Photoelectric coupler wide voltage input interface circuit based on current limiting design

Abstract

The utility model relates to a photoelectric coupler wide voltage input interface circuit based on current limiting design. The photoelectric coupler wide voltage input interface circuit comprises a PNP triode current limiting circuit, an input filter, an interface protection circuit, an anti-reverse connection circuit and a photoelectric coupler isolation circuit. The input filter is connected with an input power supply and is used for filtering clutters in the input power supply; the interface protection circuit is connected behind the input filter and is used for preventing static electricity and surge from damaging the circuit; after the PNP triode current-limiting circuit is connected to the interface protection circuit, the PNP triode current-limiting circuit is used for limiting the current flowing through the photoelectric coupler in a set wide input voltage range and preventing the photoelectric coupler from being damaged by overcurrent. According to the utility model, a wide voltage control signal is subjected to filtering, anti-reverse connection protection and current limiting and then is isolated by the photoelectric coupler to send an isolation control signal, so that the level of the control signal in a wide voltage range can be adapted, the applicability of equipment is improved, and the circuit is simple in design, few in used components and low in cost.

Description

Technical Field

[0001] This application belongs to the technical field of optocoupler interface circuits, and particularly relates to a wide-voltage input interface circuit of an optocoupler based on current-limiting design. Background Art

[0002] An optocoupler is a device that converts an optical signal into an electrical signal or an electrical signal into an optical signal. Its input terminal is usually a light-emitting diode (LED), and the output terminal is a photosensitive device (such as a photosensitive triode, a photosensitive resistor, etc.). When an electric voltage is applied to the input terminal, the LED emits light, and the light irradiates the photosensitive device to generate a photocurrent, thereby realizing the conversion from an electrical signal to an optical signal and then to an electrical signal. In the prior art, an optocoupler usually has difficulty in operating stably within a wide voltage range. The main reason is that the current is likely to be too large at a high input voltage, which may cause damage to the optocoupler. To solve this problem, traditional designs require complex voltage regulators or additional current-limiting resistors, but these solutions increase the complexity and cost of the design. Content of the Utility Model

[0003] The technical problem to be solved by this utility model is: to solve the deficiencies in the prior art, and thus provide a wide-voltage input interface circuit of an optocoupler based on current-limiting design, which realizes current limiting through two PNP triodes to ensure the stable operation of the optocoupler under a wide range of input voltages, thereby solving the above technical problems.

[0004] The technical solution adopted by this utility model to solve its technical problems is:

[0005] A wide-voltage input interface circuit of an optocoupler based on current-limiting design includes a PNP triode current-limiting circuit, an input filter, an interface protection circuit, an anti-reverse connection circuit, and an optocoupler isolation circuit;

[0006] The input filter is connected to the input power supply and is used to filter out the clutter in the input power supply;

[0007] The interface protection circuit is connected after the input filter and is used to prevent the damage of the circuit caused by static electricity and surges;

[0008] The PNP triode current-limiting circuit is connected after the interface protection circuit. The PNP triode current-limiting circuit is used to limit the current flowing through the optocoupler within a set wide input voltage range to prevent overcurrent damage to the optocoupler;

[0009] The anti-reverse connection circuit is arranged after the PNP triode current-limiting circuit and is used to avoid the damage of the circuit caused by reverse connection of the power supply;

[0010] The optocoupler isolation circuit is arranged after the anti-reverse connection circuit. The output terminal of the optocoupler is connected to the peripheral circuit and is used to realize the isolated transmission of signals.

[0011] Preferably, for a wide-voltage input interface circuit of an optocoupler based on current-limiting design of the present utility model, the input filter includes at least two parallel filter capacitors C1 and C2 for filtering high-frequency noise and interference at the power input terminal.

[0012] Preferably, for a wide-voltage input interface circuit of an optocoupler based on current-limiting design of the present utility model, the interface protection circuit includes at least two parallel electrostatic and surge protection diodes D1 and D2.

[0013] Preferably, for a wide-voltage input interface circuit of an optocoupler based on current-limiting design of the present utility model, the PNP transistor current-limiting circuit includes PNP transistors Q1, Q2, resistors R1, R2, R3, R4 and a power supply. The emitter of PNP transistor Q1 is connected to VIN+, a resistor R1 is connected in parallel between the emitter and the base of PNP transistor Q1, the collector of PNP transistor Q1 is connected to resistor R2, the base of PNP transistor Q2 and VIN- are respectively connected to both ends of resistor R3, and the emitter of PNP transistor Q2 and VIN+ are respectively connected to both ends of resistor R4.

[0014] Preferably, for a wide-voltage input interface circuit of an optocoupler based on current-limiting design of the present utility model, the optocoupler isolation circuit includes an optocoupler chip and its peripheral circuit for realizing electrical isolation transmission of signals.

[0015] The beneficial effects of the present utility model are as follows:

[0016] The wide-voltage input interface circuit of the optocoupler of the present utility model realizes current-limiting protection through two PNP transistors. When the input voltage increases, the PNP transistors automatically adjust their working states to limit the current flowing through the optocoupler and keep it within a safe range, thereby ensuring the stable operation of the optocoupler within a wide input voltage range.

[0017] The wide-voltage control signal of the present utility model passes through filtering, reverse-connection protection and current-limiting, and then is isolated and sent through the optocoupler to enable the level of the control signal adaptable to a wide voltage range, thereby improving the applicability of the device. Moreover, the circuit design is simple, with fewer components used and low cost. Description of the Drawings

[0018] The technical solutions of the present application will be further described below with reference to the drawings and embodiments.

[0019] Figure 1 is a schematic block diagram of the circuit principle of the wide-voltage input interface circuit of the optocoupler in the embodiment of the present application;

[0020] Figure 2 It is a circuit schematic diagram of the wide-voltage input interface circuit of the optocoupler (when the PNP transistor current-limiting circuit is not included);

[0021] Figure 3 It is a circuit structure schematic diagram of the PNP transistor current-limiting circuit of the embodiment of the present application. Specific Embodiments

[0022] It should be noted that, without conflict, the embodiments in the present application and the features in the embodiments may be combined with each other.

[0023] In the description of the present application, it should be understood that the orientation or positional relationship indicated by the terms "center", "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as limiting the protection scope of the present application. In addition, the terms "first", "second", etc. are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, the features defined with "first", "second", etc. may explicitly or implicitly include one or more of such features. In the description of the present invention, unless otherwise specified, the meaning of "plurality" is two or more.

[0024] In the description of the present application, it should be noted that, unless otherwise clearly specified and limited, the terms "mounted", "connected", "coupled" should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or an integral connection; it may be a mechanical connection or an electrical connection; it may be directly connected, or indirectly connected through an intermediate medium, and it may be the internal communication of two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood through specific situations.

[0025] The technical solutions of the present application will be described in detail below with reference to the drawings and in combination with the embodiments.

[0026] Embodiment

[0027] This embodiment provides a wide-voltage input interface circuit of an optocoupler based on current-limiting design, as Figure 1As shown, it includes an input filter, an interface protection circuit, a PNP transistor current limiting circuit, an anti-reverse connection circuit, and an isolation circuit including an optocoupler chip, which are connected in sequence. The I / O terminals of the input filter are respectively connected to the input power supply Ui n and the interface protection circuit. In this embodiment, the voltage range is +5V to +24V (the voltage range is related to the parameter selection in the circuit, and the theoretical voltage can be selected very high). The PNP transistor current limiting circuit is connected to the output terminal of the interface protection circuit. The I / O terminals of the anti-reverse connection circuit are respectively connected to the PNP transistor current limiting circuit and the optocoupler isolation circuit, and the output terminal of the optocoupler isolation circuit is connected to the peripheral circuit.

[0028] Combined with Figure 2 As shown, in this embodiment, the input filter includes parallel filter capacitors C1 and C2; the interface protection circuit is set as parallel electrostatic and surge protection (TVS / ESD) diodes D1 and D2; the anti-reverse connection circuit uses a parallel switching diode D3; the optocoupler chip isolation circuit mainly includes an input power supply filter capacitor C3 and an optocoupler chip U1, and the optocoupler chip U1 can be selected with the model TLP2355.

[0029] It should be noted that the input filter, the interface protection circuit, the anti-reverse connection circuit, and the optocoupler isolation circuit adopt existing technologies, and their specific structures and working principles will not be further described here. The main innovation of this embodiment is to add a current limiting circuit composed of two PNP transistors on the basis of the original current limiting resistor.

[0030] Specifically, combined with Figure 3 As shown, the specific circuit of the PNP transistor current limiting circuit. The emitter of the PNP transistor Q1 is connected to VI N+ (the positive pole of the power supply). A resistor R1 is connected in parallel between the emitter and the base of the PNP transistor Q1. A resistor R2 is connected between the collector of the transistor Q1 and the base of the PNP transistor Q2. Both ends of the resistor R3 are respectively connected to the base of the PNP transistor Q2 and VI N- (the negative pole of the power supply). Both ends of the resistor R4 are respectively connected to the emitter of the PNP transistor Q2 and VI N+.

[0031] The working principle of the above overcurrent protection circuit is as follows: The working principle of this current limiting protection circuit is based on a negative feedback regulation mechanism for controlling current. When the input voltage VI N is low, the current flowing through the resistor R1 is small, resulting in a voltage drop insufficient to turn on the transistor Q1. At this time, Q1 is in the off state. Due to the pull-down effect of the resistor R3, the base potential of the transistor Q2 is close to the ground potential, resulting in Q2 being in a nearly fully conductive state. At this time, the current is mainly limited by the resistors R1 and R4.

[0032] As the input voltage VIN gradually increases, the current flowing through resistor R1 increases, resulting in an increased voltage drop across R1. When this voltage drop reaches the conduction threshold of transistor Q1, Q1 begins to conduct, and part of the current flows through Q1 to resistor R3, thereby increasing the base voltage of Q2 and causing Q2 to transition from the conducting state to the cut-off state. As Q2 approaches cut-off, the current flowing through R1 gradually decreases, leading to a decrease in the voltage drop across R1, and then Q1 gradually turns off, reducing the base voltage of Q2 and causing Q2 to enter the conducting state again.

[0033] This process is actually an automatic adjustment balance formed through negative feedback, ensuring that both Q1 and Q2 are in the linear amplification state, thus maintaining the stability of the current. Through this feedback mechanism, the circuit can dynamically adjust the current to prevent overcurrent. Since transistor Q1 operates in the amplification state, the current flowing through the load can basically remain unchanged. The voltage across R1 is approximately equal to the conduction voltage of transistor Q1. Then the current of this circuit is mainly determined by R1 and the conduction voltage of transistor Q1, which is:

[0034] I = Vbe / R1

[0035] It can be seen that the PNP transistor current limiting circuit disclosed in this application uses the negative feedback mechanism to limit the current of the overall circuit to about I = Vbe / R1 when the input voltage changes. And the transistor and resistor parameters can be flexibly adjusted according to the actual input voltage change range to control the circuit current.

[0036] Taking the above ideal embodiment based on this application as an inspiration, through the above description, relevant staff can completely make various changes and modifications without departing from the technical idea of this application. The technical scope of this application is not limited to the content in the specification, and its technical scope must be determined according to the scope of the claims.

Claims

1. A wide-voltage input interface circuit of an optocoupler based on current-limiting design, characterized in that It includes a PNP transistor current limiting circuit, an input filter, an interface protection circuit, an anti-reverse connection circuit, and an optocoupler isolation circuit; The input filter is connected to the input power supply and is used to filter out the clutter in the input power supply; The interface protection circuit is connected after the input filter and is used to prevent the damage of static electricity and surges to the circuit; The PNP transistor current limiting circuit is connected after the interface protection circuit. The PNP transistor current limiting circuit is used to limit the current flowing through the optocoupler within a set wide input voltage range; The anti-reverse connection circuit is arranged after the PNP transistor current limiting circuit and is used to avoid the circuit damage caused by the reverse connection of the power supply; The optocoupler isolation circuit is arranged after the anti-reverse connection circuit. The output end of the optocoupler is connected to the peripheral circuit.

2. The wide-voltage input interface circuit of an optocoupler based on current-limiting design according to claim 1, wherein The input filter includes at least two parallel filter capacitors C1 and C2 and is used to filter out the high-frequency noise and interference at the power input end.

3. The wide-voltage input interface circuit of an optocoupler based on current-limiting design according to claim 2, characterized in that, The interface protection circuit includes at least two parallel static electricity and surge protection diodes D1 and D2.

4. A wide-voltage input interface circuit of an optocoupler based on current-limiting design according to any one of claims 1 to 3, characterized in that, The PNP transistor current limiting circuit includes PNP transistors Q1, Q2, resistors R1, R2, R3, R4, and a power supply. The emitter of the PNP transistor Q1 is connected to VIN+. A resistor R1 is connected in parallel between the emitter and the base of the PNP transistor Q1. The collector of the PNP transistor Q1 is connected to the resistor R2. The base of the PNP transistor Q2 and VIN- are respectively connected to both ends of the resistor R3. The emitter of the PNP transistor Q2 and VIN+ are respectively connected to both ends of the resistor R4.

5. The wide-voltage input interface circuit of an optocoupler based on current-limiting design according to claim 4, characterized in that, The optocoupler isolation circuit includes an optocoupler chip and its peripheral circuit.

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