Relative to an AC output, the 5 V source can make only a 5 V p-p AC input (again, 100% efficiency) to the converter, or 1.77 Vrms. This leads to a turns ratio of 850:1.
A photoflash trigger transformer comes to mind, but that 1/4" height will be a problem there, too. Would a non-isolated flyback circuit without an output rectifier work for your (secret) load?
ak
First, I need to thank all who replied. Unfortunately (for me), I thought the forum would advise me if there was a new reply to my original post. So, I just saw the replies, please believe me...I didn't intentionally ignore those who replied to the initial post!
Lots 'o water been undah dah bridge since my original post. Here's an update with relaxed design criteria and additional information.
Since the original post, I did additional research and found that I could use a higher input current supply. So, I have 4 volts (LIPO) at 2 amps of input power available....2 amps max at startup and ~1A actual operating current. I have a larger enclosure also, a cylinder at .9 inches wide by 2 inches long is suitable. I can get by with 500 volts peak to peak output but it must be AC or a modified square wave output. The supply DOES NOT need to be constant duty, 3 or 4 seconds of output with 5 or 10 minutes of off time is ok. I can tolerate some ringing at the transitions.
The closest off the shelf solution is a LCD inverter. I ordered a surplus unit that is small and compact and that produces up to 3KV at up to 4 mA. It works fine, except the driver chip doesn't have technical information available. It operates fine at approximately 25 kHz, but it is to bulky. And, it needs a minimum of 1 mA of load current in order to operate. If I could make a higher frequency transformer (which is much smaller physically), I might be able to build my own driver circuit that is far smaller than the LCD inverter unit that I am experimenting with. However, since the specs for the Chinese made LCD inverter aren't available, there is little chance that I can increase it's operating frequency significantly. I would like to have a low profile transformer that operates at 1 to 2 MHz rather than 25 KHz. I am very familiar with high voltage (ham radio operator) and microelectronics soldering/rework and with custom transformer winding.
My load will vary from an arc down to 1 megohm or so, my preference is not to use a royer or similar type of power oscillator that utilizes a feedback winding on the transformer since these types of drivers don't do well with a load that varies as much as mine does. Regulation is not critical, but it is desirable to have some form of crude/minimal regulation.
I'm currently looking for a ferrite that is suitable for a 1 to 2 MHz transformer which is easier said than done::>
Any suggestions are appreciated.