In many lighting applications, linear LED drivers are the preferred solution because they are relatively simple, easy to design, and allow the LED to be driven with an accurate steady current regardless of the LED forward voltage drop (Vf) or input voltage . Because the drivers are linear, they must match the power dissipation requirements of the application. ON Semiconductor offers a wide range of linear LED driver solutions with a current range of 10 mA to 1 A, including novel linear constant current stabilizer (CCR) solutions and many other linear driver solutions.
Linear CCR for low current LED drive and application examples
In many low-current LED applications with currents below 350 mA, such as automobile combination taillights, neon lamp replacements, traffic lights, large display backlights, building decorative lights and indicators, etc., ordinary linear regulators or Resistor to provide LED driving scheme. The resistor is used to limit the current of the LED string, is the lowest cost solution, easy to design, and has no electromagnetic compatibility issues. However, when using resistors, the LED forward current is determined by the voltage. Under low voltage conditions, the forward current is low, which will lead to insufficient brightness of the LED, and under transient conditions such as load dump, the LED may be damaged. The energy efficiency of the resistance scheme is also the lowest, which is not conducive to energy saving, which is particularly disadvantageous in applications that emphasize high and low energy consumption. In addition, the resistance scheme also has LED thermal runaway and screening problems. The linear regulator solution provides better steady-current accuracy (± 2%), supports over-power self-regulation, and has no EMI problems. The energy efficiency of this scheme is low and the cost is moderate.
Customers need a driving solution that is more economical than ordinary linear regulators, but much higher in performance than resistance. ON Semiconductor uses patent pending self-biased transistor (SBT) technology, combined with its own strong process control capabilities, to launch a novel LED drive solution-NSI45 series linear constant current stabilizer (CCR). Compared with a resistor, a linear CCR has a constant brightness over a wide voltage range. It protects the LED at high input voltages from overdriving and provides higher brightness at low input voltages. Thanks to its constant current characteristics, customers can reduce or eliminate the coding cost of different LEDs provided by different suppliers, reducing the total cost of the system. CCR also has no EMI problems, uses high power density packaging, and has passed the AEC-Q101 certification for the automotive industry.
ON Semiconductor's CCR includes two types of fixed-end output and three-end adjustable output. The current levels range from 10 to 350 mA and 20 to 160 mA. The anode-cathode maximum voltage VAK is 50 V and 45 V respectively. The high VAK voltage helps suppress surges and protect LEDs. This series of CCR has no voltage shift before current flow, and its fast on / off feature provides a wide range and accurate pulse width modulation (PWM) dimming capability. There is no "plug and play" component on the market like CCR. Other components require a minimum voltage of 0.5 V to turn on, instead of turning on immediately like CCR (see Figure 1 left). CCR can provide accurate PWM dimming with an external bipolar junction transistor (BJT) (see Figure 1 right). The typical PWM dimming frequency is 0.1 to 3 kHz. There is no color drift during the dimming process, because the LED always Best current conduction.
Figure 1: ICR-Vin curve comparison of 25 mA CCR and competing components (left); CCR dimming application example (right).
CCR has a negative temperature coefficient (NTC) function to protect the LED from thermal runaway at extreme voltages and operating temperatures. CCR is easy to design, suitable for high-side and low-side applications (see Figure 2a), requires no external components, is very simple, and is suitable for a wider range of applications; in comparison, some suppliers provide Similar function or performance to ON Semiconductor CCR, but requires additional external components, cannot be configured as high-end or low-end drivers, different packages, or poor thermal reliability.
Figure 2: CCR can be flexibly used for high-end or low-end drive, and can also drive multiple strings of LEDs.
CCR can also be used to drive multiple strings of LEDs (see Figures 2b and 2c), which can also be used for both high-end and low-end. Figure 2b shows an application example of a single CCR driving multiple strings of LEDs. This configuration has the lowest cost, but the forward voltage drop of different LEDs must match, and the current of other strings of LEDs increases when a certain string of LEDs fails, increasing the risk of failure. . In this configuration, more power is dissipated in a single CCR package. Figure 2c shows that multiple CCRs drive multiple strings of LEDs. This configuration has the best protection performance. It does not require matching LEDs. A string of LED failures has no effect on other strings, and power is dissipated in multiple CCR packages.
In addition to driving a single string or multiple strings of LEDs with a single CCR, multiple CCRs can be connected in parallel to provide greater current and drive single or multiple strings of LEDs. Among them, the use of three-terminal adjustable output CCR helps meet specific current setting requirements, and the adjustable resistor consumes less than 150 mW.
Figure 3: Multiple CCRs are connected in parallel to provide more current and drive a single string or multiple strings of LEDs.
CCR can be used in applications that use AC power directly. After the AC mains input is bridge-rectified, it only needs to ensure that the input voltage minus the total voltage of the LED string does not exceed the VAK of the CCR. CCR can also be used for T8 fluorescent tube LED replacement applications. CCR is used to drive LED T8 lamps (see Figure 4). Compared with fluorescent lamps using electronic ballasts, the input power is lower, the power factor is higher, the total ripple distortion is lower, and the light output is higher.
Figure 4: Circuit diagram of NSI45090DDT4G CCR in driving LED T8 tube application.
ON Semiconductor's NSI45 series CCR includes fixed output versions of 10, 15, 20, 25, or 30 mA, adjustable output versions of 60 to 160 mA, and adjustable output versions of 20 to 160 mA certified by the automotive standard. ON Semiconductor also provides CCR sample kits and evaluation boards for customers to apply for trial.
As APPLE offical recognize change and remove new iPhone 6 Battery Pack will make your iPhone devices going faster than before.Remember, this isn`t just about improving iPhone 6 Battery life; some tests have found replacing iPhone 6 new battery can result in speed improvements of over 100 percent.
iPhone 6 Battery Pack
Nominal voltage: 3.82V
Limited charge voltage: 4.35V
Capacity:1810mAh (6.91whr)
Cell size: 33x39x96mm
iPhone 6 Power and battey: Built-in rechargeable lithium-ion battery Charging via USB to computer system or power adapter Talk time: Up to 14 hours on 3G Internet use: Up to 10 hours on 3G, up to 10 hours on LTE, up to 11 hours on Wi‑Fi HD video playback: Up to 11 hours Audio playback: Up to 50 hours Standby time: Up to 10 days
iPhone 6 Battery
iPhone 6 Battery Pack,Battery Pack For iPhone 6,iPhone 5S Battery Pack Replacement,iPhone 6 Lithium-Ion Battery
Shenzhen Aokal Technology Co., Ltd. , https://www.aokal.com