Illustration of DC/DC power supply for different power LED general lighting application requirements and circuit solutions

For DC/DC powered LED lighting applications, the discussion can be based on different power ranges.

1) 1~3W DC/DC LED buck application

Typical 1-3W DC/DC LED buck lighting applications include MR11/MR16, automotive lighting, solar power supply, etc. The input voltage of such applications is 5 to 28 Vdc, supports 350mA and 700mA constant current output, frequency of 500kHz to 2MHz, energy efficiency of not less than 90%, and operating temperature range of -40℃ to 125℃. In such applications, the CAT4201 buck LED driver from ON Semiconductor can be used . This device has a patented switch control architecture, can drive 7 series LEDs (at 24V input), energy efficiency up to 94%, and provides protection features such as LED open circuit protection, current limiting and overheat protection.

Figure 1: CAT4201 1~3W DC/DC LED solution.

2) 1~30W DC/DC LED buck application

Typical 1-30W DC/DC LED buck applications include secondary-side DC/DC LED drivers in MR16 spotlights and street lighting. In such applications, the input voltage range is 7 to 120 Vdc, the output voltage range is 6 to 110 Vdc, and it supports 350mA, 700mA or 1A constant current output, with an energy efficiency of no less than 90%. Such applications can use ON Semiconductor's NCL30100 buck LED driver, which has an external switch MOSFET, provides flexible input voltage and output current design, and has an energy efficiency of more than 95%. See Figure 2 for its application circuit diagram.

Figure 2: 1-30W LED buck application based on NCL30010 and 3-20W LED boost application based on NCP3066.

3) 1~20W DC/DC LED boost application

Typical 3-20W DC/DC LED boost applications are common in DC/DC LED drivers. The input voltage of such applications is 5 to 28Vdc, supporting 350mA or 700mA constant current output, and energy efficiency of not less than 90%. Such applications can use ON Semiconductor's NCP3065/NCP3066 LED drivers. NCP3065/NCP3066 can be configured as buck, boost, single-ended primary inductor converter (SEP IC ) and inverter, and provides a corresponding automotive application version, namely NCV3065/NCV3066. Figure 2 shows the NCP3066 boost configuration LED application circuit diagram.

4) 1~3W flashlight LED boost/buck application

There are both boost and buck types in 1-3W flashlight LED applications. The input voltage range of boost applications is 1 to 2.5 Vdc, and the operating frequency is up to 1.2MHz; the input voltage range of buck applications is 4 to 5.5 Vdc, and the frequency is up to 1.7MHz. Both types of applications need to support 350mA or 600mA constant current output, and the energy efficiency is higher than 90%. In the 1-3 W flashlight boost LED application, ON Semiconductor's NCP1421 boost DC/DC converter can be used, and the flashlight buck LED application with the same power range can use ON Semiconductor's NCP1529 low-voltage buck converter. The application circuit diagrams are shown in Figure 3.

Figure 3: NCP1421-based boost and NCP1529-based buck 1-3W flashlight LED applications.