Browse Prior Art Database

Print Head Thermal Protection Circuitry

IP.com Disclosure Number: IPCOM000036871D
Original Publication Date: 1989-Nov-01
Included in the Prior Art Database: 2005-Jan-29
Document File: 2 page(s) / 30K

Publishing Venue

IBM

Related People

Do, PK: AUTHOR [+3]

Abstract

Disclosed is a low-cost circuit enabling a microprocessor to monitor the thermal state of an actuator coil, such as a print head.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 100% of the total text.

Page 1 of 2

Print Head Thermal Protection Circuitry

Disclosed is a low-cost circuit enabling a microprocessor to monitor the thermal state of an actuator coil, such as a print head.

The circuit works on the principle of change in resistance, i.e., resistance is directly proportional to temperature. The schematic is shown in the figure. From the change in resistance principle V1 at the comparator, input is inversely proportional to the resistance of the actuator. Therefore, if V2 is constructed as a reference, the comparator output can be made to change states when RA increases sufficiently.

T1 has been chosen such that when saturated, its voltage drop is negligible. The diode D1 is provided to clip inductive voltage spikes, thus protecting the comparator. The capacitor C1, is provided for filtering. The supply voltage Vss was placed common to both the load and reference to take advantage of voltage tracking.

This technique has been used effectively in the Proprinter product line and has correspondingly reduce microprocessor overhead and minimized cost.

1

Page 2 of 2

2

[This page contains 3 pictures or other non-text objects]