Semiconductor Switch Bias Switching for Overvoltage Protection
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Solution Overview
Problem
Conventional semiconductor switches face damage and malfunction due to overvoltage issues when the breakdown voltage is not high enough, leading to excessive drain-to-gate voltage drops during AC signal cycles, which can exceed the transistor's breakdown voltage.
Innovation Solution
A semiconductor switch design incorporating a transistor with a drain, gate, and source, along with bias resistors and selecting circuits that adjust bias voltages based on the transistor's state, ensuring voltage drops within specific ranges to prevent overvoltage damage, including a drain bias resistor coupled with different biases when the transistor is on or off, and a gate and source bias resistor with distinct biases for each state.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the transistor gate is grounded and drain is coupled to DC operating voltage through bias resistor, then the transistor can operate as a simple switch, but the drain-to-gate voltage drop may exceed the breakdown voltage when AC signal peak exceeds DC operating voltage
Solution Approach 1:
The patent applies dynamics by making the bias voltages changeable based on transistor state. The drain bias voltage switches between first drain bias (when transistor is on) and second drain bias (when transistor is off). The gate bias voltage similarly switches between first gate bias and second gate bias. This dynamic adjustment ensures that during off-state, the voltage difference between drain and gate remains within breakdown voltage limits even when AC signal peaks exceed the DC operating voltage, thus preventing overvoltage damage while maintaining simple switching operation.
Solution Approach 2:
The patent changes the voltage parameters dynamically based on transistor state. When the transistor is turned off, the drain bias voltage is changed to a second drain bias and gate bias voltage is changed to a second gate bias, ensuring the voltage drop remains below breakdown voltage. This parameter change approach allows the circuit to adapt to different operating conditions and protect the transistor from overvoltage stress.
2Adaptability or versatility
If the breakdown voltage is not high enough (twice or less of DC operating voltage), then the transistor cannot handle AC signals with peak values equal to or exceeding DC operating voltage, but increasing breakdown voltage may not be feasible due to device limitations
Solution Approach 1:
Instead of relying on a high breakdown voltage transistor, the patent uses dynamic bias voltage adjustment. By switching between different drain and gate bias voltages based on transistor state, the circuit ensures that the voltage difference across the transistor never exceeds the breakdown voltage, even when handling AC signals with peak values equal to or exceeding the DC operating voltage. This makes the system adaptable to various signal conditions without requiring a transistor with excessively high breakdown voltage.
Solution Approach 2:
The patent introduces bias selecting circuits as intermediary components that mediate between the AC signal and the transistor. These selecting circuits adjust the drain and gate bias voltages to ensure safe operating conditions, acting as a protective layer that prevents direct exposure of the transistor to dangerous voltage differences.
3Reliability
If bias selecting circuits are added to dynamically adjust drain and gate biases, then overvoltage protection is achieved, but the device complexity increases
Solution Approach 1:
The patent implements dynamic bias adjustment through bias selecting circuits that switch between different bias voltages based on transistor state. While this adds circuit elements, the dynamic nature of the solution allows for efficient protection without requiring continuously variable controls or complex feedback mechanisms.
Solution Approach 2:
The bias selecting circuits can be controlled by the transistor's own state (on/off condition), making the protection mechanism self-regulating. When the transistor turns off, the selecting circuits automatically switch to the appropriate bias voltages to prevent overvoltage, without requiring external monitoring or complex control logic.
Data Source
AI summary
The present invention discloses a semiconductor switch comprising a switching unit. Said switching unit includes: a transistor having a drain, a gate and a source; a drain bias resistor coupled to the drain; a drain bias selecting circuit to couple the drain bias resistor with a first or a second drain bias according to the transistor's state; a gate bias resistor coupled to the gate; a gate bias selecting circuit to couple the gate bias resistor with a first or a second gate bias according to the transistor's state; a source bias resistor coupled to the source; and a source bias selecting circuit to couple the source bias resistor with a first or a second source bias according to the transistor's state, wherein the first and second drain biases are different, the first and second gate biases are different, and the first and second source biases are different.