20W offline flyback ........and 100W Triac drive, together.

Hi,

My boss just recently asked me to design and layout a 20W SMPS (offline flyback , vin= 85-265VAC, Vout = 36V).

This afternoon he came by and told me that the company also need a 100W variable speed Triac drive in the product, and so please could i put this on the 20W PCB too.

Would i be right in saying that 20W offline flybacks and 100W Triac VSD's don't share the same PCB very well?

Would i be right in saying that the 100W triac drive will need a considerable amount of mains filtering, and would best go on its own PCB?

The product is a shower with a pump added (for the VSD), and it has stepper motor hot and cold valves........the 20W SMPS is for powering the steppers and some LEDs

(the VSD will just have three separate speeds which will be 'chosen' by a microcontroller via opto-triac trigger.)

I've seen more divergent design blocks sharing a PCB... Very well or not, it's mainly a practical question of instrument design. I can imagine some reasons for a single power board design. Form factor may be a reason against it, however.

A triac phase angle controller would use the motor inductance to reduce harmonic currents. Then there isn't much more filtering required (according to present EMC rules), perhaps a X capacitor in addition to the triac snubber circuit.