AC-DC LED driver solution for LED general lighting challenges

General Lighting design engineers face many challenges such as power density, power factor correction (PFC), space limitations, and reliability. These LED lighting design challenges are similar to power supply design challenges. Specifically, LED general lighting has several challenges: because of the effects of total effecacy and thermal limitations, even low-power applications are important; in many cases Lower power also requires power factor correction and harmonic processing; in space-constrained applications, especially when replacing bulb applications, the drive power density is critical; overall power reliability is important to improve overall lamp life. The wide input supply voltage range should support up to 277 Vac; compatible with traditional lighting requirements such as TRIAC dimming. In addition, LED general lighting is also subject to evolving standards and safety regulations, such as the US Energy Star and the European Commission's International Electrotechnical Commission (IEC) requirements.

ON Semiconductor has been providing a wide range of solutions for LED lighting, introducing a variety of products that meet the latest LED lighting standards, including AC-DC power ICs, DC-DC drivers, CCR stabilizers, constant current and constant voltage (CCCV). Control, high voltage FET, rectifier, digital interface, ambient light sensor, protection, power line communication (PLC) modem and more. This article mainly introduces AC-DC power supply configuration and related circuits for LED lighting, helping engineers to meet the above challenges and design products that meet general lighting requirements.

ON Semiconductor LED Lighting Solutions

　　 Figure 1 shows the types of products that are available from ON Semiconductor for general LED lighting.

Figure 1: Application diagram of ON Semiconductor's LED lighting solution

In ON Semiconductor's AC-DC power supply configuration for LED lighting, NCP1010~NCP1015 is recommended for lighting applications from 1 to 10 W, and NCP1027/8 is available for 1 to 15 W. These solutions incorporate MOS transistors for isolation. And non-isolated applications, support secondary PWM dimming, analog dimming or dual brightness level dimming, energy efficiency up to 75-80%; 1 to 30 W applications can use LV5026, 5027, 5028, support isolation scheme, typical energy efficiency 85 About 1%; 1 to 40 W recommended to use NCL30000, can be used for primary controllable dimming, suitable for isolation and non-isolation scheme, isolation scheme energy efficiency 80-85%. The 40 to 150 W is recommended for the NCL30001, which is a continuous conduction mode (CCM) control chip. The typical energy efficiency of the isolation scheme is 85-90%; the NCL30051 is recommended for higher power. Figure 2 is a comparison of output power and energy efficiency of these schemes. The functions and features of these solutions are described in detail below.

Figure 2: Comparison of output power and efficiency of AC-DC power supply configuration for LED lighting

LV5026/27/28 Series LED Controller for 1 to 30 W Power AC-DC Applications

The series is the LED controllers of Sanyo Semiconductor, the LV5026M, LV5028TT and LV5027T, which are members of ON Semiconductor. The LV5026M has TRIAC dimming, PWM dimming, analog dimming and power factor correction. The LV5028TT has only TRIAC dimming and power factor. Correction function. The LV5026/7/8 TRIAC dimming circuit is shown in Figure 3.

Figure 3: LV5026/7/8 TRIAC dimming circuit

Take the most functional LV5026M as an example. It is a high-voltage LED controller compatible with different dimming. The dimming mode is TRIAC, analog input or PWM input. The switching frequency (50 kHz, open circuit 70 kHz) can be selected. The solution is a low-noise switching system that uses a 5-band skip mode frequency to step-drive the switch; its reference voltage is selectable (internal 0.605 V and external input voltage) with soft-start and TRIAC stabilization.

The PWM control architecture designed to reduce electromagnetic interference (EMI) has advantages over competing products. It uses a 2-step drive to significantly reduce noise; five levels of frequency in a non-constant period effectively eliminate EMI peaks.

There are two ways to convert low-power AC-DC LED power, one is non-isolated buck, requires mechanical insulation; its design and circuit configuration are simple, the board size is small, the number of components is small, the energy efficiency is high, bill of materials (BOM) The cost is also lower. The other is isolated return, using electrical (magnetic) isolation, easy to meet safety requirements, magnetic design is more complex, suitable for higher power design, requires a larger board size.

LV5026/7/8 is used for non-isolated A19 LED lamps, which can realize the following product features: step-gate driving method, oscillation frequency rotation function, high-gate capability drive circuit, externally adjustable reference voltage, support for multiple dimmers (TRIAC dimming, digital dimming, and analog dimming); soft start, overcurrent protection, thermal shutdown, overvoltage protection, etc. are also supported. The LV5027M/LV5028M is a simplified version of the LV5026M with fewer external components.

Figure 4: LV5026/7/8 for non-isolated A19 LED lights

Low-power step-down solution for high-efficiency and space-constrained applications NCL30100

The NCL30100 is an energy-efficient, peak-current-controlled, self-regulating, fixed-time-down buck controller for low-power, space-constrained applications where space and energy efficiency are critical, such as MR16 LEDs. The scheme has an adjustable oscillation frequency characteristic. The continuous conduction mode (CCM) eliminates the output capacitance, provides higher energy efficiency, and provides natural LED open circuit protection. The NCL30100 utilizes negative current sensing to reduce power loss with a small inductor for low cost, high energy efficiency (100 Vac Vo = 36 V, energy efficiency > 90%) and low component count.

Figure 5: Single Voltage Input Buck Solution NCL30100

Low power offline step-down solution NCP1015

The NCP1015 monolithic switching power supply IC can meet the AC 85-265 Vac wide voltage input range and is suitable for low power off-line buck LED lighting design with output power within 10 W. This component offers a wide range of features such as soft start, frequency jitter, short circuit protection, skip cycle, maximum peak current setting and dynamic self-powered (DSS) to enhance energy efficiency and enhance reliability. Adding a resistor between C8 and IC's 1st pin improves energy efficiency and is suitable for small current and high voltage output.

Figure 6: NCP1015 Buck Solution

Medium and low power AC-DC solution NCL30000 for buck and buck-boost configurations

Two configurations can be selected using the NCL30000's “Average Current Stabilization” topology, one for the buck configuration (including the tapped inductor buck configuration). The inductor is connected in series with the LED string. Current flows only when the input voltage is greater than the output voltage drop. The power factor (PF) and input current total harmonic distortion (THDi%) performance depends on the ratio of the output voltage drop to the input voltage (VF/). Vin), the higher the ratio, the lower the PF, the higher the ratio, the higher the THDi.

The other is a buck-boost configuration. The inductor is not in series with the LED string. The input current waveform or distortion is independent of the output voltage drop. The inherent LED fault protection provides protection when the MOSFET is shorted; the LED forward voltage drop can be higher than Or lower than the input voltage; the MOSFET switching voltage stress is the sum of the input voltage and the output voltage drop (Vin+Vout).

The working principle of the buck topology is that current flows only when the input voltage exceeds the forward voltage drop (VF) of the LED; the high conduction factor is provided by the critical conduction mode (CrM) and constant on-time operation; the LED can be directly sensed. Current; low loop bandwidth supports high power factor operation; MOSFET current is equal to LED peak current; MOSFET voltage stress is equal to peak line voltage.

Figure 7 is the NCL30000 high power factor step-down solution application circuit, which can adjust the maximum on-time according to the line and load power when the line is dimmable; compatible TRIAC or trailing edge (transistor) dimmer; dedicated to one For line voltage (120 Vac or 230 Vac), phase-cut dimming optimizes EMI filter design, reduces X-capacitance values, and minimizes peak current.

Figure 7: NCL30000 High Power Factor Buck Solution Application Circuit

The following is an example of two AC-DC isolated power configurations based on the NCL30000.

1) AC dimmable A19 LED lamp with thermal back-off: input voltage is 90 to 135 Vac, 5 W rated output power (10 V @ 500 mA), can drive 3 series LEDs; isolated heat reverse, temperature Linearly reduces the output current when rising; power factor >0.96, energy efficiency >77%; for the "Energy Star" version 1.1 integral LED lamp requirements; compatible TRIAC and transistor dimmer.

Figure 8: Heat reverse AC dimmable A19 LED light

2) AC dimmable PAR30 LED lamp: can be used for input voltage 115 V/230 V lamp, 11 W rated output power (24.5 V @ 450 mA), drive 8 LEDs connected in series / 3 series and parallel; isolated; power Factor >0.96, energy efficiency >83%, for the "Energy Star" version 1.1 integral LED lamp requirements; compatible TRIAC and transistor dimmer.

Figure 9: AC dimmable PAR30 LED light

NCL30001 solution for medium to high power AC-DC LED lighting applications

The NCL30001 Power Factor Correction (PFC) dimmable LED driver is suitable for medium to high power applications (up to 90 W), such as building decorative light. There are three ways to support dimming: 1-10 V analog voltage input (1 V = minimum, 10 V is 100% on); two-level bi-level analog dimming; and PWM dimming (dimming) Frequency range 350 Hz to 3 kHz, dimming range > 10:1). Protection features include: open circuit and short circuit protection, over temperature protection, over current protection, over voltage protection and over temperature protection.

Figure 10: NCL30001 for building decorative light

NCL30051 solution for decorative light applications in high-power buildings

The NCL30051 is a dedicated LED power integrated circuit (IC) that provides a constant voltage for step-down DC-DC converters/LED drivers such as the NCL30160. This component incorporates a critical conduction mode (CrM) PFC controller and a half-bridge resonant controller with a built-in 600 V driver optimized for off-line power applications with all the energy-efficient, small form factor design required characteristic. The NCL30051 can be used in building decorative light applications up to 100 W, with up to 250 W power under modified component conditions. The NCL30051 supports dimming methods including 1-10 V analog voltage input (1 V = minimum, 10 V is 100% on), two-level bi-level analog dimming, and PWM dimming (frequency range 100) Up to 300 Hz, dimming range >10:1). Protection features include: open circuit and short circuit protection, over temperature protection, over current protection, and over voltage protection.

Figure 11: NCL30051 for high power building decorative light

In addition, ON Semiconductor's GreenPoint® design simulation tool allows designers to select products, determine design requirements, automate design (circuit diagrams), simulation and verification, bill of materials (BOM) and reports, downloads in just a few steps The report is a series of processes such as PDF file, save disk and sharing, so as to realize fast, easy to use and efficient LED product development.

to sum up

Using its core expertise and strengths in energy-efficient power supplies and packaging, ON Semiconductor offers control and drive components for LED lighting applications, especially general lighting, that meet a variety of regulatory requirements. These solutions use a unique LED driver power architecture, analog and dimming technology, flyback converters and non-isolated topologies to provide a wide range of applications for a wide range of general lighting applications.

Edit: Sophy