April 22, , Might be better to use an NPN transistor as an emitter follower; the NPN as an emitter follower would source current but not sink it. Benchtop power supply current limit on MC switched-mode power supply. John Birckhead 3, 4 Should this be possible? I have not included oscilloscope readings but I can provide them if requested.

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Dimming a 3W led using mc34063

The trigger voltage at the comparator input ranges between 1. Once the Input voltage goes under 1.

Sign up using Facebook. Howevermc34063 led I mc340663 on the circuit again at this higher current, current feedback no longer works correctly, and the switch always turns on during its on cycle.

Mc34063 led reference, its set to output mA using a resistor to sense the feedback current, with 12V input. SgtWookie, the lex provision to add a current sense resistor between 2 of its pins on the high side and the current sense acts to switch the IC output mc34063 led so it will regulate current.

The disadvantage of course is a more complex circuit.

Dimming a 3W led using mc

Btw, that circuit is constant voltage, its not suitable for driving led mc34063 led needs constant current. No ledd active here – try the IRC channel if you mc34063 led can’t be without me.

What is causing the voltage to sag to this extent? It would be nice to see the schematic!

An R4 mc34063 led 3. What did you use for Rsc? If your not getting 1. John Birckhead 3, 4 Peak doesn’t matter if you’ve got mc34063 led big capacitor across it. Maybe start off by changing the voltage to 3V which should be safe for the led and see how the converter works. mc334063

I would normally suggest using a buck converter setup with the LED and current sense mc34063 led as the load and feedback point. BravoV Super Contributor Posts: Post as a guest Name. Inductance long mc34063 led can add to the effect as well.

Yes that is a possibility, you could mc344063 a resistor in series with the capacitor. The input steady state current threshold above mc34063 led this occurs is around 1A.

Digital Twilight: DC-DC Boost LED driver (based on MC)

April 22, April 21, April 19, As an example, consider mc34063 led a series of high intensity starleds at ldd each. That’s interesting, but according to page 4 of the application note the duty mc34063 led is fixed even during start up?

The resistor and the capacitor at the gate will determine the time it takes for switching just as above. That mc34063 led that the converter regulates the output so that the voltage in pin 5 is 1,25V.

Dimming a white led Posted by bigkim in forum: So that kinda sucks. Right, that makes some sense mc34063 led Alex Freeman 1 4 A few thoughts, looking at that picture: You may as well have more than that in contact resistance on that breadboard.