Thin-Gate High-Voltage Switch for Fast Transient Response
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Solution Overview
Problem
In applications such as cellular network base stations, existing transistor switch designs fail to quickly turn on circuitry, with existing designs often taking longer than 500 nanoseconds to reach 99% of the final supply voltage, which is a significant drawback for rapid power-on requirements.
Innovation Solution
A circuit design incorporating a thin gate switch, NMOS and PMOS gate drivers, and a pulse generator to rapidly turn on transistors by using larger transistors for initial current charging and smaller transistors for maintaining the on-state, with diode-connected transistors to prevent voltage damage, allowing for quick and controlled switching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional transistor switch designs are used, then device simplicity is maintained, but switching speed is insufficient (taking longer than 500 nanoseconds to reach 99% of final supply voltage)
Solution Approach 1:
The transistor switch is divided into multiple segments: a first transistor for high-voltage switching and a second transistor for gate drive control. This segmentation allows each transistor to be optimized for its specific function, enabling faster switching speeds while managing complexity through functional division.
Solution Approach 2:
A gate driver circuit is introduced as an intermediary between the control signal and the transistor gate. The gate driver includes a first transistor that can source or sink current to rapidly charge or discharge the gate capacitance, enabling fast switching without requiring the main switching transistor to directly handle the gate drive current.
2Speed
If larger transistors are used for initial current charging to achieve fast switching, then switching speed improves, but steady-state power consumption increases
Solution Approach 1:
The circuit dynamically switches between different transistor configurations during the switching process. During the transient charging phase, larger transistors provide high current for fast switching. Once switching is complete, the circuit transitions to a steady-state configuration where smaller transistors maintain the on-state with minimal power consumption.
Solution Approach 2:
The gate driver circuit performs preliminary action by pre-charging the gate capacitance before the main switching transistor is fully activated. This preliminary charging action reduces the time the main transistor needs to conduct high current, thereby reducing steady-state power consumption while maintaining fast switching speed.
3Use of energy by stationary object
If thin gate transistors are used to reduce power consumption, then steady-state power consumption decreases, but vulnerability to voltage damage increases
Solution Approach 1:
A gate driver circuit is introduced as an intermediary between the control signal and the thin-gate transistor. The gate driver includes protection circuitry that limits the voltage applied to the thin gate, preventing damage while still enabling sufficient current flow for fast switching. This intermediary structure allows the thin-gate transistor to operate at low power without exposing it to harmful high voltages.
Solution Approach 2:
The circuit changes the voltage parameter applied to the thin-gate transistor dynamically. During normal operation, the gate voltage is limited to safe levels that prevent damage. During switching transitions, controlled voltage spikes are applied only for the brief duration needed to charge the gate capacitance, after which the voltage returns to safe operating levels.
Data Source
AI summary
A circuit includes a first transistor having a first control input and first and second current terminals, and a second transistor having a second control input and third and fourth current terminals. A third transistor has a third control input and fifth and sixth current terminals, the fifth current terminal coupled to the first current terminal at a first supply voltage node. A fourth transistor has a fourth control input and seventh and eighth current terminals, the seventh current terminal coupled to the second and sixth current terminals. A pulse generator has a pulse generator input and a first pulse generator output, the pulse generator input configured to receive a switch control signal, and the first pulse generator output coupled to the first control input. The third control input is configured to receive either the switch control signal or a logical inverse of the switch control signal.