Power factor correction is to correct the distortion current to a sinusoidal current and make it in phase with the voltage, so that the power factor is close to 1. Increasing the power factor is of great significance for reducing energy consumption, reducing the size and weight of power supply equipment, reducing the cross-sectional area of ​​the conductor, and weakening the external radiation and conduction interference of the power supply equipment. Therefore, LED drivers with power factor correction are becoming more and more popular. This article will introduce the design method and application scheme of the energy-efficient single-stage power factor correction LED driver by using two single-segment isolated power factor correction LED drivers NCP1652A and NCL30001 from ON Semiconductor.

Single-segment isolated power factor correction LED driver solutions include: NCL30000-based offline high power factor Triac dimmable LED driver; NCP1044 boost converter based LED single-segment power factor correction driver for high voltage LED string Solution; buck-boost flyback converter based on NCL1652A controller and constant current LED driver for area lighting applications based on NCL30001 and NCS1002. This paper mainly introduces the design scheme of single-segment isolated power factor correction LED driver with NCP1652A and NCL30001 as examples.

Both the NCL1652A and NCL30001 operate in continuous conduction mode (CCM), which integrates PFC and isolated DC-DC conversion circuitry and provides constant current to directly drive the LEDs. It is equivalent to the integration of AC-DC conversion and LED driver two parts of the circuit, all located in the lighting fixture, eliminating the linear or DC-DC converter integrated in the LED strip, the power conversion section of this integrated solution Less, reducing the number of components used (such as optical components, LEDs, electronic components and printed circuit boards, etc.), reducing system cost and supporting higher overall energy efficiency of LED power supplies. Of course, this solution has higher power density and may not be suitable for all regional lighting applications. Its optical pattern may be more suitable for low-power LEDs. Typical applications include LED street lights, exterior wall lights, wall washers, and refrigerator cabinet lighting. Wait.

LED driver for universal power and telecom power

Designed for continuous conduction mode (CCM) buck-boost flyback converter applications, the NCP1652A controller provides a second gate drive output for active clamp buffering in higher power applications. The voltage spike caused by the leakage inductance energy of the flyback transformer is an important issue. The NCP1652A allows the design of a relatively new and simple off-line power factor corrected 15 Vdc and higher output power supply using an isolated single-segment conversion topology for general purpose power, telecom distributed power front ends and for area illumination and distribution. Constant voltage LED driver for lighting applications. Based on the NCP1652A controller, the single-segment power factor correction LED driver, the circuit schematic shown in Figure 1, using a universal AC input 48V DC, 2A power supply, flyback transformer T1 only requires relatively few magnetic current components It can be used in an efficient continuous conduction mode. The test results show that this solution can provide nearly 90% energy efficiency, and the power factor exceeds 0.95 under most typical loads.

Figure 1 Complete schematic of a single-segment converter based on the NCP1652A

LED driver for area lighting applications

The NCL30001 controller's specifications also include high voltage start-up circuitry, voltage feedforward for improved loop response, input undervoltage detection, internal overload timer, shackle input, and high precision multipliers that reduce input line harmonics. NCS1002 is a secondary-side constant voltage constant current (CVCC) controller suitable for regional lighting applications such as LED street lights. With the NCL30001 controller, it can design a high-efficiency, dimming LED driver demo board that can be used directly for requirements. Constant current output from 40W to 100W power range, current can be adjusted from 0.7A to 1.5A, with a wider range of high power and high brightness LEDs, suitable for regional lighting applications such as overhead, tunnel, parking lot and road lighting Constant current LED driver. Based on the NCL30001 and NCS10002 90W demo boards, as shown in Figure 2, the test results show that the energy efficiency of 50W output power, 1000mA output voltage / 48V forward voltage drop conditions is higher than 87%, under 50% to 100% load conditions The power factor is higher than 0.9. This special design is optimized for LEDs that require more than 3A drive capability, such as Luminus Devices' CSM360 and SST90. This design can support up to 8 SST90 series or 2 CSM360 devices. The CSM360 LED has a nominal forward voltage of 12.8 V at a drive current of 3.2 A, which can produce 1600-3900 lumens depending on color temperature and luminous flux.

Figure 2 90W demo board based on NCL30001 and NCS10002

to sum up:

The use of a single-segment topology can significantly reduce the material cost of the overall component while achieving high power factor and good startup characteristics in a compact structure. In order to ensure the robustness and reliability of the solution, multiple protections are used for the circuit in the above design.

Guangzhou Ehang Electronic Co., Ltd. , https://www.ehangmobile.com