8W to 25W LED general lighting application requirements and solutions

8W to 25W LED general lighting application requirements and solutions: without PFC and with PFC

In 8W-25W AC-DC LED lighting applications, we have to consider two cases. One is that the application does not require power factor correction (PFC). On the other hand, the U.S. Department of Energy (DOE) "Energy Star" solid-state lighting (SSL) specification stipulates that power factor correction (PFC) must be mandatory for any power level. This standard applies to a series of specific products, such as recessed lights, cabinet lights and table lights, among which the LED driver power factor must be greater than 0.7 for residential applications and greater than 0.9 for commercial applications. However, this standard is a voluntary standard, which means you can choose not to comply or comply. Therefore, another case to consider is that PFC is required.

In the 8 W to 25 W AC-DC LED lighting that does not require PFC, typical applications include PAR30, PAR38 and recessed lights. In such applications, the input voltage requirement is 85~135 Vac or 185~264 Vac (or universal input), the energy efficiency requirement is greater than 80%, and protection features such as short-circuit protection and open-circuit protection are provided. The constant current output current is 350 mA, 700 mA and 1 A. Accordingly, ON Semiconductor's NCP1028 or NCP1351 can be used, as shown in Figure 2.

Figure 2: 8-15/25 W AC-DC LED lighting solution based on NCP1028 and NCP1351 (without PFC)

Among them, NCP1028 is an enhanced monolithic switch control IC that provides 800 mA peak current, as well as over-power protection, built-in slope compensation and input undervoltage protection. It is suitable for providing output power of several watts to 15 W in applications with universal wide power input. In addition to the non-PFC solution based on NCP1028, ON Semiconductor now also provides a PFC solution based on NCP1028. NCP1351 is a fixed on-time, variable off-time pulse width modulation (PWM) controller suitable for cost-critical low-power offline flyback switching power supply applications. This device supports frequency retracement and also has features such as latch input, natural frequency jitter, negative current sensing and an extended power supply voltage range.

In terms of 8 W to 25 W AC-DC LED lighting that requires PFC, typical applications are also PAR30, PAR38 and recessed lights. The input voltage specification of this type of application is 90 to 264 Vac, the energy efficiency requirement is 80%, and it supports 350 mA, 700 mA and 1 A constant current output, provides short circuit and overvoltage protection, and the power factor requirement is higher than 0.9. This type of application is suitable for ON Semiconductor's NCL30000 single-stage power factor correction LED driver. The single-stage topology saves a dedicated PFC boost stage, reduces the number of components, and helps reduce the total system cost. The NCL30000 provides a power factor higher than 0.9 and meets the IEC Class C harmonic content requirements. This device can directly drive LEDs with precise constant current output control, with an efficiency of more than 80% at lower output powers of 5 to 15 W, a typical efficiency of more than 83%, and supports existing dimming schemes such as TRIAC.

Figure 3: 8-25 W AC-DC LED lighting solution based on NCL30000 (with PFC)