Simple, economical and robust linear constant current regulation for low current LED applications
With its advantages of energy saving, long service life and rich color combination, LED has become one of the fastest growing semiconductor fields. In recent years, the annual compound growth rate (CAGR) is as high as 20%. It is expected that the global LED market will be even more in 2012. It will reach $11.4 billion and the prospects are very impressive.
Typical LED drivers on the market include two types, linear drivers and switch drivers; and further subdivided, there are three types, switching regulators, linear regulators, and resistive drivers. These three drivers are suitable for different levels of current applications. High-current applications with currents greater than 500 mA use switching regulators because linear drivers are limited to their own structure and cannot provide such large currents. In low-current applications with currents below 200 mA, linear regulators are often used. Resistive drivers; in medium current applications from 200 to 500 mA, either linear regulators or switching regulators are available.
Switching regulators offer high performance and excellent brightness control. The linear regulator structure is simple, easy to design, provides constant current and overcurrent protection, has an external current set point, and has no electromagnetic compatibility (EMC) issues. Resistive drivers use a simple discrete component such as a resistor to limit the LED string current. It is an economical LED driver solution that is equally easy to design and has no EMC issues.
As the world's leading provider of high performance, high performance silicon solutions, ON Semiconductor offers a wide selection of switching regulators and linear regulators for different LED applications. And customers on the market also need a driver that is more economical than switching regulators and common linear regulators, but much more powerful than resistive drivers. In this case, ON Semiconductor is using it. The patented self-biased transistor (SBT) technology, combined with its superior process control capabilities, introduces a new LED driver solution, the Discrete Linear Constant Current Regulator (CCR), which fills this market gap and further Enriched the lineup of ON Semiconductor's broad portfolio of LED drivers.
Low current LED application and driver comparison
The new linear constant current regulators are suitable for low current LED applications from 20 mA to 200 mA. As in automotive applications, the current requirements for combined taillights are typically only tens of milliamps (mA). In addition, in commercial and industrial applications such as billboard text circuits and backlit display cards, the input voltage is typically as high as 30 Vdc and the LED current is between 20 mA and 150 mA. In buildings such as decorative lighting, work lights, landscape lighting, counter lighting, and general lighting applications, the input voltage is typically 12 to 48 Vac or 120/220 Vac, and the LED current is only between 20 and 100 mA. In addition, LEDs such as refrigerators and washing machines also use LEDs for small LCD screen backlights or alternative lighting bulbs. Such applications also require low current LED drivers.
In low-current LED applications, the resistive driver, although low in cost and simple in structure, has a low forward current under low voltage conditions, which causes LED brightness to be insufficient and under transient conditions such as load dump. The LED may be damaged. In addition, this solution requires proper LED coding, high resistance inventory, and low performance.
Compared to resistive drivers, linear constant current regulators provide regulated current, provide constant brightness over a wide voltage range, protect LEDs from overdrive at high input voltages, and provide higher output at low input voltages. brightness. Thanks to its constant current characteristics, customers can reduce or eliminate the coding costs of different LEDs from different suppliers, resulting in lower total system cost.
We can verify the performance comparison of the two drives through actual tests. The test compares the combined taillights implemented with these two drivers, where the CCR is a 25 mA constant current component. At the same 9 V input voltage, the CCR has a higher current than the resistive driver, making the LED brighter. At the same voltage input of 13 V, the brightness is the same. After the voltage is higher than 13 V, the current of the CCR gradually flows to 25 mA, while the current of the resistive driver rises, which may cause the LED to overdrive and damage the LED. In addition, CCR provides a current accuracy of ±10%, which fully meets the application requirements, while the resistance type current accuracy is only ±50%, which is a far cry.
Simple, economical and robust linear constant current regulator based on patented SBT technology
ON Semiconductor's linear constant current regulators are based on ON Semiconductor's patented self-biased transistor (SBT) technology, which provides a degree of integration and combines ON Semiconductor's superior process control capabilities for low currents. Applications provide simple, economical and Robust LED drive solutions.
Specifically, the dual end of this assembly is very easy to design, suitable for high-side and low-side applications, and requires no external components, very simple. Its economy is mainly reflected in eliminating LED coding, reducing inventory costs, and protecting LEDs, reducing replacement and maintenance costs. ON Semiconductor also plans to introduce a linear constant current regulator with three-terminal adjustable output.
It is worth mentioning that ON Semiconductor's linear constant current regulator supports 120/220 Vac power supply. For buildings and general lighting applications, the electrical input after bridge rectification is only required for 120/220 Vac AC. After the input voltage is subtracted from the total voltage of the LED string, the remaining voltage does not exceed the maximum anode-cathode voltage VAK of the linear constant current regulator 45 V. This also shows its easy-to-design features.
In terms of ruggedness, this series of components of ON Semiconductor is very outstanding. For example, it is designed with a negative temperature coefficient (NTC) to protect the LED from thermal runaway at extreme voltages and operating temperatures. For example, the SOT-223 surface mount package measures 7.0 mm x 6.5 mm x 1.6 mm and dissipates 630 mW at 85 °C on a 500 mm long/less than 29 gram copper plate. Ideal for extreme thermal work environments. In addition, these components are certified to the rigorous AEC101 automotive standard for demanding automotive applications. These components also withstand switching transients and voltage spikes and have a good electrostatic discharge (ESD) rated pulse rating of 1.8 kV. In addition, these components are environmentally friendly, use halogen-free mold compounds, and comply with the lead-free RoHS directive.
ON Semiconductor's first NSI45 series of 10 dual-ended linear constant current regulators were introduced in May 2009. These components provide ±10% and ±15% steady-state steady current (Ireg) tolerances with a voltage rating of 45. V, operating temperature range -40 ° C to 85 ° C, maximum junction temperature of 150 ° C, available in 20 mA, 25 mA and 30 mA components, in SOD-123 and SOT223 packages, target markets include automotive and internal applications External LED lighting, xenon lamp replacement for commercial signage applications, traffic signals, etc., and screen backlighting, flat panel AC lighting, work and decorative lights, landscape and outdoor lighting in buildings and general lighting applications.
The main parameters of ON Semiconductor's NSI450 series linear constant current regulators, including dual-ended components such as NSI450XXT1G (SOT123 package, 20/25/30 mA), NSI450XXZT1G (SOT223 package, 25/30 mA), existing samples Available and mass-produced; also available in three-terminal components such as the NSI450XXZT1G (SOT223 package, 30 to 80 mA adjustable) and NSI450XXT1G (D-PAK package, 80 to 150 mA adjustable), will be available in the third quarter of 2009 And mass production in the fourth quarter.
to sum up:
As the world's leading provider of high-performance, high-performance silicon solutions, ON Semiconductor's operational excellence delivers more than 32 billion components per year through manufacturing facilities around the world, with advanced process and technical capabilities. ON Semiconductor is also familiar with its customers, has established extensive and in-depth relationships with a wide range of international and local customers, and serves customers with design support centers around the world. ON Semiconductor's broad portfolio of products and solutions spans standard products, proprietary solutions, proprietary standard products and custom ASIC solutions, as well as automotive, computer and game consoles, portable consumer products, media and entertainment, and industrial Markets for applications such as medical, high-voltage communications, military and aerospace.
All of the above applications in ON Semiconductor's services involve LED lighting/backlighting. And ON Semiconductor uses a wide range of technologies to provide solutions for a wide range of LED lighting applications, leveraging the core strengths of high-performance power solutions. ON Semiconductor's new simple, economical and rugged linear constant current regulator solution for low current LED lighting applications broadens ON Semiconductor's existing LED drivers including switching regulators and common linear regulators The product lineup is ideal for automotive interior/external lighting, commercial signage and building LED lighting applications.
(Editor: Zeng Cong)
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