LED voltages above 60V in Boost-to-ground topology with TLD509xEP
Community Translation: TLD509xEP を使用した昇圧トポロジーにおける60V以上のLED電圧について
The LED voltage is limited by the pins FBH and FBL (absolute maximum rating is 61V). There are two options if higher voltages than 60V are required:
Place the LED current sensing resistor (RFB) at low side with a 2.5V zener diode to ground. This zener diode avoids false short-to-ground (S2G) failure detections at start-up (S2G detection threshold V~FBL,FBH_S2G~ is max. 2V).
You can find a diagram https://www.infineon.com/cms/en/about-infineon/company/contacts/support/images/LED_above_60V_1.png here.
Place the LED current sensing resistor (RFB) inside the LED string such that FBH/FBL pins will see voltage 61V in all cases. This solution saves the extra zener diode and corresponding power losses, but requires additional wires for RFB. You can find a diagram https://www.infineon.com/cms/en/about-infineon/company/contacts/support/images/LED_above_60V_2.png here
A small signal diode across the LED string is required in both cases in order to enable S2G detection in case the anode is short-circuited to ground. Then the maximum LED voltage is defined as the ratio of the minimum input voltage to the maximum duty cycle (91%).