Half-Bridge Gate Driver Slew Control for Lower EMI and Charge Recycling
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Solution Overview
Problem
Conventional half-bridge drivers face issues with electromagnetic interference due to improper slew rate control, require high-voltage devices, result in high manufacturing costs and circuit area, and suffer from power loss due to inability to recycle gate-source capacitor charges.
Innovation Solution
A half-bridge driver with slew rate adjustment functionality, utilizing a switch selection circuit and slew rate adjustment circuits to control the slew rate of high-side and low-side switches, reducing the need for high-voltage devices and recycling gate-source capacitor charges, thereby minimizing electromagnetic interference and power loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If conventional high-voltage drivers are used to adjust driving voltage, then the driving capability is improved, but the number of high-voltage devices increases, circuit area increases, and manufacturing cost increases
Solution Approach 1:
The patent changes the voltage parameter range by operating the slew rate adjustment circuit in the low-voltage range (0 to 5V) instead of requiring high-voltage operation. This is achieved by using a bootstrap capacitor to provide the necessary voltage boosting, allowing the same circuit to achieve high-voltage driving capability without using high-voltage devices, thereby reducing device complexity and manufacturing cost while maintaining driving capability
2Measurement precision
If gate-source voltage sensing circuit and drain-source voltage sensing circuit are added to adjust slew rate, then the slew rate control precision is improved, but the circuit area increases
Solution Approach 1:
The patent extracts and removes the unnecessary gate-source voltage sensing circuit and drain-source voltage sensing circuit from the conventional design. Instead of sensing both voltages separately, the invention uses a simplified approach that only requires sensing the output voltage, significantly reducing the circuit area while maintaining sufficient slew rate control precision through the low-voltage adjustment circuit
3Device complexity
If conventional half-bridge driver operates without charge recycling, then the circuit simplicity is maintained, but the power loss increases
Solution Approach 1:
The patent recovers and recycles the charge that would otherwise be lost from the gate-source capacitor during switching operations. The low-voltage slew rate adjustment circuit is designed to capture and reuse these charges, converting what would be wasted energy into useful charging current for the next switching cycle, thereby reducing power loss without significantly increasing circuit complexity
4Device complexity
If slew rate is not properly controlled, then the circuit simplicity is maintained, but electromagnetic interference occurs
Solution Approach 1:
The patent applies preliminary action by pre-adjusting the slew rate of the output voltage through the low-voltage adjustment circuit before the main switching operation occurs. The pulse width control unit generates adjustment signals in advance that shape the voltage transition, preventing electromagnetic interference from occurring in the first place while maintaining relatively simple circuit architecture
Data Source
AI summary
A half-bridge driver drives a half-bridge circuit. The half-bridge driver includes a switch selection circuit and at least one slew rate adjustment circuit, wherein the slew rate adjustment circuit includes a pulse-width control unit, an adjustment pulling unit and a halt adjustment pulling unit. The switch selection circuit generates a source current or a sink current to correspondingly pull up or pull down the gate-source voltage of the upper switch or the lower switch, thereby turning-on or turning-off the upper switch or the lower switch. The adjustment pulling unit is for adjusting the pulling-up or pulling-down of the gate-source voltage of the upper switch or the lower switch. The stop-adjustment pulling unit is for stopping adjusting the pulling-up or pulling-down of the gate-source voltage of the upper switch or the lower switch.