it is just a simple basic boost converter which i used a 555timer as a pulse generator(about 20kHz)Will need quite a bit more info.
Schematic for starters. Input voltage/current, output voltage/current, and what was happening when it failed.
A photo may also help (both sides of circuit board)
So, you mean, most properly, it is my inductor rating problem?Sounds like too much current from here. What is the gauge of wire used on this inductor and what is the current?
If you are trying to use a small choke that is likely the issue, you would be pushing it for ½ amp. For an amp you need to buy one rated for it or roll your own.
I've been working on similar projects, but the 555 version is a bit off in the future. I am one of the local 555 experts around here, and have been writing articles and tutorials during my stay.
Bill's Index
My Cookbook
The 555 Projects
LEDs, 555s, Flashers, and Light Chasers
As that one guy has stated we really will need schematics at a minimum.
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Thanks. I noticed the problem of diode also. I did read the page before but I didn't know how extractly the control feedback system works. To make the voltage goes in to the npn greater than 0.7V is enough,right?A 1N4002 is a standard rectifier diode, and does not turn off quickly enough for a boost converter. You need a fast recovery type diode, or a Schottky diode.
You don't show a feedback path for voltage control. This may cause the output voltage to become very high, particularly with such a small load (20k Ohms).
I suggest that you read through Ronald Dekkers' fine "Flyback Converters for Dummies" page:
http://www.dos4ever.com/flyback/flyback.html
He shows how to use fairly commonly available source material to build your own inductors, and how to measure them.
In his Figure 3 and Figure 16 schematics, replace R4 with 47k maximum, as this will limit the output to ~<=50v; much more safe for a budding hobbyist. Please keep safety in mind at all times.
The 1N400x and 1N540x series diodes are pretty much the same, except for the current rating (1A vs 3A); they are for rectification of AC voltage that's under 500Hz. When you're in the medium kHz range, they turn on fast enough; it's just that they don't turn off fast enough.Thanks. I noticed the problem of diode also.
Pin 5 on a 555 timer is the control voltage pin. Inside a standard 555, there is a voltage divider made up of three ~5k Ohm resistors that set the trigger and threshold levels; normally at 1/3 and 2/3 Vcc.I did read the page before but I didn't know how exactly the control feedback system works.
Are you talking about the transistor on pin 5, or the MOSFET that's shown on Ronald's page?To make the voltage goes in to the npn greater than 0.7V is enough,right?
If you're talking about the NPN transistor in your circuit, then you would need a transistor rated for at least 50v.Do you have any suggestion for the npn I should use, my target output is 45V.
Ok, I will edit my CP later. I am a student in Malaysia.The 1N400x and 1N540x series diodes are pretty much the same, except for the current rating (1A vs 3A); they are for rectification of AC voltage that's under 500Hz. When you're in the medium kHz range, they turn on fast enough; it's just that they don't turn off fast enough.
Pin 5 on a 555 timer is the control voltage pin. Inside a standard 555, there is a voltage divider made up of three ~5k Ohm resistors that set the trigger and threshold levels; normally at 1/3 and 2/3 Vcc.
Referring to Ronald Dekkers' page, as the voltage on the output of the boost or flyback converter goes higher, the voltage on the base of the NPN transistor goes higher, eventually turning the NPN transistor on, which pulls the CTRL pin 5 low; this has the effect of both increasing the frequency of the 555 timer, and decreasing the ON time of the MOSFET.
Are you talking about the transistor on pin 5, or the MOSFET that's shown on Ronald's page?
A 2n2222 for the NPN on pin 5 and an IRF510 would work OK for the MOSFET.
If you're talking about the NPN transistor in your circuit, then you would need a transistor rated for at least 50v.
Instead of a transistor, I suggest using an N-channel power MOSFET.
Are you in the USA? If so, your local Radio Shack probably has all the stuff you need to make a basic switching regulator.
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Oh thanks again. I ordered some inductors from a website already. But, it doesn't show the picture of the inductors. Anyway, from your opinion, you mean the inductor burst is because of itself rating cannot withstand the 1.2A current, am I right?The best solution for inductors is to order some ferrite cores and wind your own to the value you need. Typically one type of toroid mix that you have the data for on how many turns you will need.
The resistor sized inductors cannot handle very much current at all, as you've found out.
Not more than 100mA unless it is a very large resistor physical size.Oh thanks again. I ordered some inductors from a website already. But, it doesn't show the picture of the inductors. Anyway, from your opinion, you mean the inductor burst is because of itself rating cannot withstand the 1.2A current, am I right?
1 more thing is, i couldn't find the rating of resistor-like inductor. Basically, I don't know how to search it. Could you please help?
I couldn't see anything from that page.Not more than 100mA unless it is a very large resistor physical size.
Did yours look like the top one in This Search? Anything of a higher current ends up physically larger, you would want something around 28 gauge wire minimum for the windings.