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

• US 7,453,711 B2
• Filed: 03/18/2005
• Issued: 11/18/2008
• Est. Priority Date: 03/26/2004
• Status: Expired due to Fees

• Current Assignee: ROHM Co., Ltd.
• Original Assignee: ROHM Co., Ltd.
• Inventors: Komiya, Kunihiro, Yanagida, Osamu
• Primary Examiner(s): Vu; Bao Q
• Application Number:
  US11/084,472
• Publication Number:
  US 20050213356A1
• Time in Patent Office: 1,341 Days
• Field of Search: 363/59, 363/60
• 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 voltage supply unit comprising:

a first charge pump unit having

a first capacitor,

a first double throw switch having a common terminal coupled to one end of said first capacitor, a first terminal coupled to an input terminal whereto input voltage is supplied, and a second terminal coupled to the ground, and

a second double-throw switch having a common terminal coupled to another end of said first capacitor, a first terminal, and a second terminal coupled to said input terminal, said second double throw switch operated by the same control signal as said first double throw switch,

a first step-up voltage outputting switch for outputting a first step-up voltage from another end of said first capacitor,

a second stage charge pump unit having

a second capacitor,

a third double-throw switch having a common terminal coupled to one end of said second capacitor, a first terminal coupled to the first terminal of said second double throw switch, and a second terminal coupled to the ground, and

a fourth double-throw switch having a common terminal coupled to another end of said second capacitor, a first terminal, and a second terminal coupled to said input terminal, said fourth double throw switch operated by the same control signal as said third double throw switch,

a second step-up voltage outputting switch for outputting a second step-up voltage from another end of said second capacitor,

a last stage charge pump unit having

a third capacitor,

a fifth double-throw switch having a common terminal coupled to one end of said third capacitor, a first terminal coupled to the first terminal of said fourth double throw switch, and a second terminal coupled to the ground, and

a sixth double-throw switch having a common terminal coupled to another end of said third capacitor, a first terminal, and a second terminal coupled to said input terminal, said sixth double throw switch operated by the same control signal as said fifth double throw switch, and

a control circuit for outputting an output voltage control signal for

synchronizing said first and second double throw switches and said first step-up voltage outputting switch, and switching on and off, when outputting a first step-up voltage of said first stage charge pump unit,

synchronizing said first, second, third, and fourth double throw switches and said second step-up voltage outputting switch, and switching on and off, when outputting a second step-up voltage of said second stage charge pump unit, and

switching on and off said first, second, third, fourth, fifth and sixth double throw switches and said second step-up voltage outputting switch, when outputting a third step-up voltage of said last stage charge pump unit,

wherein said step-up voltage supply unit outputs a third step-up voltage from the first terminal of said sixth double throw switch of said last stage charge pump unit without passing through any output switch.

2. A step-up voltage supply unit comprising:

a first charge pump unit having

a first capacitor,

a first single throw switch having one terminal coupled to one end of said first capacitor and another end coupled to an input terminal whereto input voltage is supplied,

a first double throw switch having a common terminal coupled to another end of said first capacitor, a first terminal coupled to said input terminal, and a second terminal coupled to the ground, said first double throw switch operated by the same control signal as said first single throw switch,

a first step-up voltage outputting switch for outputting a first step-up voltage from one end of said first capacitor,

a second stage charge pump unit having

a second capacitor,

a second single throw switch having one terminal coupled to one end of said second capacitor and another end coupled to one end of said first capacitor,

a second double throw switch having a common terminal coupled to another end of said second capacitor, a first terminal coupled to said input terminal, and a second terminal coupled to the ground, said second double throw switch operated by the same control signal as said second single throw switch,

a second step-up voltage outputting switch for outputting a second step-up voltage from one end of said second capacitor,

a last stage charge pump unit having

a third capacitor,

a third single throw switch having one terminal coupled to one end of said third capacitor and another end coupled to one end of said second capacitor,

a third double throw switch having a common terminal coupled to another end of said third capacitor, a first terminal coupled to said input terminal, and a second terminal coupled to the ground, said third double throw switch operated by the same control signal as said third single throw switch,

a third step-up voltage outputting switch for outputting a third step-up voltage from one end of said third capacitor,

a control circuit for outputting an output voltage control signal for

synchronizing said first single and double throw switches and said first step-up voltage outputting switch, and switching on and off, when outputting a first step-up voltage of said first stage charge pump unit,

synchronizing said first and second single throw switches and said first and second double throw switches and said second step-up voltage outputting switch, and switching on and off, when outputting a second step-up voltage of said second stage charge pump unit, and

switching on and off said first, second, and third single throw switches and said first, second, and third double throw switches and said third step-up voltage outputting switch, when outputting a step-up voltage of said last stage charge pump unit,

wherein said step-up voltage supply unit outputs first, second and third step-up voltage via said first, second and third step-up voltage outputting switches, respectively.