Bridgeless PFC Power Module Reverse Overcurrent Protection
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Solution Overview
Problem
Bridgeless PFC circuits in power modules are susceptible to damage from sudden voltage changes or lightning strikes, causing large reverse overcurrents that affect the reliability of switching transistors.
Innovation Solution
A power module design with a low-frequency and high-frequency bridgeless PFC circuit, where a controller detects potential differences across diodes to quickly turn off low-frequency switching transistors when preset conditions are met, avoiding damage and implementing reverse overcurrent protection without the need for large current sampling elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a bridgeless PFC circuit is used to improve efficiency and power density, then the power module achieves higher efficiency and power density, but the switching transistor becomes vulnerable to damage from reverse overcurrent
Solution Approach 1:
The controller continuously monitors the voltage difference across the diode before reverse overcurrent occurs. When the voltage difference exceeds the threshold, the controller proactively turns off the switching transistor in advance, preventing the transistor from being damaged by the upcoming reverse overcurrent. This preliminary detection and preventive action resolve the contradiction by maintaining both high efficiency (through bridgeless PFC operation) and transistor reliability (through protective shutdown).
2Reliability
If a current sampling element is used to detect reverse overcurrent, then the switching transistor can be protected, but the power module occupies more space and incurs higher costs
Solution Approach 1:
The diode in the bridgeless PFC circuit inherently provides the voltage sampling function needed for overcurrent protection. The controller utilizes the voltage difference across this existing diode element to detect reverse overcurrent conditions, eliminating the need for separate current sampling elements. This self-service approach resolves the contradiction by achieving transistor protection (reliability) while avoiding additional space occupation and cost increases.
3Reliability
If a current sampling element is used to detect reverse overcurrent, then the switching transistor can be protected, but the power module incurs higher costs
Solution Approach 1:
The existing diode in the bridgeless PFC circuit serves dual purposes: its primary function in the power conversion process and its secondary function as a voltage sampling element for overcurrent protection. By utilizing the voltage difference across this existing component, the system eliminates the need to purchase and install separate current sampling elements, thereby reducing manufacturing costs while maintaining transistor protection capability.
Solution Approach 2:
The diode is designed to perform multiple functions: it participates in the power factor correction operation and simultaneously serves as the sensing element for reverse overcurrent detection. This multi-functionality resolves the contradiction by achieving protection (reliability) without adding extra components, thus maintaining cost-effectiveness and ease of manufacture.
Data Source
AI summary
A power module includes a bridgeless PFC circuit and a controller. The bridgeless PFC circuit includes a low-frequency module and a high-frequency module that are connected. The low-frequency module includes two low-frequency bridge arms that are connected in parallel. One low-frequency bridge arm includes two low-frequency switching transistors that are connected in series. The other low-frequency bridge arm includes two diodes that are connected in series. The controller is configured to turn off the low-frequency switching transistor in the one low-frequency bridge arm when an anode potential and a cathode potential of the diode in the other low-frequency bridge arm meet at least one of the following conditions: A difference obtained by subtracting the cathode potential from the anode potential is greater than a preset voltage value, and a difference obtained by subtracting the anode potential from the cathode potential is less than an opposite number of the preset voltage value.