Patent ID: 7559628

Claim:
An ink-jet recording head substrate which is mounted with electrothermal transducers producing thermal energy used for discharging ink and which drives the electrothermal transducers, comprising: an input portion to which a first voltage is input; a production unit configured to operate on the first voltage and produce a selection signal indicating driving or non-driving of the electrothermal transducer, wherein said production unit receives signals including image data through said input portion, and produces, as the selection signal, a block selection signal and a time-division selection signal for driving the electrothermal transducers; a conversion unit configured to convert the block selection signal and the time-division selection signal produced by the production means into the block selection signal and the time-division selection signal of a second voltage higher than the first voltage; a driving unit having a plurality of driving elements each of which is configured to operate on the second voltage and drive the electrothermal transducer in accordance with the block selection signal and the time-division selection signal of the second voltage; a detection unit configured to detect a voltage input from said input portion as the first voltage and output a detection signal if the first voltage is not a predetermined voltage level for driving said conversion unit; and a control unit configured to operate on the second voltage and keep the block selection signal or the time-division selection signal supplied to said driving unit under such a state as to indicate non-driving in a case where the detection signal is outputted, so that the block selection signal or the time-division selection signal output from said conversion unit is allowed to be supplied to said driving circuit only in a case where the first voltage is equal to or greater than the predetermined voltage level.