Power supply apparatus for efficiently utilizing battery and electronic apparatus using the power supply

• US 5,610,450 A
• Filed: 06/29/1995
• Issued: 03/11/1997
• Est. Priority Date: 11/10/1994
• Status: Expired due to Term

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Ozawa, Hidekiyo, Mitsui, Hisafumi, Saeki, Mituo, Suzui, Tsutomu
• Primary Examiner(s): Shoop, Jr., William M.
• Assistant Examiner(s): LOCKETT, KIMBERLY R
• Application Number:
  US08/496,617
• Time in Patent Office: 621 Days
• Field of Search: 307/43, 307/44, 307/45, 307/46, 363/101
• US Class Current: 307/46
• CPC Class Codes: G05F 1/56 using semiconductor devices in series with the load as final control devices G05F1/461 takes precedence
• CPC Class Codes: H02J 2207/20 Charging or discharging characterised by the power electronics converter

Abstract

A booster type DC-DC conversion circuit and a voltage reduction type DC-DC conversion circuit are connected in series with a battery. When battery voltage is high, the booster type DC-DC conversion circuit does not operate, and the voltage reduction type DC-DC conversion circuit outputs a constant voltage lower than the battery voltage. When the battery voltage drops, the booster type DC-DC conversion circuit operates, and converts the battery voltage to a constant voltage higher than the operation voltage of the voltage reduction type DC-DC conversion circuit. The voltage reduction type DC-DC conversion circuit outputs a constant voltage. The power supply apparatus can continuously output a constant voltage from when the battery voltage is high until it becomes low, and can efficiently utilize the battery capacity.

Claims

1. A power supply apparatus, comprising:

a battery;

a booster type DC-DC conversion circuit having an input side thereof connected to said battery, for outputting a constant voltage above an input voltage to an output side thereof when the conversion circuit is operation, and passing the input voltage to the output side thereof when the operation of the conversion circuit is inhibited;

a voltage reduction type DC-DC conversion circuit having an input side thereof connected to the output side of said booster type DC-DC conversion circuit, for generating a constant voltage lower than the input voltage to an output side thereof;

battery voltage detection means for detecting whether the voltage of said battery is above a reference value; and

control means for outputting a signal for inhibiting the operation of said booster type DC-DC conversion circuit when said battery voltage detection means detects that the battery voltage is above said reference value, and a signal for operating said booster type DC-DC conversion circuit when said battery voltage detection means detects that the battery voltage is below said reference value.

2. A power supply apparatus comprising:

a battery;

a booster type DC-DC conversion circuit having an input side thereof connected to said battery, for outputting a constant voltage above an input voltage to an output side thereof when the conversion circuit is operation, and passing the input voltage to the output side thereof when the operation of the conversion circuit is inhibited;

a voltage reduction type DC-DC conversion circuit having an input side thereof connected to the output side of said booster type DC-DC conversion circuit, for generating a constant voltage lower than the input voltage to an output side thereof;

external terminals for connecting an external D.C. power supply, connected to the input side of said voltage reduction type DC-DC conversion circuit;

external voltage detection means for detecting whether a voltage between said external terminals is above a reference value;

battery voltage detection means for detecting whether or not the voltage of said battery is above a reference value; and

control means for outputting a signal for operating said booster type DC-DC conversion circuit only when said external voltage detection means detects that the external voltage is below said reference value and said battery voltage detection means detects that the battery voltage is below said reference value.

3. A power supply apparatus according to claim 2, which further comprises a blocking diode interposed between said external terminal and the input side of said voltage reduction type DC-DC conversion circuit, and a blocking diode interposed between said battery and said voltage reduction type DC-DC conversion circuit.

4. A power supply apparatus according to claim 2, which further comprises a charger connected between said external terminal and said battery.

5. An electronic apparatus including a power supply apparatus, said power supply apparatus comprising:

a battery;

a booster type DC-DC conversion circuit having an input side thereof connected to said battery, for outputting a constant voltage above an input voltage to an output side thereof when the conversion circuit is operation, and passing the input voltage to the output side thereof when the operation of the conversion circuit is inhibited;

a voltage reduction type DC-DC conversion circuit having an input side thereof connected to the output side of said booster type DC-DC conversion circuit, for generating a constant voltage lower than an input voltage to an output side thereof;

battery voltage detection means for detecting whether or not the voltage of said battery is above a reference value; and

control means for outputting a signal for inhibiting the operation of said booster type DC-DC conversion circuit when said battery voltage detection means detects that the battery voltage is above said reference value, and a signal for operating said booster type DC-DC conversion circuit when said battery voltage detection means detects that the battery voltage is below said reference value.

6. An electronic apparatus including a power supply apparatus, said power supply apparatus comprising:

a battery;

a booster type DC-DC conversion circuit having an input side thereof connected to said battery, for outputting a constant voltage above an input voltage to an output side thereof when the conversion circuit is operation, and passing the input voltage to the output side thereof when the operation of the conversion circuit is inhibited;

a voltage reduction type DC-DC conversion circuit having an input side thereof connected to the output side of said booster type DC-DC conversion circuit, for generating a constant voltage lower than an input voltage to an output side thereof;

external terminals connected to the input side of said voltage reduction type DC-DC conversion circuit, for connecting an external D.C. power supply;

external voltage detection means for detecting whether or not a voltage between said external terminals is above a reference value;

battery voltage detection means for detecting whether or not the voltage of said battery is above a reference value; and

control means for outputting a signal for operating said booster type DC-DC conversion circuit only when said external voltage detection means detects that the external voltage is blow the reference value and said battery voltage detection means detects that the battery voltage is below the reference value.

7. An electronic apparatus according to claim 6, which further comprises a locking diode interposed between said external terminal and the input side of said voltage reduction type DC-DC conversion circuit, and a blocking diode interposed between said battery and said voltage reduction type DC-DC conversion circuit.

8. An electronic apparatus according to claim 6, which further comprises a charger connected between said external terminal and said battery.