Bridgeless PFC Switch Control Using Current Threshold Turn-On
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Solution Overview
Problem
The voltage of the switch element in bridgeless boost PFC circuits changes violently, requiring high sampling control and weak signal anti-interference capabilities in the sampling control circuit.
Innovation Solution
A control module collects the current flowing through a current sampling element and controls the switch element to turn on when the current exceeds a threshold, reducing the delay requirement on the sampling control circuit and enhancing signal anti-interference capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If voltage detection method is used to control switch element, then zero-voltage turn-on can be achieved, but the sampling control circuit requires high sampling speed and has weak signal anti-interference capability due to violent voltage changes
Solution Approach 1:
The patent introduces a current sampling element as an intermediary to indirectly detect the voltage state of the switch element. Instead of directly sampling the violent voltage changes, the circuit samples the current through the current sampling element, which varies smoothly and provides an intermediate signal that is easier to process while still indicating the voltage state for zero-voltage turn-on control
Solution Approach 2:
The patent replaces the electrical voltage sampling method with a current-based control method. By substituting the direct voltage detection approach with current sampling through a current sampling element, the system avoids the problems of violent voltage changes and achieves the same zero-voltage turn-on function with lower sampling requirements and better anti-interference capability
2Ease of operation
If voltage sampling is performed on switch element, then turn-on control can be achieved, but the signal anti-interference capability is weak due to violent voltage changes
Solution Approach 1:
The current sampling element serves as a mediator that converts the violent voltage changes into smooth current variations. The control module samples this intermediate current signal instead of the original voltage signal, thereby maintaining switch control capability while significantly improving signal anti-interference capability
Solution Approach 2:
The patent changes the sampled parameter from voltage to current. By sampling the current through the current sampling element instead of the voltage across the switch element, the system transforms a parameter that changes violently into one that changes smoothly, reducing signal interference while preserving control functionality
Data Source
AI summary
A bridgeless PFC circuit includes: a control module that collects a current flowing through a current sampling element; and when the current flowing through the current sampling element is greater than a first threshold, the control module controls a switch element to be turned on. Based on the current flowing through the current sampling element, the switch element can be controlled to be turned on, thereby implementing zero-voltage turn-on of the switch element. Because the collected current does not change abruptly, a delay requirement on a sampling control circuit included in the control module is lowered, and a signal anti-interference capability of the control module is strong.