Resonant PFC Converter Control for Isolated High-Power Operation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
State of the art isolated PFC converters operate inefficiently at higher power inputs and frequencies due to inadequate control mechanisms, particularly in Flyback circuits, and resonant PFC converters lack detailed control schemes for efficient operation.
Innovation Solution
A resonant power factor correction converter with a transformer, high-side and low-side switches, a resonant tank circuit, and sensing circuits for closed-loop control, enabling efficient operation at higher powers by regulating output voltage and current through a state machine-driven switching mechanism.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Flyback circuit topology is used for isolated PFC converter, then galvanic isolation is achieved, but efficiency deteriorates at higher power input and frequency
Solution Approach 1:
The patent transitions from hard-switching Flyback topology to resonant soft-switching topology, fundamentally changing the switching parameters and operating mode to achieve both galvanic isolation and high efficiency at higher power levels
Solution Approach 2:
The patent employs resonant oscillation in the tank circuit (comprising inductor L and capacitor C) to achieve soft switching, utilizing vibratory energy exchange to minimize switching losses while maintaining isolation through the transformer
2Loss of energy
If resonant PFC converter is used for higher power operation, then efficiency is improved through soft-switching, but control mechanism complexity increases due to lack of detailed control schemes
Solution Approach 1:
The patent implements a closed-loop control system with sensing circuits that detect resonant current and voltage, feeding back to the control circuit to dynamically adjust switching timing and maintain optimal resonant operation across varying power conditions
Solution Approach 2:
The resonant tank circuit naturally oscillates at its resonant frequency, and the control circuit exploits this self-oscillating behavior to simplify control, requiring only timing synchronization rather than complex frequency regulation
3Device complexity
If rudimentary two-point frequency control or peak control in open-loop is used, then device complexity is reduced, but output voltage regulation precision deteriorates
Solution Approach 1:
The patent employs closed-loop feedback control where the control circuit continuously monitors output voltage and resonant current, adjusting switching timing in real-time to maintain precise output voltage regulation while adapting to varying input conditions
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 converter achieves efficient power factor correction with sinusoidal input current and regulated output voltage, suitable for higher power inputs, while providing galvanic isolation and safety extra-low voltage.
Implementation Method 1
a transformer configured to isolate an input circuit and an output circuit of the converter
Implementation Method 2
resonant PFC converters do operate efficiently at higher power (and higher frequency) due to their soft-switching characteristics
Data Source
Figure 1
Figure 2
Figure 3
AI summary
Disclosed is a resonant power factor correction, PFC, converter (1), comprising a transformer (101, Tr2) configured to isolate an input circuit (102) and an output circuit (103) of the converter (7), the input circuit (102) comprising an input capacitance (104, C2), configured to level out a rectified mains voltage (401, Vin) of the converter (7); a high-side, HS, switch (105) and a low-side, LS, switch (106) connected in series and arranged in parallel to the input capacitance (104, C2); and a resonant tank circuit (107, Ls, Ls1, Ls2, Cs, Cp), connected between the transformer (101, Tr2) and a common terminal of the HS switch (105) and the LS switch (106). The converter (1) further comprises a first sensing circuit (108, R7, R8), configured to sense the rectified mains voltage (401, Vin); a second sensing circuit (109, R9, R10, Tr2a), configured to sense an output voltage (402, Vout) of the converter (7); a third sensing circuit (110, Tr3), configured to sense a rectified resonant current (404, Ires_rect) of the resonant tank circuit 107); and a control circuit (2, Controller). The control circuit (2, Controller) is configured to determine a control variable (405, Vref) for regulation of the output voltage (402, Vout) in accordance with a given setpoint (406, Vout_ref); determine a threshold variable (407, Ires_ref) for the rectified resonant current (404, Ires_rect) in accordance with the control variable (405, Vref) and the rectified mains voltage (401, Vin); determine a first compare result (408, CMP1) in accordance with the rectified resonant current (404, Ires_rect) and its threshold variable (407, Ires_ref); and drive the HS switch (105) and the LS switch (106) in turns in accordance with a state machine (3) being stimulated through the first compare result (408, CMP1). The converter (1) is especially suitable for higher power input.