Low power PWM controller, possibly the 555 (flame war coming)

as an isolated buck.....

the web.

voltage is not steady 20V, but can drop very fast, which would pose a problem with half-bridge solution (capacitor midpoint slewing slowly) and since access to the current is easy (sense resistor)

later on.

duty cycle (45%), but peak current is detected by the comparator which in turn resets the PWM (input to PWM module) before reaching 45%.

feedback to the primary side. (not shown). Larger caps needs to be placed on the output to ease the response time of the regulation loop (microcontroller measured error voltage)

supply, but have not yet found off-the-shelf magnetics that facilitates this.

the diodes or the FETs are mounted on the output, the FETs are for syncronous rectification)

off-the-shelf magnetics in small sizes are available.

Come on now, I thought you were going to play nice.

Eleven years ago, when I first posted it, I also included a complete description of how it works, including inductor value. Recently I even posted a photo of that inductor, when someone was complaining they couldn't get a 5mH inductor rated to 5A.

The circuit was first incorporated into automobiles around 1972, when HV (350V) bipolar transistors had beta ~3. ...Jim Thompson

as an isolated buck.....

the web.

voltage is not steady 20V, but can drop very fast, which would pose a problem with half-bridge solution (capacitor midpoint slewing slowly) and since access to the current is easy (sense resistor)

later on.

duty cycle (45%), but peak current is detected by the comparator which in turn resets the PWM (input to PWM module) before reaching 45%.

feedback to the primary side. (not shown). Larger caps needs to be placed on the output to ease the response time of the regulation loop (microcontroller measured error voltage)

supply, but have not yet found off-the-shelf magnetics that facilitates this.

the diodes or the FETs are mounted on the output, the FETs are for syncronous rectification)

off-the-shelf magnetics in small sizes are available.

Crikey! I responded without looking... it _does_ have values.

The NPNPower device was a custom Delco part... BVceo=350V, beta >= 3 at 5.5A.

My trickiness was sensing current in the emitter and deriving the collector current, accurate over temperature and process variations. ...Jim Thompson

as an isolated buck.....

the web.

voltage is not steady 20V, but can drop very fast, which would pose a problem with half-bridge solution (capacitor midpoint slewing slowly) and since access to the current is easy (sense resistor)

later on.

duty cycle (45%), but peak current is detected by the comparator which in turn resets the PWM (input to PWM module) before reaching 45%.

feedback to the primary side. (not shown). Larger caps needs to be placed on the output to ease the response time of the regulation loop (microcontroller measured error voltage)

supply, but have not yet found off-the-shelf magnetics that facilitates this.

the diodes or the FETs are mounted on the output, the FETs are for syncronous rectification)

off-the-shelf magnetics in small sizes are available.

I meant my circuit, not yours.

known as an isolated buck.....

to the web.

voltage is not steady 20V, but can drop very fast, which would pose a problem with half-bridge solution (capacitor midpoint slewing slowly) and since access to the current is easy (sense resistor)

later on.

duty cycle (45%), but peak current is detected by the comparator which in turn resets the PWM (input to PWM module) before reaching 45%.

feedback to the primary side. (not shown). Larger caps needs to be placed on the output to ease the response time of the regulation loop (microcontroller measured error voltage)

supply, but have not yet found off-the-shelf magnetics that facilitates this.

the diodes or the FETs are mounted on the output, the FETs are for syncronous rectification)

off-the-shelf magnetics in small sizes are available.

OK.

I actually used such a circuit when I was ~18 years old, to drive a speaker in my car using one of those old Delco Germanium "hockey-puck" devices, running class-A. Ran hotter-then-hell, but my father-in-law-to-be machined me a custom-fit heatsink ;-) ...Jim Thompson

it looks interesting. I have not been able to find any information on this exact topology, but it looks like a LLC converter without the high side switch. Do you have any more information on this?

Regards

Klaus

Max845 takes up to 5 mA just for the chip and that's all my power budget and more to it.. Nice chip, though, I might find another one with lower current consumption. Anyway, how do they avoid flux walking..... The dead time they have inserted?

I could run at a 3.3V which I o generate, but then I have two converters in series, and that's bad for efficiency. Also, at 3 volt the output diodes means I loose a lot of efficiency.

Regards

Klaus

Hi, Klaus,

Are you referring to this?

It's just an attempt to separate the DC and AC (ie, energy storage and energy transfer) elements in a flyback switcher. So that you could use off-the-shelf magnetics, maybe, like a cruddy power inductor and an ungapped transformer.

You couldn't find any references to this exact topology because I just made it up! But I'm sure it's been invented and used somewhere, somehow, before now. It's sort of like a Sepic, only it does have leakage inductance to deal with.

John

exact topology, but it looks like a LLC converter without the high side switch. Do you have any more information on this?

Yes, the compound you drew. It's a very nice circuit and avoids the need to drive a high Side FET and has zero voltage switching possibilities. Maybe a circuit added to monitor the ringing and turn on the FET at the right time to lower losses

Regards

Klaus

The tubophiles have been calling it "parafeed" for years. I forget what RDH4 calls it. It's probably older still.

Tim

Except that this is a flyback switcher, not an audio amp.

Except if you overdrive an SE amplifier. Now what? ;)

Tim

Now come up with an idea of your own.

"John Larkin" wrote in message news: snipped-for-privacy@4ax.com...

Well that was easy. You really are a terrible troll, you know that?

Tim

This is sci.electronics.DESIGN. So design something.

more to it.. Nice chip, though, I might find another one with lower current consumption. Anyway, how do they avoid flux walking..... The dead time they have inserted?

series, and that's bad for efficiency. Also, at 3 volt the output diodes means I loose a lot of efficiency.

have you looked at linear? they have lot of sub mA micropower buck/ boost/ext.

or something like

-Lasse

PWM control.

there a PWM chips out there with low operating current. Sofar I found the TPS5110 with sub mA current consumption:

current PWM.

probably be 1:1 so I can use off the shelf types approved for EN69650.

Our little ISDN transformers, from Talema, are good for EN60590, whatever that means. They have 4 windings, 1:1:2:2. That has all sorts of possibilities. Like make a blocking oscillator flyback converter (near zero control power needed!) with some simple, low current opto feedback. A suitable SOT23 mosfet would cost a few cents.

more to it.. Nice chip, though, I might find another one with lower current consumption. Anyway, how do they avoid flux walking..... The dead time they have inserted?

series, and that's bad for efficiency. Also, at 3 volt the output diodes means I loose a lot of efficiency.

That looks like a very interesting part indeed, would almost match my needs. Only downside is the price, over 2USD in large quantities, but it saves many parts from my schematics :-)

Regards

Klaus

power PWM control.

there a PWM chips out there with low operating current. Sofar I found the TPS5110 with sub mA current consumption:

current PWM.

probably be 1:1 so I can use off the shelf types approved for EN69650.

Do you have a part number for that part?

We use royer converters a lot, in designs that needs to be self sustained. Would probably be a good choice here too, thanks for the suggestion.

Regards

Klaus

power PWM control.

there a PWM chips out there with low operating current. Sofar I found the TPS5110 with sub mA current consumption:

low current PWM.

probably be 1:1 so I can use off the shelf types approved for EN69650.

Would probably be a good choice here too, thanks for the suggestion.

We use zillions of SMJ-140B. The SHJ series has better insulation, I think.

Nice little parts. They might manage 100 mw in flyback mode. We push watts through them, into isolated DAC channels, with push-pull/forward drive, a couple of 2N7002's driving a center-tapped primary.