductance flows through the resistor R3 through the diode D1, and finally charges the capacitor C1; when the switch tube is conducted, the capacitor C1 discharges through the parallel resistor R4/R5, and the spike voltage generated by the leakage inductance is absorbed. The transformer TR1 is driven by the transformer coupling driving circuit 4, wherein a B circuit is added in the transformer coupling driving circuit 4, the B circuit can generate high dv/dt when a prefabricated switch tube is conducted, current can flow from a resistor R12 to a resistor R13 to charge a capacitor C6 of the switch tube when the switch tube is conducted due to the unidirectional conductivity of a diode D3, the resistance value of a resistor R13 is increased, the charging time of the capacitor C6 is prolonged, and the voltage change rate of the switch tube is relatively gentle, so that EMI interference is effectively inhibited; when the switch tube is turned off, the capacitor C6 can discharge through the diode D3 and the resistor R12 without passing through the resistor R13, so that the loss of the switch tube can be reduced. After the transformer TR1 is passed, a C circuit is added in the output rectifying and filtering circuit 3, and the peak voltage generated when the output rectifying diode D9/D10 is reversely recovered can be absorbed, thereby effectively inhibiting EMI interference.
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.
Claims (9)
1. A circuit for effectively suppressing EMI in a switching power supply, comprising: the circuit comprises an AC input EMC circuit (1), a rectifying and filtering circuit (2), an A circuit, an output rectifying and filtering circuit (3), a C circuit in the output rectifying and filtering circuit (3), a transformer coupling driving circuit (4), a B circuit in the transformer coupling driving circuit (4) and a constant voltage circuit (5), wherein the AC input EMC circuit (1) comprises a fuse F1, a piezoresistor MOV1, a capacitor CX1, a parallel resistor R1/R1A, a parallel resistor R2/R2A, an inductor LF1 and a thermistor 1, one end of the fuse F NTC1 is connected with a live wire of a power input end, and the other end of the fuse F NTC1 is connected with one end of the piezoresistor MOV1, the positive electrode of the capacitor CX1, one end of the parallel resistor R1/R1A and one end of an input end of the inductor LF1 in parallel; one end of the thermistor NTC1 is connected with a zero line of a power input end, the other end of the thermistor NTC1 is connected with the other end of the varistor MOV1, the negative electrode of the capacitor CX1, one end of the parallel resistor R2/R2A and the other end of the input end of the inductor LF1 in parallel, wherein the other end of the parallel resistor R2/R2A is connected with the other end of the parallel resistor R1/R1A in common; the output end of the inductor LF1 is connected with the bridge rectification input end of a rectification filter circuit (2), the rectification filter circuit (2) comprises bridge rectification and parallel capacitors EC1 and EC2, wherein one end of the output end of the bridge rectification is connected with the positive ends of the parallel capacitors EC1 and EC2, and the other end of the output end of the bridge rectification is grounded with the negative ends of the parallel capacitors EC1 and EC 2; the positive terminals of the parallel capacitors EC1 and EC2 are connected with the anodes of a parallel resistor R4, a resistor R5 and a capacitor C1 in an A circuit and one end of the input end of a transformer TR1, the A circuit comprises a resistor R4, a resistor R5, a capacitor C1, a resistor R3 and a diode D1, wherein the parallel resistor R4, the resistor R5 and the cathode of the capacitor C1 are connected with the resistor R3 in series, the other end of the resistor R3 is connected with the cathode of a diode D1, the anode of the diode D1 is connected with the other end of the input end of the transformer TR1, and the leakage inductance spike voltage generated by the transformer TR1 when the switch is turned off is absorbed through the parallel connection of the resistors and the capacitors and the unidirectional conductivity of the diode; the anode of a diode D1 in the A circuit is connected with the source of a MOS transistor Q1 and the anode of a capacitor C6 of a B circuit in a transformer coupling driving circuit (4), the B circuit comprises a MOS transistor Q1, a capacitor C6, a diode D3, a resistor R13 and a resistor R12, wherein the cathode of the capacitor C6 is connected with the drain of a MOS transistor Q1, the gate of the MOS transistor Q1 is connected with the anode of a diode D3 and the resistor R13, the cathode of the diode D3 and the other end of the resistor R13 are connected with a resistor R12 in common, and EMI interference suppression and switching tube loss reduction are realized when the switch is switched off through the B circuit; the output end of the transformer TR1 is connected with the anode of a parallel diode D9/D10 of an output rectifying and filtering circuit (3) and one end of a parallel resistor R15/R16 of a C circuit, wherein the output rectifying and filtering circuit (3) comprises a parallel diode D9/D10, a parallel resistor R15/R16, a capacitor C4 and a parallel capacitor EC3/EC4, the C circuit comprises a parallel resistor R15/R16 and a capacitor C4, the other end of the parallel resistor R15/R16 is connected with the anode of a capacitor C4, the cathode of the capacitor C4 is connected with the anode of a parallel capacitor EC3/EC4, the resistor R21 and one end of a resistor R20 of a constant voltage circuit (5), the cathode of a parallel diode D9/D10 and the anode of the output end, and the cathode of the parallel capacitor EC3/EC4 is connected with the other end of the output terminal TR1 and the cathode of the output.
2. The circuit for effectively suppressing the EMI of a switching power supply as claimed in claim 1, wherein the transformer coupling driving circuit (4) comprises a B circuit, a chip OB2281A, capacitors C2, C3 and EC5, resistors R6, R7, R8, R9, R10, R11 and R14, a diode D2, a photosensitive NPN transistor PH1/2 and an inductor Nf, wherein the "1" terminal of the chip OB2281A is grounded; the '2' terminal of the chip OB2281A is connected with the positive electrode of a capacitor C3 and the collector of the photosensitive NPN transistor PH1/2, and the negative electrode of the capacitor C3 and the emitter of the photosensitive NPN transistor PH1/2 are grounded in common; the "3" terminal of the chip OB2281A is connected to the OTP chip; the '4' terminal of the chip OB2281A is connected with the positive electrode of a capacitor C2 and one end of a resistor R11, the negative electrode of the capacitor C2 is grounded, the other end of the resistor R11 is connected with one end of a parallel resistor R6/R7/R8 and the drain of a MOS transistor Q1, and the other end of the parallel resistor R6/R7/R8 is grounded; the '5' terminal of the chip OB2281A is connected with one end of a resistor R10, one end of a resistor R14 and the anode of a capacitor EC5, the other end of the resistor R10 is connected with one end of a resistor R9, the other end of the resistor R9 is connected with the anode of a diode D1 in the circuit A, the other end of the resistor R14 is connected with the cathode of a diode D2, the anode of the diode D2 is connected with one end of an inductor Nf, and the other end of the inductor Nf is connected with the cathode of the capacitor EC5 in common ground; the "6" terminal of the chip OB2281A is connected to the other end of the resistor R12 in the B circuit.
3. The circuit for effectively suppressing switching power supply EMI as claimed in claim 1, wherein said constant voltage circuit (5) includes resistors R17, R18, R19, R20, R21 and R22, a capacitor C5, a photodiode PH1 and a regulator tube Q2, wherein the other end of the resistor R21 is connected to the positive electrode of the resistor R22 and the photodiode PH1, the other end of the resistor R22 is connected to the negative electrode of the photodiode PH1 in common to the resistor R17 and the "3" terminal of the regulator tube Q2, the other end of the resistor R17 is connected to the positive electrode of the capacitor C5, the negative electrode of the capacitor C5 is connected to the "1" terminal of the regulator tube Q2 and one end of a parallel resistor R18/R19, one end of the parallel resistor R18/R19 is connected to the other end of the resistor R20, and the other end of the parallel resistor R18/R19 is connected to the "2" terminal of the regulator tube Q2 in common to ground.
4. The circuit for effectively suppressing the EMI of the switching power supply according to claim 1, wherein the negative electrode of the parallel capacitor EC3/EC4 in the output rectifying-smoothing circuit (3) is connected to the negative electrode of the capacitor CY2, the positive electrode of the capacitor CY2 is connected to the negative electrode of the capacitor CY1, and the positive electrode of the capacitor CY1 is connected to the positive electrode of the capacitor C1 in the a circuit.
5. The circuit for effectively suppressing switching power supply EMI as recited in claim 1, wherein the positive terminal of said a circuit is connected in parallel with at least one resistor and at least one capacitor.
6. The circuit for effectively suppressing switching power supply EMI as recited in claim 1, wherein Q1 in said B circuit is a MOS transistor or a triode.
7. The circuit for effectively suppressing EMI of a switching power supply of claim 6 wherein the source terminal of Q1 in the B circuit and the positive terminal of the capacitor C6 are connected in common to at least one resistor, the other terminal of the resistor being connected to the common terminal of the input terminal of the transformer TR1 and the positive terminal of the diode D1.
8. The circuit for effectively suppressing EMI in a switching power supply of claim 1, wherein at least one of the resistors in the C circuit is connected in parallel, and the other end of the resistor is connected to the anode of the capacitor C4.
9. The circuit for effectively suppressing switching power supply EMI as claimed in claim 7, wherein the source terminal and the drain terminal of Q1 in the B circuit are connected in parallel with at least one capacitor or a series combination of a capacitor and a resistor.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202022511384.7U CN213547366U (en) | 2020-11-03 | 2020-11-03 | Circuit for effectively inhibiting EMI (electro-magnetic interference) of switching power supply |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202022511384.7U CN213547366U (en) | 2020-11-03 | 2020-11-03 | Circuit for effectively inhibiting EMI (electro-magnetic interference) of switching power supply |
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|---|---|
| CN213547366U true CN213547366U (en) | 2021-06-25 |
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| Application Number | Title | Priority Date | Filing Date |
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| CN202022511384.7U Active CN213547366U (en) | 2020-11-03 | 2020-11-03 | Circuit for effectively inhibiting EMI (electro-magnetic interference) of switching power supply |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114123741A (en) * | 2021-11-12 | 2022-03-01 | 江西吉安奥海科技有限公司 | Harmonic suppression circuit of flyback power supply |
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2020
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114123741A (en) * | 2021-11-12 | 2022-03-01 | 江西吉安奥海科技有限公司 | Harmonic suppression circuit of flyback power supply |
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