| 摘要 |
PURPOSE:To effectively prevent a change of printing density by providing a control counter, a data counter for outputting a reference density signal and a heating signal, a reference signal counter, a correction table memory for a value constituting a time sharing signal and a density data comparing circuit. CONSTITUTION:The reference clock signal from a terminal 14 and the current supply start pulse from a terminal 15 are supplied to an address counter 13. A control counter 17 is loaded with the preset concurrent heating value from a concurrent heating presetting source 18 in response to the current supply start pulse. A counter 19 counts the reference clock signal during a cooling period to a thermal head and the count value thereof is supplied to a correction table memory 21. This memory 21 preliminarily stores the optimum current supply pulse duty corresponding to the variation of the length of the cooling period caused by the variation of the transfer speed of recording paper. The current supply pulse duty-to-gradation characteristic read on the basis of the output count value of the counter 19 is supplied to a pulse generator 27. |
