A circuit with auxiliary optical coupler and switching method thereof

Abstract

The present invention discloses a circuit with an auxiliary optical coupler and a switching method thereof, which are used to be connected between the output signal of a switching power supply and the feedback of an input terminal, and include a circuit between the primary and secondary of a transformer T1, wherein the primary of the transformer T1 is connected to the output terminal Output‑singal of the auxiliary optical coupler circuit through a control circuit model‑1, and the secondary of the transformer T1 is connected to the input terminal Input‑singal of the auxiliary optical coupler circuit through a dimming circuit model‑2; the problem of a fast light attenuation rate of the optical coupler inside the power supply caused by a high temperature environment during operation can be effectively avoided, thereby improving the reliability of the switching power supply.

Description

Technical Field

[0001] The invention relates to the technical field of switching power supplies, in particular to a circuit with an auxiliary optical coupler and a switching method thereof. Background Art

[0002] In the 21st century, with the increasing number of high-power lighting equipment, companies have begun to put forward new requirements for the conversion efficiency of power supplies under the huge pressure of power consumption. Switching power supplies have the characteristic of high conversion efficiency and have been widely used. However, in real life, the requirements for safety performance are relatively high. This is mainly because LEDs are prone to die, resulting in a very high output voltage of the switching power supply after a short circuit, which may threaten human safety.

[0003] Therefore, after considering the above problems, technicians in this field introduced the concept of isolation. In the field of switching power supplies, in addition to using relays, most isolation solutions use photocouplers, referred to as "optical couplers", which are mainly used to achieve the function of isolating the primary and secondary voltages of the isolation transformer. This achieves the purpose of isolating the input AC power supply from the output DC power supply that the user contacts.

[0004] Figure 1 This is a typical application structure of optocouplers in isolated switching power supplies, such as Figure 1 As shown: including input voltage-dividing supply resistors R3 and R4, output voltage-dividing supply resistors R1 and R2, optocoupler U1, transformer T1, model-1 control circuit, model-2 dimming circuit and Buck circuit, a typical secondary-side feedback flyback topology. However, in the process of implementing the technical solution of the invention in the embodiment of the present application, the inventor of the present application found that the above technology has at least the following technical problems: Since the optocoupler is an optoelectronic device, it is easy to produce light decay when working for a long time and under high temperature conditions, which makes the light intensity of the optocoupler insufficient, resulting in insensitive circuit feedback or high delay, which will greatly affect the current feedback loop of the switching power supply, and ultimately affect the output power. In severe cases, it may cause serious flickering of the lighting equipment.

[0005] In view of the above-mentioned disadvantages of isolated switching power supplies, they cannot meet the application requirements in many application fields. For example, tunnels and other application places have very high requirements for the stability of the power supply for a long time. When the switching power supply used in classrooms and libraries is not stable, it will cause flicker. The probability of myopia among students who are in such an environment for a long time is greatly increased.

[0006] Therefore, designing a circuit with an auxiliary optocoupler and a switching method thereof to ensure the life and stability of the optocoupler while improving the response speed of feedback has become a technical problem that needs to be urgently solved by technicians in the relevant technical field. Summary of the invention

[0007] The object of the present invention is to provide a circuit with an auxiliary optical coupler and a switching method thereof to solve the problems raised in the above background technology.

[0008] To achieve the above object, the present invention provides the following technical solutions:

[0009] A circuit with an auxiliary optocoupler, comprising a circuit between a primary and a secondary of a transformer T1, wherein the primary of the transformer T1 is connected to an output terminal Output-singal of the auxiliary optocoupler circuit through a control circuit model-1, and the secondary of the transformer T1 is connected to an input terminal Input-singal of the auxiliary optocoupler circuit through a dimming circuit model-2;

[0010] The auxiliary optocoupler circuit includes a main optocoupler U1, an auxiliary optocoupler U2, a peripheral circuit at the input end of the main optocoupler U1, a peripheral circuit at the input end of the auxiliary optocoupler U2, a peripheral circuit at the output end of the main optocoupler U1 and a peripheral circuit at the output end of the auxiliary optocoupler U2.

[0011] As a further technical solution of the present invention: the peripheral circuit of the main optocoupler U1 input end and the peripheral circuit of the auxiliary optocoupler U2 input end include a voltage divider resistor, an AND gate, an inverter, a transistor and a frequency generating circuit.

[0012] As a further technical solution of the present invention: there are two connection methods for the peripheral circuit of the input end of the main optocoupler U1, connection method 1: one end of the input end of the main optocoupler U1 is connected to the voltage-dividing resistor R2, and the other end is connected to the output end of the gate IC1, one end of the gate IC1 is connected to one end of the voltage-dividing resistor R2, and the other end is connected to the input end Input_singal of the auxiliary optocoupler circuit; connection method 2: one end of the input of the main optocoupler U1 is connected to the emitter of the transistor Q2, and the other end is connected to the input end Input_singal of the auxiliary optocoupler circuit, and the base of the transistor Q2 is connected to Fre_Input.

[0013] As a further technical solution of the present invention: in the peripheral circuit of the main optocoupler U1 output end, one end of the main optocoupler U1 output end is connected to one end of the voltage divider resistor R4 and the positive electrode of the diode D2, the negative electrode of the diode D2 is connected to the output end Output_singal of the auxiliary optocoupler circuit, and the other end is grounded GND.

[0014] As a further technical solution of the present invention: there are two connection methods for the peripheral circuit of the auxiliary optocoupler U2 output end, connection method 1: one end of the auxiliary optocoupler U2 output is connected to one end of the voltage-dividing resistor R4 and the positive electrode of the diode D3, the negative electrode of the diode D3 is connected to the output end Output_singal of the auxiliary optocoupler circuit, and the other end is grounded GND; connection method 2: based on the connection method 1, the negative electrode of D3 is connected to the input end of the inverter IC3, and the output end of the inverter IC3 is connected to the output end Output_singal of the auxiliary optocoupler circuit.

[0015] As a further technical solution of the present invention: there are two connection methods for the peripheral circuit of the auxiliary optocoupler U2 input end, connection method 1: one end of the auxiliary optocoupler U2 input end is connected to one end of the voltage-dividing resistor R2, and the other end is connected to the output end of the AND gate IC2, one end of the AND gate IC2 input is connected to the auxiliary optocoupler circuit input end Input_singal, and the other end is grounded GND; connection method 2, one end of the auxiliary optocoupler U2 input end is connected to the emitter of the transistor Q1, and the other end is connected to the auxiliary optocoupler circuit input end Input_singal, the collector of the transistor Q1 is connected to one end of the voltage-dividing resistor R2, and the base is connected to the output end of the inverter IC3, and the input end of the inverter IC3 is connected to Fre_Input.

[0016] As a further technical solution of the present invention: in the peripheral circuit of the auxiliary optocoupler U2 input end, one end of the auxiliary optocoupler U2 input end is connected to one end of the voltage-dividing resistor R2, and the other end is connected to the output end of the AND gate IC2; one end of the AND gate IC2 input is connected to the auxiliary optocoupler circuit input end Input_singal, and the other end is grounded GND; connection mode 2, one end of the auxiliary optocoupler U2 input end is connected to the emitter of the transistor Q1, and the other end is connected to the auxiliary optocoupler circuit input end Input_singal, the collector of the transistor Q1 is connected to one end of the voltage-dividing resistor R2, and the base is connected to the output end of the inverter IC3, and the input end of the inverter IC3 is connected to Fre_Input.

[0017] As a further technical solution of the present invention: the frequency generating circuit includes an operational amplifier U101, an operational amplifier U102 and a counter U103. The output end of the operational amplifier U101 is connected to the inverting end of the operational amplifier U102 through a resistor R1_1 to form a frequency-adjustable square wave. The output end of the operational amplifier U102 is connected to the frequency input CLK0 of the counter U103, and the frequency input CLK1 is connected to the signal output Q0.

[0018] A switching method with an auxiliary optical coupler circuit, using the above circuit, includes the following steps:

[0019] S1: Add AND gate circuits at the input ends of the main optocoupler U1 and the auxiliary optocoupler U2 to split the logic high and low levels of the input end Input_singal of the auxiliary optocoupler circuit, and control the conduction and non-conduction of the main optocoupler U1 and the auxiliary optocoupler in real time according to the input signal;

[0020] S2: Inverts the logic level at the output of the auxiliary optocoupler U2.

[0021] A switching method with an auxiliary optical coupler circuit, using the above circuit, includes the following steps:

[0022] S1: Controls the power supply of the main optocoupler U1 and the auxiliary optocoupler U2 through the frequency generating circuit;

[0023] S2: Use the input terminal Input_singal of the auxiliary optocoupler circuit to control the conduction and non-conduction of the main optocoupler U1 and the auxiliary optocoupler U2;

[0024] S3: Change the output frequency of the frequency generating circuit to modify the interval switching time of the main optocoupler U1 and the auxiliary optocoupler U2.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] 1. In medium and high power isolated switching power supplies with relatively compact space, the problem of fast light attenuation rate caused by high temperature environment during operation of the optocoupler inside the power supply can be effectively avoided, so that the optocoupler component of the switching power supply is in the best working state, the output current is more stable, and the power supply has higher reliability and faster dynamic response speed to the output end.

[0027] 2. When used in high-power LED driver power supplies, it can not only extend the service life of the power supply, but also solve the flicker problem caused by the optocoupler during use. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a circuit schematic diagram of an existing flyback isolation switching power supply;

[0029] Figure 2 This is a schematic diagram of an optocoupler switching circuit of a switching power supply according to a first embodiment of the present invention;

[0030] Figure 3 This is a schematic diagram of an optocoupler switching circuit of a switching power supply according to a second embodiment of the present invention;

[0031] Figure 4 This is a schematic diagram of a channel selection signal circuit of a switching power supply according to a second embodiment of the present invention. DETAILED DESCRIPTION

[0032] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0033] See also Figure 2Embodiment 1: A circuit with an auxiliary optocoupler is used to connect between the output signal and the input feedback of a switching power supply, using a photoelectric coupler, referred to as "optocupler", including a circuit between the primary and secondary of a transformer T1, the primary of the transformer is connected to the output terminal Output-singal of the auxiliary optocoupler circuit through a control circuit model-1, and the secondary of the transformer is connected to the input terminal Input-singal of the auxiliary optocoupler circuit through a dimming circuit model-2.

[0034] The circuit with auxiliary optocoupler includes a primary circuit consisting of fuse F1, common mode inductor L1, X capacitor CX1, rectifier bridge BD1, electrolytic capacitor C1, film capacitors C2, C3, I-shaped inductor L2, control circuit model-1, and starting resistor R5, and a secondary circuit consisting of freewheeling diode D1, inductor L3, electrolytic capacitor C4, and dimming circuit model-2, plus the auxiliary optocoupler circuit consists of main and auxiliary optocouplers U1, U2, voltage divider resistors R1, R2, R3, R4, AND gate components IC1, IC2, inverter IC3, and diodes D2, D3. One end of the input side of the main optocoupler U1 is connected to the voltage-dividing resistor R2, and the other end is connected to the output end of the AND gate IC1. One end of the input side of the AND gate IC1 is connected to the dimming circuit Input_singal, and the other end is connected to one end of the voltage-dividing resistor. One end of the input side of the auxiliary optocoupler U2 is connected to one end of the voltage-dividing resistor R2, and the other end is connected to the output end of the AND gate IC2. One end of the input side of the AND gate IC2 is connected to the dimming circuit Input_singal, and the other end is connected to GND. One end of the output side of the main optocoupler U1 is respectively connected to the voltage-dividing resistor R4 and the positive electrode of the diode D2, and the other end is connected to GND. One end of the output side of the auxiliary optocoupler U2 is respectively connected to the voltage-dividing resistor R4 and the positive electrode of the diode D3, and the negative electrode of the diode D3 is connected to the input side of the inverter IC3. Output_singal is respectively connected to the output side of the inverter IC3 and the negative electrode of the diode D2.

[0035] The specific working principle of the circuit with auxiliary optical coupler and the switching method thereof of the present invention is as follows:

[0036] This embodiment only analyzes the circuit improvement points, and considers that the power supply of the divided voltage R1, R2, R3, and R4 has no effect on the operation of U1, U2, IC1, and IC2. Therefore, according to the input signal Input_singal, it can be divided into two states:

[0037] State 1: When the input signal is at a high level, the output end of the AND gate IC1 component is at a logic high level, and the output end of the AND gate IC2 component is at a logic low level, so that the input side of the main optocoupler U1 is not conducting, and the input side of the auxiliary optocoupler U2 is conducting. Therefore, the output side of the main optocoupler U1 is at a logic high level, and the output side of the auxiliary optocoupler U2 is at a logic low level. The output of the inverter IC3 connected to the output side of the auxiliary optocoupler U2 is at a logic low level, so Output_singal is a logic high level, corresponding to the logic high level of the input signal Input_singal.

[0038] State 2: When the input signal is at a low level, the output end of the AND gate IC1 component is at a logic low level, and the output end of the NAND gate IC2 component is at a logic high level, so that the input side of the main optocoupler U1 is turned on, and the input side of the auxiliary optocoupler U2 is not turned on. Therefore, the output side of the main optocoupler U1 is at a logic low level, and the output side of the auxiliary optocoupler U2 is at a logic high level. The output of the inverter IC3 connected to the output side of the auxiliary optocoupler U2 is at a logic low level, so Output_singal is a logic low level, corresponding to the logic low level of the input signal.

[0039] Embodiment 2, Figure 3 The schematic diagram of the optocoupler switching circuit of the switching power supply of the second embodiment of the present invention is shown. The difference from the first embodiment is that the channel selection signal and the NPN transistors Q1 and Q2 are added, and the AND gates IC1 and IC2 are removed. The emitter of the transistor Q2 at one end of the input side of the main optocoupler is connected, and the other end is connected to the input signal Input_singal. The auxiliary optocoupler is connected to the emitter of the transistor Q1, and the other end is connected to the input signal Input_singal. The collectors of the transistors Q1 and Q2 are both connected to one end of the voltage divider resistor R2. The base of the transistor Q1 is connected to the output end of the inverter IC3, the input end of the inverter IC3 is connected to Fre_Input, and the base of the transistor Q2 is connected to Fre_Input.

[0040] Figure 4This is a schematic diagram of the channel selection signal circuit of the switching power supply of the second embodiment of the present invention, which includes two parts. The first part is a square wave generating circuit composed of operational amplifiers U101, U102, resistors R1_1, R1_2, R1_3, and capacitor C1_1, and the second part is a counting circuit composed of counter U103, resistors R1_4, and R1_5. The operational amplifier U101, capacitor C1_1, and resistor R1_2 form a triangle wave generator. The output end of the operational amplifier U101 is connected to one end of the resistor R1_1, and the other end of the resistor R1_1 is respectively connected to the inverting end of the operational amplifier U102 and one end of the resistor R1_3. The other end of the resistor R1_3 is connected to the output end of the operational amplifier U102. The in-phase ends of the operational amplifiers U101 and U102 are connected to GND, the positive pole is connected to +12, and the negative pole is connected to -12V. The output of the operational amplifier U102 is connected to the CLK0 of the counter U103, the CLK1 pin of the counter U103 is connected to the counter Q0, one end of the voltage divider resistor R1_4 is connected to +12V, and the other end is connected to the VCC pin of the counter U103, one end of the voltage divider resistor R1_5 is connected to the VCC pin of the counter U103, and the other end of the voltage divider resistor R1_5 is connected to GND.

[0041] The specific working principle of the circuit with auxiliary optical coupler and the switching method thereof of the present invention is as follows:

[0042] The square wave signal of 0.05Hz~10Hz generated by operational amplifier U102 is transmitted to the CLK0 pin of counter U103. At this time, the Q0 pin of counter U103 obtains the square wave signal of the CLK0 pin of counter U103 divided by two and sends it to the CLK1 pin of counter U103 to form a decimal counter. The output frequency of the Q1, Q2, and Q3 pins of counter U103 gradually decreases. Please refer to Figure 3 , Fre_Input can select Fre_Output according to actual needs.

[0043] Therefore, according to the Fre_Input and Input_singal signals, it can be divided into four states:

[0044] State 1: When Fre_Input is at a logic low level and Input_singal is at a logic low level, the output side of the main optocoupler is at a logic high level, the output side of the auxiliary optocoupler is at a logic low level, and the corresponding input signal is at a low level.

[0045] State 2: When Fre_Input is at a logic low level and Input_singal is at a logic high level, the output side of the main optocoupler is at a logic low level, the output side of the auxiliary optocoupler is at a logic high level, and the corresponding input signal is at a high level.

[0046] State 3: When Fre_Input is at a logic high level and Input_singal is at a logic low level, the output side of the main optocoupler is at a logic low level, the output side of the auxiliary optocoupler is at a logic high level, and the corresponding input signal is at a high level.

[0047] State 4: When Fre_Input is at a logic low level and Input_singal is at a logic high level, the main optocoupler output side is at a logic high level, the auxiliary optocoupler output side is at a logic high level, and the corresponding input signal is at a high level.

[0048] Through the analysis of the working principle of the above circuit, the circuit with auxiliary optocoupler and the switching method of the present invention utilize the switching of the working time between the main and auxiliary optocouplers to reduce the working temperature of the optocoupler and slow down the occurrence of optocoupler light decay, thereby extending the life of the optocoupler and improving the reliability of the power supply.

[0049] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

[0050] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A circuit with an auxiliary optical coupler, comprising a circuit between the primary and secondary of a transformer T1, characterized in that: The primary of the transformer T1 is connected to the output terminal Output-singal of the auxiliary optocoupler circuit through the control circuit model-1, and the secondary of the transformer T1 is connected to the input terminal Input-singal of the auxiliary optocoupler circuit through the dimming circuit model-2; The auxiliary optocoupler circuit includes a main optocoupler U1, an auxiliary optocoupler U2, a peripheral circuit of the input end of the main optocoupler U1, a peripheral circuit of the input end of the auxiliary optocoupler U2, a peripheral circuit of the output end of the main optocoupler U1, and a peripheral circuit of the output end of the auxiliary optocoupler U2; the peripheral circuit of the input end of the main optocoupler U1 and the peripheral circuit of the input end of the auxiliary optocoupler U2 include a voltage divider resistor, an AND gate, an inverter, a triode, and a frequency generating circuit, wherein: There are two connection modes for the peripheral circuit of the input end of the main optocoupler U1. Connection mode 1: one end of the input end of the main optocoupler U1 is connected to the voltage-dividing resistor R2, and the other end is connected to the output end of the gate IC1, and one end of the gate IC1 is connected to one end of the voltage-dividing resistor R2, and the other end is connected to the input end Input_singal of the auxiliary optocoupler circuit; Connection mode 2: one end of the input end of the main optocoupler U1 is connected to the emitter of the transistor Q2, and the other end is connected to the input end Input_singal of the auxiliary optocoupler circuit, and the base of the transistor Q2 is connected to Fre_Input; In the peripheral circuit of the output end of the main optocoupler U1, one end of the output end of the main optocoupler U1 is connected to one end of the voltage-dividing resistor R4 and the positive electrode of the diode D2, the negative electrode of the diode D2 is connected to the output end Output_singal of the auxiliary optocoupler circuit, and the other end is grounded GND; There are two connection modes for the peripheral circuit of the output end of the auxiliary optocoupler U2. Connection mode 1: one end of the output of the auxiliary optocoupler U2 is connected to one end of the voltage-dividing resistor R4 and the positive electrode of the diode D3, the negative electrode of the diode D3 is connected to the output end Output_singal of the auxiliary optocoupler circuit, and the other end is grounded GND; Connection mode 2: based on the connection mode 1, the negative electrode of D3 is connected to the input end of the inverter IC3, and the output end of the inverter IC3 is connected to the output end Output_singal of the auxiliary optocoupler circuit; There are two connection modes for the peripheral circuit of the input end of the auxiliary optocoupler U2. Connection mode 1: one end of the input end of the auxiliary optocoupler U2 is connected to one end of the voltage-dividing resistor R2, and the other end is connected to the output end of the AND gate IC2. One end of the input of the AND gate IC2 is connected to the input end Input_singal of the auxiliary optocoupler circuit, and the other end is grounded GND. Connection mode 2: one end of the input end of the auxiliary optocoupler U2 is connected to the emitter of the transistor Q1, and the other end is connected to the input end Input_singal of the auxiliary optocoupler circuit. The collector of the transistor Q1 is connected to one end of the voltage-dividing resistor R2, and the base is connected to the output end of the inverter IC3. The input end of the inverter IC3 is connected to Fre_Input.

2. A circuit with an auxiliary optical coupler according to claim 1, characterized in that: The frequency generating circuit includes an operational amplifier U101, an operational amplifier U102 and a counter U103. The output end of the operational amplifier U101 is connected to the inverting end of the operational amplifier U102 through a resistor R1_1 to form a square wave with adjustable frequency. The output end of the operational amplifier U102 is connected to the frequency input CLK0 of the counter U103, and the frequency input CLK1 is connected to the signal output Q0.

3. A switching method with an auxiliary optocoupler circuit, characterized in that: The circuit according to any one of claims 1 to 2 comprises the following steps: S1: Add AND gate circuits at the input ends of the main optocoupler U1 and the auxiliary optocoupler U2 to split the logic high and low levels of the input end Input_singal of the auxiliary optocoupler circuit, and control the conduction and non-conduction of the main optocoupler U1 and the auxiliary optocoupler in real time according to the input signal; S2: Inverts the logic level at the output of the auxiliary optocoupler U2.

4. A switching method with an auxiliary optocoupler circuit, characterized in that: The circuit according to any one of claims 1 to 2 comprises the following steps: S1: Controls the power supply of the main optocoupler U1 and the auxiliary optocoupler U2 through the frequency generating circuit; S2: Use the input terminal Input_singal of the auxiliary optocoupler circuit to control the conduction and non-conduction of the main optocoupler U1 and the auxiliary optocoupler U2; S3: Change the output frequency of the frequency generating circuit to modify the interval switching time of the main optocoupler U1 and the auxiliary optocoupler U2.

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