Electronic Theatre Controls, Inc.

Eric W Suomi

John P Thurk

Eric G Rasmussen

Bradley J Brunker

Thomas M Stankey

Joseph W Garvey

A current sensing transformer having a low impedance primary winding is connected in series with a filter and load circuit supplied with output current by a high frequency switching PWM power supply such as a sinewave dimmer. Sensed output current is supplied to a microprocessor based programmable controller. The controller performs a routine including a family of overcurrent tests. Tests of the family are satisfied by the presence of different output current values for different time durations. At least one of the tests is enabled only at low requested output voltages or dimming levels. In response to satisfaction of any of the tests, a series power switching stage of the power supply is rendered nonconductive to shut down the power supply.

Low voltage overcurrent protection for solid state switching system

Current sensing resistors are connected directly to output terminals of MOSFETs forming the series switching stage of a PWM sinewave dimmer. An analog sensed current signal is coupled through an EMI resistant current link to comparators that provide an overcurrent indication in response to an overcurrent condition. A logic circuit overrides PWM control signals from a programmable controller, and operates drivers to render the series switching stage nonconductive and to render a clamp switching stage conductive until after the end of the current PWM duty cycle power on segment. The logic circuit sends an overcurrent signal through an optocoupler to an input of the programmable controller. The input of the controller is polled at a clock frequency for overcurrent signals and if the count exceeds a limit in any half cycle, or a maximum sum in sixteen half cycles of the AC supply, the series switching stage is rendered nonconductive and the clamp switching stage is rendered conductive pending a reset signal.

Overcurrent protection for solid state switching system

An input line filter separates an ac sinusoidal power source from a power switching stage having a series switching section and a clamp switching section. Both the series switching section and a clamp switching section include complementary pairs of high power and high speed MOSFETs. The series switching section is connected in series between the input line filter and the inductor of an output load filter between the power switching stage and a load. The clamp switching section is connected to shunt the inductor and load. Synchronous operation is achieved by alternately operating the series and clamp switching sections to conductive conditions at a high pulse width modulation frequency. The duty cycle is selected to provide a sinusoidal output waveform with a desired amplitude. A microprocessor based programmable controller provides control signals for alternate conduction of the series and clamp switching sections. A dead time interval stored in memory in the controller separates the control signals for reliable and efficient operation. The dead time interval may be constant, or may be varied in accordance with load power variations.

Sinewave dimmer control method

A driver circuit is provided for a stepper motor which utilizes a processor that outputs a PWM signal. The driver circuit includes an H-bridge circuit having first and second inputs, and a switching circuit having an input and an output. The first H-bridge input and the switching input connect to the PWM signal output from the processor, and the switching output connects to the second H-bridge input. The switching circuit performs an inversion of a duty cycle of the PWM signal when the PWM signal is present, and a non-inversion of the duty cycle when the PWM signal is not present.

Circuit for driving a stepper motor and method of controlling a stepper motor driver

A heat sink with fins has a flat, planar surface soldered to a metallic layer at one surface of a flat, planar ceramic layer. The opposite surface of the ceramic layer has a metallic pattern including base areas for high power, high frequency load switching MOSFETs. Lead frames are soldered between the lead frame base areas and base contact areas of the MOSFET packages. Thermal conduction between the MOSFETs and the heat sink dissipates the heat from switching losses. A gate drive circuit board for the load switching system is supported spaced from the and is separated from the MOSFETs by a thermally blocking air gap, with the component side of the gate drive circuit board facing away from the MOSFETs. Spade terminals of the lead frames extend through openings in the gate drive circuit board to route high power signals independently of the gate driver circuit board.

Power module package for high frequency switching system

A self contained multiple dimming channel package includes a housing with a main power circuit board supported on its bottom wall and a control circuit board extending laterally and vertically to baffle air flow through the housing. A cross flow cooling fan forces air through an opening in the control board and across power switching modules and toroidal chokes mounted to the main board. Each power switching module includes a heat sink with fins parallel to the air flow, and the chokes are mounted in rows with their central openings aligned with the air flow. The power switching modules include circuits attached to the heat sinks with terminals releasably plugged into mating connectors on the main board. Circuit breaker switches are snapped into place in the housing. The front corners of the housing are provided with integral mounting bracket and handle members.

Dimmer pack

Power for one or more luminaire accessories is extracted from a series of lamp operating pulses provided by a phase angle dimmer. A DC power supply is connected to the output of the dimmer to develop and store DC accessory power. A lamp controller is connected to the output of the dimmer to transfer power from the lamp operating pulses to the lamp. The lamp controller has a variable pulse transfer characteristic for providing lamp power without lamp performance degradation caused by accessory power variations. The variable pulse transfer characteristic can be implemented by a switching device that interrupts or blocks selected portions of the lamp operating pulses. The pulse transfer characteristic maintains constant apparent lamp brilliance independent of variations in accessory power requirements. In an off or in a preheat condition, power transfer to the lamp is reduced to prevent emission of a visible light beam. In a full brilliance condition, the lamp operating pulses are essentially unmodified by the lamp controller.

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Madison, WI, United States of America

Eric W Suomi