Overcharge prevention circuit and semiconductor device

Patent metadata

Field	Value
Publication number	US-8988840-B2
Application number	US-201213612130-A
Country	US
Kind code	B2
Filing date	Sep 12, 2012
Priority date	Sep 28, 2011
Publication date	Mar 24, 2015
Grant date	Mar 24, 2015

Abstract

Provided is an overcharge prevention circuit for clamping a voltage value of an electric power generation unit in an overcharged state to a constant value, in which the number of elements is small and which does not consume electric power unnecessarily. The overcharge prevention circuit includes: a backflow prevention diode; a clamping transistor having a gate connected to a cathode of the backflow prevention diode, a source connected to an anode thereof, and a drain connected to an overcharge prevention switch. Upon detection of overcharge, a current is discharged via the clamping transistor and the overcharge prevention switch, thereby clamping a potential of the electric power generation unit to around a voltage of an electricity storage unit.

First claim

What is claimed is:

1. An overcharge prevention circuit for a semiconductor device whose power source is an electrical storage device charged by an electric power generation device, for preventing overcharge of the electrical storage device, the overcharge prevention circuit comprising:
an overcharge detection circuit connected to a positive terminal and a negative terminal of the electrical storage device, for detecting a voltage of the electrical storage device;
an overcharge prevention transistor including:
a gate terminal connected to an output terminal of the overcharge detection circuit; and
a source terminal and a back gate terminal connected to a ground terminal; and

a clamping transistor including:
a gate terminal connected to a positive terminal of the electrical power generation device via a back flow prevention circuit located between the gate terminal and a source terminal thereof;
a drain terminal connected to a drain terminal of the overcharge prevention transistor; and
the source terminal and a back gate terminal electrically connected to the positive terminal of the electric power generation device, such that the drain terminal of the overcharge prevention transistor is electrically connected to the positive terminal of the electric power generation device through the clamping transistor, and the overcharge prevention transistor and the clamping transistor are connected in series between the positive terminal and a negative terminal of the electric power generation device, such that an overcharge voltage of the electric power generation device is restricted to a voltage of the electrical storage device plus a gate-source voltage of the clamping transistor.

2. A semiconductor device, comprising:
electric power generation device;
electrical storage device; and
the overcharge prevention circuit according to claim 1 , wherein the backflow prevention circuit prevents backflow from the electrical storage device to the electric power generation device.

Assignees

• Mitani Makoto
• Watanabe Kotaro
• Seiko Instr Inc

Inventors

• Mitani Makoto
• Watanabe Kotaro

Classifications

• H02J7/61 Primary

  against overcharge · CPC title

• H02J7/00 Primary

  Circuit arrangements for charging or discharging batteries or for supplying loads from batteries · CPC title

• Y02E10/566

  Cross-Sectional Technologies · mapped topic

• H02J2007/0037

  Electricity · mapped topic

• Y02E60/10

  Energy storage using batteries · CPC title