JP6491414B2 - Vehicular lamp driving device and vehicular lamp driving method - Google Patents

Description

  The present invention relates to a vehicle lamp driving device and a vehicle lamp driving method.

  Generally, an LED (Light Emission Diode) lamp can be driven at a low voltage and has a longer life, lower power consumption, faster reaction speed, and higher impact resistance than a filament lamp (bulb lamp). Therefore, the size and weight can be reduced. For this reason, an LED lamp can be used suitably for a headlamp etc. of vehicles, for example. In general, a vehicle headlamp includes a high beam lamp and a low beam lamp. For this reason, a driving device for driving a headlamp of a vehicle includes a driving circuit for driving a high beam lamp and a driving circuit for driving a low beam lamp.

Japanese Patent No. 5250163 JP 2012-157099 A JP 2012-44806 A JP 2011-223800 A

  According to the above-described prior art, since the drive circuit for driving the high beam lamp and the drive circuit for driving the low beam lamp are separately provided, the number of parts increases and the apparatus configuration becomes complicated. . For this reason, cost increases.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a vehicle lamp driving device and a vehicle lamp driving method capable of reducing the number of parts and simplifying the device configuration.

In order to solve the above problems, a vehicle lamp driving device according to an aspect of the present invention is for a vehicle that drives a plurality of lamps connected in series between a first terminal and a second terminal to which a DC voltage is applied. A lamp driving device, connected in parallel with a part of a current path of the plurality of lamps, and a switch for switching a lighting state of the first lamp having the current path between lighting and extinguishing; A current path in which the plurality of lamps and a switching element are connected in series between the first terminal and the second terminal, and the current flowing through the circuit network including the plurality of lamps and the switch is limited. A current limiting circuit, an inductive element connected in series with the current path of the switch, and when the switch switches the lighting state of the first lamp to off, and the switching element is turned off. If the, a rectifying element for regenerating the current emitted from the inductive element, and a said rectifying element connected in parallel to said plurality of lamps and front Symbol inductive element, said plurality of Among the lamps, a second lamp that is a lamp other than the lamp connected in parallel with the switch maintains the lighting in response to the application of the DC voltage regardless of switching of the switch, and the inductive element Has a configuration of a vehicular lamp driving device that suppresses an inrush current that flows into one of the plurality of lamps, which is generated when the switch is switched.

A vehicle lamp driving method according to an aspect of the present invention is a vehicle lamp driving method for driving a plurality of lamps connected in series between a first terminal and a second terminal to which a DC voltage is applied. The switch connected in parallel with a part of the current paths among the plurality of lamps turns on and off the first lamp having the current path connected in parallel with the switches among the plurality of lamps. Switching to any one of the above, a current path in which the plurality of lamps and switching elements provided between the first terminal and the second terminal are connected in series, and the plurality of lamps and the switch Limiting the current flowing through the network; an inductive element connected in series with the current path of the switch suppresses inrush current; and the switch switches off the lighting state of the first lamp. If instead, in the case where and the switching element is turned off, a rectifying element, the plurality of lamps and said rectifying element connected in parallel with the previous SL inductive element, from the inductive element Regenerating the discharged current, and in the step of switching the lighting state, a second lamp that is a lamp other than the lamp connected in parallel with the switch among the plurality of lamps is Regardless of switching, the lighting is maintained in response to the application of the DC voltage, and the inductive element is a current generated when the switch is switched, and flows into one of the plurality of lamps. It has the structure of the vehicle lamp drive method which suppresses inrush current.

  According to the present invention, the number of parts can be reduced and the apparatus configuration can be simplified.

It is a circuit diagram showing an example of composition of a vehicular lamp drive device by an embodiment of the present invention. It is a wave form diagram for explaining pressure | voltage rise operation | movement of the lamp drive device for vehicles by embodiment of this invention. It is a wave form diagram for demonstrating detailed operation | movement of the lamp drive device for vehicles by embodiment of this invention, and is a figure for demonstrating generation | occurrence | production of inrush current. It is a wave form diagram for demonstrating detailed operation | movement of the lamp drive device for vehicles by embodiment of this invention, and is a figure for demonstrating regeneration of inrush current. It is a circuit diagram which shows the modification of the lamp drive device for vehicles by embodiment of this invention, (A) shows a 1st modification, (B) is a figure which shows a 2nd modification.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
(Description of configuration)
FIG. 1 shows a configuration example of a vehicle lamp driving device 1 according to an embodiment of the present invention.
The vehicle lamp driving device 1 according to the present embodiment drives a first lamp ED1 and a second lamp ED2 (a plurality of lamps) connected in series between a terminal T1 to which a DC voltage Vout is applied and a terminal T2. Battery BA, coils L1, L2 (inductive elements), n-type MOS transistors M1, M2 (switching elements), resistors R1, R2, R3 and shunt resistors R4 (current detecting elements), diodes D1, D2 (Rectifier element), capacitors C1 and C2, switch SW, and control unit 100 are provided. The control unit 100 includes a boost control unit 110, a current control unit 120, an auxiliary circuit 130, and terminals TM1 to TM8. The boost control unit 110 includes a switching control unit 111, a driver 112, a voltage detection unit 113, and an overcurrent detection unit 114, and the current control unit 120 includes a switching control unit 121, a driver 122, and a peak current detection unit 123. In the present embodiment, the current control unit 120, the n-type MOS transistor M2, and the shunt resistor R4 constitute a current limiting circuit LMT that functions as a constant current circuit. In the present embodiment, the term “terminal” means a literal terminal or a concept including a simple connection point.

  Here, schematically, the coil L2, the switch SW, and the current limiting circuit LMT constitute a part of constituent elements characteristic of the present embodiment. Among these, the coil L2 is for suppressing the peak value of the inrush current that flows into the lamp when the switch SW is in the closed state. In this embodiment, the coil L2 is connected in series with the current path of the switch SW. Yes. An arbitrary inductive element can be used as the coil L2 as long as the inrush current can be suppressed. In applications where it is not necessary to suppress the inrush current, the coil L2 can be omitted. The switch SW is connected in parallel with the current path of any one of the first lamp ED1 and the second lamp ED2 (plural lamps), and switches the lighting state of the lamp having the current path. In the present embodiment, the switch SW is connected in parallel with the current path of the first lamp ED1, and switches the lighting state of the first lamp ED1. However, the switch SW may be connected in parallel with the second lamp ED2. In the present embodiment, any switch such as an n-type MOS transistor or a mechanical switch may be used as the switch SW as long as the lighting state of the lamp can be switched in response to an operation by a vehicle driver or the like. it can. The current limiting circuit LMT has a current path connected in series with the first lamp ED1 and the second lamp ED2 between the terminal T1 and the terminal T2, and includes the first lamp ED1, the second lamp ED2, and the switch SW. This is for limiting the current flowing through the circuit network consisting of: and functions as a constant current circuit.

  This will be described in detail. In FIG. 1, the negative electrode of the battery BA is connected to the vehicle body SH of the vehicle on which the vehicle lamp driving device 1 is mounted, and one end of the boosting coil L1 is connected to the positive electrode of the battery BA. The other end of the coil L1 is connected to the drain of an n-type MOS transistor M1 for driving the coil L1. The gate of the n-type MOS transistor M1 is connected to the terminal TM2 of the control unit 100, and a control signal SM1 for driving the n-type MOS transistor M1 is supplied from the control unit 100.

  A resistor R1 for detecting a current flowing through the nMOS transistor M1 is connected between the source of the n-type MOS transistor M1 and the terminal T2 (second terminal). The terminal T2 is connected to the vehicle body SH. In the present embodiment, a terminal TM7 that is a ground terminal of the control unit 100 is connected to the terminal T2. As a result, the vehicle lamp drive device 1 operates with reference to the potential of the vehicle body SH of the vehicle.

  Further, the anode of the rectifying diode D1 is connected to the drain of the n-type MOS transistor M1, and the cathode of the diode D1 is connected to the terminal T1 (first terminal). The DC voltage Vout rectified by the diode D1 is supplied to the terminal T1. A resistor R2 and a resistor R3 for dividing and detecting the DC voltage Vout are connected in series between the terminal T1 and the terminal T2. A capacitor C1 is connected between the terminal T1 and the terminal T2.

  The coil L1, the n-type MOS transistor M1, the diode D1, and the capacitor C1 constitute a boost chopper circuit CHP. In the present embodiment, under the control of the control unit 100, the boost chopper circuit CHP boosts the DC voltage Vin supplied from the battery BA to a desired DC voltage Vout and supplies it between the terminal T1 and the terminal T2. . The capacitor C1 smoothes the DC voltage Vout output from the boost chopper circuit CHP.

  A coil L2, a high beam first lamp ED1, a low beam second lamp ED2, an n-type MOS transistor M2, and a shunt resistor R4 are connected in series between the terminal T1 and the terminal T2. Specifically, one end of the coil L2 is connected to the terminal T1, and one end (anode) of the current path of the first lamp L1 is connected to the other end of the coil L2. One end (anode) of the current path of the second lamp ED2 is connected to the other end (cathode) of the current path of the first lamp ED1. That is, the first lamp ED1 and the second lamp ED2 are connected in series between the other end of the coil L2 and one end of the current path of the current limiting circuit LMT, and the terminal T2 is connected to the other end of the current path of the current limiting circuit LMT. Has been.

  The other end (cathode) of the current path of the second lamp ED2 is connected to the drain of the n-type MOS transistor M2 for controlling the current flowing through the first lamp ED1 and the second lamp ED2 to be constant. Thus, an n-type MOS transistor M2 whose current path is connected in series with the first lamp ED1 and the second lamp ED2 is connected between the terminal T1 and the terminal T2. In the present embodiment, the current path of the current limiting circuit LMT is formed using the n-type MOS transistor M2, but the present invention is not limited to this example, and the current flowing through the first lamp ED1 and the second lamp ED2 can be adjusted. Any switching element can be used with a limit of. A shunt resistor R4 connected in series with the current path of the n-type MOS transistor M2 is connected between the terminal T1 and the terminal T2. In the present embodiment, the shunt resistor R4 is connected between the source of the n-type MOS transistor M2 and the terminal T2, and detects the current If flowing through the n-type MOS transistor M2. The current If corresponds to a current flowing through a circuit network including the first lamp ED1, the second lamp ED2, and the switch SW. As long as the current If can be detected, any current detection element such as a Hall element can be used as the shunt resistor R4. In the present embodiment, the n-type MOS transistor M2 and the shunt resistor R4 form a current path of the current limiting circuit LMT.

  In the present embodiment, as described above, the switch SW is connected in parallel with the current path of the first lamp ED1, but the switch SW is connected in series to the coil L2. When the switch SW is in an open state, a potential difference is generated between the anode and cathode of the first lamp ED1, current flows from the terminal T1 to the first lamp ED1 through the coil L2, and the first lamp ED1 is turned on. On the other hand, when the switch SW is in the closed state, the anode and the cathode of the first lamp ED1 are short-circuited. In this case, the potential difference between the anode and the cathode of the first lamp ED1 disappears and no current flows into the first lamp ED1, so the first lamp ED1 is turned off.

  The first lamp ED1 is composed of three light emitting diodes ED11, ED12, and ED13 connected in series, and the second lamp ED2 is similarly composed of three light emitting diodes ED21, ED22, and ED23 connected in series. . In the present embodiment, the switch SW is connected in parallel to the first lamp ED1 because the lighting state of the first lamp ED1 for high beam needs to be controlled by the switch SW. Two lamps ED2 may be connected in parallel. Further, the number of lamps is arbitrary, and the number of switches is also arbitrary.

  Between the output end (cathode) of the current path of the second lamp ED2 and the terminal T1, a current generated by releasing the energy stored in the coil L2 when the n-type MOS transistor M2 is turned off is generated. A flywheel diode D2 (regenerative rectifier) for regeneration is connected. Specifically, the anode of the flywheel diode D2 is connected to the output end of the current path of the second lamp ED2, that is, one end of the current path of the current limiting circuit, and the terminal T1 is connected to the cathode of the flywheel diode D2. It is connected.

  The control unit 100 includes a boost control unit 110, a current control unit 120, an auxiliary circuit unit 130, and terminals TM1 to TM8. Among them, the boost control unit 110 is for controlling the boost chopper circuit, and includes a switching control unit 111, a driver 112, a voltage detection unit 113, and an overcurrent detection unit 114. The input part of the voltage detection part 113 is connected to the connection part between resistance R2 and resistance R3 via terminal TM3. The voltage detector 113 detects the DC voltage Vout, which is the output voltage of the boost chopper circuit CHP, from the voltage obtained by dividing the DC voltage Vout by the resistors R2 and R3.

  The input part of the overcurrent detection part 114 is connected to a connection part between the n-type MOS transistor M1 and the resistor R1 via the terminal TM4. The overcurrent detector 114 detects the current flowing through the n-type MOS transistor M1 from the amount of voltage drop at the resistor R1 in order to protect the n-type MOS transistor M1 from overcurrent. Based on the current value detected by the overcurrent detection unit 114, a switching control unit 111, which will be described later, adjusts the switching timing of the n-type MOS transistor M1, thereby protecting the n-type MOS transistor M1 from overcurrent. The detection results of the voltage detection unit 113 and the overcurrent detection unit 114 are input to the switching control unit 111.

  The switching control unit 111 performs switching driving of the n-type MOS transistor M1 through the driver 112 so that the DC voltage Vout detected by the voltage detection unit 113 becomes a desired voltage. Specifically, the switching control unit 111 controls the switching of the n-type MOS transistor M1 so as to decrease the DC voltage Vout if the DC voltage Vout is equal to or higher than the specified voltage, and conversely, the DC voltage Vout is less than the specified voltage. If so, the switching of the n-type MOS transistor M1 is controlled to increase the DC voltage Vout. Further, when an overcurrent is detected by the overcurrent detection unit 114, the switching control unit 111 turns off the n-type MOS transistor M1 to protect the n-type MOS transistor M1 from the overcurrent. Here, normally, the current flowing through the n-type MOS transistor M1 has a peak value that is about twice that of the current (load current) flowing on the lamp side. For this reason, when the load current increases due to a short circuit of the lamp (load) or the like, an overcurrent may occur in the n-type MOS transistor M1. Therefore, it is necessary to monitor the current flowing through the n-type MOS transistor M1 and protect the n-type MOS transistor M1 from overcurrent. Accordingly, the switching control unit 111 turns off the n-type MOS transistor M1 and turns off the n-type MOS transistor M1 if the current value detected by the overcurrent detection unit 114 is equal to or greater than the specified current for determining the overcurrent. Protects against overcurrent. Conversely, if the current value detected by the overcurrent detection unit 114 is less than the specified current, the n-type MOS transistor is configured so that the DC voltage Vout becomes a desired specified voltage based on the detection result of the voltage detection unit 113. Control the switching of M1. The driver 112 outputs the control signal SM1 to the gate of the n-type MOS transistor M1 based on the output signal of the switching control unit 111, thereby driving the n-type MOS transistor M1 through the terminal TM2.

  The current controller 120 controls the current flowing through the first lamp ED1 and the second lamp ED2 (hereinafter referred to as lamp current) to be constant, and includes a switching controller 121, a driver 122, and a peak current detector. 123. A connection point between the n-type MOS transistor M2 and the shunt resistor R4 is connected to an input portion of the peak current detection portion 123 via a terminal TM6. The peak current detection unit 123 is for detecting the lamp current observed as the current If of the n-type MOS transistor M2, and when the peak of the lamp current exceeds a specified value, outputs a detection result to that effect. To do. The detection result of the peak current detection unit 123 is input to the switching control unit 121.

  Based on the voltage drop amount of the shunt resistor R4, which is the detection result of the shunt resistor R4 as the current detection element, the switching control unit 121 sets the n-type MOS transistor so that the current If flowing through the n-type MOS transistor M2 becomes a specified value. It controls the conduction of M2. That is, the switching control unit 121 controls the conduction of the n-type MOS transistor M2 through the driver 122 so that the lamp current does not exceed a specified value based on the detection result of the peak current detection unit 123. The driver 122 drives the n-type MOS transistor M1 through the terminal TM5 by outputting a control signal SM2 to the gate of the n-type MOS transistor M2 based on the output signal of the switching control unit 121.

  The auxiliary circuit 130 has an internal power supply function for generating an internal power supply voltage Vcc, a reference voltage generation function for generating a reference voltage required by the boost control unit 110 and the current control unit 120, and a voltage of the battery BA. An undervoltage lockout function (ULVO) for stopping the boosting operation of the boosting chopper circuit CHP in the following cases and an overheat protection function for preventing the apparatus from overheating. A capacitor C2 for stabilizing the internal power supply voltage Vcc is connected to the terminal TM8.

  The terminal TM1 is a power supply terminal of a circuit constituting the control unit 100. The positive electrode of the battery BA is connected to the terminal TM1, and the DC voltage Vin of the battery MA is supplied to the auxiliary circuit 130 via the terminal TM1. The auxiliary circuit 130 converts the DC voltage Vin of the battery BA into the internal power supply voltage Vcc by the internal power supply function, and supplies the converted voltage to a circuit constituting the control unit 100. The terminal TM7 is a ground terminal of a circuit constituting the control unit 100. The terminal TM7 is connected to the vehicle body SH via the terminal T2. Accordingly, the vehicle lamp driving device 1 operates at a voltage based on the potential of the vehicle body SH.

(Description of operation)
Next, the operation of the vehicle lamp driving device 1 according to the embodiment of the present invention will be described.
FIG. 2 is a waveform diagram for explaining the step-up operation of the vehicle lamp driving device 1.
The boost control unit 110 of the control unit 100 performs switching driving of the n-type MOS transistor M1 by the control signal SM1. Here, during the period when the control signal SM1 is at a high level, the n-type MOS transistor M1 is turned on, and the current Ia flowing through the coil L1 increases. On the contrary, during the period when the control signal SM1 is at the low level, the n-type MOS transistor M1 is turned off, and the current Ia flowing through the coil L1 falls.

  Further, since the n-type MOS transistor M1 is in an on state during a period in which the control signal SM1 is at a high level (for example, a period from time t1 to time t2 in FIG. 2), the n-type MOS transistor M1 flows through the coil L1. A current Ib corresponding to the current Ia flows. Further, since the n-type MOS transistor M1 is in an off state during a period in which the control signal SM1 is at a low level (for example, a period from time t2 to time t3 in FIG. 2), the current Ib of the n-type MOS transistor M1 is substantially zero. Become. On the other hand, since the diode D1 is in the reverse bias state during the period when the control signal SM1 is at the high level, the current Ic of the diode D1 becomes substantially zero. Further, since the diode D1 is in the forward bias state during the period when the control signal SM1 is at the low level, the current Ic corresponding to the current Ia flowing through the coil L1 flows through the diode D1.

  The capacitor C1 is charged by the current Ic flowing through the diode D1. As a result, the DC voltage Vout between the terminal T1 and the terminal T2 to which the capacitor C1 is connected gradually increases and stabilizes near the desired voltage. When the load fluctuates when the first lamp ED1 and the second lamp ED2 between the terminal T1 and the terminal T2 are turned on / off, the control unit 100 keeps the DC voltage Vout constant so that the n-type MOS transistor M1 is maintained. Are controlled in feedback to stabilize the DC voltage Vout.

  Here, when the switch SW is operated in the open state, the first lamp ED1 and the second lamp T2 are electrically connected in series between the terminal T1 and the terminal T2. In this case, the DC voltage Vout between the terminal T1 and the terminal T2 is applied to the series circuit of the first lamp ED1 and the second lamp T2, and a current Id flows through these coils through the coil L2. Therefore, both the high beam first lamp ED1 and the low beam second lamp ED2 are turned on. In the present embodiment, a state where both the first lamp ED1 for high beam and the second lamp ED2 for low beam are lit is referred to as a high beam.

  The current Id flowing through the first lamp ED1 and the second lamp ED2 forms the current If of the n-type MOS transistor M2, and the current If flows through the shunt resistor R4. The control unit 100 detects the current If (= Id) from the voltage drop amount of the shunt resistor R4 at this time, so that the current If flowing through the first lamp ED1 and the second lamp ED2 does not exceed the specified value. The conduction of the MOS transistor M2 is controlled. As a result, the current Id flowing through the first lamp ED1 and the second lamp ED2 is controlled to be substantially constant, and each of the first lamp ED1 and the second lamp ED2 is lit with a specified luminance.

  Subsequently, for example, when the driver of the vehicle operates the switch SW from the open state to the closed state, one end (anode) and the other end (cathode) of the current path of the first lamp ED1 are short-circuited via the switch SW. For this reason, the potential difference between both ends of the current path of the first lamp ED1 disappears, and the current Id does not flow into the first lamp ED1. As a result, the first lamp ED1 is turned off. On the other hand, the current Id supplied through the coil L2 is supplied to the second lamp ED2 as the current Is flowing through the switch SW. For this reason, the lighting state of the low beam second lamp ED2 is maintained even after the switch SW is closed. In this embodiment, the state where the first lamp ED1 for high beam is turned off and only the second lamp ED2 for low beam is turned on is referred to as a low beam.

Here, when the switch SW is changed from the open state to the closed state and the first lamp ED1 is turned off, an inrush current flows into the second lamp ED2.
FIG. 3 is a waveform diagram for explaining the detailed operation of the vehicular lamp driving device 1 according to the embodiment of the present invention, and is a diagram for explaining the generation of an inrush current.
In FIG. 3, the uppermost waveform indicates the waveform of the control signal SM2 supplied from the control unit 100 to the gate of the n-type MOS transistor M2.

  For example, when the driver of the vehicle operates the switch SW from the open state to the closed state, the power that has been consumed by the first lamp ED1 until then is not consumed, and is supplied as surplus power to the second lamp ED2 via the switch SW. The For this reason, when the switch SW is closed, the current Id temporarily supplied as the current Is to the second lamp ED increases. As a result, an inrush current Irush1 is generated as shown by the waveform W1 in FIG. The waveform W1 shown in this example indicates a virtual current Id when no countermeasure is taken against the inrush current Irush1, and the inrush current Irush1 in this case exceeds the allowable value ITH.

In this embodiment, as will be described next, inrush current is suppressed.
(1) Inrush current suppression by the coil L2, the n-type MOS transistor M2, and the resistor R4 In this embodiment, the coil L2 is connected in series with the switch SW between the terminal T1 and the terminal T2. For this reason, when the switch SW is switched from the open state to the closed state and the current ic flows through the switch SW, the surplus current due to the power that has been consumed by the first lamp ED1 becomes the current ic until the current ic passes through the switch SW. 2 flows into the lamp ED2.

In this case, as shown by the waveform W2 in FIG. 3, the component of the inrush current Irush2 is superposed on the current Id of the coil L2, and the current id rises instantaneously. Suppressed by L2, the peak value of the current Id is suppressed below the allowable value ITH. The inrush current Irush2 is also suppressed in the process of flowing through the n-type MOS transistor M2 and the shunt resistor R4 as the current If. As a result, inrush current exceeding the allowable value ITH does not flow into the second lamp ED2. Therefore, the second lamp ED2 can be protected from the inrush current. Further, when the switch SW is in the closed state, no current flows into the first lamp ED1, so the first lamp ED1 is not affected by the inrush current.
Here, since the current control unit 120 functions to keep the lamp current constant, this function can be expected to suppress the inrush current to some extent, but the inrush current is generated. There is a time lag until the current control unit 120 starts a control operation for maintaining the lamp current constant. For this reason, the suppression effect of the inrush current by the current control unit 120 may not be expected. In this regard, according to the present embodiment, the peak value of the inrush current is suppressed by the coil L2 when the inrush current is generated, so that the inrush current can be immediately suppressed. Therefore, the lamp current can be controlled to be constant by the current control unit 120 before the lamp current increases.

(2) Inrush current suppression by n-type MOS transistor M2 The inrush current cannot be effectively suppressed even by the above-described coil L2, and the inrush current Irush3 exceeding the allowable value ITH is not obtained as shown by the waveform W3 in FIG. In such a situation, as described below, the n-type MOS transistor M2 is controlled to be turned off under the control of the control unit 100, and the inrush current is returned to the terminal T1 as a regenerative current through the flywheel diode D2. .

FIG. 4 is a waveform diagram for explaining the detailed operation of the vehicle lamp drive device 1 according to the embodiment of the present invention, and is a diagram for explaining the regeneration of the inrush current.
In FIG. 4, when the n-type MOS transistor M2 is turned on at time t11, the current Id flowing through the coil L2 increases, and when the n-type MOS transistor M2 is turned off at time t12, the current Id flowing through the coil L2 decreases. Here, at time t12 when the n-type MOS transistor M2 is turned off, for example, when the switch SW is switched from the open state to the closed state by the vehicle driver, an inrush current Irush exceeding the allowable value ITH is generated. As a result, the current If flowing through the n-type MOS transistor M2 increases.

  In this embodiment, in FIG. 4, when the inrush current Irush exceeds the allowable value ITH at time t12a and the current If reaches the predetermined value ITF at time t12a, the control unit 100 controls the n-type MOS transistor M2 to be in an off state. To do. As a result, the current Is flowing into the second lamp ED2 through the switch SW becomes the current Ie and is returned to the terminal T1 through the flywheel diode D2. In this case, when attention is paid to the flow of current, a closed loop of “terminal T1, coil L2, switch SW, second lamp ED2, flywheel diode D2, and terminal T1” is formed.

  The energy due to the inrush current Irush is consumed in the process of circulating in the closed loop, thereby suppressing the inrush current. Accordingly, even if there is a situation where the inrush current Irush cannot be sufficiently suppressed by the coil L2 at the initial stage when the inrush current Irush is generated, the first lamp ED1 and the first lamp ED1 are controlled by controlling the n-type MOS transistor M2 to be turned off. In addition to the second lamp ED2, the n-type MOS transistor M2 can be protected from the inrush current.

According to the present embodiment described above, the first lamp ED1 and the second lamp ED2 are connected in series, and the current limiting circuit LMT (n-type MOS transistor M2, shunt resistor R4) is connected in series to them. There is no need to provide a separate drive circuit for the lamp. For this reason, it is possible to switch between a high beam and a low beam, reduce the number of parts, and simplify the apparatus configuration.
Further, according to the above-described embodiment, since the coil L2 is connected in series with the switch SW connected in parallel with the first lamp ED1 for high beam, the inrush current flowing through the switch SW is suppressed by the coil L2. be able to.
Further, according to the above-described embodiment, even when the inrush current cannot be sufficiently suppressed by the coil L2, the n-type MOS transistor M2 is controlled to be in the off state, and the inrush current is generated in the closed loop including the flywheel diode D2. By circulating the current, the inrush current can be suppressed.
In addition, according to the above-described embodiment, the first lamp ED1 and the second lamp ED2 are driven and lit with the ground potential (GND) as a reference, so that a capacitor for smoothing the voltage of each lamp is unnecessary. Become. Therefore, the apparatus configuration can be further simplified.

<Modification>
FIG. 5 is a circuit diagram showing a modification of the vehicle lamp driving device according to the embodiment of the present invention. FIG. 5A shows a first modification, and FIG. 5B shows a second modification.
In the configuration of FIG. 1 described above, the coil L2 is connected between the terminal T1 and one end (anode) of the current path of the first lamp ED1, but in the first modification, as shown in FIG. Instead of the diode D2 and the coil L2, a coil L2A is provided between the terminal T1 and the switch SW, and a flywheel diode D2A is provided as a rectifying element connected in parallel to the coil L2A. Note that the flywheel diode D2A may be omitted depending on the level of the inrush current.

  Specifically, the anode of the first lamp ED1 is connected to the terminal T1. Further, one end of the coil L2A is connected to the terminal T1, and one end of the current path of the switch SW is connected to the other end of the coil L2A. The other end of the current path of the coil L2A is connected to a connection point between the first lamp ED1 and the second lamp ED2, as in FIG. That is, a series circuit of the coil L2A and the switch SW is connected in parallel to the current path of the first lamp ED1. The coil L2A and the switch SW may be interchanged. The cathode of the flywheel diode D2A is connected to one end of the coil L2A connected to the terminal T1, and the anode of the flywheel diode D2A is connected to a connection point between the coil L2A and the switch SW. Other configurations are the same as those shown in FIG. Also according to this modification, the inrush current flowing into the second lamp ED2 when the switch SW is operated to the closed state can be suppressed by the coil L2A. When the switch SW is opened, the current flowing through the coil L2A is returned to the terminal T1 through the flywheel diode D2A.

Further, as shown in FIG. 5B, in the second modification, the switch SW is omitted in the configuration of FIG. Other configurations are the same as those shown in FIG. In the second modification, any inrush current flowing into the terminal T1 can be suppressed by the coil L2. Although the flywheel diode D2 is provided in the example of FIG. 5B, the flywheel diode D2 can be omitted as necessary. The first lamp ED1 and the second lamp ED2 may be a single lamp, and the configuration of the lamp connected between the terminal T1 and the terminal T2 is arbitrary.
As another modification, in the configuration of FIG. 1 or FIG. 5B, the anodes of the flywheel diodes D2 and D2A may be connected to a connection point between the first lamp ED1 and the second lamp ED2. Good. Also by this modification, an inrush current can be regenerated.

  The vehicle lamp driving device according to the second modification shown in FIG. 5B can be expressed as follows. That is, the vehicle lamp driving device according to the second modification includes one or more lamps (ED1, ED2) connected in series between the first terminal T1 and the second terminal T2 to which a DC voltage is applied. A vehicle lamp driving apparatus for driving, wherein a coil (inductive element) L2 connected in series with the one or more lamps between the first terminal T1 and the second terminal T2, and the first A current path connected in series with the one or more lamps between the terminal T1 and the second terminal T2, and flowing through a network comprising the one or more lamps and the inductive element; It can be expressed as a vehicle lamp driving device including a current limiting circuit LMT for limiting the current.

  In the above-described embodiment and modification of the present invention, the present invention is expressed as the vehicle lamp driving device 1, but the present invention can also be expressed as a vehicle lamp driving method. In this case, the vehicle lamp driving method according to the present invention drives the plurality of lamps ED1 and ED2 connected in series between the first terminal T1 and the second terminal T2 to which a DC voltage is applied. A switch SW connected in parallel with any one of the plurality of lamps ED1 and ED2 switches a lighting state of the lamps ED1 and ED2 having the current path, and the first terminal T1 and the A current limiting circuit LMT having a current path connected in series with the plurality of lamps ED1 and ED2 between the second terminal T2 and a current flowing through a circuit network including the plurality of lamps ED1 and ED2 and the switch SW. It can be expressed as a vehicle lamp driving method including the limiting step.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the present invention.
For example, in the above-described embodiment, the case where the present invention switches between the high beam and the low beam of the vehicle has been described as an example. However, the present invention can also be applied to a case where the illuminance of the lamp is switched. The present invention can also be applied to any lighting fixture.
In the above-described embodiment, the DC voltage Vin of the battery BA is boosted by the boost chopper circuit and supplied as the DC voltage Vout between the terminals T1 and T2. However, the battery BA is connected to the first lamp ED1. If the voltage necessary for lighting the second lamp ED2 can be supplied, the terminal T1 can be connected to the positive electrode of the battery BA without providing the step-up chopper circuit including the coil L1 and the like. Good.

DESCRIPTION OF SYMBOLS 1 ... Vehicle lamp drive device 100 ... Control part 110 ... Boost control 111 ... Switching control part 112 ... Driver 113 ... Voltage detection part 114 ... Overcurrent detection part 120 ... Current control part 121 ... Switching control part 122 ... Driver 123 ... Peak Current detector BA ... Battery C1, C2 ... Capacitor CHP ... Boost chopper circuit D1 ... Diode D2, D2A ... Flywheel diode ED1 ... First lamp ED2 ... Second lamp L1, L2, L2A ... Coil LMT ... Current limiting circuit M1, M2 ... n-type MOS transistors R1 to R4 ... resistors T1, T2, TM1 to TM8 ... terminals

Claims (4)

A vehicle lamp driving device for driving a plurality of lamps connected in series between a first terminal and a second terminal to which a DC voltage is applied,
A switch that is connected in parallel to a part of the current paths of the plurality of lamps, and that switches a lighting state of the first lamp having the current paths between lighting and extinguishing;
A current path in which the plurality of lamps and a switching element are connected in series between the first terminal and the second terminal, and restricts a current flowing through a circuit network including the plurality of lamps and the switch. Current limiting circuit for,
An inductive element connected in series with the current path of the switch;
A rectifying element that regenerates a current discharged from the inductive element when the switch switches the lighting state of the first lamp to the off state and the switching element is turned off. said rectifying element connected in parallel to a plurality of lamps and front Symbol inductive element,
With
Of the plurality of lamps, a second lamp that is a lamp other than the lamp connected in parallel with the switch maintains lighting in response to the application of the DC voltage regardless of switching of the switch,
The inductive element is a current generated with the switching of the switch, and suppresses an inrush current flowing into one of the plurality of lamps.
A lamp driving device for a vehicle. The current limiting circuit is:
A current detecting element for detecting a current flowing through the pre-Symbol switching element,
A control unit that controls conduction of the switching element based on a detection result of the current detection element so that a current flowing through the switching element becomes a specified value;
The vehicle lamp driving device according to claim 1, comprising:   One end of the inductive element is connected to the first terminal, and the plurality of lamps are connected in series between the other end of the inductive element and one end of the current path of the current limiting circuit, The second terminal is connected to the other end of the current path, the anode of the rectifying element is connected to one end of the current path of the current limiting circuit, and the first terminal is connected to the cathode of the rectifying element. The vehicle lamp driving device according to 1 or 2. A vehicle lamp driving method for driving a plurality of lamps connected in series between a first terminal and a second terminal to which a DC voltage is applied,
A switch connected in parallel with a part of the current paths among the plurality of lamps turns on and off the first lamp having the current path connected in parallel with the switches among the plurality of lamps. The stage to switch to either,
A current path in which the plurality of lamps and a switching element provided between the first terminal and the second terminal are connected in series, and a current flowing through a circuit network including the plurality of lamps and the switch are limited. Stages,
An inductive element connected in series with the current path of the switch suppresses inrush current;
If the switch is switched to turn off the lighting state of the first lamp, and when the switching element is turned off, a rectifying element, parallel to said plurality of lamps and front Symbol inductive element The rectifying element connected to the power supply regenerates the current discharged from the inductive element;
Including
In the step of switching the lighting state, among the plurality of lamps, the second lamp that is a lamp other than the lamp connected in parallel with the switch is applied with the DC voltage regardless of the switching of the switch. According to the lighting,
The inductive element is a current generated with the switching of the switch, and suppresses an inrush current flowing into one of the plurality of lamps.
A vehicle lamp driving method.

Images