Totem Pole PFC Bootstrap Precharge for Startup Loss Reduction
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Solution Overview
Problem
In totem pole power factor correction (PFC) circuits, the bootstrap capacitor often fails to charge during startup or restart due to residual voltages or reverse cut-off states of parasitic diodes, leading to persistent operation of the lower transistor in standby mode, resulting in increased energy loss and reduced component lifespan.
Innovation Solution
A system and method that includes a sampling control circuit to precharge the power supply drive circuit in a PFC circuit by controlling the lower bridge arm based on alternating current power supply voltages, reducing electric energy loss and prolonging circuit element lifespan.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the lower transistor is kept in standby state to persistently work, then the bootstrap capacitor voltage is maintained in proper working range, but additional energy loss increases and component service life is reduced
Solution Approach 1:
The patent applies preliminary action by detecting the voltage of the bootstrap capacitor before the PFC circuit operates, and pre-charging it when the voltage is below the threshold. This ensures the capacitor is ready for normal operation without needing continuous standby operation of the lower transistor, thereby reducing energy loss while maintaining reliability.
2Reliability
If the lower transistor is kept in standby state to persistently work, then the bootstrap capacitor voltage is maintained in proper working range, but component service life is reduced
Solution Approach 1:
The patent performs preliminary detection and pre-charging of the bootstrap capacitor before normal operation. This eliminates the need for continuous standby operation of the lower transistor, reducing wear and tear on components while ensuring the capacitor is properly charged, thus extending component service life while maintaining voltage stability.
3Loss of energy
If precharging is performed based on voltage detection, then energy loss is reduced, but control circuit complexity increases
Solution Approach 1:
The patent implements feedback by detecting the bootstrap capacitor voltage and using this information to control the pre-charging process. The detection circuit monitors the voltage and provides feedback to the control logic, which then decides whether to activate the pre-charging path. This feedback mechanism enables energy-efficient operation while keeping the control circuit relatively simple through straightforward voltage comparison and control logic.
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 solution effectively precharges the power supply drive circuit, reducing energy loss and extending the service life of circuit elements by optimizing the charging process and ensuring efficient operation of the totem pole PFC circuit.
Implementation Method 1
a sampling control circuit to precharge the power supply drive circuit in a PFC circuit when a sampling control circuit determines that values of voltages of two ends of an alternating current power supply meet a precharging condition
Implementation Method 2
a lower bridge arm to be turned on, so that the power supply drive circuit starts charging
Data Source
AI summary
The control system includes a PFC circuit and a sampling control circuit, and the PFC circuit includes an inductor, a first power supply drive circuit, and a first bridge arm and a second bridge arm that are connected in parallel, and a first bridge arm midpoint is a serial connection point between a first upper bridge arm and a first lower bridge arm of the first bridge arm. The sampling control circuit is configured to control, based on voltages of two ends of an alternating current power supply, the first lower bridge arm to be turned on, so that the first power supply drive circuit starts charging. The sampling control circuit is further configured to: when charging duration of the first power supply drive circuit reaches first target duration, control the first lower bridge arm to be turned off, so that the first power supply drive circuit completes charging.