Quasi Floating Gate Voltage Regulator for Low Power LDO
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Solution Overview
Problem
Linear LDO voltage regulators using NMOS transistors require a charge pump to generate enough gate-to-source voltage, leading to high power consumption and undesirable electromagnetic interference (EMI) due to constant operation of the charge pump.
Innovation Solution
A voltage regulator with a quasi floating gate NMOS transistor, where the gate is capacitively coupled to an error amplifier and periodically charged by a charge pump, allowing the error amplifier to be powered by a lower voltage source and reducing power consumption and EMI by alternating between floating and quasi floating gate modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a charge pump is constantly operated to generate gate-to-source voltage for NMOS pass element, then sufficient voltage for NMOS operation is maintained, but power consumption increases and electromagnetic interference is generated
Solution Approach 1:
The charge pump operates periodically rather than continuously, being activated only when the input voltage approaches the output voltage (dropout condition). The control circuit monitors the voltage difference and enables the charge pump only when needed to maintain sufficient gate-to-source voltage on the NMOS pass element, thereby reducing overall power consumption while maintaining regulation stability.
Solution Approach 2:
The system dynamically adjusts the charge pump operation based on real-time voltage conditions. The control circuit continuously monitors the voltage difference between input and output, and adaptively enables or disables the charge pump accordingly, optimizing the balance between maintaining reliable voltage regulation and minimizing power consumption.
2Reliability
If a charge pump is constantly operated to generate gate-to-source voltage for NMOS pass element, then sufficient voltage for NMOS operation is maintained, but electromagnetic interference is generated
Solution Approach 1:
The charge pump operates periodically rather than continuously, being activated only when the input voltage approaches the output voltage (dropout condition). This periodic operation significantly reduces the duration of electromagnetic interference generation while maintaining voltage regulation stability only when necessary.
Solution Approach 2:
The harmful electromagnetic interference is extracted or isolated by confining charge pump operation to specific dropout conditions only. The control circuit separates the charge pump operation from continuous operation, extracting only the necessary portions when voltage regulation is at risk, thereby minimizing EMI while preserving reliability.
3Area of stationary object
If NMOS transistor is used as pass element, then device size is reduced due to higher conductivity, but additional voltage generation circuitry (charge pump) is required
Solution Approach 1:
The charge pump is activated periodically only during dropout conditions rather than continuously, reducing its operational complexity. The control circuit manages the charge pump in a simple on/off manner based on voltage thresholds, minimizing the control logic required while still enabling NMOS operation when needed.
Solution Approach 2:
The control circuit automatically detects dropout conditions and activates the charge pump without external intervention. The system self-regulates by monitoring its own voltage state and enabling the charge pump only when the NMOS pass element requires additional gate-to-source voltage, reducing the need for complex external control mechanisms.
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
Significantly reduces power consumption and EMI while maintaining stable output voltage, allowing the error amplifier to be powered by a lower voltage source and ensuring high gate-to-source voltage for the NMOS pass element, even in dropout conditions.
Implementation Method 1
a capacitor that is connected between the error amplifier and a gate of the N-channel transistor
Implementation Method 2
a charge pump that is switchably connected to the gate of the N-channel transistor
Data Source
AI summary
Various apparatuses, methods and systems for a voltage regulator are disclosed herein. For example, some embodiments provide an apparatus for regulating a voltage including an N-channel transistor that is connected between an input and an output, an error amplifier that is connected to the output, a capacitor that is connected between the error amplifier and a gate of the N-channel transistor, and a comparator that is connected to a node between the error amplifier and the capacitor. The apparatus also includes a charge pump that is switchably connected to the gate of the N-channel transistor. The apparatus is adapted to connect the charge pump to the gate of the N-channel transistor when a voltage at the node between the error amplifier and the capacitor rises above a threshold voltage.