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Waveform Averaging RC Circuit

IP.com Disclosure Number: IPCOM000081659D
Original Publication Date: 1974-Jul-01
Included in the Prior Art Database: 2005-Feb-28
Document File: 3 page(s) / 38K

Publishing Venue

IBM

Related People

Cielo, JR: AUTHOR [+3]

Abstract

The circuit shown is an improved filter circuit for providing an output which corresponds to the average of the input applied thereto.

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Waveform Averaging RC Circuit

The circuit shown is an improved filter circuit for providing an output which corresponds to the average of the input applied thereto.

Transistor switch 22 is turned on by a forward bias base drive signal on line
41. Current then flows from terminal 10, through primary 18 and switch 22 to terminal 12, including a voltage in the secondary windings 26 and 42. A resulting positive voltage of a first potential level occurs at point A, and is chiefly a function of voltage +E applied at terminal 10 of the regulator input, multiplied by the turns ratio of the primary winding 18 to the secondary winding 42. The positive voltage, minus the small forward bias drop in diode 44, is communicated directly to point C at the input of RC filter 46, 48.

Capacitor 52 had been charged in a previous cycle to a negative voltage by the potential at point B rises slowly, toward the value of point C in accordance with the time constant of the resistor-capacitor combination 52, 56.

The RC filter 46, 48 operates to provide a filtered output of a second positive potential level at point D of the filter. The output at point D during this portion of the cycle rises slightly, but since the time constant of RC filter 46, 48 is relatively large, the slope of this rise is slight.

When pulses width control 24 operates via line 41 to turn transistor 22 off, the potential at point A drops abruptly and continues at a negative level during the magnetization reset action of transformer 20. The reverse voltage appearing across primary winding 18 at this time is limited by clamp circuit 36, 38, 39, to a value determined by the charge on clamp capacitor 36 plus the forward drop in diode 39. This potential is reflected into secondary winding 42, whereby point A thereof falls to a negative level.

After the magnetization energy is transferred from winding 18 to the clamp circuit thereacross, the reverse potential across primary 18 and, therefore, the reverse reflected potential across secondary 42 decreases in magnitude. The appearance of a negative voltage at point A, forward biases diode 54 and recharges capacitor 42 to approximately the same negative potential level at point B. This voltage is applied to the end of resistor 16 connected thereto so as to pull point C toward the negative potential level, until diode 60 becomes forward biased and clamps point C to the level of the logic ground bus 58....