Auto-Restart Treshhold V_VO(AR) > U_fwd of one LED

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The interesting IC LYT6073C has a problem for my application.
Task: a constant current source with e.g. 300 mA at 0..10 V (1..3 LEDs, serial). With a forward voltage of 2.6 .. 3V (one LED), the output voltage is below Vvo, which would be interpreted as an error.
Is there an alternative or a workaround?

Hi Holger,

Thank you for your interest in using PI product LYT6073C. Please verify from what i understand, is Vo = 0V to 10V, Io = 300mA, LED load = 1 to 3 LEDs in series? What is the output voltage Vo at full load? Can you show me the schematic?

What do you mean by Auto-Restart Treshhold V_VO(AR) > U_fwd of one LED?

Please see the following:

1. If the forward voltage of each LED is 2.6V to 3V then 3 LEDs series will be equal to around 7.8V to 9V. This is below 10V. You can try to use an electronic load module to check at exactly 10V LED output.

2. Please make sure that feedback FB pin voltage is at around 1.265V. Please check the datasheet for other parameters.

Thank you. I hope this can help.

Hi PI-Zek,

thanks for your quick answer.

datasheet, p7:
The OUTPUT VOLTAGE pin includes a comparator to detect when the
V_VO (AR) of V_VO, for a duration exceeding t_VOUT (AR).
Thus, if the output were loaded with only one LED, the output -due to the fault condition- would be disabled for some time.

I'm looking for a way to drive 1 to 3 LEDs -> minimum output is around 2.6 V, maximum <= 10 V at CC 350 mA.

Regards Holger

Hi Holger,

Yes it will be an Auto-Restart when the load is 1 LED = 2.6V. The threshold for VO pin is at 3.45V (p.26 LYTSwitch-6 Datasheet). You can try to add a bias winding which can deliver >3.45V to VOUT pin when the load is 2.6V only. You may also use this bias winding as supply for FWD pin.

We usually add a bias winding when the output voltage of the power supply is >27V which exceeds the Vmax of VOUT pin. You may refer to DERs with >27V output (example DER-657 with secondary bias winding). I hope this can help. Thank you.