Current Mirror Clamp Circuit for Low Leakage

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Solution Overview

Problem

Diode-based clamp circuits exhibit high leakage current when the voltage on a conductive line is below the clamp voltage, which degrades the accuracy of current measurements by affecting the reference voltage's ability to track temperature variations in sense resistors, impacting the accuracy of current measurements in ADCs.

Innovation Solution

A clamp circuit utilizing a first and second current mirror configured in a feedback loop, where the first current mirror mirrors current through its branches and the second current mirror mirrors current through its branches, with the branches of both current mirrors coupled in series, allowing for low leakage current when the voltage is below the clamp voltage and clamping the voltage to the desired level when it reaches the clamp voltage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a diode-based clamp circuit is used, then the voltage can be clamped to a desired level, but the leakage current is high which degrades measurement accuracy

Engineering Contradiction:

Improvevoltage clamping capabilityVSAvoidcurrent measurement accuracy

Core Design Contradiction:

ReliabilityVSMeasurement precision

Solution Approach 1:

The patent introduces current mirrors as intermediary components between the clamp voltage source and the conductive line. The current mirrors (first and second current mirrors with coupled branches) act as mediators that provide precise current control while maintaining low leakage, thereby resolving the contradiction between reliable voltage clamping and accurate current measurement.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent implements a feedback mechanism where the current mirrors continuously monitor and adjust the current flow based on the voltage level on the conductive line. This feedback control enables the circuit to maintain low leakage current during normal operation while automatically activating clamping action when voltage exceeds the desired level, thus preserving both measurement accuracy and clamping reliability.

Inventive Principle:

Principle #23Feedback

2Reliability

If a diode-based clamp circuit is used, then voltage protection is provided, but leakage current affects the reference voltage's ability to track temperature variations

Engineering Contradiction:

Improvevoltage protectionVSAvoidtemperature tracking accuracy

Core Design Contradiction:

ReliabilityVSTemperature

Solution Approach 1:

The current mirrors serve as intermediary elements that isolate the reference voltage circuit from the clamp circuit's leakage effects. By using current mirrors with coupled branches, the patent creates an intermediate control stage that preserves the reference voltage's temperature tracking capability while still providing robust voltage protection through the clamping mechanism.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Reliability

If a clamp circuit is added to protect against voltage exceeds, then circuit reliability is improved, but device complexity increases

Engineering Contradiction:

Improvecircuit protectionVSAvoidclamp circuit structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent achieves multi-functionality by designing the clamp circuit using current mirrors that simultaneously provide voltage clamping, low leakage current control, and temperature compensation. The first and second current mirrors with their coupled branches serve multiple purposes: protecting against overvoltage, maintaining measurement accuracy, and tracking temperature variations, thereby reducing the need for separate dedicated circuits for each function.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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

The proposed clamp circuit achieves a significantly lower leakage current compared to diode-based clamp circuits, ensuring accurate tracking of temperature variations in sense resistors and maintaining the accuracy of current measurements by the ADC, with a sharp transition from non-clamped to clamped current.

Implementation Method 1

a first current mirror having a first branch and a second branch, wherein the first current mirror is configured to mirror a current flowing through the first branch of the first current mirror to the second branch of the first current mirror

Methodology Applied

Scientific EffectCurrent mirror effect:

Implementation Method 2

a second current mirror having a first branch and a second branch, wherein the second current mirror is configured to mirror a current flowing through the first branch of the second current mirror to the second branch of the second current mirror

Methodology Applied

Scientific EffectCurrent mirror effect:

Data Source

PatentUS11307604B2Clamp circuit

Publication Date: 2022.04.19 QUALCOMM INC

AI summary

In certain aspects, a clamp circuit includes a first current mirror having a first branch and a second branch, wherein the first current mirror is configured to mirror a current flowing through the first branch of the first current mirror to the second branch of the first current mirror. The clamp circuit also includes a second current mirror having a first branch and a second branch, wherein the second current mirror is configured to mirror a current flowing through the first branch of the second current mirror to the second branch of the second current mirror. The first branch of the first current mirror is coupled in series with the second branch of the second current mirror, and the second branch of the first current mirror is coupled in series with the first branch of the second current mirror.