Bridgeless PFC Converter Topology and Light-Load Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional PFC power converters have high power consumption and reduced efficiency due to the number of semiconductor devices in the conduction path, and they do not effectively manage power during light-load conditions.
Innovation Solution
A bridgeless PFC power converter design that reduces the number of semiconductor devices in the conduction path and includes a control circuit to generate switching signals for high efficiency, as well as a light-load signal to disconnect the EMI filter during low power usage, thereby saving power.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional PFC power converter uses bridge rectifier with multiple semiconductor devices, then PFC function is achieved, but power consumption increases and circuit efficiency decreases
Solution Approach 1:
The patent removes the bridge rectifier from the conventional PFC circuit topology, extracting only the necessary PFC function through two transistors and two inductors. This extraction eliminates four diodes and reduces semiconductor devices in the current conduction path from three to two, directly reducing power loss while maintaining PFC capability.
Solution Approach 2:
The patent segments the conventional bridge rectifier PFC circuit into separate functional modules: two independent inductors (first and second inductors) with their own transistors, allowing each to operate in alternating half-cycles. This segmentation enables the removal of the bridge rectifier while maintaining the overall PFC function through coordinated operation of the segmented components.
2Loss of energy
If EMI filter is connected during light-load condition, then EMI filtering is provided, but power consumption increases
Solution Approach 1:
The patent implements dynamic control of the EMI filter by using a control circuit to generate a light-load signal that switches the third and fourth transistors based on load conditions. During light-load operation, the EMI filter is disconnected to save power, while during heavy-load operation, the filter is connected to provide EMI filtering. This dynamic adjustment resolves the contradiction between power consumption and EMI protection.
Solution Approach 2:
The control circuit periodically monitors the load condition and switches the EMI filter connection state accordingly. The light-load signal is generated based on periodic detection of the output voltage or current, enabling the EMI filter to be connected when needed and disconnected when not needed, thus reducing power consumption during light-load conditions while maintaining EMI performance when required.
Data Source
AI summary
A bridgeless PFC power converter comprises a first inductor and a second inductor coupled from a first input-terminal and a second input-terminal to a first transistor and a second transistor. A first diode and a second diode are coupled from the first transistor and the second transistor to an output capacitor. A first capacitor and a second capacitor are coupled from the input-terminals to the ground terminal through a third transistor and a fourth transistor. A control circuit generates a first-switching signal and a second-switching signal to control the first transistor and the second transistor. The second-switching signal will turn on the second transistor when the first-switching signal switches the first transistor. The first-switching signal will turn on the first transistor when the second-switching signal switches the second transistor. The control circuit turns off the third transistor and the fourth transistor during the light-load of the PFC power converter.