CN-122001346-A - Circuit for converting analog signal into PWM signal

Abstract

A circuit for converting analog signals into PWM signals belongs to the technical field of signal transmission application. The device comprises a precise sawtooth wave generating circuit and a signal comparison circuit, wherein the precise sawtooth wave generating circuit provides a sawtooth wave signal with precisely determined waveform amplitude, and the signal comparison circuit compares the sawtooth wave signal with an analog input voltage signal and generates a PWM signal with the duty ratio linearly related to the amplitude of the analog voltage signal. The method has the advantages that the generated sawtooth wave has high linearity, the amplitude variation range can be accurately controlled between 0 and reference voltage VREF, a stable reference is provided for high-precision comparison, the duty ratio of an output PWM signal and the amplitude of an input analog voltage are in a strict linear relation in a range, the accuracy of signal conversion is ensured, the duty ratio of the generated PWM signal can be continuously adjustable in a full range of 0-100%, no adjusting blind area in a traditional circuit is avoided, and the dynamic range and the applicability of the signal are improved.

Inventors

• WU ZHENGYANG
• ZHU YAN

Assignees

• 苏州工学院

Dates

Publication Date

20260508

Application Date

20260127

Claims (6)

1. 1. A circuit for converting an analog signal into a PWM signal is characterized by comprising a precise sawtooth wave generating circuit and a signal comparison circuit, wherein the precise sawtooth wave generating circuit provides a sawtooth wave signal with precisely determined waveform amplitude, and the signal comparison circuit compares the sawtooth wave signal with an analog input voltage signal and generates a PWM signal with a duty ratio linearly related to the amplitude of the analog voltage signal.
2. 2. The circuit for converting an analog signal into a PWM signal according to claim 1, wherein said precision sawtooth wave generating circuit comprises a constant current source circuit, a voltage reference source circuit and a sawtooth wave generation control circuit, said constant current source circuit providing a current for charging an integrating capacitor, said voltage reference source providing a reference voltage for defining a sawtooth wave generation control circuit for controlling the amplitude of a sawtooth wave, said sawtooth wave generation control circuit for generating a sawtooth wave control signal with a controlled amplitude.
3. 3. The circuit for converting analog signals into PWM signals according to claim 2, wherein the constant current source circuit comprises diodes D1 and D2, resistors R1 and R2 and a triode Q1, wherein the anode of the diode D1 and one end of the resistor R1 are commonly connected with a direct current power supply VCC, the cathode of the diode D1 is connected with the anode of the diode D2, the cathode of the diode D2 is connected with the base of the triode Q1 and one end of the resistor R2, the emitter of the triode Q1 is connected with the other end of the resistor R1, the collector of the triode Q1 is connected with an integrating capacitor in the sawtooth wave generation control circuit, and the other end of the resistor R2 is connected with a direct current power supply GND.
4. 4. The circuit for converting analog signals to PWM signals according to claim 2, wherein said voltage reference source circuit comprises a resistor R4, a capacitor C5 and a parallel voltage stabilizing integrated chip U2, said parallel voltage stabilizing integrated chip U2 is TL431, one end of said resistor R4 is connected with a DC power supply VCC, the other end of said resistor R4 is connected with one end of said capacitor C5 and 1 and 2 pins of said parallel voltage stabilizing integrated chip U2, and outputs a reference voltage VREF, and the 3 pins of said parallel voltage stabilizing integrated chip U2 and the other end of said capacitor C5 are commonly connected with a DC power supply ground GND.
5. 5. The circuit for converting analog signals to PWM signals according to claim 3, wherein said sawtooth wave generation control circuit comprises resistors R3, R5, a diode D3, capacitors C1, C2, C3, C4, an analog switch chip U1 and a voltage comparator U3A, wherein said analog switch chip U1 employs SGM3157, said voltage comparator U3A employs LM393, said capacitor C1 is said integrating capacitor, a 1 pin of the voltage comparator U3A is connected with one end of a resistor R3 and an anode of a diode D3, a cathode of the diode D3 is connected with one end of a capacitor C2, one end of a resistor R5 and a 6 pin of the analog switch chip U1, a 2 pin of the voltage comparator U3A is connected with a reference voltage VREF, a 3 pin of the voltage comparator U3A is connected with one end of the analog switch chip U1 and one end of the capacitor C1, and is commonly connected to a 5 pin of the analog switch chip U1 in said circuit, one end of the capacitor C3 is connected with one end of the capacitor C3, a collector of the capacitor C4, and the other end of the capacitor C3A is commonly connected with the other end of the capacitor C1, and the other end of the capacitor C3 is commonly connected with the other end of the capacitor C3, and the other end of the capacitor C1 is commonly connected with the resistor C3, and the capacitor C2 is commonly connected with the other end of the capacitor C3.
6. 6. The circuit for converting analog signals into PWM signals according to claim 3, wherein the signal comparison circuit comprises resistors R6-R8, a connector H1, a connector H2 and a voltage comparator U3B, wherein the voltage comparator U3B is LM393, the 5 pin of the voltage comparator U3B is connected with one end of a resistor R7 and one end of a resistor R8, the other end of the resistor R7 is connected with the 2 pin of the connector H1 and is used for introducing analog input voltage signals Vin, the 6 pin of the voltage comparator U3B is connected with a collector of a triode Q1 in the constant current source circuit, the 7 pin of the voltage comparator U3B is connected with one end of the resistor R6 and the 2 pin of the connector H2 and is used for outputting PWM signals after signal comparison, and the other end of the resistor R6 is connected with a direct current power supply GND together with the 1 pin of the connector H1, the 1 pin of the connector H2 and the other end of the resistor R8.

Description

Circuit for converting analog signal into PWM signal Technical Field The invention belongs to the technical field of signal transmission application, and particularly relates to a circuit for converting an analog signal into a PWM signal. Background In the process of remote transmission or isolated transmission, the analog signals are easy to interfere due to the characteristic of continuous change, so that the fidelity of the signals is reduced and the stability is insufficient. Particularly in the practical application of the isolation transmission of the analog signals, if the analog signals are directly processed and transmitted, the requirements on the precision and the stability of circuit elements are harsh, and the problems that the circuit structure is complex, the isolation transmission precision is difficult to guarantee and the like are caused. In order to overcome the defects, the prior analog signal isolation transmission mainly adopts an analog-digital hybrid transmission scheme, and the basic principle is that an analog signal to be transmitted is firstly converted into a digital signal or a digital modulation signal, and then the digital signal is recovered into an original analog signal after isolation transmission. In the process, the conversion from analog signals to digital signals is a key link, and the transmission precision, the anti-interference capability and the overall stability of the system are directly determined. The existing signal analog-digital transmission scheme mainly adopts modes such as an A/D converter or voltage-frequency (V/F) conversion, however, the problems of complex circuit and high cost of the methods generally exist. As a potential alternative, pulse Width Modulation (PWM) technology, the equivalent voltage of a constant frequency PWM signal is directly determined by the duty cycle and amplitude of the signal. Based on this, converting an analog signal into a precise PWM signal having a duty cycle that is linear with the input voltage can be regarded as an effective analog-to-digital conversion approach. However, the traditional PWM-based conversion circuit still has the defects of complex structure, dead zone in the duty ratio adjusting range, limited conversion precision and the like. Therefore, it is necessary to develop a special circuit that can convert an analog voltage signal into a PWM signal with a variable duty ratio that is linearly related thereto, and improve the accuracy of transmission and reception while reducing the cost of the circuit by optimizing the design. The technical solutions to be described below are created in this context. Disclosure of Invention The invention aims to provide a circuit for converting an analog signal into a PWM signal, which has a simple and reasonable structure and low cost, and can realize high-precision linear conversion between an input analog voltage signal and an output PWM signal duty ratio. The invention aims at achieving the aim, and provides a circuit for converting an analog signal into a PWM signal, which comprises a precise sawtooth wave generating circuit and a signal comparison circuit, wherein the precise sawtooth wave generating circuit provides a sawtooth wave signal with precisely determined waveform amplitude, and the signal comparison circuit compares the sawtooth wave signal with an analog input voltage signal and generates the PWM signal with the duty ratio linearly related to the amplitude of the analog voltage signal. In a specific embodiment of the present invention, the precision sawtooth wave generating circuit includes a constant current source circuit, a voltage reference source circuit, and a sawtooth wave generating control circuit, wherein the constant current source circuit provides a current for charging an integrating capacitor, the voltage reference source provides a reference voltage for limiting and controlling the amplitude of the sawtooth wave for the sawtooth wave generating control circuit, and the sawtooth wave generating control circuit generates a sawtooth wave control signal with controlled amplitude. In another specific embodiment of the present invention, the constant current source circuit includes diodes D1 and D2, resistors R1 and R2, and a triode Q1, where an anode of the diode D1 and one end of the resistor R1 are commonly connected to a dc power VCC, a cathode of the diode D1 is connected to an anode of the diode D2, a cathode of the diode D2 is connected to a base of the triode Q1 and one end of the resistor R2, an emitter of the triode Q1 is connected to the other end of the resistor R1, a collector of the triode Q1 is connected to an integrating capacitor in the sawtooth wave generating control circuit, and the other end of the resistor R2 is connected to a dc power ground GND. In another specific embodiment of the present invention, the voltage reference source circuit includes a resistor R4, a capacitor C5, and a shunt regulator integrated chip U2, where