Output diode
ı need a 3000 V(İNVERSE VOLTAGE) output diode. but ı couldn't find anywhere this kind of diode in Turkey...I think to connect 3 diodes(1000V) in series..Does it cause a problem in my circuit?
Comments
Some years ago, I saw many diodes connected in series to achieve 50kv PIV. The trick to make them all act the same was to put high resistance and low capacitance in parallel with each diode. Sorry, I don't know more detail, but i expect the parallel resistance would be based on leakage current, and capacitance on junction capacitance.
i want to make a 40 watt flyback circuit but output voltage will be about 1 kV. I used PI expert program for simulation my circuit and i got some results. I used top244Y on my circuit but i couldnt see any voltage on primary or secondary wind on transformer. i couldnt find the problem. I used pri.enh. feedback. I am waiting for your advices for my circuit.
i used these components on my circuit;
output power is 40 W..
output voltage is 1000V..
transformer EI33...
fS= 66 khz
ı used TOP244Y.
VACmın= 195 V
VACmax= 265 V
fline= 50 Hertz
Vbias=28 Volt
Primary;
1n4007 diode bridge
Cın=47uF 400V
P6KE180 (180 volt zener diode) + BYV26C diode
2.2 Mohm resistor for L pin
(for 66 khz C and F pin connected)
There are 6.8ohm resistor (1/4 watt) and 47 uF 50 V capacitor between F and S pin.
There is 12kohm resistor between X and S pin
Bias;
BAV21 diode + 100nf 50V capacitor
15 ohm resistor
1n5251 zener to C pin (22 volt)
100 nf 50V capacitor
Secondary;
High voltage diode( about 8KV and 0.6 A) ultrafast + 47nF 2000V capacitor
I am waiting for your help,
Thanks...
Your design just isn't feasible using our devices. We specialize in high voltage AC/DC to low voltage DC conversion and our devices are well suited for this.
Your design has a very high output voltage and this makes transformer design with our devices nearly impossible. PI Expert will not allow an output voltage over 100 V to be entered because of the fact that designs with such high output voltages using our devices are not feasible.
The problem is that the turns ratio (VOR) is basically completely opposite for a high voltage output (few primary turns and many secondary turns) than what our devices are optimized for a low voltage output (many primary turns and few secondary turns). This causes flux density in the core to be very high or you must have a very high current limit on the device.
Unfortunately our devices are not an easy solution for your problem. We do not have the experience in these types of designs to give much practical advice. If you decide to pursue this project please let us know how it goes! Thank you!
-PI-Wesley
Wesley,
I have a 600 VDC supply working pretty well; I didn't design the xfmr. The only difficulty I'm having is peculiar to my app, not the 600 VDC; when I switch the FB to deliver 140 VDC at light load instead of 600 VDC, the supply loses regulation. I posted this problem yesterday. I'm thinking that I may be able to solve it by switching in a load when operating at 140 VDC, and switching the load out at 600 VDC; see attached. Or I may try to add a series regulator for the 140 VDC in some config that gets bypassed for 600 VDC. More to come...
i am sorry i gave wrong info to you. i used PI Xls program for simulation. this program allow high voltage simulation. it gave us transformer's properties. we made transformer and we bought the components for our circuit.
Could you please post your PI Xls spreadsheet and/or the transformer design you are using?
-Wesley
http://www.powerint.com/sites/default/files/TOPGX Flyback Design1.xls
http://www.powerint.com/sites/default/files/TOPGX Flyback Design1.xls
Let me correct my previous response, it is possible but it is outside of our expertise and I personally have no experience with high voltage output designs.
However if you are not seeing any voltage on the transformer I would check that your secondary or bias winding is not shorted.
Also could you provide details on this high voltage diode you are using? Could you provide a datasheet? What is the diode's reverse recovery time? Again if it is very high it could be making the secondary look like a forward winding and thus the core would store no energy and the supply to not work.
Lastly could you explain in more detail by what voltages you are seeing exactly and where you are measuring them and with reference to what?
Thanks and I'll do my best I can to help!
-Wesley
http://www.powerint.com/sites/default/files/TOPGX Flyback Design2.xls
Hi,
An output diode with a PIV of 3000 V is very high! Why do you believe you need such a diode? Are you using our PI Expert/ PI Xls design software?
With such a large PIV I don't think your design is viable. Could you please provide details so we may verify the design together.
HOwever yes you can usually connect 3 diodes in series to get the necessary PIV rating but do not expect the specifications of the three diodes in series to be the same of as one of a 3000 V rated model.
Good luck and please provide more information. Thanks!
-PI-Wesley