LED Driver IC Voltage Sampling for Low-Loss Current Regulation

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Solution Overview

Problem

Conventional driver ICs for electrical loads, such as LEDs, face efficiency deterioration due to power loss and heat generation from resistors used for current detection, especially when load current increases, leading to reduced overall efficiency in portable electronic devices.

Innovation Solution

A driver IC with a sample-and-hold circuit synchronized with a pulse width modulated signal and a comparator with push-pull function is used to regulate driving voltage by sampling and holding the minimum voltage across current sources and comparing it with a reference threshold, enabling efficient feedback and reduced power consumption.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If resistors are used for current detection in conventional power supply systems, then current detection function is achieved, but power loss increases and efficiency deteriorates

Engineering Contradiction:

Improvepower lossVSAvoiddetection accuracy

Core Design Contradiction:

Loss of energyVSReliability

Solution Approach 1:

The patent replaces the conventional resistor-based current detection method with a capacitor-based voltage sampling system. Instead of using resistors to detect current (which causes power loss), the invention uses capacitors to sample and hold voltage signals that represent current information, thereby eliminating the power loss associated with resistive detection while maintaining detection functionality.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent introduces a capacitor as an intermediary element between the power supply and the control circuit. This capacitor samples and holds the voltage signal during the off-period of the switching cycle, acting as a mediator that transfers current information without requiring continuous resistive detection, thus reducing power loss while enabling accurate current monitoring.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Adaptability or versatility

If DC-DC conversion type power circuit is used to generate different voltage, then voltage regulation capability is improved, but device complexity increases

Engineering Contradiction:

Improvevoltage regulation capabilityVSAvoidcircuit complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent combines the voltage sampling, holding, and comparison functions into a single integrated control circuit that works in conjunction with the existing switching regulator. By merging these functions into one cohesive system rather than using separate complex DC-DC conversion circuits, the invention achieves voltage regulation capability while keeping the overall device complexity manageable.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The control circuit automatically samples the voltage during the on-period and holds it during the off-period, with the capacitor self-charging and self-discharging in synchronization with the switching cycle. This self-service mechanism eliminates the need for additional complex control circuits while maintaining voltage regulation capability.

Inventive Principle:

Principle #25Self-service

3Power

If load current is increased to drive more electrical loads, then driving capability is improved, but power loss due to detection resistors increases

Engineering Contradiction:

Improvedriving capabilityVSAvoiddetection power loss

Core Design Contradiction:

PowerVSLoss of energy

Solution Approach 1:

The patent replaces resistive current detection with capacitive voltage sampling. Since capacitors do not dissipate power like resistors, the invention enables increased load current driving capability without the proportional increase in detection power loss that would occur with resistive methods. The capacitor samples voltage without continuous power dissipation.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

4Ease of operation

If voltage sampling and holding is performed without synchronization, then circuit operation is simplified, but stability at low duty cycles deteriorates

Engineering Contradiction:

Improvecircuit operation simplicityVSAvoidoperation stability

Core Design Contradiction:

Ease of operationVSStability of the object's composition

Solution Approach 1:

The patent implements periodic synchronization between the voltage sampling operation and the switching regulator's operating cycle. The capacitor samples the voltage during the on-period and holds it during the off-period, with this periodic action synchronized to the switching frequency. This synchronization ensures stable operation at low duty cycles while maintaining relatively simple circuit operation.

Inventive Principle:

Principle #19Periodic action

Data Source

PatentUS20110266962A1Driver IC for electrical load and driving method thereof

Publication Date: 2011.11.03 SILICON WORKS CO LTD

AI summary

A driver IC for electrical loads, suitable for regulating a driving voltage depending upon a feedback signal and supplying a regulated driving voltage to a power supply line to which load strings are connected in parallel. The driver IC includes driving current sources respectively connected to the load strings through regulated voltage nodes and configured to supply driving current to the load strings in response to a control signal; sensing units configured to sense and output a minimum voltage among voltages of the regulated voltage nodes; a sample-and-hold circuit configured to sample, hold and output the minimum voltage in response to the control signal; and a comparator configured to compare an output voltage of the sample-and-hold circuit and a reference threshold voltage and generate the feedback signal.