Active solid-state devices (e.g. – transistors – solid-state diode – Field effect device – Having insulated electrode
Reexamination Certificate
2000-03-16
2001-11-06
Lee, Eddie (Department: 2815)
Active solid-state devices (e.g., transistors, solid-state diode
Field effect device
Having insulated electrode
C257S387000, C257S248000, C257S328000, C257S329000, C257S119000
Reexamination Certificate
active
06313513
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 11-076062, filed Mar. 19, 1999, the entire contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
This invention relates to an AC switch device used for switching AC circuit and an AC switch circuit having the AC switch device, which are in particular used for an AC circuit for an inverter mounted on small household electrical appliance.
Recently, inverters have become used more and more for small household electrical appliance. In this current of using inverters, an AC switch circuit as follows for switching AC at high speed has been used, as means for providing an inexpensive and high-reliable system in comparison with a DC brushless type circuit.
FIG. 1
shows a circuit diagram showing a basic constitution of the AC circuit. A current flowing from an AC power supply A
101
flows through a load L
101
when a switch SW
101
is closed, and is cut off when the switch SW
101
is opened.
However, if such a circuit is actually used, as shown in
FIG. 2
, a switch SW
102
for making a regenerative current flow when the switch SW
101
is opened is provided. Further, a dead time is provided in order to prevent undesired flow of current between switches SW
101
-SW
102
, and there required bidirectional Zener diodes Z
101
and Z
102
for absorbing a surge generated thereby, and a capacitor C
101
for absorbing a surge generated due to an impedance of the AC power supply A
101
.
Further, constituting an AC switch circuit wherein a current can flow in the two directions as shown in
FIG. 3
is means which are effective in respect of cost and electric power loss. In this circuit, AC switch devices AS
101
and AS
102
capable of running a current in the two directions are used as the switch SW
101
and SW
102
. The AC switch devices AS
101
and AS
102
are made by connecting two MOS field effect transistors (hereinafter referred to as “MOSFET”) in series.
However, in the AC switch device shown in
FIG. 3
, since two MOSFETs are connected in series, the number of the MOSFETs (elements) increases, and wiring resistance also increases. Therefore, in a conventional AC switch circuit, a number of MOSFETs having a low on-state resistance should be prepared, and there is a problem that lowering the price of the device is inhibited.
Further, with respect to gate driving circuits of the TR
101
and TR
102
, since the source voltages are different, floating-state power supplies must be used for them as shown in FIG.
4
and the power supplies must be separated by using transformers, which complicates the circuit.
Therefore, it is generally known as an inexpensive method to use a circuit as shown in
FIG. 5
comprising a bootstrap power supply VBS, a control signal generating circuit
101
, a level shift circuit
102
, drive circuits
103
and
104
, diodes D
101
and D
102
, and capacitors C
101
and C
102
. However, in the case of an AC switch device, it is difficult to apply such a circuit since electric potentials of the both ends of the device are not fixed.
BRIEF SUMMARY OF THE INVENTION
Therefore, the present invention has been made in consideration of the above objects, and is aimed at providing an inexpensive AC switch device having a simple structure wherein the number of elements are reduced, and providing an AC switch circuit which can perform gate drive of the AC switch device in a good state.
In order to achieve the above objects, according to a first aspect of the present invention, there is provided an AC switch device comprising:
a first semiconductor region of a second conductivity type formed on a semiconductor substrate of a first conductivity type, the second conductivity type being different from the first conductivity type;
second and third semiconductor regions of the first conductivity type, separately formed in the first semiconductor region;
fourth and fifth semiconductor regions of the second conductivity type, separately formed in the second semiconductor region;
sixth and seventh semiconductor regions of the second conductivity type, separately formed in the third semiconductor region;
a first channel region formed in an upper part in the second semiconductor region between the fourth and fifth semiconductor regions, on the one hand, and the sixth and seventh semiconductor regions, on the other;
a second channel region formed in an upper part in the third semiconductor region between the fourth and fifth semiconductor regions, on the one hand, and the sixth and seventh semiconductor regions, on the other;
a first control electrode formed above the first channel region with an insulating film interposed; and
a second control electrode formed above the second channel region with an insulating film interposed.
In an AC switch device formed as described above, if a bias is applied between the first control electrode and the second and third semiconductor regions, and between the second control electrode and the fourth and fifth semiconductor regions so that channels are formed in the first and second channel regions, a current flows in either direction in accordance with the state of applying a voltage. Thereby, an inexpensive AC switch device having a simple structure wherein the number of elements are reduced.
In order to achieve the above objects, according to a second aspect of the present invention, there is provided an AC switch circuit comprising:
a switch device which can be rendered conductive bidirectionally and have MOS transistors with current-detecting terminals;
detection circuits for detecting currents flowing through the current-detecting terminals; and
control circuits for controlling voltages to be applied to gates of the MOS transistors, in accordance with detection results of the detection circuits.
In an AC switch circuit formed as described above, gate drive of the switch device can be performed in a good state by detecting currents flowing through the current-detecting terminals provided on the switch device.
In order to achieve the above objects, according to a third aspect of the present invention, there is provided an AC switch circuit comprising:
switch devices which can be rendered conductive bidirectionally and have MOS transistors;
drive circuits for supplying drive voltages to gates of the MOS transistors;
capacitors for supplying voltages to the drive circuits;
an AC power supply connected with the switch devices; and
a bootstrap circuit for boosting the capacitors on the basis of a varying minimum potential in the AC power supply.
In an AC switch circuit formed as described above, gate drive of the switch devices can be performed in a good state by detecting currents flowing through the current-detecting terminals provided on the switch devices.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.
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Mohamed N. Darwish, et al., “Lateral MOS-Gated Power Devices-A Unified View,” IEEE Transactions on Electron Devices, vol. 38, No. 7, Jul. 1991, pp. 1600-1604.
James D. Plummer, et al., “Insulated-Gate Planar Thyristors: I-Structure and Basic Operation,” IEEE Transactions on Electron Devices, vol. ED-27, No. 2, Feb. 1980, pp. 380-387.
Brad W. Scharf, et al., “Insulated-Gate Planar Thyristors: II-Quantitative Modeling,” IEEE Transactions on Electron De
Iida Akihiro
Imanishi Kazuo
Fenty Jesse A
Kabushiki Kaisha Toshiba
Lee Eddie
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