High-power LED power solution based on LYTSwitch-4

1 Overview

PowerInt's LYTSwitch-4 family of products, LYT4211-4218/4311-4318, combines a controller and a high-voltage, high-power FET in the same package. The controller provides high power factor and constant current output with constant current performance better than ±5%. TRIAC dimming, full brightness start-up time less than 250ms, power factor greater than 0.9, up to 92% efficiency, switching frequency 132kHz can use smaller magnetic materials. Mainly used in high power LED drivers.

The LYTSwitch-4 family features excellent turn-on characteristics for leading and trailing edge TRIAC dimming. This gives it a wide dimming range and quick start-up of the drive (even from a low conduction angle). The LED driver using the LYTSwitch-4 series does not use a large-capacity aluminum electrolytic capacitor on the primary side. This means a significant increase in the life of the drive, especially in bulbs and other high temperature applications.

The LYTSwitch-4 series features large dimming ratios, low startup current, low cost and long life.

2 System Block Diagram of LYTSwitch-4 Controller

The LYTSwitch-4 chip is highly integrated with primary control technology that eliminates opto-isolators and reduces component count. In this way, an inexpensive single-sided printed circuit board can be used. Integrating PFC and CC functions into a single stage also helps reduce costs and increase efficiency. Its 132 kHz switching frequency allows it to use small, low-cost magnetic components.

The LYTSwitch-4 controller includes: an oscillator, feedback (detection and logic) circuitry, 5.9V regulator, hysteretic overtemperature protection, frequency jitter, cycle-by-cycle current limit, auto-restart, inductor correction, power factor, and constant current control. Figure 1 shows the system block diagram of the LYTSwitch-4 controller.

Figure 1 LYTSwitch-4 block diagram

3 LYTSwitch-4 performance and typical applications

3.1 Main performance characteristics of LYTSwitch-4

• Better than ±5% constant current regulation

• TRIAC dimmable to less than 5% output

• Quick start "250ms (full brightness)

• "1s at (10% brightness)

• High power factor "0.9

• Easily meet EN61000-3-2 standard, optimized design less than 10% THD

• Up to 92% efficiency

• 132kHz switching frequency for small size magnetic components

• High performance, combined drive, controller, switch

The LYTSwitch-4 series enables off-line LED drivers with high power factor and easily meets international standards for THD and harmonics. Its output current is tightly regulated and is better than ±5% constant current performance. In a typical application, up to 92% efficiency can be easily achieved. And support a variety of TRIAC dimmer options.

3.2 LYTSwitch-4 Typical Application Circuit

As shown below, Figure 2 is a typical application circuit diagram of LYTSwitch-4.

Figure 2 LYTSwitch-4 typical application circuit

The LYTSwitch-4 family features excellent turn-on characteristics for leading and trailing edge TRIAC dimming. This gives it a wide dimming range and quick start-up of the drive (even from a low conduction angle). The LYTSwitch-4 series features large dimming ratios, low startup current, low cost and long life.

The LYTSwitch-4 chip is highly integrated with primary control technology that eliminates opto-isolators and reduces component count. In this way, an inexpensive single-sided printed circuit board can be used. Integrating PFC and CC functions into a single stage also helps reduce costs and increase efficiency. Its 132 kHz switching frequency allows it to use small, low-cost magnetic components. The LED driver using the LYTSwitch-4 series does not use a large-capacity aluminum electrolytic capacitor on the primary side. This means a significant increase in the life of the drive, especially in bulbs and other high temperature applications.

4 high power TRIAC dimming LED driver

4.1 Main features of high power TRIAC dimming LED driver

• High efficiency, 120V ≥ 85%

• Wide range of dimmer compatibility (within NEMA SSL6 dimming curve) and a wide selection of USTRIAC-based dimmers

• Enhanced user experience

• No flicker, monotonic dimming

• Fast monotonic start (200ms) - no significant delay

• Turn on and off at almost the same dimming angle - no flash off

•low cost

• Single stage PFC combined with accurate primary side regulated constant current output

• Single-sided PCB with a small number of components

• Integrated protection and reliability features

• Output open / output short circuit automatic recovery protection

• Fast power line input overvoltage shutdown, increased pressure resistance during line faults

• No MOV, can withstand ±2500V ring wave and ±500V differential surge

• Automatic recovery of large hysteresis thermal shutdown to protect components and printed circuit boards

• Complies with IEC 61000-4-5 ring wave, IEC 61000-3-2C total harmonic distortion and IEC CISPR 15/EN55015 B conducted EMI standard

4.2 High Power TRIAC Dimming LED Driver

The document describes an isolated high power factor TRIAC dimmable LED driver that is used to drive a nominal 36V LED string voltage (550mA) with a typical input voltage range of 90VAC~132VAC. The LED driver uses the LYT4317E from the LYTSwitch-4 chip family.

Figure 3 High power TRIAC dimming LED driver circuit diagram

Its topology is a single-stage power factor correction flyback with high isolation efficiency, high power factor, low THD, and low component count. Its high power factor and low THD are achieved through the use of the LYTSwitch-4 IC, which also provides a complex, range of protection features including automatic restart of open control loops and output short-circuit inclusion. Input overvoltage provides extended line fault and surge withstand, and its precise hysteretic thermal shutdown ensures a safe average PCB temperature under a variety of conditions.

5 Conclusion

This paper presents a high power LED power solution based on LYTSwitch-4. The LYTSwitch-4's excellent turn-on characteristics are fully utilized in this solution, allowing it to have a wide dimming range and to quickly start the driver (even from a low conduction angle); and its input overvoltage provides an extension Line fault and surge withstand, its precise hysteretic thermal shutdown ensures a safe average PCB temperature under a variety of conditions. The solution has been verified by the analysis to have a large dimming ratio, low starting current, low cost and long life.

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