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Registered Member #60260
Joined: Fri May 27 2016, 06:35PM
Location:
Posts: 14
For development of an electrostatic headphone amplifier, I want to regulate a Mazzilli ZVS driver driving an CRT Flyback to ~1 kV. What would be the best way to do this?
I thought of two ways: -Separating gate drive and power input voltage and adjusting the power input voltage with a high power buck controller -Introduce pulse skipping by using a JFET to prevent the next pulse from starting when the secondary voltage exceeds a threshold
I'm not sure what would be the best way for feedback, a separate winding on the flyback or optocoupled from the HV side.
But maybe I'm barking upon the wrong tree and I'm missing the obvious and easy way to do this. Please enlighten me if so!
Registered Member #162
Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140
I would consider the power source first, which may determine your design. I guess 5V USB or 3v6 lithium, and of course as effcient as practically achievable. I'm out-of-touch but something like a regulated flyback h.v. + SiC modulating transistor ??
Registered Member #60260
Joined: Fri May 27 2016, 06:35PM
Location:
Posts: 14
woodchuck wrote ...
FWIW, there certainly are smaller and cheaper ways to generate 1kVDC. They are also quieter (in terms of both ripple and EMI).
Probably, but I would like the supply to scale to ~10 kV, for if I decide to use it for large panel speakers. However, I'm interested in alternate topologies. What would you suggest here?
Sulaiman wrote ...
I would consider the power source first, which may determine your design. I guess 5V USB or 3v6 lithium, and of course as effcient as practically achievable. I'm out-of-touch but something like a regulated flyback h.v. + SiC modulating transistor ??
An old laptop power brick was my first idea, but both Li-ion batteries and usb would be nice as well.
Registered Member #235
Joined: Wed Feb 22 2006, 04:59PM
Location:
Posts: 80
Your first idea is how it is generally done in literature. Using a buck converter to effectively limit the dc-link voltage.
Search for "current-fed push-pull resonant inverter"
You can also use 2 dc-link inductors in series with the transformer winding, instead of using 1 dc-link inductor and center-tappingthe transformer. This has been demonstrated on this site and in many papers.
Registered Member #2431
Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639
Molenaar wrote ...
How does load influence the secondary voltage?
This is a complicated question. But a small flyback from a small TV like the portable ones, or 8" screen one, would supply more than 10kV, which could then be dialed back for 10kV at you desired current. I would think that electrostatic stuff doesnt work well at just 1kV, but that depends of course.
These previous projects of mine may help. They're over kill at 46 and 52kV, but layout the issues for you. Feedback regulation is definitely possible. I recommend optical feedback, though i haven't mastered it myself, the feedback winding on a common core has poor cross-regulation issues in your application.
Pulse Frequency Modulated (PFM) Flyback Transformer.
If it is 1kV, then use an inductor or normal transformer at high frequency and feedback regulation.
I reallly dont do the "Mazilli / ZVS / ZCS" thing so my experience is mostly with conventional switching SMPS.
Registered Member #60260
Joined: Fri May 27 2016, 06:35PM
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Posts: 14
I don't know whether 1 kV will be enough, but my valves can handle 20 kV, so scaling should be fine. I also have a pulsed power rated 40 kV rated capacitor which could stabilize the output.
Why does a feedback winding have poor performance in this case? I was hoping to be able to use feedback from a dedicated winding and feed it to the buck converter which supplies the ZVS driver.
I could also use a resistor divider (I have 10 200 Meg 7,5 kV resistors) for feedback from the secondary, but I'm weary of relatively high power dissipation that way, since all current used by the feedback element (e.g. Led driven by voltage to frequency converter) will also pass through the HV resistors.
Registered Member #2431
Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639
Molenaar wrote ...
I don't know whether 1 kV will be enough, but my valves can handle 20 kV, so scaling should be fine. I also have a pulsed power rated 40 kV rated capacitor which could stabilize the output.
Why does a feedback winding have poor performance in this case? I was hoping to be able to use feedback from a dedicated winding and feed it to the buck converter which supplies the ZVS driver.
I could also use a resistor divider (I have 10 200 Meg 7,5 kV resistors) for feedback from the secondary, but I'm weary of relatively high power dissipation that way, since all current used by the feedback element (e.g. Led driven by voltage to frequency converter) will also pass through the HV resistors.
you can try the feedback winding, but they tend to have errors. youll have to look up cross-regulation issues. this is typically the difference between a good ATX power supply and a poor one.
Registered Member #58522
Joined: Tue Mar 15 2016, 08:33PM
Location:
Posts: 50
You might want to look at
This is a 1500 V, 1 A power supply to run a tube amplifier. It looks like it uses a divider network and zener diode to set the feedback voltage set point. It may be more complicated than you want to do.
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How to regulate Mazzilli ZVS driver?
