Switched-Capacitor Gate Driver With Series-Parallel Gate Charging
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Solution Overview
Problem
Conventional gate-driving circuits for high power, high current transistors suffer from issues such as voltage overshoot, slow transitions, and excessive power dissipation due to parasitic inductance and capacitance resonance, which can damage the transistors and increase power consumption.
Innovation Solution
A switched-capacitor gate driver with multiple switching cells and a controller that operates in series and parallel states to stepwise charge and discharge the gate capacitance, using a supply voltage or dc-dc conversion, to achieve efficient and controlled voltage transitions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional gate-driving circuits are used to switch power transistor gates between rails, then the transistors can be switched between on and off states, but voltage overshoot and ringing occur due to parasitic inductance and capacitance resonance
Solution Approach 1:
The gate driver is divided into multiple switching cells (first switching cell, second switching cell, etc.), each capable of operating in series or parallel configurations. This segmentation allows gradual voltage application to the gate, preventing sudden voltage spikes and ringing caused by parasitic resonance.
Solution Approach 2:
The switching cells dynamically reconfigure between series and parallel states based on the desired gate voltage level. During turn-on, cells switch from parallel to series to progressively increase voltage; during turn-off, they reverse the process, enabling controlled voltage transitions without overshoot.
2Reliability
If resistance is added to damp the wiring/gate capacitance resonance, then voltage overshoot is reduced, but voltage transitions become slow causing excessive power dissipation
Solution Approach 1:
The gate driver applies voltage in periodic steps through multiple switching cells rather than as a single abrupt transition. Each switching cell contributes a voltage step, creating a controlled periodic charging sequence that achieves fast transitions without requiring excessive damping resistance.
Solution Approach 2:
The circuit changes the voltage application parameter from a single-rail abrupt switch to a multi-stage stepped voltage increase. By controlling the switching state of each cell (series/parallel configuration), the gate voltage is raised in controlled increments, achieving fast transitions with minimal power loss.
3Productivity
If significant gate capacitance is switched between rails using traditional gate-driving circuits, then the power transistors can be driven, but significant power is expended to switch the gate capacitances
Solution Approach 1:
The switched-capacitor gate driver recovers energy during the switching process by using capacitive coupling between switching cells. When cells transition between series and parallel states, energy is transferred and reused rather than dissipated, significantly reducing the power required to drive the gate capacitance compared to traditional rail-to-rail switching.
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 effectively mitigates ringing and overshoot, reduces power dissipation, and ensures fast, efficient switching of high voltage transistors by recovering energy during transitions.
Implementation Method 1
each switching cell of the plurality of switching cells has a capacitor and is operable in at least a series-state and parallel-state, the parallel-state using the power supply voltage to charge the capacitor, and the series-state coupling the charged capacitor to raise voltage on the load capacitance
Data Source
AI summary
A circuit for driving a gate of a power semiconductor device includes multiple switching cells, each switching cell operable in a series-state and parallel-state and having an output coupled to a first terminal of an energy storage component, the output coupled through a first switching device to an input. A second switching device is coupled to a second terminal of the energy storage component and to the first input, and a third switching device is coupled to the second terminal of the energy storage component and to a different energy source or a second output of another of the plurality of switching cells. A controller generates control signals to switch the switching cells between a series-state and a parallel-state.