Switching regulator for terminal printhead

Claim 1

A printing terminal having means for providing a hard copy display, comprising: (a) thermal printing means; (b) temperature indicating means located to indicate the temperature of the thermal printing means; and (c) switching regulator power supply means for providing a controlled voltage to the thermal printing means, comprising: (i) switching means for operatively connecting a voltage source in circuit with the thermal printing means; (ii) means for establishing a preselected reference level in response to a signal from the temperature indicating means representative of the temperature of the thermal printing means, (iii) bi-stable means, coupled to the switching means having a first output state to close the switching means and a second output state to open the switching means; and (iv) control means connected to turn the bi-stable means on when the controlled voltage is less than the preselected reference level and to turn the bi-stable means off when the controlled voltage exceeds the preselected reference level, causing the first and second output states, respectively, to occur.