LED Driver Gate Signal Delay for Current Overshoot
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional LED drivers for DLP projection systems experience noticeable overshoot or undershoot in LED current and light output due to simultaneous gate signal transitions, leading to reduced efficiency and brightness, and a compromised viewing experience.
Innovation Solution
An LED driver with a switched-mode power converter and two semiconductor switches, where the gate signal for the load switch is delayed relative to the converter switch, ensuring precise control and minimizing overshoot by allowing the capacitor to discharge before the LED load is turned on, thus stabilizing the LED current at the desired intensity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If gate control signals for the converter switch and load switch are issued simultaneously, then the switching operation is simple and synchronized, but this results in noticeable overshoot or undershoot on the LED current and light output
Solution Approach 1:
The control processor delays the gate control signal for the load switch relative to the converter switch signal. This preliminary timing adjustment ensures that the load switch is already in the appropriate state when the converter switch transitions, preventing current overshoot or undershoot while maintaining simple switching operation.
2Adaptability or versatility
If the load switch is added in series with the lighting load to enable independent switching, then the LED can be turned on and off independently, but this increases the device complexity
Solution Approach 1:
The load switch serves multiple functions: it enables independent LED lighting control, works in conjunction with the converter switch for precise current control, and integrates with the existing SMPS architecture. This multi-functionality justifies the added component while providing versatile control capabilities.
3Ease of operation
If simultaneous gate signals are used for converter and load switches, then the control timing is simple and synchronized, but excess light from overshoot is wasted leading to reduced efficiency
Solution Approach 1:
The control processor monitors the switching states and adjusts the timing of the load switch gate signal based on the converter switch signal transitions. This feedback mechanism ensures optimal timing that prevents overshoot and maximizes light output efficiency while maintaining synchronized control.
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 eliminates or reduces noticeable overshoot in LED current, enhancing the precision of light output, improving the viewing experience, and increasing efficiency and brightness in DLP projection systems.
Implementation Method 1
the converter comprises a number of energy storage elements and a first semiconductor switch
Implementation Method 2
a field-effect transistor (FET) is a suitable choice of switch for this purpose
Data Source
Figure 1
Figure 2
Figure 3
AI summary
LED driver (1) comprising a switched-mode power converter (10) for providing power to an LED arrangement (100) connected across output terminals of the converter (10), and wherein the converter (10) comprises a number of energy storage elements (L, C) and a first semiconductor switch (Ql); a second semiconductor switch (Q2) connected in series with the LED arrangement (100); a control means (11) realized to generate a second control signal (G2) for the second semiconductor switch (Q2), such that a transition of the second control signal (G2) is delayed relative to a corresponding transition of a first control signal (G 1) for the first semiconductor switch (Q 1). The invention further describes a projection arrangement (2); and a method of driving an LED arrangement (100).