Otis Elevator Company

Sven-Oliver Rainer Kersten

Helmut L Schroder-Brumloop

An elevator drive circuit is used for maintaining the voltage across first and second serially connected capacitors having first and second ends. The circuit comprises an active stabilizer for substantially maintaining a predetermined value of the voltage at a connection node of the capacitors. The active stabilizer provides compensation in response to deviations from the predetermined value of the voltage at the connection node.

Active stabilization of serially connected capacitors in high voltage

Drivers for field-controlled switches are powered and switched on and off by the same combined command and power signal which consists of a command signal modulated by a clock signal forming a command envelope including a train of clock pulses. The invention prevents power from being lost by refreshing power during the PWM low state, such that the command high state pulses need not be used for restoring power. Power and a command to a field-controlled driver is provided by a combined command power signal consisting in the on-state of clock pulses, the groups being a function of switch signal pulse width, and in the off-state of absence of clock pulses. During the off-state of the driver, power is refreshed. In addition, by integration the clock pulses a dead time occurs within the driver circuit, while the driver is being switched on with different time constants.

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Berlin, Germany

Sven-Oliver Rainer Kersten