The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Oct. 21, 2003
Filed:
Mar. 23, 2001
Brian R. Pelly, Palos Verdes Estates, CA (US);
International Rectifier Corporation, El Segundo, CA (US);
Abstract
An active filter reduces the common mode current in the ground wire of a PWM controlled motor drive circuit. The active filter is, in part, integrated into an integrated circuit chip and contains a buffer amplifier which drives two junction type or MOSFET transistors linearly to divert common mode current from a ground wire and through the transistors. The transistors are connected between positive and negative d-c busses which supply d-c power to a PWM inventor which drives an a-c motor, producing the common mode ground current in its grounded frame. A current transformer monitors the common mode current and its output is coupled to the input of the buffer amplifier to control the transistors. An internal power supply for the amplifiers is formed at the nodes between two current sources and two zener diodes which are connected between the d-c bus conductors. Headroom control circuits are disclosed to insure sufficient headroom voltage for each of the transistors under all input a-c voltage conditions.