Synchronous Full-Bridge Rectifier Control for Low-Loss Surge Protection
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Solution Overview
Problem
Conventional bridge rectifiers using diodes suffer from high power loss due to forward voltage-drop, especially at high current conditions, and are prone to damage from abnormal conditions like lightning surges or ESD, necessitating a more efficient and protective solution for AC-to-DC power conversion.
Innovation Solution
A synchronous full-bridge rectifier circuit employing transistors (MOSFETs) with a rectifier switch controller that generates detection signals and driving signals to control the transistors, preventing short-through damage and optimizing power conversion by using clamping transistors to manage voltage and current thresholds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If rectifier diodes are used in a bridge rectifier, then the circuit structure is simple, but the forward voltage-drop is high causing significant power loss
Solution Approach 1:
The patent changes the key parameter from using diodes (with fixed forward voltage-drop) to using transistors (with controllable on-resistance). By changing the switching state of transistors, the circuit dynamically selects between different conduction paths, effectively reducing the voltage drop from typically >1V to much lower values, thereby resolving the power loss issue while maintaining reasonable structural complexity
Solution Approach 2:
The invention introduces dynamic control through switching signals that change the state of transistors based on the AC input polarity. This dynamic switching enables the circuit to adaptively select conduction paths, making the rectifier efficient across different operating conditions while maintaining a relatively simple overall structure
2Loss of energy
If transistors are used to replace rectifier diodes for high efficiency, then power loss is reduced, but the circuit becomes prone to short-through damage from abnormal conditions
Solution Approach 1:
The patent implements preliminary protective actions by using detection transistors that continuously monitor the AC input voltage before the main power switching transistors are activated. These detection transistors identify abnormal conditions (such as lightning surges or ESD) in advance and generate protection signals to prevent the main transistors from being damaged, thereby ensuring reliability while maintaining the low power loss benefits of using transistors
Solution Approach 2:
The invention introduces detection transistors as intermediary elements between the AC input and the main power transistors. These intermediaries perform the function of monitoring and protection, isolating the main transistors from direct exposure to harmful voltage spikes and transient conditions, thus protecting the high-efficiency transistor-based rectifier from short-through damage
3Reliability
If detection transistors are added to prevent short-through damage, then reliability is improved, but the device complexity increases
Solution Approach 1:
The detection transistors serve multiple functions: they detect abnormal voltage conditions, generate protection signals, and can also contribute to the rectification process during normal operation. This multi-functionality reduces the need for separate dedicated protection circuits, thereby limiting the increase in overall device complexity while achieving improved reliability
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 significantly reduces power loss and protects the rectifier circuit from damage by efficiently controlling transistor operation based on detection signals, ensuring low switching loss and effective power management across varying load conditions.
Implementation Method 1
the first low-side transistor is turned on after the body-diode of the first low-side transistor is turned on; the second low-side transistor is turned on after the body-diode of the second low-side transistor is turned on
Data Source
AI summary
A synchronous full-bridge rectifier circuit includes: a first high-side transistor, a first low-side transistor, a second high-side transistor and a second low-side transistor which are configured to generate a DC power source from an AC power source, wherein the first high-side transistor and the first low-side transistor are coupled to a live wire of the AC power source, and the second high-side transistor and the second low-side transistor are coupled to a neutral wire of the AC power source; a first detection transistor, coupled to the live wire and configured to generate a first detection signal; and a second detection transistor, coupled to the neutral wire configured to generate a second detection signal; wherein the first low-side transistor is turned on after the body-diode of the first low-side transistor is turned on; the second low-side transistor is turned on after the body-diode of the second low-side transistor is turned on.