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Inverter Start Circuit

IP.com Disclosure Number: IPCOM000081893D
Original Publication Date: 1974-Aug-01
Included in the Prior Art Database: 2005-Feb-28
Document File: 2 page(s) / 65K

Publishing Venue

IBM

Related People

Duspiva, WS: AUTHOR

Abstract

The start circuit shown in Fig. 1 will provide an output bias to the remaining control circuits of a regulator, such as shown, for example, in Fig. 2, while the output voltage of the regulator is gradually being ramped-up (over a 1/2 to 2 second interval).

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Inverter Start Circuit

The start circuit shown in Fig. 1 will provide an output bias to the remaining control circuits of a regulator, such as shown, for example, in Fig. 2, while the output voltage of the regulator is gradually being ramped-up (over a 1/2 to 2 second interval).

When the power switch SW1 of Fig. 2 is closed, an AC input is presented to the start circuit of Fig. 1. This input momentarily charges capacitor C2. The pulse through C1 may last for only a few milliseconds, but this is long enough to provide an output at C3 to operate the remainder of the control circuits and begin the switching action of Qx. The pulse width of Qx is narrowed down and then gradually widened, so as to ramp the voltage of Cx to its intended value. This gradual ramp action prevents large internal surges from occurring.

While Cx is being brought up in voltage, a second input to the start circuit is established: Feedback from the inductor L. This input serves to maintain the action of the start circuit which has begun by the AC pulse. When Cx finally reaches its peak value, so does the bias feedback, and this same bias feedback turns off the start circuit through CR5.

In the start circuit, Q1 is either on or off, either charging C3 or allowing C3 to discharge into the remainder of the control circuits. Transistors Q3, Q4 and resistors R7, R8, R9 all form a comparator with hysteresis, the basis for the limit cycle operation. Q2 is the drive transistor for Q1. If Q1 were to be...