Load Switch True Reverse Current Blocking MOSFET
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Solution Overview
Problem
Load switches often lack protection against reverse current flow from the load back to the power supply, which can damage components, especially when the switch is in an off or open state, and they have limited current capability and high on-state resistance.
Innovation Solution
A load switch with true reverse current blocking (TRCB) capability, increased current capability, and reduced on-state resistance, utilizing a MOSFET switch with a TCRB circuit that blocks current flow from the output to the input regardless of the switch's state, and includes features like hysteresis logic to prevent false triggers and electrostatic discharge protection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional load switch is used, then the switch can connect and disconnect the load from power supply, but it provides no protection against reverse current flow from load to power supply
Solution Approach 1:
The patent combines the reverse current blocking function with the main power switch by using the body diode of an N-channel MOSFET. The source terminal is connected to the load and drain to the power supply, creating an inherent reverse current block due to the MOSFET's body diode orientation, thus merging protection functionality into the switching element itself.
Solution Approach 2:
The patent introduces a P-channel MOSFET as an intermediary element working in conjunction with the N-channel MOSFET. The P-channel MOSFET's body diode blocks reverse current while allowing forward current flow when both MOSFETs are properly controlled, using the intermediary device to achieve the blocking function.
2Reliability
If the switch is in off state, then power is disconnected from load, but reverse current can still flow from load to power supply
Solution Approach 1:
The N-channel MOSFET's body diode is oriented to block reverse current flow from load to power supply in the off state, combining the switching and protection functions. This eliminates the need for separate protection components that would increase quiescent current drain.
3Power
If conventional switches are used, then basic switching is achieved, but current capability is limited and on-state resistance is high
Solution Approach 1:
The patent merges a P-channel MOSFET and N-channel MOSFET in a complementary configuration where each device compensates for the other's limitations. This combination achieves low on-state resistance and high current capability while maintaining reliable reverse current blocking through the body diodes of both devices.
Data Source
AI summary
Devices, systems and methods are provided for switching a load with true reverse current blocking (TRCB). The device may include an input port coupled to a supply voltage; an output port coupled to the load; a TRCB circuit coupled to the input port and the output port; and a switch control port coupled to the TRCB circuit. The TRCB circuit may be configured to couple the input port to the output port in response to a switch close signal applied to the switch control port and to de-couple the input port from the output port in response to a switch open signal applied to the switch control port. The TRCB circuit may further be configured to block current flow from the output port to the input port in response to both the switch open signal and the switch close signal.