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adjusting frequency in LLC designs

Posted by: neonboy on

My understanding of LLC designs is that they use frequency to control output voltage in a fixed secondary turns transformer witha fixed resonant frequency.

Here is my problem:

- I need the supply to operate with a changing resonant frequency (fixed for each unit).

- I can't alter the turns ratio on the transformer and I need to set the switching frequency.

How can I use the Hiper PLC to do this ?

Can I change from an LLC mode to a different one ?

The PLC appears to be a continuous mode mechanism. Maybe I need discontinuous but the LCS model does not seem to work for high voltages(using the PI-expert s/w). Probably I am not setting something correctly...

 

Characteristics are:

- the lamp connected to the output has a capcitance, which cannot be determined beforehand, and is different for every device.

- The resonant frequency cannot be determined at manufacture only when deploying.

- The resonant frequency and output voltage both need to be independently adjustable to achieve the desired effect when deploying.

 - output wattage is in area of 80-150W

 - output voltage is in range 7000 to 20000 V

 - AC output. not required to be tightly regulated.

 - frequency range of output needs to be between 20kHz-100kHz  (PLC suggests 30k minimum)

 - magnetics can be large to enable sufficient power to be used. Typically something like

  TSC Ferrite International 81-33-16 core in 7070 material

end result looks like:

http://www.valerieloveland.com/lj/valerie/pinky.JPG

 

other examples:

http://www.boston.com/partners/greader/prfmkt/images/Wayne%20Strattman%20obstructing%20flow%20of%20molecule%20tree.jpg

http://nbmaa.files.wordpress.com/2012/08/dscn0170.jpg

 

Can you offer any advice please.

Comments

Submitted by PI-Neela on 10/10/2012

PLC frequency is controlled by VCO pin voltage. If you can modify your controller loop to control you VCO voltage, you can control your frequency. We don't have a promoted solution for that.

PLC can operate at 20kHz although suggested minimun frequency is 30kHz.