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Self Activated Drivers for Capacitive Based Voltage Reducer

IP.com Disclosure Number: IPCOM000083421D
Original Publication Date: 1975-May-01
Included in the Prior Art Database: 2005-Mar-01
Document File: 4 page(s) / 65K

Publishing Venue

IBM

Related People

Hoffman, HS: AUTHOR

Abstract

These self-activated drivers provide automatic timing signals for operating transistor switches of a capacitive based voltage reducer.

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Self Activated Drivers for Capacitive Based Voltage Reducer

These self-activated drivers provide automatic timing signals for operating transistor switches of a capacitive based voltage reducer.

A voltage reducer (VR) 10 is connected to a load 11 to supply load 11 with a reduced voltage, derived from a higher DC voltage applied to terminals 12 and 13 of a power source. VR 10 comprises a plurality of capacitors 16-20, a plurality of diodes 22-25, and a plurality of transistor switches 27-30 connected as shown in the drawing. A bleed resistor 14 is connected in parallel across load 11.

Four drivers 40, 50, 60 and 70 provide timing signals to switches 27-30 to operate them in one mode of operation, which provides a voltage reduction of 1/4. To accomplish this, switches 27 and 30 are turned on and off concurrently and switches 28 and 29 are turned on and off concurrently, but alternately with the operation of switches 27 and 30. When VR 10 is in operation, capacitors 16- 20 are, respectively, charged to nominal fractions of 1/2, 1/2, 1/4, 1/4 and 1/4 of the input voltage across terminals 12 and 13. Capacitor 20 is used to smooth out the current supplied to load 11.

The basic cycle of operation is divided into two periods. The first one is when switches 27 and 30 are on while the others are off.

The second period is when switches 28 and 29 are on while switches 27 and 30 are off. With switch 27 on, half of the current flowing into the collector of switch 27 comes from the power source and half comes from the discharge of capacitor 16. This current flows through capacitor 18 to charge it from a state of lower charge to a state of higher charge, through diode 24, load 11 and diode 23. At this point, the current splits and half of it returns to the lower plate of capacitor 16, while the other half flows through capacitor 17 back to the power source and, in the process of flowing, charges capacitor
17.

Concurrently, switch 30 is on and this connects capacitor 19 in parallel with the load for discharge therethrough. Current flows from the upper plate of capacitor 19, through diode 24, load 11 and switch 30 back to the lower plate of capacitor 19. During this period, capacitors 16 and 19 discharge while capacitors 17 and 18 charge. During the second period, with switches 29 and 28 on, the reverse action occurs so that capacitors 17 and 18 discharge while capacitors 16 and 19 charge.

The timing circuit comprised of drivers 40, 50, 60 and 70 controls the operation of switches 27-30. Drivers 40-70 are identical and each operates in a similar manner. In each driver, the units digit of the reference numeral denotes similar parts. A start/stop timing signal is applied to terminals 32 and 33 of driver
50. When the start signal is applied, the timing circuit is enabled.

Driver 50 comprises a voltage divider 51 containing resistors 51-1 and 51-2 connected in parallel across switch 28 being controlled by driver 50, to provide a voltage division when s...