Integrated Circuit Reverse Current Protection and Disconnection Detection

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Solution Overview

Problem

Load switches in integrated circuits face challenges in accurately detecting power source disconnection and providing reverse current protection due to low ON resistance, leading to inaccurate current sensing and potential battery damage.

Innovation Solution

The integration of a switch transistor, gate driver circuit, current sensor circuit, voltage drop regulation circuit, and charge-release circuit, which includes a transconductance amplifier to increase voltage across the switch transistor and improve current sense accuracy, and a charge-release circuit to disconnect the power source when necessary, preventing reverse current flow.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If the load switch is active with low ON resistance to enable efficient power transmission, then power transmission efficiency is improved, but reverse current flows from the battery to the load switch causing thermal power dissipation that may exceed the transistor's thermal rating

Engineering Contradiction:

Improvepower transmission efficiencyVSAvoidreverse current damage

Core Design Contradiction:

Use of energy by moving objectVSObject-affected harmful factors

Solution Approach 1:

The patent applies preliminary action by detecting the disconnection status of the power source before reverse current can cause damage. The detection circuit monitors whether the power source is connected, and the control circuit proactively turns off the load switch when disconnection is detected, preventing reverse current flow before it can exceed the transistor's thermal rating.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent implements feedback through a detection circuit that continuously monitors the power source connection status and provides this information to the control circuit. The control circuit adjusts the load switch state based on this feedback signal, turning off the switch when disconnection is detected to prevent reverse current damage while maintaining efficient power transmission when connected.

Inventive Principle:

Principle #23Feedback

2Difficulty of detecting and measuring

If voltage comparison is used to detect power source disconnection, then disconnection detection capability is provided, but the low voltage difference due to low ON resistance makes accurate detection difficult

Engineering Contradiction:

Improvedisconnection detection capabilityVSAvoiddetection accuracy

Core Design Contradiction:

Difficulty of detecting and measuringVSMeasurement precision

Solution Approach 1:

The patent introduces an intermediary approach by using a detection circuit that measures the voltage difference between input and output ports during a specific detection period when the load switch is in a known state. This intermediary measurement method overcomes the difficulty of detecting small voltage differences caused by low ON resistance, enabling accurate disconnection detection.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent applies parameter changes by controlling the load switch to be in a specific state (off or high-side switch off) during the detection period, creating a measurable voltage difference between input and output ports. This temporary parameter change enables accurate detection of power source disconnection status that would be difficult to detect during normal operation with low ON resistance.

Inventive Principle:

Principle #35Parameter changes

3Object-affected harmful factors

If the load switch is turned off to prevent reverse current, then reverse current protection is provided, but current surge occurs upon reconnection that may damage the battery

Engineering Contradiction:

Improvereverse current protectionVSAvoidcurrent surge damage

Core Design Contradiction:

Object-affected harmful factorsVSObject-generated harmful factors

Solution Approach 1:

The patent applies preliminary action by detecting power source disconnection status before reverse current can flow, and proactively turning off the load switch to prevent damage. This preliminary detection and response prevents both reverse current damage and subsequent current surge issues upon reconnection.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent implements feedback through continuous monitoring of the power source connection status. When disconnection is detected, the control circuit receives feedback and turns off the load switch to prevent reverse current. This feedback mechanism enables the system to respond appropriately to connection changes, preventing both reverse current and current surge damage.

Inventive Principle:

Principle #23Feedback

Data Source

PatentUS10505361B2Integrated circuit with reverse current protection and power source disconnection detection

Publication Date: 2019.12.10 NXP BV

AI summary

An integrated circuit (IC) includes a switch transistor, a gate driver circuit, a current sensor circuit, a voltage drop regulation circuit, and a charge-release circuit. The switch transistor is connected between input and output ports of the IC, and receives an input signal from a power source and provides the input signal as an output signal to the output port. The current sensor circuit detects the current through the switch transistor. The gate driver circuit drives the switch transistor using a control signal. The voltage drop regulation circuit is activated when the current flowing through the switch transistor is low. The voltage drop regulation circuit controls the control signal to increase the voltage across the switch transistor. When the power source is disconnected, the charge-release circuit transfers residual charge from the input port of the IC to ground.