Programmable Gate-Drive Switching Circuit for Safe Power-Off Transitions
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Solution Overview
Problem
Existing switching devices face challenges in safely transitioning between active and inactive modes, leading to potential damage from transient voltages and currents, especially when power supply is absent or degraded, due to uncontrolled high voltage transistors and inadequate voltage management.
Innovation Solution
A switching device comprising a high voltage depletion mode transistor and a low voltage enhancement mode transistor in series, with a control circuit and driver circuit that uses programmable voltage sources and programming modules to manage gate currents, ensuring controlled transitions between modes and preventing transistor damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the high voltage transistor is left uncontrolled during inactive mode, then the device can be deactivated without power supply, but transient voltages and currents can damage the transistors
Solution Approach 1:
The control circuit ensures that the high voltage transistor is switched off before the power supply is removed during deactivation. This preliminary action prevents transient voltage spikes and current surges that would otherwise damage the transistor when switching from active to inactive mode.
Solution Approach 2:
The control circuit monitors the state of the high voltage transistor and adjusts the switching sequence accordingly. By detecting whether the transistor is on or off, the control circuit can coordinate the shutdown sequence to prevent damage, ensuring the transistor is off before power removal occurs.
2Ease of operation
If the gate voltage of the high voltage transistor is floating during inactive mode, then the device can be fully deactivated, but the transistor may switch to on-state due to coupling effects
Solution Approach 1:
The control circuit applies a clamping voltage to the gate of the high voltage transistor during inactive mode to counteract any coupling effects that might cause unwanted switching. This preliminary anti-action prevents the transistor from inadvertently turning on when the gate voltage would otherwise be floating.
3Reliability
If separate control terminals are used for both transistors, then the switching state can be precisely controlled, but the device complexity increases
Solution Approach 1:
The control circuit is designed to perform multiple functions: it controls both the high voltage and low voltage transistors, manages power supply sequencing, and provides gate voltage clamping. This multi-functional approach maintains precise switching control while avoiding the need for entirely separate control circuits for each transistor.
4Speed
If the switching sequence is not controlled during mode transitions, then the device can switch modes quickly, but transient currents can exceed avalanche voltage and damage transistors
Solution Approach 1:
The control circuit prepares the transistor states before mode transitions occur. During activation, it ensures the high voltage transistor is switched on before full power is applied. During deactivation, it switches off the high voltage transistor before removing power supply. This preliminary preparation enables fast transitions without damaging transient currents.
Data Source
AI summary
A power circuit switching device includes two switching terminals; a high voltage depletion mode transistor and a low voltage enhancement mode transistor arranged in series between the two switching terminals; a control circuit having a first input for receiving a switching signal and a second input for receiving a signal for activating the device, the control circuit being configured to put the switching device into an inactive state or an active state; a driver circuit for applying the switching signal to the gate of the high voltage transistor, the driver circuit being supplied with a first voltage from a first voltage source (VDR+) and with a second voltage from a second voltage source (VDR−), the first and second voltages being respectively higher and lower than the threshold voltage of the high voltage transistor; and at least one programming module associated with the driver circuit, configured to program the incoming current which is to be injected at the gate of the high voltage transistor, and the outgoing current which is to be drawn from the gate; the programming module being able to be connected to a first and a second passive component for programming the incoming current and outgoing current, respectively.