After the use of the technology of LED into the LED Flashlight, this kind of technology is applied into many aspects such as the lighting in the car and outside the car. In fact, this is a necessary application. Car is becoming more and more common in our daily life. The lighting technology should be improved to meet the need of users.
External signal lights, tail lights and headlamps on the car require the highest power of the DC / DC LED driver, because the brightness of the LED lights is used most, so the numbers are up. Although the light is based on the steady flow of heat and restrictions, a very bright LED headlamp is also rare. Driving high-power LED series amber and red, fine-tuning for the interior lighting and lighting to bring the same challenge, the difficulty of the challenge is different. High dimming ratio is not necessary, but a simple on / off and high / low brightness function is useful. LED series car battery voltage often exceeds the voltage range, and therefore need to have a buck and boost, or buck-boost LED driver functionality.
This application shows the LT3477 buck LED driver to drive two high-power 1A current LED. The two LED without the ground as the base, connecting the two terminals are generally the converter output and battery input. LT3477 has two unique, and a floating current sensing 100mV input pin. This pin connected in parallel with the LED multi-string, and not to ground-based current-sensing resistor. In the LED Flashlight, this is potential.
They work in the automotive battery voltage range, and below this range, the current situation can be up to 1A to achieve accurate LED steady flow. LT3477′s shutdown pin is used to achieve the lamp on / off function, and when not in use the input current to 1uA (typically 100nA). IADJ pin is used for the brake light and taillight applications such as signal lights or brake lights, back-end such as to achieve greater than 10:1 analog dimming ratio, such applications do not need true color PWM dimming.
Using high-power LED Driver LTC3783 buck-boost architecture, the application of the drive is used for automotive taillights 6-10 3W red LED. External switching MOSFET current sensing resistor and switching to high power and high voltage LED driver designed to provide maximum design flexibility. If the battery voltage drops below 9V, the 9V to 36V input and 1.5A in the current when the LED in series up to 25V output will need to switch 100V rated voltage. It is higher than the peak switch current of 8A capacity. In the automotive battery voltage range, 1.5A constant current battery is good and stable. In fact, the technology in both taillights and LED Flashlight is the same.