Decreasing gain while the circuit is operating leads to an increasing in gain, and the output stays stable. Let’s get serial UT Feedback Control This circuit promises greater accuracy, if that is a requirement, as well as more flexibility in choosing the current setting sense resistor value. I know this works on other constant current chips but they actually say in the data sheet that you can do it. Jul 17, 22, 1, Boost converter current source for LEDs Hello. If you use a chip like a ua78s40 which is very similar to a MC, but includes a catch diode and a spare op amp you dont need any extra components.

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The constant current sources are not much different from the buck converters above but with no inductor. Maybe the current does not actually flow through the current sensor? No, create an account now.

You’d need three supplies, one for curfent color. I have an Ultimaker and a 3D engraver. Even if the needed current is well within the specification, the MC may get really hot, wheras with the external switching transistor, it remains at room temperature.

May 29, 69 0.

mc34063 Constant Current

I’ve only recently begun soldering SMT parts, but I’ll be having PCBs made for all of this, so I can go surface connstant where needed, to keep things small. Last edited by DeepOne; 21st April at You are likely bumping lsd against your current limit.


So that kinda sucks. It’s a little more complex than a simple soft-start, but should give you some wiggle room to optimize for your application. Derek Lewis 2 7.

IEE Floating Point addition 7. 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. Unless you mean the duty cycle of leed output switch rather lef the capacitor.

I can understand why this is occurring on a very rough basis: Any linear solutions need to have a low drop out voltage to avoid generating too much heat.

LED Driver Circuits

The amplifier gain can be chosen so that the voltage drop across the sense resistor is kept very small, say mV or less. I’ll give that a try. I need to fit 36 of them into a fairly small area, I don’t know how small they can be made. Boost converter current source for LEDs Hello. Would you like to answer one of these unanswered questions instead?

12V AC-DC Converter MC Driving mA LED 12V Source – Electronics Projects Circuits

That will create too much heat for my application. Let’s get serial UT The LEDs continue to light currenf in the overcurrent, but at reduced intensity. I’ve been thinking of using the MC in buck mode as a current regulator, by using the correct value of current limit resistor.


I will research more about SPMSs in the meantime, thanks.

One options I looked at is using 3 switching dc-dc converters, adjustable, one for each colour of LED chip, and lde them to just above the highest Vfwd of the 12 LEDs, and using resistors to limit the current.

Here is one way to delay powering the sections that draw the larger current, allowing the unit to boot up before powering the final load.

Boost converter current source for LEDs Here is what i ended up with, with external switch. Care will need to be taken when high gains are used, as vurrent and noise will be amplified. Should these be asked as separate questions? Right, that makes some sense but: Sign up using Facebook.