AC-DC Converter Topology for PFC and Tight Voltage Regulation
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Solution Overview
Problem
Existing AC-DC electrical power converters with power factor correction and tight regulation of output voltage require two separate power stages and inductances, leading to increased volume, cost, and losses.
Innovation Solution
Combining the two power stages into a single AC-DC switch mode electrical power converter using a transformer with magnetizing and leakage inductances to regulate both power flows, eliminating the need for separate inductances and reducing volume and losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a three-terminal topology is used to provide good load regulation and transient response, then power quality improves, but the converter requires an additional output capacitor and becomes unsuitable for single-sided ground applications
Solution Approach 1:
The patent divides the power converter into two separate converters: a primary side converter that performs power conversion, and a secondary side converter that performs voltage inversion. This segmentation allows each converter to be optimized independently, with the primary converter using a simpler two-terminal topology and the secondary converter handling the polarity inversion function, thereby eliminating the need for an additional output capacitor on the primary side.
Solution Approach 2:
The patent introduces a secondary side converter as an intermediary component between the primary converter and the load. This intermediary inverts the rectified voltage polarity, enabling the primary converter to operate with a simple two-terminal topology while still achieving the functionality of a three-terminal converter. The intermediary transfers the inversion function from the primary to the secondary side.
2Speed
If a three-terminal topology is used, then transient response improves, but isolation between primary and secondary sides is compromised
Solution Approach 1:
The patent segments the voltage inversion function from the power conversion function. The primary converter focuses on efficient power conversion with inherent isolation through the transformer, while the secondary converter handles voltage inversion. This segmentation maintains isolation between primary and secondary sides while achieving fast transient response through optimized control of each independent converter.
Solution Approach 2:
The secondary side converter acts as an intermediary that restores isolation by handling the voltage inversion function separately. This allows the primary converter to maintain galvanic isolation through the transformer, while the secondary converter provides the necessary polarity inversion without compromising the isolation barrier.
3Device complexity
If a two-terminal topology is used, then device complexity reduces, but load regulation and transient response deteriorate
Solution Approach 1:
The patent introduces a secondary side converter as an intermediary that compensates for the limitations of the simple two-terminal primary converter. This intermediary actively regulates the output voltage and provides fast transient response by inverting the rectified voltage and controlling the output capacitor charging/discharging cycles, thereby achieving load regulation without increasing primary converter complexity.
Solution Approach 2:
The secondary side converter implements feedback control to regulate the output voltage. By monitoring the output voltage and adjusting the switching duty cycle of the secondary converter, the system maintains stable voltage under varying load conditions, compensating for the lack of inherent load regulation in the simple two-terminal primary converter topology.
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 proposed converter achieves power factor correction and tight output voltage regulation with reduced volume and cost by integrating the power stages, utilizing a single transformer to handle both power conversion functions.
Implementation Method 1
a transformer having a primary winding and a secondary winding
Implementation Method 2
a rectifier circuit coupled to the secondary winding of the transformer and configured to convert the AC voltage to a rectified voltage
Implementation Method 3
an output capacitor coupled in parallel to a load
Data Source
Figure 1~2
Figure 3
Figure 4A
AI summary
An AC-DC switch mode electrical power converter is proposed. Comprises an input half- bridge comprising an input capacitive leg and an input switching leg; an output half-bridge comprising an output capacitive leg and an output switching leg; and a transformer. A secondary winding of the transformer is connected between a middle point of the output capacitive leg and a middle point of the output switching leg, while a primary winding is connected in series to an AC input voltage source. An input current and an output voltage are controlled based on control variables including a duty cycle of the input half-bridge, a duty cycle of the output half-bridge, and a phase shift between the duty cycle of the input half- bridge and the duty cycle of the output half-bridge. In some embodiments, the input capacitive leg, input switching leg, output capacitive leg and/or output switching leg can be replaced by a switched capacitor leg.