# Reverse recovery time of Schottky diodes

I am considering redesigning a IR2110-based H-bridge driver with 1N5819 because UF4007 he called for is, strangely, not available from local suppliers. I understand that the author chose it for its fast speed, but I am wondering whether Schottky diodes are faster.

I have no intention running this circuit anywhere over 20V. It draws power from a car battery, or perhaps a running car.

Here is the circuit I am modifying:

The same speed issue exists in the body diode of IRF540 power MOSFET I chose to use. Transformers have flyback issues and the same switching frequency is also applied to the switching MOSFETs' body diodes as well. Will a MBR1045 power Schottky diode help?

Not quite in topic, if I replace the bootstrap cap C1 with a MLCC (47uF ceramic caps in 1206 and 0603 sizes are available from local suppliers, despite being quite expensive) can I get away without C2?

• 1N5819 is perfectly okay for D1, as long as the max voltage is not exceeded. If you need something with a higher voltage rating, 1N4148 might also be okay. However, these diodes will not suffice if you're using rectified line voltage (110/230V) as input, then you need something like the UF4007. For C1/C2, a properly placed single X7R 1uF or 470nF is most probably okay. – Laszlo Valko Jan 15 '15 at 15:22
• Schottky diodes have no reverse recovery, though of course they still have junction capacitance. Unless you go with exotic materials you can't find high voltage Schottkys. As the rated voltage gets higher Schottkys use guard ring structures and other techniques that can sometimes give a response that looks like a little bit of reverse recovery. – John D Jan 15 '15 at 15:24
• @LaszloValko So you are suggesting that I can safely replace all UF4007s with 1N5819s since I am running this off a car battery? What about the MOSFET body diode problem? – Maxthon Chan Jan 15 '15 at 15:28
• You may safely replace those UF4007s with 1N5819s if the maximum voltage in your circuit is below 20V. Those MBR1045s are also perfect choices for the body diode helper role in this case. – Laszlo Valko Jan 15 '15 at 16:40
• @LaszloValko Thanks. UF4007s are hard to find here but 1N5819s are sold at less than US\$0.01 each so it also cuts the budget. – Maxthon Chan Jan 15 '15 at 16:52