Partially Bootstrapped Gate Drive for Low-Loss Wide-Bandgap Switching
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Solution Overview
Problem
Existing gate driving circuits for wide band gap devices face issues with high parasitic resistance, requiring additional power supplies and complex control signals, leading to increased cost, risk of overcharging, and reduced reliability.
Innovation Solution
A partially bootstrapped gate driving circuit using a bootstrap structure with capacitors and diodes to double the output voltage without additional power supplies, controlling capacitance to prevent overcharging and simplify control signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a voltage source driving circuit is used, then the circuit structure is simple, but the switching loss cannot be effectively reduced due to large parasitic resistance in wide band gap devices
Solution Approach 1:
The patent implements dynamic voltage boosting during switching transitions. A bootstrap capacitor charges to twice the supply voltage (2Vcc) and connects to the gate during switching events, providing temporary high-voltage drive current. This dynamic approach allows the simple voltage source structure to achieve low switching loss by delivering high peak current only when needed, rather than maintaining high voltage continuously.
Solution Approach 2:
The bootstrap capacitor is periodically charged during the off-state and discharged during the on-state to provide voltage boosting. This periodic charging and discharging enables the circuit to deliver high drive current during switching transitions while maintaining simple overall structure, effectively reducing switching loss without continuous complex control.
2Speed
If additional power supply is added to improve switching speed, then the switching loss is reduced, but the cost and device complexity increase significantly
Solution Approach 1:
The bootstrap capacitor serves multiple functions: it acts as a voltage booster during switching, provides gate drive energy, and eliminates the need for separate high-voltage power supplies. By making this single component multi-functional, the patent achieves high switching speed without adding complex additional power supply structures.
Solution Approach 2:
The bootstrap capacitor is charged automatically from the supply voltage through diodes during the off-state, and then self-discharges to provide the voltage boost during the on-state. This self-charging and self-discharging mechanism eliminates the need for external control circuits or additional power supplies, reducing device complexity while maintaining high switching speed.
3Loss of energy
If current source driving with inductors is used, then the switching loss can be adjusted, but the circuit volume increases greatly
Solution Approach 1:
The patent extracts and eliminates the inductor component from the driving circuit. Instead of using inductors to generate current, the design uses capacitors (bootstrap capacitors) to store and release energy. This extraction of the inductor significantly reduces circuit volume while maintaining the ability to control switching loss through capacitor selection and control logic.
4Loss of energy
If complex control logic is added to monitor voltage and current, then parasitic oscillation is suppressed and loss is reduced, but the cost increases and reliability decreases
Solution Approach 1:
The patent uses simple, inexpensive components (capacitors, diodes, resistors) instead of complex monitoring circuits. The bootstrap capacitors provide the necessary voltage boosting through passive charge/discharge cycles, eliminating the need for expensive voltage and current monitors. This approach reduces cost and improves reliability by minimizing the number of active components that could fail.
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
Significantly reduces switching loss by 50%-75% and 10%, improves switching speed, and ensures reliable operation without additional hardware or control signals, adapting to varying load conditions.
Implementation Method 1
by controlling the capacitance of a capacitor, an output voltage of the driving circuit automatically drops to the supply voltage of a power supply at the end of the switching process
Implementation Method 2
A partially bootstrapped gate driving circuit using a bootstrap structure with capacitors and diodes to double the output voltage
Data Source
AI summary
The present invention belongs to the technical field of gate driving circuits, and discloses a partially bootstrapped gate driving circuit for reducing switching loss and a control method thereof. The partially bootstrapped gate driving circuit for reducing the switching loss comprises a switching device, PWM, a power supply, signal isolation, non-isolated driving chips, a bootstrap structure, a driving resistor, Mon and Moff. The bootstrap structure is used in the present invention, which can realize voltage doubling output without increasing the power supply, overcomes limitation of parasitic resistance inside a large gate of a wide band gap device, and can significantly reduce the switching loss.