NMOS Switch Control Circuit With Dynamic Leakage Turn-Off Path
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional switch circuits struggle to reliably turn off NMOS transistor switches in power-off states without impacting performance in power-on states, as they either fail to ensure switch off or incur performance burdens due to additional components like constant resistors.
Innovation Solution
A switch control circuit comprising an electronic component, a control circuit, and a resistive component that functions as a leakage path between the switch control node and the voltage terminal, allowing the switch to be turned off in power-off states without affecting the switch circuit's performance in power-on states by preventing voltage from exceeding a predetermined level.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a constant resistor is used as a leakage path to ensure the switch turns off in power-off state, then the reliability of switch off is improved, but the operating speed and performance of the switch circuit deteriorates
Solution Approach 1:
The patent replaces the static constant resistor with a dynamic leakage path formed by an electronic component (such as an NMOS transistor) whose resistance changes based on operating conditions. In power-off state, the electronic component provides sufficient leakage to ensure switch off reliability. In power-on state, the electronic component's resistance increases automatically, reducing the burden on operating speed and performance.
2Productivity
If no leakage path is provided in power-off state, then the performance burden is reduced, but the switch cannot be turned off reliably
Solution Approach 1:
The patent implements preliminary action by designing the electronic component and resistive component to automatically establish an appropriate leakage path before the switch needs to be turned off. The control circuit prepares the leakage path in advance during normal operation, and this pre-established path ensures reliable switch off when power is removed, without requiring additional performance burden during active operation.
3Reliability
If the control circuit maintains control over the control voltage node in power-off state, then the switch control is improved, but the circuit complexity increases
Solution Approach 1:
The patent extracts the power-off state control function from the main control circuit. The control circuit is designed to have no effective control over the control voltage node in power-off state, naturally relinquishing control when power is removed. This simplifies the control circuit design while maintaining reliability through the automatic operation of the electronic component and the established leakage path.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Ensures the switch is reliably turned off in power-off states without compromising the switch circuit's performance in power-on states, potentially even improving it by using a depletion mode NMOS transistor or diode to manage voltage and current effectively.
Implementation Method 1
the predetermined voltage is equal to the sum of the voltage drop caused by the electronic component between the switch control node and the control voltage node and the voltage of the voltage terminal in the power-off state
Implementation Method 2
The resistive component is coupled between the control voltage node and the voltage terminal. The electronic component and the resistive component function as at least a part of a leakage path between the switch control node and the voltage terminal
Data Source
AI summary
Disclosed is a switch control circuit coupled between a switch control node and a voltage terminal. The switch control node is between an input circuit and a switch. The switch control circuit includes: an electronic component being turned on or off according to voltages of the switch control node and a control voltage node in a power-on state and preventing the voltage of the switch control node from being higher than a predetermined voltage in a power-off state; a control circuit outputting a control signal to the control voltage node in the power-on state and having no effective control over the voltage of the control voltage node in the power-off state; and a resistive component coupled between the control voltage node and voltage terminal. The electronic and resistive components function as at least a part of a leakage path to assist in turning off the switch in the power-off state.