Miscellaneous active electrical nonlinear devices – circuits – and – Signal converting – shaping – or generating – Current driver
Reexamination Certificate
2001-03-22
2004-12-28
Callahan, Timothy P. (Department: 2816)
Miscellaneous active electrical nonlinear devices, circuits, and
Signal converting, shaping, or generating
Current driver
C327S109000, C327S110000, C327S387000
Reexamination Certificate
active
06836161
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a semiconductor switch driving circuit, particularly relates to a semiconductor switch driving circuit suitable for controlling a semiconductor switch used for electrotherapy apparatus such as a defibrillator.
2. Related Art
For a device for a semiconductor switch which enables the control of high voltage, an insulated gate bipolar transistor (IGBT) is generally used.
A circuit for driving a semiconductor switch configured by this insulated gate bipolar transistor (hereinafter called IGBT) is connected via a photocoupler or a transformer so that the circuit is electrically insulated from a circuit part that directly drives a control signal and the gate of IGBT.
Referring to drawings, an example using a photocoupler and an example using a pulse transformer respectively of a conventional type semiconductor switch driving circuit will be described below.
FIG. 3
is a circuit diagram showing a semiconductor switch driving circuit using a photocoupler.
As shown in
FIG. 3
, a part that drives a switching device (IGBT)
208
a
at a first stage is composed of a photocoupler
201
a
, a comparator
202
a
, a positive voltage source
203
a
, transistors
204
a
and
205
a
, a negative voltage source
206
a
and a resistor
207
a
and a ground terminal is connected to a GND
1
. Also, a part that drives a switching device (IGBT)
208
b
at a second stage is composed of a photocoupler
201
b
, a comparator
202
b
, a positive voltage source
203
b
, transistors
204
b
and
205
b
, a negative voltage source
206
b
and a resistor
207
b
, a ground terminal is connected to a GND
2
and a driving circuit at the next stage or at the subsequent stages can be similarly composed.
FIG. 4
is a circuit diagram showing a semiconductor switch driving circuit using a pulse transformer.
As shown in
FIG. 4
, a part that drives a switching device (IGBT)
257
a
at a first stage connected to a secondary side of a pulse transformer
251
is composed of a transistor
255
a
, diodes
252
a
and
253
a
and resistors
254
a
and
256
a
, a part that drives a switching device (IGBT)
257
b
at a second stage is composed of a transistor
255
b
, diodes
252
b
and
253
b
and resistors
254
b
and
256
b
and a driving circuit at the next stage or the subsequent stages can be similarly composed.
However, the conventional type semiconductor switch driving circuit has the following problems.
The semiconductor switch driving circuit shown in
FIG. 3
is provided with the photocoupler, the positive voltage source, the negative voltage source and the GND at every stage of a driven switching device (IGBT). In a conventional type system of a multistage semiconductor switch, there is a problem of a time lag in the switching of a switching device (IGBT). When the timing of the switching is delayed, overvoltage is applied to a switching device in case switching devices are connected in series as shown in
FIG. 3
, also, in case switching devices are connected in parallel, over current is applied to a switching device and in any case, the switching device may be broken. Also, as the same number of the photocouplers, the positive voltage sources, the negative voltage sources and the grounds as the number of the stages of the switching devices (IGBT) are required, there is a problem that the scale of the circuit is large and the cost of the whole apparatus is high.
Also, the semiconductor switch driving circuit shown in
FIG. 4
cannot continuously supply positive voltage or negative voltage to the gate of the switching device (IGBT) to be driven. There is also a problem that switching to reverse bias (from positive voltage to negative voltage or from negative voltage to positive voltage) is slow.
Further, there are problems that positive voltage or negative voltage cannot be made to an independent value and the size of a transformer for low-frequency switching is large.
SUMMARY OF THE INVENTION
The invention is made to solve the problems of the prior art and the object is to provide a semiconductor switch driving circuit suitable for controlling a semiconductor switch which can continuously supply positive voltage or negative voltage to the gate of a switching device (IGBT) to be driven by the small number of parts, enables high-speed switching to reverse bias and is particularly used for electrotherapy apparatus because a lag in switching timing between each stage can be reduced.
To achieve the object, a semiconductor switch driving circuit according to a first aspect of the invention is based upon a semiconductor switch driving circuit provided with at least a transformer and is characterized in that a primary side area for controlling the primary current of the transformer according to a control signal for controlling a semiconductor switch is provided on the primary side of the transformer, a secondary side area for directly driving a switching device is provided on the secondary side of the transformer, voltage between the gate and the emitter of the switching device can be continuously kept positive, voltage between the gate and the emitter can be continuously kept negative and voltage between the gate and the emitter can be switched so that it is alternately positive and negative.
A semiconductor switch driving circuit according to a second and a third aspect of the invention is characterized in that the circuit is operated in synchronization with an input control signal because the primary side area is configured so that the primary side area receives a control signal, transmits power for controlling plural switching devices to the secondary side area and absorbs back electromotive force caused when current flowing in the transformer is cut off and the secondary side area is configured so that the secondary side area receives the power supplied from the primary side area, transmits the power for controlling the plural switching devices to the plural switching devices, the plural switching devices receive the power supplied to the secondary side area of the semiconductor switch driving circuit and cause or prevent current to flow for switching.
A semiconductor switch driving circuit according to a fourth aspect of the invention is characterized in that back electromotive force between a terminal at one end of a primary winding of a transformer and a terminal at the other end of the primary winding of the transformer can be inhibited by connecting the source of P channel MOSFET to a power terminal, connecting the drain of the P channel MOSFET to the anode of a diode, connecting the cathode of the diode to the terminal at one end of the primary winding of the transformer and as a result, conducting the P channel MOSFET.
A semiconductor switch driving circuit according to a fifth aspect of the invention is characterized in that when the primary side area receives an input control signal, it transmits power for controlling plural switching devices to a secondary side area and absorbs back electromotive force caused when current flowing in the transformer is cut off because a control signal input terminal is connected to the base of an NPN bipolar transistor via a resistor and a capacitor respectively connected in parallel, the base and the emitter of the NPN bipolar transistor are connected via a resistor, the emitter is connected to a ground terminal, the collector of the NPN bipolar transistor is connected to the gate of a P-channel MOSFET via a resistor, the gate and the source of the P-channel MOSFET are connected via a resistor, the source is connected to a power terminal, the drain of the P-channel MOSFET is connected to the anode of a diode, the cathode of the diode is connected to the drain of a N-channel MOSFET and a terminal of a primary winding of a transformer, the gate and the source of the N-channel MOSFET are connected via a resistor, the source is connected to a ground terminal, a control signal input terminal is connected to the gate of the N-channel MOSFET via a resistor, a control signal input terminal is connect
Akiyama Naoto
Inomata Masahiko
Tsumura Ikuhiro
Callahan Timothy P.
Luu An T.
Nihon Kohden Corporation
Sughrue & Mion, PLLC
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