Pulse width modulation and protection circuit
July 28, 2015. Estimated Expiration Date is calculated based on simple USPTO term provisions. It does not account for terminal disclaimers, term adjustments, failure to pay maintenance fees, or other factors which might affect the term of a patent.Patent ReferencesSolid state ballast High intensity discharge lamp self-adjusting ballast system with current limiters and a current feedback loop Dimming circuit having switching transistor protection means CMOS latch-up recovery circuit Dual channel current mode switching regulator Microcomputer based reclosing relay Lamp intensity control system having over-current protection Patent #: 5001398 InventorsApplicationNo. 508715 filed on 07/28/1995US Classes:361/94, With time delay protective means315/307, Automatic regulation361/59Circuit automatically reconnected only after the fault is clearedExaminersPrimary: Leja, Ronald W.Attorney, Agent or FirmForeign Patent References
International ClassH02H 003/00AbstractA pulse width modulation circuit includes a transistor pass element alternately switched on and off by an oscillator and connecting a power source to a load. Current through the transistor pass element is compared to a reference signal by a comparator. If the current through the transistor pass element exceeds the reference signal, the comparator generates a fault signal, and the transistor pass element is switched off for the remainder of the cycle. After a predetermined number of faults, the transistor pass element is switched off for a plurality of cycles. The pulse width modulation circuit prevents damage to the transistor pass element caused by the low initial resistance of the load and supplies sufficient current to slowly heat the load to steady state operation. This also allows for downsizing of the pass element for steady state conditions thereby saving product cost.Other References
Field of SearchVoltage regulator protective circuitsLoad shunting by fault responsive means (e.g., crowbar circuit) Current responsive Circuit automatically reconnected only after the fault is cleared Automatic reclosing With lockout means Current With time delay protective means With semiconductor circuit interrupter (e.g., SCR, Triac, Tunnel Diode, etc.) Including means to establish plural distinct current levels (e.g., high, low) SPECIAL APPLICATION Vehicle Head light systems WITH AUTOMATIC SHUNT AND/OR CUTOUT Automatic regulation Automobile Lighting circuits | |
