Forward Converter Compensation Winding for Low-Voltage PFC
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Solution Overview
Problem
Conventional forward converter circuits face inefficiencies and demagnetization issues when input AC power is low, leading to compromised power factor correction and increased system interference, which cannot meet stringent regulatory requirements.
Innovation Solution
A forward converter with a voltage conversion device, switch, and auxiliary device that stores energy and generates a compensation voltage, eliminating current dead zones and providing electrical isolation without additional complex structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional forward circuit is used, then electrical isolation is achieved, but current dead zone occurs when input AC power is low voltage
Solution Approach 1:
The patent introduces a compensating winding as an intermediary element that generates a compensating voltage to bridge the voltage gap when input voltage is low. This compensating voltage acts as a mediator that enables current flow through the circuit even when the induced voltage from the transformer is insufficient, thereby eliminating the current dead zone while maintaining electrical isolation through the transformer.
2Reliability
If additional transformer is added to meet demagnetization requirement, then demagnetization is achieved, but device complexity and cost increase
Solution Approach 1:
The patent makes the transformer serve multiple functions: it provides electrical isolation, voltage transformation, and demagnetization all through a single device. The demagnetization function is achieved by utilizing the inherent properties of the transformer core and winding configuration, eliminating the need for separate demagnetization circuits or additional transformers. This multi-functional approach reduces device complexity and cost while meeting all requirements.
3Reliability
If conventional fly-back structure is used, then electrical isolation is achieved, but conversion efficiency is poor
Solution Approach 1:
The patent inverts the conventional fly-back approach by using a forward converter topology where the switch conducts current during the on-state to transfer energy directly to the output through the transformer. This inversion of the energy transfer timing and method reduces energy losses associated with fly-back's discontinuous conduction mode and improves overall conversion efficiency while maintaining electrical isolation through the transformer.
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 high conversion efficiency, meets demagnetization requirements, reduces current dead zones, and ensures high power factor and low harmonic rates, while being compact and lightweight.
Implementation Method 1
The voltage conversion device includes a primary winding and a secondary winding and is configured to convert an input voltage into an output voltage
Implementation Method 2
The auxiliary device is connected to the voltage conversion device, stores electrical energy released by the voltage conversion device and generating a compensation voltage when the switch is cut off
Data Source
Figure 1~2
Figure 3~4
Figure 5
AI summary
A forward converter (1, 1_1, 1_2, 1_3, 1_4, 1_5, 1_6) includes a voltage conversion device (20, 20_1, 20_2, 20_3, 20_4, 20_5, 20_6), a switch (10, 10_1, 10_2, 10_3, 10_4, 10_5, 10_6) and an auxiliary device (30, 30_1, 30_2, 30_3, 30_4, 30_5, 30_6). The voltage conversion device (20, 20_1, 20_2,20_3, 20_4, 20_5,20_6) includes a primary winding (201, N1) and a secondary winding (202, N2), and is configured to convert an input voltage (Vi) into an output voltage (Vo). The switch (10, 10_1, 10_2, 10_3, 10_4, 10_5, 10_6) is connected to the voltage conversion device (20, 20_1, 20_2, 20_3, 20_4, 20_5, 20_6), and is switched to make the voltage conversion device (20, 20_1, 20_2, 20_3, 20_4, 20_5, 20_6) receive or not receive the input voltage (Vi). The auxiliary device (30, 30_1, 30_2, 30_3, 30_4, 30_5, 30_6) is connected to the voltage conversion device (20, 20_1, 20_2, 20_3, 20_4, 20_5, 20_6). When the switch (10, 10_1, 10_2, 10_3, 10_4, 10_5, 10_6) is cut off, the auxiliary device (30, 30_1, 30_2, 30_3, 30_4, 30_5, 30_6) stores electrical energy released by the voltage conversion device (20, 20_1, 20_2, 20_3, 20_4, 20_5, 20_6) and generates a compensation voltage (Vca), and when the switch (10, 10_1, 10_2, 10_3, 10_4, 10_5, 10_6) is turned on, the auxiliary device (30, 30_1, 30_2, 30_3, 30_4, 30_5, 30_6) provides the compensation voltage (Vca), wherein the compensation voltage (Vca) and the input voltage (Vi) have same polarity. The present disclosure further provides a forward power factor corrector including the forward converter (1, 1_1, 1_2, 1_3, 1_4, 1_5, 1_6) described above and a rectifying device.