JP2012028820A - Led drive circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an LED drive circuit that can adjust emitted light quantity of an LED in multiple steps.SOLUTION: An LED drive circuit 3 comprises: a current control circuit 20 having a switching terminal and connected to one end of the LED; a square wave pulse power supply Vcapable of changing a duty factor; and a charging/discharging circuit 21 connected between the square wave pulse power supply Vand the switching terminal of the current control circuit 20. The current control circuit 20 may have a darlington transistor. The square wave pulse power supply Vmay have: an oscillator that outputs first and second pulse trains whose oscillation frequencies are mutually different; and a comparator that outputs voltage based on voltage comparison result between the first pulse train and the second pulse train where the first and second pulse trains are defined as input.

Description

  The present invention relates to an LED drive circuit, and more particularly to an LED drive circuit used for decoration of a gaming machine.

  In gaming machines typified by pachinko gaming machines and spinning-reel gaming machines, the degree of customer satisfaction is influenced by the gaming performance and the impression level given to the player, and the number of gaming machines sold is affected. Therefore, it is important how to make the player attractive by making full use of effects such as the display contents of the display device incorporated in the gaming machine, sound effects, and accessory actions.

  As one of such effects, there is a light decoration, and a large number of light emitters such as LEDs and lamps are arranged on the front surface of the game board of the gaming machine and are individually driven to enhance the effect. For example, ingenuity has been devised to change the lighting pattern and brightness of the light emitters according to the state of the game, such as during standby, during normal games, and during major roles, so that the player can have the expectation of major players.

  Typical examples of LEDs used in such light decoration applications are red, green, and blue. By appropriately arranging these LEDs and controlling the amount of light emitted from each of them, it is possible for the player. It can appear to emit light with various colored light. Also, for example, when playing a big role or during a reach, the player's sense of expectation is clearly given to the player by visually changing the amount of light emitted, the blinking speed, etc., clearly different from the standby state. And can produce a sense of achievement.

  In recent years, in gaming machines, higher brightness LEDs have been used in order to enhance the effect. On the other hand, when such a high-brightness LED is used, in the pachinko hall under an average environment, in order to adjust the light emission amount so that the player can recognize the difference in the brightness of the LED, It is necessary to change the flowing current in a range of a weak current value as compared with the maximum rated current value. In order to perform such control, the LED arranged on the game board is controlled by an LED drive circuit connected to the effect CPU via wiring, and is turned on or off according to a change in the output signal from the effect CPU. Turns off the light.

  As an LED drive circuit that can be used for such a purpose, an indicator dimming system and an LED drive circuit have been developed that can be controlled by an input signal from an external terminal to variably adjust the light output of the LED (Patent Document 1). And 2).

  The indicator dimming system described in Patent Document 1 includes a first switching element for driving an LED, a current limiting resistor that defines a current flowing through the LED, and a second switching element that switches a resistance value of the current limiting resistor. And a microprocessor for controlling the first and second switching elements (see Patent Document 1). Then, by selectively biasing the first switching element and the second switching element by a control signal from the microprocessor, the LED is turned off and the emission luminance is switched.

  However, in the indicator dimming system described in Patent Document 1, the light emission luminance of the LED itself can be switched to only two stages, and the light emission luminance of the LED cannot be changed with more gradations.

  In addition, the LED driving circuit described in Patent Document 2 has a plurality of constant voltage power supplies whose output voltages are turned ON / OFF by a control signal and a collector connected to a power supply terminal based on the outputs of the plurality of constant voltage power supplies. There is a switching circuit comprising the same number of circuit switching transistors and a resistor connected at one end to each of the emitters of the circuit switching transistor and connected at the other end to the anode of the LED. And in this LED drive circuit, since the drive current flows through the LED only through the circuit switching transistor that is biased by the output voltage turned on among the plurality of constant voltage power supplies, the control signal for the constant voltage power supply The light emission amount of the LED can be changed.

  However, in the LED driving circuit described in Patent Document 2, in order to increase the number of LED light emission levels, the number of constant voltage power supplies, circuit switching transistors, and resistors is increased according to the number of stages. is required. Therefore, the LED driving circuit used for the light decoration of the gaming machine becomes expensive, and the amount of necessary wiring becomes very large, which is desirable in terms of increase in the area required for installation and generation of noise. Absent.

  In addition, a device using a pulse width modulation (PWM) method is known as a driving device for a display device LED of a pachinko machine (see Patent Document 3). In the PWM control, the output signal from the CPU is a square wave pulse, and the duty ratio is changed to adjust the average current value flowing through the LED, thereby adjusting the light emission amount of the LED.

  However, when adopting the PWM method, especially when trying to change the light emission amount of the LED in a multistage manner with a relatively small light emission amount, it is necessary to perform a control that slightly changes the duty ratio. It is necessary to form the output waveform at the sampling pitch. Therefore, the load on the CPU is large, and it is necessary to use an expensive and high-performance CPU as the production CPU, or to provide a CPU dedicated to LED control separately from the production CPU. End up.

  Further, in the pachinko machine described in Patent Document 3, some signal lines are shared in order to drive a large number of LEDs with a small number of wires. However, this causes a period in which the power supply is stopped for each LED, making it impossible for the LED to continuously emit light at the maximum luminance, and the brightness felt by the player is also reduced. Further, if the player can only emit light that is not so bright, the impact on the player will be diminished, and it will be difficult to exert a sufficient effect.

Japanese Patent Laid-Open No. 11-272215 JP 63-213379 A JP 2001-252416 A

  In view of the above problems, an object of the present invention is to provide an LED drive circuit capable of adjusting the light emission amount of an LED in multiple stages.

  Another object of the present invention is to provide an LED drive circuit capable of reducing the load on the control CPU.

  In order to achieve the above object, an LED drive circuit according to the present invention includes a current control circuit having a switching terminal and connected to one end of an LED, a square wave pulse power source capable of changing a duty ratio, and a square shape. It has a charging / discharging circuit connected between a wave pulse power supply and the switching terminal of a current control circuit.

  It is possible to use a square wave pulse power supply that can be easily controlled by the CPU, or the output from the CPU itself can be regarded as a power supply output, and the square wave pulse is changed to a pulse whose peak voltage changes depending on its duty ratio. Since the charging / discharging circuit is provided, as will be described later, even in a relatively dark region such as the seventh gradation or less shown in FIG. 1, the LED does not need to be adjusted within a fine range of 1% or less. The brightness of the production CPU can be reduced.

  The current control circuit preferably includes a Darlington transistor. This is because the active operating range of the current control circuit can be set wide.

  Further, the square-wave pulse power supply has an oscillation circuit that outputs first and second pulse trains having different oscillation frequencies and an input of the first and second pulse trains, and the voltage of the first pulse train and the second pulse train. It is preferable to have a comparator that outputs a voltage based on the comparison result of high and low.

  The LED drive circuit has one end connected between the charge / discharge circuit and the switching terminal, and one end connected between the charge / discharge circuit and the switching terminal, the first switching element having the other end grounded. And a second switching element having the other end connected to the constant voltage source, and the first switching element changes the voltage applied to the switching terminal to the ground voltage when the first switching element is turned on. When the second switching element is turned on, the second switching element responds to the constant voltage supplied from the constant voltage source to the switching terminal when the second switching element is turned on. It is preferable to saturate the drive current flowing through the current control circuit and the LED by applying the applied voltage.

  By adopting such a configuration, control is normally performed only when a specific state such as turning off the LED or turning on the maximum brightness appears while periodically changing the brightness of the LED, without particularly giving a control signal. Only by giving a signal, it can be distinguished from the normal state, and an LED drive circuit having a high effect can be configured while reducing the load on the CPU for the effect.

  An LED driving circuit according to another aspect of the present invention includes a switching terminal and a current control circuit connected to one end of the LED, a variable voltage source, a variable voltage source, and an output voltage of the variable voltage source. And a pulse oscillation circuit that generates a pulse wave whose voltage amplitude changes in response to the voltage and applies the pulse wave to the switching terminal.

  By setting it as such a structure, it becomes possible to adjust LED to arbitrary light emission amount.

  The current control circuit preferably includes a Darlington transistor. This is because the active operating range of the current control circuit can be set wide.

  Further, the signal input circuit is connected between the pulse oscillation circuit and the current control circuit and has an external signal input terminal, and when the predetermined voltage is applied to the external signal input terminal, the signal input circuit It is preferable to interrupt or saturate the current control circuit.

  By adopting such a configuration, it is sufficient to give a specific control signal only when a specific state of turning off the LED or turning on the maximum brightness appears while the LED is normally illuminated with a constant light emission amount. An LED driving circuit having a high effect can be configured while reducing a load on a device such as a CPU that controls the LED driving circuit.

  The LED driving system according to the present invention includes a first LED driving circuit and a second LED driving circuit having the external signal input terminal, a first input terminal and an output terminal, and an output terminal. Has a first synthesis circuit connected to an external signal input terminal of the first LED drive circuit, a third and a fourth input terminal, and an output terminal, and the output terminal is an external signal of the second LED drive circuit A second synthesis circuit connected to the input terminal; and a shift register having first and second memories connected serially. The output of the first memory is connected to the first input terminal. The output of the second memory is connected to the third input terminal, and the same control signal is applied to the second input terminal and the fourth input terminal.

  With such a configuration, even when the number of LEDs to be driven is large, the number of output terminals required in the CPU that supplies a control signal to the LED driving system can be reduced, and wiring can be saved. .

  Further, the LED driving circuit or the LED driving system may be packaged as a semiconductor integrated circuit.

  Furthermore, a gaming machine according to the present invention has the above LED drive circuit or LED drive system. Here, the gaming machine refers to a pachinko gaming machine and a revolving type gaming machine.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to provide the LED drive circuit which can adjust the light emission amount of LED in multistep.

  In addition, it is possible to provide an LED drive circuit that can reduce the load on the control CPU.

It is the graph which investigated the change of the duty ratio at the time of changing the brightness of LED observed visually by equal intervals by PWM control. 1 is a circuit diagram of an LED drive circuit according to a first embodiment of the present invention. (A) is a graph which shows the change of the output voltage from the variable voltage source of the LED drive circuit which concerns on 1st Embodiment, (b) is the electric potential of the negative side input terminal of the comparator corresponding to (a). It is a graph which shows a change, (c) is a graph which shows the change of the electric potential applied to the base of the transistor of the current control circuit corresponding to (b), (d) is the cathode of LED corresponding to (c). It is a graph which shows the electric potential change of. It is a circuit diagram of the modification which comprised the current control circuit of the LED drive circuit which concerns on the 1st Embodiment of this invention with the Darlington transistor. It is a circuit diagram of the LED drive circuit which concerns on the 2nd Embodiment of this invention. (A) is a graph which shows the shape of the square wave pulse supplied from the square wave pulse power supply in the LED drive circuit which concerns on 2nd Embodiment, (b) is a change of the square wave pulse of (a). Is a graph showing the change in potential applied to the base of the transistor of the current control circuit, (c) is a graph showing the change in the potential of the cathode of the LED corresponding to (b), (d) is It is a graph which shows the outline of the change of the emitted light amount of LED to drive. It is a circuit diagram of the LED drive circuit which concerns on the 3rd Embodiment of this invention. (A) is a graph which shows the shape of the square wave pulse supplied from the square wave pulse power supply in the LED drive circuit which concerns on 3rd Embodiment, (b) is a change of the square wave pulse of (a). Is a graph showing the change in potential applied to the base of the transistor of the current control circuit, (c) is a graph showing the change in the potential of the cathode of the LED corresponding to (b), (d) is It is a graph which shows the outline of the change of the emitted light amount of LED to drive. It is a circuit diagram of the LED drive circuit which concerns on the 4th Embodiment of this invention. It is a circuit diagram of the LED drive circuit which concerns on the 5th Embodiment of this invention. (A) is a graph which shows the output voltage change of the triangular wave oscillation circuit of the LED drive circuit which concerns on 5th Embodiment, (b) is a graph which shows the output voltage of the comparator corresponding to the output voltage change of a triangular wave oscillation circuit (C) is a graph showing a change in potential applied to the base of the transistor of the current control circuit corresponding to (a) and (b), and (d) is a graph of the LED corresponding to (c). It is a graph which shows the outline of the change of emitted light amount. It is a circuit diagram of the LED drive circuit which concerns on the 6th Embodiment of this invention. (A) is a graph which shows the electric potential of the negative side input terminal of the comparator of the LED drive circuit which concerns on 6th Embodiment, (b) is applied to the base of the transistor of the current control circuit corresponding to (a). (C) is a graph showing an outline of a change in the light emission amount of the LED corresponding to (b). It is a block diagram of the LED drive system which concerns on embodiment of this invention. It is a figure explaining rough correspondence with each signal input waveform and the amount of luminescence of each LED. It is a timing chart showing correspondence between each output signal from the CPU for presentation and a signal inputted to each LED drive circuit.

  First, in order to know how much light output can be used to control the LED used in the light decoration of the gaming machine, the inventor of the present application can use the hall environment for the LED normally used in the gaming machine. The player investigated the amount of light that can be recognized by the player to recognize the difference in brightness of the LED light. The survey results will be described. In this investigation, a red LED having a maximum luminance of 7700 mcd was used.

  FIG. 1 shows that an LED is observed indoors at a distance of 50 cm, and the observer feels that the brightness of the LED has changed 11 steps at regular intervals from the extinguished state to the steady light emitting state at the maximum luminance of the LED. Fig. 5 shows changes in the duty ratio of the pulse voltage applied to the LED when the LED is PWM-controlled. In FIG. 1, the horizontal axis represents gradation, the first gradation represents a light-off state, and the eleventh gradation represents a steady light emission state at the maximum luminance. The vertical axis represents the duty ratio.

  As shown in FIG. 1, the duty ratio is only 0.03% in the second gradation, and the duty ratio is only 0.6% in the sixth gradation that is between the light-off state and the steady light emission state. It was found that the duty ratio reached only 1% in the next seventh gradation and that the duty ratio was only 40% even in the tenth gradation, which was only one step lower than the steady light emission state. Further, as shown in FIG. 1, it has been found that in order for the observer to sense that the brightness of the LED changes at equal intervals, it is necessary to change the interval of the duty ratio nonlinearly. More specifically, in a region where the light emission amount of the LED is relatively small, the observer recognizes that the brightness has changed even if the duty ratio is changed to a small value. However, as the light emission amount of the LED increases, If the ratio is not changed greatly, a person cannot recognize the change in the brightness of the LED.

  Therefore, in order to control the LED so that the player can recognize the change in brightness, not just flickering, it is necessary to change the duty ratio from less than 0.1% to 100% in the case of PWM control. In particular, it is preferable that the duty ratio can be changed with a finer pitch in the range of less than 0.1% to around 1%. Therefore, it is necessary to perform pulse control with a very fine sampling pitch. Also, when controlling by changing the LED drive current value, the drive current value and the light emission luminance are in a proportional relationship, so that the LED can be changed from less than 1/1000 of the maximum rated current value to the maximum rated current value. It is necessary, and it is preferable that it is changed in multiple steps in a very small current region, particularly in a range from less than 1/1000 to around 1/100 of the maximum rated current value.

Hereinafter, an LED drive circuit according to the present invention will be described in detail with reference to the drawings.
FIG. 2 shows a circuit diagram of the LED drive circuit 1 according to the first embodiment of the present invention.
In the LED drive circuit 1 according to the first embodiment of the present invention, a current control circuit 10 for supplying a drive current to the LED 1 is connected to one end of the LED 1, and the switching terminal of the current control circuit 10 is connected to a constant cycle. And a variable voltage source V _in1 connected to the pulse oscillation circuit and capable of controlling the amplitude of the pulse wave oscillated from the pulse oscillation circuit 11. By having such a configuration, the light emission amount of the LED ₁ can be adjusted by adjusting the output voltage of the variable voltage source V _in1 based on the control signal from the CPU for performance, and it is used for light decoration with a high effect. It is possible.

As shown in FIG. 2, a voltage _Vcc is supplied to the anode of the LED 1 to be controlled from a constant voltage power source (not shown) via a resistor R _L1 . The cathode of the LED ₁ is connected to the collector of a transistor Tr ₁ which is a current control circuit 10. On the other hand, the emitter of the transistor Tr ₁ is grounded.

The base of the transistor Tr ₁ which is a switching terminal of the current control circuit 10 is connected to the resistor R ₈ of the pulse oscillation circuit 11 and the emitter of the transistor Tr ₂ via the resistor R ₁ .

Pulse oscillation circuit 11 is composed of a comparator CMP1, the transistor Tr _2, a capacitor C _1, diode D _1, and a resistor R ₂ to R _8.

The LED1 constant pressure power source for supplying a driving current (not shown), the collector of the transistor Tr ₂ are connected. Similarly, the constant pressure supply, one end of each of the capacitors C ₁ and a resistor R ₄ to be connected in parallel is connected. The base of the transistor Tr ₂ is, via a resistor R _7, are connected to the other ends of the capacitor C ₁ and resistor R _4. Further, the emitter of the transistor Tr ₂ is grounded via a resistor R ₈ and connected to the base of the transistor Tr ₁ of the current control circuit 10 via a resistor R ₁ .

The other end of each of the capacitor C ₁ and the resistor R ₄ is connected to the negative input terminal of the comparator CMP ₁ and also connected to the output terminal of the comparator CMP ₁ via the resistor R ₅ and the diode D _1. ing. Incidentally, the cathode of the diode D ₁ is connected to the output terminal of the comparator CMP1.

The positive input terminal of the comparator CMP1, with one end of the resistor R ₂ and the resistor R ₃ is connected, is also connected to the cathode of the diode D ₁ via a resistor R _6. Then, the other end of the resistor R _2, the anode of the variable voltage source V _in1 is connected. The other end of the resistor R ₃ is grounded.

The variable voltage source V _in1 changes the voltage applied to the pulse oscillation circuit 11 based on a control signal from an effect CPU (not shown).

Hereinafter, the operation of the LED drive circuit 1 according to the first embodiment of the present invention will be described.
FIG. 3A is a graph showing the voltage change of the applied voltage V of the variable voltage source V _in1 , and FIG. 3B shows the change of the potential V2 of the negative input terminal of the comparator CMP1 corresponding to FIG. a graph, (c) is a graph showing the change in the potential V3 applied to the base of the transistor Tr ₁ corresponding to (b). FIG. 3D is a graph showing changes in the cathode potential V4 of the LED1.

The pulse oscillation circuit 11 is an oscillation circuit using the positive feedback operation of the comparator CMP1, and the emitter potential V3 of the emitter follower Tr ₂ follows this by repeating the discharge operation and the charge operation in the capacitor C _1. And periodically fluctuate. Specifically, when the capacitor C ₁ is not sufficiently charged, the potential V2 of the negative input terminal of the comparator CMP1 is higher than the potential of the positive input terminal, and therefore the potential of the output terminal of the comparator CMP1 is low. Become. In this case, the program proceeds natural charge in the path of the resistor R ₄ and R _5, since the intermediate potential between the resistor R ₄ the resistance R ₅ is input to the emitter follower Tr _2, according to the charging status of the above, the transistor Tr ₁ is Biased. Thereafter, when the charge amount of the capacitor C ₁ increases, the potential V2 gradually decreases, and the emitter follower output voltage V3 also decreases. For this reason, the operating point of the transistor Tr ₁ shifts to the cut-off region side, and as a result, the light emission luminance of the LED 1 decreases.

When the capacitor C ₁ is further charged, the voltage applied to the positive input terminal of the comparator CMP1 exceeds the voltage V2 applied to the negative input terminal, and the output of the comparator CMP1 becomes a high potential. Therefore, the capacitor C ₁ performs a _one-time discharge operation, and the voltage V2 starts to rise. This discharge operation is continued until the positive terminal potential moved to the higher side is reached.

Here, when the voltage applied from the variable voltage source is set relatively high, as shown in FIGS. 3A and 3B, the voltage is applied to the positive side input terminal and the negative side input terminal of the comparator CMP1. The voltage rises overall. Accordingly, the voltage V3 which is biased to the transistor Tr ₁ is also increased with increasing voltage V2, the light emission amount of LED1 is increased.

Conversely, when the voltage V applied from the variable voltage source V _in1 is set relatively low, the operation of the pulse oscillation circuit 11 is opposite to the above, and the peak value of the voltage V3 biased by the transistor Tr ₁ is reduced. And the light emission amount of LED1 falls.

Here, the peak value of the voltage V3 from the cutoff point of the transistor Tr _1, to fit between the saturation point of the transistor Tr _1, appropriately configure each resistance value. If the peak value of the voltage V3 falls below the cut-off point of the transistor Tr _1, the driving current to the LED1 does not flow, LED1 is because no light is emitted, whereas the peak value of the voltage V3 exceeds the saturation point of the transistor Tr _1, the voltage This is because, while V3 is above the saturation point, light is emitted at the maximum luminance, so that it is difficult to appropriately control brightness.

As described above, the LED drive circuit 1 according to the first embodiment of the present invention controls the output voltage of the variable voltage source V _in1 by, for example, a control signal from the effect CPU, thereby driving the LED drive current. a transistor Tr ₁ is can be controlled by both the duration and the peak value entering the active region, thereby the light emission amount of the LED freely changed. In particular, if the frequency of the pulse output from the pulse oscillation circuit 11 is set to a high value such as 50 Hz or more so that the change in brightness due to the brightness change of the LED for each pulse is not visually recognized, the brightness of the LED Can be sensed according to the average of the light emission luminance of the LED or the light emission amount within a certain period of time, so that the LED in a low light emission region where the brightness of the LED is perceived with a slight change in the light emission amount. Control becomes easy. Further, a constant pressure power source is used as a power source for supplying a driving current to the LED, and a system for controlling the light emission amount of the LED is separately configured. Therefore, the LED driving circuit 1 can operate stably. .

Further, in the LED drive circuit 1 described above, two transistors Tr ₃ and Tr ₄ connected in Darlington may be used instead of the transistor Tr ₁ which is the current control circuit 10. A circuit diagram of an LED drive circuit 2 according to a modification of the first LED drive circuit 1 is shown in FIG. As described above, if the current control circuit 12 is configured by a Darlington transistor, the active operating range of the transistor Tr ₃ can be expanded as compared with a single transistor.

Next, an LED drive circuit 3 according to a second embodiment of the present invention will be described.
FIG. 5 shows a circuit diagram of the LED drive circuit 3 according to the second embodiment of the present invention.
In the LED drive circuit 3 according to the second embodiment of the present invention, a current control circuit 20 for supplying a drive current to the LED 2 is connected to one end of the LED 2, and a charge / discharge circuit is connected to a switching terminal of the current control circuit 20. A square wave pulse power source V _in2 connected via the square wave power source 21 is provided, and a square wave pulse input from the square wave pulse power source V _in2 has a triangular shape in which the charge / discharge circuit 21 has a peak value corresponding to the pulse width. After being converted to a wave pulse, the light emission amount of the LED 2 can be controlled by PWM control by applying it to the current control circuit 20. Further, in the LED drive circuit 3, the adjustment of the light emission amount of the LED can be performed using a large change ratio of the duty ratio as compared with the case where the square wave pulse is directly supplied to the LED, particularly in a weak light emission range. Is possible.

As shown in FIG. 5, a voltage V _cc is supplied to the anode of the LED 2 to be controlled from a constant pressure power source (not shown) via a resistor R _L2 . On the other hand, the collector of the transistor Tr ₈ constituting the current control circuit 20 is connected to the cathode of the LED 2. In addition, the emitter of the transistor Tr ₈ is grounded. The base of the transistor Tr ₈ is a switching terminal is connected through a capacitor C _2, resistors R ₁₂ and resistor R ₁₃ to the collector of the transistor Tr _7, the charge and discharge circuit 21.

The charge / discharge circuit 21 includes a capacitor C ₂ , transistors Tr ₅ , Tr ₆ , Tr ₇ , and resistors R ₁₁ , R ₁₂ . The emitters of the transistors Tr ₆ and Tr ₇ are connected to a constant voltage power source and supplied with a voltage V _cc . The bases of the transistors Tr ₆ and Tr ₇ are connected to each other and to the collector of the transistor Tr ₆ . Further, the collector of the transistor Tr ₆ is connected to the collector of the transistor Tr ₅ via the resistor R ₁₁ . The emitter of the transistor Tr ₅ is grounded, the base of the transistor Tr ₅ is connected to the anode of the square-wave pulse power V _in2 through a resistor R _10. On the other hand, the collector of the transistor Tr ₇ is connected to one end of the resistor R ₁₂ and the capacitor C ₂ . The other end of the capacitor C ₂ is grounded. The collector of the transistor Tr ₇ via a resistor R _13, a switching terminal of the current control circuit 20 is connected to the base of the transistor Tr _8.

The square wave pulse power source V _in2 outputs a square wave pulse that alternately generates a supply voltage V _cc to the LED ₂ and a potential corresponding to GND. The frequency and duty ratio of the square wave pulse can be changed based on, for example, a control signal from an effect CPU (not shown).

Hereinafter, the operation of the LED drive circuit 3 according to the second embodiment of the present invention will be described.
FIG. 6 shows an operation state of the LED drive circuit 3 according to the second embodiment of the present invention.
The graph in FIG. 6A shows the shape of a square wave pulse supplied from a square wave pulse power source. Graph (b) shows relative change in the square wave pulse, the change in the base potential V5 of the transistor Tr _8. The graph of (c) shows the potential V6 of the cathode of LED2. And the graph of (d) shows the outline of the change of the emitted light amount per unit time of LED2.

If the voltage supplied from the square-wave pulse power V _in2 is at a high potential (V _cc), the transistor Tr ₅ of the charging and discharging circuit 21 is biased, the state is ON. Therefore, the transistors Tr ₆ and Tr ₇ that are constant current sources are activated, and the capacitor C ₂ is charged. As the charging of the capacitor C ₂ is advanced, the voltage applied to the base of the transistor Tr ₈ of the current control circuit 20 V5 becomes high.

On the other hand, when the voltage supplied from the square-wave pulse power is low potential (GND), the transistor Tr ₅ is in a state of OFF without being biased. At this time, the capacitor C ₂ performs a discharging operation through the resistor R ₁₁ . Therefore, the voltage V5 applied to the base of the transistor Tr ₈ of the current control circuit 20 is rapidly lowered.

As shown in FIG. 6, when the duty ratio of the square wave is relatively small, the capacitor C ₂ is not sufficiently charged, the peak value of the voltage V5 which is biased to the transistor Tr ₈ from the charge-discharge circuit 21 is low. Peak value of V5 is, when below the cut-off point of the transistor Tr _8, since no current flows through the transistor Tr _8, thus LED2 does not emit light.

On the other hand, as the duty ratio of the square wave increases, the amount of charge to the capacitor C ₂ also increases, and the voltage V5 that biases the transistor Tr ₈ also increases. When the peak value of V5 is to exceed the cut-off point of the transistor Tr _8, the transistor Tr ₈ becomes the ON state only during the period that exceeded the cutoff point, through the transistor Tr _8, become a driving current flows through the LED2, The LED 2 emits light. Incidentally, this case also, the voltage V5 decreases due to discharge of the capacitor C _2, LED2 is turned off.

  Further, when the duty ratio of the square wave is increased, the drive current flowing through the LED 2 is relatively increased and the light emission amount of the LED 2 is also increased. When the predetermined duty ratio is exceeded, the voltage V5 increases until the drive current of the LED 2 reaches the maximum rated value, and the LED 2 emits light with the maximum luminance.

Finally, when the duty ratio is 100%, that is, when a steady voltage is supplied from the square-wave pulse power source _Vin2 , the LED 2 maintains lighting at the maximum luminance.

As described above, in the LED drive circuit 3 according to the second embodiment of the present invention, since the current control circuit 20 is biased with a triangular wave pulse, the peak value of the triangular wave and the transistor Tr ₈ are in the active region. The amount of light emission of the LED can be controlled by both the time width of entering. As a result, the amount of light emitted from the LED can be controlled in detail even when the amount of change in the duty ratio is coarser than when the square wave pulse is simply supplied to the LED, so that the load on the CPU that controls the square wave pulse power supply can be reduced. .

An LED drive circuit 4 according to the third embodiment of the present invention will be described.
FIG. 7 shows a circuit diagram of the LED drive circuit 4 according to the third embodiment of the present invention.
As shown in FIG. 7, the LED drive circuit 4 according to the third embodiment of the present invention _generates a square wave output from the square wave pulse power source V _{in3 in the same} manner as the LED drive circuit 3 according to the second embodiment. The amount of light emitted from the LED 3 is controlled by generating a triangular wave by inputting it to the charge / discharge circuit 31 and inputting the triangular wave to the switching terminal of the current control circuit 30. The LED drive circuit 3 according to the second embodiment is different from the LED drive circuit 3 in that the configuration of the charge / discharge circuit is different and a Darlington transistor is used as the current control circuit 30.

As shown in FIG. 7, a voltage V _cc is supplied to the anode of the LED 3 to be controlled from a constant voltage power source (not shown) via a resistor R _L3 . On the other hand, the collectors of Darlington transistors Tr ₁₁ and Tr ₁₂ constituting the current control circuit 30 are connected to the cathode of the LED 3. In addition, the emitter of the transistor Tr ₁₂ is grounded. The emitter of the transistor Tr ₁₁ is connected to the base of the transistor Tr ₁₂ and grounded via the resistor R ₁₄ . The base of the transistor Tr ₁₁ that is a switching terminal of the current control circuit 30 is connected to the capacitor C ₃ and the resistors R ₁₂ and R ₁₃ of the charge / discharge circuit 31.

The charge / discharge circuit 31 includes a capacitor C ₃ , a diode D ₂ , transistors Tr ₉ and Tr ₁₀ , and resistors R ₁₅ , R ₁₆ , R ₁₇ and R ₁₈ . The collector of the transistor Tr ₉ is connected to a constant pressure source is supplied a voltage V _cc. The base of the transistor Tr ₉ is connected via a resistor R ₁₅ and R ₁₆ are connected in series, are connected to the base of the transistor Tr _10. Incidentally, between the resistors R ₁₅ and R _16, the diode D ₂ is connected. On the other hand, the emitter of the transistor Tr ₉ is connected via a resistor R ₁₇ and R ₁₈ are connected in series, are connected to the collector of the transistor Tr _10. In addition, the emitter of the transistor Tr ₁₀ is grounded.

Further, one end of the capacitor C ₃ is connected between the resistors R ₁₇ and R ₁₈ connected in series, and at the same time, the base of the transistor Tr ₁₁ of the current control circuit 30 is also connected. The other end of the capacitor C ₃ is grounded.

The anode of the square-wave pulse power V _in3 is connected between the diode D ₂ and resistor R ₁₆ of the charge and discharge circuit 31. This square wave pulse power source V _in3 is the same as the square wave pulse power source V _{in2 of the} LED drive circuit 3 according to the second embodiment, and alternately generates a supply voltage V _cc to the LED 3 and a potential corresponding to GND. Outputs square wave pulses. Further, for example, the duty ratio and the pulse frequency can be changed by a control signal from an effect CPU (not shown).

Hereinafter, the operation of the LED drive circuit 4 according to the third embodiment of the present invention will be described.
FIG. 8 shows an operation state of the LED drive circuit 4 according to the third embodiment of the present invention.
The graph of FIG. 8A shows the shape of a square wave pulse supplied from the square wave pulse power source _Vin3 . Graph (b) shows relative change in the square wave pulse, the change in the base potential V7 of the transistor Tr _11. The graph of (c) shows the potential V8 of the cathode of LED3. And the graph of (d) shows the outline of the change of the emitted light quantity per unit time of LED3.

When the voltage supplied from the square wave pulse power supply is at a low potential (GND), the charge / discharge circuit 31 biases the transistor Tr ₉ connected between the constant pressure power supply for supplying the voltage _Vcc and the square wave pulse power supply _Vin3. As a result, the state becomes ON. The transistor Tr ₁₀ is connected between the square-wave pulse power V _in3 and GND are not biased, a state of OFF. Therefore, a current flows through the transistor Tr _9, the capacitor C ₃ is connected through a resistor R ₁₇ to the collector of the transistor Tr ₉ is charged. The voltage V7 applied to the base of the transistor Tr ₁₁ of the current control circuit 30 as the capacitor C ₃ is charged is also increased.

On the other hand, when the voltage supplied from the square-wave pulse power is high potential (V _cc), the transistor Tr ₉ is in a state of OFF without being biased. Further, the state of the ON transistor Tr ₁₀ is biased. At this time, since the capacitor C ₃ is connected to the collector of the transistor Tr ₁₀ via the resistor R ₁₈ , a discharge operation is performed through the Tr ₁₀ . Therefore, the voltage V7 is applied to the base of the transistor Tr ₁₁ of the current control circuit 30 is rapidly lowered.

As shown in FIG. 8, when the duty ratio of the square wave is relatively large, the capacitor C ₃ is not sufficiently charged, the charging and discharging circuit 31 voltage V7 is biased decreases in the transistor Tr ₁₁ from, thus LED3 The driving current that flows is also reduced. Further, the discharge of the capacitor C _3, since the voltage applied V7 to the base of the transistor Tr ₁₁ is equal to GND, LED 3 is turned off.

On the other hand, as the duty ratio of the square wave decreases, the amount of charge to the capacitor C ₃ also increases, and the voltage V7 that biases the transistor Tr ₁₁ also increases. Therefore, the drive current flowing through the LED 3 is relatively increased, and the light emission amount of the LED 3 is also increased. When the predetermined duty ratio is exceeded, the capacitor C ₃ is charged until the transistor Tr ₁₂ is saturated, the drive current of the LED 3 becomes the maximum rated value, and the LED 3 emits light with the maximum luminance.

Finally, when the duty ratio is 0%, that is, when a steady voltage is supplied from the square wave pulse power source _Vin3 , the LED 3 maintains lighting at the maximum luminance.

As described above, in the LED drive circuit 4 according to the third embodiment of the present invention, the current control circuit 30 is also biased with a triangular wave pulse, similarly to the LED drive circuit 3 according to the second embodiment. Therefore, the peak value of the triangular wave, the transistor Tr ₁₁ can control the light emission amount of the LED in both the time width entering the active region. As a result, the amount of light emitted from the LED can be controlled in detail even when the amount of change in the duty ratio is coarser than when the square wave pulse is simply supplied to the LED, so that the load on the CPU that controls the square wave pulse power supply can be reduced. .

  Note that the LED drive circuit 3 according to the second embodiment has a characteristic that the potential applied to the current control circuit 20 at the time of charging rises relatively linearly, but the LED drive circuit 4 according to the third embodiment. Then, as the potential applied to the current control circuit 30 increases, the increase degree becomes exponentially dull. Therefore, when using a very low frequency of the square wave pulse output from the square wave pulse power supply and using it in a state where the brightness change of the LED corresponding to each square wave pulse can be sensed, the LED drive When the LED drive circuit 4 is used rather than the circuit 3, it is possible to lengthen the period during which the LED gradually becomes brighter in one period of the square wave pulse.

Further, in the LED driving circuit 3, the range of the voltage applied to the current control circuit 20 for lighting the LED2 below the maximum brightness is limited to between saturation point and cutoff point of the transistor Tr _8, LED driving circuit 4, the range of the voltage applied to the current control circuit 30 for lighting the LED 3 below the maximum luminance is a region where the transistor Tr ₁₁ is ON and the transistor Tr ₁₂ is OFF, that is, V _be11 <V3 <V _be11. It becomes + V _be12 , and a relatively wide active range can be secured. Here, V _be11 is a voltage for _turning on the transistor Tr ₁₁ , and V _be12 is a voltage for _turning on the transistor Tr ₁₂ .

Next, an LED drive circuit 5 according to a fourth embodiment of the present invention will be described.
FIG. 9 shows a circuit diagram of an LED drive circuit 5 according to the fourth embodiment of the present invention.
As shown in FIG. 9, the LED drive circuit 5 according to the fourth embodiment of the present invention uses a square wave pulse power supply _Vin3 of the LED drive circuit 4 according to the third embodiment of the present invention as a repeat circuit 41. The LED brightness can be changed at a constant cycle without using a control signal from an external control device such as an effect CPU.

In this embodiment, as in the LED drive circuit 1 according to the first embodiment, the current control circuit 40 is configured by one transistor Tr ₁₃ . However, the current control circuit 40 may be a Darlington transistor similarly to the LED driving circuit 4 according to the third embodiment.

As shown in FIG. 9, the repeat circuit 41 includes a triangular wave oscillation circuit Osc that oscillates two types of triangular waves having different periods and a comparator CMP2. A relatively short period triangular wave V9 oscillated from the triangular wave oscillation circuit Osc is input to the + side terminal of the comparator CMP2, while a relatively long period triangular wave V10 is input to the − side terminal of the comparator CMP2. The The comparator CMP2 generates a high potential ( _Vcc ) when the voltage of V10 is lower than the voltage of V9, and conversely, when the voltage of V10 is higher than the voltage of V9, the comparator CMP2 generates a low potential (GND). ) Output. As a result, the charge / discharge circuit 31 receives a square wave pulse whose pulse duty ratio periodically changes.

Furthermore, an LED drive circuit 6 according to a fifth embodiment of the present invention will be described below.
FIG. 10 shows a circuit diagram of an LED drive circuit 6 according to the fifth embodiment of the present invention.
As shown in FIG. 10, the LED drive circuit 6 according to the fifth embodiment of the present invention is provided between the charge / discharge circuit 31 and the current control circuit 40 of the LED drive circuit 5 according to the fourth embodiment of the present invention. The first signal input circuit 42 and the second signal input circuit 43 are connected, and the brightness of the LED 4 is changed at a constant cycle, and the LED 4 is turned off or the maximum brightness is being input only during the input of a specific signal. Thus, it is possible to maintain the lighting state at.

The first signal input circuit 42 includes transistors Tr ₁₄ and Tr ₁₅ , resistors R ₂₀ , R ₂₁ and R ₂₂ . From the emitter of the transistor Tr _14, the voltage V _cc is supplied, whereas the collector is connected to the base of the transistor Tr ₁₃ of the current control circuit 40 via the resistor R ₂₁ and R _19. The base of the transistor Tr ₁₄ is connected to the collector of the transistor Tr ₁₅ via the resistor R ₂₀ . The emitter of the transistor Tr ₁₅ is grounded. Then, the base of the transistor Tr _15, and the all-on signal input terminal T _in1 is connected via a resistor R _22. As can be seen with reference to FIG. 10, when a voltage sufficient to bias Tr ₁₄ and Tr ₁₅ is applied to all the lighting signal input terminals T _in1 , via the transistor Tr ₁₄ and the resistors R ₂₁ and R ₁₉ , transistor Tr ₁₃ is biased from V _cc. Therefore, by selecting the value of resistor R ₂₁ as appropriate, the bias voltage to the Tr ₁₃ can be larger than the saturation point of the Tr _13, it is possible to light the LED4 at maximum brightness.

On the other hand, the signal input circuit 43 includes a transistor Tr ₁₆ and a resistor R ₂₃ . The collector of the transistor Tr ₁₆ is connected to the base of the transistor Tr ₁₃ via the resistor R _19, and the emitter of the transistor Tr ₁₆ is grounded. Then, the base of the transistor Tr _16, and the turn-off signal input terminal T _in2 is connected via a resistor R _23. As can be seen with reference to FIG. 10, when a voltage sufficient to bias the transistor Tr ₁₆ is applied to the turn-off signal input terminal T _in2 , a current flows to the GND through the transistor Tr ₁₆ , so that the transistor Tr ₁₃ is unconditional. LED4 is turned off.

This is shown in FIG. FIG. 11A shows an output waveform from the triangular wave oscillation circuit Osc, and FIG. 11B shows an output of the comparator CMP2 corresponding to the output waveform of the triangular wave oscillation circuit Osc. 11A and 11B, the horizontal axis of the graph represents elapsed time, and the vertical axis represents voltage. Also FIG. 11 (c) is a diagram showing how the voltage V12 applied to the base of the transistor Tr ₁₃ of the current control circuit 40 corresponds to the output waveform of the triangular wave oscillation circuit Osc and comparator CMP2 changes, Figure 11 (d) is a diagram schematically showing how the light emission amount per unit time of the LED 4 changes corresponding to the change of the voltage V12.

As shown in FIGS. 11C and 11D, the voltage V12 that changes according to the output voltage V11 from the comparator CMP2 unless there is a signal input from the full lighting signal input terminal T _in1 and the extinction signal input terminal T _in2. Along with the increase / decrease, the light emission amount of the LED 4 repeatedly increases / decreases. However, when a signal is input to the all-lighting signal input terminal T _in1 or the light-off signal input terminal T _in2 , the voltage V12 is applied to the all-lighting signal input terminal T _in1 or the light-off signal input terminal T regardless of the output from the comparator CMP2. _{Under the} control of the signal from _in2 , the LED 4 is turned off or turned on with the maximum luminance.

  As described above, in the LED drive circuit 6 according to the fifth embodiment of the present invention, since it is only necessary to input a signal only when the LED is turned off or the maximum luminance is turned on, the LED drive circuit is It is possible to greatly reduce the load on the controlling CPU for presentation.

  In the fourth and fifth embodiments, a triangular wave oscillation circuit is used as a circuit for oscillating two types of pulse trains used in the repeat circuit 41. However, the present invention is not limited to this. For example, two sine wave oscillation circuits that generate sine waves having different oscillation frequencies may be used instead of the triangular wave oscillation circuit. As these oscillation circuits, it is not necessary to use special ones, and well-known oscillation circuits can be used.

  In addition, even if the signal input circuits 42 and 43 similar to the above are added to the LED driving circuit 1 or 2 according to the first embodiment of the present invention, the LED driving circuit 5 according to the fifth embodiment of the present invention and Similar functions can be realized. FIG. 12 shows a circuit diagram of an LED drive circuit 7 in which signal input circuits 42 and 43 are added to the LED drive circuit 2 described above.

As shown in FIG. 12, in the LED drive circuit 7, the signal input circuits 42 and 43 are connected between the pulse oscillation circuit 11 and the current control circuit 12. As in the fifth embodiment, the transistors Tr ₃ and Tr ₄ of the current control circuit are biased at a high potential while a high potential signal is being input to all the lighting terminals _{Tin 1} of the signal input circuit 42. As a result, the saturation point of Tr ₄ is exceeded and the LED 1 emits light with the maximum luminance. Conversely, while entering the high potential signal to the off terminal T _in2 signal input circuit 43, the transistors Tr ₃ and Tr ₄ are not biased and remains LED1 is turned off.

This is shown in FIG.
FIG. 13A is a graph showing the potential V2 of the negative input terminal of the comparator CMP1 of the LED drive circuit 7 according to the sixth embodiment, and FIG. 13B is a transistor of the current control circuit corresponding to FIG. is a graph showing changes in potentials applied to the base of tr _3, (c) is a graph showing an outline of a change in the emission amount of the LED corresponding to (b). As can be seen from FIGS. 13 (b) and 13 (c), in the LED drive circuit 7, LED1 depends on the voltage applied from the pulse oscillation circuit 11 to the current control circuit unless a signal is input to the signal input circuits 42 and 43. The light is emitted with a relatively small amount of light (dark lighting). On the other hand, while the signal is input to the signal input circuit 42, the LED 1 emits light with the highest luminance (dazzling lighting). Conversely, the LED 1 is turned off while a signal is being input to the signal input circuit 43.

In FIG. 14, the block diagram of the LED drive system 8 which concerns on embodiment of this invention is shown.
The LED drive system 8 according to the embodiment of the present invention includes three LED drive circuits 6 according to the fifth embodiment of the present invention, and each LED drive circuit 6a, 6b, 6c is combined with the shift register 50. Control is performed using AND circuits 51 to 56 which are circuits. In this embodiment, the LED drive circuits 6a, 6b, and 6c can be driven by three types of external signals, that is, a Data signal, a clock signal, and an ST signal, compared with a case where the same number of LED drive circuits are directly controlled. Thus, the number of output terminals of the production CPU can be reduced and wiring can be saved.

  As shown in FIG. 14, the signal input terminals of the LED drive circuits 6a, 6b, and 6c are connected to the output terminals of the AND circuits 51 to 56, respectively. Further, the outputs Q1 to Q6 and ST signals of the memories M1 to M6 at each stage of the shift register 50 are input to the AND circuits 51 to 56, respectively. Further, the data signal and the clock signal are input to the shift register 50. The Data signal, the clock signal, and the ST signal are output from the effect CPU 57, respectively.

  The operation of the LED drive system 8 according to the embodiment of the present invention will be described with reference to FIGS. 15 and 16. FIG. 15 shows a schematic correspondence between each signal input waveform and the light emission luminance of the LEDs 5, 6 and 7 driven by the LED driving circuits 6a, 6b and 6c, respectively.

  FIG. 15 is a timing chart showing the correspondence between the output signals from the effect CPU 57 and the signals input to the LED drive circuits 6a, 6b, 6c.

  As shown in FIG. 15, for example, all signals are turned off (low potential) in a standby state or a normal gaming state. In this case, since the drive current flowing through the LED 5, LED 6, and LED 7 depends only on the output waveform from the triangular wave oscillation circuit such as the LED drive circuit 6a, it repeatedly brightens or darkens at a constant cycle.

  On the other hand, when the gaming state is reaching or playing a major role, each LED starts to output each signal from the production CPU, and each LED enters a light-off state or a maximum luminance light-emitting state. It is possible to perform such an effect as to make it appear and excite the player's expectation. In this case, the Data signal and the clock signal are input to the shift register 50, and the outputs Q1 to Q6 of each stage of the shift register 50 are used as signal inputs to the LED drive circuits. Despite following the same communication rules for each LED drive circuit, different operations can be performed on LED5, LED6, and LED7.

This will be described with reference to FIG.
The top three graphs in FIG. 16 are timing charts of the clock signal, the Data signal, and the ST signal in order from the top. The six graphs below are timing charts of outputs Q1 to Q6 of each stage of the shift register S in order from the top. The six graphs at the bottom are timing charts of output signals of the AND circuits 51 to 56 in order from the top. The vertical axis of each graph represents the potential (high potential is H and low potential is L).

First, the state of the Data signal corresponding to the down edge of the clock signal is input to the shift register 50. For example, as shown in FIG. 16, six consecutive Data signals are input in the order of {L, L, H, L, L, H}. At this time, {H, L, L, H, L, L} signals are stored in the memories M1 to M6 of each stage of the shift register 50, respectively. In this state, when the ST signal becomes H, the output signals x1 to x6 of the AND circuits 51 to 56 become {H, L, L, H, L, L}, respectively. Accordingly, the output signals x1 and x2 are, LED drive circuit 6a which is connected to all the light-up signal input terminal T _IN1A and off signal input terminal T _IN2A respectively, because all lighting input signal is ON, it turns on the LED5 with maximum brightness Let Similarly, the LED drive circuit 6b to which the output signals x3 and x4 are connected to the all-lighting signal input terminal T _in1b and the light-off signal input terminal T _in2b , respectively, turns off the LED 6 because the light-off input signal is ON. Finally, since the output signals x5 and x6 are respectively connected to the full lighting signal input terminal T _in1c and the extinction signal input terminal T _in2c , both the full lighting input signal and the extinction input signal are OFF. The LED 7 repeats increase / decrease in brightness at a constant cycle.

  As described above, the LED driving system 8 according to the embodiment of the present invention can perform different operations on a plurality of LEDs by only three signal outputs from the effect CPU. Moreover, it is also possible to simultaneously emit all LEDs at the maximum luminance as necessary while sharing the signal line from the effect CPU.

  In the above embodiment, the LED driving system 8 has been described as controlling three LEDs, but the number of LEDs to be controlled is not limited to three. When an LED and a drive circuit for driving the LED are added, the number of shift register stages is increased by the number of signal input terminals of the LED drive circuit to be added, and the output from the memory of the added stage is combined. Control can be similarly performed by adding a circuit.

  In the above embodiment, the synthesis circuit that synthesizes the output from the shift register and the ST signal from the effect CPU has been described as an AND circuit, but has a configuration of two inputs and one output like a NOR circuit. Other logic circuits may be used.

  Although the LED driving circuit and the LED driving system according to the present invention have been described above, the present invention is not limited to the above examples. For example, in each of the above embodiments, the current control circuit is connected to the cathode side of the LED. However, it is possible to change the configuration to connect the current control circuit to the anode side of the LED. Furthermore, the resistance constituting the LED drive circuit can be optimized as appropriate depending on the LED to be used and the supply voltage to the LED. Such modifications can be easily made by those skilled in the art within the scope of the present invention.

1, 2, 3, 4, 5, 6, 6a, 6b, 6c, 7 LED drive circuit 8 LED drive system 10, 12, 20, 30, 40 Current control circuit 11 Pulse oscillation circuit 21, 31 Charge / discharge circuit 41 Repeat Circuit 42, 43 Signal input circuit 50 Shift register 51, 52, 53, 54, 55, 56 AND circuit 57 CPU for presentation
R _{1 to} R ₂₃ , R _{L1 to} R _L4 Resistance Tr _{1 to} Tr ₁₆ Transistor D ₁ , D ₂ Diode LED _{1 to} LED 7 LED
V _in1 , variable voltage source V _in2 , V _in3 square wave pulse power supply T _in1 , T _in1a , T _in1b , T _in1c all lighting signal input terminal T _in2 , T _in8a , T _in2b , T _in2c unlit signal input terminal Osc Triangular wave oscillation circuit CMP1, CMP2 comparator C _1, C _2, C ₃ capacitor

Claims (6)

A current control circuit having a switching terminal and connected to one end of the LED;
An LED driving circuit comprising: a square wave pulse power supply capable of changing a duty ratio; and a charge / discharge circuit connected between the square wave pulse power supply and the switching terminal of the current control circuit.   The LED driving circuit according to claim 2, wherein the current control circuit includes a Darlington transistor.   The square-wave pulse power supply includes an oscillation circuit that outputs first and second pulse trains having different oscillation frequencies, and the first and second pulse trains as inputs, and the first pulse train and the second pulse train. The LED drive circuit according to claim 1, further comprising a comparator that outputs a voltage based on a comparison result of the voltage level. A first switching element having one end connected between the charge / discharge circuit and the switching terminal and the other end grounded;
A second switching element having one end connected between the charge / discharge circuit and the switching terminal and the other end connected to a constant voltage source;
The first switching element cuts off a drive current flowing through the current control circuit and the LED by lowering a voltage applied to the switching terminal to a ground voltage when the first switching element is turned on,
When the second switching element is turned on, the second switching element applies a voltage according to a constant voltage supplied from the constant voltage source to the switching terminal, thereby the current control circuit and the LED. The LED drive circuit according to claim 3, wherein the drive current flowing through the LED is saturated.   A semiconductor integrated circuit comprising the LED drive circuit according to claim 1.   A gaming machine comprising the LED driving circuit according to claim 1.

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