Totem-Pole PFC Bridge-Midpoint Sensing for Transistor Protection
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Solution Overview
Problem
The totem-pole power factor correction circuit has a complex structure, leading to increased costs and occupied space due to the need for complex detection circuits like current transformers and auxiliary windings.
Innovation Solution
A simplified detection circuit that directly detects currents and voltages between the power transistor and the bridge arm middle point using comparators, phase inverters, OR logic circuits, and flip-flops, eliminating the need for complex structures like current transformers and auxiliary windings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If complex detection circuits like current transformers and auxiliary windings are used to detect current, then the power transistor can be protected when current is excessively large, but the structural complexity and cost increase
Solution Approach 1:
The patent extracts the current detection function from complex external components (current transformers, auxiliary windings) and implements it directly within the existing half-bridge circuit by utilizing the body diode of the power transistor and a simple sampling resistor. This extraction eliminates unnecessary components while maintaining the protection function.
Solution Approach 2:
The power transistor's body diode is utilized to provide the detection path, making the transistor itself participate in the detection process. The circuit uses its own inherent components (body diode, source-drain junction) to detect current conditions, eliminating the need for separate complex detection devices.
2Measurement precision
If complex detection circuits like current transformers and auxiliary windings are used, then current detection capability is achieved, but the occupied space increases
Solution Approach 1:
The detection function is merged with the existing power transistor and half-bridge circuit structure. The sampling resistor is integrated into the source terminal connection, and the detection path shares components with the normal current path, thereby eliminating the need for separate detection components that would occupy additional space.
Solution Approach 2:
The body diode of the power transistor serves dual purposes: it provides the normal freewheeling current path during switching operation and simultaneously serves as the detection path for current monitoring. This multi-functionality eliminates the need for dedicated detection components.
Data Source
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AI summary
This application provides a totem-pole power factor correction circuit and a power supply module. A detection circuit of the totem-pole power factor correction circuit can detect a current between a power transistor and a bridge arm middle point, and determine a current value when an inductor is charged. When a control circuit controls a drive circuit to drive the power transistor to be turned on, in response to a value of a current flowing through the inductor being greater than a first predetermined value, the drive circuit can drive, in time based on a detection result of the detection circuit, the power transistor to be turned off, to protect the power transistor. Based on the totem-pole power factor correction circuit and the power supply module in which the totem-pole power factor correction circuit is located that are provided in embodiments of this application, structure complexity is reduced, and the costs are reduced, thereby further reducing space occupied by a device.