Shared-Switch Charge-Pump AC-DC Converter for Low-EMI PFC
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional LED drivers face challenges in achieving high power factor, efficiency, and compact size due to the limitations of two-stage converters with pulse-width-modulated (PWM) converters, which result in high conducted electromagnetic interference (EMI) and larger passive components.
Innovation Solution
The proposed AC-DC power converter incorporates a charge-pump-based power factor correction sub-converter and a resonant sub-converter with a shared controllable switch network, allowing for independent operation of power factor correction and DC-DC conversion using soft-switching techniques, thereby reducing switching losses and component size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If pulse-width-modulated (PWM) converters are used in conventional two-stage LED drivers, then power factor correction can be achieved, but conducted electromagnetic interference (EMI) increases and passive component sizes increase
Solution Approach 1:
The converter is divided into two independent single-phase stages: a charge-pump PFC stage and a resonant DC-DC stage. Each stage operates independently with its own current path, allowing the PFC function to be achieved without the high-frequency switching EMI characteristics of conventional PWM converters. The segmentation enables each stage to be optimized for its specific function.
Solution Approach 2:
The harmful high-frequency switching EMI is extracted and eliminated by replacing the PWM switching mechanism with soft-switching techniques in the resonant stage. The PFC function is extracted into a separate charge-pump stage that operates at lower frequencies, removing the source of conducted EMI while maintaining power factor correction capability.
2Ease of manufacture
If pulse-width-modulated (PWM) converters are used in conventional two-stage LED drivers, then power factor correction can be achieved, but passive component sizes increase
Solution Approach 1:
The switching frequency parameter is changed from low-frequency PWM operation to high-frequency soft-switching operation. This parameter change enables the use of smaller passive components (inductors and capacitors) while maintaining or improving efficiency. The resonant stage operates at frequencies where smaller components can achieve the same energy storage and filtering functions.
Solution Approach 2:
The mechanical switching mechanism of PWM converters is replaced with a resonant soft-switching mechanism. This substitution eliminates the need for large PWM filters and allows the use of smaller resonant tank components, reducing overall passive component size while maintaining power factor correction through the charge-pump stage.
3Loss of energy
If resonant inverters operate at high switching frequencies, then switching losses are reduced, but component size must be minimized
Solution Approach 1:
The resonant inverter employs dynamic soft-switching operation where the switching instances are synchronized with the resonant tank voltage and current waveforms. This dynamic operation enables zero-voltage switching (ZVS) and/or zero-current switching (ZCS), minimizing switching losses at high frequencies. The controllable switch network adapts its switching timing to maintain optimal operating conditions throughout the power range.
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
This solution achieves high efficiency and compact size by utilizing soft-switching in the resonant sub-converter, reducing switching losses, and allowing for independent operation of power factor correction and DC-DC conversion, while maintaining high power factor and efficiency.
Implementation Method 1
a resonant tank configured to convert the DC-bus supply voltage to a resonant voltage or current
Implementation Method 2
an output rectification circuit configured to generate the DC output voltage or DC output current from the resonant voltage or current
Data Source
AI summary
An AC-DC power converter includes: an AC rectification circuit configured to convert an AC line voltage into a rectified line voltage; a charge-pump-based power factor correction sub-converter configured to provide a DC-bus supply voltage; a resonant sub-converter configured to convert the DC-bus supply voltage to a DC output voltage or DC output current, the resonant sub-converter including: a resonant tank configured to convert the DC-bus supply voltage to a resonant voltage or current; and an output rectification circuit configured to generate the DC output voltage or DC output current from the resonant voltage or current to supply a converter load, and a controllable switch network shared by the charge-pump-based power factor correction sub-converter and the resonant sub-converter.