JP4836594B2 - Semiconductor laser driving device and image forming apparatus having semiconductor laser driving device - Google Patents

Description

  The present invention relates to a semiconductor laser driving device that performs driving control of a semiconductor laser, and an image forming apparatus incorporating such a semiconductor laser driving device.

  In recent years, it has become indispensable to reduce the power consumption of an image forming apparatus itself such as a laser printer in consideration of the environment, and image forming apparatuses whose power consumption of the entire apparatus is less than 300 W have started to appear. In the future, it is predicted that the power consumption of the entire image forming apparatus will be further reduced.

  Semiconductor laser driving devices incorporated in image forming apparatuses such as laser printers and optical disks and used for writing operations are also desired to reduce their power consumption as the power consumption of image forming apparatuses is reduced. .

  The reduction in power consumption of the semiconductor laser driving device is described in Japanese Patent Laid-Open No. 2000-244052 (see Patent Document 1). Patent Document 1 discloses a semiconductor laser driving device capable of reducing unnecessary power consumption without impairing the high speed required for switching the amount of light emitted from the semiconductor laser. However, in the semiconductor laser driving device disclosed in Patent Document 1, the power consumption during operation is reduced, but the power consumption during standby is not yet reduced.

2. Description of the Related Art Conventionally, a semiconductor laser driving device for an image forming apparatus is in a writing standby state when the image forming apparatus itself is on standby and when the image forming apparatus is operating other than writing. The power consumption during standby of one semiconductor laser driving device is about 0.3 W to 0.4 W. On the other hand, the power consumption of the conventional image forming apparatus is about 1 kW during operation in the case of a laser printer, for example. Accordingly, when only one semiconductor laser is used in the image forming apparatus, only one semiconductor laser driving apparatus is used, and the standby power consumption can be ignored with respect to the power consumption of the image forming apparatus. Since this is a possible value, there is almost no need to reduce the standby power consumption of the semiconductor laser driving device.
JP 2000-244052 A

  However, at present, in order to cope with the increase in the speed of image forming apparatuses, a multi-beam method that realizes a high-speed writing operation by simultaneously using a plurality (2, 4 or 8) semiconductor lasers is becoming mainstream. Accordingly, the same number of semiconductor laser driving devices as the number of semiconductor lasers are required. In addition, a color laser printer has a tandem method in which image forming is performed using four image forming units corresponding to YMCK4 colors. In this method, four semiconductor lasers and four semiconductor laser driving devices are required. Therefore, the standby power consumption of one semiconductor laser driving device was negligible, but in a current image forming apparatus in which speeding up and colorization are progressing, a plurality of semiconductor laser driving devices are used. The standby power consumption of the entire semiconductor laser driving device becomes very large. When eight semiconductor laser driving devices are used, their total standby power consumption may exceed 3 W.

  Accordingly, the standby power consumption of the semiconductor laser driving device cannot easily be ignored as the image forming apparatus increases in speed, color, and power consumption.

  An object of the present invention is to provide a semiconductor laser driving device in which standby power consumption is controlled and an image forming apparatus incorporating such a semiconductor laser driving device.

  In order to achieve the above object, a semiconductor laser driving device of the present invention is a semiconductor laser driving device that controls driving of a semiconductor laser, and includes a reset signal that instructs to reset the semiconductor laser driving device, and the semiconductor laser. And an APC signal instructing to execute automatic light control (APC), and the operation state of the semiconductor laser driving device is changed according to the logic combination of the reset signal and the APC signal. It has an operation mode selection circuit for determining.

  By controlling the operation state in this way, it is possible to provide a semiconductor laser driving device in which standby power consumption is controlled.

  In order to achieve the above object, in the semiconductor laser driving device of the present invention, the operation mode selection circuit has, as one operation mode, a low power consumption mode in which a part of the semiconductor laser driving device is in an operating state. It is characterized by selecting.

  Thereby, it is possible to provide a semiconductor laser driving device with reduced standby power consumption.

  In order to achieve the above object, in the semiconductor laser driving device of the present invention, the operation mode selection circuit selects a sleep mode in which the entire semiconductor laser driving device is inoperative as one of the operation modes. It is characterized by that.

  As a result, it is possible to provide a semiconductor laser driving device that has zero standby power consumption and can easily detect a minute current that flows when the device fails.

  In order to achieve the above object, in the semiconductor laser driving device of the present invention, the operation mode selection circuit shifts from the sleep mode to a low power consumption mode in which a part of the semiconductor laser driving device is in an operating state. It is characterized by doing.

  As a result, it is possible to control standby power consumption step by step, and it is possible to provide a semiconductor laser driving device that does not cause malfunction due to a sharp start-up.

  Furthermore, in order to achieve the above object, an image forming apparatus of the present invention is an image forming apparatus that includes a semiconductor laser driving device that performs drive control of a semiconductor laser and executes image writing by the semiconductor laser driving device. A reset signal instructing the semiconductor laser driving device to reset the semiconductor laser driving device, and an APC signal instructing the semiconductor laser to execute automatic light amount adjustment control (APC), An operation mode selection circuit that determines an operation state of the semiconductor laser driving device in accordance with a combination of logic of the reset signal and the APC signal is provided.

  By controlling the operation state in this way, it is possible to provide an image forming apparatus having a semiconductor laser driving device in which standby power consumption is controlled.

  In order to achieve the above object, in the image forming apparatus of the present invention, the operation mode selection circuit has, as one operation mode, a low power consumption mode in which a part of the semiconductor laser driving device is activated. It is characterized by selecting.

  Accordingly, it is possible to provide an image forming apparatus having a semiconductor laser driving apparatus in which standby power consumption is reduced in accordance with speeding up, colorization, and low power consumption of the image forming apparatus.

  In order to achieve the above object, in the image forming apparatus of the present invention, the operation mode selection circuit selects, as one operation mode, a sleep mode in which the entire semiconductor laser driving device is inactivated. It is characterized by.

  As a result, it is possible to provide an image forming apparatus having a semiconductor laser driving apparatus that consumes zero standby power and that can easily detect a minute current that flows when the apparatus fails.

  In order to achieve the above object, in the image forming apparatus of the present invention, the operation mode selection circuit shifts from the sleep mode to a low power consumption mode in which a part of the semiconductor laser driving device is activated. It is characterized by that.

  As a result, it is possible to control standby power consumption step by step, and it is possible to provide an image forming apparatus having a semiconductor laser driving device that does not cause malfunction due to a sharp start-up.

  According to the present invention, it is possible to provide a semiconductor laser driving device in which standby power consumption is controlled and an image forming apparatus incorporating such a semiconductor laser driving device.

  The best mode for carrying out the present invention will be described with reference to the accompanying drawings.

  FIG. 1 is a block diagram illustrating an example of a configuration of an image forming apparatus.

  In FIG. 1, an image forming apparatus 100 is a laser printer (LP) or a multifunction printer (MFP) or the like, and includes a system control means 101, a storage means 102, an image processing means 103, an image forming means 104, An operation unit 105, a display unit 106, a communication unit 107, a document reading unit 108, and a bus 109 are included. The system control unit 101 is a unit that controls the entire image forming apparatus 100, and includes a central processing unit (CPU), a read-only memory (ROM), a random access memory (RAM), and the like. The storage means 102 is means for accumulating image data, and may be a hard disk device (HDD) or a large-capacity semiconductor storage device. The image processing unit 103 is a unit that executes image processing such as color conversion or gradation processing on the image data. The image forming unit 104 is a unit that forms an image based on image data on a recording medium such as paper or an optical disk using a semiconductor laser. The operation unit 105 is a unit for the user to set and operate the image forming apparatus 100. The display unit 106 is a unit for notifying the user of the state and processing status of the image forming apparatus 100. The communication means 107 is means for transmitting / receiving data to / from an external terminal via a network or the like. The document reading unit 108 is a unit that reads the content of the document placed on the image forming apparatus 100 as image data. A bus 109 is a line for exchanging data and information between each unit of the image forming apparatus 100.

  The image forming apparatus 100 temporarily stores the image data received from the external terminal by the communication unit 107 or the image data read by the document reading unit 108 in the storage unit 102. When the user presets via the operation unit 105 to perform image processing such as color conversion or gradation processing on the image data, the image data stored in the storage unit 102 is stored in the image processing unit. In step 103, predetermined image processing is performed. After the image processing, the image data is written on the recording medium by the image forming unit 104.

  The image forming unit 104 further includes a semiconductor laser driving device for driving and controlling a semiconductor laser that performs a writing operation on the recording medium. The semiconductor laser driving device is in a standby state other than during the writing operation to the recording medium.

  Next, the configuration and standby operation of the semiconductor laser driving device of the present invention will be described in detail in the following examples.

〔Constitution〕
FIG. 2 shows a configuration example of the semiconductor laser driving device of the present invention.

  In FIG. 2, the semiconductor laser driving device 1 is a device that controls the amount of light by adjusting the current flowing through the laser diode 2. The semiconductor laser driving device 1 is connected to the cathode of the laser diode 2 by a terminal 18, and the current-voltage by a terminal 19. The output part of the conversion circuit 4 is connected. The anode of the laser diode 2 is connected to the cathode of the photodiode 3, and is further connected to the power supply voltage VCC. The anode of the photodiode 3 is connected to the input part of the current-voltage conversion circuit 4.

  The laser diode 2 emits light when a current flows. The light emitted from the laser diode 2 is received by the photodiode 3. The photodiode 3 generates a current proportional to the amount of received light. The current-voltage conversion circuit 4 converts the current generated in the photodiode 3 into a voltage. The voltage converted by the current-voltage conversion circuit 4 is input from the terminal 19 to the semiconductor laser driving device 1. The semiconductor laser driving device 1 performs automatic light amount control (APC) based on the input voltage, and adjusts the current flowing through the laser diode 2. Here, APC is a general laser diode control device, and the forward current-light output characteristics (IL characteristics) of the laser diode fluctuate due to ambient temperature change, secular change, etc. It shows the control to keep the constant.

  In order to execute the APC, the semiconductor laser driving device 1 includes a driver circuit 11, an APC execution circuit 12, a reference voltage / current source circuit 13, a control circuit 14, signal input terminals 15 and 16, and an operation mode. And a selection circuit 17. The driver circuit 11 is a circuit for causing a current to flow through the laser diode 2. The APC execution circuit 12 is a circuit that calculates a current necessary for the laser diode 2 to emit light with a predetermined light amount. The reference voltage / current source circuit 13 is a circuit that supplies a reference voltage and a reference current required for the driver circuit 11 and the APC execution circuit 12 to operate. The control circuit 14 is a circuit that digitally controls the driver circuit 11 and the APC execution circuit 12. One signal input terminal 15 of the signal input terminals is a terminal for inputting a RESETB signal for resetting the control circuit 14, and is hereinafter referred to as a RESETB input terminal. The other signal input terminal 16 of the signal input terminals is a terminal for inputting an APC signal for starting APC to the APC execution circuit 12, and is hereinafter referred to as an APC input terminal. When the RESETB signal input from the RESETB input terminal 15 is “0”, it is a reset instruction, and when it is “1”, it is a reset state release instruction. When the APC signal input from the APC input terminal 16 is “1”, it is an instruction to start execution of APC. The reset and APC execution instructions are set by the user via the operation unit 105 in FIG. 1 and are input as signals from the system control 101. The operation mode selection circuit 17 includes a circuit sleep signal SLS_1 for setting each of the driver circuit 11, the APC execution circuit 12, and the reference voltage / current source circuit 13 to a sleep state according to a combination of logic of the RESETB signal and the APC signal. This circuit generates SLS_2.

  The operation mode selection circuit 17 is configured according to the operation specifications of the semiconductor laser driving device 1. In the present embodiment, as shown in FIG. 2, the operation mode selection circuit 17 includes first and second OR circuits 171 and 173 and a NOR circuit 172. The first and second OR circuits 171 and 173 and the NOR circuit 172 are two-input one-output circuits. One input terminal of each of the first OR circuit 171 and the NOR circuit 172 is connected to the RESETB input terminal 15, and the other is connected to the APC input terminal 16. The output terminal of the first OR circuit 171 is connected to the driver circuit 11, the APC execution circuit 12, and the control circuit 14. The output signal of the first OR circuit 171 is input as the first circuit sleep signal SLS_1 to the driver circuit 11 and the APC execution circuit 12, and is input to the control circuit 14 as a reset signal. Further, the output terminal of the first OR circuit 171 is connected to one input terminal of the second OR circuit 173. The output terminal of the NOR circuit 172 is connected to the other input terminal of the second OR circuit 173. The output terminal of the second OR circuit 173 is connected to the reference voltage / current source circuit 13. The output signal of the second OR circuit 173 is input to the reference voltage / current source circuit 13 as the second circuit sleep signal SLS_2. When the circuit sleep signals SLS_1 and SLS_2 are “0”, the circuit is put into a sleep state, and when the circuit sleep signals SLS_1 and “SLS_2” are “1”, the sleep state is released. In this embodiment, the APC signal is directly input to the APC execution circuit 12 from the APC input terminal 16.

[Operation]
FIG. 3 is a table showing the relationship between the input signal of the semiconductor laser driving device 1 of FIG. 2 and the standby operating state. With reference to FIG. 3, operation control during standby of the semiconductor laser driving device 1 of FIG. 2 by two input signals, that is, a RESETB signal and an APC signal will be described.

  When both the RESETB signal and the APC signal are “0”, the first and second circuit sleep signals SLS_1 and SLS_2 output from the operation mode selection circuit 17 are “0” and “1”, respectively. . Accordingly, the driver circuit 11 and the APC execution circuit 12 are in the sleep state, and the reference voltage / current source circuit 13 is in the operating state. Further, since the first circuit sleep signal SLS_1 is also supplied to the control circuit 14 as a reset signal, the control circuit 14 is in a reset state. The state of the semiconductor laser driving device 1 in which only the reference voltage / current source circuit 13 is operating is called a low power consumption mode.

  When the APC signal remains “0” and the RESETB signal is “1”, the first and second circuit sleep signals SLS_1 and SLS_2 output from the operation mode selection circuit 17 are both “1”. It becomes. Accordingly, not only the reference voltage / current source circuit 13 but also the driver circuit 11 and the APC execution circuit 12 are activated. Further, since the first circuit sleep signal SLS_1 is also supplied to the control circuit 14 as a reset signal, the reset state of the control circuit 14 is released, and the semiconductor laser driving device 1 causes the driver circuit 11 to supply current to the laser diode 2. It shifts to the normal mode which drives to flow. However, since the APC signal is still “0”, the APC execution circuit 12 does not execute APC.

  On the other hand, when the RESETB signal remains “0” and the APC signal is “1”, the first and second circuit sleep signals SLS_1 and SLS_2 output from the operation mode selection circuit 17 are both “ 1 ". Accordingly, not only the reference voltage / current source circuit 13 but also the driver circuit 11 and the APC execution circuit 12 are activated. Further, since the first circuit sleep signal SLS_1 is also supplied to the control circuit 14 as a reset signal, the reset state of the control circuit 14 is released, and the semiconductor laser driving device 1 causes the driver circuit 11 to supply current to the laser diode 2. It shifts to the normal mode which drives to flow. Further, since the APC signal is “1”, the APC execution circuit 12 executes APC. In this case, since the RESETB signal for instructing resetting of the semiconductor laser driving device 1 is “0”, the control circuit 14 is supposed to be in a reset state and the semiconductor laser driving device 1 should not operate. In the embodiment, an operation mode is given so that an instruction to start execution of APC is given priority, and the reset state of the control circuit 14 is canceled when the APC signal is “1” even if the RESETB signal is “0”. A selection circuit 17 is configured.

  Finally, when both the RESETB signal and the APC signal are “1”, the first and second circuit sleep signals SLS_1 and SLS_2 output from the operation mode selection circuit 17 are both “1”. . Accordingly, the driver circuit 11, the APC execution circuit 12, and the reference voltage / current source circuit 13 are in an operating state. Further, since the first circuit sleep signal SLS_1 is also supplied to the control circuit 14 as a reset signal, the reset state of the control circuit 14 is released, and the semiconductor laser driving device 1 causes the driver circuit 11 to supply current to the laser diode 2. It shifts to the normal mode which drives to flow. Further, since the APC signal is “1”, the APC execution circuit 12 executes APC.

  As described above, the semiconductor laser driving device 1 is switched from the low power consumption mode during standby to the normal mode during normal operation by input signals from outside the semiconductor laser driving device such as a RESETB signal and an APC signal. Can do.

  Further embodiments of the present invention are described below with reference to FIGS.

〔Constitution〕
FIG. 4 shows another configuration example of the operation mode selection circuit incorporated in the semiconductor laser driving device 1 of FIG. 4, an operation mode selection circuit 47 is incorporated in the semiconductor laser driving device 1 of FIG. 2 in place of the operation mode selection circuit 17, and has a D flip-flop circuit 471 and a 2-input 1-output OR circuit 472. In the D flip-flop circuit 471, the D terminal is connected to a DC voltage power source (not shown), the clock (CLK) terminal is connected to the APC input terminal 16, and the reset (RB) terminal is connected to the RESETB input terminal 15. . Further, the output terminal Q of the D flip-flop circuit 471 is connected to the driver circuit 11 and the APC execution circuit 12. The output signal of the D flip-flop circuit 471 is input to the driver circuit 11 and the APC execution circuit 12 as the first circuit sleep signal SLS_1. One input terminal of the OR circuit 472 is connected to the reset terminal of the D flip-flop circuit 471 and the control circuit 14, and the other is connected to the APC input terminal 16. The output terminal of the OR circuit 472 is connected to the reference voltage / current source circuit 13. The output signal of the OR circuit 472 is input to the reference voltage / current source circuit 13 as the second circuit sleep signal SLS_2. In this embodiment, the APC signal is directly input to the APC execution circuit 12 from the APC input terminal 16 as in the first embodiment. However, the RESETB signal is directly input from the RESETB input terminal 15 to the control circuit. 14 is different from that of the first embodiment.

[Operation]
FIG. 5 is a table showing the relationship between the input signal of the semiconductor laser driving apparatus incorporating the operation mode selection circuit 47 of FIG. 4 and the standby operation state. With reference to FIG. 5, the operation control during standby of the semiconductor laser driving apparatus incorporating the operation mode selection circuit 47 of FIG. 4 by two input signals, that is, the RESETB signal and the APC signal will be described.

  When both the RESETB signal and the APC signal are “0”, the first and second circuit sleep signals SLS_1 and SLS_2 output from the operation mode selection circuit 47 are both “0”. Therefore, the driver circuit 11, the APC execution circuit 12, and the reference voltage / current source circuit 13 are in a sleep state. At this time, the power consumption of the semiconductor laser driving device 1 is zero. The state of the semiconductor laser driving device 1 in which all the internal circuits are not operating is called a sleep mode.

  Next, when the APC signal remains “0” and the RESETB signal becomes “1”, the reset of the control circuit 14 is released and the second circuit sleep signal SLS_2 becomes “1”, and the reference voltage / The current source circuit 13 is activated. However, since the first circuit sleep signal SLS_1 remains “0”, the driver circuit 11 and the APC execution circuit 12 are still in the sleep state. Accordingly, since only the reference voltage / current source circuit 13 is operating in the semiconductor laser driving device 1, the semiconductor laser driving device 1 is in the low power consumption mode at this time.

  When the APC signal becomes “1” after the RESETB signal becomes “1”, the first circuit sleep signal SLS_1 also becomes “1”, and not only the reference voltage / current source circuit 13 but also the driver circuit 11 and the APC are executed. Circuit 12 is also activated. Therefore, since all the circuits are operating in the semiconductor laser driving device 1, the semiconductor laser driving device 1 is in the normal mode at this time. Further, since the APC signal is “1”, the APC execution circuit 12 executes APC. Thereafter, the semiconductor laser driving device 1 remains in the normal mode even if the APC signal becomes “0” unless receiving the RESETB signal instructing resetting of the device (that is, “0”).

  Providing a sleep mode in this way is advantageous for fault detection. A semiconductor laser driving device is often manufactured as a semiconductor integrated circuit (semiconductor IC). In this case, when an internal failure occurs in the semiconductor IC, a path from the power source to the ground is generated, and a through current may flow. . Since the through current is very small, it is difficult to measure in the normal mode, and a failure cannot be easily detected. However, in the sleep mode, the power consumption of the semiconductor laser driving device is zero, that is, the current consumption is zero, and a minute through current can be easily measured, so that failure detection is facilitated.

  However, since all the circuits in the semiconductor laser driving device have stopped operating in the sleep mode, when the state directly shifts to the normal mode from such a state, each analog operation in the semiconductor laser driving device operates. There is a possibility that the rise time of the circuit to be generated is shifted and the semiconductor laser driving device malfunctions. Therefore, in order to start up in advance only those circuits that can cause a malfunction when shifting from the sleep state to the operating state among the individual analog operating circuits in the semiconductor laser driving device, The operating state is not directly shifted from the sleep mode to the normal mode, but through the low power consumption mode. For example, when shifting from the sleep mode to the normal mode without going through the low power consumption mode, all the circuits of the semiconductor laser driving device 1 including the reference voltage / current source circuit 13 are started up at the same time. In many cases, the reference voltage / current source circuit has a longer period of time from startup to stabilization than other analog circuits. During this period, the voltage and current output from the reference voltage / current source circuit 13 are unstable. For this reason, the entire semiconductor laser driving device 1 may malfunction. Therefore, in order to prevent malfunction of the semiconductor laser driving device 1, it is necessary to start up only the reference voltage / current source circuit 13 first and provide a period until the operation is stabilized. Further, by providing the low power consumption mode, it is possible to reduce the power consumption in a standby state until the writing operation by the semiconductor laser driving device 1 starts.

  As described above, the semiconductor laser driving device 1 can switch the operation state during standby step by step by the input signals from the outside of the semiconductor laser driving device such as the RESETB signal and the APC signal. That is, it becomes possible to control the power consumption of the semiconductor laser driving device in stages.

Even in a multi-channel semiconductor laser driving device capable of controlling a plurality of semiconductor lasers with a single semiconductor laser driving device, the transition to the low power consumption mode and the introduction of the sleep mode described above are effective. FIG. 6 shows a configuration example of the multi-channel semiconductor laser driving device of the present invention. In FIG. 6, the multi-channel semiconductor laser driving device 61 is connected to the cathodes of the _n laser diodes 62 _{1 to} 62 _n by n terminals 618 _{1 to} 618 _n , and the n terminals 619 ₁ to 619 ₁ Each of 619 _n is connected to an output unit of each of the _n current-voltage conversion circuits 64 ₁ to 64 _n . The anodes of the laser diodes 62 _{1 to} 62 _n are connected to the cathodes of the corresponding photodiodes 63 _{1 to} 63 _n , respectively, and further connected to the power supply voltage VCC. The anodes of the photodiodes 63 _{1 to} 63 _n are connected to the input portions of the corresponding current-voltage conversion circuits 64 ₁ to 64 _n , respectively.

The semiconductor laser driving device 61 includes a driver circuit 611, an APC execution circuit 612, a reference voltage / current source circuit 613, a control circuit 614, a RESETB input terminal 615, and n APC input terminals that are the same number as the laser diodes. 616 _{1 to} 616 _n and an operation mode selection circuit 617. The function of each circuit in the semiconductor laser driving device 61 is the same as that of each circuit in the single channel semiconductor laser driving device 1 shown in FIG. However, in order to drive one semiconductor laser provided for each channel, an APC signal equivalent to the number of channels instructing to execute APC for each channel is input to the multichannel semiconductor laser driving device. The

  FIG. 7 shows an example of the relationship between the input signal of the multi-channel semiconductor laser driving device and the standby operating state. When the relationship as shown in FIG. 7 is established, the semiconductor laser drive device is in the case where the RESETB signal and all the APC signals are “0”, that is, in the reset state and does not execute APC for all the channels. Is in a low power consumption mode, and in other logics it is in a normal mode. As shown in FIGS. 2 and 4, the semiconductor laser driving apparatus can obtain desired operation control by configuring an operation mode selection circuit in accordance with an input signal. When the relationship between the input signal and the standby operating state in the multi-channel semiconductor laser driving device is as shown in FIG. 7, the operation mode selection circuit in the semiconductor laser driving device is configured as shown in FIG. 8, for example. .

In FIG. 8, the operation mode selection circuit 617 includes an OR circuit group 81 including first and second OR circuits 80 and 83 having n inputs and one output, and n OR circuits 81 _{1 to} 81 _{n having} two inputs and one output. A NOR circuit 82 with two inputs and one output, and a third OR circuit 84 with (n + 1) inputs and one output. The n input terminals of the first OR circuit 80 are connected to the APC input terminals 616 _{1 to} 616 _n , respectively, while the output terminal is connected to one input terminal of the NOR circuit 82. . The other input terminal of the NOR circuit 82 is connected to the RESETB input terminal 615, and its output terminal is connected to one of the input terminals of the third OR circuit 84. _One of the input terminals of the OR circuits 81 _{1 to} 81 _n of the OR circuit group 81 is connected to the RESETB input terminal 615 and the other is connected to each of the APC input terminals 616 _{1 to} 616 _n . The output terminals are connected to the input terminals of the second and third OR circuits 83 and 84, respectively. The output terminal of the second OR circuit 83 is connected to the driver circuit 611, the APC execution circuit 612, and the control circuit 614. The output signal of the second OR circuit 83 is input to the driver circuit 611 and the APC execution circuit 612 as the first circuit sleep signal SLS_1, and is input to the control circuit 614 as a reset signal. The output terminal of the third OR circuit 84 is connected to the reference voltage / current source circuit 613. The output signal of the third OR circuit 84 is input to the reference voltage / current source circuit 613 as the second circuit sleep signal SLS_2. In this embodiment, n APC signals are directly input to the APC execution circuit 612 from the _n APC input terminals 616 ₁ to 616 _n .

  As described above, even in a multi-channel semiconductor laser driving device capable of controlling a plurality of semiconductor lasers with a single semiconductor laser driving device, the operating state during standby can be easily switched by an input signal from the outside of the semiconductor laser driving device. Can do.

[Modification]
The present invention is not limited to the embodiments described above.

  For example, the semiconductor laser driving device of the present invention may be used in any device that uses a semiconductor laser other than the image forming apparatus. Further, the semiconductor laser driving device of the present invention may be a stand-alone device, in which case an input signal is directly input from the outside.

  Furthermore, the operation mode selection circuit incorporated in the semiconductor laser driving device of the present invention can take various configurations in addition to the above-described embodiments, depending on the required standby operation.

An example of the configuration of the image forming apparatus is represented as a block diagram. 1 shows a configuration example of a semiconductor laser driving device of the present invention. 3 is a table showing a relationship between an input signal and an operation state of the semiconductor laser driving device of FIG. 3 shows another configuration example of an operation mode selection circuit incorporated in the semiconductor laser driving device of FIG. 5 is a table showing a relationship between an input signal and an operation state of a semiconductor laser driving device in which the operation mode selection circuit of FIG. 4 is incorporated. 1 shows a configuration example of a multi-channel semiconductor laser driving device of the present invention. 7 is a table showing an example of a relationship between an input signal and an operation state of the multi-channel semiconductor laser driving device of FIG. 7 shows a configuration example of an operation mode selection circuit incorporated in the multi-channel semiconductor laser driving device of FIG.

Explanation of symbols

₁ , 61 Semiconductor laser driving device ₂ , 62 ₁ , 62 _n Laser diode 3, 63 ₁ , 63 _n Photo diode 4, 64 ₁ , 64 _n Current-voltage conversion circuit 11, 611 Driver circuit 12, 612 APC execution circuit 13, 613 Reference voltage / current source circuit 14, 614 Control circuit 15, 615 ₁ , 615 _n RESETB input terminal 16, 616 ₁ , 616 _n APC input terminal 17, 47, 617 Operation mode selection circuit 171, 173, 472, 80, 81 ₁ , 81 _n , 83, 84 OR circuit 172, 82 NOR circuit 471 D flip-flop circuit

Claims (6)

In a semiconductor laser driving device for controlling the driving of a semiconductor laser,
An APC execution circuit for calculating a current required for the semiconductor laser to emit a predetermined light amount for automatic light amount control (APC) of the semiconductor laser;
A driver circuit for driving the semiconductor laser in accordance with a calculation result of the APC execution circuit;
A reference voltage / current source circuit for supplying power to the APC execution circuit and the driver circuit;
A reset signal for instructing to reset the semiconductor laser drive device, the semiconductor and APC signal for instructing to perform the APC for the laser is input, depending on the logical combination of the reset signal and the APC signal the APC execution circuit, possess the operation mode selection circuit for switching each of the operating / non-operation of the driver circuit and the reference voltage / current source circuit,
The operation mode selection circuit selects the semiconductor laser drive device when the reset signal instructs the reset of the semiconductor laser drive device and the APC signal does not instruct the start of execution of the APC. A low power consumption mode in which the circuit and the driver circuit are deactivated and the reference voltage / current source circuit is activated, or the APC circuit, the driver circuit, and the reference voltage / current source circuit are deactivated. A semiconductor laser driving device characterized in that a sleep mode is entered . The operation mode selection circuit, when the semiconductor laser drive device is in the sleep mode, when the reset signal indicates the cancellation of the reset, and the operation state of said reference voltage / current source circuit, the semiconductor laser driving characterized in that makes migrating device in the low power consumption mode, the semiconductor laser driving apparatus according to claim 1. The semiconductor laser driving device is a multi-channel semiconductor laser driving device capable of controlling a plurality of semiconductor lasers,
The operation mode selection circuit receives a plurality of APC signals corresponding to each of the plurality of semiconductor lasers, and when all of the plurality of APC signals do not instruct the start of execution of the APC, the semiconductor laser drive Put the device into the low power consumption mode
The semiconductor device according to claim 1. In an image forming apparatus having a semiconductor laser driving device that performs drive control of a semiconductor laser, and performing image writing by the semiconductor laser driving device,
The semiconductor laser driving device comprises:
An APC execution circuit for calculating a current required for the semiconductor laser to emit a predetermined light amount for automatic light amount control (APC) of the semiconductor laser;
A driver circuit for driving the semiconductor laser in accordance with a calculation result of the APC execution circuit;
A reference voltage / current source circuit for supplying power to the APC execution circuit and the driver circuit;
A reset signal for instructing to reset the semiconductor laser drive device, the semiconductor and APC signal for instructing to perform the APC for the laser is input, depending on the logical combination of the reset signal and the APC signal the APC execution circuit, possess the operation mode selection circuit for switching each of the operating / non-operation of the driver circuit and the reference voltage / current source circuit,
The operation mode selection circuit selects the semiconductor laser driving device when the reset signal instructs the resetting of the semiconductor laser driving device and the APC signal does not instruct the start of execution of the APC. A low power consumption mode in which the circuit and the driver circuit are deactivated and the reference voltage / current source circuit is activated, or the APC circuit, the driver circuit, and the reference voltage / current source circuit are deactivated. An image forming apparatus characterized in that a sleep mode is entered . The operation mode selection circuit, when said semiconductor laser drive device is in the sleep mode, when the reset signal indicates the cancellation of the reset, and the operation state of said reference voltage / current source circuit, the semiconductor laser drive The image forming apparatus according to claim 4 , wherein the apparatus is shifted to the low power consumption mode. The semiconductor laser driving device is a multi-channel semiconductor laser driving device capable of controlling a plurality of semiconductor lasers,
The operation mode selection circuit receives a plurality of APC signals corresponding to each of the plurality of semiconductor lasers, and when all of the plurality of APC signals do not instruct the start of execution of the APC, the semiconductor laser drive Put the device into the low power consumption mode
The image forming apparatus according to claim 4.

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