	US 7,453,711 B2
	Step-up power supply unit and portable apparatus utilizing the same
Osamu Yanagida, Kyoto (Japan); and Kunihiro Komiya, Kyoto (Japan)
Assigned to Rohm Co., Ltd., Kyoto (Japan)
Filed on Mar. 18, 2005, as Appl. No. 11/84,472.
Claims priority of application No. 2004-091170 (JP), filed on Mar. 26, 2004.
Prior Publication US 2005/0213356 A1, Sep. 29, 2005
Int. Cl. H02M 3/18 (2006.01); H02M 7/00 (2006.01); H02M 7/19 (2006.01)

U.S. Cl. 363—59 [363/60]

2 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.