Oh!

I forgot to mention soft-switching, that's the
most common catch-all term.

On Sep 8, 7:13*pm, Grumpy The Mule wrote:
THESE MUST BE OPERATED UNDER LOAD OR THEY WILL SMOKE.

At least that is what happend to mine.

Jimmie

Oh, sorry to hear that. *Yeah, it's a bad idea to operate
any switch mode power supply without a minimum load unless
the min. load is built-in or the thing is so inefficent that
its own losses make up the minimum load. The output diodes
probably didn't like that... just my guess.

I found some interesting stuff on the panasonic inverter.

On the fusor chat they claim it's 85% efficient and good for
1200W. *The efficiency seems right, the 1200W seems... optimistic.

Also this, instructions on getting the inverter to play.http://www.fusor.net/board/view.php?..._hvpower&key=1...
046 *

Hey mule:
Your url got cropped.

The inverter PS I have can be fooled into thinking it has a load.

There is a current sense I found and a voltage sense
both on the primary side.
It's a piece of cake opto coupling a signal back
to those sense inputs. they are both straight voltage dividers
with Vrefs. And the current sense uses a 50K ohm trim pot for
adjustment.

They use a 100meg bleeder for a load. And the filament which is at
least
150 watts, loads the supply too.

I suspect my 120VAC inverter will work off of 240VAC

And if you take out the filament circuit that gives yoiu an extra 150
watts.
I suspect I can gits 1500 watts from my 1300 watt interer PS, with
input
filtering of the DC off the mains.

But the final report wont happen until i gits the feedback circuit
wired.
That will prevent it from trying to produce 1300 watts into no load.
With no load it will try to up the voltage to produce more current.
Which it can't
produce more current so it keeps increasing the voltage untill it lets
out the smoke,

When it hits 3000 volts I will fool the sense circuits: a voltage
divider for
the current sense and another divider for the voltage sense, into
seeing 1300 watts.

Another trick is to run the mains off a variac starting at 10 VAC very
slow. Also supply seperate power to the PWM IC circuit,
Just to see how far it will go, and not get it to go into run away.

I see the power trouble how can you gits 1300 watts out of that little
bitty core?
That's what they used to say about silicone diodes when they used to
replace a 5U4 tube.
They used to tell me how can a little piece of wire with a bead on it
replace a tube as big as your fist
no freaking way. I also made a living selling 2.5 amp 1000 piv diodes.

I mean the primary of this thing uses litz wire that looks like 10AWG
wire about 13 turns around the core
and they using 4 strands of 28 AWG to run the filament
The HV secondary measures only 6.8 ohms DC.


73 OM

n8zu

Ok, this should work. http://tinyurl.com/6at4zu

I mean the primary of this thing uses litz wire that looks like 10AWG
wire about 13 turns around the core
and they using 4 strands of 28 AWG to run the filament
The HV secondary measures only 6.8 ohms DC.


I'm glad you mentioned that. If the core is ferrite and it's gapped,
then the litz makes sense to reduce eddy current losses from the
fringing field sprayed out of the gap. A gapped core would also most
likely mean it is a flyback.

It really is amazing the power density SMPS can achieve. Though the
overload capacity available from big hunks of iron and copper isn't
to be discounted lightly. I had to pick up a 10KW autotransformer
today. I don't know how much it weighed but I'd guess 130lbs, or
there about. The two transformers in the 10KW SMPS are maybe four
pounds total.

On Sep 9, 7:50 pm, Grumpy The Mule wrote:
Ok, this should work. http://tinyurl.com/6at4zu

I mean the primary of this thing uses litz wire that looks like 10AWG
wire about 13 turns around the core
and they using 4 strands of 28 AWG to run the filament
The HV secondary measures only 6.8 ohms DC.

I'm glad you mentioned that. If the core is ferrite and it's gapped,
then the litz makes sense to reduce eddy current losses from the
fringing field sprayed out of the gap. A gapped core would also most
likely mean it is a flyback.

It really is amazing the power density SMPS can achieve. Though the
overload capacity available from big hunks of iron and copper isn't
to be discounted lightly. I had to pick up a 10KW autotransformer
today. I don't know how much it weighed but I'd guess 130lbs, or
there about. The two transformers in the 10KW SMPS are maybe four
pounds total.

Hey mule

Exactly right it is a gapped core. Once I git's a scope on I'll see.

But the voltage doubler they using is full wave doubler. Which means
they taking the positive and negative waves to get 4000 or so volts
DC
Now the positive half they use a .0082 mfd for a filter and the
negative half they use a .0056 mfd filter both at 3000wvdc.
..
They use a damper diode that looks like a varistor, and a hold down
cap is .032 mfd at 500V across the primary.
The power into the primary is filter by an LC just to prevent the RF
getting back into the mains/bridge diodes pack.

73 OM

n8zu

Exactly right it is a gapped core. Once I git's a scope on I'll see.

But the voltage doubler they using is full wave doubler. Which means
they taking the positive and negative waves to get 4000 or so volts
DC
Now the positive half they use a .0082 mfd for a filter and the
negative half they use a .0056 mfd filter both at 3000wvdc.


my guess is the quasi-push pull output is due to the leakage energy
recovery circuit. HV flyback transformers usually have very high
leakage inductance (the part of the magnetizng inductance not coupled
to the secondary is leakage inductance) because distance between
windings is a major cause of poor coupling and you need distance for
isolation.

The leakage energy sloshes about in the primary causing all sorts of
mischief. This circuit recovers it and dumps it back into the primary.
It's unusual since the leakage energy is usually dumped back into the
bulk storage capacitor on the primary side if it's recovered by a clamp
winding or active clamp circuit.

A soft switching topology often uses the leakage inductance to reduce
transistion losses in the switch. Sometimes a discrete inductor is
added in series with the transformer primary to add to it. Another
bonus for the lousy coupling of the HV flyback transformer... no
discrete inductor needed. I think of this as electronic ju-jitsu.

The energy per half cycle (on the secondary) won't be equal so juggling
the capacitor values helps equalize the voltage stress.

Eh! I might be completely wrong. Simulating it would be the thing
but it's too much like work work and I'd need the transformer parameters.

At least that's how I think it works... Please let me know when you've
scoped the waveforms.

On Sep 10, 8:05*pm, Grumpy The Mule wrote:
Exactly right it is a gapped core. Once I git's a scope on I'll see.

But the voltage doubler they using is full wave doubler. Which means
they taking the positive and negative waves *to get 4000 or so volts
DC
Now the positive half they use a .0082 mfd for a filter and the
negative half they use a .0056 mfd filter both at 3000wvdc.

my guess is the quasi-push pull output is due to the leakage energy
recovery circuit. *HV flyback transformers usually have very high
leakage inductance (the part of the magnetizng inductance not coupled
to the secondary is leakage inductance) because distance between
windings is a major cause of poor coupling and you need distance for
isolation. *

The leakage energy sloshes about in the primary causing all sorts of
mischief. *This circuit recovers it and dumps it back into the primary.
It's unusual since the leakage energy is usually dumped back into the
bulk storage capacitor on the primary side if it's recovered by a clamp
winding or active clamp circuit. *

A soft switching topology often uses the leakage inductance to reduce
transistion losses in *the switch. *Sometimes a discrete inductor is
added in series with the transformer primary to add to it. *Another
bonus for the lousy coupling of the HV flyback transformer... no
discrete inductor needed. *I think of this as electronic ju-jitsu.

The energy per half cycle (on the secondary) won't be equal so juggling
the capacitor values helps equalize the voltage stress.

Eh! *I might be completely wrong. *Simulating it would be the thing
but it's too much like work work and I'd need the transformer parameters.

At least that's how I think it works... Please let me know when you've
scoped the waveforms.

The schematic I sent to msg actually refers to it as a flyback
circuit.
I am guessing one of the IGBTs is being used as a damper.

Jimmie



Jimmie

On Sep 10, 8:05*pm, Grumpy The Mule wrote:
my guess is the quasi-push pull output is due to the leakage energy
recovery circuit. *HV flyback transformers usually have very high
leakage inductance (the part of the magnetizng inductance not coupled
to the secondary is leakage inductance) because distance between
windings is a major cause of poor coupling and you need distance for
isolation. *

Exactly right I was in a hurry to get off to work and cut out the part
about the Damper diode and hold down capacitor. So yeah the diode
which looks like a varistor and may very well be a varistor, is the
push pull switch shorting out the induced trailing edge energy of the
IGBT. They use a .032 mfd across the primary along with the damper.
So the damper is switching on after the IGBT turned is off.

At least that's how I think it works... Please let me know when you've
scoped the waveforms.

Hopefully on the day 911, I get this powered up with low voltage. .
VK3HZ waveforms were at 50 hz trace sweep frequency so you couldn't
see the 30khz waveform.

73 OM
n8zu

On Sep 1, 7:48*pm, raypsi wrote:
On Aug 28, 8:39*pm, wrote:





On Aug 28, 4:02*pm, wrote:

On Aug 27, 12:40*pm, raypsi wrote:

finally came across an article by VK3HZ that describes how to make a
microwave oven inverter PS work, as a stand alone supply.
the link is:www.users.bigpond.net.au/dwsmith/hv_inverter.pdf

It's only regulated from the primary side. And you can make it put out
anything from 2000 to 4000 VDC. but at 1300 watts.

So all I have to do is load down the primary to fake out the regulator
into seeing 1300 watts, Or run class A.

The output or the input still has to be filtered

There's an opto coupler that has to see a 110hz square wave, according
to VK3HZ, that'll keep the supply running full tilt as long as there
is power supplied to the inverter.

73
n8zu

If the circuit can be driven from 555 osc perhaps the pulse width can
be controlled from a feedback voltage taken off the output of the
power supply.
I am thinking adding a small winding to the transformer rectifying and
filtering it and supplying this back to control the pulse width of
your osc.

JImmie- Hide quoted text -

- Show quoted text -

I was the OP of the origonal thread about the inverter power supplies.
I was actually more interested in learning about the design of the
power supplies so I could possibly build one from scratch. With the
right information this may be easier to do than to modify one from a
microwave oven. I am very grateful for the information. I have a
couple of the Panasonic power supplies unfortunately they dont work
but maybe I can repair them now that I have a schematic. Information
on the transformer would be a good thing to have as I am sure it could
be optimized for the desired output voltage and current needed for an
amateur amplifier.

With the current transformer on the front end I am guessing this may
be the feedback path for regulation. That is to say the power supply
is being controlled by the amount of current that is being drawn on
the input side of the power supply. If this is the case maybe this
input can be taken of the out put of the power supply and then the
supply could be voltage regulated instead of being power regulated.

Jimmie- Hide quoted text -

- Show quoted text -

Hey Jimmie

I suppose *that you could use the duty cycle feature of this supply to
control the output
but I'd need a bank of 450WVDC caps to supply filtering.
So say the power of the amp drops: the supply will compensate by
increasing the voltage
But with feedback I could drop the duty cycle thru the opto coupled
input. Thus causing a drop in voltage which the filter would handle.
By running the inverter at another lower duty cycle I can control the
output voltage.

I would suggest at least a bank of 16, 450WVDC for a little head room.
Plus that would take out the 120 cycle ripple.

73

n8zu- Hide quoted text -

- Show quoted text -

The mains rectifier could use some filtering too. Im thinking using
the caps out of some old PC power supplies

Jimmie

wrote in
:

The mains rectifier could use some filtering too. Im thinking using
the caps out of some old PC power supplies

Jimmie


Lots of good parts in a PC power supply...

Use the NTC inrush limiter resistors from the old PC supply
too so the caps don't pound the snot out of the on-off switch
and line recifier.

On Sep 12, 10:54*am, Grumpy The Mule wrote:
wrote :

The mains rectifier could use some filtering too. Im thinking using
the caps out of some old PC power supplies

Jimmie

Lots of good parts in a PC power supply...

Use the NTC inrush limiter resistors from the old PC supply
too so the caps don't pound the snot out of the on-off switch
and line recifier.

Yeah, I was planning on using pretty much the whole input section to
the PC power supply. The one I am looking at I think I can cut out the
whole circuit with a coping saw and mount it on some standoffs. This
would put the rectifiers and caps on a seperate little chassis and I
wont have to shoehorn in the 'lytics on to the inverter board.

I was noticing that the schematic for the 120VAC uwave inverters is
pretty much the same as the 240VAC inverter. I was expecting mains
input to be different. What I was expecting was a voltage doubler on
the 120VAC board since the 240VAC board used a bridge. This would mean
that the inverter section is designed to run off of anything from
150VDC to 300VDC . I need to take a closer look at just what are the
differences in the 120 and 240 inverters.

Jimmie


Jimmie