Sub-harmonic Detector for PWM Signal Stability
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Solution Overview
Problem
Conventional voltage converting apparatuses face challenges in detecting sub-harmonic conditions in PWM signals, leading to unstable pulse widths and excessive current flow, which affects the efficiency and stability of the power transistor operation.
Innovation Solution
A sub-harmonic detector is introduced, comprising a pulse eliminating circuit, a counter, and a comparator, which processes the PWM signal by subtracting reference pulses to generate a processed signal and count pulses within a time period, allowing for the detection of sub-harmonic conditions through comparison of counting values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional voltage converting apparatus uses simple PWM signal generation without sub-harmonic detection, then device complexity is reduced, but pulse width stability deteriorates and excessive current flow occurs
Solution Approach 1:
The detection function is divided into separate modular components: pulse eliminating circuit, counter, and comparator. Each module performs a specific function in the sub-harmonic detection process, making the overall system more manageable and maintainable while achieving reliable pulse width stability
Solution Approach 2:
A reference PWM signal is introduced as an intermediary element to compare against the actual PWM signal. This reference signal serves as a benchmark for detecting sub-harmonic conditions, enabling stable pulse width control without requiring complex direct measurement circuits
2Reliability
If sub-harmonic detection is implemented using pulse eliminating circuit, counter, and comparator, then pulse width stability is improved, but device complexity increases
Solution Approach 1:
The harmful sub-harmonic conditions are extracted and identified through the detection circuit before they can cause excessive current flow. By taking out the detection function as a separate subsystem, the main power conversion circuit remains simple while achieving improved current control
Solution Approach 2:
The sub-harmonic detection is performed in advance before excessive current flow occurs. The pulse eliminating circuit and counter continuously monitor PWM signal characteristics, and the comparator triggers corrective action preemptively, preventing harmful current conditions rather than responding to them after occurrence
Data Source
AI summary
A voltage converting apparatus and a sub-harmonic detector are disclosed. The sub-harmonic detector includes a pulse eliminating circuit, a counter, and a comparator. The pulse eliminating circuit receives a pulse width modulation (PWM) signal and a reference PWM signal having a same period. The PWM signal and reference PWM signal has a plurality of pulses and reference pulses respectively. The pulse eliminating circuit eliminates at least one part of the pulses which overlap with the reference pulses for generating a processed signal. The counter counts the processed signal and the PWM signal during a time period to obtain first and second counting values. The comparator compares the first and second counting values for detecting whether a sub-harmonic condition happens or not in the PWM signal.