meastwood98
New Member
Hi,
Im using a DC-DC convertor and the datasheet suggests the following over-voltage protection (see attachment). The voltage in is 28v and the output is 3.3v. The max voltage my component it is powering can take is 3.6v.
I have selected a 2.4 zener diode and a 1.2v drop opto coupler, therefore once the output voltage becomes >3.6v, current will flow through the opto-coupler and resistor. My problem is calculating the value for the resistor.
If I design it for a voltage around 4v, if the output voltage error is 28v then the current through the opto coupler will be huge and probably damage it. However if I design it for a voltage of 28v, if the over voltage is around 4v, then there will not be enough current to switch on the transistor side of the opto coupler.
I hope this is clear,
Thanks,
Mark
IMAGE: ENGINEERING.com | File Downloads
Im using a DC-DC convertor and the datasheet suggests the following over-voltage protection (see attachment). The voltage in is 28v and the output is 3.3v. The max voltage my component it is powering can take is 3.6v.
I have selected a 2.4 zener diode and a 1.2v drop opto coupler, therefore once the output voltage becomes >3.6v, current will flow through the opto-coupler and resistor. My problem is calculating the value for the resistor.
If I design it for a voltage around 4v, if the output voltage error is 28v then the current through the opto coupler will be huge and probably damage it. However if I design it for a voltage of 28v, if the over voltage is around 4v, then there will not be enough current to switch on the transistor side of the opto coupler.
I hope this is clear,
Thanks,
Mark
IMAGE: ENGINEERING.com | File Downloads