Pull-Down Circuit Prevents MOSFET False Turn-On
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Solution Overview
Problem
Conventional output driver circuits in integrated circuit devices face high power consumption due to leakage currents caused by low resistance pull-down resistors, which are used to prevent false turn-on of power MOSFETs triggered by displacement currents from gate-drain parasitic capacitance.
Innovation Solution
The implementation of a pull-down circuit with a switching device, such as a depletion type n-channel MOSFET, and a charge pump control circuit that dynamically adjusts the gate voltage of the external MOSFET switch to prevent premature turn-on, using a negative charge pump to manage the gate-source voltage and reduce power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a pull-down resistor with low resistance value is used to prevent false turn-on of the power MOSFET, then the reliability is improved, but the power consumption increases due to leakage current
Solution Approach 1:
The patent applies the dynamics principle by replacing the static pull-down resistor with a dynamic switching circuit. The switching device (such as an n-channel MOSFET) is controlled to change its state based on the operating conditions of the power MOSFET. During the off-state of the power MOSFET, the switching device activates the pull-down function to prevent false turn-on. During the on-state, the switching device disables the pull-down path to eliminate leakage current. This dynamic adaptation resolves the contradiction by providing the pull-down function only when needed, rather than continuously.
Solution Approach 2:
The patent applies the parameter changes principle by changing the resistance value of the pull-down path dynamically. When the power MOSFET is off, the switching device connects a low resistance pull-down resistor to the gate to ensure strong pull-down capability and prevent false turn-on. When the power MOSFET is on, the switching device disconnects or increases the resistance of the pull-down path, thereby minimizing leakage current. This change in resistance parameter based on operational state resolves the contradiction between reliability and power consumption.
2Reliability
If a pull-down resistor is used to address false turn-on, then the reliability is improved, but the device complexity increases due to additional circuit components
Solution Approach 1:
The patent applies the universality principle by designing the switching device to perform multiple functions. The same switching device (such as an n-channel MOSFET) that is part of the power conversion circuit also serves as the control element for the pull-down circuit. The gate of the switching device is controlled by the same control signal that drives the power MOSFET, allowing it to simultaneously perform power switching and gate voltage control functions. This multi-functionality reduces the need for separate dedicated pull-down components, thereby reducing device complexity while maintaining reliability.
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
This solution effectively reduces power consumption by minimizing leakage currents and preventing false turn-ons of the MOSFET switch, while maintaining the MOSFET in a controlled state to avoid unnecessary power usage.
Implementation Method 1
a charge pump control circuit coupled to a gate of the switching device. The charge pump control circuit generates a control voltage in response to the switching signal to turn off the switching device
Data Source
AI summary
A pull-down circuit includes a control circuit generating an activation signal in response to a supply voltage, a first reference voltage, and a feedback signal, and a charge pump configured to generate a control signal in response to the activation signal and control a switching device using the control signal. The switching device is a field-effect transistor (FET) and is coupled to a power switch and pulls down a voltage level of a gate of the power switch to prevent a premature turn-on of the power switch.