Switched-Mode Power Supply Dynamic Mode Switching

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Solution Overview

Problem

Conventional LED drivers face challenges in maintaining constant current when the load is dynamically changed, such as when LEDs are shortened, leading to current spikes due to output capacitor discharge, which can damage remaining LEDs.

Innovation Solution

Implementing a method that switches from current control to voltage control just before a load change, allowing energy stored in output capacitors to be transferred back to the input, using a bidirectional power supply and recovery circuits like SEPIC converters to manage energy transfer and prevent current spikes.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a current control loop is used to regulate current through the LED chain, then the current regulation is effective when the load is static, but the system cannot maintain constant current when the load is dynamically changed

Engineering Contradiction:

Improvecurrent regulation stabilityVSAvoidresponse to dynamic load changes

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The power supply system dynamically switches between two operational modes: a first mode for normal current regulation and a second mode for rapid response to load changes. This dynamic mode switching allows the system to adapt its characteristics based on real-time load conditions, resolving the contradiction between stable regulation and dynamic responsiveness

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The system changes the operational parameters of the power supply by switching between sourcing current mode and sinking current mode. This parameter change enables the system to handle dynamic load conditions by reversing the current flow direction, allowing rapid adaptation while maintaining regulation stability

Inventive Principle:

Principle #35Parameter changes

2Adaptability or versatility

If LEDs are dynamically bypassed/shorted to change the load, then the forward voltage biasing is reduced, but the output capacitor discharges causing a current spike that can damage remaining LEDs

Engineering Contradiction:

Improvedynamic load configurationVSAvoidcurrent spike damage

Core Design Contradiction:

Adaptability or versatilityVSObject-affected harmful factors

Solution Approach 1:

The system detects anticipated load changes and preemptively switches to the second mode before the actual load change occurs. This preliminary action prevents the harmful current spike from occurring in the first place, rather than reacting after the damage has already been caused

Inventive Principle:

Principle #9Preliminary anti-action

Solution Approach 2:

Instead of allowing the output capacitor to discharge forward through the LED chain (causing harmful current spikes), the system inverts the current flow by switching to sinking mode. This reverses the current direction, forcing the capacitor to discharge backward through the power supply circuitry where it can be safely managed, thus eliminating the harmful effect

Inventive Principle:

Principle #13The other way round (Inversion)

3Speed

If the current spike occurs quickly and is driven by output capacitors, then the load change response is fast, but the current control loop cannot regulate the spike effectively

Engineering Contradiction:

Improveload change response speedVSAvoidcurrent regulation effectiveness

Core Design Contradiction:

SpeedVSReliability

Solution Approach 1:

The system performs preliminary action by detecting anticipated load changes and switching modes before the actual load change and current spike occur. This timing allows the system to be in the correct operational state to handle the rapid transition, maintaining both speed and regulation effectiveness

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The control circuit acts as an intermediary that detects load changes and mediates the transition between operational modes. This intermediary function allows the system to bridge the gap between the fast-acting capacitor discharge and the slower current control loop, enabling effective regulation of rapid current spikes

Inventive Principle:

Principle #24Intermediary (Mediator)

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

This approach effectively mitigates current spikes during dynamic load changes, ensuring stable power supply and preventing LED damage by smoothly transitioning output voltage and recovering energy, thus enhancing the reliability of LED drivers.

Implementation Method 1

switching regulation of the power supply from sourcing a current to the load in the first mode to sinking the current from the load in a second mode... transferring energy from the output port of the power supply to an input port of the power supply

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Data Source

PatentUS9584022B1System and method for a switched-mode power supply

Publication Date: 2017.02.28 INFINEON TECHNOLOGIES AG

AI summary

In accordance with an embodiment, a method includes receiving an indication of a changed load condition or voltage characteristic of a power supply providing power to a load via an output port of the power supply in a first mode, and switching regulation of the power supply from sourcing a current to the load in the first mode to sinking the current from the load in a second mode in response to receiving the indication of the changed load condition or voltage characteristic. Sinking the current from the load in the second mode includes controlling the power supply to transfer energy from the output port of the power supply to an input port of the power supply.