Semiconductor Device With Separate Drivers For Synchronized Switching
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Solution Overview
Problem
Conventional high-voltage switching circuits face challenges in achieving fast switching speed while preventing current leakage or breakdown, particularly when normally-off elements turn off before normally-on elements, leading to unstable switching performance and potential overvoltage issues.
Innovation Solution
A semiconductor device configuration that includes a normally-on element and a normally-off element connected in series, with a diode and capacitor between the gate of the normally-on element and the low-voltage source, and separate drivers for each element, allowing simultaneous and stable control of their gate voltages to prevent overvoltage and ensure synchronized switching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a common driver is used to control both normally-off element and normally-on element, then device complexity is reduced, but switching speed is limited by parasitic capacitance of normally-on element
Solution Approach 1:
The patent divides the control system into separate drivers: a first driver controls the normally-on element while a second driver controls the normally-off element. This segmentation allows each driver to be optimized independently, enabling the second driver to achieve fast switching for the normally-off element without being constrained by the parasitic capacitance of the normally-on element that would limit a common driver approach.
2Speed
If normally-off element switches off before normally-on element, then switching speed is improved, but overvoltage is applied to normally-off element causing current leakage or breakdown
Solution Approach 1:
The patent employs a delay circuit in the second driver that delays the turn-off signal for the normally-off element. This preliminary timing adjustment ensures that the normally-on element turns off first, establishing a safe voltage condition before the normally-off element turns off. This prevents overvoltage stress and current leakage while still achieving fast switching through the normally-off element's inherent characteristics.
3Strength
If normally-on element is used alone for switching, then voltage-withstanding capability is improved, but on-resistance increases and switching speed decreases
Solution Approach 1:
The patent combines a normally-on element and a normally-off element in series to create a hybrid switching circuit. The normally-on element provides high voltage-withstanding capability and low on-resistance, while the normally-off element contributes fast switching speed. The separate driver configuration with delay control enables both elements to work synergistically, achieving performance that neither element could provide alone.
Data Source
AI summary
A semiconductor device includes a first transistor and a second transistor connected in series between a first voltage source and a second voltage source. A diode is connected between a gate of the first transistor and the second voltage source. A capacitor is connected to the gate of the first transistor. A first driver is connected to the gate of the first transistor through the capacitor. A second driver is connected to a gate of the second transistor. A threshold voltage of the second transistor is higher than a threshold voltage of the first transistor.