Bi-directional Switch Gate Drive Using Floating Capacitor
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Solution Overview
Problem
Conventional methods for controlling the gate of a bi-directional switch in switched mode power converters require an additional transformer, which increases cost and board space, and are inefficient in switching operations.
Innovation Solution
A technique that uses floating supply capacitors to charge the gate of the first transistor during a predetermined moment in the switching cycle, eliminating the need for a transformer and minimizing conduction losses, by connecting the top plates of capacitors together with a boost switch when the voltage across the bi-directional switch is at a minimum.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an additional transformer is used to control the gate of the bi-directional switch, then the switching operation can be performed, but the cost and board space increase
Solution Approach 1:
The patent extracts and eliminates the additional transformer from the circuit by using the existing transformer's auxiliary winding to provide the gate drive voltage. This removes the unnecessary component while maintaining the switching function, thereby reducing board space and cost.
Solution Approach 2:
The auxiliary winding of the existing transformer is made to serve dual purposes: providing isolation for the control circuit and simultaneously providing the gate drive voltage for the bi-directional switch. This multi-functionality eliminates the need for a separate transformer dedicated to gate control.
2Reliability
If an additional transformer is used to control the gate of the bi-directional switch, then the switching operation can be performed, but the cost increases
Solution Approach 1:
The patent extracts and eliminates the additional transformer from the circuit by using the existing transformer's auxiliary winding to provide the gate drive voltage. This removes the unnecessary component while maintaining the switching function, thereby reducing board space and cost.
Solution Approach 2:
The auxiliary winding of the existing transformer is made to serve dual purposes: providing isolation for the control circuit and simultaneously providing the gate drive voltage for the bi-directional switch. This multi-functionality eliminates the need for a separate transformer dedicated to gate control.
3Productivity
If the gate voltage is not accurately controlled, then the switching efficiency decreases, but conventional methods require complex transformer circuits
Solution Approach 1:
The patent introduces a capacitor connected to the auxiliary winding as an intermediary energy storage element. This capacitor smooths the rectified voltage from the auxiliary winding and provides a stable, accurate gate drive voltage, improving switching efficiency while keeping the control circuit simple.
Solution Approach 2:
The patent replaces the complex transformer-based gate drive system with a simpler capacitor-based voltage stabilization system. The capacitor substitutes for the need for additional transformer circuits, providing accurate gate voltage control through passive energy storage and smoothing.
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
Enables efficient and accurate gate switching of the first transistor without a transformer, reducing conduction losses and ensuring the gate voltage is close to the floating supply voltage, thereby improving the overall efficiency of the bi-directional switch control.
Implementation Method 1
a floating supply capacitor associated with the second transistor, wherein the gate of the first transistor and/or the supply of its gate drive circuit is charged by the floating supply capacitor
Data Source
AI summary
A bi-directional switch for a power converter comprises first and second transistors (SW1, SW2) and a floating supply capacitor (C2) associated with the second transistor (SW2). The drive circuit and/or gate of the first transistor (SW1) is charged by the floating supply capacitor (C2) of the second transistor (SW2). The charging takes place at a predetermined moment in the switching cycle, and in particular at a moment in the switching cycle when the voltage across the bi-directional switch is substantially a minimum.