ELECTRIC POWER PATH SWITCHING METHOD AND ELECTRIC POWER PATH SWITCHING CIRCUIT
An electric power path switching method for switching a first electric power path from a built-in rechargeable battery in a communication device and a second electric power path from a charger for charging the rechargeable battery which can be connected to the communication device by plugging in and out, includes dividing a load of the communication device into two systems of a first load and a second load; supplying electric power to the first load from the first electric power path; and supplying electric power to the second load from the second electric power path when charging the rechargeable battery by the charger and from the first electric power path when the rechargeable battery is not charged.
1 . An electric power path switching method for switching a first electric power path from a built-in rechargeable battery in a communication device and a second electric power path from a charger for charging the rechargeable battery which can be connected to the communication device by plugging in and out, comprising:
dividing a load of the communication device into two systems of a first load and a second load;
supplying electric power to the first load from the first electric power path; and
supplying electric power to the second load from the second electric power path when charging the rechargeable battery by the charger and from the first electric power path when the rechargeable battery is not charged.
2 . An electric power path switching circuit for switching a first electric power path from a built-in rechargeable battery in a communication device and a second electric power path from a charger for charging the rechargeable battery which can be connected to the communication device by plugging in and out, wherein;
a load of the communication device is divided into two systems of a first load and a second load; and
the electric power path switching circuit comprises:
an electricity feeding path for supplying an electric power to the first load from the first electric power path; and
an electric power switching module for switching the first electric power path and the second electric power path, and supplying the switched electric power to the second load; wherein
the electric power path switching module supplies electric power from the first electric power path to the second load as the switched electric power when the charger is not connected to the communication device and supplies electric power from the second electric power path to the second load as the switched electric power when the charger is connected to the communication device.
3 . The electric power path switching circuit according to claim 2 , wherein;
the electric power path switching module comprises a first input edge connected to the first electric power path, a second input edge connected to the second electric power path, and an output edge which outputs the switched electric power; and
the electric power path switching module is configured by;
a first conducting device that is inserted between the first input edge and the output edge, having electric power from the first electric power path conduct to the output edge as the switched electric power; and
a second conducting device that is inserted between the second input edge and the output edge, having electric power from the second electric power path conduct to the output edge as the switched electric power.
4 . The electric power path switching circuit according to claim 3 , wherein;
the first conducting device is configured by a first Schottky Barrier Diode having an anode connected to the first input edge and a cathode connected to the output edge; and
the second conducting device is configured by a second Schottky Barrier Diode having an anode connected to the second input edge and a cathode connected to the output edge.
5 . The electric power path switching circuit according to claim 3 , wherein;
the electric power path switching module further comprises a backflow prevention circuit for preventing a reverse current flowing to the rechargeable battery via the first conducting device from the second load when the charger is connected to the communication device.
6 . The electric power path switching circuit according to claim 3 , wherein;
the electric power path switching module further comprises a first loss reduction circuit for reducing a loss which occurs in the first conducting device when the charger is not connected to the communication device.
7 . The electric power path switching circuit according to claim 3 , wherein;
the electric power path switching module further comprises a second loss reduction circuit for reducing a loss which occurs in the second conducting device when the charger is not connected to the communication device.
8 . The electric power path switching circuit according to claim 7 , wherein;
the first conducting device comprises
a Schottky Barrier Diode by which an anode is connected to the first input edge, and a cathode is connected to the output edge; and
a first P-channel MOSFET by which a drain is connected to the first input edge, and a source is connected to the output edge;
the second conducting device comprises
a P-channel MOSFET by which a drain is connected to the second input edge and a cathode is connected is connected to the output edge; and
the second loss reduction circuit is configured of:
a comparator for controlling a gate voltage of the first P-channel MOSFET and the second P-channel MOSFET by the comparison result of comparing the voltage of the first input edge and the voltage of the second input edge.
9 . The electric power path switching circuit according to claim 8 , wherein;
the comparator makes the gate control voltage of the first P-channel MOSFET as a logical low level when the voltage of the first input edge is higher than the voltage of the second input edge and as a logical high level when it is higher; and
the comparator makes the gate control voltage of the second P-channel MOSFET as a logical high level when the voltage of the first input edge is higher than the voltage of the second input edge and as a logical low level when it is lower.
10 . The electric power path switching circuit according to claim 8 , wherein;
the comparator makes the gate control voltage of the first P-channel MOSFET as a logical low level when the voltage of the first input edge is higher than the voltage of the second input edge and as a logical high level when it is lower; and
the comparator makes the gate control voltage of the second P-channel MOSFET as a logical high level when the voltage of the first input edge is higher than the voltage that deducted only the predetermined offset voltage from the voltage of the second input edge and as a logical low level when it is low.