Low Power Regulator Using Constant-Gm Bias for Voltage Stability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing voltage regulators require large die size and consume substantial area due to high quiescent current, and struggle to deliver current efficiently when transitioning from deep sleep mode to normal operation, while also experiencing variations in output voltage due to temperature and supply changes.
Innovation Solution
A voltage regulator design utilizing a constant-gm bias circuit with NMOS devices and a diode-connected transistor, combined with a bipolar junction transistor, to generate and mirror bias current, ensuring the gate-source voltage remains constant and delivering current efficiently across temperature and supply variations, thereby reducing quiescent current and output voltage stability issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a large resistor divider network is used to reduce quiescent current, then quiescent current consumption is reduced, but die area increases substantially
Solution Approach 1:
The patent changes the operating parameters of the transistor by biasing it in the subthreshold region instead of the saturation region. This parameter change allows the transistor to function as a high-impedance current source with much lower current consumption, eliminating the need for large resistor values and thereby reducing die area while maintaining low quiescent current.
Solution Approach 2:
The patent substitutes the traditional resistor-based current limiting mechanism with an active transistor-based current source. This substitution uses the transistor's inherent electrical characteristics (subthreshold conduction) to achieve the same current control function with significantly reduced area and improved performance.
2Use of energy by moving object
If the voltage regulator is designed for low quiescent current, then power consumption during sleep mode is reduced, but the ability to deliver current quickly when exiting sleep mode is compromised
Solution Approach 1:
The patent creates a dynamic system where the transistor operates in different regions based on the operational state. During sleep mode, the transistor operates in the subthreshold region for minimal current consumption. When exiting sleep mode, the transistor can transition to the saturation region to quickly deliver the required current, providing dynamic adaptability to different operational requirements.
Solution Approach 2:
The circuit is designed with preliminary action by maintaining the transistor in a biased state that allows rapid transition from sleep to active mode. The subthreshold-biased transistor is pre-configured to can quickly source current when needed, eliminating the delay that would occur if the regulator had to fully power up from a completely off state.
3Reliability
If traditional voltage regulator circuits are used, then voltage regulation is achieved, but output voltage varies significantly with temperature and supply voltage changes
Solution Approach 1:
The patent implements a feedback mechanism where the gate of the subthreshold-biased transistor is connected to the output node. This creates a self-regulating system that responds to output voltage changes by adjusting the transistor's conduction, thereby stabilizing the output voltage against variations in temperature and supply voltage.
Solution Approach 2:
The circuit performs self-service by using the output voltage itself to control the biasing of the transistor. The transistor automatically adjusts its operating point based on the output conditions, providing inherent compensation for temperature and supply variations without requiring external control circuits.
Data Source
AI summary
A voltage regulator may derive current from a bias circuitry having a constant-transconductance. The bias circuitry may generate the bias current using three NMOS devices. The temperature coefficient of the bias current may be within a specified, desired range. The bias current may be mirrored to low-power regulator circuitry to bias a diode-connected transistor in the low-power regulator circuitry to operate in the strong inversion region. A ratioed current based on the output load current may be injected into a bipolar junction transistor (BJT) device to cause the gate-source voltage (VGS) of the diode-connected device to track the VGS of the output transistor of the voltage regulator, to ensure tighter load regulation. By operating the diode-connected transistor in strong inversion, by maintaining its (VGS) constant over temperature, and by cancelling the VGS of the output transistor of the voltage regulator with the base-emitter voltage (VBE) of the BJT device, the regulated voltage output may become free of the effects of temperature and supply voltage.