JP2008109051A - Light emitting element driving apparatus and electronic equipment provided with it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light emitting element driving apparatus capable of selecting an optimum driving method for each light emitting element. <P>SOLUTION: The light emitting element driving apparatus is provided with a register part 1 for outputting the instruction of DC drive or pulse drive to a drive control part 2 by an operation instruction inputted from the outside. The drive control part 2 outputs a DC voltage to a drive part 5 by the instruction from the register part 1 in the case of DC-driving the light emitting element 6, and outputs a voltage to be turned on or off at a timing generated in a timer part 4 to the drive part 5 by the instruction from the register part 1 in the case of pulse-driving the light emitting element 6. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a light emitting element driving apparatus that drives a light emitting element such as a light emitting diode (LED). In particular, the present invention relates to a light emitting element driving device including a register for realizing selection of an LED driving method (DC driving method, pulse driving method) and duty ratio selection. The present invention also relates to an electronic device including such a light emitting element driving device.

  Image reproduction apparatuses typified by televisions and DVD players, and image (still image, moving image) recording apparatuses typified by video cameras and digital cameras are widely used. A light emitting element such as an LED incorporated in these devices is a very important element in terms of a user interface. This is because the light-emitting element can be driven to illuminate in a variety of ways, such as lighting a specific color, stopping the lighting driving, and always lighting driving and blinking driving. This is because the user interface can be handled by various methods.

  For example, a recent video camera is equipped with a light emitting element that is turned on when the power of the device body is turned on, a light emitting element that is turned on when an information medium such as a memory card is being accessed, and the like. Yes. Also, there is a lighting method that changes the lighting color according to the state of the device body, such as lighting the light emitting element in red when the power is on, and lighting the light emitting element in green in the standby state.

  Usually, the microcomputer directly drives the light emitting element. However, in recent years, all products have become multifunctional, and the functions that the microcomputer has to control have increased significantly accordingly. Therefore, there is a problem that the microcomputer port tends to be insufficient. Therefore, it is possible to construct a more effective system by preparing a dedicated light-emitting element driving device or a larger-scale LSI incorporating the light-emitting element instead of the microcomputer directly driving the light-emitting element.

In addition, as a driving method of the light emitting element, a direct current driving method in which a constant current is continuously applied to the light emitting element and continuously lit, and a current is intermittently applied to the light emitting element based on a predetermined pulse to continuously light up. There is a pulse driving method. Generally, lighting driving is performed by any one of a DC driving method and a pulse driving method, and the pulse driving method has an advantage that less power consumption is required. Patent Document 1 discloses a configuration in which a light emitting element is turned on by a pulse driving method.
JP 2004-241264 A

  However, in the configuration disclosed in Patent Document 1, since the light emitting element is driven to be lit by a pulse driving method based on a certain pulse, a driving method with better visibility cannot be selected for each light emitting element. There is a problem. That is, the light emitting elements have individual variations for each element, and even when the same current is applied, the brightness may be different for each element. For example, in the case where a plurality of light emitting elements that emit light of the same color are mounted in a single device, if there is a solid variation for each light emitting device and the brightness during light emission varies, the quality of the device is degraded.

  In view of the above problems, an object of the present invention is to provide a light emitting element driving apparatus capable of selecting an optimum driving method for each light emitting element. It is another object of the present invention to provide an electronic device that can suppress variation in light emission during light emission and improve quality.

  In order to achieve the above object, a light-emitting element driving device of the present invention includes a light-emitting element, a drive unit that drives the light-emitting element to be turned on or off according to an input voltage, an oscillation unit that generates a reference pulse, A timer unit that generates a pulse of a predetermined frequency based on a reference pulse output from the oscillating unit; and a drive control unit that outputs a voltage to the driving unit to control operation, and at least DC driving and pulse driving A light emitting element driving apparatus that drives and controls the light emitting element by any one of the driving methods, and outputs the DC driving or the pulse driving command to the driving control unit according to an operation command input from the outside. The drive control unit outputs a DC voltage to the drive unit in accordance with a command from the register unit when the light emitting element is DC driven. When pulsing the light emitting element, by a command from the register unit, and outputs a voltage that turns on or off at a timing generated by the timer unit to the drive unit.

  In addition, the electronic device of the present invention outputs a light emitting element, a driving unit that drives the light emitting element to be turned on or off according to an input voltage, an oscillating unit that generates a reference pulse, and an output from the oscillating unit A timer unit that generates a pulse of a predetermined frequency based on a reference pulse, and a drive control unit that outputs a voltage to the drive unit to control operation, and at least one of DC drive and pulse drive A light emitting element driving apparatus for driving and controlling the light emitting element by a method, comprising: a register unit that outputs the DC driving or the pulse driving command to the driving control unit according to an operation command input from the outside; When the light emitting element is DC driven, the drive control unit outputs a DC voltage to the driving part in response to a command from the register unit, and the light emitting element is pulse driven. That case, the command from the register unit, are those in which a light-emitting element driving device for outputting a voltage that turns on or off at a timing generated by the timer unit to the drive unit.

  The light emitting element driving apparatus of the present invention can select an optimum driving method for each light emitting element. Therefore, there are various effects such as light emission variation for each light emitting element, visibility can be improved, and power consumption can be suppressed.

  Moreover, since the electronic device of this invention can suppress the light emission variation of a light emitting element, it can improve a dignity.

  In the light emitting element driving device of the present invention, the register unit may be configured to store information relating to the driving method in a table. As a result, an instruction is performed by transmitting only a value from the outside to the register unit, and a drive command corresponding to the value input in the register unit is output, so the amount of data between the outside and the register unit is reduced. The number can be reduced, and high-speed response can be achieved.

  The drive control unit may be configured to change the duty ratio of the voltage in accordance with a command from the register unit during pulse driving. Thereby, the light emission amount of the light emitting element at the time of pulse drive can be controlled.

  The electronic apparatus according to the present invention further includes a clock control unit that is controlled by moving a needle in synchronization with a reference pulse generated by the oscillator, and the timer unit has a predetermined frequency based on the reference pulse generated by the oscillator. The pulse can be generated. As a result, the light emitting element driving device and the timepiece control unit can share the oscillation unit, so that the cost can be reduced and the electronic device can be downsized.

(Embodiment 1)
FIG. 1 is a block diagram showing a light emitting element driving apparatus according to Embodiment 1. In FIG. FIG. 2 shows a driving pulse representing a DC driving method of the light emitting element in the first embodiment. FIG. 3 shows driving pulses representing the pulse driving method of the light emitting element in the first embodiment.

  In FIG. 1, the light emitting element driving device 8 includes a register unit 1, a drive control unit 2, an oscillation unit 3, a timer unit 4, and a light emitting element driving unit 5. In the present embodiment, the light emitting element driving device 8 is configured by a chip independent from a microcomputer (external control unit 9) and other ICs.

  The register unit 1 stores information such as various light emitting element control methods such as a direct current drive method and a pulse drive method, and a duty ratio during pulse drive in a table form. Each data constituting the table is associated with a value. Therefore, the register unit 1 extracts data corresponding to the value from the table based on the value input from the external control unit 9, and outputs a drive command corresponding to the extracted data to the drive control unit 2. For example, in the register unit 1, it is assumed that the data “pulse driving the light emitting element with a duty ratio of 70%” is associated with the value “1”. When the value “1” is input from the external control unit 9, the register unit 1 outputs a command to drive the light emitting element with a duty ratio of 70% to the drive control unit 2.

  The drive control unit 2 outputs a timing signal of the light emitting element to the light emitting element driving unit 5 based on the drive command output from the register unit 1. When the first light emitting element 6 and the second light emitting element 7 are DC driven, a timing signal as shown in FIG. 2 is generated and output. When the first light emitting element 6 and the second light emitting element 7 are pulse-driven, a timing signal as shown in FIG. 3 is generated and output based on time information sent from the timer unit 4. . The timing signal output from the drive control unit 2 corresponds to a voltage applied to the base of the transistor when the light emitting element driving unit 5 is configured by a drive circuit including a transistor, for example.

  The oscillation unit 3 generates and outputs a reference pulse when the first light emitting element 6 and the second light emitting element 7 are pulse-driven. In this embodiment, the oscillating unit 3 includes an oscillator that generates a reference pulse of about 32 KHz (more precisely, 32.768 kHz) used for hand movement control in a separately provided timepiece driving IC. That is, the oscillating unit 3 is not a dedicated unit for driving the light emitting element to be lit, and an existing oscillator is used in the device, so that the cost is not increased. In particular, in this embodiment, since the oscillator of the clock driving IC that is always supplied with power is used even when the power of the device is turned off, the power switch of the device is turned on. Immediately after being operated, the light emitting element can be driven and controlled by pulse driving. In addition, when the oscillation unit 3 has an oscillation device outside, it is called an external oscillation unit, and when it has an oscillation device inside, it is called an internal oscillation unit. The oscillation unit 3 is not particularly limited in type and deviation, such as a crystal oscillator, a crystal oscillator, or a ceramic oscillator.

  The timer unit 4 generates an actual time for driving or non-driving the first light emitting element 6 and the second light emitting element 7 based on the reference pulse output from the oscillating unit 3. Specifically, a pulse of a predetermined frequency (256 KHz in the present embodiment) is generated by dividing or edge-detecting the 32 KHz reference pulse output from the oscillation unit 3. The pulse generated in the timer unit 4 is not particularly limited in the duty ratio itself, but it is almost always off when it is close to 0%, and it is almost always on when it is close to 100%, so the effect is considered to be small. It is done.

  The light emitting element driving unit 5 receives the timing signal output from the drive control unit 2 and drives the first light emitting element 6 and the second light emitting element 7 to be lit according to the timing signal. Specifically, the light emitting element driving unit 5 is configured by a drive circuit that drives the first light emitting element 6 and the second light emitting element 7 to light. The drive circuit includes a transistor for switching on and off, and is configured such that the timing signal (voltage) from the drive control unit 2 is applied to the base of the transistor, and the collector emits the first light emission via the load resistor. This is a circuit in which the element 6 or the second light emitting element 7 is connected and the emitter is grounded. In such a drive circuit, by turning on or off the base of the transistor based on a timing signal (voltage), the current flowing through the light emitting element can be switched on or off, and the light emitting element is turned on or off. Can be driven. Note that the light emitting element driving unit 5 is not limited to a transistor drive circuit, and may be any circuit that can turn on or off the light emitting element based on at least the timing signal generated by the drive control unit 2.

  The 1st light emitting element 6 and the 2nd light emitting element 7 are comprised, for example by LED, and are driven by the light emitting element drive part 5 so that it may be lighted or extinguished. Note that in this embodiment, two light emitting elements are connected, but one may be used, and drive control can be performed even with three or more. In the following description of the operation, an operation of driving and lighting the first light emitting element 6 will be described. In the present embodiment, the first light emitting element 6 and the second light emitting element 7 can be independently driven and controlled, and can also be simultaneously controlled. The first light-emitting element 6 and the second light-emitting element 7 are not limited to LEDs, and may be any light-emitting element that can be turned on or off at least by a timing signal (voltage) output from the drive control unit 2. .

  The external control unit 9 controls the register unit 1 from the outside. Specifically, the external control unit 9 outputs a light emission command of the light emitting element and a command related to the light emission method to the register unit 1 as values. Moreover, the external control part 9 can be comprised with a microcomputer, and the port shortage of a microcomputer can be eliminated by comprising a microcomputer and the light emitting element drive device 8 with another chip | tip in this way.

  The operation will be described below.

  Usually, the microcomputer directly drives the light emitting element. However, in recent years, as described above, all products have become multifunctional, and the functions that the microcomputer has to control have increased significantly. Accordingly, there has been a problem that the ports of the microcomputer are likely to be insufficient. In the present embodiment, a microcomputer (for example, the external control unit 9 in FIG. 1) does not directly drive the first light emitting element 6, but a light emitting element driving device that drives and controls the first light emitting element 6. It is realized by incorporating it into an independent dedicated IC.

  In FIG. 1, the external control unit 9 can select a driving method for a target light emitting element in accordance with its visibility, power consumption, and characteristics. Specifically, by inputting a value into the register unit 1, a desired driving method is selected from the data tabulated in the register unit 1. The data tabulated in the register unit 1 includes information on a light emitting element driving method such as a direct current driving method and a pulse driving method, and information on a duty ratio during pulse driving. For example, a direct current driving method may be selected to increase the visibility of the light emitting element, and a pulse driving method may be selected to reduce power consumption. Also, if there is individual variation among light emitting elements, select a direct current drive method for light emitting elements with a small amount of light emission to increase the light emission amount, or use a pulse driving method for light emitting elements with a large amount of light emission. By selecting and reducing the light emission amount, the brightness of the light emitting elements can be made uniform. In addition, since the duty ratio in the pulse driving method can be selected, the brightness of the light emitting element during pulse driving can be finely adjusted. The communication between the light emitting element driving device 8 and the external control unit 9 includes two-wire serial communication represented by I2C (Inter-Integrated Circuit), three-wire serial communication represented by SPI (Serial Perirheral Interface), and the like. Can be mentioned.

  First, the operation when the pulse driving method is selected will be described.

  When a command to turn on the first light emitting element 6 is input from the external control unit 9, the register unit 1 outputs a drive command based on a value input from the external control unit 9. For example, when a value for lighting the first light emitting element 6 by pulse driving is input from the external control unit 9, the register unit 1 picks up a driving method (pulse driving) corresponding to the value from its own table. Then, a command for driving by the pulse driving method is output to the drive control unit 2.

  The drive control unit 2 generates a predetermined timing signal based on the drive command from the register unit 1. Note that a pulse having a predetermined frequency generated by the timer unit 4 based on the reference pulse oscillated by the oscillation unit 3 is input to the drive control unit 2. The drive control unit 2 generates a timing signal (voltage) shown in FIG. 3 based on a pulse having a predetermined frequency input from the timer unit 4.

  The drive control unit 2 drives and controls the light emitting element driving unit 5 based on the generated timing signal. Specifically, the drive control unit 2 performs drive control so that the base voltage of the transistor of the drive circuit in the light emitting element drive unit 5 is turned on or off in accordance with the timing of the timing signal shown in FIG. Accordingly, the current flowing through the first light emitting element 6 can be switched on or off, and the first light emitting element 6 can be controlled to be turned on or off.

  Next, the operation when the DC driving method is selected will be described.

  When the first light emitting element 6 is DC driven, the register unit 1 outputs a DC drive command to the drive control unit 2 based on a value input from the external control unit 9 (a value corresponding to DC drive). . The drive control unit 2 generates a timing signal as shown in FIG. 2 based on a command from the register unit 1. In the case of direct current driving, pulse frequency control as in pulse driving is unnecessary, and time information output from the timer unit 4 is ignored.

  The drive control unit 2 drives and controls the light emitting element driving unit 5 based on the generated timing signal. Specifically, the drive control unit 2 performs drive control so that the base voltage of the transistor of the drive circuit in the light emitting element drive unit 5 is turned on or off in accordance with the timing of the timing signal shown in FIG.

  Thus, the first light emitting element 6 is controlled so that the applied current is turned on at a timing synchronized with the timing signal shown in FIG. 2 by the driving control by the light emitting element driving unit 5 and is controlled to be lit. .

  When the first light emitting element 6 is continuously turned on for a predetermined time by the direct current driving method, it can be continuously turned on by continuously inputting a value from the external control unit 9 to the register unit 1. The lighting time corresponds to the time during which values are continuously input. For example, when the first light emitting element 6 is lit for 5 seconds, the external control unit 9 continuously inputs a value to the register unit 1 for 5 seconds.

  As described above, according to the present embodiment, it is possible to select a driving method according to a light emitting element by making it possible to select either a direct current driving method or a pulse driving method. For example, if it is desired to improve the visibility of the light emitting element, a control signal (value) may be input to the register unit 1 so as to select a DC driving method. If it is desired to reduce power consumption, a pulse driving method is selected. Thus, a control signal (value) may be input to the register unit 1. Further, in the case where individual variations occur in each light emitting element, any one of a direct current driving method and a pulse driving method may be selected in order to suppress the individual variation.

  Further, the light emitting element driving device 8 is configured independently of the microcomputer (external control unit 9), and is controlled from the outside by the external control unit 9, so that the shortage of ports of the microcomputer can be solved.

  In the present embodiment, the oscillator associated with the timepiece IC (also referred to as a real-time clock IC or the like) is used as the oscillation unit 3, but the present invention is not limited to this. A similar configuration can be realized as long as the oscillator can output at least a constant pulse. The frequency of the pulses output from the oscillator 3 and the timer 4 is an example.

  In the present embodiment, the light emitting element driving device 8 is configured as an IC independent of a microcomputer or another IC. However, the light emitting element driving device 8 may be configured to be incorporated in another IC in a device body such as a video camera. For example, a configuration in which a clock IC mounted on a video camera controls a clock function can be considered.

  FIG. 4 shows a configuration in which the light emitting element driving device 8 is incorporated into an existing timepiece control LSI. In FIG. 4, the LSI 10 includes a clock control unit 11 that is a circuit for controlling a clock function mounted on the video camera, and a light emitting element driving device 8. The light emitting element driving device 8 has the same configuration as that in the first embodiment, but the oscillation unit 3 is used for the hand movement control in the timepiece control unit 11 and the pulse control at the time of pulse driving in the light emitting element driving device 8. The control unit 11 and the timer unit 4 are connected. That is, the LSI 10 has the functions equivalent to those realized by the light emitting element driving device 8 and also has other functions.

  Note that the IC incorporating the light emitting element driving device is described as an example in which a watch IC is applied. For example, even an IC provided independently of the main device is an IC that is activated when the power of the electronic device is off. Any IC may be applied. That is, for example, there are an IC in which a circuit for accepting an operation of a power switch is incorporated, and an IC in which a circuit for resetting an LSI is incorporated.

  Further, according to the light emitting element driving apparatus of the present embodiment, it is possible to realize a configuration in which the remaining capacity of the power source battery of the device is detected and the light emission amount of the light emitting element is controlled. For example, there is a method in which voltage value information of a terminal voltage (that is, remaining capacity) of a power battery is input to the timer unit 4, a predetermined pulse is generated based on PWM control in the timer unit 4, and is output to the drive control unit 2. . According to this method, when the terminal voltage of the power supply battery is high, a pulse with a high duty ratio is output from the timer unit 4 by PWM control, and the light emitting element is driven to be lit with a high light emission amount. Further, if the terminal voltage of the power supply battery is lowered, the duty ratio is lowered by the PWM control in the timer unit 4, and the light emission amount of the light emitting element is suppressed. Thus, since the light emission amount of the light emitting element can be controlled based on the remaining capacity of the power battery, visibility can be increased or power consumption can be suppressed according to the remaining capacity of the power battery.

  The light emitting element driving device of the present invention is useful for an apparatus including a light emitting element such as an LED.

FIG. 2 is a block diagram illustrating a configuration of a light-emitting element driving device according to Embodiment 1. Timing diagram showing timing signal (light emitting element drive voltage) at the time of DC drive output from the drive control unit Timing chart showing timing signal (light emitting element driving voltage) at the time of pulse driving outputted from the drive control unit 4 is a block diagram illustrating another example of the light-emitting element driving device in Embodiment 1. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Register part 2 Drive control part 3 Oscillation part 4 Timer part 5 Light emitting element drive part 6 1st light emitting element 7 2nd light emitting element 8 Light emitting element drive device 9 External control part

Claims (5)

A light emitting element;
A driving unit for driving the light emitting element to be turned on or off according to an input voltage;
An oscillation unit for generating a reference pulse;
A timer unit that generates a pulse of a predetermined frequency based on a reference pulse output from the oscillation unit;
A drive control unit for controlling operation by outputting a voltage to the drive unit;
A light-emitting element driving device that drives and controls the light-emitting element by at least one of a DC driving method and a pulse driving method,
In accordance with an operation command input from the outside, a register unit that outputs the DC drive or pulse drive command to the drive control unit,
The drive control unit
In the case of direct current driving the light emitting element, in response to a command from the register unit, a direct current voltage is output to the driving unit,
When the light emitting element is pulse-driven, a voltage that is turned on or off at a timing generated by the timer unit is output to the driving unit according to a command from the register unit. The register unit is
The light-emitting element driving device according to claim 1, wherein information relating to the driving method is stored in a table. The drive control unit
The light emitting element driving device according to claim 1, wherein the duty ratio of the voltage can be changed by a command from the register unit during pulse driving. A light emitting element;
A driving unit for driving the light emitting element to be turned on or off according to an input voltage;
An oscillation unit for generating a reference pulse;
A timer unit that generates a pulse of a predetermined frequency based on a reference pulse output from the oscillation unit;
A drive control unit for controlling operation by outputting a voltage to the drive unit;
A light-emitting element driving device that drives and controls the light-emitting element by at least one of a DC driving method and a pulse driving method,
In accordance with an operation command input from the outside, a register unit that outputs the DC drive or pulse drive command to the drive control unit,
The drive control unit
In the case of direct current driving the light emitting element, in response to a command from the register unit, a direct current voltage is output to the driving unit,
When driving the light emitting element in a pulsed manner, the light emitting element driving device outputs a voltage that is turned on or off at a timing generated by the timer unit to the driving unit according to a command from the register unit. Electronics. A clock control unit that is controlled to move in synchronization with a reference pulse generated by the oscillator,
The timer unit is
The electronic device according to claim 4, wherein a pulse having a predetermined frequency is generated based on a reference pulse generated by the oscillator.

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