Step-up power supply unit and portable apparatus utilizing the same

• US 20050213356A1
• Filed: 03/18/2005
• Published: 09/29/2005
• Est. Priority Date: 03/26/2004
• Status: Active Grant

• Current Assignee: ROHM Co., Ltd.
• Original Assignee: ROHM Co., Ltd.
• Inventors: Komiya, Kunihiro, Yanagida, Osamu
• Granted Patent: US 7,453,711 B2
• Time in Patent Office: Days
• US Class Current: 363/59
• CPC Class Codes: H02M 3/07 using capacitors charged and discharged alternately by semiconductor devices with control electrode , e.g. charge pumps

Abstract

A step-up power supply unit for providing a multiplicity of different step-up voltages as needed, generated by stepping up a voltage of a single power source such as a battery. The step-up voltage of the last stage charge pump unit and the step-up voltage of at least one charge pump unit other than the last stage charge pump unit, are made available as multiple output voltages. When one or more of the output voltages are not needed, all the charge pump units subsequent to the one providing the highest output voltage are disabled based on an output voltage control signal, thereby minimizing the size and cost of the step-up circuit and reducing the power consumption by the circuit.

Claims

1. A step-up power supply unit having N stages of charge pump units (N being greater than 1) connected in series for stepping up an input voltage, with each charge pump unit having a capacitor and a switch circuit, wherein:

said step-up power supply unit is adapted to output a multiplicity of output voltages based on the step-up voltages of the last stage charge pump unit and of at least one charge pump unit other than the last stage charge pump unit; and

said output voltage based on the step-up voltage of said at least one charge pump unit other than the last stage charge pump unit is the step-up voltage output from said at least one charge pump unit via an output switch that is synchronized with the clock controlling the on-off operation of said switch circuit and is controlled by an output voltage control signal.

2. The step-up power supply unit according to claim 1, wherein said output voltage based on the step-up voltage of the last stage charge pump unit is output without passing through any output switch.

3. The step-up power supply unit according to claim 2, wherein when one or more of said output voltages are not needed, the charge pump units in all the stages subsequent to the stage that provides the highest output voltage are disabled based on said output voltage control signal.

4. The step-up power supply unit according to claim 2, wherein each of said charge pump units includes:

a capacitor;

a first double-throw switch having a common terminal connected to one end of the capacitor; and

a second double-throw switch having the common terminal connected to the other end of the capacitor, and operated by the same control signal as for the first double-throw switch.

5. The step-up power supply unit according to claim 2, wherein each of said charge pump units includes:

a capacitor;

a single-throw switch having one terminal connected to one end of the capacitor; and

a double-throw switch having a common terminal connected to the other end of the capacitor, and operated by the same control signal as for the single-throw switch.

6. The step-up power supply unit according to claim 1, wherein when one or more of said output voltages are not needed, the charge pump units in all the stages subsequent to the stage that provides the highest output voltage are disabled based on said output voltage control signal.

7. The step-up power supply unit according to claim 6, wherein each of said N stage output voltages is smoothed and regulated by the regulator of that stage.

8. The step-up power supply unit according to claim 6, wherein each of said charge pump units includes:

a capacitor;

a first double-throw switch having a common terminal connected to one end of the capacitor; and

a second double-throw switch having the common terminal connected to the other end of the capacitor, and operated by the same control signal as for the first double-throw switch.

9. The step-up power supply unit according to claim 6, wherein each of said charge pump units includes:

a capacitor;

a single-throw switch having one terminal connected to one end of the capacitor; and

a double-throw switch having a common terminal connected to the other end of the capacitor, and operated by the same control signal as for the single-throw switch.

10. The step-up power supply unit according to claim 1, wherein each of said N stage output voltages is smoothed and regulated by the regulator of that stage.

11. The step-up power supply unit according to claim 10, wherein each of said charge pump units includes:

a capacitor;

a first double-throw switch having a common terminal connected to one end of the capacitor; and

a second double-throw switch having the common terminal connected to the other end of the capacitor, and operated by the same control signal as for the first double-throw switch.

12. The step-up power supply unit according to claim 10, wherein each of said charge pump units includes:

a capacitor;

a single-throw switch having one terminal connected to one end of the capacitor; and

a double-throw switch having a common terminal connected to the other end of the capacitor, and operated by the same control signal as for the single-throw switch.

13. The step-up power supply unit according to claim 1, wherein each of said charge pump units includes:

a capacitor;

a first double-throw switch having a common terminal connected to one end of the capacitor; and

a second double-throw switch having the common terminal connected to the other end of the capacitor, and operated by the same control signal as for the first double-throw switch.

14. The step-up power supply unit according to claim 1, wherein each of said charge pump units includes:

a capacitor;

a single-throw switch having one terminal connected to one end of the capacitor; and

a double-throw switch having a common terminal connected to the other end of the capacitor, and operated by the same control signal as for the single-throw switch.

15. A portable apparatus having different components that utilize the output voltages of the step-up power supply unit according to any one of claims 1 through 14.