LED lighting driver solutions for different power supplies and different power levels

1. AC-DC LED lighting solutions

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

Figure 1 : Isolation topologies in different power ranges

In AC-DC LED lighting applications, low-power LED applications are usually driven by constant current (CC), while the constant voltage (CV) function is used as a protection function when the output is open. High-power LED applications may require the addition of power factor correction (PFC) to the circuit, in which the AC-DC conversion and LED drive circuits may be configured in an integral manner, that is, the two are integrated together and are located in the lighting fixture, or in a distributed configuration, as shown in Figure 2, thereby simplifying safety considerations and increasing system flexibility.

From the specific power range of the application, the power supply solution applications of AC-DC LED lighting mainly include:

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

8W -25W: PAR30/PAR38 lighting

50W-300W: Area lighting

1) 1 W-8 W AC-DC LED lighting applications

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

ON Semiconductor's NCP1015 self-powered monolithic switching regulator can be used in such applications. This device integrates a fixed frequency (65/100/130 kHz) current mode controller and a 700 V high-voltage MOSFET, providing all the features required to build a robust, low-cost power supply, such as soft start, frequency jitter, short-circuit protection, cycle skipping, maximum peak current set point, and dynamic self-powered function (no auxiliary winding required). Figure 3 shows the circuit diagram of the NCP1015 in an isolated 1 W-8 W range AC-DC LED lighting application. It is worth mentioning that the NCP1015 can also be used in non-isolated (no high-frequency transformer in the circuit) 1 W-8 W range AC-DC LED 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 : ON Semiconductor 8 W LED driver application circuit schematic (input voltage 85 to 264 Vac)

2) 8W-25W AC-DC LED lighting applications

The U.S. Department of Energy (DOE) ENERGYSTAR™ solid-state lighting (SSL) specification stipulates that any power level must provide power factor correction (PFC). This standard applies to a series of specific products, such as recessed lights, cabinet lights and table lamps, among which the power factor of LED drivers for residential applications must be greater than 0.7, and greater than 0.9 for commercial applications. However, this standard is a voluntary standard, which means that you can choose not to comply or comply.

Accordingly, in 8W-25W AC-DC LED lighting applications, we consider two situations, one is that the application has no power factor requirement, that is, no PFC controller is required, and the other is that a PFC controller is required. In applications that do not require PFC, we assume that the input voltage specification is 90~132Vac or 180~264Vac (or universal input), the energy efficiency is 85%, and protection features such as short-circuit protection and open-circuit protection are provided. The output current is 350mA, 700mA and 1A constant current. Accordingly, ON Semiconductor's NCP1028 or NCP1351 can be used. Among them, NCP1028 is an enhanced monolithic switching regulator suitable for providing output power from several watts to 15W in applications with universal main power input. NCP1028 has lower on-resistance than NCP101x, provides 800mA peak current, has many features of NCP101x, and also provides 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 suitable for cost-critical low-power offline flyback switching power supply applications. The device supports frequency retracement and also features latch input, natural frequency jitter, negative current sensing, and an extended supply voltage range. Figure 4 shows an 8 W-25 W LED lighting solution based on the NCP1351 under 90 to 264 Vac input conditions.

Figure 4 : Schematic diagram of an 8 W to 25 W AC-DC LED lighting application based on the NCP1351.

In 8 W-25 W AC-DC LED lighting applications that require PFC, it is assumed that the input voltage specification is 90 to 264 Vac, 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 available in different options such as 350 mA, 700 mA and 1 A. In such applications, ON Semiconductor's NCP1607 or NCP1608 PFC controllers can be used. NCP1607 is a cost-effective critical conduction mode (CrM) PFC controller. This device is fully compatible with industry standard pins, simplifying engineers' designs. Functions such as adjustable overvoltage protection (OVP) and loop open circuit protection also enhance design flexibility and robustness. Figure 5 shows the LED lighting application solution of NCP1607/NCP1608 under 85 to 135 Vac or 185 to 264 Vac input conditions.

Figure 5 : Schematic diagram of 8 W-25 W AC-DC LED lighting application based on NCP1607/8 PFC controller

3) AC-DC LED lighting applications with power above 50 W

In AC-DC LED applications with power ranging from 50 W to 300 W, which are widely used in street lighting and high-power area lighting applications, different LED driving schemes can be adopted, assuming that the input voltage specification is 90 to 264 Vac, the power factor is higher than 0.95, and the energy efficiency is 90%.

This type of application can adopt the following different solutions to suit different application requirements:

NCP1652: Improved single-stage PFC

NCP1607/8+NCP1377: Critical conduction mode PFC+quasi-resonant current mode PWM

NCP1607/8+NCP1396: Critical conduction mode PFC+half-bridge resonant LLC

NCP1901: The latest two-stage (PFC + higher efficiency half-bridge resonant LLC)

For example, in 50 W-150 W AC-DC LED applications, either an improved single-stage PFC controller such as NCP1652 can be used, or a combination of NCP1607/8 PFC controller and NCP1377 quasi-resonant (QR) mode PWM controller can be used. Among them, NCP1377 combines a true current mode modulator and a demagnetization detector to ensure full CrM operation under any load/line conditions and ensure the lowest leakage voltage switch (quasi-resonant operation). NCP1652 drives a signal with programmable dead time, supports active clamping or synchronous rectification, and provides optimized energy efficiency. This device also has protection features such as input undervoltage protection, overvoltage protection, and overcurrent protection, and supports frequency jitter, cycle skipping, and critical conduction mode (CrM)/discontinuous conduction mode (DCM) operation. The schematic diagram of a 50 W-150 W AC-DC LED solution based on NCP1652 with 85 to 135 Vac or 185 to 264 Vac input is shown in Figure 6.

Figure 6 : 50 W-150 W AC-DC LED solution based on the NCP1652 single-stage PFC controller.

If AC-DC LED lighting applications with power above 50 W require a more energy-efficient LED power supply, a high-efficiency LED lighting topology is required, which often shifts from a flyback topology to a resonant half-bridge topology to give full play to the advantages of zero voltage switching (ZVS) technology. Both NCP1396 and NCP1901 are high-efficiency half-bridge resonant solutions for LED power supplies developed by ON Semiconductor. Figure 7 shows the latest PFC+ resonant half-bridge LED driver solution based on NCP1901, with an input voltage of 90 to 264 Vac and a power of 100 W to 300 W, in which the half-bridge section operates at a fixed frequency and a fixed duty cycle to reduce switching losses.

Figure 7 : 100W-300W AC-DC LED lighting solution based on NCP1901

2. DC -DC LED lighting solution

Common specific applications in LED lighting applications powered by DC-DC power supplies include 1 W-3 W MR11/MR16 buck LED bulbs, 1 W-20 W boost LED drivers, and 20 W-60 W high-power LED drivers.

Among them, in 1 W-3 W DC-DC LED lighting applications, ON Semiconductor's CAT4201 buck LED driver can be used. This device is compatible with 12 V and 24 V systems, provides up to 350 mA of LED drive current, and can drive 7 series LEDs in a 24 V system with an energy efficiency of up to 94%. This device uses a patented switch control architecture to help reduce system costs, support CrM operation and improve energy efficiency. CAT4201 also provides comprehensive protection features such as current limiting, thermal protection and LED open circuit protection. The circuit diagram of this device in 1 W-3 W DC-DC LED applications is shown in Figure 8.

Figure 8 : 1 W-3 W DC-DC LED solution based on CAT4201.

In the DC-DC boost LED application with a power range of 1 W-20 W, ON Semiconductor's NCP3065/6 or NCV3065/6 (automotive version) buck, boost, single-ended primary inductor converter (SEPIC) and inverter multi-mode LED driver can be used, and the boost circuit mode can be selected. In addition, ON Semiconductor's NCP1034 synchronous buck PWM controller can be used in DC-DC buck LED applications with a power range of 20 W-60 W.

3. LED flashlight driving solution

Flashlight DC-DC LED lighting solutions include boost and buck types. The NCP1421 boost DC-DC converter with true shutdown function can be used in 1W-3W boost DC-DC LED flashlight applications, while the NCP1529 low-voltage buck converter can be used in 1W-3W buck LED flashlight applications. The application diagrams of the two are shown in Figure 9.

Figure 9 : LED flashlight boost and buck solutions based on NCP1421 and NCP1529

4. Summary

ON Semiconductor is the world's leading supplier of high-performance, energy-efficient silicon solutions, providing LED lighting drivers and PFC solutions covering a power range of 1 to hundreds of watts. Whether it is an LED lighting driver using an AC-DC power supply, a DC-DC power supply, or a battery used in an LED flashlight, ON Semiconductor can provide customers with LED lighting driver solutions with different requirements for low cost, high cost performance, high energy efficiency, or whether PFC is required.