Low-Voltage Detector for DC-DC Converter UVLO

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Solution Overview

Problem

Existing DC-DC converters face challenges in accurately detecting high-side Under Voltage Lock-Out (UVLO) events due to noisy and unstable BOOT voltages, leading to inefficiencies and potential short circuits, especially when the BOOT capacitor lacks sufficient energy or capacitance, causing driver failure and increased on-state resistance.

Innovation Solution

A low-voltage detector is implemented to monitor high-side UVLO events by utilizing a current generator architecture that compares reference currents from both high-side and low-side voltage domains, enabling accurate detection and communication of UVLO events to control circuitry, thereby ensuring reliable driver operation and preventing short circuits.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If BOOT capacitor is used to provide voltage for driver operation, then driver can be powered in high-side voltage domain, but BOOT voltage becomes noisy and unstable when capacitor lacks sufficient energy or capacitance

Engineering Contradiction:

ImproveBOOT capacitor energy storageVSAvoiddriver operation reliability

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

The low-voltage detector is configured to detect UVLO events before they cause driver failure. By monitoring the voltage difference between first and second voltages in advance, the system can trigger protective actions (such as disabling the driver or switching to alternative power supply) before the BOOT capacitor voltage becomes insufficient, thereby preventing unreliable driver operation.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The detector provides continuous feedback about the voltage difference between the first voltage (from BOOT capacitor) and second voltage (from stable power supply). This feedback mechanism allows the control circuit to adjust its operation based on the actual voltage conditions, ensuring reliable driver operation by compensating for BOOT capacitor voltage drops or instability.

Inventive Principle:

Principle #23Feedback

2Ease of operation

If high-side UVLO detection is implemented using BOOT voltage, then detection can be performed in high-side voltage domain, but detection accuracy deteriorates due to noisy and unstable BOOT voltage

Engineering Contradiction:

Improvehigh-side UVLO detection capabilityVSAvoidUVLO event detection accuracy

Core Design Contradiction:

Ease of operationVSMeasurement precision

Solution Approach 1:

The detector uses a second voltage from a stable low-side power supply as an intermediary reference for detecting UVLO events. Instead of directly comparing BOOT voltage to a fixed threshold (which would be inaccurate due to BOOT noise), the system compares the first voltage (derived from BOOT) to the second voltage (from stable supply) through a controlled current comparison process, thereby achieving accurate detection despite BOOT voltage instability.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent replaces direct voltage threshold comparison (analog measurement susceptible to noise) with a current comparison mechanism. By converting the voltage detection problem into a current comparison problem through controlled current generators, the system achieves more accurate and noise-immune UVLO detection, as current comparison is less susceptible to voltage noise and instability.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Device complexity

If simple voltage threshold comparison is used for UVLO detection, then detection circuit can be simple, but detection accuracy is insufficient under noisy voltage conditions

Engineering Contradiction:

Improvedetection circuit complexityVSAvoidvoltage difference detection accuracy

Core Design Contradiction:

Device complexityVSMeasurement precision

Solution Approach 1:

The patent replaces direct voltage threshold comparison with a current comparison mechanism. Current generators convert the voltage difference into proportional currents, which are then compared with high precision. This substitution transforms a noisy voltage measurement problem into a more accurate current measurement problem, achieving better detection precision without proportionally increasing circuit complexity.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The detector changes the parameter being measured from voltage directly to current. By using current generators that produce currents proportional to the voltage difference, and comparing these currents against a reference, the system achieves more accurate detection. This parameter transformation exploits the fact that current comparison is less susceptible to noise and can be performed with higher precision using standard circuit techniques.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS10591518B1Apparatus and system of a low-voltage detector

Publication Date: 2020.03.17 TOWER SEMICONDUCTOR LTD

AI summary

Some demonstrative embodiments include an apparatus including a low-voltage detector to detect whether a voltage difference between a first voltage of a first voltage domain and a second voltage of the first voltage domain is lower than a predefined voltage.