This is an attempt to use peltier modules direct from the 120VAC mains. 170VDC rectified and smoothed.
I will double insulate as the supply isn't isolated.
So far I am looking at using FET PWM with an input capability of 200VDC to generate around a 4A avg. with soft start current. I plan on using (3) series mounted 12V, 60W (peak) peltier units. This means a 0.1 ohm current sense feeding into a low pass and then the comparators.
The challenge is the control circuitry operates at lower voltages, eg. a TL494 PWM driver is good to about 40V.
The Tl494 might pull perhaps 20mA to operate so a resistance divider could drop the 170VDC supply to 1/10 to provide the TL494 power. Perhaps 3.5W additional heat load as a result.
A stock PC supply is a bit too bulky for the application space overheads.
That's n option. But triacs are chopping a 60Hz signal, then that'll get rectified and smoothed. Might have a high LF ripple at the current limiting end which makes a current sense control prone to swings.
I was thinking of rectifying and smoothing at the high voltage side (like a PC PSU) , then using a TL494 PWM (say 50Khz) direct into the Peltiers via the current sense. A low pass filter can then supply a stable average (current sense) voltage signal for the comparators. A 5A fuse in line with the Peltiers for protection.
If it was me given TEC module are pretty forgiving devices I would just capacitive couple the TEC's to the mains power. Once AC capacitor, one bridge rectifier one DC electrolytic capacitor and one resistor to bleed off the charge on the AC capacitor for safetys sake.
If it was me given TEC module are pretty forgiving devices I would just capacitive couple the TEC's to the mains power. Once AC capacitor, one bridge rectifier one DC electrolytic capacitor and one resistor to bleed off the charge on the AC capacitor for safetys sake.
60W 12V 5A units. Using 3 was for a lot of thermal margin and losses.
I'll go with 2 x 60W units at first to see if they're adequate for the job. I'll have to mock up the application, but I do have enough on hand to do it before I purchase the 120W PSU.
Way too much. To power a 4 - 5 amp 36 volt load off of a 120 VAC 60 cycle power source you would need about 16 - 21 ohms of impedance which works out to around 135 - 165 uF which is easily doable with common motor or HID lighting ballast capacitors.
Way too much. To power a 4 - 5 amp 36 volt load off of a 120 VAC 60 cycle power source you would need about 16 - 21 ohms of impedance which works out to around 135 - 165 uF which is easily doable with common motor or HID lighting ballast capacitors.