Bridgeless PFC Current Sampling via Segmented Units
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Solution Overview
Problem
The reliability of power supply in bridgeless Power Factor Correction (PFC) circuits is compromised due to sampling delays when the AC input voltage is high, leading to loss of control of the control loop.
Innovation Solution
The use of three sampling units to sample currents through a switch transistor and a diode in the bridgeless PFC circuit, allowing for more comprehensive and flexible control by delivering sampled signals to a control system, which enables proper representation of currents in the boost inductor and prevents loss of control even at high AC input voltages and small duty cycles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If bi-resistor sampling or bi-current-transformer sampling is used in bridgeless PFC circuit, then the circuit structure is simplified compared to traditional PFC, but sampling delay occurs when AC input voltage is very high causing loss of control loop reliability
Solution Approach 1:
The patent divides the sampling function into three separate sampling units instead of using a single sampling method. Each sampling unit is configured to sample current at different points in the bridgeless PFC circuit, allowing the system to overcome the limitations of any single sampling approach and maintain reliable control loop operation across all AC input voltage conditions.
Solution Approach 2:
The patent transitions from a two-dimensional sampling approach (bi-resistor or bi-current-transformer) to a three-dimensional sampling approach by adding a third sampling unit. This dimensional expansion in the sampling architecture provides additional measurement perspectives that eliminate the sampling delay problem occurring in high AC input voltage conditions.
2Reliability
If the number of sampling units is increased from two to three, then sampling reliability is improved, but device complexity increases
Solution Approach 1:
The three sampling units are designed to perform multiple functions within the bridgeless PFC circuit. Each sampling unit not only samples current but also provides information about different operational states of the circuit, allowing the increased number of units to contribute to overall system functionality rather than merely adding redundant components.
Data Source
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AI summary
Disclosed are an induction current sampling device and method for a bridgeless PFC circuit. The device includes a first sampling unit, a second sampling circuit and a third sampling circuit, wherein the the first sampling unit, connected in serial with a first switch transistor of the bridgeless PFC circuit, is configured to sample a current flowing through the first switch transistor to acquire a first sampling signal V1; the the second sampling unit, connected in serial with a second switch transistor of the bridgeless PFC circuit, is configured to sample a current flowing through the second switch transistor to acquire a second sampling signal V2; and the third sampling unit, with one terminal connected with a ground of the bridgeless PFC circuit and the other terminal connected with a negative output of a PFC capacitor of the bridgeless PFC circuit, is configured to sample a current flowing through a boost diode of the bridgeless PFC circuit to acquire a third sampling signal V3.