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Multiple-CCFL inverter all output shutdown circuit in any failure happened

IP.com Disclosure Number: IPCOM000013901D
Original Publication Date: 2001-Nov-15
Included in the Prior Art Database: 2003-Jun-19
Document File: 2 page(s) / 43K

Publishing Venue

IBM

Abstract

A multiple-CCFL (cold-cathode fluorescent lamp) inverter that had a complete safety protection was developed. When it happened any failure detected the inverter shut off all the high-voltage outputs. The protection circuit controlled all the STOP signals of each controller IC using a multiple-input NAND gate buffer.

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Multiple-CCFL inverter all output shutdown circuit in any failure happened

    A multiple-CCFL (cold-cathode fluorescent lamp) inverter that had a complete safety protection
was developed. When it happened any failure detected the inverter shut off all the high-voltage
outputs. The protection circuit controlled all the STOP signals of each controller IC using a
multiple-input NAND gate buffer.

<Previous circuit>
If it happened any failure with a CCFL, the controller IC shut off the high-voltage output of the
failed CCFL only, however, the other CCFL were worked like as a normal condition. It was certainly
abnormal condition and it cannot be judged whether it was completely safe or not. We thought it was
not a perfect safety protection.

<New circuit>
It was connnected each IC reference-voltage-out (VREF_OUT) to each IC STOP signal input through a
6-input NAND gate buffer like a schematics. If it happened any failure with a CCFL, the error
detected IC VREF_OUT went to inactive, the STOP signals of all IC went to active, then all the
controller IC stopped working and all the high-voltage outputs were shut off. The inverter could not
restart without reset signal input. It was a completely safety protection.

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