Power Switching Circuit With Protected HV Transistor Gate Control
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Solution Overview
Problem
Existing dual-control power circuit switching devices face challenges in safely transitioning between inactive and active modes, particularly due to uncontrolled high voltage applied to high voltage transistors, which can lead to damage during startup or degraded operations, and transient voltage/current issues during mode changes.
Innovation Solution
A switching device with a high voltage transistor in depletion mode and a low voltage transistor in enhancement mode, controlled by a circuit with separate switching and activation signals, utilizing a driver circuit with programmable voltage sources and programming modules to manage gate currents, and a protection circuit to maintain the high voltage transistor in a blocking state during inactive mode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the switching device is in inactive mode with the drive circuit unpowered, then energy consumption is reduced, but the gate voltage of the high voltage transistor becomes floating and uncontrolled, risking transistor damage
Solution Approach 1:
The protection circuit is pre-configured with a pull-down resistor connected to the gate of the high voltage transistor. Before the drive circuit is powered down, the protection circuit ensures the gate voltage is already pulled to a safe level. This preliminary action prevents the gate voltage from becoming floating when power is removed, thus protecting the transistor while enabling energy-saving inactive mode.
Solution Approach 2:
The protection circuit acts as an intermediary between the drive circuit and the high voltage transistor. When the drive circuit is unpowered, the protection circuit mediates by providing a defined voltage path through the pull-down resistor, preventing direct exposure of the transistor gate to floating voltage conditions. This intermediary ensures reliable transistor protection during energy-saving operations.
2Adaptability or versatility
If overvoltage is applied to the drain of the high voltage transistor during inactive mode, then the transistor can be turned on by coupling effect, but this maintains the transistor in an uncontrolled state leading to potential damage
Solution Approach 1:
The protection circuit applies a preliminary counteracting action by pulling the gate voltage to a defined low level through the pull-down resistor. This prevents the coupling effect from inadvertently turning on the transistor when overvoltage appears on the drain during inactive mode. The gate is pre-biased to ensure it remains firmly in the off state, counteracting any parasitic coupling effects.
3Ease of operation
If transient voltages or currents appear during mode transitions, then switching between active and inactive modes is possible, but these transients can damage the transistors if not perfectly controlled
Solution Approach 1:
The protection circuit provides beforehand cushioning by having the pull-down resistor permanently connected to the gate of the high voltage transistor. During mode transitions, this resistor acts as a cushion that prevents transient voltages from pushing the gate into dangerous regions. The resistor is already in place before transients occur, providing continuous protection against voltage spikes and current surges during switching operations.
Data Source
Figure 1~2
Figure 3~4a
Figure 4b~4c
AI summary
The invention relates to a power circuit switching device (1) comprising: two switching terminals (2a, 2b); a high voltage depletion mode transistor (5) and a low voltage enhancement mode transistor (6) arranged in series between the two switching terminals (2a, 2b); a control circuit (8) having a first input (9) for receiving a switching signal and a second input (10) for receiving a signal for activating the device (1), the control circuit (8) being configured to put the switching device (1) into an inactive state or an active state; a driver circuit (4) for applying the switching signal to the gate of the high voltage transistor (5), the driver circuit (4) 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 (5); and at least one programming module associated with the driver circuit (4), configured to program the incoming current which is to be injected at the gate of the high voltage transistor (5), and the outgoing current which is to be drawn from said 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.