tiny winy smps  - Page 1
Forum section: electronics / projects

author: dave_j_fan
author_rank: Regular Contributor
timestamp: January 09, 2015, 01:47:16 pm
content: small diy smps fried the 10E entry resistor , i purposely put a 0.25w 10E? what may be wrong--checked coils they are finetaking baby steps to smpsmy values are in redhow to test without frying transistors ??

author: LukeW
author_rank: Frequent Contributor
timestamp: January 09, 2015, 02:22:06 pm
content: Maybe have a look at this to get some ideas.http://www.power.com/sites/default/files/product-docs/linkcv_family_datasheet.pdfYou could look at designing your own circuit with discrete components to replace the controller chip, but take away the "good ideas" away from that reference design. (Or other reference designs for offline SMPS from TI, PI, or whoever). Obviously you can adjust the secondary output stage to suit your needs with one rail.A fusible resistor on the input can be a good choice in production designs to minimise BOM count and cost whilst maintaining UL etc. compliance, but for R&D on the lab bench it may be best to remove it and add a fuseholder or circuit breaker, and over-rate the power rating of that resistor. Or keep a big pile of fusible resistors handy because you'll pop them pretty oftenI think full wave rectification might be better, or at the very least if you've got one diode use a pi filter - add an inductor and a second 4.7uF 400V cap - to provide a relatively smooth HT DC input rail.

author: diyaudio
author_rank: Frequent Contributor
timestamp: January 09, 2015, 02:36:06 pm
content: Quote from: dave_j_fan on January 09, 2015, 01:47:16 pmA IN4007 rated at 1A in series with a 220V SMPS, I wouldn't even dare build this. well it is cheap Chinese design why the risk ?

author: T3sl4co1l
author_rank: Super Contributor
timestamp: January 09, 2015, 02:37:50 pm
content: All problems solved if you pay more than $3 for the POS.

author: Yansi
author_rank: Super Contributor
timestamp: January 09, 2015, 02:42:49 pm
content: diyaudio: Whats wrong with 1N4007 being used on mains power? The diode is pretty usayble there. Or why would you use eg 10 amp diode for mains rectification in such 5W PSU?The only good suggestion would be to use bridge rectifier, insted of halfwave. I see nothing wrong with the circuit, its a standard self oscillating flyback converter. Maybe the wrong thing is that it is being oldschool and cheap?And note, that the 4007 on primary shoud be UF4007, instead of slow 1N4007.

author: Kalvin
author_rank: Super Contributor
timestamp: January 09, 2015, 03:06:08 pm
content: Quote from: dave_j_fan on January 09, 2015, 01:47:16 pmYes, you stated that the coils are fine, but are you sure that the transformer coil winding directions are correct ie. the dot-convention match to the original design?

author: Yansi
author_rank: Super Contributor
timestamp: January 09, 2015, 03:32:03 pm
content: Winding orientations...By the way, where did you get those turn counts and ratios? Were the properly calculated according to your exact type of core? Has the core properly calculted air gap?

author: dave_j_fan
author_rank: Regular Contributor
timestamp: January 10, 2015, 06:45:39 am
content: Quote from: Yansi on January 09, 2015, 03:32:03 pmit was ordered for a led driver smps..http://homemadecircuitsandschematics.blogspot.in/2014/09/32-v-3-amp-smps-led-driver-circuit.htmlthis circuit has opto tc ... yes opto is better but yeeah ... the self oscillating ck sd work ...please see the windings are different in my case than the original design...fusible resistors -- good idea ... i am thinking to power the ckt from a 24VAC xformer seconday , what u say it will oscillate ?

author: dave_j_fan
author_rank: Regular Contributor
timestamp: January 10, 2015, 06:47:00 am
content: Quote from: Kalvin on January 09, 2015, 03:06:08 pmmay be the dot part has an issue .. if i am wrong at the dots will it stop oscillatingNeed to check tryme-dont fry me tricks...seems most smps dont respond <100V so plan to do 24v ac test is ruled outsteps to move forward :1)read the pdf link (http://www.power.com/sites/default/files/product-docs/linkcv_family_datasheet.pdf) nice info ---given by LukeWunderstood the required parts ,the best infor so far :"the RCD clamp is to protect the devices from leakage emf spikes "means it is not part of oscillator2)pulled the circuit explanation in pathetic english=================================For the market everywhere in the mobile phone charger,universal charge is growing rapidly, but are not very high quality, often a problem, throw a pity, it will teach you the recipe for analyzing the principles of cell phone chargers, hope that they can repair bring some help. Analysis of a power supply, often started from the input. 220V AC input, end of 4007 after a half-wave rectifier, the other end through a resistor 10 in Europe, by the 10uF capacitor filter. The resistance used for 10 protection in Europe, if followed as a result of over-current fault occurs, then the resistance will be blown, so to avoid a bigger failure. Right 4007,4700 pF capacitor, 82K? resistor to form a high-pressure absorption circuit, when the switch off when the 13003 is responsible for absorption of the induction coil voltage, thereby preventing the pressure added to the switch 13003 which led to breakdown. 13003 for the switch (complete name should be MJE13003), voltage 400V, the maximum collector current of 1.5A, the maximum collector power dissipation of 14W, is used to control the primary winding and power between the pass, off.When the primary winding non-stop off, they will change in the switching transformer in the formation of the magnetic field, thereby inducing a voltage in the secondary winding. Because the figure does not indicate the end of winding of the same name, it can not be seen to be a forward or flyback. However, the structure of this circuit point of view, can be inferred that this power should be the flyback's. 510K? resistor to start the left side to switch to provide start with the base current. 13003 10? resistance below the current sampling resistor, the current into a voltage by sampling after (its value is 10 * I), this voltage by the diode 4148, the increase to the base of the transistor C945. When the sampling voltage is greater than approximately 1.4V, the switch current is greater than 0.14A, the transistor turn-C945, which will switch 13003 of the base voltage down to the collector current decreases, so that limits the switch current to prevent the current burn too large (in fact this is a constant current structure, the maximum switch current limit 140mA or so). Bottom left of the winding transformer (sampling winding) of induced voltage by the rectifier diode rectifier 4148, 22uF capacitor filter to form a sample voltage. For the convenience, we take the C945-emitter transistor to one end. Then this sample is the negative voltage (-4V or so), and the higher output voltage, the sampling voltage is more negative. After sampling voltage 6.2V regulator diode, added to the switch 13003 of the base. Said earlier, when the output voltage is higher, then the sample voltage more negative, as negative to a certain degree, 6.2V voltage regulator diode is the breakdown, which will switch 13003 of the base potential of down, which will lead to switch disconnect switch or delayed conduction to control the energy input to the transformer, also control the output voltage increases, the regulator output to achieve the function. The 1K? below 2700pF capacitor in series with resistance, it is positive feedback branch, removed from the sampling winding induced voltage, added to the switch on the base to maintain oscillation.==================================same text my version of moderately understandable english---MJE13003 (t1 )is used as a switching transistor , it can withstand upto 400v ..4007,4700 pF capacitor, 82K resistor to form a RCD clamp to kill the spikes during switchoff of MJE13003primary receives a sudden voltage by the action of MJE13003 turning on , this induces a secondary voltage510K resistor to start the left side makes the MJE13003 on with a base current ..10ohm resistance below the current sampling resistor at the emitter of C945id T1 switch current is greater than 0.14A t2 turns the T1 off and imposes current limit .the second winding acts like +ve voltage feedback via 1K and 2700pF to "maintain the oscillations "6.2V regulator zener limits to safe levelsTHe secondary circuit is simple it is just hallf wave rectified dc with filter capacitor 220uFseems it is like the led ccs circuit where a small transistor is pulling the big transistor if current exceededhttp://www.talkingelectronics.com/projects/200TrCcts/images/ConstantCurrent-2.gif

author: dave_j_fan
author_rank: Regular Contributor
timestamp: January 15, 2015, 04:47:39 pm
content: Quote from: blueskull on January 09, 2015, 07:54:16 pmi have UF4007 i will try thatwell my effort to wind trafo failed with heating (not in this ckt in another circuit ) so not touching the trafo now , if it is 80V i will use it with series led designsand later ask the winder guys to reduce the turns

author: amyk
author_rank: Super Contributor
timestamp: January 15, 2015, 04:58:10 pm
content: Use a current limiter, raise the voltage slowly on the input and see if it's even starting up.Also worth doing a simulation too to make sure you didn't get anythingreallywrong.

author: dave_j_fan
author_rank: Regular Contributor
timestamp: January 15, 2015, 05:04:25 pm
content: Quote from: amyk on January 15, 2015, 04:58:10 pmany recommended current limiter ..? i dont have HV PSU ..triac based dimmer only possible

author: Yansi
author_rank: Super Contributor
timestamp: January 15, 2015, 07:38:23 pm
content: triac dimmer...Use standard variac, or you will very likely destroy the dimmer or your circuit or both. Not mentioning that the dimmer is not a variable voltage source soutable for this.