Trying to identify SMD with label scrubbed off - PWM, inverter, 100W 12VDC to 120VAC modified sine wave (2023 Update)

Freescale has 16-pin PICs with two-pin oscillators hanging around that end of the package. Usually 15-16, though.

What's the surrounding unit's branding/model number?

RL

I've posted a photo of the board here:

Turns out to be Feihong's logo. Never heard of them...but lets find an English product line to see if they make 16 pin SMD inverter ICs...

Thanks,

John :-#)#

'Modified' sine wave output ?

2step, 4step or full pwm?

Logo on the box?

The unregulated DC-DC, 12-120v section can survive without any energy storage, except for capacitors and leakage, but I see no attempt to filter the full bridge output.

EG Microelectronics offers a demo board (1" x 2") that includes hv gate drivers to produce dedicated low frequency full bridge sine power.

Anything higher is aimed at an audio market.

There are many variable frequency motor drivers that don't depend on sinusoidal waveforms.

RL

The Slowman fool puked: =====================

** Not how real "mod sine" inverters operate. There are two requirements on such devices:

1. Output the normal supply peak voltage.
2. Output the normal supply RMS voltage.

Using these two, the "off" time must be 50%.

Using only 33% would result in incandescent lamps failing in seconds.

.... Phil

The standard modified sine wave has an off time of 33% and doesn't blow up incandescent lamps.

A regular 240V rms sine wave has a peak voltage of 377V. A modified sine wave would produce 240V rms if the "on" voltages were +/-294 volts.

If you want to rectify the output (which would be an odd thing to with an inverter) you might set the "on" voltages as high +/-377V.

I don't know what kind of half-wits you have been dealing with, but you clearly haven't done much thinking about how this gear is used.

The Slowman f****it PUKED : =========================

** ROTFLMAO !!!!!!!!!!!!!!!!! ** Absurd & insane crap. ** Same INSANE error.

** I'm dealing with a FUCKING MASSIVE one right now !!

FYI : you raving NUT CASE

240V rms sine = 340 V peak 340 V continuous = double power with a resistive load. 340 V at 50% duty cycle = same as 240 V rms sine

Fucking Chemistry Freak.

..... Phil

It's not a great waveform for driving a synchronous motor, but better than a square wave.

Not all that clever, but he does write very clearly, and doesn't waste his time explaining stuff that is difficult to explain. I first came across him when he started writing for Byte, to which my wife had given me a foundation subscription, and which I kept on reading until it folded. Nothing I read of his ever told me anything I didn't already know, but he did put it neatly.

Ten to fifteen percent you could get out of a Baxandall inverter by switching capacitors in and out of the resonant circuit, but that would only be worth doing if you didn't need much power.

Probably. I was using pi/2 which - on reflection - would have been right for the average voltage rather than the average power. I'll have to dust off my integral calculus and do it right.

So what's voltage you need to get the same a 240V sine wave at a 66.6% duty cycle? Perhaps 294V?

And why wouldn't you use that?

The Slowman f****it PUKED : =========================

==========================

** See rule 1.

The reason is bloody obvious.

Actually it is trigonometry.

Cos 2.theta = 1 - 2.(sin theta) ^2.

which means that (sin theta)^2 = 0.5 - cos 2.theta

So the integral of ( V. (sin theta))^2 over theta from 0 to 90 degrees is [0.5 + sin 2.theta] or V^2/root 2.

So the peak voltage is 339.41V for a 240V sine wave.

A rule you seem to have invented. Regular modified sine wave generators don't seem to take it too seriously.

The justification for making that choice might be obvious, but having third harmonic content in the output isn't an advantage, and people who know what they are doing are free to make a different choice.

The Slowman f****it PUKED :

==========================

** Absolute certainty a f****ng, know nothing TROLL like YOU has never even seen a REAL one.

.... Phil

<snip>

Is there a relationship between the RC oscillator waveforms and the low frequency output drive?

Does a 10% shift in the R or C get a corresponding shift in the ~60Hz cycle?

Is the input DC/DC synchronized from the same clock?

RL

I might have. The kind of complicated high-end gear I worked on didn't go in for them, but my wife has colleagues who have consumer level gadgets to adapt their domestic gear to work on UK, US or Japanese main voltages when their owners are working overseas.

The 120V coffee grinder my wife bought in Boston used one for years when we lived in England and the Netherlands. We eventually gave it to somebody who was moving to a 120V country, and I bought a 240V replacement for us to use.

The theory is obvious enough - even if you don't know much about it - and it has been discussed here from time to time.

That was the direction I was planning on going as it looked the easiest way to modify the frequency. I've done this before on other inverters that didn't scrub the numbers off.

Application Notes are so very handy for this sort of thing - knowing the capabilities of the IC would be of some use to know how to get the range of output frequency I'm after. I guess I'll just plug with a resistor in the PWM clock - use some high value pot to tweak the value and watch the output on the scope or use my frequency counter once I have something that changes the Hz...

John :-#)#

Even if the input DC-DC is synced, going up in frequency by a factor of 4 won't kill anything, but the load reg will suffer due to leakage inductance. Series gate resistors will get hotter and any clamps will be stressed. Thermal imaging might pick out anything troublesome.

The output bridge doesn't care.

Loads might be more picky.

RL

On Fri, 6 Aug 2021 23:54:07 -0700 (PDT), Phil Allison snipped-for-privacy@gmail.com wrote: <snip>

The peak output voltage on this thing is 120v, in an attempt to power 120v AC loads, so a straight square wave ends up supplying 120v average, rms or whatever else you might want to call it.

Light bulbs might be the only 'safe' load . . .

A peak-rectified capacitive load would see this as being close to drop-out levels, but with almost no crest factor to sweat it.

RL

I took a brief look. Didn't find your part, sorry, but found a nifty little ASIC from a Chinese company that works as a true sine wave controller. Unipolar or bipolar modulation and either handles the stuff after the 400V bus is created or can do the whole shebang with a low frequency transformer.

Tease! Part numbers or it didn't happen :)

EG8010

I guess it's a pre-programmed MCU with or without some extra peripherals, but pretty nifty. Sells for a buck and change at LCSC, but they don't have the English datasheet linked.

Speaking of parts in that price range, is anyone thinking of using the Rpi chip RP2040 in a real product?