Miscellaneous active electrical nonlinear devices – circuits – and – Signal converting – shaping – or generating – Current driver
Reexamination Certificate
2000-03-09
2001-05-08
Wells, Kenneth B. (Department: 2816)
Miscellaneous active electrical nonlinear devices, circuits, and
Signal converting, shaping, or generating
Current driver
C327S108000, C327S109000, C327S304000
Reexamination Certificate
active
06229356
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a stabilized gate driver which comprises a current source transformer which comprises a primary coil and a secondary coil, and a gate driver unit which comprises a positive auxiliary voltage input and a negative auxiliary voltage input.
When a power semiconductor component, e.g. an IGB transistor, is controlled, it is important to keep the control voltage within certain values. Typically the voltage used for igniting an IGB transistor should not be lower than +13 volts. If the voltage used for controlling the power semiconductor is too low, the power semiconductor will not become completely saturated, which causes additional conducting losses in the power semiconductor. On the other hand, if the gate voltage exceeds +15 volts, the possible short-circuit current increases so much that it is no longer safe to cut it off quickly.
Considering the disturbance tolerance, the gate of the IGBT to be turned off should be rendered to the negative potential with respect to the emitter. This allows to prevent unintentional ignition of the power semiconductor caused by changes in the potential. A suitable range for turning the IGBT off is from about −5 to −15 volts. The turn-off voltage may vary within a wider range than the ignition voltage without interfering with the function of the power semiconductor.
Earlier voltages for controlling the power semiconductor have been generated with a current source transformer the secondary coil of which comprises a middle output. This way we obtain a bilateral symmetric voltage which does not, however, satisfy all the requirements set for controlling the power semiconductor. Since the voltage feeding the current source transformer has not been stabilized, the voltage may often vary too much, which is disadvantageous particularly on the positive side. Furthermore, this renders the structure of the transformer comprising a middle output unnecessarily complicated, which directly affects the costs of the solution in question.
BRIEF DESCRIPTION OF THE INVENTION
The object of the present invention is to provide a stabilized gate driver which eliminates the above-mentioned drawbacks and enables controlling of power semiconductors in a reliable manner. This object is achieved with a gate driver according to the invention which is characterized in that the gate driver also comprises a diode the anode of which is connected to the positive pole of the secondary coil of the current source transformer, a zener diode the cathode of which is connected to the cathode of the diode, resistance whose one pole is connected to the anode of the zener diode and the other pole to the negative pole of the secondary coil of the current source transformer, a first semiconductor switch the control electrode of which is connected to the point between the zener diode and the resistance, and the collector of which is connected to the cathode of the zener diode, a second semiconductor switch the control electrode of which is connected to the point between the zener diode and the resistance and the collector of which is connected to the negative pole of the secondary coil of the current source transformer and the emitter to the emitter of the first semiconductor switch, a first capacitance the first pole of which is connected to the collector of the first semiconductor switch and the second pole to the emitter of the second semiconductor switch, the first pole of the capacitance forming a positive voltage input which is connected to the positive auxiliary voltage input of the gate driver unit, and a second capacitance the first pole of which is connected to the emitter of the second semiconductor switch and the second pole to the collector of the second semiconductor switch, the second pole of the capacitance forming a negative voltage input which is connected to the negative auxiliary voltage input of the gate driver unit, in which case the point between the capacitances forms the zero potential between the positive and the negative auxiliary voltage input.
The invention is based on the idea that the gate driver can be made to function reliably by stabilizing the auxiliary voltages to be supplied to the gate driver unit which allows to generate a bilateral voltage the positive voltage output of which can be kept within the desired limits for igniting the power semiconductor reliably and keeping it in the line state. The positive voltage supply is stabilized using a simple voltage division connection combined with a current buffer. An advantage of the gate driver according to the invention is that the positive auxiliary voltage can always be kept within the desired voltage limits regardless of the changes in the output voltage of the current source transformer. Changes in the output voltage of the current source transformer affect only the magnitude of the negative power supply of the gate driver according to the invention, for which a wider range of variation is allowed.
REFERENCES:
patent: 4375701 (1983-03-01), Hanson
patent: 5224026 (1993-06-01), Okayama
patent: 5514921 (1996-05-01), Steigerwald
patent: 5675244 (1997-10-01), Piton
patent: 5684681 (1997-11-01), Huh
patent: 6128203 (2000-10-01), Canizales
ABB Industry OY
Dinh Paul
Dykema Gossett PLLC
Wells Kenneth B.
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