P-type Back-to-Back MOS Switch Protection Circuit
Solution Overview
Problem
Existing gate driving circuits using n-type back-to-back MOS switches are vulnerable to high voltages during stress events like ESD, leading to potential damage and destruction of MOSFETs, and require expensive charge pump circuitry for signal amplification, while current protection mechanisms result in undesired current injection.
Innovation Solution
A protection circuit for a p-type back-to-back MOS switch gate driver that includes a gate source coupling switch and a driving signal insulation switch, which manage voltage differences between common gates and sources to prevent breakdown and minimize current injection, using a reference voltage to control conduction paths and disconnect the input from the supply voltage during high voltage events.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If n-type back-to-back MOS switches are used in gate driving circuits, then the circuit can provide gate drive functionality, but the MOSFETs are vulnerable to damage from high voltages during stress events like ESD
Solution Approach 1:
The patent introduces a protection circuit as an intermediary between the gate driving circuit and the external environment. This protection circuit includes voltage detection circuitry that monitors voltage levels and activation circuitry that responds to overvoltage conditions by controlling the back-to-back MOS switches, thereby mediating the harmful effects of ESD and overvoltage stress on the MOSFETs
Solution Approach 2:
The protection circuit performs preliminary detection of voltage levels through the voltage detection circuitry before harmful overvoltage damage can occur. The circuit is configured to detect overvoltage conditions and activate the protection mechanism in advance, preventing the high voltage from reaching damaging levels at the MOSFETs during stress events
2Reliability
If zener diodes and resistors are used to protect MOSFETs against high voltage differences, then the MOSFETs are protected, but undesired current injection occurs during high voltage events
Solution Approach 1:
The protection circuit employs feedback through voltage detection circuitry that continuously monitors the voltage at the output terminal. When overvoltage conditions are detected, the activation circuitry receives feedback signals and activates the protection mechanism by controlling the back-to-back MOS switches to clamp the voltage, thereby preventing current injection while maintaining protection
3Ease of operation
If charge pump circuitry is used to amplify input signals to higher voltage levels, then the n-type MOSFET gates can be driven, but the circuitry becomes large and expensive
Solution Approach 1:
Instead of using a charge pump to actively generate high voltages for gate driving, the patent inverts the approach by using back-to-back MOS switches configured to naturally provide the required voltage levels through their intrinsic properties and connection to the supply voltage. This eliminates the need for complex charge pump circuitry while maintaining the ability to drive gates at appropriate voltage levels
Data Source
AI summary
A protection circuit and a gate driving circuitry. The protection circuit is for protecting a p-type back-to-back MOS switch. The circuit receives an input driving signal and provides a driving output signal to common gates of the p-type back-to-back MOS switch. The circuit comprises a driving signal insulation switch for disconnecting the common gate of the p-type back-to-back MOS switch from the received input driving signal when the voltage of the common gates is larger than the supply voltage of the circuit. The circuit further comprises a gate source coupling switch for coupling a voltage received at the common source of the p-type back-to-back MOS switch to the common gate if a received voltage at the common sources is larger than a reference voltage Vref.