| 摘要 |
PURPOSE: A power supply circuit in a wireless modem having a TDD(Time Division Duplexing) is provided to extend a battery life, built in the wireless modem, by supplying different voltage outputted from a DC/DC converter inside of a power supply circuit, when a transmission mode and a reception mode are performed. CONSTITUTION: A DC/DC converter(10) boosts battery voltage(Vb) to predetermined voltage through a step-up method, according to the comparing result of feedback voltage(Vtb) and inside standard voltage. A feedback voltage detector(21) contacts a contact point of a first and a second resistor(R1,R2) with a feedback voltage detector terminal of the DC/DC converter, including an electric switch for supervising connection in parallel between a fourth resistor(R4) and a second resistor after operating turn-on and turn-off, according to the first/the second resistor(R1,R2) contacted in series between an output terminal of the DC/DC converter(10) and a ground, the fourth resistor(R4) contacted in parallel to the second resistor(R2), and a Smode. A switch(SW1) contacts the common contact(c) to contact(a) by a receiving mode selection signal(TX) among the Smods, and contacts the common contact(c) to contact(b) by a receiving mode selection signal(RX). A first regulator(12) stabilizes voltage to receiving operating voltage(Vrx) through the contact(b) of the switch(SW1). A second regulator(13) stabilizes output voltage(V1) of the DC/DC converter(10) to power supply voltage(Vbb).
|
