Backup battery system for a portable electronic device

An apparatus comprising:

• first voltage multiplying means for coupling to a primary power source having a primary voltage, said first voltage multiplying means for increasing the voltage from a primary power source to provide a regulated voltage having a magnitude greater than a magnitude of the primary voltage;
• second voltage multiplying means coupled to the primary power source, said second voltage multiplying means increasing the voltage from the primary power source to a limited voltage, Wherein a magnitude of the limited voltage is greater than the magnitude of the regulated voltage;
• rechargeable power source coupled to said second voltage multiplying means, said rechargeable power source recharging to a voltage substantially equal to the limited voltage;
• and
• electrical circuit means selectively powered by said first voltage multiplying means in response to the presence of the primary power source, and selectively powered by said rechargeable power source in response to the absence of the primary power source.

A selective call receiver having a decoder circuit, a primary power source, and a back-up power source, wherein said decoder circuit controls a plurality of selective call receiver functions, and further wherein the primary power source provides power for said selective call receiver and the back-up power source provides back-up power to said selective call receiver in the event that primary power is unavailable, said selective call receiver comprising:

• a first voltage multiplier for receiving a first voltage from said primary power source, said first voltage multiplier boosting the first voltage to a regulated voltage having a magnitude greater than a magnitude of the first voltage;
• a second voltage multiplier for receiving the first voltage and coupled to said first voltage multiplier for providing the back-up power having a voltage magnitude greater than the magnitude of the regulated voltage, said second voltage multiplier providing a charging current to said back-up power source;
• and
• a power source detector coupled to said decoder and receiving the first voltage, said power source detector detecting when the first power source becomes unavailable and signalling said decoder of an absence of the regulated voltage, said decoder thereafter enabling said back-up power source for supplying the back-up power to said selective call receiver, and wherein said power source absent detector detects a restoration of the regulated voltage and thereafter causing said decoder to delay the charging current to said back-up power source for a predetermined time.