Browse Prior Art Database

Power Supply

IP.com Disclosure Number: IPCOM000092249D
Original Publication Date: 1968-Oct-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 33K

Publishing Venue

IBM

Related People

Galetto, LV: AUTHOR [+2]

Abstract

In an AC to DC voltage converter of a transistor power supply in which a pair of NPN transistors T1 and T2 are alternatively switched to conduct, it is desirable to have the switching frequency as high as possible. As drive frequency is increased, T1 and T2 tend to conduct simultaneously due to storage delay time of transistor which is to be switched off, resulting in high circulating current in a loop containing both transistors. To eliminate the high circulating current, one transistor is switched on after the other transistor has come out of saturation and vice versa.

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Power Supply

In an AC to DC voltage converter of a transistor power supply in which a pair of NPN transistors T1 and T2 are alternatively switched to conduct, it is desirable to have the switching frequency as high as possible. As drive frequency is increased, T1 and T2 tend to conduct simultaneously due to storage delay time of transistor which is to be switched off, resulting in high circulating current in a loop containing both transistors. To eliminate the high circulating current, one transistor is switched on after the other transistor has come out of saturation and vice versa.

Bases 1 and 2 of T1 and T2 are connected to outputs of And's 3 and 4 respectively. Input diodes 5 and 6 of And's 3 and 4 are connected to the secondary winding of transformer 7, the primary winding of which is energized by rectangular waveforms. Other input diodes 8 and 9 are cross-connected to collectors 10 and 11 of T1 and T2 respectively. Collectors 10 and 11 are connected to output transformer 12.

Assume now that T1 was conducting with positive voltage applied to input diode 5 and T2 was cut off with negative voltage applied to input diode 6 and that the polarity of voltage appearing at input diodes 5 and 6 has just been reversed. And 4 is not immediately satisfied at that instant since input diode 8 is still supplied with low voltage. This is because T1 is still kept conductive due to its storage delay. After cessation of the storage delay time of T1, high voltage is developed o...