High-Voltage LED Driver Using Segmented DC-DC Conversion
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Solution Overview
Problem
Current high-voltage LED drive schemes face inefficiencies due to high voltage stress on components, reverse recovery issues in diodes, and the need for multiple stages in power processing, which limits efficiency and increases component size.
Innovation Solution
The proposed solution involves an isolated DC-DC converter providing multiple voltage levels, allowing non-isolated DC-DC converters to regulate a single voltage difference, reducing voltage stress and enabling efficient power processing in a single stage, using buck, boost, or buck-boost converters to minimize component size and improve switching frequency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If an isolated DC-DC converter with boost converter is used to drive high-voltage LED strings, then the LED string can be driven with required high voltage (several hundred volts), but the breakdown voltages of switch and diode must be higher than LED string voltage, increasing component voltage stress and size
Solution Approach 1:
The patent divides the single high-voltage LED string into multiple lower-voltage LED strings connected in parallel. Each string is driven by a separate converter, reducing the voltage stress on individual components. For example, instead of one string requiring 600V, multiple strings operate at lower voltages, allowing use of components with lower breakdown ratings.
Solution Approach 2:
The patent employs a unified isolated DC-DC converter architecture that provides multiple identical output channels, each capable of driving an LED string. This multi-functional design allows the same converter circuitry to serve multiple purposes, reducing overall system complexity and component variety while maintaining high-voltage drive capability through parallel operation.
2Power
If a boost converter is used with high-voltage diode, then LED string can be driven, but the high voltage diode has serious reverse recovery issue, limiting LED driver efficiency
Solution Approach 1:
The patent replaces the problematic high-voltage diode in the boost converter with a MOSFET that replicates the diode's rectification function. The MOSFET, controlled by appropriate gate signals, performs the same one-way current conduction function as a diode but without the reverse recovery issue, thereby eliminating the efficiency loss associated with diode reverse recovery at high voltages.
Solution Approach 2:
The patent substitutes the passive diode component with an active MOSFET device, transitioning from a simple passive rectification mechanism to an actively controlled semiconductor switch. This substitution eliminates the inherent reverse recovery limitation of diodes while providing equivalent or superior rectification performance in the boost converter circuit.
3Reliability
If switching frequency is kept low to reduce component size in high-voltage application, then component breakdown voltage requirements are met, but component size cannot be minimized
Solution Approach 1:
The patent segments the high-voltage power conversion task into multiple parallel low-voltage channels. By operating multiple converters at lower voltages, the system can use higher switching frequencies in each channel, which reduces the size of magnetic components (inductors and transformers) and capacitors, while the overall high-voltage output is achieved through parallel combination of these smaller components.
Solution Approach 2:
The patent changes the operating voltage parameter of the converter stages from a single high-voltage operation to multiple lower-voltage operations. This parameter change enables the use of higher switching frequencies, which directly reduces the size of energy storage components (inductors and capacitors) while maintaining the required high-voltage output capability through parallel configuration.
4Power
If two stages are used to process required LED power from V_BUS, then LED strings can be driven, but efficiency is lowered due to multiple conversion stages
Solution Approach 1:
The patent merges the voltage conversion and LED string driving functions into a single integrated isolated DC-DC converter stage. By combining these functions that were previously separated into two stages, the system eliminates one conversion stage, reducing energy losses and improving overall power efficiency while still delivering the required power to multiple LED strings in parallel.
Solution Approach 2:
The patent designs a unified converter architecture that simultaneously performs voltage conversion and drives multiple LED strings, making the converter multi-functional. This eliminates the need for separate conversion stages, reducing energy losses associated with multiple power conversions while maintaining the capability to drive multiple high-voltage LED strings through parallel output channels.
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 enhances LED driver efficiency by reducing voltage stress on components, eliminating reverse recovery issues, and allowing higher switching frequencies, resulting in smaller components and improved light distribution in large panel applications.
Implementation Method 1
An isolated DC-DC converter is used. The term isolated refers to the fact that the input and outputs of the converter are isolated by an electrical barrier, typically a transformer.
Implementation Method 2
A boost converter (comprised of S1, D1, L1, Ci1 and Co1) is applied to drive one string of LEDs.
Implementation Method 3
A MOSFET SD1 is in series with the LED string to achieve fast PWM dimming.
Implementation Method 4
A boost converter (comprised of S1, D1, L1, Ci1 and Co1) is applied to drive one string of LEDs.
Data Source
AI summary
A high-voltage LED drive scheme with multi-stage power regulation. The multi-stage power regulation applies two components of voltage to drive the LED strings. This scheme achieves high efficiency, small size and low cost.