Baluncore
Science Advisor
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If the output is not regulated then do not mess with the feedback circuit.Salvador said:yet still I am only doing +-70 volts DC output at max.
That core is for a wound transformer, NOT an inductor. Frequency is determined by the components on the PWM clock.Salvador said:maybe judging by this ferrite index we can approximately know how many turns would be required for a given frequency
Yes, that's step two or three for me. Before getting anywhere close to the mains voltage, I'll run the primary off of a low voltage AC bench supply and the control circuitry off a bench DC supply, with the feedback loop jiggered accordingly. Later with with the mains isolation transformer in place, first use a well below design rating fuse, and so on. Little by little.Baluncore said:You must be careful testing that circuit. I use a 1:1 mains isolation transformer and Earth the common reference when working inside live switching power supplies.
Are you suggesting that those in the East are not, or the West should not be extremely concerned about safety?Salvador said:I see that in the west you are extremely concerned about safety ,
I am not going to answer your endless streaming thoughts on modifications to a tested SMPS design if you are not prepared to focus on the real issues. So long as you avoid those critical issues, you are lost. You are reacting emotionally to the circuit. I expect you will mess it up even more by going off on further “reality avoidance tangents”.Salvador said:personally i think i would be better of reducing the duty cycle length and increasing frequency , as to give the transistors more deadtime , since the core saturates probably quite fast anyways so the longer duty cycle is useless beyind saturation yet the higher frequency could push more useful power through the core.
I asked the question because, if you use the scope probe ground on one side of that inline test resistor on the primary, without an isolation transformer, you may well short the high voltage primary to Earth ground through the scope. That won't go well for the scope lead or your primary circuit.Salvador said:so that i can attach an oscilloscope and see the waveform
In practice, the flux density change, ΔB, is
limited either by core saturation or by core loss,
thereby limiting the volt-seconds per turn that
can be applied to a specific core cross-section
area. To fully utilize any core, the design should
result in ΔB close to the saturation or core loss
limit, whichever governs, by adjusting either the
core area, the number of primary turns, or the
ON time.
The flux density in the core (which links both
windings) is determined solely by volt
seconds per turn applied to the primary
(Faraday’s Law), independent of load
current.
The Coroners verdict will be that "the deliberate use of an oscilloscope with a live common chassis" was tantamount to the murder of those who responded to your suicide. I need not say more.Salvador said:ok mheslep, I see your point ,. but the scopes my friend has have no grounding at all in the socket , nor are they otherwise grounded, nor the scope chassis has any ground connection, . most of our sockets don't have any grounding , just the phase and the neutral , even those who have the separate ground connection are useless because the older cables had only two wires in most home AC installations.
NO. Live controls are dangerous to you and the circuit. You can adjust it to the point where it destroys itself while you are trying to optimise output. It is one thing creeping up on an optimum operating point, but you must also be able to get there and back safely when applying, removing or momentarily interrupting power to the circuit at any time. In aerodynamics that region of operation is called "coffin corner".Salvador said:so this is basically saying the same thing i said earlier about having a reostat to control the duty cycle manually, or to see whether the feedback is working ,
Ok, the above comment to me shows this thread is on the verge of needing to be shut down. There is no place in the primary circuit you can put a series resistor and have one side of it already grounded simply due to the nature of the design of the circuit. Sticking a scope probe ground on either side of a series resistor in the primary circuit guarantees disaster. One way to 'see' the voltage across a resistor of this sort using a scope is to have a 2 channel scope that you can invert one channel and use the summing function of the scope. The difference in voltage from one side of the resistor to the other will then show up in the scope display.Salvador said:Also nothing bad can happen to the scope otherwise because the voltage will be only that which is dropped across the resistor hence very small.
If you have to reduce the line voltage to the point that the 5 volt regulator goes out of regulation then use a battery ahead of the 5 volt regulator until you have the problem solved.
Your schematic indicates a 7812 off a 15V (?) transformer.Salvador said:the device is not run from a 7812, its run from a small transformer , rectifier , and two 12 volt zeners in series., in other words from a regulated 24 volt supply.
The design was for kilowatts, but you were only testing 100 watt. Obviously, the energy stored in the full capacitance was capable of destroying the MOSFETS. When doing initial testing you should have been using much less storage capacitance after the line rectifier. You were warned.Salvador said:as I switch the power on the lightbulb in the ac mains barely glows for a little while might have been the split second then I hear a crak noise and the light bulb lights fully.
So you have no 7812 = +12V regulated floating supply, but instead use a 24 volt zenner clamp? Do you have a limiting resistor before the zenners ? Does that explain why the half-bridge driver may be unable to correctly drive the MOSFET gates?Salvador said:the device is not run from a 7812, its run from a small transformer , rectifier , and two 12 volt zeners in series., in other words from a regulated 24 volt supply.
Yep, it just keeps getting better.Baluncore said:How many other things are different from the original design?
That is the case.Salvador said:could it be that if the IR2110 gets supplied by 22 or at most say 23 volts DC it would also drive the mosfet with that voltage level?
What is this? The zenner or the 7812? Where does that average 500mA come from? Only current pulses are needed when MOSFETs are switching. Resistor with Zener must carry current maximum needed over the full cycle. It will waste energy whenever current is below peak of cycle, = very poor for power pulses.Salvador said:One question though, ok the zener regulator isn't that effective but since this is a linera regulator wouldn't it produce quite some heat considering it would have to drop bit more than 10 volts on an average of 500mA?
Buy on specification, not a guess of quality. The quality of your circuit construction is nowhere near as high as quality of Vishay products.Salvador said:Or maybe the Vishay products are less quality ?
When one mosfet is on the other has full voltage of -162V to +162V = 324V total.Salvador said:Also I see some good high current but lower voltage rated devices.Now here's a question , for example if I used a 50a 200v device for both mosfets in the half bridge , as long as the deadime is kept in check and no spikes occur , the devices should work because the voltage any of the device has to whitstand is only half the rectified mains so about 162 volts in my case.I do realize the device would have a higher chance of failing under some unwanted events like spikes from the primary or else but what do you think?
A zener regulator with a series resistor is less efficient than a 7815 since the series resistor with the zener is ALWAYS conducting. A 7815 will not operate in this manner. The 7815 only wastes power when there is current passing through it.Salvador said:One question though, ok the zener regulator isn't that effective but since this is a linera regulator wouldn't it produce quite some heat considering it would have to drop bit more than 10 volts on an average of 500mA?
or maybe it has some advanced little circuitry inside and that's not the case.
There are plenty of linear power supplies out there that are high current supplies. 50 amps is not uncommon.Because usually when I imagine a classical linear regulator I see a half conducting BJT which then is only suited to low current applications due to the excessive heating.
Why not look into a 317 adjustable regulator if your source does not have the 7812? Even a 7805 can be used as an adjustable regulator. Changing a design may be acceptable when you consider all of the consequences.Salvador said:by this i was reffering to the 7812.I think of buying the 7815 because 15 volts is in the acceptable voltage level for a mosfets gate and mainly because the 7812 is not in my store but the 7815 is.after all I've been driving my mosfets with 20 volts and they have stood except for the fairchilds which took a bit more than those 20 and lost the game, 15 vmax should be good.i will see if i can get the 12 volt version but if not ill go with the 15v one.
My photo of a picture in Tiroler Volkskunstmuseum, unknown 17thC European artist, there are several copies and later versions by different people.Salvador said:oh and by the way I see you are a bit eccentric yourself or atleast that's the impression one would get from you r avatar picture which I assume is painted by Salvador Dali, maybe some other not sure ,
Let me and the Museum know if you work out who the artist was. She was well ahead of her time.Salvador said:Will check out his works.
You can also wire it like an adjustable regulator. We know that the regulator will do what it needs to in order to get 5 volts between the ground pin and the output pin. So if we make a voltage divider between the output and ground and tie the ground PIN to the node between the resistors of our voltage divider the output voltage will be determined by the ratio of the resistors in the divider.Salvador said:7805? but the last two digits indicate it's a 5v regulator?