Ultra-low Power CMOS Reference Voltage Driver Circuit
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Solution Overview
Problem
Conventional CMOS analog circuits for driving reference voltage consume high power due to continuous DC current consumption, especially in battery-operated or energy harvesting applications, where power efficiency is critical and low output impedance is required, and existing solutions like class A, B, and BJT-based amplifiers with dead zones consume significant power and are affected by process variations and supply voltage.
Innovation Solution
The implementation of an ultra-low power CMOS driver circuit with a 'dead zone' of output voltage levels that minimizes power consumption by using asymmetric comparators operating in the sub-threshold range, independent of supply voltage and process parameters, and constrains output current to avoid high current during power-up or interference, utilizing CMOS transistors and embedded offsets to manage voltage levels effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If class A amplifier is used to drive reference voltage, then output impedance is reduced, but power consumption increases due to continuous DC current
Solution Approach 1:
The amplifier is divided into two separate push-pull stages: a first push-pull amplifier stage and a second push-pull amplifier stage. This segmentation allows each stage to operate independently with optimized biasing, enabling the circuit to achieve low output impedance only when needed while minimizing continuous power consumption through the dead zone operation mode.
Solution Approach 2:
The circuit operates in a dead zone mode where both stages are turned off during steady-state conditions, and only activates periodically when voltage compensation is needed. This periodic action eliminates continuous DC current consumption while maintaining the ability to provide low output impedance when required.
2Use of energy by moving object
If class B amplifier is used to reduce power consumption, then power efficiency improves, but dead zone appears when biasing conditions shift
Solution Approach 1:
The circuit maintains continuous monitoring of the output voltage through feedback, ensuring that the dead zone is dynamically adjusted to prevent tracking errors. The feedback mechanism continuously detects when the output deviates from the input reference voltage and activates the appropriate stage to correct the error, eliminating the reliability issues associated with fixed dead zones.
Solution Approach 2:
The biasing conditions of the push-pull stages are dynamically adjusted based on the operating state. The circuit transitions between different biasing modes (fully off in dead zone, partially on during correction) to optimize both power consumption and tracking accuracy under different conditions.
3Stability of the object's composition
If amplifier is used to provide low output impedance, then voltage driving capability improves, but DC current consumption increases
Solution Approach 1:
The output impedance is made dynamic rather than static. During steady-state operation in the dead zone, both push-pull stages are turned off, resulting in high output impedance and zero DC current consumption. When voltage compensation is needed, the stages are activated to provide low output impedance for effective voltage driving, accepting temporary energy loss only when necessary.
Data Source
AI summary
A method and apparatus for implementing a CMOS buffer for driving a reference voltage that consumes very low current in normal operating conditions but drive high current when output voltage is off, tracking the required reference voltage. The circuit is operating in a “deadzone” most of the time, where pull-up and pull-down current paths are blocked, and ultra-low power comparators, with build-in offset, are monitoring the output voltage continuously, and driving compensation current, when needed. The circuit can be manufactured with a standard CMOS processing technology.