LED Driver Delayed Gate Signal Control
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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, as well as 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 adjusting the energy transfer during active and inactive phases.
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 means generates the load switch gate signal to transition before the converter switch gate signal transitions. This preliminary action allows the load switch to be ready to receive current before the converter switch closes, preventing current overshoot while maintaining simple switching control
2Measurement precision
If the LED load is switched independently of the SMPS using a separate switch, then the light output timing can be precisely controlled, but this increases the device complexity and requires additional components
Solution Approach 1:
The patent combines the converter switch and load switch into a single switching circuit controlled by a unified control means. The control means generates both gate signals with different timing characteristics, achieving independent load switching without adding separate control circuits or increasing device complexity
3Ease of manufacture
If a conventional SMPS with simultaneous switching is used, then the circuit design is straightforward, but excess light from overshoot detracts from viewing quality and reduces overall efficiency
Solution Approach 1:
By transitioning the load switch gate signal before the converter switch gate signal, the system prepares the load switching path in advance. This prevents energy loss from current overshoot and ensures that when the converter switch closes, current flows efficiently through the load without excessive light output that would waste energy
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, allowing for more precise light output control, enhancing the viewing experience and increasing efficiency and brightness in DLP projection systems.
Implementation Method 1
a switched-mode power converter for providing power to an LED load connected across output terminals of the converter, and wherein the converter comprises a number of energy storage elements and a first semiconductor switch
Data Source
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 (Q1); 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).