| 摘要 |
PURPOSE:To stably express a recording image with high accuracy so as to have a medium contrast, by providing a selection circuit so that the sum total of printing powers supplied to a heat generating element and a load resistor group always becomes almost constant. CONSTITUTION:An ON-selection member 26 is reversed by an inverter 31 and selected in a state thinned by a frequency dividing circuit 32 to be inputted to a shift register 33. The signal for turning the load resistor 37, which corresponds to a heat generating element to which no printing power is supplied, ON is stored in the shift register 33. A latch pulse 28 is simultaneously supplied to a latch circuit 4 and a latch circuit 34 and a strobe 27 is supplied to a driver NAND gate 35 and a driver NAND gate 5 in the same timing. By this method, power is almost simultaneously supplied to the heat generating element 2 and the load register 37. As mentioned above, even when the power supplied to the heat generating element varies, by controlling the power consumed by a load resistor group corresponding thereto, the whole power consumption of a thermal head becomes constant and, therefore, the variation in a power supply voltage is prevented and printing density can be stably controlled with high accuracy. |
