Phase-Shifted PWM Circuits for Sub-Clock Pulse Resolution
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Solution Overview
Problem
Conventional pulse width modulation (PWM) systems have limited resolution, allowing pulse width changes only in increments of the clock period, which restricts the precision of pulse width modulation.
Innovation Solution
The proposed PWM system achieves higher resolution by logically combining multiple pulse width modulated signals that are phase shifted with respect to each other, using multiple clock sources and phase shifting techniques to generate pulse widths that can be adjusted in fractions of the clock period, thereby increasing the precision of pulse width modulation without increasing the clock frequency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the clock frequency is increased to improve pulse width resolution, then the resolution of pulse width changes is improved, but the complexity and power consumption of the system increases
Solution Approach 1:
The patent divides the pulse width modulation function into multiple independent PWM circuits, each operating at a lower clock frequency but generating phase-shifted output signals. By segmenting the overall PWM function across multiple circuits rather than using a single high-frequency circuit, the system achieves fine pulse width resolution without requiring a single high-frequency clock source, thus reducing individual circuit complexity and power consumption.
Solution Approach 2:
The patent combines multiple lower-frequency PWM circuit outputs through logical combination (OR operation) to achieve the equivalent resolution of a single high-frequency system. By merging the phase-shifted outputs of multiple circuits, the system synthesizes fine-grained pulse width control without the complexity and power consumption of a single high-frequency circuit.
2Measurement precision
If the clock frequency is increased to improve pulse width resolution, then the precision of pulse width modulation is improved, but the power consumption increases
Solution Approach 1:
The patent segments the high-power high-frequency PWM operation into multiple lower-power lower-frequency PWM circuit operations. Each circuit operates at reduced frequency and power consumption, but their combined phase-shifted outputs achieve the same effective resolution, thus reducing total power consumption while maintaining precision.
Solution Approach 2:
The patent creates multiple copies of the PWM circuit, each operating at lower frequency, and combines their outputs. Rather than using one high-frequency circuit, multiple low-frequency copies are synthesized and combined, achieving the same functional result with lower power consumption per circuit.
3Device complexity
If a single PWM circuit is used to simplify the system, then the device complexity is reduced, but the pulse width resolution is limited to clock period increments
Solution Approach 1:
The patent segments the PWM function into multiple circuits that each operate independently at lower frequency. By dividing the single-circuit function into multiple segment circuits with phase-shifted outputs, the system achieves fine resolution without requiring a single complex high-frequency circuit.
Solution Approach 2:
The patent adds the dimension of phase shifting to the PWM approach. Instead of relying solely on frequency increases for resolution, the system introduces phase as an additional dimension of control, where multiple circuits operating at the same frequency but different phases combine to provide fine-grained pulse width resolution.
Data Source
AI summary
A pulse width modulation (PWM) system can include at least a first pulse width modulation circuit that generates a first pulse width modulated signal in synchronism with a first clock signal; a source circuit that provides a second pulse width modulated signal that is phase shifted with respect to the first pulse width modulated signal; and output logic that logically combines the first and second pulse width modulated signals to generate a pulse width modulated output signal.