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US 7,842,967 B2Granted
Semiconductor device used in step-up DC-DC converter, and step-up DC-DC converter
AssigneeRicoh Company, Ltd.
InventorsMasaya Ohtsuka, Yoshinori Ueda
Life of this patent
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Abstract
A power supply device is disclosed that is able to satisfy the power requirements of a device in service and has high efficiency. The power supply device includes a first power supply; a voltage step-up unit that steps up an output voltage of the first power supply; a voltage step-down unit that steps down an output voltage of the voltage step-up unit; and a load that is driven to operate by an output voltage of the voltage step-down unit. The voltage step-up unit steps up the output voltage of the first power supply to a lower limit of an operating voltage of the voltage step-down unit.
Claims18
A semiconductor device used in a step-up DC-DC converter, comprising:
- a switching element;
- a diode element formed in the same semiconductor substrate as the switching element;
- a switching terminal;
- and
- an output terminal,
- wherein
- the switching element includes a LDMOS transistor having a channel region formed of a surface portion of a body diffusion layer below a gate electrode of the LDMOS, said LDMOS transistor including
- a source diffusion layer,
- wherein the body diffusion layer has a conductivity opposite to a conductivity of the source diffusion layer, and is formed to enclose a side surface and a bottom surface of the source diffusion layer, and
- a drain diffusion layer that has a conductivity the same as the conductivity of the source diffusion layer, and is formed outside and neighboring the body diffusion layer, and
- the diode element includes a vertical bipolar transistor including
- a collector diffusion layer that forms a collector of the diode element,
- a base diffusion layer that has a conductivity opposite to a conductivity of the collector diffusion layer, and forms a base of the diode element in the collector diffusion layer, said base being connected to the collector, and
- an emitter diffusion layer that has a conductivity the same as the conductivity of the collector diffusion layer, and forms an emitter of the diode element in the base diffusion layer, thereby producing a diode between the base and the emitter, and
- wherein
- a drain of the switching element and an anode of the diode element are connected to the switching terminal, and
- a cathode of the diode element is connected to the output terminal, wherein the diode element further includes a high concentration diffusion layer formed in the base diffusion layer in a direction intersecting a longitudinal direction of the base diffusion layer, and the high concentration diffusion layer has the same conductivity and a higher impurity concentration as compared to the base diffusion layer.
14 more elements
A step-up DC-DC converter, comprising:
- a semiconductor device;
- a coil;
- and
- a capacitor;
- wherein
- the semiconductor device includes
- a switching element;
- a diode element formed in the same semiconductor substrate as the switching element;
- a switching terminal connected to the coil;
- and
- an output terminal connected to one end of the capacitor;
- wherein
- the switching element includes a LDMOS transistor having a channel region formed of a surface portion of a channel diffusion layer below a gate electrode of the LDMOS, said LDMOS transistor including
- a source diffusion layer,
- the channel diffusion layer that has a conductivity opposite to a conductivity of the source diffusion layer, and is formed to enclose a side surface and a bottom surface of the source diffusion layer, and
- a drain diffusion layer that has a conductivity the same as the conductivity of the source diffusion layer, and is formed outside and neighboring the channel diffusion layer,
- the diode element includes a vertical bipolar transistor comprising:
- a collector diffusion layer that forms a collector of the diode element,
- a base diffusion layer that has a conductivity opposite to a conductivity of the collector diffusion layer, and forms a base of the diode element in the collector diffusion layer, said base being connected to the collector, and
- an emitter diffusion layer that has a conductivity the same as the conductivity of the collector diffusion layer, and forms an emitter of the diode element in the base diffusion layer, whereby a diode is produced between the base and the emitter,
- wherein
- a drain of the switching element and an anode of the diode element are connected to the switching terminal,
- a cathode of the diode element is connected to the output terminal,
- one end of the coil is connected to the switching terminal, and
- one end of the capacitor is connected to the output terminal, wherein the diode element further includes a high concentration diffusion layer formed in the base diffusion layer in a direction intersecting a longitudinal direction of the base diffusion layer, and the high concentration diffusion layer has the same conductivity and a higher impurity concentration as compared to the base diffusion layer.
22 more elements
Dependencies are inferred from the claim text.