With the development of LED technology, the application of LED has expanded from the traditional low-power portable product backlight to medium and high power indoor lighting, outdoor lighting and flashlight applications. Depending on the driving power supply, LED lighting can usually be divided into AC-DC LED lighting, DC-DC LED lighting power supply and battery-powered LED flashlights. LED lamps and their power are also available. Different, such as 3 W PAR16, 3×2 W PAR20, 10 W/15 W PAR30, 15 W/22 W PAR38, 1 W G13, 3 W GU10, 1 W MR11, 3 W MR16, 3 W/9 W /15 W recessed light, 1W-3W reading light, etc.
1, AC-DC LED Lighting Solutions ON Semiconductor offers a variety of off-line controllers and power factor correction (PFC) controllers in AC-DC power-operated LED lighting applications, with different isolation and non-isolation requirements. LED application program. 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 100 W, while the LLC half-bridge topology is the preferred solution for high power and energy efficiency.
Figure 1: Isolated topology with different power ranges
In AC-DC LED 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.
Figure 2: Distributed configuration of high-power LED drivers
From the specific power range of the application, the power solution application of AC-DC LED lighting mainly includes:
1 W-8 W: G13/GU10/PAR16/PAR20 lighting
8W -25 W: PAR30/PAR38 lighting
50 W-300 W: area lighting
1) 1 W-8 W AC-DC LED Lighting Applications These applications require an input voltage of 90 to 264 Vac and an 80% efficiency, while providing short-circuit protection, overvoltage protection, and 350 mA, 700 mA. Constant current, application areas include G13, GU10, PAR16, PAR20 and downlight.
ON Semiconductor's NCP1015 self-powered monolithic switching regulator can be used in this type of application. This device integrates a fixed frequency (65/100/130 kHz) current mode controller and a 700 V 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, hopping 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 1 W-8 W range AC-DC LED lighting application. It is worth mentioning that the NCP1015 can also be used in non-isolated (high-frequency transformers in the circuit) 1 W-8 W range AC-DC LED lighting applications. Tapped inductors can be used in the circuit to improve MOSFET operation. Duty cycle and improve system efficiency and circuit performance.
Figure 3: Ansemite 8 W LED driver application circuit diagram (input voltage 85 to 264 Vac)
2) 8 W-25 W AC-DC LED Lighting Applications Power Factor Correction (PFC) is mandatory for any power class specified in the US Department of Energy (DOE) ENERGY STAR® 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 8 W-25 W AC-DC LED lighting application, we consider two cases, one is that the application does not have a 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 90~132 Vac or 180~264Vac (or universal input), 85% efficiency, short-circuit protection and open-circuit protection, and output currents of 350 mA, 700 mA and 1 A constant current, correspondingly using NCP1028 or NCP1351 from ON Semiconductor. Among them, the NCP1028 is an enhanced single-chip switching regulator that is designed to deliver several watts to 15 watts of output power in general-purpose mains input applications. The NCP1028's on-resistance is lower than the NCP101x, providing 800 mA 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 8 W-25 W LED lighting solution based on the NCP1351 at 90 to 264 Vac input.
Figure 4: Schematic diagram of an 8 W to 25 W AC-DC LED lighting application circuit based on the NCP1351.
For 8 W-25 W AC-DC LED lighting applications requiring PFC, the input voltage specification is assumed to be 90 to 264 Vac, the power factor is higher than 0.9, the efficiency is 80%, short-circuit and over-power protection are provided, and the output current is also 350 mA. Different options such as 700 mA and 1 A. In this type of application, ON Semiconductor's NCP1607 or NCP1608 PFC 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.
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 for AC-DC LED applications from 50 W to 300 W are widely used in street lighting and high-power area lighting applications. Different LED drive schemes can be used, assuming their inputs The voltage specification is 90 to 264 Vac, the power factor is higher than 0.95, and the energy efficiency is 90%.
These applications can be adapted to different application requirements using the following different options:
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 a 50 W-150 W AC-DC LED application, either an improved single-stage PFC controller such as the NCP1652 or a NCP1607/8 PFC controller and NCP1377 quasi-resonant (QR) mode PWM can be used. Controller. Among them, the NCP1377 combines a true current mode modulator and demagnetization detector to ensure complete CrM operation under any load/line conditions and to ensure the lowest leakage voltage switching (quasi-resonant operation). The NCP1652 drives signals with programmable dead time and supports active clamping or synchronous rectification to provide optimized energy efficiency. The device also features input undervoltage protection, overvoltage protection, and overcurrent protection to support frequency jitter, skip cycle, and critical conduction mode (CrM)/discontinuous conduction mode (DCM) operation. A schematic of a 50 W-150 W AC-DC LED scheme based on the 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.
AC-DC LED lighting applications with more than 50 W require an energy-efficient LED lighting topology that requires an energy-efficient LED lighting topology, often moving from a flyback topology to a resonant half-bridge topology to take full advantage of zero-voltage switching The advantages of (ZVS) technology. NCP1396 and NCP1901 are energy-efficient 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 the NCP1901 with an input voltage of 90 to 264 Vac and a power of 100 W to 300 W, with the half-bridge operating at a fixed frequency and a fixed duty cycle for reducing Switching loss.
2, DC-DC LED lighting solutions using DC-DC power supply LED lighting applications, common applications include 1 W-3 W MR11/MR16 step-down LED bulb, 1 W-20 W boost LED driver and 20 W- 60 W high power LED driver.
Among them, in the 1 W-3 W DC-DC LED lighting application, ON Semiconductor's CAT4201 step-down LED driver can be used. This device is compatible with 12 V and 24 V systems and provides LED driving current of 350 mA. Driving 7 series LEDs in a 24 V system with up to 94% efficiency. The device features a patented switch control architecture that helps reduce system cost, support CrM operation and improve energy efficiency. The CAT4201 also offers comprehensive protection features such as current limiting, thermal protection and LED open circuit protection. A schematic of the circuit in this 1 W-3 W DC-DC LED application is shown in Figure 8.
And in the DC-DC boost LED application with a power range of 1 W-20 W, you can use ON Semiconductor's NCP3065/6 or NCV3065/6 (automotive application version) buck, boost, single-ended primary inductor converter (SEPIC) and inverter multimode LED driver, and select the boost circuit mode. In addition, ON Semiconductor's NCP1034 synchronous buck PWM controller can be used in DC-DC buck LED applications with power ranges from 20 W to 60 W.
3, LED flashlight drive solution flashlight DC-DC LED lighting solutions include both boost and buck. The NCP1421 step-up DC-DC converter with true shutdown can be used in a 1 W-3 W step-up DC-DC LED flashlight application, while the NCP1529 low-dropout can be used in a 1 W-3 W step-down LED flashlight application. The pressure converter, the application diagram of the two is shown in Figure 9.
Figure 9: LED flashlight boost and buck solution based on NCP1421 and NCP1529
4, summary
ON Semiconductor is the world's leading provider of high performance, energy efficient silicon solutions, offering LED lighting drivers and PFC solutions ranging from 1 to hundreds of watts. Whether using AC-DC power supplies, DC-DC power supplies, or LED lighting drivers for batteries used in LED flashlights, ON Semiconductor can provide customers with the benefits of low cost, cost effectiveness, energy efficiency or the choice of PFC. Required LED lighting driver solution.
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