Constant Voltage Circuit With Dynamic Op-Amp Bias for Load Transients

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Solution Overview

Problem

Conventional constant voltage circuits face issues with unstable output and increased current consumption due to amplification of minute high-frequency signals, and require larger resistance elements to improve transient response, leading to operational instability and increased chip area.

Innovation Solution

A constant voltage circuit incorporating an operational amplifier with a constant current source, voltage detector, amplifier, judgment, and controller to selectively amplify and control AC components of the output voltage, thereby managing current consumption and improving transient response characteristics without increasing resistance elements.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If the current consumption of the operational amplifier is reduced, then power efficiency is improved, but the operating frequency becomes low and response performance to load transient fluctuation deteriorates

Engineering Contradiction:

Improvecurrent consumptionVSAvoidresponse performance

Core Design Contradiction:

Use of energy by moving objectVSSpeed

Solution Approach 1:

The operational amplifier's current consumption is made dynamic rather than static. The constant current source is controlled to increase current consumption temporarily during load transient fluctuations (detected via differentiation circuit) and return to low current consumption during steady state, thus achieving both power efficiency and fast response when needed

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The circuit uses feedback through the differentiation circuit that monitors output voltage changes and feeds back control signals to the operational amplifier. When load transient fluctuations are detected, the feedback mechanism triggers increased current consumption to improve response, creating a closed-loop control system that adapts to loading conditions

Inventive Principle:

Principle #23Feedback

2Productivity

If an amplification stage is added to improve response performance, then transient response characteristics are improved, but minute high-frequency signals are amplified causing unstable output and increased current consumption

Engineering Contradiction:

Improvetransient response characteristicsVSAvoidoutput stability

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The amplification function is applied locally and selectively only to specific frequency components (low-frequency transient signals) through the differentiation circuit, while high-frequency components are excluded from amplification. This localized application of amplification improves transient response without causing instability from high-frequency noise amplification

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The circuit changes the operating parameters of the operational amplifier dynamically based on the detected signal characteristics. The current consumption parameter is increased temporarily during transient events and returned to normal during steady state, allowing high response performance only when actually needed rather than maintaining it continuously

Inventive Principle:

Principle #35Parameter changes

3Speed

If the resistance component of the differentiation circuit is increased to widen the operating frequency band, then transient response performance is improved, but the resistance element area becomes larger increasing chip area

Engineering Contradiction:

Improvetransient response performanceVSAvoidresistance element area

Core Design Contradiction:

SpeedVSArea of stationary object

Solution Approach 1:

Instead of using large resistance values to widen the frequency band, the circuit changes the operational amplifier's current consumption parameter dynamically. This allows the use of smaller resistance components while achieving the same transient response performance through increased drive current during transient events

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The differentiation circuit's effective resistance is made dynamic through the controlled current consumption of the operational amplifier. During transient events, the increased current effectively compensates for smaller resistance values, allowing the use of smaller on-chip resistors while maintaining the desired frequency response characteristics

Inventive Principle:

Principle #15Dynamics

Data Source

PatentUS11835977B2Constant voltage circuit for improvement of load transient response with stable operation in high frequency, and electronic device therewith

Publication Date: 2023.12.05 NISSHINBO MICRO DEVICES INC

AI summary

A constant voltage circuit amplifies an error between a reference voltage and an output voltage by an operational amplifier, and controls a load current based on the amplified voltage so that the output voltage becomes a constant voltage. The constant voltage circuit includes voltage detector means that detects only AC components of the output voltage limited to a predetermined band and outputs a detected voltage; voltage amplifier means that amplifies AC components of the detected voltage and outputs an amplified voltage; judgment means that outputs a judgment signal indicating whether or not the amplified voltage equal to or larger than a predetermined threshold; and controller means configured to increase a current value of the constant current source included in the operational amplifier, based on the judgment signal, thereby temporarily increasing a current consumption of the operational amplifier.