Hybrid Switch Leakage Clamp Circuit for Cascode Voltage Safety
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Solution Overview
Problem
Conventional semiconductor switches in cascode configurations face issues with leakage current imbalances, which can lead to unsafe voltage levels at intermediate terminals, potentially damaging the switch, especially when the leakage current of the normally-on device exceeds that of the normally-off device.
Innovation Solution
A leakage clamp circuit is integrated across the normally-off device, clamping the voltage at the intermediate terminal to a threshold level, preventing excessive voltage and ensuring safe operation by controlling the voltage between the source and gate of the normally-on device, thereby preventing substrate current and snapback.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a cascode configuration with normally-on and normally-off devices is used, then switching efficiency and power conversion performance are improved, but leakage current imbalances cause unsafe voltage levels at intermediate terminals
Solution Approach 1:
A clamp circuit is introduced as an intermediary component between the normally-on and normally-off devices. This clamp circuit actively monitors and limits the voltage at the intermediate terminal, preventing voltage spikes caused by leakage current imbalances. The clamp circuit acts as a mediator that protects the system from the harmful effects of leakage current variations while maintaining the high-efficiency cascode configuration.
2Power
If the normally-on device operates at high voltage, then power handling capability is improved, but substrate current and snapback effects increase
Solution Approach 1:
The clamp circuit is designed to utilize the naturally occurring leakage currents in the high-voltage normally-on device rather than treating them purely as harmful effects. By providing a controlled path for these leakage currents through the clamp circuit, the system converts potentially damaging substrate current and snapback effects into manageable operational characteristics, allowing the device to maintain high power handling capability while preventing harmful current injection into the substrate.
Data Source
AI summary
A switch having a drain, a source, and a control. The switch comprising a depletion-mode transistor including a first, a second, and a control terminal and an enhancement-mode transistor including a first, a second, and a control terminal. The first terminal of the depletion-mode transistor is the drain of the switch and the control of the depletion-mode transistor is coupled to the source of the switch. The control of the enhancement-mode transistor is coupled to the control of the switch, the second terminal of the enhancement-mode transistor is the source of the switch. The switch comprises a clamp circuit to clamp a voltage of the first terminal of the enhancement-mode transistor to a threshold, the clamp circuit comprises a resistor and a pn-junction device coupled between the first and second terminals of the enhancement-mode transistor and between the second terminal and the control of the depletion-mode transistor.