grizedale
Advanced Member level 3
Hello,
We are doing a 90-265VAC isolated , offline, half-bridge SMPS [+/-50V(out) and 330W] which must have a very fast transient response.
The load is just going fully on , fully off , very suddenly, all the time.
We are using TL431/OPTO regulation and so do you believe that its essential, to get a standing current flowing in the opto-diode, so that its CTR is at its peak?
...because i notice that CTR drops off very badly at low diode current...as the graph at the bottom of the CNY17F datasheet testifies.
CNY17F opto datasheet
https://www.farnell.com/datasheets/90931.pdf
Low CTR means low gain and so poor transient response?
The resistor that i mean to use to "bias" the opto diode is as in R39 (12k) in the following schematic......
https://i55.tinypic.com/eh1b13.jpg
Is this resistor necessary?
We are doing a 90-265VAC isolated , offline, half-bridge SMPS [+/-50V(out) and 330W] which must have a very fast transient response.
The load is just going fully on , fully off , very suddenly, all the time.
We are using TL431/OPTO regulation and so do you believe that its essential, to get a standing current flowing in the opto-diode, so that its CTR is at its peak?
...because i notice that CTR drops off very badly at low diode current...as the graph at the bottom of the CNY17F datasheet testifies.
CNY17F opto datasheet
https://www.farnell.com/datasheets/90931.pdf
Low CTR means low gain and so poor transient response?
The resistor that i mean to use to "bias" the opto diode is as in R39 (12k) in the following schematic......
https://i55.tinypic.com/eh1b13.jpg
Is this resistor necessary?
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