PWM Modulator Triangular Waveform Peaks to Prevent Pulse Skipping
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Solution Overview
Problem
PWM modulators in class D amplifiers experience pulse skipping due to high frequency disturbances or oscillations when operating near saturation conditions, leading to system malfunction with modulating signals of large dynamics or under strong disturbances.
Innovation Solution
Introducing a synchronous peak on the vertex of the triangular waveform, either through an auxiliary clock and high pass filter or by adding a resistor in series with the capacitor in the feedback loop of the op-amp integrator, to prevent pulse skipping and reduce spurious switching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an auxiliary clock and high pass filter are introduced to create synchronous peaks on the triangular waveform, then pulse skipping is prevented and system reliability is improved, but device complexity and power consumption increase
Solution Approach 1:
The patent extracts only the essential function of creating synchronous peaks by removing the auxiliary clock and high pass filter, and achieves the same effect through a simplified resistor-capacitor network in the feedback loop that directly generates the required current peaks
Solution Approach 2:
The patent merges the peak generation function into the existing feedback loop of the op-amp integrator by adding a resistor in series with the capacitor, combining multiple functions (integration, feedback, and peak generation) into a single unified circuit structure
2Reliability
If an auxiliary clock and high pass filter are introduced to create synchronous peaks, then pulse skipping is prevented, but power consumption increases
Solution Approach 1:
The patent removes the power-consuming auxiliary clock generator and high pass filter components, extracting only the essential peak-generation function and implementing it through passive resistor-capacitor elements that consume minimal power
Solution Approach 2:
The feedback loop components (resistor and capacitor) generate the synchronous peaks using the existing carrier signal and operational amplifier, making the circuit self-sufficient without requiring additional active power-consuming components
3Measurement precision
If the triangular waveform has sharp vertices, then the PWM modulation is precise, but spurious switching occurs under strong disturbances
Solution Approach 1:
The patent applies beforehand cushioning by introducing a resistor in series with the integrator capacitor, which rounds the triangular waveform vertices in advance before comparison occurs, preventing spurious switching that would result from sharp vertices under disturbance conditions
Solution Approach 2:
The patent changes the waveform parameter by modifying the vertex shape from sharp to rounded through the addition of resistance in the feedback loop, altering the slope characteristics to prevent excessive switching while maintaining adequate modulation precision
Data Source
AI summary
A method is for reducing pulse skipping from a characteristic affecting a modulating signal input to an integrator of a pulse width modulation (PWM) modulator, together with a square wave carrier signal for generating a triangular waveform of the PWM modulator. The method may include creating a broad synchronous peak at vertexes of the triangular waveform output by the integrator.