JP6662675B2 - Light lighting control circuit - Google Patents

Description

  The present invention relates to a light lighting control circuit, and more particularly to a light lighting control circuit using a light emitting diode as a light source.

  2. Description of the Related Art In recent years, the use of light-emitting diodes with low power consumption and high light-emission intensity as light sources for vehicles has been increasing.

  In such a case, a light-on control circuit designed to secure the light quantity of the light and the life of the light-emitting diode by driving the light-emitting diode with a constant current may be used. Further, in some of such lighting control circuits, a manual lighting switch for turning on and off a light emitting diode is attached near a battery or the like.

  Under such circumstances, Patent Literature 1 relates to a light emitting diode lamp lighting device in which a lamp driving power supply and a switch unit are connected, and the lamp driving power supply has a constant current control function and a constant voltage control function, and is operated during normal operation. The disclosure discloses a configuration in which a constant current operation is performed in which a constant current is supplied to a plurality of light emitting diode lamps in a light emitting diode unit when the light emitting diode lamp is not out of order.

JP 2014-120444 A

  However, according to the study of the present inventor, in the configuration of Patent Document 1, when the lighting switch is switched from the off state to the on state, the rush current is applied to the light emitting diode before the suppression by the feedback control of the driving current is started. There is room for improvement because it is considered that the light may flow and the life of the light emitting diode may be shortened.

  The present invention has been made in view of the above, and an object of the present invention is to provide a light lighting control circuit capable of suppressing a reduction in the life of a light emitting diode.

In order to achieve the above object, the present invention provides that a constant current circuit including a control circuit and a booster circuit, and that a lighting switch for turning on and off a light emitting diode as a light source of a light switch from an off state to an on state. A light-on control circuit, comprising: a switch-on detection circuit for detecting the light-on switch, wherein the control circuit detects that the lighting switch has been switched from the off state to the on state by the switch-on detection circuit. by stopping the boosting operation of the booster circuit, and lower than the forward voltage value of the output voltage value of the boosting circuit and the light emitting diode, the output voltage value of the boosting circuit the forward voltage of the light emitting diode A low-voltage detection circuit that detects that the voltage has become lower than a predetermined value. After it is detected that the output voltage value of the path becomes lower than the forward voltage value of the light emitting diode, the output voltage of the booster circuit is adjusted so that the current value flowing through the light emitting diode becomes a target value. Controlling the value is a first aspect.

According to the present invention, in addition to the first aspect, the switch-on detection circuit has a first terminal and a second terminal connected between the booster circuit and the light emitting diode, and is added to a third terminal. A switching element for controlling a current flowing between the first terminal and the second terminal with a voltage or a current, and a resistor connected in parallel between the first terminal and the second terminal of the switching element A circuit comprising an element, a difference detection circuit for detecting a difference value between the output voltage value of the booster circuit and a voltage value on the upstream side of the lighting switch corresponding to the forward voltage value of the light emitting diode, Wherein the control circuit is configured such that when the lighting switch is switched from the off state to the on state, the difference detection circuit outputs the output voltage value of the booster circuit and the upstream side of the lighting switch. Stopping the boosting operation of the boosting circuit in response to detecting that the difference value from the voltage value is equal to or greater than a predetermined voltage value, thereby changing the output voltage value of the boosting circuit to the light emitting diode. The second aspect is to make the forward voltage value lower than the above described forward voltage value.

According to the present invention, in addition to the first aspect, the switch-on detection circuit has a first terminal and a second terminal connected between the booster circuit and the light emitting diode, and is added to a third terminal. A switching element for controlling a current flowing between the first terminal and the second terminal with a voltage or a current, and a resistor connected in parallel between the first terminal and the second terminal of the switching element Element, and a terminal voltage detection circuit that detects a voltage value on the upstream side of the lighting switch as a terminal voltage value, wherein the control circuit switches the lighting switch from the off state to the on state. When the voltage is switched, the boosting operation of the booster circuit is stopped in response to the terminal voltage detecting circuit detecting that the terminal voltage value has become equal to or higher than a predetermined voltage value, whereby the boosting is performed. That the output voltage value of the circuit lower than the forward voltage of the light emitting diode and the third aspect.

The present invention, in addition to any one of the first to third aspects, further comprises a discharging circuit for discharging the output voltage of the boosting circuit when the control circuit stops the boosting operation of the boosting circuit. Phase 4 is assumed.

  According to the light lighting control circuit according to the first aspect of the present invention, the control circuit performs the boosting operation of the boosting circuit by the switch-on detecting circuit detecting that the lighting switch has been switched from the off state to the on state. By stopping the operation, the output voltage value of the booster circuit is made lower than the forward voltage value of the light emitting diode. Therefore, when the lighting switch is switched from the off state to the on state, the drive current is suppressed by feedback control. It is possible to prevent the inrush current from flowing to the light emitting diode before the life of the light emitting diode is shortened.

According to the light lighting control circuit according to the first aspect of the present invention, the control circuit detects that the output voltage value of the booster circuit has become lower than the forward voltage value of the light emitting diode by the low voltage detection circuit. After that, since the output voltage value of the booster circuit is controlled so that the current value flowing through the light emitting diode becomes a target value, after the lighting switch is switched from the off state to the on state, the power saving light emitting diode is turned off. The light used as the light source can be turned on with a long life.

According to the light lighting control circuit according to the second aspect of the present invention, when the lighting switch is switched from the off state to the on state, the difference detection circuit detects the output voltage value of the booster circuit and the upstream of the lighting switch. The boosting circuit stops the boosting operation in response to detecting that the difference value from the voltage value on the side of the light-emitting diode is equal to or greater than the predetermined voltage value, thereby changing the output voltage value of the boosting circuit to the forward voltage value of the light emitting diode. When the lighting switch is switched from the off state to the on state, an inrush current flows to the light emitting diode before the drive current is suppressed by the feedback control, and the life of the light emitting diode is reduced. This can be reliably suppressed with a simple configuration.

According to the light lighting control circuit according to the third aspect of the present invention, when the lighting switch switches from the OFF state to the ON state, the terminal voltage value of the terminal voltage detection circuit becomes equal to or higher than the predetermined voltage value when the lighting switch is switched from the OFF state to the ON state. By stopping the boosting operation of the boosting circuit in response to detecting that the output voltage value of the boosting circuit is lower than the forward voltage value of the light emitting diode, the lighting switch is turned off. When the switching to the ON state is performed, the rush current flows to the light emitting diode before the suppression by the feedback control of the drive current is started, and the reduction in the life of the light emitting diode can be reliably suppressed with a simpler configuration. .

According to the light lighting control circuit according to the fourth aspect of the present invention, since the control circuit further includes a discharge circuit that discharges an output voltage of the booster circuit when the booster circuit stops boosting operation, the booster circuit Output voltage value faster and more reliably than the forward voltage value of light emitting diodes

FIG. 1 is a block diagram illustrating a configuration of a light lighting control circuit according to an embodiment of the present invention. FIG. 2 is a timing chart for explaining the operation of the light lighting control circuit in the present embodiment. FIG. 3 is a block diagram illustrating a configuration of a light lighting control circuit according to a modification of the present embodiment. FIG. 4 is a timing chart for explaining the operation of the light lighting control circuit in the present modification.

  Hereinafter, a light lighting control circuit according to an embodiment of the present invention will be described in detail with reference to the drawings as appropriate.

  First, a configuration of a light lighting control circuit according to the present embodiment will be described with reference to FIG.

[Constitution]
FIG. 1 is a block diagram illustrating a configuration of a light lighting control circuit according to the present embodiment.

  As shown in FIG. 1, a light lighting control circuit 1 in the present embodiment is an electric circuit which is typically mounted on a vehicle such as a motorcycle and forms a part of an electronic control device (not shown). And a plurality of light emitting diodes D connected in series so as to constitute a light source of an LED (Light Emitting Diode) light L. The light lighting control circuit 1 includes a constant current circuit 2, a switch-on detection circuit 3, a low voltage detection circuit 4, a latch circuit 5, and a discharge circuit 6 as main components.

  The constant current circuit 2 is an electric circuit that supplies a plurality of light emitting diodes D with an LED driving current that is a forward current of a constant current.

  Specifically, the constant current circuit 2 includes a booster circuit 2a, a latch circuit 2b, and a control circuit 2c.

  The booster circuit 2a forms a part of the switch-on detection circuit 3 by executing a boosting operation of boosting a power supply voltage from a battery (not shown) according to a control signal from the control circuit 2c and outputting the boosted voltage. This is an electric circuit that can supply an LED driving current, which is a forward current, to a plurality of light emitting diodes D via a field effect transistor (FET) element Q1, a resistance element R2, and an external switch SW in this order. The booster circuit 2a is basically operated to make the input voltage (hereinafter, referred to as terminal voltage) to the plurality of light emitting diodes D equal to or higher than the forward voltage while the LED light L is lit. The power supply voltage from the battery is typically not supplied individually to the booster circuit 2a, but is supplied via the power supply voltage from the battery supplied to the electronic control unit. The external switch SW is attached to an instrument panel, a handle, or the like between the light lighting control circuit 1 and the plurality of light emitting diodes D and outside the light lighting control circuit 1, typically outside the electronic control device. Is what it is.

  The latch circuit 2b performs a latch operation and a release operation thereof, applies an output voltage corresponding to the latch operation to the gate terminal G of the FET element Q1, and turns it on / off. , An electric circuit that can be operated by inputting a release signal from the low voltage detection circuit 4. Typically, when there is no input of a release signal from the low voltage detection circuit 4, the latch circuit 2b outputs a high level signal or a low level control signal from the control circuit 2c. The level or low level voltage is continuously output and applied to the gate terminal G of the FET element Q1. After that, even if the control signal input from the control circuit 2c is switched to low level or high level, it is output. The voltage level applied to the gate terminal G of the FET element Q1 is not switched. The latch circuit 2b releases the latch operation when a release signal is input from the low voltage detection circuit 4, and at that time, the control signal input from the control circuit 2c has already been switched to the low level or the high level. When the switching is performed or after that, a low-level or high-level voltage is output and applied to the gate terminal G of the FET element Q1.

  The control circuit 2c is an electric circuit that performs feedback control on the LED drive current supplied to the plurality of light emitting diodes D via the booster circuit 2a so as to match the constant current value. The control circuit 2c outputs a high-level or low-level control signal to the boosting circuit 2a under the input of the enable signal from the latch circuit 5 to control the boosting operation, and outputs a high-level signal to the latch circuit 2b. Alternatively, it is an electric circuit capable of outputting a low-level control signal and controlling the on / off operation of the FET element Q1 via the latch circuit 2b, and has an enable terminal 2d to which an enable signal is input. Typically, only when the enable signal input to the enable terminal 2d is at a high level, the control circuit 2c allows the control operation including its output operation and allows each of the control signals to be supplied to the booster circuit 2a and the latch. The circuit 2b can be output. Note that the control circuit 2c may be integrated.

  The switch-on detection circuit 3 calculates a difference value between the boosted voltage output from the booster circuit 2a and the terminal voltage when the external switch SW for turning on and off the plurality of light emitting diodes D is switched from the off state to the on state. Is an electric circuit for detecting

  Specifically, the switch-on detection circuit 3 includes an electric circuit including a P-type FET element Q1 and a resistance element R1, and a difference detection circuit 3a.

  In the electric circuit including the FET element Q1 and the resistance element R1, the FET element Q1 is connected between the booster circuit 2a and the plurality of light emitting diodes D, that is, the external switch SW. The second terminal is connected to the source terminal S by performing on / off operation in accordance with the voltage level applied to the gate terminal G (third terminal) from the control circuit 2c via the latch circuit 2b. The resistor R1 is connected in parallel between the source terminal S and the drain terminal D of the FET element Q1, and the light emitting diode D1 is turned off when the FET Q1 is turned off. Has a resistance value large enough to prevent overcurrent from flowing. In the switch-on detection circuit 3, the current flowing between the source terminal S and the drain terminal D is controlled by using the FET element Q1, but a switching element such as a bipolar transistor element other than the FET element is used. Thereby, the current flowing between the collector terminal and the emitter terminal may be controlled.

  The difference detection circuit 3a is an electric circuit that detects a difference value between the boosted voltage output from the booster circuit 2a and the voltage on the upstream side of the external switch SW corresponding to the terminal voltage. Typically, when the difference value between the boosted voltage output from the booster circuit 2a and the voltage on the upstream side of the external switch SW corresponding to the terminal voltage is smaller than a predetermined difference value, the difference detection circuit 3a A level detection signal is output to the latch circuit 5, and a high level detection signal is output to the latch circuit 5 when the difference value is equal to or greater than a predetermined difference value. Note that a terminal voltage detection circuit for detecting the terminal voltage value itself may be provided instead of the difference detection circuit 3a. In such a case, the terminal voltage detection circuit outputs a low-level detection signal to the latch circuit 5 when the value of the terminal voltage is less than the predetermined threshold, and when the value of the terminal voltage is equal to or more than the predetermined threshold, The high-level detection signal is output to the latch circuit 5.

  The low voltage detection circuit 4 detects that the boosted voltage output from the booster circuit 2a is lower than the low voltage detection voltage, and thus the boosted voltage output from the booster circuit 2a is lower than the low voltage detection voltage. When the voltage is lowered, the electric circuit outputs a release signal to release the latch operation to the latch circuits 2b and 5 respectively. Here, the low voltage detection voltage is set in advance as a predetermined voltage value lower than the forward voltage value of the terminal voltage.

  The latch circuit 5 executes a latch operation and release thereof and outputs an enable signal corresponding to the latch operation to the control circuit 2c. The release of the latch operation is performed by input of a release signal from the low voltage detection circuit 4. A possible electric circuit. Typically, when there is no input of the release signal from the low voltage detection circuit 4 and the high level or low level detection signal is input from the difference detection circuit 3a during the period when there is no input of the release signal from the low voltage detection circuit 4, A low-level or high-level voltage enable signal is continuously output and is continuously input to the enable terminal 2d of the control circuit 2c. During this period, the detection signal input from the difference detection circuit 3a is at a low level. Alternatively, the voltage level of the enable signal does not switch even if the level is switched to the high level. The latch circuit 5 releases the latch operation when a release signal is input from the low-voltage detection circuit 4, and at this time, the detection signal input from the difference detection circuit 3a becomes low level or high level. When the switching has already been performed or after that, the voltage level of the enable signal is switched, and a high-level or low-level enable signal is output and input to the enable terminal 2d of the control circuit 2c.

  The discharging circuit 6 is an electric circuit that discharges the boosted voltage output from the boosting circuit 2a when the control circuit 2c stops the boosting operation of the boosting circuit 2a. The trigger that the discharge circuit 6 starts the discharge operation is, for example, when the difference detection circuit 3a outputs a high-level detection signal to the latch circuit 5 when the difference value is equal to or greater than the predetermined difference value. It may be given. The trigger for the discharge circuit 6 to end the discharging operation is given from the low voltage detection circuit 4 at the timing when the low voltage detection circuit 4 outputs a release signal to the latch circuits 2b and 5 respectively. You may.

[motion]
Next, the operation of the light lighting control circuit 1 in the present embodiment will be described with reference to FIG.

  FIG. 2 is a timing chart for explaining the operation of the light lighting control circuit 1 in the present embodiment.

  In the light lighting control circuit 1, as shown in FIG. 2A, when the external switch (lighting switch) SW is switched from the ON state to the OFF state at time T = T1, no current flows through the LED light L. As shown in FIG. 2B, the value of the LED drive current (LED current) becomes zero, and as shown in FIG. 2C, the boosted voltage which has been the forward voltage level increases. Note that the control circuit 2c monitors the value of the LED drive current from the potential difference between the upstream side and the downstream side of the resistance element R2.

  Next, at time T = T2, when the control circuit 2c detects that the boosted voltage has become equal to or higher than the preset overvoltage detection voltage, as shown in FIGS. 2 (g), (h) and (i), The control circuit 2c stops the boosting operation by controlling the boosting circuit 2a, and switches the control signal output to the latch circuit 2b (latch circuit A) from a high level to a low level. 2b (latch circuit A) switches the FET element Q1 from the on state to the off state by outputting a low-level voltage and applying it to the gate terminal G of the FET element Q1. At the same time, the latch circuit 2b (latch circuit A) keeps outputting a low-level voltage by applying the latching operation, continuously applying the low-level voltage to the gate terminal G of the FET element Q1, and turning off the FET element Q1. maintain. At this time, the enable signal input from the latch circuit 5 to the control circuit 2c is at a high (enable) level. Note that the value of the boosted voltage monitored by the control circuit 2c is the value of the voltage on the downstream side of the booster circuit 2a.

  As a result, as shown in FIGS. 2C and 2D, the boosted voltage gradually decreases as time passes by being discharged through the control circuit 2c and other accessory circuits, and the terminal voltage is accordingly reduced. Also gradually decreases.

  Next, at time T = T3, when the control circuit 2c detects that the boosted voltage has fallen below the preset overvoltage detection release voltage, as shown in FIGS. 2 (g), (h) and (i), The control circuit 2c raises the boosted voltage by controlling the booster circuit 2a, and also keeps the FET element Q1 in an off state to flow the current of the boosted voltage through the resistance element R1. At this time, the enable signal input from the latch circuit 5 to the control circuit 2c is at a high (enable) level. Then, in this case, if the external switch SW remains off, the boosted voltage rises to the overvoltage detection voltage as in the case of the time T = T2, so that the operation at the time T = T2 (boosting stop) The operation, the FET element OFF state switching operation, and the FET element OFF state maintaining operation) and the operation at time T = T3 (the boosting operation and the FET element OFF state maintaining operation) are repeatedly executed.

  Next, at time T = T4, as shown in FIG. 2G, when the external switch SW is switched from the off state to the on state while the boosting stop operation and the boosting operation are repeatedly performed. 2 (c) and 2 (d), while the terminal voltage sharply decreases to near the voltage Vf which is the forward voltage of the light emitting diode D, the boosted voltage increases with time as time elapses. Since a gradual decrease transition as shown between T = T2 and time T = T3 is shown, a difference value occurs between the terminal voltage and the boosted voltage. Therefore, as shown in FIGS. 2 (e), (j), (k) and (m), the difference detection circuit 3a determines that the difference value between the terminal voltage and the boosted voltage is equal to or larger than the predetermined difference value. When the detection is detected, the difference detection circuit 3a outputs a high-level detection signal to the latch circuit 5 (latch circuit B), thereby enabling the low level to instruct the stop of the control operation including the output operation of the control circuit 2c. A signal is output from the latch circuit 5 (latch circuit B) to the enable terminal 2d of the control circuit 2c, and in response, the control circuit 2c stops the control operation including the output operation. At this time, the discharging circuit 6 starts a discharging operation of discharging the boosted voltage that is being reduced in voltage after being boosted by the boosting circuit 2a. When a terminal voltage detection circuit is provided instead of the difference detection circuit 3a, the terminal voltage detection circuit outputs a high-level detection signal when detecting that the value of the terminal voltage has exceeded a predetermined threshold value. This is output to the latch circuit 5.

  Next, at time T = T5, as shown in FIGS. 2C and 2D, the difference value between the terminal voltage and the boosted voltage is a predetermined difference value (in the figure, the predetermined difference value is assumed to be zero). When the difference becomes less than the predetermined value, the difference detection circuit 3a detects that the difference value between the terminal voltage and the boosted voltage is less than the predetermined difference value, and outputs a low-level detection signal to the latch circuit 5. The circuit 5 (latch circuit B) continuously outputs a low-level enable signal for instructing stop of the control operation including the output operation to the enable terminal 2d of the control circuit 2c, and the control circuit 2c responds to the low-level enable signal. The state where the control operation including the operation is stopped is maintained. When a terminal voltage detection circuit is provided instead of the difference detection circuit 3a, the terminal voltage detection circuit outputs a low-level detection signal when detecting that the value of the terminal voltage has become less than a predetermined threshold value. 5, and the latch circuit 5 continues to output a low-level enable signal instructing stop of the control operation including the output operation to the enable terminal 2d of the control circuit 2c.

  Then, at time T = T6, as shown in FIG. 2C, when the boosted voltage becomes equal to or lower than the preset low-voltage detection voltage, as shown in FIG. Then, it detects that the boosted voltage is equal to or lower than the low voltage detection voltage, and outputs a release signal to each of the latch circuits 2b and 5 to release their latch operations. When the latch circuit 5 releases the latch operation, a high-level enable signal instructing execution of a control operation including an output operation is output to the enable terminal 2d of the control circuit 2c. In response to this, the boosting operation of the booster circuit 2a is started, and the FET element Q1 is switched from the off state to the on state. At the same time, the discharging circuit 6 stops the discharging operation. Thereafter, the control circuit 2c controls the output voltage of the booster circuit 2a to start the energization control for feedback-controlling the current flowing through the light emitting diode D to the target current value that is a constant current value.

  As is apparent from the above description, according to the light lighting control circuit 1 of the present embodiment, when the external switch SW is switched from the off state to the on state, the switch-on detection circuit 3 sets the switch-on detection circuit 3 to the booster circuit. By detecting that the difference value between the output voltage value of the booster circuit 2a and the forward voltage value of the light emitting diode D is equal to or higher than a predetermined voltage value, the boosting operation of the booster circuit 2a is stopped. Since the voltage value is lower than the forward voltage value of the light emitting diode D, when the external switch SW is switched from the off state to the on state, the rush current is reduced before the drive current is suppressed by the feedback control. D, and the life of the light emitting diode D is prevented from being shortened. In addition, typically, an external switch SW for turning on and off the light emitting diode D is provided between the light lighting control circuit 1 and the plurality of light emitting diodes D and outside the light lighting control circuit 1. In such a case, the external switch SW can interrupt the power from the battery (not shown) supplied to the light lighting control circuit 1, eliminating the need to provide a power line dedicated to the light emitting diode D. The size of the entire system can be reduced.

  Further, according to the light lighting control circuit 1 of the present embodiment, the control circuit 2c detects that the output voltage value of the booster circuit 2a has become lower than the forward voltage value of the light emitting diode D by the low voltage detection circuit 4. After that, since the output voltage value of the booster circuit 2a is controlled so that the current value flowing through the light emitting diode D becomes the target value, after the lighting switch is switched from the off state to the on state, the power consumption is reduced. The light L using a light emitting diode as a light source can be turned on with a long life.

  Further, according to the light lighting control circuit 1 of the present embodiment, when the lighting switch SW is switched from the off state to the on state, the control circuit 2c determines whether the difference detection circuit 3a has the output voltage value of the booster circuit 2a and the lighting switch. The boosting operation of the boosting circuit 2a is stopped in response to detecting that the difference value between the voltage value on the upstream side of the SW and the predetermined voltage value is equal to or more than the predetermined value. D is lower than the forward voltage value of D, so that when the lighting switch SW is switched from the off state to the on state, an inrush current flows through the light emitting diode D before the suppression by the feedback control of the driving current is started. In addition, a reduction in the life of the light emitting diode D can be reliably suppressed with a simple configuration.

  Here, the detection of the switching of the lighting switch SW from the OFF state to the ON state is performed by detecting the difference between the output voltage value of the booster circuit 2a and the voltage value of the lighting switch SW on the upstream side of the lighting switch SW. This may be performed by using a terminal voltage value, which is the voltage value of the above, and detecting that the voltage value becomes equal to or higher than a predetermined voltage value. Thereby, when the lighting switch SW is switched from the off state to the on state, the rush current flows through the light emitting diode D before the suppression by the feedback control of the driving current is performed, and the life of the light emitting diode D is reduced. With a simpler configuration, it can be surely suppressed.

  According to the light lighting control circuit 1 of the present embodiment, the control circuit 2c further includes the discharge circuit 6 that discharges the output voltage of the booster circuit 2a when the booster circuit 2a stops the boost operation. The output voltage value of the booster circuit 2a can be reduced more quickly and reliably than the forward voltage value of the light emitting diode D.

(Modification)
Next, with reference to FIGS. 3 and 4, the configuration and operation of a light lighting control circuit according to a modification of the present embodiment will be described.

[Constitution]
FIG. 3 is a block diagram illustrating a configuration of a light lighting control circuit according to the present modification.

  As shown in FIG. 3, the light lighting control circuit 1 ′ according to the present modification has the same configuration as that of the above-described light lighting control circuit 1 according to the present embodiment except that it does not include the discharge circuit 6. I have. Therefore, in the following, description of the configuration of the light lighting control circuit 1 'in the present modified example will be omitted, and its operation will be described while focusing on differences from the above-described embodiment.

[motion]
FIG. 4 is a timing chart for explaining the operation of the light lighting control circuit 1 'in the present modification.

  First, the timing at which a difference from the operation in the present embodiment described above appears is time T = T4. That is, at time T = T4, as shown in FIGS. 4 (e), (j), (k), and (m), the difference detection circuit 3a determines that the difference between the terminal voltage and the boosted voltage is equal to the predetermined difference. When it is detected that the value has exceeded the threshold value, a high-level detection signal is output to the latch circuit 5 (latch circuit B), whereby a low-level enable signal for instructing the control circuit 2c to stop the control is output to the latch circuit. 5 (latch circuit B) to output to the enable terminal 2d of the control circuit 2c, and the control circuit 2c stops the control operation including the output operation in response to the output from the enable terminal 2d in the same manner as in the present embodiment. However, in this modification, since the discharging circuit is not provided, the boosted voltage output from the boosting circuit 2a cannot be discharged by operating the discharging circuit, and as shown in FIG. The voltage is Over time, gradually it will be reduced by being discharged through the control circuit 2c, and other associated circuitry.

  In the present modification, at time T = T6, as shown in FIG. 4 (l), the low voltage detection circuit 4 detects that the boosted voltage is equal to or lower than the low voltage detection voltage, and the latch circuit 2b Outputting release signals to the latch circuits 5 to release their latch operations is the same as in the present embodiment, however, in this modification, the discharge circuit is not provided since the discharge circuit is not provided. You don't have to.

  As is clear from the above description, according to the light lighting control circuit 1 'in the present modification, even in a simple configuration in which the discharge circuit 6 is omitted, the control circuit 2c turns on the external switch SW from the off state to the on state. When the state is switched to the state, the switch-on detection circuit 3 detects that the difference value between the output voltage value of the booster circuit 2a and the forward voltage value of the light emitting diode D is equal to or greater than a predetermined voltage value, and thereby the booster circuit By stopping the boosting operation of 2a, the output voltage value of the boosting circuit 2a can be made lower than the forward voltage value of the light emitting diode D, so that the drive is performed when the external switch SW is switched from the off state to the on state. It is possible to prevent the inrush current from flowing to the light emitting diode D before the current feedback control is performed, thereby reducing the life of the light emitting diode D. Can.

  Note that the present invention is not limited to the above-described embodiment in terms of the type, shape, arrangement, number, and the like of the members, and the gist of the invention is that the components are appropriately replaced with those having equivalent functions and effects. Of course, it can be changed as appropriate without departing from the scope.

  INDUSTRIAL APPLICABILITY As described above, the present invention can provide a light lighting control circuit capable of suppressing a reduction in the life of a light emitting diode, and a light system for a vehicle such as a motorcycle due to its general-purpose universal nature. It is expected that it can be widely applied to

1, 1 ': light lighting control circuit 2: constant current circuit 2a: boost circuit 2b, 5: latch circuit 2c: control circuit 2d: enable terminal 3: switch-on detection circuit 3a: difference detection circuit 4: low voltage detection circuit 5 ... Latch circuit 6 ... Discharge circuit D ... Light emitting diode L ... Light Q1 ... FET element R1, R2 ... Resistor element SW ... External switch

Claims (4)

A constant current circuit comprising a control circuit and a booster circuit;
A switch-on detection circuit that detects that a lighting switch that turns on and off a light emitting diode that is a light source of a light has been switched from an off state to an on state,
In the light lighting control circuit having
Wherein the control circuit, by the lighting switch is the switch-on detecting circuit detects that the switched from the OFF state to the ON state, by stopping the boosting operation of the booster circuit, the output of the booster circuit A voltage value lower than a forward voltage value of the light emitting diode ,
A low-voltage detection circuit that detects that the output voltage value of the booster circuit is lower than the forward voltage value of the light-emitting diode,
The control circuit is configured such that after the low voltage detection circuit detects that the output voltage value of the booster circuit is lower than the forward voltage value of the light emitting diode, the current value flowing through the light emitting diode is A light lighting control circuit , wherein the output voltage value of the booster circuit is controlled so as to be a target value . The switch-on detection circuit,
A first terminal and a second terminal are connected between the booster circuit and the light emitting diode, and a current flowing between the first terminal and the second terminal by a voltage or current applied to a third terminal A circuit comprising: a switching element that is controlled, and a resistance element connected in parallel between the first terminal and the second terminal of the switching element;
A difference detection circuit that detects a difference value between the output voltage value of the booster circuit and a voltage value on the upstream side of the lighting switch corresponding to the forward voltage value of the light emitting diode;
With
The control circuit is configured such that, when the lighting switch is switched from the off state to the on state, the difference detection circuit sets the output voltage value of the booster circuit and the voltage value on the upstream side of the lighting switch. By stopping the boosting operation of the boosting circuit in response to detecting that the difference value has become equal to or greater than the predetermined voltage value, the output voltage value of the boosting circuit is changed to the forward voltage value of the light emitting diode. The light lighting control circuit according to claim 1 , wherein the light emission control circuit is lower than the light emission control circuit. The switch-on detection circuit,
A first terminal and a second terminal are connected between the booster circuit and the light emitting diode, and a current flowing between the first terminal and the second terminal by a voltage or current applied to a third terminal A circuit comprising: a switching element that is controlled, and a resistance element connected in parallel between the first terminal and the second terminal of the switching element;
A terminal voltage detection circuit that detects a voltage value on the upstream side of the lighting switch as a terminal voltage value,
With
The control circuit, when the lighting switch is switched from the off state to the on state, in response to detecting that the terminal voltage value is equal to or more than a predetermined voltage value in the terminal voltage detection circuit, 2. The light lighting control circuit according to claim 1 , wherein the step-up operation of the step-up circuit is stopped so that the output voltage value of the step-up circuit is lower than the forward voltage value of the light emitting diode. Light lighting control circuit according to any one of claims 1 to 3, the step-up operation further comprises a discharge circuit for discharging the output voltage of the boosting circuit when the stop of the control circuit the booster circuit.

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