Half-Bridge Precharge Control for Switching Noise Suppression
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Solution Overview
Problem
Existing power conversion devices emit electromagnetic noise due to steep potential fluctuations caused by parasitic capacitance discharge during switching element transitions, which can exceed tolerance levels.
Innovation Solution
Implementing precharge circuits to precharge switching elements before turning them on during dead times, thereby reducing the amount of electric charge flowing into parasitic capacitances and minimizing potential fluctuations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If switching elements are turned on during dead times without precharging, then the power conversion device operates efficiently, but steep potential fluctuations occur due to parasitic capacitance discharge causing electromagnetic noise
Solution Approach 1:
The precharge circuit performs preliminary charging of the parasitic capacitance before the switching element is turned on. During the dead time, the precharge circuit charges the parasitic capacitance to a predetermined voltage, so when the switching element turns on, there is no sudden discharge current, thereby preventing electromagnetic noise while maintaining efficient power conversion operation
2Object-generated harmful factors
If precharge circuits are added to precharge switching elements, then electromagnetic noise is reduced, but device complexity increases
Solution Approach 1:
A precharge circuit is introduced as an intermediary component between the power supply and the switching element. This precharge circuit includes a precharge transistor and precharge resistor that temporarily charge the parasitic capacitance during dead time, acting as a mediator to prevent noise without requiring major structural changes to the main power conversion circuit
3Object-generated harmful factors
If the precharge transistor is kept on continuously, then parasitic capacitance is continuously charged, but power consumption increases
Solution Approach 1:
The precharge transistor operates periodically rather than continuously. It is turned on during dead time when the main switching element is off and turned off when the main switching element is on, creating a periodic charging action that prevents potential fluctuation only when needed, thereby minimizing power consumption while maintaining noise suppression effectiveness
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
Suppresses spike noise and electromagnetic noise emissions by stabilizing parasitic capacitance voltages, ensuring compliance with noise tolerance limits.
Implementation Method 1
parasitic capacitance discharge during switching element transitions
Data Source
AI summary
According to one embodiment, a control method is provided. The control method includes: precharging, in a state where both of a first switching element and a second switching element in a power conversion device are turned off when the first and second switching elements perform a synchronous rectification operation, one end of the first switching element, the first and second switching elements being half-bridge connected between an input node and an output node, and the power conversion device converting an AC voltage into a DC voltage; and turning on the second switching element after the precharging the one end of the first switching element is completed.