Resonant Half-Bridge Converter Control for Power Factor Correction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current-controlled resonant converters lack concrete guidance for achieving optimum power factor correction, particularly in controlling the switching bridge's conductive and non-conductive times to match input voltage and current phases.
Innovation Solution
A resonant half-bridge converter with a control circuit that senses input voltage and resonant current, controlling the high-side switch's conduction period to be twice the rise time of a reference current proportional to the input voltage, using a comparator and counter to determine the switch-off time based on a delay measured from a voltage crossing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If current-controlled resonant converters are used for power factor correction, then power factor correction capability is provided, but lack of concrete control guidance results in suboptimum power factor correction
Solution Approach 1:
The patent implements feedback control by sensing the resonant current and using it to determine the switching bridge conduction period. The control circuit measures the resonant current waveform and adjusts the switch timing based on the measured current characteristics, creating a closed-loop system that automatically optimizes power factor correction without requiring complex external control guidance.
Solution Approach 2:
The resonant converter system uses its own resonant current waveform as the control reference, eliminating the need for external control signals or complex timing guidance. The control circuit derives all necessary timing information from the resonant current itself, making the system self-regulating and easy to implement.
2Reliability
If the switching bridge conduction period is extended to improve power factor correction, then phase matching between input voltage and current is improved, but switching losses increase
Solution Approach 1:
The patent implements dynamic adjustment of the switching bridge conduction period based on real-time resonant current characteristics. Rather than using a fixed conduction period, the control circuit continuously adapts the switching timing to match the instantaneous resonant current waveform, optimizing the balance between phase matching accuracy and switching loss minimization.
Solution Approach 2:
The control circuit changes the conduction period parameter dynamically by measuring the resonant current waveform and adjusting the switch timing accordingly. This parameter adaptation allows the system to achieve optimal phase matching while minimizing switching losses by precisely timing the conduction period to the actual resonant current characteristics.
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
Achieves optimum power factor correction by ensuring the switch-on period aligns with the phase-lagging resonant current, enhancing efficiency and power factor correction in inductive mode.
Implementation Method 1
a switching bridge circuit generates a square-wave voltage that excites a resonant tank circuit to output a resonant sinusoidal current
Data Source
Figure 1
Figure 2
Figure 3a~3c
AI summary
Disclosed is a resonant half-bridge converter (1) for a light-emitting diode, LED, light source (2). The converter (1) comprises a switching circuit (101, 102), comprising a high-side switch (101) and a low-side switch (102) connected in series, and being subjected to a rectified input voltage (Vin) of the converter (1) with reference to a ground electric potential of the converter (1). The converter (1) further comprises a resonant tank circuit (103, 104, 105), connected between a common electric potential of the high-side switch (101) and the low-side switch (102) and the ground electric potential of the converter (1), and comprising a plurality of reactive circuit elements (104, Ls, 103, Cs, 105, Cp). The converter (1) further comprises a voltage sensing circuit (106), being arranged to sense a first voltage being indicative of an instantaneous value of the rectified input voltage (Vin). The converter (1) further comprises a current sensing circuit (107), being arranged to sense a second voltage being indicative of a resonant current (Ires) of the resonant tank circuit (103, 104, 105). The converter (1) further comprises a control circuit (108), being arranged to improve a power factor of the converter (1) by controlling a duration of a conduction period of the high-side switch (101) to be twice a duration (td) of a rise of the second voltage to a third voltage being indicative of a reference current (Ires,ref), wherein the third voltage is proportional to the first voltage.. This facilitates achievement of optimum power factor correction based on current-controlled resonant converters.