Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

Oscillation on LED current bad for EMC compliance?

Status
Not open for further replies.

eem2am

Banned
Joined
Jun 22, 2008
Messages
1,180
Helped
37
Reputation
74
Reaction score
23
Trophy points
1,318
Activity points
0
Hello,

i have designed an offline LED driver.

it is flyback.

the LED current needs filtering,
-however, placing a series inductor with the LEDs makes the power stage phase lag too long, and results in instability (oscillation in LED current)

Therefore, i have skimped on LED current filtration , and am settling for a 8mA peak to peak oscillation at 100KHz (switching freq) on the LED current......

LED current oscillation......pink=current; green = DC Bus
2myu5on.jpg


Here is a close up of this LED current
29glfzt.jpg


Here is the schematic:
2cfsbo0.jpg


I would be very surprised if this 8mA pk to pk is bad, since this picture shows what the current looks like in a fluorescent lamp....and they get by without getting banned by the EMC authorities....
23uwmkl.jpg
 

Status
Not open for further replies.

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Top