AN2983 datasheet(21/32 Pages) STMICROELECTRONICS

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AN2983

Circuit description

Doc ID 15679 Rev 1

21/32

2.7

Auxiliary power

The components for the auxiliary power supply are Q1, D2, C2, R2, R3, and R5.

This section is included as a commodity to reduce the main voltage (48 V nominal) to the

18 V required from the Vcc input of the L6562A controller, thus avoiding the use of another

power supply. It has been designed to work with input voltages in the range of 33 to 65 V, but

can be easily resized for different ranges.

Note that it is a linear regulator and that its efficiency is not very good. For this reason, in

real applications where multiple modules are employed, it is better to consider a solution

with an external supply common to all the modules.

Simply removing R2 and R5 disconnects the entire block and allows the power supply (Vcc)

to be provided from pin 5 of the header connector.

Figure 21.

Auxiliary power

Figure 19.

Dimming 90%

Figure 20.

Dimming 99%

CH(4) green: LED current [mA]

CH(1) red: gate drive output [V]

CH(3) purple: D_Dimm input [V]

CH(4) green: LED current [mA]

CH(1) red: gate drive output [V]

CH(3) purple: D_Dimm input [V]

AN2983 Fiches technique(PDF) 21 Page - STMicroelectronics