AHB Flyback Converter Control With Differential Auxiliary Sensing
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Solution Overview
Problem
Existing half-bridge flyback power converters face challenges in maintaining a high signal-to-noise ratio (SNR) across wide output voltage ranges, particularly when the output voltage is low, due to the need for a relatively low voltage ratio for auxiliary voltage sensing.
Innovation Solution
A resonant asymmetrical half-bridge (AHB) flyback power converter with differential voltage sensing is introduced, featuring a switching control circuit that includes a voltage divider, differential input sensing circuit, feedback circuit, and PWM control circuit. This configuration enhances SNR by accurately sensing auxiliary signals and generating feedback and PWM signals to control the transistors effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a low voltage ratio is used for auxiliary voltage sensing to accommodate high output voltage (e.g., 48V), then the device can handle wide output voltage ranges, but the signal-to-noise ratio (SNR) deteriorates when output voltage is low (e.g., 5V)
Solution Approach 1:
The sensing process is segmented into two distinct paths: a first voltage ratio for sensing when output voltage is high, and a second voltage ratio for sensing when output voltage is low. This segmentation allows each sensing path to be optimized for its specific voltage range, preventing the SNR deterioration that occurs with a single fixed voltage ratio
Solution Approach 2:
The voltage ratio is made dynamic rather than fixed. The system automatically switches between different voltage ratios based on the output voltage level, enabling the sensing circuit to adapt its characteristics to maintain optimal SNR across the entire output voltage range from 5V to 48V
2Measurement precision
If differential voltage sensing is implemented to improve SNR at low output voltages, then measurement precision improves, but device complexity increases
Solution Approach 1:
The differential input sensing circuit serves multiple functions: it performs voltage sensing, generates peak detection signals, produces demagnetization-time signals, and provides over-voltage and under-voltage protection. By making the sensing circuit multi-functional, the patent reduces the need for separate circuits for each function, thereby limiting the increase in device complexity
Solution Approach 2:
Multiple sensing functions are merged into a single differential input sensing circuit. The circuit simultaneously handles auxiliary voltage sensing, peak detection, and protection functions, consolidating what could have been separate circuits into one integrated unit
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The proposed solution significantly improves the signal-to-noise ratio (SNR) across a wide range of output voltages, ensuring efficient power conversion and maintaining high precision control, even at low output voltages.
Implementation Method 1
a resonant capacitor, a first transistor and a second transistor, which are coupled to convert an input power to an outpout power; wherein the peak signal is related to a quasi-resonance of the transformer after the transformer is demagnetized
Data Source
AI summary
A resonant asymmetrical half-bridge flyback power converter includes: a first transistor and a second transistor switching a transformer coupled to a capacitor for generating an output power; a voltage divider coupled to an auxiliary winding of the transformer; a differential sensing circuit which includes a first terminal and a second terminal coupled to the voltage divider to sense an auxiliary signal generated by the auxiliary winding for generating a peak signal and a demagnetization-time signal; and a PWM control circuit configured to generate a first PWM signal and a second PWM signal in accordance with the peak signal and the demagnetization-time signal, for controlling the first transistor and the second transistor respectively; wherein a period of an enabling state of the demagnetization-time signal is correlated to the output power level; wherein the peak signal is related to a quasi-resonance of the transformer after the transformer is demagnetized.