LED Driver Circuit Voltage Sequencing for Low-Voltage Transistor Use

Solution Overview

Problem

Existing LED driver circuits face issues with high power consumption and the need for high-voltage power transistors to withstand relatively high voltage supplies, leading to increased manufacturing costs and inefficiencies.

Innovation Solution

The proposed solution involves sequencing the drive signal and supply voltage for light emitting elements such that the voltage is not increased above a predetermined allowable voltage until the transistor is turned on and not decreased below it until turned off, allowing a low-voltage transistor to be used, and implementing this control in both analog and PWM drive circuits to regulate LED brightness.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a high-voltage power transistor is used to withstand relatively high voltage supply, then the transistor can handle the voltage requirements, but the manufacturing cost increases and power consumption increases

Engineering Contradiction:

Improvetransistor voltage handling capabilityVSAvoidmanufacturing cost

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent applies preliminary action by turning on the power transistor before increasing the supply voltage to the LED string. The control circuit sequences the operations such that the transistor is activated in advance, allowing the voltage to be gradually increased without exceeding the transistor's voltage rating. This enables the use of a low-voltage transistor while still driving high-voltage LEDs, thereby reducing manufacturing cost and power consumption.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent implements dynamics by dynamically sequencing the voltage application and transistor switching operations. The control circuit adjusts the timing and sequence of voltage application to the LED string and transistor switching to ensure that the transistor never experiences voltage exceeding its rating. This dynamic control allows the system to operate with a low-voltage transistor while maintaining the ability to drive high-voltage LED strings.

Inventive Principle:

Principle #15Dynamics

2Reliability

If a high-voltage power transistor is used to withstand relatively high voltage supply, then the transistor can handle the voltage requirements, but power consumption increases

Engineering Contradiction:

Improvetransistor voltage handling capabilityVSAvoidpower consumption

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The patent applies preliminary action by turning on the power transistor before increasing the supply voltage to the LED string. The control circuit sequences the operations such that the transistor is activated in advance, allowing the voltage to be gradually increased without exceeding the transistor's voltage rating. This enables the use of a low-voltage transistor while still driving high-voltage LEDs, thereby reducing manufacturing cost and power consumption.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent implements dynamics by dynamically sequencing the voltage application and transistor switching operations. The control circuit adjusts the timing and sequence of voltage application to the LED string and transistor switching to ensure that the transistor never experiences voltage exceeding its rating. This dynamic control allows the system to operate with a low-voltage transistor while maintaining the ability to drive high-voltage LED strings.

Inventive Principle:

Principle #15Dynamics

3Productivity

If voltage is increased above allowable voltage for the transistor, then the LED string can be driven, but the transistor may be damaged

Engineering Contradiction:

ImproveLED string driving capabilityVSAvoidtransistor voltage stress

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The patent applies preliminary action by turning on the power transistor before increasing the supply voltage to the LED string. The control circuit sequences the operations such that the transistor is activated in advance, allowing the voltage to be gradually increased without exceeding the transistor's voltage rating. This enables the use of a low-voltage transistor while still driving high-voltage LEDs, thereby reducing manufacturing cost and power consumption.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent implements feedback through the control circuit that monitors the transistor state and supply voltage levels. The control circuit uses feedback signals to adjust the sequencing of voltage application and transistor switching, ensuring that the voltage never exceeds the transistor's rating. This feedback mechanism protects the transistor from voltage stress while maintaining LED string driving capability.

Inventive Principle:

Principle #23Feedback

Data Source

PatentUS9013110B2Circuit for driving light emitting elements

Publication Date: 2015.04.21 ATMEL CORP

AI summary

In one novel aspect, driving a string of light emitting elements, such as LEDs, includes applying a drive signal to circuitry that regulates a voltage appearing at a source of a transistor whose drain is coupled to one end of the string of light emitting elements and whose source is coupled to ground through a resistive element. Sequencing of the drive signal and a voltage supply signal for the light emitting elements is controlled such that the voltage supply signal is not increased above a predetermined allowable voltage for the transistor until the transistor is turned on, and such that the supply voltage is not decreased below the allowable voltage for the transistor until the transistor is turned off.