LED Driving Circuit with Boost-Buck Converter Mode Switching

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Solution Overview

Problem

Existing driving circuits for LEDs, particularly in railway safety systems, are complex and inefficient, requiring multiple LEDs to achieve desired luminosity due to the lack of adaptable converters that can seamlessly transition from boost to buck converter modes as LED efficiency improves, necessitating additional components and increased complexity.

Innovation Solution

A driving circuit that can be converted between boost and buck converter modes by adding or removing a simple supplementary circuit with minimal electronic components, eliminating the need for an inductor, allowing for efficient operation with fewer LEDs by using a boost converter with an additional circuit that includes a P-MOSFET, capacitor, Zener diode, and resistors to manage voltage and current.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If a boost converter is used to drive LEDs, then the circuit can operate with higher voltage output, but the circuit complexity increases and cannot adapt to reduced LED counts

Engineering Contradiction:
Improveconverter mode adaptabilityVSAvoidcircuit complexity
Core Design Contradiction:
Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent applies universality by designing a circuit that can function as both a boost converter and a buck converter. The additional circuit includes components (P-MOSFET, capacitor, Zener diode, resistors) that enable the same base circuit to operate in two different converter modes, allowing adaptability without requiring separate dedicated circuits for each mode.

Inventive Principle:
Principle #6Universality (Multi-functionality)

Solution Approach 2:

The patent implements dynamics by enabling the circuit to dynamically switch between boost converter mode and buck converter mode. The additional circuit allows the converter to adapt its operating characteristics based on the required output voltage and current, providing dynamic flexibility rather than a fixed configuration.

Inventive Principle:
Principle #15Dynamics

2Use of energy by moving object

If LED efficiency improves and fewer LEDs are needed, then energy efficiency increases, but the existing boost converter circuit cannot drive the reduced number of LEDs effectively

Engineering Contradiction:
Improveenergy efficiencyVSAvoidconverter adaptability to LED count
Core Design Contradiction:
Use of energy by moving objectVSAdaptability or versatility

Solution Approach 1:

The patent applies universality by creating a converter circuit that serves multiple purposes - it can drive both higher current loads (multiple LEDs) and lower current loads (fewer efficient LEDs) by switching between boost and buck converter modes, making the circuit universally applicable to different LED configurations.

Inventive Principle:
Principle #6Universality (Multi-functionality)

Solution Approach 2:

The patent implements parameter changes by allowing the converter to change its operating parameters (voltage conversion direction, current levels) based on the LED configuration. The additional circuit enables the converter to adjust its electrical parameters to match the requirements of different numbers of LEDs, from many inefficient LEDs to fewer efficient LEDs.

Inventive Principle:
Principle #35Parameter changes

3Adaptability or versatility

If an integrated circuit is designed to function as both boost and buck converter, then adaptability improves, but the construction and wiring become complex

Engineering Contradiction:
Improvedual converter functionalityVSAvoidconstruction and wiring complexity
Core Design Contradiction:
Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent applies segmentation by dividing the converter into a base circuit and an additional circuit. The additional circuit contains the extra components (P-MOSFET, capacitor, Zener diode, resistors) that enable dual functionality, while the base circuit remains relatively simple. This segmentation allows the complex functionality to be added as a supplement rather than redesigning the entire circuit.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The patent implements merging by combining the additional circuit components with the existing boost converter circuit to create a unified dual-mode converter. Rather than creating separate boost and buck converter circuits, the additional components are integrated into the existing circuit architecture, merging functions into a single cohesive system.

Inventive Principle:
Principle #5Merging (Combining)

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

Enables cost-effective and efficient operation with reduced component count, future-proofing the system as LED efficiency improves, allowing the same luminosity to be achieved with fewer LEDs, demonstrated through test arrangements showing effective voltage and current management.

Implementation Method 1

the boost converter 10 comprises an inductor L1

Methodology Applied
Scientific EffectElectromagnetic induction: Electromagnetic Induction

Implementation Method 2

the capacitor C1 is charged via the diode D1 by the subsequent induction peak of the inductor L1

Methodology Applied
Scientific EffectCapacitance: Capacitance

Implementation Method 3

the capacitor C1 is charged via the diode D1 by the subsequent induction peak of the inductor L1

Methodology Applied
Scientific EffectDiode rectification: Diode

Implementation Method 4

When the N-MOSFET 14 is switched on in the switching controller 11, the drain D of the N-Mosfet 14 becomes low. As the gate G of the P-Mosfet 21 is connected to the drain D of the N-MOSFET 14, the P-MOSFET 21 is connected through and the electric charge stored in capacitor C1 is transferred into capacitor C2

Methodology Applied
Scientific EffectField effect transistor conduction:

Implementation Method 5

the Zener diode DZ1, two resistors R1, R2... the Zener diode DZ1 limits voltage peaks between gate G and source S of the P-MOSFET 21

Methodology Applied
Scientific EffectZener breakdown: Diode

Data Source

PatentEP2413660B1Driving circuit with a boost converter transformed into a buck converter for driving power LEDs
Publication Date: 2014.03.05 THALES DEUTLAND GMBH
  • EP2413660B1 patent drawingFigure 1
  • EP2413660B1 patent drawingFigure 2
  • EP2413660B1 patent drawingFigure 3a

AI summary

The invention relates to a driving circuit (1) for driving LEDs (2), in particular of an LED signal, comprising a boost converter (10) for converting an input voltage (Vcc) into a higher output voltage (VHigh), with the boost converter (10) comprising an inductor (L1), wherein for transforming subsequently the boost converter (10) into a buck converter which converts the input voltage (Vcc) into a lower output voltage (VLow), an additional circuit (20) is provided between the boost converter (10) and the LEDs (2), with the additional circuit (20) comprising no inductor.