PWM Resonant Power Converter for Wide-Range ZVS Efficiency
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Solution Overview
Problem
Resonant power conversion circuits face inefficiencies at low output voltages and light loads due to the need for higher switching frequencies, failing to meet market demands for wide output voltage ranges and high conversion efficiency.
Innovation Solution
A power conversion circuit using pulse-width modulation control that turns on high-side and low-side transistors under valley and zero-voltage switching, optimizing efficiency by employing a control circuit that adjusts transistor operation based on resonant current and voltage thresholds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If higher switching frequency is used to maintain resonant operation at low output voltage or light load, then resonant operation can be maintained, but conversion efficiency deteriorates
Solution Approach 1:
The patent applies dynamics by making the switching frequency adjustable rather than fixed. The control circuit dynamically adapts the switching frequency based on operating conditions (load and output voltage), allowing the system to maintain resonant operation when beneficial while operating outside resonance when efficiency would otherwise deteriorate. This resolves the contradiction by making the system flexible rather than constrained to resonant operation at all conditions.
Solution Approach 2:
The patent changes the parameter of switching frequency based on operating conditions. By detecting load and output voltage levels, the control circuit adjusts the switching frequency to maintain resonance at optimal points while allowing frequency to drift from resonance when doing so improves efficiency. This parameter adaptation resolves the contradiction between maintaining resonant operation and preserving conversion efficiency.
2Reliability
If frequency control is used to maintain 50% duty cycle for high-side and low-side transistors, then zero-voltage switching is achieved, but adaptability to wide output voltage ranges deteriorates
Solution Approach 1:
The patent makes the control strategy dynamic by detecting output voltage levels and adapting the switching frequency accordingly. When output voltage is within an optimal range, the system maintains resonant operation with 50% duty cycles to ensure zero-voltage switching. When output voltage exceeds this range, the control circuit adjusts frequency and duty cycle to maintain conversion efficiency. This dynamic adaptation resolves the contradiction between ensuring zero-voltage switching and adapting to wide output voltage ranges.
Solution Approach 2:
The patent changes both switching frequency and duty cycle parameters based on output voltage detection. By comparing output voltage against reference values, the control circuit adjusts these parameters to maintain ZVS when conditions are favorable, while allowing deviation from ZVS when output voltage requires it for efficiency. This parameter adaptation resolves the contradiction between maintaining zero-voltage switching and achieving adaptability to wide output voltage ranges.
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
Improves conversion efficiency by ensuring zero-voltage and valley switching, enhancing performance across varying load conditions and output voltages.
Implementation Method 1
a resonant capacitor, a resonant inductor, a transformer... The primary coil, the resonant capacitor, and the resonant inductor are connected in series between a switch node and a ground
Implementation Method 2
The transformer comprises a primary coil and a secondary coil, where the primary coil is coupled between a switch node and a resonant node
Data Source
AI summary
A power conversion circuit converting an input voltage into an output voltage includes a transformer, a resonant capacitor, a high-side transistor, a low-side transistor, and a control circuit. The transformer includes a primary coil and a secondary coil. The resonant capacitor and the primary coil are coupled in series between a switch node and a ground, and a resonant current flows through the resonant capacitor. The high-side transistor is coupled between the input voltage and the switch node, and the low-side transistor is coupled between the switch node and the ground. The control circuit drives the high-side transistor and the low-side transistor based on the output voltage and the resonant current. When the resonant current reaches a first threshold, the control circuit turns off the low-side transistor so that the high-side transistor achieves zero-voltage switching.