Hi. I'm looking for the schematic or any technical information on the optionnal Michell HR supply for their DC motor turntable. it is supposed to be a great upgrade to the original small DC wall adapter. This HR supply is quite expensive. It contains what is called "Never-Connected" supply. After a search on the net I collected these informations:
1-The HR supply uses "Active-Rectification" followed by a solid state regulator, possibly a standard LM317. It has a variable DC 9V output, so the DC motor speed can be adjusted. It has High current capacity, specs unknown, possibly higher than the standard wall adpater 9V dc supply. It is suing also a toroidal transformer. See image.
2-The HR supply image gives a few clues about is circuitry. We see rectication diode, possibly Hi-Speed recifiers, and possibly two low ESR caps. The "Active rectification" is probably use after the first diode rectification. It is using possibly the MAX797 IC's and a FET as active rectification part. The LM317 or LT variant (low drop-out) rectifier and the FET are probably mounted on the supply's back.
3-The "Never-Connected" principle is basicly a DC supply using "Active rectification". This principle well known for numerous years use active FET switch to rectify the AC voltage. The advantge are:
Linear (sinusoidal) current and voltage load
THDU, THDI small
Two way energy flow (source-load-source), energy recuperation
In case of active rectifier breakdown can the device operate normally as an uncontrolled rectifier
cosf regulation
Output voltage stabilization
It is probably a good start to use this desing:
-Toriodal transfo + high speed rectifiers + Panasonic FC low ESR caps, small MOV at the input of the transfo.
-MAX797 + FET active rectification, set at maybe 12V
-Final LT1085 low drop-out adjustable regulator, set at 9V +/-5% potentiometer adjustement (for speed fine tuning)
-Small FC cap at the ouptput with MKS Wima bypass cap (as the image is showing)
Any comments are welcome...
1-The HR supply uses "Active-Rectification" followed by a solid state regulator, possibly a standard LM317. It has a variable DC 9V output, so the DC motor speed can be adjusted. It has High current capacity, specs unknown, possibly higher than the standard wall adpater 9V dc supply. It is suing also a toroidal transformer. See image.
2-The HR supply image gives a few clues about is circuitry. We see rectication diode, possibly Hi-Speed recifiers, and possibly two low ESR caps. The "Active rectification" is probably use after the first diode rectification. It is using possibly the MAX797 IC's and a FET as active rectification part. The LM317 or LT variant (low drop-out) rectifier and the FET are probably mounted on the supply's back.
3-The "Never-Connected" principle is basicly a DC supply using "Active rectification". This principle well known for numerous years use active FET switch to rectify the AC voltage. The advantge are:
Linear (sinusoidal) current and voltage load
THDU, THDI small
Two way energy flow (source-load-source), energy recuperation
In case of active rectifier breakdown can the device operate normally as an uncontrolled rectifier
cosf regulation
Output voltage stabilization
It is probably a good start to use this desing:
-Toriodal transfo + high speed rectifiers + Panasonic FC low ESR caps, small MOV at the input of the transfo.
-MAX797 + FET active rectification, set at maybe 12V
-Final LT1085 low drop-out adjustable regulator, set at 9V +/-5% potentiometer adjustement (for speed fine tuning)
-Small FC cap at the ouptput with MKS Wima bypass cap (as the image is showing)
Any comments are welcome...