| 摘要 |
PURPOSE:To extend the constant voltage output range in the low voltage side by making a by-pass circuit conductive by a control circuit when the input voltage from a battery is reduced beyond the constant voltage outputtable range of a constant voltage circuit. CONSTITUTION:A constant voltage circuit 10 changes the resistance value R of an active element in accordance with variances of an input voltage Ei and an output voltage Eo to output 5V constant voltage. In this case, the first by- pass circuit consisting of the series circuit of a relay contact 14a (the first switch) and a diode 16 and the second by-pass circuit consisting of a relay contact 12a (the second switch) are juxtaposed between input and output terminals of the constant voltage circuit 10. These by-pass circuits are controlled by the control circuit consisting of a comparator 18, a window comparator 20, and relays 12 and 14. If the battery voltage (input voltage) Ei is reduced below 5.5V, the output of the comparator 18 goes to the high level, and the contact 12a of the relay 12 is turned on to output said voltage Ei directly.
|
