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Backup power circuit - Patent 4316097 (6406 words) |
 | A backup circuit according to claim 3, wherein the predetermined value of the ramp signal is generally at the midportion of its slope and is equal to the reference signal input of the comparator. |
| The present invention resides in the provision of such conventional circuit with temperature compensation means in the preferred form of four anode-to-cathode, series-connected, temperature-sensitive, semiconductor diodes 140a, 140b, 140c, and 140d, which, in combination with a calibrating potentiometer 143, varies the charging current curve of the battery charger circuit as a function of battery temperature. |
| Such circuit characteristics are effected by the variance in the control voltage between pins 5 and 6 of chip 135, caused in turn by variance of the inherent voltage across the diodes 140a, 140b, 140c, and 140d in response to changing temperatures. |
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