Load Switch Gate Slope Control for Zero Quiescent Current
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Solution Overview
Problem
Existing power management systems face challenges in minimizing quiescent current in load switches, which leads to increased power consumption and reduced battery life, especially when these switches are in an inactive state.
Innovation Solution
A low quiescent current load switch circuit is developed using a resistive driver with external capacitor-based constant gate slope control, which reduces the quiescent current to zero by shutting off the gate slope control circuitry once the gate is fully activated, thereby minimizing power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If gate slope control circuitry is kept active to maintain load switch operation, then the load switch can respond quickly to enable signals, but quiescent current increases during inactive states
Solution Approach 1:
The gate slope control circuitry is activated periodically only when needed - specifically when an enable signal transitions from low to high state. The circuit operates during the transition phase to charge the gate capacitor, then enters a low-power state during steady operation. This periodic activation eliminates continuous current consumption while maintaining fast response capability when the load switch needs to be enabled.
2Use of energy by moving object
If gate slope control circuitry is shut off to reduce quiescent current, then power consumption decreases, but the load switch may not activate quickly enough
Solution Approach 1:
The gate slope control circuitry is designed to activate in advance of the actual switching requirement. When the enable signal transitions high, the circuit immediately begins charging the gate capacitor through the controlled slope mechanism. This preliminary action ensures the gate reaches full voltage quickly at the moment switching is needed, while the circuitry remains dormant (consuming minimal power) during extended inactive periods between switching events.
3Reliability
If continuous monitoring and control circuits are maintained active, then load switch operation remains stable and responsive, but battery life is reduced due to increased power consumption
Solution Approach 1:
The patent extracts and removes the gate slope control circuitry from the continuous active state, isolating it to operate only during specific transition events. By taking out this power-consuming control mechanism from the always-on configuration and placing it in an event-driven architecture, the circuit maintains operational stability when needed while consuming negligible power during normal operation, thereby extending battery life without sacrificing reliability.
Data Source
Figure 1A
Figure 1B~2A
Figure 2B~3B
AI summary
A load switch circuit (100) includes a driver (112) to control a gate (114) of a transistor. The gate (114) enables the transistor to deliver power to a load from a power supply (130) when the gate (114) is activated. A gate slope control (116) controls a rate of change over time of a voltage associated with the gate (114) to activate the gate (114) and to disable the driver (112) when the gate (114) is activated.