[SOLVED] Very fast power Schottky diode

[htg]

Are there any power Schottky diodes with trr no more than 1 ns,
and preferably no more than 300 ps?
I need to rectify many kW cost-effectively at 200 MHz, at least at 25 MHz.

 

[malik_zohaib]

what about bat series like bat41 trr is about 5ns.

also check it out
Central Semiconductor

 

[htg]

bat41 is a 100 mA diode. If I want 100 mA, I can use MBD301 with trr=100ps.

 

[FvM]

If I want 100 mA.

You did not tell a current specification.

 

[malik_zohaib]

yah you did not tell any specification rather than trr

 

[htg]

I said "Power Schottky diode", not "small signal Schottky diode". You should know the difference.

 

[malik_zohaib]

opppppppppps i did not see the word "power". i dont why??

 

[FvM]

I said "Power Schottky diode", not "small signal Schottky diode".

It's O.K. to post vague questions, but then you shouldn't complain about the answers...

 

[htg]

I can use variety of combinations of Vrr, If as long as it can rectify at least 50W, and I would like trr <= 1 ns.

 

[FvM]

I forgot to mention a more general specification problem. By design principle, schottky diodes do not have a recovery time. The majority carrier lifetime is in the order of 100 ps maximum and doesn't count here. Schottky diodes have a switching time though, caused by junction capacitance.

 

[htg]

Generally trr values are listed in the range of 100ps to tens or hundreds of nanoseconds.
I need to rectify many kW in a cost-effective way, preferably at 200 MHz, at least at 25 MHz.

 

[jiripolivka]

Hello htg:

I can follow your ideas, quite phantastic, from physics to huge low-frequency waveguides. Interesting!
I have used and tested quite a lot of various diodes for rectennas but so far I have NOT seen any diode usable for a high-power rectification at 25...250 MHz or higher.
On the other hand I noticed that in DC/DC converters, to achieve high efficiency, the designers use not only high frequency (from 10 kHz now up to 20-30 MHz), but instead of lossy P/N junction rectifiers, now FETs are used as synchronous rectifiers. Those FETs have fast responses and channel resistance under one Ohm, so they are much better than Schottky diodes. Consider this, please. It can be quite easy to use a small Schottky diode to generate a control signal for "heavy" FET rectifiers in a sync mode.

 

[htg]

I thought about using FETs, but according to the data I found, they cannot withstand reverse voltages above about 1 V, - I need more, I think (even though I can use a transformer and have low voltage, I think 1V is impractical at kW power levels).

 

[FvM]

they cannot withstand reverse voltages above about 1 V

FET's as synchronous rectifiers are always operated reverse biased.

Usage of FET's instead of Schottky diodes isn't for higher speed, only to reduce forward voltage. At high frequencies FETs and schottky diodes have the same problem, the junction respectively ds capapacitance. I don't think that FET's offer considerable advanteges in this regard. The capacitance has be handled in your circuit.

 

[htg]

Schottky diodes offer reasonable Vrr. So what about reverse voltages for MOSFETs?
If I could find a high-current analog of the Schottky diode MBD301 (100mA, 30V, trr=100ps), it would solve my problem.

 

[jiripolivka]

I think you are not right: ordinary switching FETs handle 60-100 V reverse and there are types that can handle more. Then there are V-channel FETs used in kilowatt applications up to 50 MHz. Maybe there is a good selection to try synchronous rectifiers with a better efficiency than a Schottky.

I am looking forward to a new rectifier type for microwave rectennas. Many people dream about them, so far nothing works as desired...

 

[FvM]

I think, you didn't understand the trr and schottky diode point. They don't show delayed reverse recovery, because they don't have minority carriers. But they have junction capacitances.

 

[htg]

..ordinary switching FETs handle 60-100 V reverse and there are types that can handle more...

Are you talking about MOSFETs?
Can you name just one that can handle 60V reverse (preferably fast enough to work at 200MHz)?

---------- Post added at 05:40 PM ---------- Previous post was at 05:37 PM ----------

I think, you didn't understand the trr and schottky diode point. They don't show delayed reverse recovery, because they don't have minority carriers. But they have junction capacitances.

I need 70% rectification efficiency at 200 MHz. I do not think junction capacitance is the problem. According to the data I've seen, trr is in tens of ns or worse and that is the problem with the power Schottky diodes.

 

[FvM]

I didn't find any power schottky diode with a trr specification. Where did you see it?

P.S.:

Can you name just one that can handle 60V reverse

Possibly a misunderstanding. A MOSFET used as rectifier will be reversed biased in on-state and forward biased in off-state.

 

[htg]

Regarding trr: I did Google search for power Schottky diode and looked through many results.

MOSFET as a rectifier: I thought that the body diode in a MOSFET will always conduct when the MOSFET is reverse-biased, so I do not see why I would need to switch it on.