NCL30000 Datasheet, PDF (22/23 Pages) ON Semiconductor – Power Factor Corrected Dimmable LED Driver

NCL30000
Figure 35 shows output ripple current for 115 Vac input
and 36.9 (12 LED) load operating at 350 mA average. Scale
factor is 67 mA per division. The low frequency ripple
follows the input haversine characteristic of single stage
converters.
Figure 35. Output Ripple at 115 Vac and 36.9 V,
350 mA Load
Figure 36 shows output ripple current at the main
switching frequency. Scale factor is 33 mA per division.
This is the signal superimposed over the haversine ripple
component.
Figure 37. Start up Characteristic with 36.9 V, 350 mA
Load
Typical voltage stress on power FET with 36.9 V, 350 mA
load and 305 Vac input voltage is shown in Figure 38. Scale
factor is 100 V per division.
Figure 36. Output Ripple at 115 Vac and 36.9 V,
350 mA Load
Initial start up characteristic is shown in Figure 37 below.
Note the higher current limit controlled by the fast feedback
loop and the transition to the main average mode feedback
control loop. This shows start up at 115 Vac with 36.9 V,
350 mA load. Trace 2 is LED current at 167 mA per division
and trace 3 in applied input voltage at 200 V per division.
Figure 38. Drain to Source Voltage with 36.9 V,
350 mA Load at 305 Vac Input
Note that while the power supply was designed to meet
agency requirements, it has not been submitted for
compliance. Standard safety practices should be used when
this circuit is energized and in particular when connecting
test equipment. During evaluation, input power should be
sourced through an isolation transformer.
Additional Application Information and Tools
An evaluation board is available for this 90 − 305 Vac
design example. Moreover, for applications where it is
desired to dim the LEDs via a TRIAC dimmer, please refer
to Application Note AND8448 which explains the steps
necessary to configure the NCL30000 for TRIAC dimming.
In addition there are two additional TRIAC dimmable
reference designs which illustrate a complete design for 90
− 135 Vac or 180 − 265 Vac operation. There is also an
Microsoft EXCEL spreadsheet tool available to aid in the
design process and assist in developing target winding
requirements for the transformer.
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