Variable Ramp PWM Circuit for Full-Range Duty Ratio Control
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Solution Overview
Problem
Conventional PWM signal generation circuits have limited control over duty ratio, particularly failing to provide flexible and full-range operation for dynamic and precise control of DC motor rotation speed, as they rely on a single controllable parameter (input voltage level) and are restricted by the fixed slope and amplitude of ramp signals.
Innovation Solution
A PWM signal generation circuit with a variable ramp signal generation capability, allowing adjustable slope and amplitude of the ramp signal, enabling precise control of duty ratio through a comparator circuit that compares a reference signal with a variable ramp signal having a fixed peak level and adjustable rising and falling slopes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the level of the input voltage Vin is adjusted to change the duty ratio of the PWM signal, then the duty ratio can be controlled, but the control is limited to a linear adjustment range and cannot provide full-range operation
Solution Approach 1:
The patent changes the controllable parameters from only the reference signal level (input voltage Vin) to include both the reference signal level and the ramp signal level. By adjusting the ramp signal level through a controllable voltage source, the system achieves extended duty ratio control range beyond the limitations of input voltage adjustment alone, enabling full-range operation from 0% to 100% duty ratio.
2Adaptability or versatility
If the ramp signal level is adjusted to provide additional control parameter, then more flexible duty ratio control is achieved, but the adjustment range is limited by the upper limit of peak and lower limit of valley of the ramp signal
Solution Approach 1:
The patent implements dynamic adjustment of the ramp signal level by using a controllable voltage source that can be programmed to output any voltage within a wide range. This dynamic control mechanism allows the ramp signal level to be adjusted freely without being constrained by fixed peak or valley limits, enabling the duty ratio to be controlled across the entire 0%-100% range.
3Adaptability or versatility
If both the reference signal level and ramp signal level are adjustable, then full-range duty ratio control is achieved, but the circuit complexity increases
Solution Approach 1:
The patent employs a controllable voltage source that serves multiple functions: it generates the ramp signal, adjusts the ramp signal level, and can be programmed to provide different waveforms (triangle or sawtooth). This multi-functional component reduces the need for separate adjustment circuits for reference signal level and ramp signal level, thereby minimizing the increase in circuit complexity while achieving full-range duty ratio control.
Data Source
AI summary
The present invention discloses a PWM signal generation circuit and a PWM signal generation method. The PWM signal generation circuit includes: a reference signal generation circuit for generating a reference signal according to an input voltage; a variable ramp signal generation circuit for generating a variable ramp signal; and a comparator circuit for comparing the reference signal with the variable ramp signal to generate a PWM signal. A rising slope and/or a falling slope of the variable ramp signal is variable.