Bridgeless PFC Booster Circuit Reducing Diode Voltage Drop
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Solution Overview
Problem
Conventional PFC booster circuits suffer from significant energy losses due to the 1V forward voltage drop across full wave rectifier diodes, and existing bridgeless solutions face limitations such as high switching noise and the need for multiple boost inductors, which reduce efficiency and increase component count.
Innovation Solution
A PFC booster circuit that utilizes switchable power transistors to operate in both flyback and forward states, minimizing voltage drops by storing and releasing energy in a single inductive element through a controlled diode path, thereby reducing the number of components and enhancing energy transfer efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a full wave rectifier with four diode elements is used in conventional PFC booster circuits, then the circuit can rectify AC mains supply into DC voltage, but the forward voltage drop across the diodes causes significant energy loss (approximately 1% for high line mains voltage and 2% for low line mains voltage)
Solution Approach 1:
The patent removes the traditional full-wave rectifier diodes from the circuit topology. Instead of using four diode elements that cause voltage drops, the invention extracts the rectification function and integrates it directly into the PFC boost circuit operation, where the switch and inductor perform both switching and rectification functions simultaneously. This eliminates the separate rectifier stage and its associated losses.
Solution Approach 2:
The patent merges the rectification function with the PFC boost operation. The same switch and inductor used for power factor correction also perform rectification, combining multiple functions into a single integrated circuit stage. This eliminates the need for separate rectifier diodes and reduces the total component count while improving efficiency.
2Loss of energy
If bridgeless PFC booster circuits are used to reduce diode losses, then energy efficiency improves, but high switching noise is presented to the mains supply
Solution Approach 1:
The patent employs dynamic switching of the power transistor with controlled duty cycles to manage both rectification and PFC functions. By dynamically adjusting the switch timing and duration, the circuit achieves efficient power transfer while controlling electromagnetic interference and switching noise injected into the mains supply.
3Loss of energy
If bridgeless PFC booster circuits are used to reduce diode losses, then energy efficiency improves, but two separate boost inductors are required
Solution Approach 1:
The patent combines the boost inductor function with the existing PFC inductor, using a single inductor to perform both energy storage for PFC and the secondary boost function. This integration eliminates the need for two separate inductors, reducing component count, circuit complexity, and cost while maintaining the efficiency benefits of bridgeless topologies.
4Reliability
If conventional PFC booster circuits with full wave rectifiers are used, then the circuit structure is well-established, but the forward voltage drop across diodes significantly reduces circuit efficiency
Solution Approach 1:
The patent replaces the passive diode-based rectification mechanism with an active switching mechanism using a power transistor and control circuitry. This substitution allows for controlled current flow and voltage regulation, eliminating the unavoidable forward voltage drops of diodes while maintaining reliable and stable circuit operation through active management.
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 achieves efficient power transfer with reduced voltage drops across diode components, minimizing the number of components needed and increasing overall energy efficiency, resulting in lower heat generation and operational costs.
Implementation Method 1
an inductor is charged from an AC power supply through the control of two power transistors, where a first power transistor is reverse biased and a second power transistor is switched on
Implementation Method 2
the stored energy in the inductor is transferred via a diode element to a capacitor element
Data Source
AI summary
A power factor correction booster circuit for connection to an alternating current (AC) power source including a first circuit portion arranged to be active over a first AC half cycle of the power source, the first circuit portion including: a first AC input node in connection with a source node of a first power transistor, a first node of an inductive element in connection with a drain node of the first power transistor, a second node of the inductive element in connection with a drain node of a second power transistor, a second AC input node in connection with a source node of the second power transistor, an anode of a first semiconductor diode element in connection with the second node of the inductive element, a cathode of the first semiconductor diode element in connection with a first node of a first output capacitor element, and a second node of the first output capacitor element in connection with the second AC input node, wherein the first and second power transistors are controllable to switch the first circuit portion between a forward mode and a flyback mode, such that in the forward mode the inductive element stores energy from the AC power source, and in the flyback mode the stored energy from the inductive element is transferred to the first output capacitor through the first semiconductor diode element.