Current-Triggered Synchronous Rectifier for Power Loss Reduction
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Solution Overview
Problem
Conventional bridge rectifiers using diodes suffer from inefficiency due to forward voltage drop and heat dissipation issues, particularly in low-voltage and high-frequency power converters, which reduces overall efficiency and reliability.
Innovation Solution
A current-triggered synchronous rectifier is developed, utilizing MOSFET devices with a current monitor to switch between ON and OFF states based on predetermined current thresholds, replacing diodes in a full-wave rectifier configuration to minimize heat loss and prevent short circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If diodes are used in bridge rectifiers, then full-wave rectification is achieved, but forward voltage drop and heat dissipation occur reducing efficiency
Solution Approach 1:
The patent changes the operating parameters of the rectifier by using MOSFETs instead of diodes, utilizing their voltage-controlled resistance特性 to achieve synchronous switching. This parameter change allows the rectifier to operate with much lower conduction losses while maintaining reliability through controlled switching behavior.
Solution Approach 2:
The patent substitutes the passive mechanical diode structure with an active electronic MOSFET-based synchronous switching system. This replacement transforms the rectification mechanism from passive conduction to active controlled switching, dramatically reducing power losses while improving reliability through precise gate control.
2Loss of energy
If MOSFETs replace all diodes in bridge rectifier, then power loss is reduced, but short circuiting between input and output terminals may occur
Solution Approach 1:
The patent segments the bridge rectifier into four independent MOSFET switching circuits, each with its own gate control. This segmentation allows independent optimization of each switching element and simplifies the overall control strategy by treating each quadrant separately, reducing the complexity of coordinated switching while maintaining low power loss.
Solution Approach 2:
The patent implements feedback control through current sensing circuits that monitor the output current and provide feedback signals to the gate control circuits. This feedback mechanism prevents short circuiting by detecting abnormal current conditions and adjusting the switching signals accordingly, enabling safe replacement of all diodes with MOSFETs while maintaining simple control.
3Speed
If diodes are used in high frequency switching power supplies, then rectification is achieved, but heat dissipation reduces component reliability
Solution Approach 1:
The patent employs periodic gate signals to control the MOSFETs at the switching frequency, synchronizing the switching action with the input AC waveform. This periodic control enables high-frequency operation with minimal conduction losses, as the MOSFETs spend most time in the low-resistance ON state, significantly reducing heat dissipation compared to diode rectifiers at the same frequency.
4Loss of energy
If Schottky diodes are used to minimize voltage drop, then forward voltage loss is reduced, but device complexity and cost increase
Solution Approach 1:
The patent implements self-service control where the gate control circuits automatically generate appropriate switching signals based on the input voltage waveform and load conditions, without requiring external complex control circuits. The MOSFETs self-regulate their conduction states through the inherent properties of the circuit, achieving minimal voltage drop losses while maintaining simple overall circuit architecture.
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 heat dissipation, enhancing the efficiency and reliability of power converters by up to 50% compared to traditional diode-based rectifiers, while preventing short circuits through precise current monitoring and switching control.
Implementation Method 1
a current monitor configured to monitor a drain-current flowing through the drain terminal and to send a gate signal to the gate terminal
Implementation Method 2
in the ON state, a current path is provided between the source and the drain terminals, having the characteristics of an ohmic resistor
Implementation Method 3
the closed electronic switch 131 of the MOSFET 130 behaves as an ohmic resistor
Implementation Method 4
In the OFF state, current is blocked
Data Source
AI summary
A current-triggered synchro-rectifier comprising an electronic switch configured to be in its ON setting when the current flowing through its cathode exceeds a predetermined threshold. The electronic switch may include a half-wave rectifier wired to the source terminal and the drain terminal of a MOSFET device, and a current monitor configured to monitor the drain-current flowing through the drain terminal. The current monitor sends a gate signal to the gate terminal such that the MOSFET is switched to its ON state when the drain-current exceeds a first threshold current and the MOSFET is switched to its OFF state when the drain-current falls below a second threshold current. Usefully, the synchro-rectifier may be incorporated into a full-wave rectifier.