AC-DCLED lighting solutions

ON Semiconductor offers a wide range of off-line controllers and power factor correction (PFC) controllers for AC-DC power-provided LED lighting applications, with different LED applications for isolation and non-isolation requirements. In isolation applications where there is no physical electrical connection between the AC line voltage and the LED, common topologies are flyback and dual inductor plus single capacitor (LLC) half-bridge resonance. Different topologies are suitable for different power ranges or for special design requirements. For example, the flyback topology is the standard choice for medium to low power applications of less than 100W, while the LLC half-bridge topology is the preferred solution for high power and energy efficiency.

In AC-DCLED lighting applications, low-power LED applications are typically driven with constant current (CC), while constant voltage (CV) functions are used as protection functions in the case of open outputs. High-power LED applications may require the addition of power factor correction (PFC) in the circuit, where both the AC-DC conversion and the LED-driven two-part circuit may be in an integral configuration, ie, the two are fused together and are located in the illumination. Within the luminaire, a distributed configuration can also be used, as shown in Figure 2, to simplify security considerations and increase system flexibility.

From the specific power range of the application, the application of AC-DCLED lighting power solutions mainly includes:

1W-8W: G13/GU10/PAR16/PAR20 lighting

8W-25W: PAR30/PAR38 lighting

50W-300W: area lighting

1).1W-8WAC-DCLED lighting application

This type of application requires an input voltage of 90 to 264Vac and an energy efficiency of 80%. It also provides protection features such as short-circuit protection and overvoltage protection, and provides 350mA and 700mA constant current. Applications include G13, GU10, PAR16, PAR20 and recessed lights. (downlight) and so on.

ON Semiconductor's NCP1015 self-powered monolithic switching regulator can be used in this type of application. This device integrates a fixed frequency (65/100/130kHz) current mode controller and a 700V high voltage MOSFET to provide all the features needed to build a robust, low cost power supply such as soft start, frequency jitter, short circuit protection, skip cycle, Maximum peak current set point and dynamic self-powered function (no auxiliary winding required). Figure 3 shows a circuit diagram of the NCP1015 in an isolated 1W-8W range AC-DCLED lighting application. It is worth mentioning that the NCP1015 can also be used in non-isolated (high-frequency transformers in the circuit) 1W-8W range AC-DCLED lighting applications. Tapped inductors can be used in the circuit to increase the duty cycle of the MOSFET. And improve system energy efficiency and circuit performance.

Figure 3: Ansemite 8 W LED driver application circuit diagram (input voltage 85 to 264 Vac)

2).8W-25WAC-DCLED lighting application

Power Factor Correction (PFC) is mandatory for any power class specified by the US Department of Energy (DOE) Energy Star (ENERGYSTAR®) Solid State Lighting (SSL) specification. This standard applies to a range of specific products, such as recessed lights, cabinet lights and desk lamps, where the LED driver power factor for residential applications must be greater than 0.7, and for commercial applications greater than 0.9. However, this standard is a voluntary standard, that is, you can choose not to comply or comply.

Accordingly, in the 8W-25WAC-DCLED lighting application, we consider two cases, one is that the application has no power factor requirement, that is, the PFC controller is not required, and the other is the PFC controller. In applications that do not require PFC, we assume an input voltage specification of 90~132Vac or 180~264Vac (or universal input), 85% energy efficiency, short-circuit protection and open-circuit protection, and output currents of 350mA, 700mA and 1A. For constant current, the NCP1028 or NCP1351 from ON Semiconductor can be used accordingly. Among them, the NCP1028 is an enhanced single-chip switching regulator that is designed to deliver several watts to 15W of output power in general-purpose mains input applications. The NCP1028's on-resistance is lower than the NCP101x, providing 800mA peak current, with many features of the NCP101x, plus over-power protection, built-in slope compensation, and input undervoltage protection. The NCP1351 is a fixed on-time, variable off-time pulse width modulation (PWM) controller for cost-effective low-power off-line flyback switching power applications. The device supports frequency reversal and features latch-up inputs, natural frequency jitter, negative current sensing, and extended supply voltage range. Figure 4 shows the 8W-25W LED illumination scheme based on the NCP1351 at 90 to 264 Vac input.

In the 8W-25WAC-DCLED lighting application requiring PFC, the input voltage specification is assumed to be 90 to 264Vac, the power factor is higher than 0.9, the energy efficiency is 80%, short circuit and over power protection are provided, and the output current is also 350mA, 700mA and 1A. select. In this type of application, ON Semiconductor's NCP1607 or NCP1608PFC controllers can be used. The NCP1607 is a cost-effective, critical conduction mode (CrM) PFC controller. This device is fully compatible with industry standard pins and simplifies engineer design. Features such as adjustable overvoltage protection (OVP) and open loop protection also enhance design flexibility and robustness. Figure 5 shows the LED lighting application for the NCP1607/NCP1608 at 85 to 135 Vac or 185 to 264 Vac input.

AC-DCLED applications ranging from 50W to 300W are widely used in street lighting and high-power area lighting applications. Different LED driving schemes can be used, assuming an input voltage specification of 90 to 264Vac, a power factor higher than 0.95, and an energy efficiency of 90. %.

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