JP2006108757A - Ccd driving circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a CCD driving circuit for which cost reduction and shortening of time for design can be realized by enabling commonly using a circuit for a plurality of CCD image sensors having different driving performance. <P>SOLUTION: The circuit is provided with a driving signal generator 13 for generating a driving signal to be outputted to a CCD image sensor 2, a driving performance information acquiring section 11 for acquiring CCD driving performance information, and a control unit 12 for causing the generator 13 to generate a driving signal consisting of driving performance corresponding to the driving performance information acquired by the means 11. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a CCD drive circuit for driving a CCD image sensor.

A conventional CCD drive circuit is driven by connecting a CCD drive device or a C-MOS logic device dedicated to the CCD image sensor in parallel according to the drive frequency of the CCD image sensor to be driven. Further, as disclosed in Patent Document 1, in the CCD driving LSI 5 that outputs the first signal R for driving the CCD image sensor 6, a second signal NR having a phase opposite to that of the first signal R is output as a dummy. Further, a CCD driving device is proposed in which a capacitive load C equivalent to the input capacitance of the CCD image sensor 6 to which the first signal R is input is connected to the output of the second signal NR.
Japanese Patent Laid-Open No. 9-181975

  However, a dedicated CCD drive device is expensive and is not generally used, and a C-MOS logic device has a limited drive capability, so the number of parallel connections must be changed according to the drive frequency. is there. For this reason, in general, a CCD drive circuit is created for each product and mounted on the product. However, creating a CCD drive circuit for each product increases the cost and reduces the design time. However, there is a problem that it takes a long time. Further, it has been difficult to make the CCD drive circuit common so as to be compatible with a plurality of products. Designing a CCD drive circuit in accordance with a CCD image sensor with a high frequency will increase the drive capability even if it is intended to be shared, which increases the cost of EMI (Electro magnet Interference) measures. End up.

  The present invention has been made in order to solve the above problems, and provides a CCD driving circuit that can reduce the cost and shorten the design time by making a circuit common to a plurality of CCD image sensors having different driving capabilities. It is intended to do.

The invention according to claim 1 of the present invention is a CCD driving circuit for driving a CCD image sensor,
Drive signal generating means for generating a drive signal to be output to the CCD image sensor;
Drive capability information obtaining means for obtaining CCD drive capability information;
Control means for causing the drive signal generating means to generate the drive signal corresponding to the drive ability information obtained by the drive ability information obtaining means.

  In this configuration, when the drive capability information acquisition unit acquires the CCD drive capability information, the control unit causes the drive signal generation unit to generate a drive signal having a drive capability according to the CCD drive capability information.

  According to a second aspect of the present invention, there is provided the CCD drive circuit according to the first aspect, wherein the control means is configured so that the image reading device provided with the CCD image sensor is in a standby state. The drive signal generating means is controlled so that the drive capability of the drive signal is lowered.

  In this configuration, when the image reading apparatus enters a standby state, the control unit controls the drive signal generation unit to reduce the drive capability of the drive signal.

  According to a third aspect of the present invention, there is provided the CCD drive circuit according to the second aspect, wherein the drive capability information is obtained at a timing when the image reading device provided with the CCD image sensor is turned on or released from sleep. Based on the drive capability information obtained by the means, the control means causes the drive signal generating means to generate the drive signal.

  In this configuration, when the image reading apparatus provided with the CCD image sensor is turned on or when the sleep mode is released, the control unit generates a drive signal in the drive signal generation unit.

According to a fourth aspect of the present invention, there is provided the CCD drive circuit according to any one of the first to third aspects, wherein the drive signal generation means includes a plurality of signal generation circuits connected in parallel. , The output of each signal generation circuit is assembled and output to the CCD image sensor as the drive signal,
The control means varies the number of the signal generation circuits to be driven according to the driving ability information obtained by the driving ability information obtaining means.

  In this configuration, the control unit drives the signal generation unit so that the number of signal generation circuits differs according to the driving capability information acquired by the driving capability information acquisition unit, and collects the outputs from the signal generation circuits. Are output as drive signals to the CCD image sensor.

  Further, the invention according to claim 5 is the CCD drive circuit according to claim 4, wherein the drive signal generation means outputs from the point where the signal generator outputs, and outputs from another signal generator. Is the same length for all the signal generators.

  In this configuration, the distance from the output point of the signal generation unit in the drive signal generation unit to the set point where the outputs from the other signal generation units gather is set to the same length for all the signal generation units. In this way, a drive circuit with less skew is realized while avoiding the influence of reflected waves.

  The invention according to claim 6 is the CCD drive circuit according to any one of claims 1 to 5, wherein the drive capability information obtaining means is configured to provide model information or drive frequency of the CCD image sensor. A driving capability storage unit for storing the corresponding driving capability, and a driving capability reading unit for reading out the driving capability according to the model information or the driving frequency information of the CCD image sensor from the driving capability storage unit as the driving capability information It is.

  In this configuration, in the drive capability information obtaining unit, the drive information reading unit reads the drive capability according to the model information or the drive frequency of the CCD image sensor from the drive capability storage unit so that the drive capability information is obtained. It has become.

  According to the first aspect of the present invention, since a drive signal having a driving capability adapted to each CCD image sensor can be output to the CCD image sensor, the circuit is common to a plurality of CCD image sensors. Therefore, cost reduction and design time reduction can be realized.

  According to the second aspect of the present invention, when the image reading apparatus is in a standby state, the EMI countermeasure can be simplified by reducing the drive capability of the drive signal.

  According to the third aspect of the present invention, when the image reading apparatus provided with the CCD image sensor is turned on, or when the sleep is released, the drive capability of the drive signal output to the CCD image sensor is reset. Therefore, even if the waveform of the drive signal used so far is disturbed for some reason, it will be corrected to an appropriate drive signal, and the CCD image sensor will be driven and controlled accurately. Can do.

  According to the fourth aspect of the present invention, the drive capability of the drive signal can be changed with a simple circuit.

  According to the fifth aspect of the present invention, it is possible to realize a drive circuit with less skew while avoiding the influence of reflected waves.

  According to the sixth aspect of the present invention, if the driving capability according to the model information or the driving frequency of the plurality of CCD image sensors is stored in advance in the driving capability storage unit, the driving information reading unit is used as the driving capability storage unit. Thus, it is possible to easily generate a drive signal corresponding to the drive capability of the CCD image sensor to be driven by reading drive capability information corresponding to the drive frequency of the CCD image sensor to be driven.

  A CCD driving circuit according to an embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a schematic configuration of a CCD drive circuit according to the first embodiment of the present invention. The CCD drive circuit 1 according to the present invention includes a drive capability information acquisition unit 11, a control unit 12, and a drive signal generation unit 13.

  The drive capability information acquisition unit 11 stores model information indicating each type of one or more CCD image sensors (hereinafter simply referred to as model information), and information indicating the model-specific drive capability of the CCD image sensor. This model is based on the driving capability storage unit 111 that stores (hereinafter referred to as driving capability information) in association with each model information and model information input from a CPU (not shown) or model information input from an operator. A driving capability reading unit 112 that reads driving capability information corresponding to the information from the driving capability storage unit 111 is provided. The driving capability information is, for example, information set in advance according to the driving frequency of each CCD image sensor, and how many signal generation circuits (described later) provided in the driving signal generation unit 13 are driven. It is information on what to do.

  The control unit 12 controls the drive signal generation unit 13 based on the drive capability information read from the drive capability storage unit 111 by the drive capability reading unit 112, and generates a drive signal suitable for each model of the CCD image sensor. Generated by the unit 13. That is, the control unit 12 drives the signal generation circuit in the drive signal generation unit 13 by the number indicated by the drive capability information, and causes the drive signal generation unit 13 to generate a drive signal for the CCD image sensor.

  The drive signal generation unit 13 generates a drive signal to be output to the CCD image sensor. As described above, the drive signal generation unit 13 generates a drive signal suitable for each model of the CCD image sensor 2 connected to the CCD drive circuit 1 under the control of the control unit 12, and generates the generated drive. The signal is output to the CCD image sensor 2 according to the reference clock.

  FIG. 2 is a diagram showing an outline of the internal configuration of the drive signal generator 13. The drive signal generation unit 13 includes drive signal generation circuits 130, 131, 132, and 133 including tri-state buffers and the like. The drive signal generation circuits 130, 131, 132, 133 are connected in parallel to each other, and the outputs of the drive signal generation circuits 130, 131, 132, 133 are collected and output to the CCD image sensor 2 as drive signals. ing.

  Each of the drive signal generation circuits 130, 131, 132, and 133 receives the reference clock signal CLK and the corresponding one of the select signals S0, S1, S2, and S3 output from the control unit 12, and the drive signal. The output of each of the generation circuits 130, 131, 132, 133 is turned on / off individually according to the level of the select signal from the control unit 12. That is, the control unit 12 drives the drive signal generation circuits for the number indicated by the drive capability information by switching the level of each select signal output to each of the drive signal generation circuits 130, 131, 132, 133. Is configured to do.

  Further, the pattern length L from each point a at which each of the drive signal generation circuits 130, 131, 132, 133 outputs to the set point b at which the outputs from these drive signal generation circuits 130, 131, 132, 133 are collected. Are the same length for all of the drive signal generation circuits 130, 131, 132, 133. By aligning the pattern length L in this way, the influence of the reflected wave is avoided and the skew is reduced. Preferably, each pattern length should be 10% or less of the pattern length L.

  The drive control of the drive signal generator 13 by the controller 12 will be further described. FIG. 3 is a timing chart of the reference clock signal and the select signal input to the drive signal generation circuits 130, 131, 132, and 133 and the output signal of the drive signal generation circuits 130, 131, 132, and 133.

  For example, in the case where the control unit 12 drives three drive signal generation circuits of the drive signal generation unit 13 based on the drive capability information read from the drive capability storage unit 111 by the drive capability reading unit 112 in FIG. This will be described with reference to FIG. In this case, the control unit 12 sets the select signal output to the drive signal generation circuit to be driven to High, turns on the output switch of each drive signal generation circuit, and selects the select signal for the drive signal generation circuit that is not driven. Is set to Low to turn off the output switch of the drive signal generation circuit. In FIG. 3, in order to drive the drive signal generation circuits 130, 131, 133, the select signals S 0, S 1, S 3 input to these drive signal generation circuits 130, 131, 133 are set to High and input to the drive signal generation circuit 132. This shows a state in which the select signal S2 to be set is Low.

  When the reference clock signal is input to each of the drive signal generation circuits 130, 131, and 133 in the above state, the drive signal generation circuits 130, 131, and 133 whose output switches are turned on receive the reference clock signal CLK. The output signals D0, D1, and D3 having the following phases are output, and the output signal D2 indicating high impedance is output from the drive signal generation circuit 132 in which the output switch is turned off. Then, the outputs from the drive signal generation circuits 130, 131, 132, and 133 are collected at the set point b and output to the CCD image sensor 2 as drive signals.

  In this way, the CCD drive circuit 1 can generate a plurality of patterns of drive signals by causing the control unit 12 to drive the drive signal generation circuits 130... As many as indicated by the drive capability information. If the driving capability information corresponding to the driving capability of the CCD image sensor corresponding to the model information of each image reading device is stored in the unit 111, a driving signal having a driving capability corresponding to each CCD image sensor to be driven is received. It can be generated and output to the CCD image sensor. Thereby, it is possible to make the circuit common to a plurality of image reading apparatuses, and it is possible to realize cost reduction and design time reduction of the CCD drive circuit 1.

  FIG. 4 is a diagram showing an application example of the CCD drive circuit 1. In addition, about the structure similar to the said 1st Embodiment, the same code | symbol is attached | subjected and description is abbreviate | omitted. The CCD drive circuit 1 according to the second embodiment is provided in the CCD image sensor 2 so that the drive frequency of the CCD image sensor 2 is lowered when the image reading apparatus provided with the CCD image sensor 2 is in the sleep state. The drive signal to be output is changed.

  The CCD drive circuit 1 is configured such that an operation mode signal indicating the operation state of the image reading apparatus is input from a mode monitoring unit 14 such as a CPU (not shown) to the drive capability reading unit 112. The mode monitoring unit 14 monitors what operation mode (full operation state, sleep (standby) state, power on / off state, etc.) the image reading apparatus provided with the CCD image sensor 2 is in. The drive capability storage unit 111 also includes drive capability information when the image reading device is in a full operation state, and drive capability information when the image reading device is in a sleep state (more than the drive capability during full operation). Information indicating low drive capability, and drive capability information set for the purpose of driving at a drive frequency lower than the drive frequency during full operation) is stored for each model of each CCD image sensor.

  Under the above configuration, when an operation mode signal indicating that the image forming apparatus has shifted to the sleep state is output from the mode monitoring unit 14 to the drive capability reading unit 112, the drive that has received the operation mode signal is received. The capability reading unit 112 reads the driving capability information at the time of sleep corresponding to the model of the CCD image sensor 2 that is currently driven from the driving capability storage unit 111. The control unit 12 controls driving of each of the drive signal generation circuits 130, 131, 132, and 133 of the drive signal generation unit 13 based on the read drive capability information at the time of sleep, thereby driving the sleep state drive signal. Is generated by the drive signal generation unit 13 and the drive signal is output to the CCD image sensor 2.

  Further, when an operation mode signal indicating that the image forming apparatus has been released from sleep is output from the mode monitoring unit 14 to the driving capability reading unit 112, the driving capability reading unit 112 receives the driving capability from the driving capability storage unit 111. The driving capability information at the time of full operation corresponding to the model of the CCD image sensor 2 that is currently driven is read out, and at the timing when the sleep is released, the control unit 12 reads the drive at the time of full operation. Based on the capability information, the drive signal generator 13 is caused to generate a drive signal for full operation.

  As described above, the EMI countermeasure can be simplified by reducing the drive capability of the drive signal of the CCD image sensor 2 when the image reading apparatus is in the sleep state.

  The present invention is not limited to the configuration of the above embodiment, and various modifications can be made. For example, in the above embodiment, the drive capability information acquisition unit 11 stores the model information of the CCD image sensor and the corresponding drive capability information in the drive capability storage unit 111 and is input to the drive capability reading unit 112. Based on the model information, the drive capability reading unit 112 reads the drive capability information corresponding to the model information from the drive capability storage unit 111. The drive capability storage unit 111 stores the frequency information of the CCD image sensor, And the driving capability information corresponding to the frequency information inputted to the driving capability reading unit 112 is read by the driving capability reading unit 112 from the driving capability storage unit 111. It may be. If the operator knows the drive frequency of the CCD image sensor by reading from the drive capability storage unit 111 or the like, the CCD drive circuit 1 can output a drive signal suitable for the CCD image sensor.

  In the second embodiment, the control unit 12 acquires the driving capability information from the driving capability information acquisition unit 11 at the timing when the image reading apparatus is released from sleep, and generates a driving signal to be generated by the driving signal generation unit 13. However, instead of this control, or together with this control, for example, the mode monitoring unit 14 detects that the image reading apparatus is turned on and outputs an operation mode signal to the drive capability reading unit 112. The control unit 12 may cause the drive signal generation unit 13 to generate a new drive signal based on the drive capability information read by the drive capability reading unit 112 from the drive capability storage unit 111. In this case, since the drive capability of the drive signal output to the CCD image sensor is reset when the image reading apparatus is turned on, the waveform of the drive signal used so far is disturbed for some reason. Even so, it is corrected to an appropriate drive signal, and the CCD image sensor can be accurately driven and controlled.

1 is a diagram showing a schematic configuration of a CCD drive circuit according to a first embodiment of the present invention. It is a figure which shows the outline of the internal structure of a drive signal generation part. 5 is a timing chart of a reference clock signal and a select signal input to each drive signal generation circuit and an output signal of each drive signal generation circuit. It is a figure which shows the application example of a CCD drive circuit.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 CCD drive circuit 2 Image sensor 11 Drive ability information acquisition part 111 Drive ability memory | storage part 112 Drive ability reading part 12 Control part 13 Drive signal generation part 130,131,132,133 Drive signal generation circuit 14 Mode monitoring part D0, D2, D1, D3 output signal S0, S1, S2, S3 select signal

Claims (6)

A CCD driving circuit for driving a CCD image sensor,
Drive signal generating means for generating a drive signal to be output to the CCD image sensor;
Drive capability information obtaining means for obtaining CCD drive capability information;
A CCD driving circuit comprising: a control unit that causes the driving signal generation unit to generate the driving signal according to the driving capability information acquired by the driving capability information acquisition unit.   2. The CCD according to claim 1, wherein the control means controls the drive signal generating means so that the drive capability of the drive signal is lowered when the image reading apparatus provided with the CCD image sensor is in a standby state. Driving circuit.   Based on the drive capability information acquired by the drive capability information acquisition unit at the time of power-on or sleep release of the image reading apparatus provided with the CCD image sensor, the control unit converts the drive signal into the drive signal. The CCD driving circuit according to claim 2, wherein the CCD driving circuit is generated by a generating unit. The drive signal generation means includes a plurality of signal generation circuits connected in parallel, collects the output of each signal generation circuit, and outputs the drive signal to the CCD image sensor,
4. The CCD drive circuit according to claim 1, wherein the control unit varies the number of the signal generation circuits to be driven according to the drive capability information obtained by the drive capability information obtaining unit.   The drive signal generation means is configured such that a distance from a point where the signal generation unit outputs to a set point where outputs from other signal generation units gather is the same length for all the signal generation units. Item 5. The CCD drive circuit according to Item 4.   The drive capability information acquisition means includes a drive capability storage unit that stores the drive capability according to the model information or drive frequency of the CCD image sensor, and the model capability information or drive frequency information of the CCD image sensor from the drive capability storage unit. 6. The CCD driving circuit according to claim 1, further comprising a driving capability reading unit that reads out the corresponding driving capability as the driving capability information.

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