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Temperature and Voltage Compensation Circuit for Constant Energy Hammer Drivers

IP.com Disclosure Number: IPCOM000048946D
Original Publication Date: 1982-Apr-01
Included in the Prior Art Database: 2005-Feb-09
Document File: 3 page(s) / 48K

Publishing Venue

IBM

Related People

Arnold, RW: AUTHOR [+4]

Abstract

The energy delivered to an actuator by a saturated current driver is a function of the driver supply voltage, resistance and inductance of the actuator coil, and the duration of the hammer firing pulses. Variations in the input electrical energy are primarily caused by changes in the supply voltage, and by changes in the actuator coil resistance because of heating effects. This circuit compensates for temperature and voltage variations, to keep input energy nearly constant, by changing the firing pulse width as a function of the driver supply voltage and hammer bank temperature.

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Temperature and Voltage Compensation Circuit for Constant Energy Hammer Drivers

The energy delivered to an actuator by a saturated current driver is a function of the driver supply voltage, resistance and inductance of the actuator coil, and the duration of the hammer firing pulses. Variations in the input electrical energy are primarily caused by changes in the supply voltage, and by changes in the actuator coil resistance because of heating effects. This circuit compensates for temperature and voltage variations, to keep input energy nearly constant, by changing the firing pulse width as a function of the driver supply voltage and hammer bank temperature.

As seen in Fig. 1, this circuit will fire the hammer driver at time T0, if the driver voltage and hammer bank temperature are at their nominal values. If the driver voltage decreases below its nominal setting or should the hammer bank temperature rise, then the compensation circuit will begin firing the driver sometime during the period T1 to T0. The driver will begin firing during the period T0 to T2 if the hammer bank temperature falls below its nominal temperature or if there is an increase in the driver voltage. The exact driver initiation time is determined by the actual driver voltage and bank temperature that exist when the triggering signal occurs. The total firing time, from driver initiation to driver turn-off at time T3, is such that the energy delivered to the actuator remains nearly constant regardless of driver voltage or hammer bank temperature.

The compensation circuit consists of a current source 10 (Fig. 2), a timing capacitor 11, a pre-charging circuit 12 for capacitor 11 and a voltage comparator
13. The circuit operation is as follows : Prior to the falling-edge of the triggering input pulse, the precharging circuit keeps timing capacitor 11 initially charged to a voltage V(c)= 6(R9) divided by R8+R9. When the trigger pulse occurs, the output from NAND gate 14 assumes a "HIGH" logic state (off condition of the open collector output dev...