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Expanding on what the other have stated: When the current is turned on and off through a diode, particularly when it shuts off because the polarity is reversed, there is a tiny delay before the diode responds. In that tiny delay it behaves more like a resistor than a diode. It happens extremely fast, often just a few nS pass before it starts or stops conducting. At low frequencies the delay is rarely important but as the frequency increases it becomes more of a problem. Unfortunately, in SMPS the frequency can be quite high and there can be very fast reversals of polarity so the loss in a normal diode causes heat to be generated and the circuit loses efficiency. A schottky doped diode has faster switching characteristics which mean it spends less time in its resistive state and therefore dissipates less heat. As a bonus, the forward voltage drop is also a little lower which means power loss (W = Vf x I) is also less and you get more output voltage. The drawback is they tend to have poorer leakage current and poorer temperature stability so they are not a replacement for normal diodes in all applications.
Hi All,
thanks for all the replies...In the circuit diagram I have attached, D6 is a schottky barrier diode. J10 is a DC supply. Why is it required in this case?
In a DC situation it is only being used because of its lower voltage drop, the time aspect is not important. In you circuit it is being used to prevent reverse connection causing damage.
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