basic page about the used Powersupplies 3     Page No.:D04-3
 
      WARNING : At the following circuit diagrams i have marked up with light red shading the so called
                    "primary side" of the supply. In this areas there are voltages up to 400 Volt present!
                            Such voltages are lethal dangerous !
                    Never access this areas with present "live Voltage" ( i.e. supply "powered up" ) !
                    Red highlighted areas may only be accessed while powersupply is disconnected
                    from main powersource ( disconnected from powercord ) !
                    Never attempt this areas without ensuring the demanded precautions of safty !
                    Only experienced Users with advanced knowledge and successfully solved safty training
                    may work at this red highlighted areas !
                    Read red colored text with safty warnings ! Do not ignore this warnings !
                    Ignoring this warnings may cause electric schock with lethal results !

At this point i want to step back again to the primary section and compare a unit working with 110 Volt (like marked below at A )
to a unit working with 220 Volt ( like marked below with B ). If the Unit for 110 Volt like marked below with A has 2 time 110 Volt
coils like in the picture then itīs rather well possible to change such a device to use with 220 Volt - BUT: If the device has not at
least 2 times a 110 Volt coil but instead ONLY ONE 110 Volt coil - THEN IT WON`T BE POSSIBLE TO CHANGE SUCH A SUPPLY
TO USE WITH 220 VOLT !

Another possible handicap that disables such switching might be caused by use of components that wonīt handle higher voltage-
ratings ( like for example electrolytic capacitors in 110 Volt supply limited to 200 Volt maximum ). In 220 Volt supplies the capacitors
must be able to handle voltages up to Voltagelimit of maximum of 400 Volt. At regular capacitors in 110 Volt supplies there might be
used capacitors with limitation to 160 Volt while at 220 Volt supplies that same capacitors must be at least defined to limitation of
350 Volt.

And similar statements must be made also for the resistors and other devices ( like the transistors and diodes ).

So in general there is a valid statement: In most cases itīs not possible to modify a supply designed
for use with 110 Volt to use with 220 Volt !

If a change of use is possible - it is in general only possible the other way around
- Itīs rather more possible to alter a unit designed for use with 220 Volt to be able to work with 110 Volt !
But also in that case two statements are valid:
The modification to the lower voltage is only possible if:
either the Transformer has at the 220 Volt coil a splitconnection at exactly half of the coil resulting to the chance to split
that coil to 2 coils working with 110 Volt or if the primary section of the transformer has 2 coils each 220 Volt
and BOTH HAVING A SPLITOFF CONNECTION AT EXACTLY HALF OF THE COIL resulting to the chance of splitting that 2
coils of 220 Volt to be split to 4 coils each for 110 Volt ( like in picture 2 below of the the following picture 1 )
- or there must be made a modification at the primary section at the input of 220 volt to accept
110 Volt and then doubling the voltage up to 220 Volt internal in the entry area by use for
example of a alternate entry stage ( by use of voltage doubling like DELON - this will be treated
in a later section of this page ).

In general this will be the only valid and correct working version of changing / altering a supply
unit from 220 Volt to 110 Volt and then using internal of the supply in fact 220 Volt.		  
       
      Another reason for problems of changing the used input voltage of a switching powersupply is the "winding-ratio".

( just to prevent a "shitstorm" from experienced engineers and technicians a remark here: of course you may argue that i have
not used in the following section the very correct formulas for the math performed to calculate the correct amount of windings -
but due to the fact that this page is dedicated to amateurs and hobbyists too i wanted to keep the math simple and therefor
the examples use very basic math without offset and correction of losspower-compensation and other factors ! The math is kept
very basic just to explain difference to transformer with windings at one side with 110 Volt and other side with 220 Volt with very
rough and basic calc to "proportions" )

So now for very basic example of the "winding-ratio":
 
If i use 110 volt at transformer: If i use 220 Volt at transformer :
The ratio of a 12 Volt coil will be 9,16 or in very basic calc of windings:
the amount of windings
at primary 110 Volt section            at secondary 12 volt section:
1100 windings                         =>    120 windings
 		 The ratio of a 12 Volt coil will be 18,33 or in very basic calc of windings:
the amount of windings
at primary 220 Volt section        at secondary 12 volt section:
1100 windings                       =>  60 windings
The ratio of a 5 Volt coil will be 22 or in very basic calc of windings:
the amount of windings
at primary 110 Volt section           at secondary 5 Volt section:
1100 windings                         =>   50 windings
 		 The ratio of a 5 Volt coil will be 44 or in very basic calc of windings:
the amount of windings
at primary 220 Volt section         at secondary 12 volt section:
1100 windings                        =>  25 windings
If i would use a 110 Volt transformer without change
of the ratio at 220 Volt would result to the following voltage:
 		 If i would use a 220 Volt transformer without change
of the ratio at 110 Volt would result to the following voltage:
1100 windings                         =>    120 windings
would result to a voltage of:        secondary 24 volt !
 		 1100 windings                       =>  60 windings
would result to a voltage of:      secondary 6 volt !
1100 windings                         =>   50 windings
would result to a voltage of:        secondary 10 volt !		 1100 windings                        =>  25 windings
would result to a voltage of:       secondary 2,5 volt !


This would result to the fact that without change of the transformer in theory
- a 110 volt transformer operating at 220 Volt would issue at the secondary section double voltage than calculated
- and a 220 Volt transformer operating with only 110 Volt would issue at secondary section only half of the calculated voltage !
BUT IN FACT at first example the transformer would overheat ( like operating with partial shortcircuit ) and getting destroyed
and in second example the switching powertransistor gets destroyed  due to the higher transmission of current exceeding the
limits of the powertransistor !
 

  
       
   Before explaining the modification according to Delon lets first take a general short view to regular common part of primary
voltage input section: The picture below displays at a) a extrem primitiv ( rather uncommon used ) rectifying section with only 2 diodes.
Picture B) displays the rather common used rectifying section with so called "bridge-rectifier" ( which is replaced in some power supplies
by use of 4 diodes. In general of such supplies there is only one (!) electrolytic capacitor instead of the displayed 2 capacitors C+ and C-.
therefor in such supplies there is no junction point between C+ and C- and no connection to 0 (!) . Instead in common supplies then -Ua will
be used as 0 Volt ( i.e. GND = ground ) and at +Ua there will be the rectified DC Voltage. In the rare case if a supply is "switchable"
then there will be really 2 electrolytic capacitors with exactly same capacity and same voltage limit and the junction point will be leading to
the voltage selection switch. If there is only one electrolytic capacitor it must be replaced by 2 capacitors of same capacity and same voltage
limit like displayed in the picture to make the powerunit switchable.
         
      Important safty warning : In both kinds of supplies the "ground"
may not be connected
and primary ground is possibly lethal dangerous !
Itīs therefor strictly recommended to take safty  precautions
by using a isolating transformer between output from wall and powerunit !

Modification by doubling input voltage  115 Volt at internal primary section to 220 volt
( according to Delon ):
In picture C) there is the very uncommon version of simple rectifying the voltage in the primary section according to picture A).
Picture D) shows the rather more often used solution of a "bridge rectifier" according to picture B) above -BUT WITH SLIGHT
DIFFERENCES resulting to other behaviour of the circuit ! While in picture 3 at B) the diodes D3 and D4 are blocking AC voltage
towards the negativ connection of the electrolytic capacitor C- in the picture 4 at section D) the blocking diodes towards the
electrolytic capacitor C2 are D2 and D4 ! And in this picture 4 there is a wire added between junction of negativ pol of C1 and
positiv pol of C2 and junction of the 2 added resistors R1 and R2 !
This trace between the input at AC input of Ue and wire a) and junction between
wire a) and junction at resistors R1 and R2 may not be connected to any other part in the powersupply !
The added resistors R1 and R2 are just to ensure the "balancing" of the voltage between DC voltage between +Ua and wire a)
and wire a) and 0  ensuring that at the connections from C1 and C2 there are same amount of voltage
( exactly half amount of voltage 0 to +Ua = 1/2 +Ua = 110 Volt DC )  !
And of course C1 must be exactly same kind of electrolytic capacitor like C2 in capacity and voltage limitation
as well as R1 must be exactly same kind of resistor like R2 in resistance and powerconsumtion !		  
       
      So even if the modification displayed above is practical solution several aspects must be kept in mind:
1. There are several minor differences between rectifying with only 2 diodes and true bridge rectifying :
     a) less amount of loading waves contra higher amount of loading waves ( resulting to other frequency calculations )
     b) higher amount of disturbing "noise voltage" compared to less "noise-voltage" and alteration of the filters
2.There might be some changes required to the security / protection circuit to fit demanded needs :
    a) by different parts of traces related to grounding and isolation 		 
         
       
   
   		   


 

 

 
         
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