The next component we must choose is the fly-back diode. This device is necessary for the circuit to work as it re-circulates the inductor stored energy during the OFF period into the LED. For the best efficiency, a Schottky diode should be used as these have a lower forward volt drop than a normal silicon diode. For normal ambient temperatures of up to 85 centigrade, a Zetex ZHSC1000 is a suitable 1 A 40 V device. When the control electronics are in an extremely high temperature environment, which may occur if a number of LEDs are mounted on the same PCB close to the control electronics, a low leakage Schottky diode should be used, such as the Zetex ZLLS1000. All Schottky diodes have a reverse leakage current which increases as the junction temperature rises. This leakage current is multiplied by the supply voltage to produce a power loss in the diode. This adds to the overall heating on the diode which increases the leakage current further increasing the power dissipated. This thermal runaway can result in the destruction of the device. If in doubt, use a low leakage device.