Browse Prior Art Database

ENHANCED OVERCURRENT PROTECTION SYSTEM

IP.com Disclosure Number: IPCOM000010400D
Publication Date: 2002-Nov-26
Document File: 9 page(s) / 5M

Publishing Venue

The IP.com Prior Art Database

Abstract

Existing “soft hiccup” overcurrent protection circuits do not allow a power controller to recover from an overcurrent condition (even if the overcurrent condition has been cleared), unless the system is restarted by completely discharging the soft start capacitor. As an overcurrent event is detected, output gate blanking is removed (to minimize gate on time in overcurrent) and from that point, the system is subject to tripping off when it detects the current spike at the leading edge of the gate pulse that results. Furthermore, most “soft hiccup” overcurrent protection circuits are unable to recover from an overcurrent condition when the output driver blanking is disabled because it can not discern between an actual over current condition and a normal leading edge switching spike. If blanking is not disabled, then if an overcurrent condition persists, the device is subjected to more and possibly damaging power dissipation. However, rapid response to overcurrent conditions is a highly desirable market feature and basic customer requirement for power controllers. Thus, there is a need for a means to quickly allow a power controller to recover from an overcurrent event. The concept proposed is to disable blanking to reduce FET power dissipation, but re-assert it every n cycles to restore precision of detection. It represents a compromise between recovery response time and FET power limiting during load fault conditions.

This text was extracted from a Microsoft Word document.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 32% of the total text.

Enhanced overcurrent protection system

Existing “soft hiccup” overcurrent protection circuits do not allow a power controller to recover from an overcurrent condition (even if the overcurrent condition has been cleared), unless the system is restarted by completely discharging the soft start capacitor.� As an overcurrent event is detected, output gate blanking is removed (to minimize gate on time in overcurrent) and from that point, the system is subject to tripping off when it detects the current spike at the leading edge of the gate pulse that results.         Furthermore, most “soft hiccup” overcurrent protection circuits are unable to recover from an overcurrent condition when the output driver blanking is disabled because it can not discern between an actual over current condition and a normal leading edge switching spike. � If blanking is not disabled, then if an overcurrent condition persists, the device is subjected to more and possibly damaging power dissipation. However, rapid response to overcurrent conditions is a highly desirable market feature and basic customer requirement for power controllers.� Thus, there is a need for a means to quickly allow a power controller to recover from an overcurrent event.� The concept proposed is to disable blanking to reduce FET power dissipation, but re-assert it every n cycles to restore precision of detection.� It represents a compromise between recovery response time and FET power limiting during load fault conditions.

Background

What’s this “blanking” stuff all about?� � Let’s say you are out in the ocean on a small boat in the fog, and the possibility exists there might be much larger vessels in the immediate vicinity.� To sense proximity and direction, you sound a very loud multidirectional horn blast, then listen for an echo.� Since sound travels at approximately 600 mph, or 6 seconds for 1 mile, a 12 second delay between blast and echo implies a large reflective object 1 mile away.�

There is a fundamental flaw with this approach.� The transmitted sound is so loud that it overloads the sensitive receiving instrument (your ears), such that you cannot hear anything for the following 24 seconds.� What this means, in practice, is that you cannot sense another ship closer than 2 miles, not a particularly good situation.

What’s the solution?� You don a set of thick sound-blocking ear covers, transmit the signal, then remove them and listen.� It takes you but 3 seconds to remove the covers, so your practical minimum distance sensitivity has been improved to ¼ mile.� Within that range, you are dependent on visual means of detection.� Blocking the receiver during signal transmission is called “blanking”, so named because the early radar and sonar systems used long-persistence cathode ray tubes to convert the echo signal to a visual display.� You can see that this is not a new concept . . . it has probably been employed since the 1930’s.

The ideal system would have a range of 10 (...