Bidirectional signal isolation transmission circuit with automatic switching function

Abstract

The utility model provides a bidirectional signal isolation transmission circuit with an automatic switch function. The bidirectional signal isolation transmission circuit comprises an automatic switch control circuit and a signal transmission circuit. According to the utility model, bidirectional signal transmission control is realized through the general transistors, the diodes and the resistors. By adopting the automatic switch control circuit, a special control signal is omitted, and the switch can be automatically turned on in a signal transmission state; under the state of no signal transmission, the switch can be automatically turned off. By adopting the signal transmission circuit, an internal signal and an external signal are isolated through a transistor, so that an internal device is protected from being interfered by the external signal, and meanwhile, level conversion between the internal signal and the external signal is realized.

Description

TECHNICAL FIELD

[0001] The utility model relates to electrical element technical field, concretely relates to a two -way signal isolation transmission circuit with automatic switch function. BACKGROUND

[0002] In the low-voltage, low-frequency digital signal design field, especially in the product design of module level, the TTL signal is often used for signal transmission between modules. Due to the difference between signal level and driving capacity between modules, in order to solve this problem, a special integrated circuit (bus buffer) is used for signal isolation and transmission between modules, and the "switch function pin" and "direction function pin" of the bus buffer are controlled by the processor in the module.

[0003] When there is signal transmission, first, the transmission direction of the signal is determined by negotiating through other signal pins between modules, then the direction is selected by the "direction function pin" of the bus buffer controlled by the processor, then the "switch function pin" of the bus buffer is enabled by the processor, and finally the signal transmission is performed.

[0004] When there is no signal transmission, first, the signal transmission is determined to be completed by negotiating through other signal pins between modules, and then the "switch function pin" of the bus buffer is closed by the processor.

[0005] From the above analysis, it can be seen that the existing bus buffer technology has obvious shortcomings:

[0006] (1) The transmission mechanism is complicated. When signal transmission, additional "switch function pin" and "direction function pin" are needed, and transmission negotiation is needed, which increases the software development work.

[0007] (2) Cost. The cost of bus buffer is one order of magnitude higher than that of ordinary transistor, diode and resistor, and when using bus buffer, the processor in the module needs to detect whether there is signal transmission demand in real time, which inevitably increases the module power consumption.

[0008] Therefore, a switch control circuit with appropriate transmission mechanism and low power consumption is needed. SUMMARY

[0009] The utility model discloses in order to solve the problem of signal transmission mechanism complicated, cost high, provide a kind of two-way signal isolation transmission circuit with automatic switch function, pass through general transistor, diode and resistance, realize two-way signal transmission control.

[0010] The utility model provides a kind of two-way signal isolation transmission circuit with automatic switch function, including the automatic switch control circuit and signal transmission circuit of connection;

[0011] Automatic switch control circuit includes the transistor Q1 of source ground, the resistance R1 being connected with the drain electrode of transistor Q1, the resistance R2, the resistance R3, the resistance R4 being respectively connected with resistance R1 one end, the diode V1 of positive pole simultaneously connecting resistance R2 and transistor Q1 gate, negative pole connecting resistance R3, the diode V2 of positive pole simultaneously connecting resistance R2 and transistor Q1 gate, negative pole connecting resistance R4, the transistor Q2 of drain electrode and resistance R3 being connected and the transistor Q3 of drain electrode and resistance R4 being connected;

[0012] Resistance R1, resistance R2, resistance R3 and resistance R4 are connected with power supply voltage VCC, resistance R2 is connected with transistor Q1 gate, diode V1 negative pole is simultaneously connected with resistance R3 and transistor Q2 drain electrode, diode V2 negative pole is simultaneously connected with resistance R4 and transistor Q3 drain electrode, transistor Q2 gate is connected with transistor Q3 source, transistor Q2 source is connected with transistor Q3 gate;

[0013] Signal transmission circuit includes transistor Q4 and transistor Q5,

[0014] Transistor Q4 source is connected with transistor Q5 source, transistor Q4 drain electrode is connected with transistor Q5 drain electrode;

[0015] Signal S A Transistor Q4 source, transistor Q5 source are simultaneously connected, also be connected in transistor Q2 gate;Signal S B Transistor Q4 drain electrode, transistor Q5 drain electrode are simultaneously connected, also be connected in transistor Q3 gate;

[0016] Control signal C A Be connected in transistor Q1 drain electrode, also be connected in transistor Q4 gate, control signal C B Be connected in transistor Q1 gate, also be connected in transistor Q5 gate;

[0017] The transistor Q1, the transistor Q2, the transistor Q3 and the transistor Q4 are NMOS type transistors, and the transistor Q5 is a PMOS type transistor.

[0018] The two-way signal isolation transmission circuit with the automatic switch function, as a preferred mode, the diode V1 and the diode V2 are both Schottky diodes or switching diodes.

[0019] The two-way signal isolation transmission circuit with the automatic switch function, as a preferred mode, the resistor R1, the resistor R2, the resistor R3 and the resistor R4 are all pull-up resistors.

[0020] The utility model discloses a circuit is composed of automatic switch control circuit and signal transmission circuit. Compared with traditional signal transmission and control that realizes by special integrated circuit, this circuit realizes two-way signal transmission control through general transistor, diode and resistance. Through the automatic switch control circuit, the special control signal is omitted, and in the state of signal transmission, the switch will automatically open. In the state of no signal transmission, the switch will automatically close. Through the signal transmission circuit, the internal signal and the external signal are isolated through the transistor, so that the internal device is protected from the interference of the external signal, and the level conversion between the internal signal and the external signal is realized.

[0021] The utility model has the following advantages:

[0022] (1), compared with the traditional technology, the automatic switch control circuit is adopted in this circuit, the transmission demand and transmission direction of signal can be automatically identified, and the software development work is omitted without the consultation between modules.

[0023] (2), through the automatic switch control circuit, the signal transmission needs real-time monitoring of special circuit, so as to reduce the module power consumption.

[0024] (3), through the general device, the signal automatic transmission is realized, and the design cost is greatly saved. DRAWINGS

[0025] Figure 1 It is an automatic switch control circuit principle diagram of a two-way signal isolation transmission circuit with automatic switch function;

[0026] Figure 2 It is a signal transmission circuit principle diagram of a two-way signal isolation transmission circuit with automatic switch function. PREFERRED EMBODIMENT

[0027] Clearly, the described embodiments are merely a part of the embodiments of the present utility model, rather than all the embodiments.

[0028] Embodiment 1

[0029] As shown in Figure 1 , 2 , a bidirectional signal isolation transmission circuit with automatic switching function, comprising automatic switching control circuit and signal transmission circuit. Automatic switching control circuit comprises transistor Q1, transistor Q2, transistor Q3, diode V1, diode V2, resistor R1, resistor R2, resistor R3 and resistor R4; signal transmission circuit comprises transistor Q4, transistor Q5.

[0030] The transistor in the automatic switching control circuit is an NMOS transistor.

[0031] The diode in the automatic switching control circuit is a Schottky diode.

[0032] The resistance in the automatic switching control circuit is a pull-up resistance, and the resistance value is 4.7KΩ or 10KΩ.

[0033] The transistor Q4 in the control signal transmission circuit is an NMOS transistor, and the transistor Q5 is a PMOS transistor.

[0034] The device of the present utility model mainly consists of two modules-automatic switching control circuit and signal transmission circuit, and the working principle schematic diagram is shown in Figure 1 , 2 .

[0035] The automatic switching control circuit is mainly used for realizing automatic detection during signal transmission, and simultaneously controlling the opening or closing of the signal transmission circuit; the signal transmission circuit is mainly used for realizing the isolation and transmission of internal signals and external signals.

[0036] The working principle of the present utility model is as follows:

[0037] Signal transmission process. Since the internal signal and the external signal are completely symmetrical, only the one-way transmission working principle is described. In the field of digital signals, high level represents "1", and low level represents "0", and the specific process is as follows:

[0038] Assuming that the initial state signal S A =S B =0, both are low level. When S A =1, transistor Q2 is turned on, control signal C B is set to "0" through diode V1, and control signal C A is control signal C BThe inversion of the control signal C A The value is "1". At this time, transistor Q5 is turned on, and S... A To conduct S B Charging, finally S A =S B =1, indicating a high level.

[0039] Assume signal S A =S B =1, both are high level. When S A =0, transistor Q3 is turned on, control signal C B The control signal C is set to low level by diode V2. A For control signal C B The inversion of the control signal C A The value is "1". At this time, transistor Q4 is turned on, and S... B To conduct S A Discharge, finally S A =S B =0, which indicates a low level.

[0040] Shutdown process. After signal transmission is complete, S... A =S B Transistors Q2 and Q3 are both turned off, and the control signal C... B When the signal is high, the control signal C A The signal is at a high level, at which point transistors Q4 and Q5 are both turned off, and signal S... A and S B It is in a state of isolation.

[0041] Furthermore, signal S A and S B The high-level values ​​can be different, but the absolute value of the difference between the two must be less than the threshold voltages of transistors Q2 and Q3.

[0042] The above description is only a preferred embodiment of the present utility model, but the protection scope of the present utility model is not limited thereto. Any equivalent substitutions or changes made by those skilled in the art within the technical scope disclosed in the present utility model, based on the technical solution and the inventive concept of the present utility model, should be included within the protection scope of the present utility model.

Claims

1. A bidirectional signal isolation transmission circuit with automatic switching function, characterized in that: This includes the connected automatic switch control circuit and signal transmission circuit; The automatic switch control circuit includes a transistor Q1 with its source grounded, a resistor R1 connected to the drain of transistor Q1, resistors R2, R3, and R4 connected to one end of resistor R1 respectively, a diode V1 with its positive terminal connected between resistor R2 and the gate of transistor Q1 and its negative terminal connected to resistor R3, a diode V2 with its positive terminal connected to both resistor R2 and the gate of transistor Q1 and its negative terminal connected to resistor R4, a transistor Q2 with its drain connected to resistor R3, and a transistor Q3 with its drain connected to resistor R4. Resistors R1, R2, R3, and R4 are all connected to the power supply voltage VCC. Resistor R2 is connected to the gate of transistor Q1. The cathode of diode V1 is connected to both resistor R3 and the drain of transistor Q2. The cathode of diode V2 is connected to both resistor R4 and the drain of transistor Q3. The gate of transistor Q2 is connected to the source of transistor Q3. The source of transistor Q2 is connected to the gate of transistor Q3. The signal transmission circuit includes transistor Q4 and transistor Q5, with the source of transistor Q4 connected to the source of transistor Q5 and the drain of transistor Q4 connected to the drain of transistor Q5. Signal S A Simultaneously connected to the source of transistor Q4, the source of transistor Q5, and also connected to the gate of transistor Q2; signal S B It is connected to the drain of transistor Q4, the drain of transistor Q5, and also to the gate of transistor Q3; Control signal C A It is connected to the drain of transistor Q1 and also to the gate of transistor Q4, with control signal C. B It is connected to the gate of transistor Q1 and also to the gate of transistor Q5; Transistors Q1, Q2, Q3, and Q4 are all NMOS transistors, while transistor Q5 is a PMOS transistor.

2. The bidirectional signal isolation transmission circuit with automatic switching function according to claim 1, characterized in that: Both diodes V1 and V2 are Schottky diodes or switching diodes.

3. The bidirectional signal isolation transmission circuit with automatic switching function according to claim 1, characterized in that: Resistors R1, R2, R3, and R4 are all pull-up resistors.

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