IRPLLED1A International Rectifier, IRPLLED1A Datasheet - Page 23

• Manufacturer Part Number: IRPLLED1A
• Description: Power Management IC Development Tools Hi-Vlt DC-DC Buck Cnvr HBLED Cur Cntrl
• Manufacturer: International Rectifier
• Type: DC/DC Converters, Regulators & Controllersr

Specifications of IRPLLED1A

• Product: Power Management Development Tools
• Tool Is For Evaluation Of: IRS25401PBF
• Output Voltage: 16 V to 24 V
• Output Current: 350 mA to 1.5 A
• Factory Pack Quantity: 1

a mechanical isolation system could be used to disconnect the LEDs completely from the ballast for safe access. In
an illuminated sign for example, this would be a reasonable approach.
The open circuit protection system described in this section can only be an effective safety feature in a system where
the IRS25401/11 Buck stage is used as a back end stage supplied by an already isolated DC source. It does however
serve to limit the output voltage to prevent damage to the output capacitor COUT in cases where the bus voltage is
greater than the rating of this capacitor.
Note:
The over voltage protection scheme used in the IRPLLED1A evaluation board is different to that used in earlier
revisions of the IRPLLED1A and does not conflict with the synchronization operation described in the previous
section.
The open load protection circuit in Fig 29 is recommended for isolated non-dimming applications where the load
may be disconnected and then reconnected without shutting down the driver. When the load is reconnected with
power on this would reduce the initial surge of current to the output reducing stress on the LEDs .
In an open circuit condition, switching will continue at the HO and LO outputs, whether due to the output voltage
clamp or to the watchdog timer.
Due to the operation of this circuit the output voltage under open circuit conditions where JDIM is in the DIM
position is made up of pulses as shown in Fig 30. If JDIM is in the REG position then these pulses will delay slowly
as the output discharges. This can leave an average voltage of approximately 50V at the output. The decay rate of
these pulses depends on the value of COUT and the interval between pulses depends on the time taken for CVCC1
to charge above VCCUV- through RS1 and therefore depends on the input voltage.
Fig. 30 Open Circuit Fault Signals, with Clamp
RD-0608
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