Amtel Systems Corp.

Sms Advanced Power, Inc.

Richard B Drabing

William S Duvall

A switch-mode power supply has first and second switching transistors connected in series together and in parallel with the primary of a power transformer which alternately connect the primary winding of the power transformer across a DC potential. The bases of the switching transistors are each connected to a separate secondary winding of a control transformer the primary of which receives a control signal. Simultaneous conductance of the switching transistors is prevented. A control circuit providing the control signal is powered initially from charge derived from the power supply primary circuit and stored on a capacitor. A Schmitt trigger connects the capacitor to power the control circuit when the voltage across the capacitor rises to above a first predetermined level. Once the power supply begins to operate, semi-regulated power from the secondary circuit of the supply is connected via the Schmitt trigger to power the control circuit output. Current limiting is provided to reduce the duty cycle of the switching transistors when an overcurrent occurs. When the voltage applied to power the control circuit falls below a second predetermined level, the Schmitt trigger disconnects the control circuit from the capacitor to shut down the power supply. The control circuit restarts automatically, providing a 'burp mode' of operation. Supply output voltage is monitored by a comparator which is connected to the control circuit through an opto-coupler operated in a digital mode to provide high primary-to-second circuit isolation without requiring special circuit compensation.

Switch-mode power supply

Disclosed is a power line transmission system which generates a narrow band multi-frequency shift keyed signal having a first predetermined frequency representing a first state of information (e.g., a '0') and a second predetermined frequency representing a second state of information (e.g., a '1'). The system includes a power line connected between a transmitter and a receiver and the FSK narrow band signal is transmitted from the transmitter over the power line to the receiver which recovers the transmitted information. The system provides improvement over noise problems present in a power line and in addition provides multi-channel capability.

Power line communication system utilizing a local oscillator

A thermal message printer for printing a wide block of text which is produced with low cost printheads. The printer includes a thermal printer having a first number of fixed printheads equal in number to the lines to be printed on thermographic paper. Each of the fixed printheads has a second number of dot elements which are energized in a column fashion according to a pattern of dots to be energized from a matrix of dots for each of the characters. Control means are included for sequentially energizing selected ones of the dot heads in order to form the series of characters such that a wide block of text is printed.

Growing community of inventors

Los Altos, CA, United States of America

Richard B Drabing