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Protected MOSFET Bleeder

IP.com Disclosure Number: IPCOM000242507D
Publication Date: 2015-Jul-21
Document File: 2 page(s) / 18K

Publishing Venue

The IP.com Prior Art Database

Related People

Bob Lazaravich: INVENTOR

Abstract

The present embodiments enable the use of a protected MOSFET for the bleeder instead of a switch (transistor or MOSFET) and a resistor. Protected MOSFETs are commercially available devices which include some level of self-protection.

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Protected MOSFET Bleeder

By:  Bob Lazaravich

A small module that has a number of power supply bleeder circuits in it.  In one embodiment 4 – 8 power bleeder circuits are comprised within the module. 

It is well known to use bleeders in modern digital logic to get the power supplies to go all the way down to 0V when power is removed.  In the old days you did this to remove lethal voltages.  Nowadays we do this to make sure that a power supply output starts at 0V instead of say .7 or .8V or higher.  Often times without a bleeder it can take minutes for the voltage to bleed off. 

We want the power supplies to start at zero for 2 reasons. 

1.      To make sure that we can sequence designs with multiple power supplies correctly.  You need to start at 0V to do this.

2.      We want to be sure that logic devices including initialization circuits actually run the initialization process.  Sometimes if the power turns on and the power supply output voltage is above some threshold (from the last power cycle) the devices will skip initialization.

The present embodiments enable the use of a protected MOSFET for the bleeder instead of a switch (transistor or mosfet) and a resistor.  Protected MOSFETs are commercially available devices which include some level of self-protection.  The self-protection may include current limiting, temperature limiting, ESD (electrostatic discharge) protection or a current mirror.

The protected mosfet has advantages. 

1.      It works VERY quickly to bleed a supply be...