LED driver circuit diagram powered by solar cells

This figure shows the application of an LED driver powered by a solar cell to an LED emergency flashlight. When the flashlight is turned off, the LTC3536 is in shutdown mode. Its quiescent current of less than 1μA minimizes supercapacitor power consumption when ambient light is no longer available. When the LED flashlight is turned on, the LTC3536 turns on through the SHDN pin to provide a constant load current of 105mA to the LED. The LTC3536 regulates output and LED current to provide 14 minutes of reliable lighting with the supercapacitor charged up to 5V. This guaranteed lighting time of 14 minutes can be extended by increasing the value of the supercapacitor or using a battery with suitable charge control.