PWM Circuit Topology for Linear Duty Cycle Adjustment
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Solution Overview
Problem
Existing pulse width modulation (PWM) circuits face limitations in linearly adjusting duty cycle over a wider range, leading to non-linear relationships between input DC voltage and PWM signal, which can result in unwanted effects such as non-linear motor speed control.
Innovation Solution
A PWM circuit comprising an input voltage source, regulator, multiple voltage-dividing units, a voltage adder, and a comparator, where the duty cycle is linearly adjusted by generating and comparing divided voltages to produce a pulse width modulation signal with a linear relationship to the input voltage, allowing flexible control of duty cycle without additional components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the high and low voltage levels of the triangular wave signal are controlled via the input DC voltage to adjust duty cycle across a wider range, then the duty cycle tuning range is improved, but the linearity between duty cycle and input voltage deteriorates
Solution Approach 1:
The patent segments the voltage control function into multiple independent voltage-dividing units. Each unit divides a portion of the input voltage to generate specific voltage levels for the triangular wave signal. This segmentation allows the high and low voltage levels to be independently adjusted through separate dividing ratios, enabling wide duty cycle tuning while maintaining linear relationship with input voltage.
Solution Approach 2:
The patent applies local quality by assigning different functions to different parts of the voltage control system. The first voltage-dividing unit specifically controls the high voltage level, the second voltage-dividing unit controls the low voltage level, and the third voltage-dividing unit provides reference voltage. Each unit has optimized dividing ratios to ensure that the overall system maintains linearity while achieving wide duty cycle adjustment range.
2Adaptability or versatility
If the reference voltage generator is modified to achieve wider duty cycle tuning, then the duty cycle range is improved, but the device complexity increases
Solution Approach 1:
The patent makes the voltage-dividing units universal by designing them to handle multiple functions. The same voltage-dividing unit structure is used for generating both high and low voltage levels of the triangular wave, as well as for providing reference voltage. This multi-functionality reduces the need for separate dedicated components for each function, thereby reducing overall device complexity while achieving wide duty cycle tuning.
Solution Approach 2:
The patent introduces dynamic adjustability through controllable voltage-dividing units whose dividing ratios can be dynamically changed. This allows the system to adapt to different duty cycle requirements without requiring additional fixed components. The dynamic nature of the voltage division enables a single set of units to cover a wide tuning range, reducing the need for multiple static component sets.
Data Source
AI summary
A pulse width modulation circuit capable of linearly adjusting duty cycle with voltage, which comprises an input voltage source for generating an input voltage, a regulator for generating a regulated voltage, a first voltage-dividing unit for providing a first divided voltage, a second voltage-dividing unit for providing a second divided voltage, a third voltage-dividing unit for providing a third divided voltage, a voltage adder for adding the first divided voltage and the third divided voltage for generating a high level voltage, a waveform generator for generating an oscillating signal according to the high level voltage and the third divided voltage, and a comparator having a first input terminal coupled to the second voltage-dividing unit, a second terminal coupled to the waveform generator, and an output terminal for comparing the second divided voltage with the oscillating signal to output a pulse width modulation signal through the output terminal.