Combined in series, I have about 1.2 ohms, and on a stock, unmodified cellphone charger, using this for Rsc sets the current limit (measured with the Fluke 87) at 373 mA. Nov 15, 2006, 06:39 PM #8 flieslikeabeagle flieslikeabeagle Got shenpa? Datasheets: http://www.datasheetarchive.com/search.php?q=GM34063 -Flieslikeabeagle Sign up now to remove ads between posts Nov 15, 2006, 02:27 AM #2 Acetronics Acetronics "MAYONNAISE" Hi, Beagle The Luxeon Leds Have to be CURRENT driven and Or I guess I could just parallel it with the two high-power LED's, again with its own series resistor to keep the current through the third LED suitably low. -Flieslikeabeagle Nov
One charge pump chip especially designed for this application is called "LTC3215"; I have used it quite successfully with 3 NiCads (unfortunalety, the chip is not useful for input voltages > All rights reserved. I do not believe this circuit will work well.The current limit of the MC34063A does have a reliable threshold, but the effect on the timing capacitor voltage is not as predictable. We recommend upgrading to the latest Safari, Google Chrome, or Firefox. This Site
If I leave the circuit set up as is, but connect my PWM to the feedback pin, wouldn't that increase the current at the feedback, and thus dim the LED? The CT pin can become super charged (much higher voltage) between the time the current limit is reached and the coil current falls below the limit. with the comparatorinverting input grounded, no voltage regulation, the current limiting is reversed. dvr2.jpg (14.99 kB, 384x286 - viewed 737 times.) « Last Edit: April 07, 2014, 08:04:21 AM by gobo » Logged valley_nomad Contributor Posts: 16 Re: cheap led driver board questions
Note that some LEDs may have very limited reverse voltage and so it may be worthwhile protecting them with a reverse biassed diode or zener placed in parallel. I understand very well that the LED's need to be driven from a current source, and not a voltage source, due to the exponential current/voltage relationship in a semiconductor PN junction. Features Business Explore Marketplace Pricing This repository Sign in or Sign up Watch 1 Star 0 Fork 0 dword1511/mc34063-leddrv Code Issues 0 Pull requests 0 Projects 0 Insights Pulse Graphs Mc34063 Step Up Circuit The drive transistor current is clipped to (0.3V/Rsc) amps, but that is not the same as the output current from the circuit.
I know this works on other constant current chips but they actually say in the data sheet that you can do it. This was on designing hysteritic control LED Driver using 34063 Please advise. Use the control loop with the LEDs in the feedback circuit. check here The MC34063 will limit current when the voltage across the Vcc-Ipk pins reaches a value between 0.25V and 0.35V.
carefull at selection of inductor , in rest is very well .Maximum current achieved in safe conditions is 700mA , but is enough for my applications . Mc34063 Application Circuit The variation is within acceptable limits for the LED's and illumination requirements, but is "untidy". Here's the kicker, during the off cycle, the energy stored in the inductor wants to go somewhere, and flyback voltage causes a voltage polarity switch across the inductor, so now the Rlimit can be set accordingly.
Follow Us TI Worldwide | Contact Us | my.TI Login | Site Map | Corporate Citizenship | m.ti.com (Mobile Version) TI is a global semiconductor design and manufacturing company. https://e2e.ti.com/support/power_management/non-isolated_dcdc/f/196/t/71405 Agreed, but if you hold pin7 low it holds the osc in reset so there will be no output. #9 Like Reply Oct 23, 2011 #10 MCrowe Thread Starter Member Mc34063 Constant Current Led Driver OR is there another way you could dim the LED? Mc34063 Boost Led Driver For me works for 6 months , and is awesome circuit .
I would normally suggest using a buck converter setup with the LED and current sense resistor as the load and feedback point. As an example, consider driving a series of high intensity starleds at 1W each. The feed back circuit will limit current to (1.25V + Vf) / R2 , where Vf is the forwarding voltage of D3. They can draw up to 700 mA, at which point using traditional resistors to set current flow becomes problematic: the resistors have to be large and heavy, and lots of power Mc34063 Led Driver Schematic
Please login or register.Did you miss your activation email? 1 Hour 1 Day 1 Week 1 Month Forever Login with username, password and session length Home Help gerber image prototype 34063-led.cmd 34063-led.net 34063-led.pcb 34063-led.sch README README NOTE: ONSemi has 34063-style LED drivers NCP3065/3066, which have higher switching frequency and lower feedback voltage. I measured voltage drops at currents from 100 mA to 500 mA for all three diodes, but without additional heatsinking, the blue and green LED's get too warm at currents much Alain posted a method to make the 34063 into a precision current-source, using the same feedback method that is used when making an op-amp current source: Quote: Originally Posted by Acetronics
faster clock = higher current.well, maybe. Mc34063 Boost Circuit I'll bet that it's a buck-type regulator and you do not have a sufficiently high voltage supply. #6 Like Reply Oct 20, 2011 #7 THE_RB AAC Fanatic! Also the driver current on pin 8 will change significantly as VCC goes from 5V to 35V.
Alain The LED's I'm using are rated for up to 700 mA of current draw, and Vref for the 34063 is 1.25 V, so I was initially not enthusiastic about Alain's gobo Contributor Posts: 9 cheap led driver board questions (mc34063) « on: April 02, 2014, 03:37:49 PM » i've been trying to "re-purpose" a cheap mc34063 based led driver board to If this voltage drop is triggering the current limiting, then the duty cycle of the output transistor is changed (the on time is shortened) by charging the timing cap faster. Mc34063 Calculator Reply Cancel Cancel Reply Suggest as Answer Use rich formatting Guru 109820 points Chris Glaser Nov 1, 2010 5:24 PM Kiran, Here is an app note that discusses using the TPS54160
Reply Cancel Cancel Reply Suggest as Answer Use rich formatting TI E2E™ Community Forums Blogs Groups TI training Site Support & Feedback Settings TI E2E™ Community Groups TI University Program Make Customer is fully responsible for all design decisions and engineering with regard to its products, including decisions relating to application of TI products. Robert Keim A Malleable Future: The Worth of Stretchable Electronics Though few companies have marketed finished stretchable products, a new report reveals surprising findings about how massive the stretchable electronics market Last edited by Chippie; Nov 15, 2006 at 02:35 PM.
decrease the input, and the sense drop increases and the frequency increases.at 10vdc the sense drop is 0.097v, led current 45 mils and the freq is 104khz.i built a different drawing. The circuit uses a MC34063 chip in boost converter topology, DO NOT SHORT CIRCUIT THE OUTPUT. If you artificially pull that pin below 1.25v using your PWM output, the regulator will send as much current as it can from it's output to bring that feedback pin back I think it might be prudent to double check your schematic, especially with reference to the LED and Schottky.
To reduce the power loss in the sense resistor, you can bias up that voltage with a TLV431, as described in this EVM for the TPS62110: http://focus.ti.com/lit/ug/slvu254/slvu254.pdf Chris Glaser Texas Instruments Also you could measure the voltage drop across your 2.2 Ohm resistor, to see if it would trigger the current limiting circuit (I think the threshold is around 290mV). COuld you do the same thing with the mc34063?? In that event, the regulator will decrease its' output current. #4 Like Reply Oct 19, 2011 #5 MCrowe Thread Starter Member May 29, 2011 69 0 Oh, yeah I guess
Fred Nov 15, 2006, 09:47 AM #4 Tom in Cincy Tom in Cincy Tom Para I am using a similar circuit. Terms Privacy Security Status Help You can't perform that action at this time. If you try to DECREASE the feedback input below 1.25v, your LED will be subjected to excessive current, and likely burn up. https://www.rcgroups.com/forums/show...69&postcount=8 Nov 15, 2006, 12:13 PM #5 flieslikeabeagle flieslikeabeagle Got shenpa?
Diffley Into the Fukushima Reactor: A One-Way Journey for Drones Drones being sent into Fukushima are malfunctioning much faster than expected. Use of the information on this site may require a license from a third party, or a license from TI. I have a shortage of sub-ohm resistors, but I scrounged up a 0.47 ohm resistor, and three 2.2 ohm resistors which I wired in parallel to make a 0.733 ohm resistor. These voltage drops are lower than I had been told (I'd been told 4V - 5V per LED).
No, it doesn't make sense.