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Dual Voltage Input Power Supply

IP.com Disclosure Number: IPCOM000060851D
Original Publication Date: 1986-May-01
Included in the Prior Art Database: 2005-Mar-09
Document File: 2 page(s) / 31K

Publishing Venue

IBM

Related People

Maddock, D: AUTHOR

Abstract

A power supply includes a bridge rectifier, a pair of smoothing capacitors and a control circuit. When a 240-volt input is supplied, the bridge rectifier acts as a normal bridge. When a 110-volt input is supplied, this is detected by the control circuit which closes a switch to reconfigure the bridge on capacitors to act as a voltage doubling circuit. Thus the power supply will automatically produce roughly the same DC output voltage with an input of 240 V or 110 V. A long time constant circuit is included in the control circuit so that voltage spikes are ignored.

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Dual Voltage Input Power Supply

A power supply includes a bridge rectifier, a pair of smoothing capacitors and a control circuit. When a 240-volt input is supplied, the bridge rectifier acts as a normal bridge. When a 110-volt input is supplied, this is detected by the control circuit which closes a switch to reconfigure the bridge on capacitors to act as a voltage doubling circuit. Thus the power supply will automatically produce roughly the same DC output voltage with an input of 240 V or 110 V. A long time constant circuit is included in the control circuit so that voltage spikes are ignored. Reliable operation for a dual 240 V/110 V input power supply requires that: $on 240 volts the unit must not select 110-volt option $on 240 volts the switch on the unit must not select 110-volt option $on 240 volts missing mains cycles the unit must not select 110 volts $on 110 volts missing mains cycles the unit must not select 240 volts after the switch on the unit must not change state due to mains transients or other disturbances. D1, D2, D3, D4 are diodes to rectify the mains and charge capacitors C1 and C2. For 240-volt operation, switch S1 is open, the diodes are connected as a bridge, and capacitors C1 and C2 charge up so that A becomes, say, 380 volts. Diode D5 is forward biased, charging up capacitor C3. D5, C3, R3 become a peak detector which can be charged by D5 and discharged by resistor R3. The time constant of C3 and R3 acts as a storage memory so that several mis...