PWM Demodulator Circuit Without Extra Clock Signals
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Solution Overview
Problem
Existing PWM demodulation technologies face issues with insufficient resolution, slow response times, significant output ripple, complex implementation, high bill-of-materials costs, and the need for additional clock signals, which hinder efficient demodulation of Pulse Width Modulated signals.
Innovation Solution
A circuit comprising a low pass filter, track-and-hold, and averaging circuits generates an output signal indicating the duty cycle of a PWM signal without requiring an additional clock signal, using a triangular signal produced by low-pass filtering and determining minimum and maximum values to produce an accurate output, thereby simplifying implementation and reducing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional PWM demodulation circuits are used, then demodulation function is achieved, but resolution is insufficient and output ripple is significant
Solution Approach 1:
The demodulation process is segmented into distinct functional blocks: a low-pass filter circuit for ripple reduction, a track-and-hold circuit for sampling, and an averaging circuit for precision enhancement. Each block performs a specific function to progressively improve resolution and reduce output ripple.
Solution Approach 2:
Multiple circuit functions are merged into integrated operational amplifier circuits. The low-pass filter, track-and-hold, and averaging functions are combined in a unified circuit architecture that uses operational amplifiers to simultaneously achieve ripple reduction and high-resolution demodulation without requiring separate discrete components for each function.
2Measurement precision
If high-resolution demodulation is achieved through traditional methods, then measurement precision improves, but device complexity increases and bill-of-materials cost increases
Solution Approach 1:
The operational amplifier circuits are designed to perform multiple functions simultaneously. Each op-amp circuit serves as a low-pass filter, track-and-hold circuit, and averaging circuit depending on the configuration, reducing the total number of components needed while maintaining high-resolution demodulation capability.
Solution Approach 2:
The circuit achieves high resolution by changing the time constant parameters of the low-pass filter and the sampling frequency of the track-and-hold circuit. By optimizing these parameters, the circuit achieves superior resolution without increasing complexity, as the same hardware operates with different parameter settings rather than requiring additional complex components.
3Speed
If traditional demodulation circuits are used, then PWM signal processing is achieved, but settling time is slow and response speed is insufficient
Solution Approach 1:
The track-and-hold circuit dynamically switches between tracking mode and hold mode based on the PWM signal edges. This dynamic operation allows the circuit to rapidly settle to the correct value on each PWM transition while maintaining accuracy during the hold phase, achieving both fast settling time and reliable response accuracy.
4Measurement precision
If additional clock signals are used for PWM demodulation, then demodulation accuracy improves, but device complexity increases and bill-of-materials cost increases
Solution Approach 1:
The circuit uses the PWM signal itself to control the track-and-hold switching and the averaging process. The PWM signal edges automatically trigger the sampling and holding operations, eliminating the need for external clock signals. The circuit serves itself by using its input signal to drive its own operation, maintaining high accuracy without additional complexity.
Data Source
AI summary
A simple, fast, easily designed circuit for demodulating a PWM signal produces an output signal indicating a duty cycle of a received PWM signal. The circuit may include a low pass filter circuit to receive a Pulse Width Modulated (PWM) signal and produce a triangular signal, a track-and-hold circuit to receive the PWM signal and the triangular signal and produce a minimum and maximum signals corresponding to minimum and maximum values of the triangular signal during each cycle of the PWM signal, and an averaging circuit to receive the minimum signal and the maximum signal and produce, by averaging the values of the minimum signal and the maximum signal, the output signal.