Driver selection for different DC-DC LED lighting applications

In recent years, the application areas of high-brightness LEDs have continued to increase, covering a range from mobile device backlighting, medium and large-sized LCD backlighting, automotive interior and exterior lighting to general lighting. Common DC-DC LED lighting applications include landscape lighting, internal low-voltage road lighting, solar-powered lighting, automotive lighting, emergency vehicle lighting, marine applications, low-voltage halogen replacement, and aircraft interior lighting. This article will focus on how to select the appropriate ON Semiconductor high-efficiency driver solution for different DC-DC LED lighting applications.

　　LED DC-DC Switching Regulator Topology

　　According to the relationship between input voltage and output voltage, we can divide the topology of LED DC-DC switching regulator into the following types:

　　Buck: Suitable for applications where the minimum input voltage is always higher than the maximum voltage of the LED string under all operating conditions. For example, this topology is used when driving a single 1 W LED from a 12 V supply.

　　Boost: Suitable for applications where the maximum input voltage is always lower than the minimum voltage of the LED string under all operating conditions. For example, this topology is used when driving 6 LEDs with a 5 V supply.

　　Buck-boost, or single-ended primary inductor converter (SEPIC): Suitable for applications where the input voltage and output voltage overlap. For example, this topology can be used when driving four LEDs from a 12 V car battery.

　　Different topologies are suitable for different LED driver solutions. As a leading high-performance silicon solution provider for energy-efficient electronic products, ON Semiconductor uses its expertise and knowledge in power management to provide a wide range of energy-efficient driver solutions for various LED lighting applications, including various energy-efficient DC-DC LED lighting solutions.

　　LED DC-DC buck driver solution

　　Typical LED DC-DC buck applications are high-brightness modular light strips used in trough lights, bookshelf lights, and display cabinet lights. Each strip (11.5 x 1 inch) generally has 4 LEDs, with a luminous efficacy of 23 to 47 lm/W depending on the color, and a voltage of 23 to 25 V.

　　Depending on the frequency and current, different LED DC-DC buck driver solutions provided by ON Semiconductor can be used in such applications, including NCL30100 controller, CAT4201 regulator, and NCP3065/NCV3065, NCP3066/NCV3066 regulators and controllers that can be configured as buck regulators (see Figure 1). Each of these solutions has its own characteristics.

　　For example, the NCL30100, as a controller, does not integrate FETs itself, but it supports the use of cost-effective N-channel MOSFETs as external components, can regulate current, and works at 100% duty cycle. However, the supply voltage (VCC) of this component can reach 18 V, and external components are required to support higher voltages and are required for a certain number of LED designs. The NCL30100 is suitable for applications such as MR16 bulbs, 12 V landscape lighting, solar-powered LED lighting, linear lighting, and billboard text circuits and sign backlighting.

　　CAT4201 is a complete power converter that integrates MOSFET switches. It uses a small TSOT5 package with a maximum voltage of 36 Vdc (can withstand 40 V transient voltage). It can drive 7 serial LEDs with a total voltage of 32 V. The power efficiency is as high as 94%, and it provides current limiting and thermal protection. However, this component requires output capacitors in most applications, and the LED output current is limited to a maximum of 350 mA. CAT4201 is suitable for applications such as 12 V and 24 V lighting systems, automotive and aircraft lighting, and general lighting.

　　NCP3065 and NCP3066, as well as the corresponding automotive-certified versions NCV3065 and NCV3066, are flexible switching regulators that can be configured as buck, boost, and buck-boost. When configured as an LED buck regulator, it can operate without the use of large output capacitors, supports +40 V/1.5 A typical peak switch current, can be set to 350 mA, 700 mA and 1,000 mA, and can also meet dimming requirements. NCP3065/6, NCV3065/6 are suitable for automotive and marine lighting, high-power LED drivers, constant current sources, low-voltage LED lighting (landscape, road, solar and MR16 replacement) and other applications.

　　LED DC-DC Boost Driver Solution

　　As mentioned above, NCP3065/6 and NCV3065/6 can be configured in different structures. The right side of Figure 4 shows an application circuit diagram configured in a boost structure.

　　In addition, ON Semiconductor will also launch the NCL30131 LED boost driver specifically for high-efficiency boost mode, suitable for driving long strings of high-brightness LEDs. The NCL30131 is a switching boost controller that can use N-channel FETs and can be used to build high-efficiency LED boost drivers. This component uses a voltage-mode pulse width modulation (PWM) feedback mechanism with an operational transconductance amplifier (OTA). This component has high drive capability and can drive high-current/high-efficiency MOSFETs. The input voltage range is extremely wide, ranging from 4.5 V to 28 V. The NCL30131 provides 300/600/1,000 kHz switching frequencies and provides rich protection functions such as programmable current limiting, short-circuit protection, thermal shutdown, overvoltage protection, and undervoltage lockout, suitable for applications such as MR16 building lighting, light bars, landscape lighting, and in-cabinet lighting.

　　Figure 5: Typical circuit diagram of the NCL30131 high-efficiency boost LED driver.

　　The +12 Vin @ ~700 mA demonstration board built based on NCL30131 driving 10 high-brightness LEDs has shown an energy efficiency of over 90% and a line voltage regulation accuracy of less than 0.2%.

　　In addition to the NCL30131, ON Semiconductor also offers another LED DC-DC boost converter, the CAT4240. This component operates at a fixed switching frequency of 1 MHz, enabling the use of small-value external ceramic capacitors and inductors. The high-voltage output stage of this component is ideal for driving medium- and large-size panel displays containing up to 10 serial white LEDs, with an efficiency of up to 94%.

　　LED DC-DC Buck-Boost Driver Solution

　　Typical LED buck-boost applications include driving a module containing 3 to 4 LEDs with a 12 V AC or 12 V DC power supply. In this application, the NCP3065/6 controller configured in a buck-boost topology can be used to meet the application requirements where the input voltage and output voltage overlap. Figure 6 shows the circuit diagram of the NCP3065 in such an application.

　　Figure 6: NCP3065 LED buck-boost application circuit diagram.

　　GreenPoint® Online Design Simulation Tool Accelerates DC-DC LED Lighting Design

　　As a leading supplier of high-performance silicon solutions for energy-efficient electronic products, ON Semiconductor provides complete system solutions for various LED lighting applications (including DC-DC LED lighting applications), including power supplies, communications, light sensors, MOSFETs, rectifiers, protection, filters and thermal management products.

　　In addition, to help designers speed up LED lighting design, ON Semiconductor also provides the GreenPoint® online design simulation tool, which allows designers to sit at their workbench and easily go through several steps such as "selecting LED drivers", "determining design requirements", "automatically generating design circuit diagrams", "simulating and verifying", "generating bills of materials and reports", "downloading reports as PDF files" and "saving and sharing disk files", which can greatly shorten development time and speed up product launch.

　　This online design tool currently supports the application design of a number of ON Semiconductor's high-efficiency LED driver products, including the DC-DC LED drivers NCP3065, NCP3066, NCL30100, CAT4201, NCP1529 (buck solution), NCP5030 (buck-boost solution) and NCP5050 (boost solution). More products will be supported in the future.

　　Figure 7: ON Semiconductor GreenPoint® online design tool helps accelerate LED lighting design.

　　Summarize

　　As the leading high-performance silicon solution provider for energy-efficient electronic products, ON Semiconductor provides different energy-efficient DC-DC LED lighting products, which are convenient for users to choose according to application requirements. ON Semiconductor also provides online simulation design tools, demonstration boards and multiple reference designs to help customers simplify design bidding and use. The design of ON Semiconductor LED driver products continues to trend towards small size, high energy efficiency and low cost, helping to drive the LED lighting market forward.