An isolated transmission circuit compatible with PWM signals and analog signals

Abstract

The utility model provides a kind of compatible PWM signal and analog signal's isolated transmission circuit, including signal isolation transmission circuit, amplifier, the output end of signal isolation circuit is connected to the input end of the amplifier;It further includes triangular wave generator and signal comparison circuit, the PWM signal or analog signal to be isolated transmission is compared with the triangular wave generated by triangular wave generator in the signal comparison circuit after output, and then it is connected to the signal isolation transmission circuit;The pulse amplitude of the PWM signal to be isolated transmission is same with the amplitude of triangular wave.In the utility model, the pulse amplitude of the PWM signal to be isolated transmission is same with the amplitude of triangular wave, the PWM signal or analog signal to be isolated transmission is compared with the triangular wave generated by triangular wave generator in signal comparison circuit after output, if it is PWM signal then original signal output, if it is analog signal then modulate into another PWM signal and connect signal isolation transmission circuit.

Description

Technical Field

[0001] This utility model relates to the field of isolated transmission circuits, and in particular to an isolated transmission circuit compatible with both PWM signals and analog signals. Background Technology

[0002] In modern electrical products and equipment, PWM signals and analog signals are often transmitted through safety-compliant isolation circuits, highlighting the crucial role of these circuits. On one hand, safety circuits protect electrical products and equipment, extending their lifespan. On the other hand, they ensure user safety, preventing threats from high-voltage leakage, overload, and other situations. When voltage exceeds safe limits, external control circuits need to isolate and control circuits containing high-voltage components.

[0003] Safety certification here ensures the safety and quality of products for users and the environment, including product safety, electromagnetic compatibility (EMC), environmental protection, and energy certification. Safety testing, on the other hand, verifies the safety performance of products by simulating real-world usage scenarios, with the core objective of protecting users from risks such as electric shock, mechanical injury, and overheating.

[0004] Currently, PWM signals and analog signals are transmitted in isolation using isolation signals. Some even convert analog signals into PWM signals for transmission. For example, utility model patent announcement number CN 217985035 U discloses a circuit for implementing isolated transmission of analog signals. It converts the analog signal that needs to be isolated into a PWM signal and transmits it through optocoupler isolation. However, this circuit is not compatible with PWM optocoupler isolation and requires setting up another isolation transmission path for the PWM signal. Utility Model Content

[0005] This invention addresses the shortcomings of current optocoupler isolation transmission circuits that cannot be compatible with PWM signals and analog signals by providing an isolation transmission circuit that is compatible with both PWM signals and analog signals. This circuit isolates and transmits PWM signals and analog signals at different times.

[0006] The technical solution for achieving the technical objective of this utility model is: an isolated transmission circuit compatible with PWM signals and analog signals, including a signal isolation transmission circuit, an amplifier, the input terminal of which is connected to the output terminal of the signal isolation circuit; it also includes a triangular wave generator and a signal comparison circuit, wherein the PWM signal or analog signal to be isolated and transmitted is compared with the triangular wave generated by the triangular wave generator in the signal comparison circuit, and the output is then connected to the signal isolation transmission circuit; the pulse amplitude of the PWM signal to be isolated and transmitted is the same as the amplitude of the triangular wave.

[0007] Furthermore, in the aforementioned isolation transmission circuit compatible with PWM signals and analog signals: when the PWM signal or analog signal to be isolated and transmitted is input, a clamping circuit is also provided, which clamps the PWM signal or analog signal to be isolated and transmitted between the amplitudes of the triangular wave output by the triangular wave generator.

[0008] Furthermore, in the aforementioned isolated transmission circuit compatible with both PWM and analog signals, the triangular wave output by the triangular wave generator is between 0 and 5V.

[0009] Furthermore, in the aforementioned isolated transmission circuit compatible with both PWM and analog signals: the triangular wave generator includes operational amplifier U2A, operational amplifier U2B, and operational amplifier U2C; a resistor R6 is connected in series with the inverting input of operational amplifier U2A to the positive terminal of a 5V power supply, and simultaneously connected to ground through a resistor R11 and a capacitor C3; the non-inverting input of operational amplifier U2A is connected to both the non-inverting input of operational amplifier U2A and the output terminal of operational amplifier U2B through a resistor R1; the non-inverting input of operational amplifier U2A is connected to both the inverting input of operational amplifier U2B and the output terminal of operational amplifier U2A through a resistor R2 connected in series with a resistor R8 or a resistor R9.

[0010] The non-inverting input of operational amplifier U2B is connected to the inverting input of operational amplifier U2A; a capacitor C1 is placed between the inverting input and the output of operational amplifier U2B.

[0011] The inverting input and output of operational amplifier U2C are shorted together with a wire.

[0012] Furthermore, in the aforementioned isolated transmission circuit compatible with both PWM and analog signals: the clamping circuit is located at the input terminal of the PWM signal or analog signal, and includes two series diodes D1 connected between the +5V power supply signal line and ground. The cathode of one series diode D1 is connected to the +5V power supply, and the anode of the other series diode D1 is grounded.

[0013] Furthermore, the aforementioned isolated transmission circuit compatible with both PWM signals and analog signals also includes a resistor R12 and a capacitor C7; the resistor R12 is positioned between the +5V power supply signal line and the input signal line; and the capacitor C7 is positioned between the input signal line and ground.

[0014] Furthermore, in the aforementioned isolated transmission circuit compatible with PWM signals and analog signals: the signal comparison circuit includes an operational amplifier U2D, and the triangular wave signal generated by the triangular wave generator and the input signal after clamping at the input terminal are respectively connected to the inverting and non-inverting terminals of the operational amplifier U2D.

[0015] Furthermore, the aforementioned isolation transmission circuit compatible with PWM signals and analog signals also includes a front-end amplifier, which includes a transistor Q2; the output terminal of the operational amplifier U2D is connected to the base of the transistor Q2, the emitter of the transistor Q2 is connected to the signal isolation transmission circuit, and the collector is grounded.

[0016] Furthermore, in the aforementioned isolated transmission circuit compatible with PWM signals and analog signals: the signal isolation transmission circuit includes an optocoupler U1; the source pin 1 of the optocoupler U1 is connected to the +5V power supply signal line through a resistor R7, and the input signal after clamping is connected to the source pin 2 of the optocoupler U1.

[0017] Furthermore, in the aforementioned isolated transmission circuit compatible with both PWM and analog signals: the amplifier includes a transistor Q1; pin 4 of the output terminal of the optocoupler U1 is connected to the +5V power signal line and grounded through capacitor C6; pin 3 is connected to the base of transistor Q1 through resistor R10; the collector of transistor Q1 is connected to the +5V power signal line through resistor R5; the base of transistor Q1 is grounded through resistor R13; and the emitter is grounded.

[0018] It also includes an output filter, which includes resistor R4, resistor R3, capacitor C4, and capacitor C3; resistor R4 and capacitor C4 are connected in series between the collector and emitter of the transistor; resistor R3 and capacitor C3 are connected in series and then in parallel across capacitor C4.

[0019] In this invention, since the pulse amplitude of the PWM signal to be isolated and transmitted is the same as the amplitude of the triangular wave, after the PWM signal or analog signal to be isolated and transmitted is compared with the triangular wave generated by the triangular wave generator in the signal comparison circuit, if it is a PWM signal, the original signal is output; if it is an analog signal, it is modulated into another PWM signal and connected to the signal isolation transmission circuit.

[0020] The present invention will be described in more detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0021] Figure 1 This is a block diagram illustrating the principle of an isolated transmission circuit compatible with both PWM and analog signals, as described in Embodiment 1 of this utility model.

[0022] Figure 2 This is a schematic diagram of an isolated transmission circuit compatible with PWM signals and analog signals, as shown in Embodiment 1 of this utility model. Detailed Implementation

[0023] This embodiment is an isolated transmission circuit compatible with both PWM signals and analog signals, such as... Figure 1 and Figure 2As shown: In this embodiment, a triangular wave with an amplitude of 5V is first generated by a triangular wave generator. Then, a PWM signal or an analog circuit is input from the input interface. Here, the pulse amplitude of the PWM signal is 5V. After the two signals are compared in the comparison circuit, the PWM signal will not change, while the analog signal is modulated into a PWM signal. Then, it is transmitted to the back end through optocoupler isolation. The PWM signal output from the optocoupler is amplified and output at the back end. If it is a PWM signal modulated from an analog signal, it is output as an analog signal by filtering.

[0024] like Figure 1 and Figure 2 As shown, the isolated transmission circuit compatible with both PWM and analog signals in this embodiment can be divided into four functional modules, with the signal flow from right to left:

[0025] 1. Triangular wave oscillator circuit

[0026] It consists of operational amplifiers U2C and U2B, and resistors and capacitors R1, C1, R2, and C2, etc. Its core function is to generate a periodic triangular wave. In this embodiment, the amplitude of the triangular wave is between 0 and 5V.

[0027] The operational amplifier U2C outputs a stable triangular wave signal through RC charging and discharging and comparison feedback, providing a reference waveform for subsequent "signal comparison".

[0028] 2. Signal Comparison Circuit

[0029] Composed of operational amplifier U2D, optocoupler Q2, transistor Q2 and peripheral components, it compares analog signals with triangular waves to generate PWM signals.

[0030] The left signal input port CN1 receives analog signals or external PWM signals, processes them, and then compares them with a triangular wave sent to operational amplifier U2D.

[0031] The output level signal after comparison drives the optocoupler U1 to achieve electrical isolation to avoid interference between the preceding and following stages, and finally outputs the "prototype" of the PWM signal.

[0032] Here, after the PWM signal or analog signal is input, it is clamped to ensure that the amplitude of the PWM signal or analog signal to be transmitted is between 0V and +5V. The clamping circuit uses the unidirectional conduction characteristic of the diode. On the wire of the first pin of the input interface CN1, the diode D1 is connected to the +5V power supply line, and the diode is grounded. The P terminal of the diode is connected to the wire of the first pin of the interface CN1 or ground respectively.

[0033] Before entering isolation, a transistor Q2 is used for amplification. The front-end amplifier includes transistor Q2. The output of operational amplifier U2D is connected to the base of transistor Q2, the emitter of transistor Q2 is connected to the signal isolation transmission circuit, and the collector is grounded.

[0034] 3. Signal isolation transmission

[0035] Composed of optocoupler U1 (optical coupler), it is a key component for strong and weak current isolation.

[0036] The front-end PWM signal is transmitted from the "control side" to the "power side" through the "electro-optical-photoelectric" conversion of optocoupler U1, while disconnecting the electrical connection to prevent high voltage / high current from impacting the control circuit.

[0037] 4. Signal output filtering circuit

[0038] Composed of transistor Q1, resistors (R3, R4, R5, R10, R13), and capacitors (C4, C5, C6), its function is to filter the isolated PWM signal to obtain DC voltage.

[0039] After the PWM signal is amplified by Q1 and filtered by RC (C4, C5, R4, etc. constitute a low-pass filter), a smooth DC voltage is output, which can be used to drive subsequent loads such as power devices and sensors.

[0040] The output of optocoupler U1 is a PWM signal. After being amplified by an amplifier composed of transistor Q1, the restored PWM signal is output from the collector of transistor Q1. If the input from CN1 is a PWM signal, the PWM signal output from the collector of transistor Q1 is the PWM signal transmitted through the bandgap. If the input from CN1 is an analog signal, the analog signal is modulated into the PWM signal when compared with the triangular wave. At this time, the modulated signal PWM is output from the collector of transistor Q1. After passing through the subsequent filtering circuit, the analog signal is demodulated from the modulated PWM signal.

[0041] Overall logical summary

[0042] The core of the circuit in this embodiment is the process of "triangular wave generation → signal comparison to generate PWM → isolation transmission → filtered DC output", which realizes the conversion of "analog signal (or PWM) → isolated DC voltage". It is often used in power electronics, industrial control and other scenarios that require electrical isolation and signal conditioning, such as control circuits of switching power supplies and motor drives.

Claims

1. An isolated transmission circuit compatible with PWM signals and analog signals, comprising a signal isolation transmission circuit and an amplifier, wherein the input terminal of the amplifier is connected to the output terminal of the signal isolation circuit; characterized in that: It also includes a triangular wave generator and a signal comparison circuit. The PWM signal or analog signal to be isolated and transmitted is compared with the triangular wave generated by the triangular wave generator in the signal comparison circuit, and the output is then connected to the signal isolation transmission circuit. The pulse amplitude of the PWM signal to be isolated and transmitted is the same as the amplitude of the triangular wave.

2. The isolated transmission circuit compatible with PWM signals and analog signals according to claim 1, characterized in that: A clamping circuit is also provided when the PWM signal or analog signal to be isolated is input. The clamping circuit clamps the PWM signal or analog signal to be isolated between the amplitudes of the triangular wave output by the triangular wave generator.

3. The isolated transmission circuit compatible with PWM signals and analog signals according to claim 2, characterized in that: The triangular wave output by the triangular wave generator is between 0-5V.

4. The isolated transmission circuit compatible with PWM signals and analog signals according to claim 2, characterized in that: The triangular wave generator includes operational amplifiers U2A, U2B, and U2C. A resistor R6 is connected in series with the inverting input of operational amplifier U2A and connected to the positive terminal of a 5V power supply. Simultaneously, a resistor R11 and a capacitor C3 are connected in parallel to ground. The non-inverting input of operational amplifier U2A is connected to both the non-inverting input of operational amplifier U2A and the output terminal of operational amplifier U2B via a resistor R1. The non-inverting input of operational amplifier U2A is connected in series with either resistor R8 or resistor R9 via a resistor R2 and then connected to both the inverting input of operational amplifier U2B and the output terminal of operational amplifier U2A. The non-inverting input of operational amplifier U2B is connected to the inverting input of operational amplifier U2A; a capacitor C1 is placed between the inverting input and the output of operational amplifier U2B. The inverting input and output of operational amplifier U2C are shorted together with a wire.

5. The isolated transmission circuit compatible with PWM signals and analog signals according to claim 2, characterized in that: The clamping circuit is located at the input terminal of the PWM signal or analog signal, and includes two series diodes D1 connected between the +5V power signal line and ground. The cathode of one series diode D1 is connected to the +5V power supply, and the anode of the other series diode D1 is grounded.

6. The isolated transmission circuit compatible with PWM signals and analog signals according to claim 5, characterized in that: It also includes a resistor R12 and a capacitor C7; the resistor R12 is placed between the +5V power signal line and the input signal line; the capacitor C7 is placed between the input signal line and ground.

7. The isolated transmission circuit compatible with PWM signals and analog signals according to claim 2, characterized in that: The signal comparison circuit includes an operational amplifier U2D. The triangular wave signal generated by the triangular wave generator and the input signal after clamping at the input terminal are respectively connected to the inverting and non-inverting inputs of the operational amplifier U2D.

8. The isolated transmission circuit compatible with PWM signals and analog signals according to claim 7, characterized in that: It also includes a front-end amplifier, which includes a transistor Q2; the output terminal of the operational amplifier U2D is connected to the base of the transistor Q2, the emitter of the transistor Q2 is connected to a signal isolation transmission circuit, and the collector is grounded.

9. The isolated transmission circuit compatible with PWM signals and analog signals according to claim 8, characterized in that: The signal isolation transmission circuit includes an optocoupler U1; the source pin 1 of the optocoupler U1 is connected to the +5V power signal line through a resistor R7, and the input signal after clamping is connected to the source pin 2 of the optocoupler U1.

10. The isolated transmission circuit compatible with PWM signals and analog signals according to claim 9, characterized in that: The amplifier includes a transistor Q1. The output pin 4 of the optocoupler U1 is connected to the +5V power signal line and grounded through capacitor C6. The output pin 3 is connected to the base of transistor Q1 through resistor R10. The collector of transistor Q1 is connected to the +5V power signal line through resistor R5. The base of transistor Q1 is grounded through resistor R13, and the emitter is grounded. It also includes an output filter, which includes resistor R4, resistor R3, capacitor C4, and capacitor C3; resistor R4 and capacitor C4 are connected in series between the collector and emitter of the transistor; resistor R3 and capacitor C3 are connected in series and then in parallel across capacitor C4.

Images