Switching Control Circuit With Dynamic Rectification for PFC Loss Reduction
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Solution Overview
Problem
Switching loss and conduction loss of transistors and diodes become significant issues in power factor correction circuits operating in critical mode, particularly for low-power devices.
Innovation Solution
A switching control circuit that includes a first driver circuit to control transistors based on inductor current and output voltage, and a second driver circuit to implement synchronous rectification modes, reducing switching loss by complementary switching and zero voltage switching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the PFC circuit is operated in the critical mode, then the power factor is improved by shaping the inductor current waveform, but switching loss of the transistor and conduction loss of the diode increase
Solution Approach 1:
The patent implements dynamic mode switching between critical mode and continuous mode based on operating conditions. The control circuit monitors the inductor current and automatically transitions between modes to minimize losses while maintaining power factor correction performance. This dynamic adaptation allows the system to operate in critical mode when efficient and in continuous mode when loss reduction is prioritized.
Solution Approach 2:
The patent changes the operating parameters of the PFC circuit by adjusting the switching frequency and duty cycle dynamically. By modifying these parameters based on the operating mode, the circuit optimizes the balance between power factor correction effectiveness and loss minimization. The control circuit adjusts parameters to reduce switching losses in continuous mode while maintaining effective waveform shaping in critical mode.
2Power
If the ON period of the first transistor is extended, then the output voltage is maintained at target level, but switching loss increases due to frequent switching
Solution Approach 1:
The patent employs periodic switching action with optimized duty cycles to maintain output voltage while reducing switching frequency. By carefully controlling the ON period and switching timing, the circuit achieves stable output voltage regulation with minimized switching losses. The periodic nature of the switching allows for predictable loss characteristics and efficient heat management.
Solution Approach 2:
The control circuit performs preliminary adjustment of the switching parameters before the main switching operation. By pre-setting the optimal ON period and switching timing based on anticipated load conditions, the circuit minimizes unnecessary switching actions while ensuring output voltage stability is maintained throughout the operating cycle.
Data Source
AI summary
A switching control circuit for a power supply circuit, including: a first driver circuit configured to turn on a first transistor of the power supply circuit after an inductor current therein reaches a first value, and turn off the first transistor in response to an ON period corresponding to an output voltage of the power supply circuit having elapsed; a second driver circuit configured to, when the ON period of the first transistor is shorter than a first time period, drive the first transistor in a first mode, which is a mode in which the first transistor is switched in a state where a second transistor of the power supply circuit is kept off, and when the ON period exceeds the first time period, drive the second transistor in a second mode, which is a mode in which the second transistor is switched complementarily to the first transistor.