DD259482A1 - INTEGRATED CIRCUIT ARRANGEMENT FOR CONTROLLING A LED LIGHT PRINTER - Google Patents

Abstract

The invention finds application in integrated circuit technology, in particular for driving LEDs in Lichtdruckkoepfen. The outputs of the circuit arrangement have current source character and thus allow the direct control of LED. Its digital programmability allows the compensation of brightness tolerances of the LED. Its digital programmability allows the compensation of brightness tolerances of the LED. An analog control input allows you to set the sum of all output currents. By a serial data interface, the circuit arrangement can be cascaded arbitrarily.

Description

Figure 1 shows an embodiment of the solution with 3-bit programmable current outputs. The shift register cells SRZ1 ... SRZn realize with the serial data input DE and the data output DA the serial data interface of the circuit arrangement. The shift clock C controls the synchronous data transfer and output of the shift register cells. With the address inputs Ac... Aa, in each case all those memory cells of different outputs are addressed simultaneously, which are assigned to equivalent current sources. If z. B. the address input Aa is activated, all current sources with the valence a (SQ1 a, SQ2a ... SWna) are programmed according to the respective shift register content. With the result of the logical AND operation of the respective memory cell contents with the information at the current enable control input Z, analog switches are actuated which switch the analog control voltage to AE to the corresponding current sources. Thus, according to the voltage at AE, all the output currents are controlled analogously to their digitally adjusted value.

Claims (1)

I · Claim: Integrated circuit arrangement for controlling an LED light printer, comprising a shift register, a subsequent memory unit and associated output stages, characterized in that the memory unit associated with each shift register cell (SRZn) of the shift register consists of memory cells (Tnc.Tna), each memory cell (Tnc. Tna) one of a plurality of mutually weighted, a common circuit output (SAn) forming current sources (SQna ... SQnc) is assigned and all the memory cells (T 1 c.Tnc, T2b ... Tnb, T1 a ... Tna) the different Shift register cells (SRZ1 ... SRZn) and thus different circuit outputs (SA1 ... SAn) are assigned, but with current sources of equal significance (SQ 1c.SQnc, SQ2b ... SQn b, SQ 1a, .. SQn a) are linked , are connected to the same address input (Ac, Ab, Aa). , , For this 1 page drawing Field of application of the invention The invention finds application in integrated circuit technology, in particular for the control of LEDs in light printheads. Characteristic of the known state of the art According to US-PS 4091377 a digital display drive circuit is known, consisting of a shift register, which is divided into a plurality of shift register cells, wherein each shift register cell is associated with a memory having a corresponding output stage. Only one output of the circuit is activated. With this arrangement, there is no possibility of digital programmability of the outputs and no analog control of the output. Known technical solutions for controlling an LED printer have voltage outputs. You need an external resistor for each LED to be controlled. Digital programmability of the outputs to compensate for the manufacturing differences in the brightness of the LED via the control of the pulse duration of the output current. As a result, the illuminated area per light pulse is not constant, which has a negative effect on the print quality. Object of the invention The aim of the invention is to provide an integrated circuit arrangement for driving an LED printhead, which allow an improvement in the print quality of the LED printer, as well as a material saving in the manufacture of the circuit arrangement allowed. Explanation of the essence of the invention The invention has for its object to provide an integrated circuit arrangement that allows direct control of the LED, a digital programmability at a constant pulse length and a cascadability of the circuit allows. According to the invention, the object is achieved in that each shift register cell of a serial and cascadable externally shift register are assigned in like manner memory cells, each one of a plurality of current sources drives, which are weighted to each other and form a common circuit output. All memory cells which are assigned to different shift register cells and thus to different circuit outputs, but which drive current sources of the same significance, each have the same address which can be set at the address inputs of the circuit arrangement. The currents of all output current sources of the circuit arrangement can be adjusted in parallel via the analog control input, proportional to the significance of the sources. All output current sources are activated jointly by a digital control input of the circuit arrangement according to the analog control voltage and the respective content of their associated memory cell. embodiment The character of the invention will be shown with reference to an embodiment. FIG. 1 shows an integrated circuit arrangement for controlling an LED light printer with analog controllable 3-bit programmable current outputs. '