Active Clamp Power Factor Correction Circuit for GaN Switching Loss Reduction
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Solution Overview
Problem
The working frequency of hard switching totem pole power factor correction circuits is limited due to parasitic body capacitance discharging loss, which increases turn-on loss for gallium nitride power devices, restricting the power density and efficiency of switching power supplies.
Innovation Solution
A power factor correction circuit design incorporating a first and second bridge arm, an output capacitor, and an active clamp unit, where the active clamp unit includes a second inductor, a clamp capacitor, and a fifth switch, positioned between various components to reduce switching loss and enable higher working frequencies through zero-voltage switching (ZVS) functions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the working frequency of hard switching totem pole power factor correction circuit is increased to increase power density, then the power density increases, but the parasitic body capacitance discharging loss increases dramatically causing turn-on loss to reach ten times higher than turn-off loss
Solution Approach 1:
The active clamp unit performs preliminary action by discharging the parasitic body capacitance of the gallium nitride power device before the main switching operation. The clamp switch and clamp capacitor are activated in advance to transfer and discharge the parasitic capacitance energy, ensuring that when the main switch turns on, the capacitance is already discharged, thereby dramatically reducing turn-on loss and enabling high-frequency operation.
2Speed
If wide bandgap devices are used to increase switching frequency and power density, then switching speed increases and switching loss decreases, but parasitic body capacitance discharging loss during switching operation increases dramatically
Solution Approach 1:
The active clamp unit acts as an intermediary between the gallium nitride power device and the main circuit. It includes a clamp switch, clamp capacitor, and clamp inductor that work together to transfer and discharge the parasitic body capacitance energy separately from the main power switching operation. This intermediary mechanism allows the main switch to operate at high frequency with high switching speed while the parasitic capacitance is handled independently, preventing the dramatic increase in turn-on loss.
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 design achieves reduced switching loss and increased working frequency, allowing for higher power density and efficiency in switching power supplies while maintaining good efficiency, by utilizing the active clamp unit to manage parasitic capacitance and switching operations.
Implementation Method 1
enable higher working frequencies through zero-voltage switching (ZVS) functions
Data Source
AI summary
A power factor correction circuit includes an input power source, a first bridge arm, a second bridge arm, an output capacitor and an active clamp unit. The first bridge arm includes a first switch and a second switch in series. The second bridge arm includes a third switch and a fourth switch in series. The active clamp unit includes a second inductor, a clamp capacitor and a fifth switch. The power factor correction circuit may realize the ZVS function of the first switch and the second switch by the collaboration of the active clamp unit and the conduction/non-conducting state of the first switch, the second switch, the third switch and the fourth switch.