阅读说明：本技术 一种光电耦合器输出端恒功率老炼电路 (Constant-power aging circuit for output end of photoelectric coupler ) 是由 代骞 王智 钱军军 吕前进 任真伟 郭俊峰 周卓 方明洪 简青青 于 2021-07-23 设计创作，主要内容包括：一种光电耦合器输出端恒功率老炼电路,涉及元器件老炼技术领域。包括：电源V1、电源V2、输入端恒流模块、待老炼光耦、输出端限流稳压差模块、输出端恒流控制模块、输出电流采样模块；输入端恒流模块的一端接V1正极,另一端接待老炼光耦输入单元正极端及输出端恒流控制模块正输出端,输出端限流稳压差模块的一端接V2正极,另一端接待老炼光耦输出单元的正极端,输出电流采样模块的一端接待老炼光耦输出单元的负极端,另一端接地；输出端恒流控制模块的输入端并联在输出电流采样模块的两端,输出端并联在待老炼光耦输入单元的的两端。解决了现有老炼电路老炼功率不稳定、质量不受控、成本高等问题,广泛应用于光电耦合器的老炼电路中。(A constant-power aging circuit for an output end of a photoelectric coupler relates to the technical field of aging of components. The method comprises the following steps: the device comprises a power supply V1, a power supply V2, an input end constant current module, an optical coupler to be aged, an output end current-limiting and voltage-stabilizing difference module, an output end constant current control module and an output current sampling module; one end of the input end constant current module is connected with a V1 positive pole, the other end of the input end constant current module is connected with a positive pole of the to-be-aged optocoupler input unit and a positive output end of the output end constant current control module, one end of the output end current-limiting voltage-stabilizing difference module is connected with a V2 positive pole, the other end of the output end current-limiting voltage-stabilizing difference module is connected with a positive pole of the to-be-aged optocoupler output unit, one end of the output current sampling module is connected with a negative pole end of the to-be-aged optocoupler output unit, and the other end of the output current sampling module is grounded; the input end of the output end constant current control module is connected in parallel with two ends of the output current sampling module, and the output end of the output end constant current control module is connected in parallel with two ends of the optical coupler input unit to be aged. The problems of unstable aging power, uncontrolled quality, high cost and the like of the conventional aging circuit are solved, and the aging circuit is widely applied to the aging circuit of the photoelectric coupler.)

1. A photoelectric coupler output end constant power aging circuit is characterized by comprising: the device comprises an input direct-current power supply V1, an output direct-current power supply V2, an input end constant-current module, an optical coupler to be aged, an output end current-limiting and voltage-stabilizing difference module, an output end constant-current control module and an output current sampling module;

one end of the input end constant current module is connected with the anode of an input direct current power supply V1, the other end of the input end constant current module is connected with the anode of the to-be-aged optocoupler input unit and the anode of the output end constant current control module, the cathode of the input direct current power supply V1 is grounded, and the cathode of the to-be-aged optocoupler input unit is grounded;

one end of the output end current-limiting voltage-stabilizing difference module is connected with the anode of an output direct-current power supply V2, the other end of the output end current-limiting voltage-stabilizing difference module is connected with the anode end of the aging optocoupler output unit, and the cathode of the output direct-current power supply V2 is grounded;

one end of the output current sampling module is connected with the negative end of the aging optocoupler output unit, and the other end of the output current sampling module is grounded;

the input end of the output end constant current control module is connected in parallel with two ends of the output current sampling module, and the positive input end of the output end constant current control module is connected with the negative end of the output unit of the optical coupler to be aged; the output end of the output end constant current control module is connected in parallel with two ends of the optical coupler input unit to be aged, and the positive output end of the output end constant current control module is connected with the positive end of the optical coupler input unit to be aged.

2. The output end constant-power aging circuit of a photoelectric coupler as claimed in claim 1, wherein one end of the input end constant-current module is connected with the negative electrode of an input direct-current power supply V1, the other end of the input end constant-current module is connected with the negative electrode end of an input unit of the optical coupler to be aged and the negative electrode end of the output end constant-current control module, the negative electrode of the input direct-current power supply V1 is grounded, and the positive electrode end of the input unit of the optical coupler to be aged is connected with the positive electrode of the input direct-current power supply V1.

3. The constant-power aging circuit for the output end of a photoelectric coupler, as claimed in claim 1, wherein the input end constant-current module is an input end current-limiting resistor R1, the optocoupler to be aged is an optocoupler OC1 whose output is a phototriode, the output end current-limiting voltage-stabilizing difference module is an output end current-limiting resistor R2, the output end constant-current control module is a negative feedback circuit, and the output current sampling module is an output current sampling resistor R3;

one end of the R1 is connected with the anode of an input direct current power supply V1, and the other end of the R1 is connected with the anode of an OC1 input unit and the anode of the output end of the negative feedback circuit;

one end of the R2 is connected with the anode of an output direct current power supply V2, and the other end of the R2 is connected with the anode end of an OC1 output unit;

one end of the R3 is connected with the negative end of the OC1 output unit, and the other end of the R3 is grounded;

the input end of the negative feedback circuit is connected in parallel with two ends of R3, and the positive input end is connected with the negative end of the OC1 output unit;

the output end of the negative feedback circuit is connected in parallel with the two ends of the OC1 input unit, and the positive output end of the negative feedback circuit is connected with the positive end of the OC1 input unit.

4. The constant-power aging circuit for the output end of a photoelectric coupler, as claimed in claim 1, wherein the input end constant-current module is an input end current-limiting resistor R1, the optocoupler to be aged is an optocoupler OC1 whose output is a phototriode, the output end current-limiting voltage-stabilizing difference module is an output end current-limiting resistor R2, the output end constant-current control module is a negative feedback circuit, and the output current sampling module is an output current sampling resistor R3;

one end of the R1 is connected with the negative electrode of the input direct-current power supply V1, and the other end of the R1 is connected with the negative electrode end of the OC1 input unit and the negative electrode end of the output end of the negative feedback circuit;

one end of the R2 is connected with the positive electrode of the output direct-current power supply V2, and the other end of the R2 is connected with the positive input end of the negative feedback circuit;

one end of the R3 is connected with the positive input end of the negative feedback circuit, and the other end is connected with the negative input end of the negative feedback circuit;

the negative input end of the negative feedback circuit is connected with the positive end of the OC1 output unit, and the negative end of the OC1 input unit is grounded.

5. The constant-power aging circuit for the output end of a photoelectric coupler as claimed in claim 3 or claim 4, wherein the R1, R2 and R3 are precision metal film potentiometers.

6. The constant-power aging circuit for the output end of the photoelectric coupler is characterized in that digital potentiometers are adopted for R1, R2 and R3.

7. The constant-power aging circuit for the output end of a photocoupler according to claim 3, wherein the negative feedback circuit is a common emitter circuit formed by an NPN triode Q2, the input end of the negative feedback circuit is BE pole, and the output end of the negative feedback circuit is CE pole; the NPN triode Q2 is 2N 3904.

8. The constant power aging circuit for the output end of a photoelectric coupler as claimed in claim 3, wherein the negative feedback circuit comprises a PNP triode Q1 and an NPN triode Q2, the base electrode of Q1 is connected with the collector electrode of Q2, the collector electrode of Q1 is connected with the emitter electrode of Q2 and is grounded, the input end of the negative feedback circuit is the BE electrode of Q2, and the output end of the negative feedback circuit is the CE electrode of Q1; the PNP triode Q1 is 2N3906, and the NPN triode Q2 is 2N 3904.

9. The constant power aging circuit for the output end of a photoelectric coupler as claimed in claim 3, wherein the negative feedback circuit is realized by an operational amplifier A1, the input end of the input end A1 of the negative feedback circuit is the input end of A1, and the output end of the negative feedback circuit is the output end of A1.

10. The output end constant-power aging circuit of a photoelectric coupler as claimed in claim 9, wherein said operational amplifier a1 is a high input impedance high precision operational amplifier.

Technical Field

The invention relates to the technical field of aging of components, in particular to an aging circuit of a photoelectric coupler.

Background

The photoelectric coupler (optical coupler for short) is applied to the occasion needing physical isolation on electricity to transmit signals, and the transmission process is as follows: the input end converts the electric signal into an optical signal, and the output end receives the optical signal and converts the optical signal into the electric signal; the input end of the light-emitting diode is physically isolated from the output end of the light-emitting diode, and the input end is a light-emitting diode and the output end is a phototriode.

At present, the aging screening of the optical coupler is divided into two steps of input end aging and output end aging. When the output end is subjected to aging screening, a certain forward current I needs to be applied to a light emitting diode in the optical coupler_FMeanwhile, a specified power is applied to the phototriode at the output end for aging, and the specified power is usually a rated power P_CM。

Fig. 1 is a circuit used for aging an output end of an optical coupler, and the working principle of the circuit is as follows: regulating output voltage V2 to a certain value V_CEVoltage values (typically between 0.6 and 0.75 times the breakdown voltage); r2 is sampling resistor or current limiting resistor, and its voltage at two ends can be converted into I_CA current value; the V1 voltage and R1 resistance were then adjusted to control I_FMake the output end I_CCurrent and V_CEThe product of the voltages reaches P_CMThereby achieving the purpose of aging.

As shown in fig. 1, the output terminal triodeAging power of (2): p_C＝V_C×I_C,I_CFrom input current I_FAnd CTR determination with the optical coupler is carried out, and the relation is as follows: i is_C＝I_FX CTR where I_F＝(V1-V_F) /R1, therefore, the aging power of the output transistor:

from the above equation, it can be seen that if CTR is not uniform or varies, the power P_CA change will occur. The inconsistency of CTR can be roughly divided into two cases:

firstly, the CTR of the same optical coupler fluctuates under different work conditions, such as temperature fluctuation and other reasons, so that the power P is caused_CA change is made.

Secondly, the optical couplers of the same model have individual differences in the parameter of CTR, and if each optical coupler is specifically used, some CTRs are larger, some CTRs are smaller, and the difference is different from tens of percent to hundreds of percent.

When the optical coupler is actually used for aging, hundreds of optical couplers are needed for power aging, so that the circuit in the figure 1 needs to be parallelly connected hundreds of times. V1, R1, V if applied to each optocoupler_CAre all the same and ignore each optocoupler V_FThe individual difference of (2) is P of each optocoupler_CPower is directly related to the variability of CTR; theoretically, the P value of each optocoupler can be adjusted by respectively adjusting the R1 value or the V1 value of each optocoupler_CThe power is consistent, but the difficulty and the cost of concrete implementation are sharply increased, the number of times of adjusting the optical coupler aging is needed, and the problem that the CTR of the same optical coupler changes along with the environment cannot be avoided.

In the aspect of physical mechanism, due to the reasons that the consistency of the assembly process of each optocoupler, the parameters of the chip at the transmitting end and the chip at the receiving end of the optocoupler have individual differences and the like, the consistency of the CTR of each optocoupler is poor.

The purpose of power burn-in is to reject devices that have potential or manufacturing defects. Failure of these devices is time and stress dependent, e.g., without aging, and the devices will experience early failure under normal use conditions.

The power of an output end triode in the existing burn-in circuit is unstable, so that the output end triode has the possibility of burn-in with over power or under power, and the burn-in with over power can cause the following consequences: firstly, the parameters of the product are slowly degraded, and the service life is shortened; secondly, the product parameters are abnormal; direct damage of the product; of these three consequences, the first one often introduces the problem of quality uncontrollable factors, since it is difficult to screen them out by means of parameter detection; the second and third types can be screened out by parameter detection. The problems introduced by under-power burn-in are: due to the low stress applied, there is a possibility that the defective products are difficult to reject by power aging, and thus there is a possibility that quality uncontrollable factors are introduced.

Therefore, the main problems of the existing burn-in circuit are as follows: the aging power of the output end triode is unstable and has large fluctuation, so that the over-current stress is easily caused, and the service life of the optocoupler is unstable after aging, thereby causing uncontrolled quality and reliability; the CTR of the optical coupler has individual difference, so that the aging power deviation of each optical coupler is large, the consistency of the CTR is poor, and the aging consistency is poor; the batch aging compatibility is poor; poor aging reliability and the like.

In view of the above, the present invention is particularly proposed.

Disclosure of Invention

The invention aims to solve the problems of unstable aging power, large fluctuation, poor aging reliability, uncontrolled quality and reliability, high aging cost and the like of the triode at the output end of the photoelectric coupler in the existing aging circuit.

In the prior art, for a voltage stabilizing circuit, when a load changes, the current of the voltage stabilizing circuit inevitably changes to maintain constant voltage; similarly, for a constant current circuit, when the load changes, the voltage of the constant current circuit inevitably changes to keep the current constant; the current cannot be constant if the voltage is kept constant, and the voltage cannot be constant if the current is kept constant.

Prior art As shown in FIG. 1, by adjusting V2 voltage and I_FThe aging power of the output end triode is determined by the current, but the aging quality is influenced due to the fact that the optical coupler CTR is large in change along with environmental factors and poor in batch property and consistency, and the power fluctuation range of the optical coupler CTR is large. In order to ensure that the power fluctuation range is small and even constant power, the voltage and the current of an output end unit (an output triode) of the optical coupler are required to be constant, and because a constant-voltage circuit is not constant-current and a constant-current circuit is not constant-voltage in the prior art, how to design a circuit which is constant-voltage and constant-current is the starting point of the circuit design, and the convenience of aging and the cost of batch aging are both considered. In practical application, hundreds of optocouplers can be used for aging simultaneously, the circuit in fig. 1 needs to be repeated by hundreds of times, the complexity and the cost of the circuit are increased by hundreds of times, and the addition of any element means that hundreds of elements are added in practical application, so that the simplicity of the circuit is very important in order to realize the constant voltage and constant current function.

In the circuit of FIG. 1, I_CThe difference in current is caused by the change or inconsistency of CTR, which is objective, so that the change of CTR does not affect I_CAdditional parameters are needed for compensation, and according to the optical coupling characteristic of the circuit, the compensation can be realized through I_FTo compensate, when CTR becomes large, I is set_FWhen the adjustment is small, I can be maintained_CAnd vice versa. Therefore, I can be controlled by an output constant current control module (output current sampling, amplifying and feedback control network)_CAnd I_FAnd (4) associating to design a circuit block diagram of the patent.

Therefore, the invention provides a constant-power aging circuit for the output end of a photoelectric coupler, which adopts the constant-current and constant-voltage technology of the output end to realize constant-power aging of the output end of the photoelectric coupler. As shown in fig. 2.

The constant-power aging circuit for the output end of the photoelectric coupler comprises: the device comprises an input direct-current power supply V1, an output direct-current power supply V2, an input end constant-current module, an optical coupler to be aged, an output end current-limiting and voltage-stabilizing difference module, an output end constant-current control module and an output current sampling module.

One end of the input end constant current module is connected with the anode of an input direct current power supply V1, the other end of the input end constant current module is connected with the anode of the to-be-aged optocoupler input unit and the anode of the output end constant current control module, the cathode of the input direct current power supply V1 is grounded, and the cathode of the to-be-aged optocoupler input unit is grounded;

one end of the output end current-limiting voltage-stabilizing difference module is connected with the anode of an output direct-current power supply V2, the other end of the output end current-limiting voltage-stabilizing difference module is connected with the anode end of the aging optocoupler output unit, and the cathode of the output direct-current power supply V2 is grounded; the output end current-limiting voltage-stabilizing difference module has the functions of current limiting and generating voltage stabilizing difference, so that the output voltage V of the output unit of the optical coupler to be aged is enabled_EStabilizing;

one end of the output current sampling module is connected with the negative end of the aging optocoupler output unit, and the other end of the output current sampling module is grounded;

the input end of the output end constant current control module is connected in parallel with two ends of the output current sampling module, and the positive input end of the output end constant current control module is connected with the negative end of the output unit of the optical coupler to be aged; the output end of the output end constant current control module is connected in parallel with two ends of the optical coupler input unit to be aged, and the positive output end of the output end constant current control module is connected with the positive end of the optical coupler input unit to be aged. Is organically matched with the output end current-limiting voltage-stabilizing differential module to realize the output voltage V of the output unit of the optical coupler to be aged_EAnd an output current I_CAnd the stability is realized, so that the purpose of constant-power aging of the output end of the photoelectric coupler is realized.

And for the input end constant current module, the constant current module can also be connected to the negative input end of the aging circuit, and the figure is omitted. At this time, one end of the input end constant current module is connected with the negative electrode of the input direct current power supply V1, the other end of the input end constant current module is connected with the negative electrode end of the to-be-aged optocoupler input unit and the negative electrode end of the output end constant current control module, the negative electrode of the input direct current power supply V1 is grounded, and the positive electrode of the to-be-aged optocoupler input unit is connected with the positive electrode of the input direct current power supply V1.

In order to implement the technical scheme shown in fig. 2, the invention provides an output end constant power aging circuit of a photoelectric coupler, which is divided into a positive input end connected with a constant current module aging circuit (shown in fig. 3) and a negative input end connected with the constant current module aging circuit (shown in fig. 4) according to the access mode of an input end constant current module.

I, for the positive input end connects the constant current module burn-in circuit

The method comprises the following steps: the device comprises an input direct-current power supply V1, an output direct-current power supply V2, an input end current-limiting resistor R1 (playing the role of input end constant current and current limiting), an optical coupler OC1 to be aged, an output end current-limiting resistor R2 (playing the role of output end constant voltage and current limiting), a negative feedback circuit (carrying out output end constant current control), and an output current sampling resistor R3.

One end of the R1 is connected with the anode of an input direct current power supply V1, and the other end of the R1 is connected with the anode of an OC1 input unit and the anode of the output end of the negative feedback circuit;

one end of the R2 is connected with the anode of an output direct current power supply V2, and the other end of the R2 is connected with the anode end of an OC1 output unit;

one end of the R3 is connected with the negative end of the OC1 output unit, and the other end of the R3 is grounded;

the input end of the negative feedback circuit is connected in parallel with two ends of R3, and the positive input end is connected with the negative end of the OC1 output unit; the output end of the negative feedback circuit is connected in parallel with the two ends of the OC1 input unit, and the positive output end of the negative feedback circuit is connected with the positive end of the OC1 input unit.

The R1, R2 and R3 can adopt precise metal film potentiometers, and can adopt digital potentiometers in consideration of the problem of automatic control.

Secondly, for the aging circuit of the constant current module of the negative input terminal termination

The method comprises the following steps: the device comprises an input direct-current power supply V1, an output direct-current power supply V2, an input end current-limiting resistor R1 (playing the role of input end constant current and current limiting), an optical coupler OC1 to be aged, an output end current-limiting resistor R2 (playing the role of output end constant voltage and current limiting), a negative feedback circuit (carrying out output end constant current control), and an output current sampling resistor R3.

One end of the R1 is connected with the negative electrode of the input direct-current power supply V1, and the other end of the R1 is connected with the negative electrode end of the OC1 input unit and the negative electrode end of the output end of the negative feedback circuit;

one end of the R2 is connected with the positive electrode of the output direct-current power supply V2, and the other end of the R2 is connected with the positive input end of the negative feedback circuit;

one end of the R3 is connected with the positive input end of the negative feedback circuit, and the other end is connected with the negative input end of the negative feedback circuit;

the negative input end of the negative feedback circuit is connected with the positive end of the OC1 output unit, and the negative end of the OC1 input unit is grounded;

the R1, R2 and R3 can adopt precise metal film potentiometers, and can adopt digital potentiometers in consideration of the problem of automatic control.

Third, circuit principle analysis

Taking the schematic diagram shown in fig. 3 as an example, the pair I is completed in the negative feedback circuit by introducing the sampling circuit and the negative feedback circuit in the burn-in circuit_CDetection of current, if I_CIf the current is larger than the set value, the feedback current I is increased₁Due to I₁Increasing the input end current I of the optical coupler_FWill be reduced and thus the output terminal I_CThe current is reduced to reach the control I_CThe current is stabilized within the range of the set value, so that the constant current is realized; for the problem of constant voltage, the input end V of the negative feedback circuit is connected_EIs set to a constant value, the loop voltage is formulated as:

V_CE＝V₂-V_R2-V_E

wherein V_R2Is the voltage across R2, the voltage value of which is related to the current I flowing through it_CIn connection with, once I is put_CControl to a constant value, then V_R2Is also a constant value, then V_CEThe voltage can be constant, the value of the voltage is basically unchanged, and the voltage is constant; therefore, the requirements of constant voltage and constant current of the output end of the optical coupler are met, and the purpose of constant power aging of the output end is achieved.

Has the advantages that:

through the analysis to the circuit is smelted always to current opto-coupler output, the problem that quality and reliability uncontrollable factor are introduced to current circuit of smelting always exists and the CTR of opto-coupler has individual difference, leads to specifically leading to the great problem of the power deviation of smelting always of each opto-coupler. The technical scheme of the invention solves the problems and has the advantages that:

(1) the power stability is good when the opto-coupler output is used for refining, has solved the problem that the quality is uncontrollable factor is introduced in the link of refining in the current circuit of refining, has also solved the CTR of opto-coupler simultaneously and has had individual difference, leads to specifically leading to the great problem of the power deviation of refining of each opto-coupler.

(2) The circuit is simple, is easy to expand in parallel, and has good realizability, maintainability and popularization.

(3) The reliability is high, the batch consistency is good, the tolerance to CTR fluctuation is large, and the application range is wide.

The technical scheme of the invention is widely applied to photoelectric coupler aging circuits with high reliability and batch performance.

Drawings

Fig. 1 is a schematic diagram of a conventional aging circuit at the output end of a photoelectric coupler.

Fig. 2 is a schematic diagram of the constant power aging principle of the output end of the photoelectric coupler of the present invention.

Fig. 3 is a schematic circuit block diagram of the burn-in circuit with the positive input terminal connected to the constant current module.

Fig. 4 is a schematic circuit diagram of the burn-in circuit with the negative input terminal connected to the constant current module.

Fig. 5 is a schematic diagram of a single-tube sampling amplification type constant-power aging circuit.

Fig. 6 is a schematic structural diagram of a composite tube sampling amplification type constant power aging circuit.

Fig. 7 is a schematic diagram of an integrated operational amplifier sampling amplification type constant power aging circuit.

In the figure: v1 is an input dc power supply, V2 is an output dc power supply, R1 is an input current limiting resistor, R2 is an output current limiting resistor, R3 is an output sampling resistor, OC1 is a photoelectric coupler to be aged, Q1 is a PNP transistor, Q2 is an NPN transistor, and a1 is an operational amplifier.

Detailed Description

Further, the positive input end is connected with the constant current module burn-in circuit, and according to the implementation mode of the negative feedback circuit, the following three specific implementation modes are listed according to the magnitude of the sampling amplification capacity and the control capacity:

example 1: (FIG. 5)

The negative feedback circuit is implemented by a common emitter circuit formed by an NPN transistor Q2. The input end of the negative feedback circuit is BE pole, and the output end of the negative feedback circuit is CE pole. The NPN triode Q2 is 2N 3904.

Example 2: (FIG. 6)

The negative feedback circuit is realized by a composite transistor consisting of a PNP triode Q1 and an NPN triode Q2. The base of Q1 is connected to the collector of Q2, the collector of Q1 is connected to the emitter of Q2 and grounded, the BE pole of the input Q2 of the negative feedback circuit, and the CE pole of Q1 is the output of the negative feedback circuit. The PNP triode Q1 is 2N3906, and the NPN triode Q2 is 2N 3904.

Example 3: (FIG. 7)

The negative feedback circuit is implemented by an operational amplifier a 1. The input end of the negative feedback circuit A1, and the output end of the negative feedback circuit is the output end of A1. The operational amplifier a1 is a high input impedance high precision operational amplifier.

The constant-power aging circuit at the output end of the photoelectric coupler shown in fig. 5 comprises:

analyzing a steady flow and voltage stabilization principle:

taking the embodiment 1 as an example, as shown in fig. 5, first, regardless of Q2 and R3, when V1 is powered on, a forward current I is provided to the led at the input end of the optocoupler_FThe light emitting diode works to drive the output end of the phototriode to be conducted to generate I_CThe relationship of the current, IC and IF is determined by the CTR of the optocoupler:

I_C＝CTR·I_F

since the CTR changes with the working conditions and each optocoupler has differences, I_CThe current will not be constant. In the circuit of fig. 5, Q2 and R3 are introduced to form a negative feedback circuit to solve the problem of CTR variation and inconsistency, where CTR has two inconsistent states, one is larger and the other is smaller, and the following two cases are analyzed respectively to show how the circuit satisfies the functions.

First, the CTR is large.

When CTR is larger, then I_CThe current is larger, so that the voltage V at the two ends of the resistor R3 is increased_R3Become large, V_R3Becoming larger will make Q2 threeThe pole tube is conducted to generate current I_CQ2Or let I_CQ2And is increased. Meanwhile, because in the circuit:

I_F＝I₁-I_CQ2

I_CQ2increase will make I_FBecome smaller, and I_FBecome smaller and result in I_CThe current becomes smaller, thereby generating negative feedback effect to make I_CThe current is kept constant or within an allowable range.

Second, the CTR is small.

CTR is small, so that the output end I_CWhen the current is small, the negative feedback circuit will not work, and I cannot be adjusted_CThe current is increased to the required value. For this case, only I needs to be added₁The current is adjusted to ensure that the negative feedback circuit acts, i.e. when the circuit is designed, I is adjusted₁The current is designed to be larger, I₁The larger the design, the larger the CTR range that can accommodate this, but too large I₁Will generate energy waste and the like, so it is adjusted to I_FTwice as much.

Analyzed to this point, the circuit can guarantee I_CConstant, followed by analysis of the voltage V at the output of the optocoupler_CEWhether it can also be constant. From the circuit, the following is derived:

V_CE＝V₂-V_R2-V_E

V_Ea B, E interelectrode voltage equal to Q2, V, which is a diode forward voltage characteristic, remains substantially constant_R2For the voltage across the resistor, from formula V_R2＝I_CR2 decision, wherein I_CR2 is a constant value, then V_R2The voltage V2 is constant voltage source voltage, and is constant value, so the voltage V at the output end of the photoelectric coupler_CEMay also be kept constant.

Based on the above analysis, in the circuit of FIG. 5, the output terminal voltage V of the photocoupler_CECurrent I_CCan keep constant, so the circuit can meet the requirement of constant power of an output end triode of the photoelectric coupler.

The operation principle of the circuits shown in fig. 6 and 7 is similar to that of the circuit shown in fig. 5, and the same function can be achieved.

Fig. 5, fig. 6 and fig. 7 are specific circuit diagrams designed according to the circuit block diagram of fig. 3, and it can be seen that in the specific circuit, V is set_EIt is possible to set the voltage of the spot to a substantially constant value.

The specific circuit capable of realizing the function of the block diagram in fig. 3 is not limited to the examples illustrated in fig. 5, 6 and 7, and the purpose of constant power aging of the output end of the optical coupler can be realized as long as the idea of the circuit block diagram in fig. 3 is satisfied.

Finally, it should be noted that: the above examples are merely examples for clarity of illustration, and the present invention includes but is not limited to the above examples, which are not necessarily exhaustive of all embodiments. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. Embodiments that meet the requirements of the present invention are within the scope of the present invention.