High-Voltage Synchronous Rectifier for Fast PFC Mode Switching
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Solution Overview
Problem
Existing power factor correction circuits in switching-mode power supplies suffer from increased losses and inefficiencies, particularly at high-voltage and high-frequency power inputs, due to the use of simple diodes for isolation, which are exacerbated by varying load conditions.
Innovation Solution
A power factor high-voltage end synchronous rectifier utilizing a bridge rectifying module, power factor module, and high-voltage synchronous rectifier, incorporating wide bandgap compound semiconductors and a current detector, to control the conduction modes and reduce power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If simple diodes are used for isolation in power factor correction circuits, then device complexity is reduced, but power loss increases especially at high-voltage and high-frequency inputs
Solution Approach 1:
The patent changes the key parameter from simple diode isolation to synchronous rectification using active switches (MOSFETs or IGBTs), transforming the isolation mechanism from passive to active control. This parameter change enables dynamic adjustment of the isolation components to minimize power loss while maintaining system complexity at acceptable levels through integrated control circuits.
Solution Approach 2:
The patent replaces the mechanical/passive diode isolation system with an electronically controlled synchronous rectification system. The active switches are controlled by synchronization circuits that detect the input voltage waveform and generate appropriate gate signals, substituting passive component behavior with active electronic control to reduce power losses.
2Productivity
If switching frequency is increased to reduce SMPS size, then power density increases, but power loss in traditional PFC circuits increases
Solution Approach 1:
The patent employs periodic synchronous control where the isolation switches are turned on and off in synchronization with the input voltage waveform. The control circuit detects zero-crossing points and generates gate signals at appropriate intervals, creating periodic action that maintains low power loss even at high switching frequencies by ensuring switches are conductive only when necessary.
Solution Approach 2:
The patent incorporates feedback mechanisms where the control circuit monitors the input voltage waveform and adjusts the switching timing and duration of the isolation switches accordingly. This feedback control ensures optimal switching moments are selected, minimizing power loss while maintaining high power density operation.
3Use of energy by moving object
If synchronous rectification is implemented, then power consumption is reduced, but device complexity and control requirements increase
Solution Approach 1:
The patent designs the synchronous rectification control circuit to perform multiple functions: detecting input voltage zero-crossings, generating synchronized gate signals for isolation switches, and adapting to different operating modes (DCM, CCM, QR). This multi-functionality reduces the need for separate control circuits while achieving power consumption reduction through synchronous operation.
Solution Approach 2:
The control circuit automatically synchronizes with the input voltage waveform by detecting zero-crossing points and self-adjusts the switching timing without external intervention. The system serves itself by using the input voltage waveform as the reference signal for generating gate signals, reducing the need for complex external control mechanisms.
Data Source
AI summary
A power factor high-voltage end synchronous rectifier includes a bridge rectifying module, a power factor module and a high-voltage synchronous rectifier, whereby the high-voltage synchronous rectifier obtains the state of a second power outputted by the bridge rectifying module through a current detector and generates first and second control signals. The first control signal adjusts the on/off state of a first wide bandgap compound semiconductor of the power factor module, and the second control signal adjusts the on/off state of a second wide bandgap compound semiconductor of the power factor module, allowing the high-voltage synchronous rectifier to generate a plurality of control signals at the same time, so that the second power of the power module can be switched between continuous conduction mode (CCM), discontinuous conduction mode (DCM) and quasi resonant mode (QR) in a very short time (can be regarded as zero second in an ideal state).