Startup Regulator Circuit With Charge-Pumped MOSFET Gate Bias
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Solution Overview
Problem
Conventional high-voltage startup regulators face limitations in power consumption, application input range, and cost due to constraints on the minimum resistance value for pull-up resistors and the use of dedicated high-voltage MOSFETs with gate leakage, which are costly and complex.
Innovation Solution
A circuit incorporating a charge pump and electronic switches to sustain gate leakage current, where a comparator activates the charge pump when the input voltage reaches a threshold, reducing the reliance on pull-up resistors and enabling cost-effective operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a pull-up resistor is used to bias the gate of the bypass transistor, then the transistor can be activated, but power consumption increases due to the constraint on minimum resistance value
Solution Approach 1:
The charge pump circuit is activated in advance to charge the gate capacitor before the bypass transistor needs to conduct. This preliminary charging action eliminates the need for continuous current through the pull-up resistor, thereby reducing power consumption while ensuring the transistor is properly activated when needed.
Solution Approach 2:
The gate capacitor serves itself by storing charge during the off-state and maintaining the gate voltage without requiring continuous external current supply. This self-sustaining mechanism reduces reliance on the pull-up resistor and minimizes steady-state power consumption.
2Loss of energy
If a dedicated high-voltage MOSFET with no gate leakage is used, then gate leakage current is eliminated, but cost and device complexity increase
Solution Approach 1:
The gate leakage current is extracted and redirected through the charge pump circuit rather than being lost through the bypass transistor gate. By separating the leakage path from the main current path and utilizing it to charge the gate capacitor, the system eliminates waste while maintaining simplicity.
Solution Approach 2:
The gate leakage current, which is normally a harmful loss, is converted into a beneficial charging current for the gate capacitor. The charge pump captures this leakage current and uses it to maintain the gate voltage, transforming an energy loss into a useful function.
3Use of energy by moving object
If the pull-up resistor resistance is reduced to lower power consumption, then power consumption decreases, but the minimum high-voltage input range is compromised
Solution Approach 1:
The charge pump performs preliminary charging of the gate capacitor to a sufficient voltage level before the bypass transistor needs to conduct. This advance preparation allows the use of lower resistance pull-up resistors without compromising the ability to activate the transistor across the full input voltage range.
Solution Approach 2:
The system changes the operating parameters by introducing a charge pump that actively manages gate voltage, replacing the passive resistor-based biasing. This parameter change enables the pull-up resistor to operate at lower resistance values while maintaining proper transistor activation through the active charge pumping mechanism.
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 reduces power consumption, expands the application input range, and provides a cost-effective alternative to dedicated high-voltage MOSFETs by minimizing gate leakage current through the charge pump, thus addressing the limitations of conventional regulators.
Implementation Method 1
A charge pump is coupled to the current flow-path of the first electronic switch and configured to be activated with the second electronic switch switched to the conductive state to pump electric charge from the current flow-path of the first electronic switch to the control node of the first electronic switch
Implementation Method 2
A comparator is coupled to the voltage-sensing node and a threshold. The comparator is configured to compare a voltage at the voltage-sensing node with the threshold and generate the switch-on signal in response to the voltage at the voltage-sensing node reaching the threshold
Implementation Method 3
a pull-up resistor used to bias the gate of the bypass transistor
Data Source
AI summary
A circuit includes an electronic switch configured to be coupled intermediate a high-voltage node and low-voltage circuitry and configured to couple the low-voltage circuitry to the high-voltage node. A voltage-sensing node is configured to be coupled to the high-voltage node via a pull-up resistor. A further electronic switch can be switched to a conductive state to couple the voltage-sensing node and the control node of the electronic switch. A comparator compares a threshold with a voltage at the voltage-sensing node and causes the further electronic switch to switch on in response to the voltage at said voltage-sensing node reaching said threshold. A charge pump coupled to the current flow-path of the electronic switch is activated to the conductive state to pump electric charge from the current flow-path of the electronic switch to the control node of the electronic switch via the further electronic switch switched to the conductive state.