JP6697729B2 - Lighting device, lighting device, and vehicle using the same - Google Patents

Description

  The present invention relates to a lighting device, a lighting device, and a vehicle using the lighting device, and more particularly, to a lighting device having a dimming function, a lighting device, and a vehicle using the lighting device.

  BACKGROUND ART Conventionally, a light emitting element driving device (lighting device) that performs PWM dimming of an LED (Light Emitting Diode) module unit has been proposed (see, for example, Patent Document 1). This light emitting element driving device includes a converter and a series circuit of an LED module section and a dimming switch element (switch section) connected between output terminals of the converter. The LED module section includes a plurality of LEDs connected in series. This light emitting element driving device controls the amount of light of the LED module section by intermittently controlling the current flowing through the LED module section (semiconductor light emitting element) by performing PWM control of the dimming switch element.

JP, 2013-149479, A

  In the light emitting element drive device of Patent Document 1, the output voltage of the converter is applied across the dimming switch element during the off period of the dimming switch element. When the number of LEDs in series constituting the LED module section is increased to obtain a large amount of light, it is necessary to increase the output voltage of the converter. Therefore, it is necessary to use a component having a higher withstand voltage than the output voltage of the converter as the dimming switch element (switch section).

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a lighting device capable of using a switch unit having a lower withstand voltage, an illumination device, and a vehicle using the same.

A lighting device of the present invention includes a DC power supply circuit that outputs a DC voltage, a switch unit, a dimming control circuit, and a power supply control circuit, and the switch unit is a semiconductor light source between output terminals of the DC power supply circuit. And a second state in which the switch unit is configured to be connected in series with the semiconductor light source and a second state in which a current having a second current value smaller than the first current value is flowed to the semiconductor light source. And the dimming control circuit alternately switches the state of the switch unit between the first state and the second state, and the time ratio of the first state and the second state is changed. The semiconductor light source is configured to perform PWM dimming by adjusting a certain duty ratio, and the DC power supply circuit has a voltage conversion circuit that performs voltage conversion by switching a power supply voltage input from a DC power supply. Then, the power supply control circuit controls the switching operation of the voltage conversion circuit, and the power supply control circuit controls the voltage conversion circuit so as to stop the switching operation in the second state during PWM dimming. It is characterized by
Another lighting device of the present invention includes a DC power supply circuit that outputs a DC voltage, a switch unit, a dimming control circuit, and a power supply control circuit. The switch unit is connected in series with the semiconductor light source between the output terminals of the DC power supply circuit. The switch unit is switched between a first state in which a current having a first current value is applied to the semiconductor light source and a second state in which a current having a second current value smaller than the first current value is applied to the semiconductor light source. The dimming control circuit alternately switches the state of the switch unit to the first state and the second state, and adjusts a duty ratio which is a temporal ratio between the first state and the second state. Thus, the semiconductor light source is configured to perform PWM dimming. The DC power supply circuit has a voltage conversion circuit that performs voltage conversion by switching a power supply voltage input from a DC power supply. The power supply control circuit controls the switching operation of the voltage conversion circuit based on the measured value of the output voltage or output current of the DC power supply circuit. In the second state at the time of PWM dimming, the power supply control circuit sets a value obtained by superimposing an addition value proportional to the voltage across the switch unit on the measured value of the output voltage or the output current of the DC power supply circuit. Based on this, the switching operation of the voltage conversion circuit is controlled.

  An illumination device of the present invention is characterized by including the above-mentioned lighting device, the semiconductor light source that the lighting device lights, and a case that houses the lighting device and the semiconductor light source.

  A vehicle of the present invention is characterized by including the above lighting device and a vehicle body to which the lighting device is attached.

  ADVANTAGE OF THE INVENTION According to this invention, the lighting device which can use the switch part with a lower withstand voltage, an illuminating device, and the vehicle using the same can be provided.

It is a circuit diagram of the lighting device of the first embodiment. It is a figure which shows the forward voltage-forward current characteristic of LED lighted by the lighting device of Embodiment 1. FIG. 6 is a circuit diagram showing another circuit configuration of the lighting device of the first embodiment. It is a circuit diagram of the lighting device of Embodiment 2. It is a circuit diagram which shows the other circuit structure of the lighting device of Embodiment 2. It is a circuit diagram which shows another circuit structure of the lighting device of Embodiment 2. It is a circuit diagram of the lighting device of Embodiment 3. It is a circuit diagram which shows the other circuit structure of the lighting device of Embodiment 3. It is a circuit diagram of the lighting device of Embodiment 4. It is a circuit diagram which shows the other circuit structure of the lighting device of Embodiment 4. It is a circuit diagram of a lighting device of the fifth embodiment. It is a circuit diagram which shows the other circuit structure of the lighting device of Embodiment 5. It is a circuit diagram which shows another circuit structure of the lighting device of Embodiment 5. It is a schematic block diagram of the illuminating device of Embodiment 6. FIG. 13 is an external perspective view of a vehicle of Embodiment 6.

  Hereinafter, embodiments of a lighting device, a lighting device, and a vehicle using the lighting device will be described with reference to the drawings. The present invention is not limited to the following embodiments, and various modifications can be made according to the design and the like as long as they do not depart from the technical idea of the present invention.

(Embodiment 1)
FIG. 1 shows a circuit diagram of the lighting device 1 of the first embodiment. The lighting device 1 according to the present embodiment is a lighting device that lights a lighting device (for example, a headlight) mounted on a vehicle (for example, an automobile or a motorcycle). The lighting device 1 is a headlight for the vehicle. Is not limited to the one that lights up, and may be applied to other uses.

  The lighting device 1 of the present embodiment includes a DC power supply circuit 10, a control circuit 20 that is a dimming control circuit, and a switch unit 30. The DC power supply circuit 10 outputs a DC voltage. The switch unit 30 is connected in series with the semiconductor light source 2 between the output terminals of the DC power supply circuit 10. The switch unit 30 is switched between a first state in which a current having a first current value is supplied to the semiconductor light source 2 and a second state in which a current having a second current value smaller than the first current value is supplied to the semiconductor light source 2. The control circuit 20 alternately switches the state of the switch unit 30 between the first state and the second state, and adjusts the duty ratio, which is the temporal ratio between the first state and the second state, to control the semiconductor light source 2. PWM dimming.

  As a result, even in the second state during PWM dimming, the current having the second current value flows through the semiconductor light source 2, so that the voltage applied to the switch unit 30 changes from the output voltage of the DC power supply circuit 10 to the semiconductor light source 2. It becomes the voltage which subtracted the voltage between both ends of. Therefore, the voltage applied to the switch unit 30 decreases, and the withstand voltage of the switch unit 30 can be set to a voltage lower than the output voltage of the DC power supply circuit 10. Therefore, a component with a lower withstand voltage can be used for the switch unit 30. .. Since a component having a lower withstand voltage can be used for the switch unit 30, it is possible to reduce the size and cost of the lighting device 1.

  Next, the circuit configuration of the lighting device 1 will be described in more detail.

  The lighting device 1 of the present embodiment has three input terminals t1, t2, t3, two output terminals t4, t5, a DC power supply circuit 10, a control circuit 20, a switch unit 30, and an impedance adjustment circuit 50. Equipped with. The lighting device 1 lights the semiconductor light source 2 with electric power supplied from the DC power supply 100.

  The DC power supply 100 is, for example, a vehicle battery. The DC power supply 100 may be an AC-DC converter that rectifies and smoothes an AC voltage input from the AC power supply to convert the AC voltage into a DC voltage.

  The semiconductor light source 2 includes a plurality (40 in the present embodiment) of LEDs 2a connected in series. The semiconductor light source 2 is not limited to one having the LED 2a as a light source, and may include a solid-state light emitting source other than the LED (for example, an electroluminescence element other than the LED, an organic EL element, etc.). The series circuit of 40 LEDs 2a constituting the semiconductor light source 2 is connected between the output terminal t4 and the output terminal t5 in such a direction that current flows from the output terminal t4 to the output terminal t5 via the semiconductor light source 2. There is. Note that FIG. 2 shows the forward voltage-forward current characteristics of the LED 2a.

  The input terminals t1 and t2 are electrically connected to the positive electrode of the DC power supply 100 via the switches 101 and 102, respectively. The input terminal t3 is electrically connected to the negative electrode of the DC power supply 100. The switch 101 is used to switch ON/OFF of the semiconductor light source 2. The switch 102 is used to switch the lighting state of the semiconductor light source 2 between the full lighting state and the dimming lighting state. When the switch 101 is on and the switch 102 is off, the semiconductor light source 2 is turned on at a dimming level of 100% (this state is called a fully-lit state). When the switch 102 is turned on while the switch 101 is turned on, the semiconductor light source 2 is turned on at a preset dimming level (this state is called a dimming lighting state).

  The semiconductor light source 2 is connected between the output terminals t4 and t5.

  The DC power supply circuit 10 is composed of a step-up chopper circuit composed of a switching element 11, a choke coil 12, capacitors 13, 15 and a diode 14.

  A capacitor 13, a choke coil 12 and a series circuit of a switching element 11 are connected in parallel between the input terminals t1 and t3. The anode of the diode 14 is connected to the connection point between the choke coil 12 and the switching element 11, and the capacitor 15 is connected between the cathode of the diode 14 and the input terminal t3. The terminal on the high potential side of the capacitor 15 is connected to the output terminal t4, and the terminal on the low potential side of the capacitor 15 is electrically connected to the output terminal t5 via the switch unit 30. The switching element 11 is, for example, an N-channel MOSFET (Metal Oxide Semiconductor Field Effect Transistor), and is turned on/off by a control signal S2 input from the control circuit 20.

  The DC power supply circuit 10 turns on the semiconductor light source 2 with the power supply voltage V1 input from the DC power supply 100 by causing the switching element 11 to perform a switching operation according to the control signal S2 input from the control circuit 20. The DC voltage V2 is converted to a required voltage value.

  The switch unit 30 has a switching element 31 connected between the output terminal t5 and the input terminal t3. In the full lighting state, the switching element 31 is always controlled to be in the on state (first state). In the dimming lighting state, the switching element 31 is switched between the first state and the second state. Here, the "first state" is a state in which a current having a first current value (for example, a rated load current) flows through the semiconductor light source 2 (a state in which the semiconductor light source 2 is turned on in a saturated state), and the "second state" This is a state in which a current having a second current value smaller than the first current value is passed through the semiconductor light source 2. In addition, it is preferable that the second current value is a current value that is 1/100 or less of the first current value.

  The control circuit 20 includes an output control circuit 21, a comparator 22, an OR gate 23, an AND gate 24, a constant voltage source 25, and an oscillation circuit 26 as constituent elements.

  The output control circuit 21 includes, for example, a microcomputer as a constituent element. When the microcomputer executes the program stored in the memory, the function of controlling the output of the DC power supply circuit 10 and the function of controlling ON/OFF of the switch unit 30 are realized. This program may be provided through an electric communication line, or may be provided by being stored in a recording medium such as a memory card. The voltage values of the input voltage and the output voltage V2 of the DC power supply circuit 10 and the current value of the output current of the DC power supply circuit 10 measured by the current sensor 16 are input to the output control circuit 21. The output control circuit 21 outputs a control signal S2 for PWM-controlling the switching element 11 to the AND gate 24 so that the output current of the DC power supply circuit 10 reaches a preset target value.

  The inverting input terminal of the comparator 22 is connected to the input terminal t2, and the non-inverting input terminal of the comparator 22 is connected to the constant voltage source 25. When the switch 102 is on, the voltage of the input terminal t2 (power supply voltage V1) becomes higher than the voltage value of the constant voltage source 25, so that the output signal of the comparator 22 becomes low. On the other hand, when the switch 102 is off, the voltage of the input terminal t2 becomes lower than the voltage value of the constant voltage source 25, so that the output signal of the comparator 22 becomes high.

  The output signal of the comparator 22 and the rectangular wave signal of the oscillation circuit 26 are input to the OR gate 23. The output signal S1 of the OR gate 23 is input to the base of the switching element 31 via the diode 53 and the resistor 52.

  The output signal S1 of the OR gate 23 and the control signal S2 output from the output control circuit 21 are input to the AND gate 24.

  The oscillator circuit 26 outputs a rectangular wave signal having a preset frequency and duty ratio.

The impedance adjustment circuit 50 has a resistor 51 whose one end is connected to the base of the switching element 31. The other end of the resistor 51 is connected to a constant voltage circuit for control which supplies a constant DC voltage Vcc to the control circuit 20 and the like.
The impedance adjustment circuit 50 adjusts the impedance between both ends of the switching element 31 to an impedance such that the current value of the current flowing through the semiconductor light source 2 becomes the second current value in the second state during PWM dimming. The impedance adjusting circuit 50 adjusts the impedance between both ends of the switching element 31 to be much smaller than the impedance in the second state in the first state during full lighting or PWM dimming.

  Next, the operation of the lighting device 1 of the present embodiment will be described.

  When the switch 101 is off, the power supply voltage V1 is not input to the DC power supply circuit 10, and the semiconductor light source 2 is turned off.

  When the switch 101 is on and the switch 102 is off, the output signal of the comparator 22 becomes high and the output signal S1 of the OR gate 23 remains high, so that the switching element 31 continues to be on. The output control circuit 21 outputs to the AND gate 24 the control signal S2 in which the switching frequency or the duty ratio of the switching element 11 is adjusted according to the detected values of the output voltage and the output current. Since the output signal S1 of the OR gate 23 maintains the high state, the control signal S2 is output from the AND gate 24 as it is, and the ON/OFF of the switching element 11 is controlled by the control signal S2. As a result, the output voltage of the DC power supply circuit 10 is controlled to a voltage value required to maintain the preset output current, and the output current of the DC power supply circuit 10 is supplied to the semiconductor light source 2 and the semiconductor light source 2 Lights up. Further, the output control circuit 21 monitors the output voltage V2 of the DC power supply circuit 10. When the measured value of the output voltage V2 exceeds the preset upper limit voltage, the output control circuit 21 reduces the on-duty of the control signal S2 or stops the output of the control signal S2 to stop the switching operation. Thus, the overvoltage protection control for suppressing the output voltage V2 is performed.

  When both the switches 101 and 102 are turned on, the voltage value of the input terminal t2 becomes higher than the voltage value of the constant voltage source 25, the output signal of the comparator 22 becomes low, and the oscillation circuit 26 from the OR gate 23 is output. The rectangular wave signal of is output as it is. That is, the output signal S1 of the OR gate 23 becomes the same signal as the rectangular wave signal of the oscillation circuit 26.

  During the period when the signal level of the output signal S1 is high, the base current flows from the control circuit 20 to the switching element 31 via the diode 53 and the resistor 52, and the switching element 31 is in the first state (state in which it is turned on in the saturation region). ), and a current flows through the semiconductor light source 2. When the switching element 31 is in the first state, the impedance between both ends of the switching element 31 becomes such an impedance that allows the semiconductor light source 2 to flow a current having a first current value (for example, a rated lighting current).

  Here, when the rated lighting current of the 40 LEDs 2a constituting the semiconductor light source 2 is 50 [mA] and the forward voltage is 2.8 [V], when the rated lighting current flows through the semiconductor light source 2, the semiconductor The voltage across the light source 2 is about 112 [V]. When the current amplification factor of the switching element 31 is β, at least (50/β) [mA] or more is applied to the switching element 31 in order to flow the rated lighting current to the switching element 31 when the switching element 31 is on (first state). It is necessary to pass the base current of. Therefore, the resistance value of the resistor 52 is set to a resistance value such that the base current becomes (50/β) [mA] or more in the first state.

  When the signal level of the output signal S1 becomes low, the output of the AND gate 24 also becomes low, and the control signal S1 of the output control circuit 21 is no longer output from the AND gate 24. At this time, since the switching element 11 is turned off and the switching operation of the DC power supply circuit 10 is stopped, the output voltage V2 of the DC power supply circuit 10 does not rise even if the output current decreases. Even if the output voltage V2 of the DC power supply circuit 10 does not rise, the output voltage V2 drops slowly because the smoothing capacitor 15 is connected to the output end of the DC power supply circuit 10.

  When the signal level of the output signal S1 becomes low, the base current stops flowing from the control circuit 20 to the switching element 31. Here, when the switching element 31 is completely turned off and the output current becomes zero, the rated load voltage (about 112V) is entirely applied to the switching element 31, so that the switching element 31 has a withstand voltage of at least 120V. Will be required. Considering variations in the forward voltage of the LED 2a, temperature characteristics, and the like, a switching element having a higher withstand voltage is required.

  Therefore, in the present embodiment, during the period when the signal level of the output signal S1 is low, a minute base current is passed from the constant voltage circuit to the switching element 31 through the resistor 51 to switch the switching element 31 to the second state. In the second state, the impedance (on-resistance) between both ends of the switching element 31 is adjusted to an impedance such that the current value of the current flowing through the semiconductor light source 2 becomes the second current value. Here, it is preferable that the second current value is a current value that is 1/100 or less of the current (for example, the rated lighting current) flowing through the semiconductor light source 2 in the first state. For example, when the second current value is set to a current value 1/1000 of the rated lighting current (0.05 [mA]), the base of the switching element 31 is (0.05/β) [mA]. The resistance value of the resistor 51 may be set so that the current flows. By passing such a base current through the switching element 31, the current flowing through the semiconductor light source 2 becomes 1/1000 of the rated lighting current (0.05 [mA]), and the LEDs 2a each have 2.45. A forward voltage of [V] is generated. Therefore, a voltage drop of 98V occurs in the entire semiconductor light source 2, so that the voltage applied to the switching element 31 is reduced to 14V, and an element having a low withstand voltage can be used as the switching element 31.

  When both the switches 101 and 102 are on, the switching element 31 is alternately switched between the first state and the second state according to the high/low of the output signal S1 which is a rectangular wave signal. Therefore, the semiconductor light source 2 is PWM dimmed by alternately repeating the period in which the output current has the first current value and the period in which the output current has the second current value. When dimming is performed by reducing the value of the current flowing through the semiconductor light source 2, the tint of the output light may change, but in the present embodiment, the duty ratio between the first state and the second state is adjusted. Therefore, since the light is controlled, it is possible to control the light while suppressing the change in the tint of the output light.

  In the diode 53, when the signal level of the output signal S1 becomes low during PWM dimming, the base current supplied from the constant voltage circuit to the switching element 31 via the resistor 51 does not flow to the resistor 52 side. Is provided. The diode 53 may be omitted depending on conditions such as resistance values of the resistors 51 and 52.

  Further, in the circuit configuration of FIG. 1, the base current is supplied from the constant voltage circuit to the switching element 31 via the resistor 51 in the second state during PWM dimming. A circuit configuration that allows a base current to flow from the output may be used.

  In addition, when the current flowing through the semiconductor light source 2 in the second state is set to a sufficiently small value (for example, 1/100 or less) compared to the steady lighting current flowing through the semiconductor light source 2 in the first state, the semiconductor in the second state is reduced. The light output of the light source 2 has almost no effect on the average light output during PWM dimming.

  Another circuit example of the lighting device 1 of the present embodiment will be described with reference to FIG. The same components as those of the lighting device 1 shown in FIG. 1 are designated by the same reference numerals and the description thereof will be omitted.

  The lighting device 1 shown in FIG. 3 includes a switching element 54 for forming a current mirror circuit together with a switching element 31 for PWM dimming. The switching element 54 is an npn-type transistor, the base and collector of the switching element 54 are connected to the base of the switching element 31, and the emitter of the switching element 54 is connected to the circuit ground via the resistor 55. Further, a resistor 17 for current detection is connected in series with the switching element 31.

  In the lighting device 1 having the circuit configuration shown in FIG. 3, when the signal level of the output signal S1 becomes high during PWM dimming, a collector current flows from the control circuit 20 to the transistor 54 via the diode 53 and the resistor 52.

  Here, the voltage value when the signal level of the output signal S1 becomes high is VS1, and the resistance values of the resistors 17, 51, 52, and 55 are R17, R51, R52, and R55, respectively. It is assumed that the base-emitter voltage of the switching elements 31 and 54 and the forward voltage of the diode 53 are 0 [V], and the current amplification factor of the switching elements 31 and 54 is infinite. It is very small compared to the flowing current. Further, the resistance values R17 and R55 are set to be much smaller than the resistance values R51 and R52. In this case, the collector current of the switching element 54 is VS1/R52, and the collector current of the switching element 31 is (R55/R17)×(VS1/R52). Here, if the value of (R55/R17)×(VS1/R52) is sufficiently large with respect to the current value of the current flowing through the semiconductor light source 2 in the first state, the impedance of the switching element 31 in the first state is sufficient. Becomes smaller.

  On the other hand, when the signal level of the output signal S1 becomes low (second state), the collector current of the switching element 54 is only the current flowing from the constant voltage circuit through the resistor 51.

  Here, the current flowing through the semiconductor light source 2 in the second state is set to a much smaller current (for example, 1/100 or less) than the current flowing through the semiconductor light source 2 in the first state. Therefore, assuming that the current value of the current flowing through the semiconductor light source 2 in the second state is Im, the resistance values of the resistors 17, 55 are set so that the collector current of the switching element 54 becomes (R17/R55)×Im. Good.

  As a result, even in the second state, a very small current flows in the semiconductor light source 2 as compared with the first state, so that the voltage applied to the switching element 31 can be reduced, and an element having a low withstand voltage is used for the switching element 31. it can.

  In the circuit of FIG. 3, in the second state, the collector current is supplied from the constant voltage circuit to the switching element 54 that sets the value of the current flowing in the switching element 31 through the resistor 51. A collector current may flow from the power supply circuit 10.

  In the lighting device 1 of FIGS. 1 and 3, the switching element 31 for PWM dimming is a transistor, but the switching element 31 is not limited to a transistor. The switching element 31 may be a switching element such as an IGBT (Insulated Gate Bipolar Transistor) or MOSFET, and the switching is such that the output signal S1 for PWM dimming output from the control circuit 20 switches between the first state and the second state. Any element will do.

  Further, in the lighting device 1 of the present embodiment, the switching element 31 for PWM dimming is connected to the output terminal on the low potential side of the DC power supply circuit 10. However, the switching element 31 for PWM dimming is a DC power supply circuit. It may be connected to the high potential side output terminal of 10.

  Further, the lighting device 1 of the present embodiment may further include an impedance adjustment circuit 50. The switch unit 30 has a switching element 31 connected between the output terminals of the DC power supply circuit 10 via the semiconductor light source 2. The switching element 31 has a control terminal whose impedance can be adjusted. In the second state during PWM dimming, the impedance adjustment circuit 50 adjusts the signal (current or voltage) input to the control terminal so that the impedance of the switching element 31 is equal to the current value of the current flowing through the semiconductor light source 2. The impedance is adjusted so that the second current value is obtained.

  In this way, the impedance adjusting circuit 50 adjusts the impedance of the switching element 31 to an impedance such that the current value of the current flowing through the semiconductor light source 2 becomes the second current value in the second state during PWM dimming. There is. Thereby, the voltage applied to the switching element 31 can be reduced, and an element having a lower withstand voltage can be used as the switching element 31.

  The lighting device 1 of the present embodiment may further include a power supply control circuit (control circuit 20). The DC power supply circuit 10 has a voltage conversion circuit (for example, a boost chopper circuit) that performs voltage conversion by switching the power supply voltage input from the DC power supply 100. The power supply control circuit controls the switching operation of the voltage conversion circuit. The power supply control circuit controls the voltage conversion circuit so as to stop the switching operation in the second state during PWM dimming.

In this way, the control circuit 20 as a power supply control circuit, since in the second state of the PWM dimming controls the voltage conversion circuit so as to stop the switching operation, dc power supply circuit when the output current drops The increase of the output voltage V2 of 10 can be suppressed.

(Embodiment 2)
FIG. 4 shows a circuit diagram of the lighting device 1 of the second embodiment. The same components as those of the lighting device 1 of Embodiment 1 are designated by the same reference numerals, and the description thereof will be omitted.

  In the lighting device 1 of the present embodiment, the switch unit 30 for PWM dimming includes a switching element 32 and a bypass circuit 33 connected in parallel with the switching element 32.

  The switching element 32 is, for example, an N-channel MOSFET, and is switched on or off according to the output signal S1 directly input from the control circuit 20 to the gate electrode. That is, during PWM dimming, when the signal level of the output signal S1 becomes high, the switching element 32 turns on, and the rated lighting current flows through the switching element 32. On the other hand, during PWM dimming, when the signal level of the output signal S1 becomes low, the switching element 32 is turned off and no current flows through the switching element 32.

  The bypass circuit 33 is, for example, a resistor, and has an impedance such that the current value of the current flowing through the semiconductor light source 2 becomes the second current value. The bypass circuit 33 is not limited to the resistor, and may be a circuit element other than the resistor as long as the circuit element has a predetermined impedance.

  In the present embodiment, when the signal level of the output signal S1 becomes high during PWM dimming, the switching element 32 is turned on. Therefore, the steady lighting current (current of the first current value) is applied to the semiconductor light source 2 via the switching element 32. Flows. On the other hand, when the signal level of the output signal S1 becomes low during PWM dimming, the switching element 32 is turned off, and a current having the second current value flows through the semiconductor light source 2 via the bypass circuit 33. That is, in the first state, a current flows through the semiconductor light source 2 via the switching element 32, and in the second state, a current flows through the semiconductor light source 2 through the bypass circuit 33.

  As a result, even when the switching element 32 for PWM dimming is turned off during PWM dimming, a minute current flows through the semiconductor light source 2 via the bypass circuit 33, so the voltage applied to the switching element 32 is reduced. it can.

  The bypass circuit 33 may be a constant current circuit that allows a constant current (current of a second current value) to flow, and a circuit diagram of the lighting device 1 including the bypass circuit 40 realized by the constant current circuit is shown in FIG. In the lighting device 1 having the circuit configuration shown in FIG. 5, the same components as those of the lighting device 1 described in FIG. 4 are designated by the same reference numerals, and the description thereof will be omitted.

  In the lighting device 1 of FIG. 5, the PWM dimming switch unit 30 includes a bypass circuit 40 realized by a constant current circuit and a switching element 32.

  The bypass circuit 40 includes an npn-type transistor 41, a constant voltage source 42, and a resistor 43. The collector of the transistor 41 is connected to the connection point between the semiconductor light source 2 and the switching element 32. A constant voltage source 42 is connected to the base of the transistor 41, and the emitter of the transistor 41 is connected to the circuit ground via a resistor 43.

  In this bypass circuit 40, the transistor 41 operates as an emitter follower, and the emitter terminal voltage is determined by the voltage value of the constant voltage source 42 applied to the base of the transistor 41. Therefore, the emitter current of the transistor 41 becomes a constant current determined by the emitter terminal voltage and the resistance value of the resistor 43. If the base current is so small that it can be ignored, the collector current becomes almost the same as the emitter current, so that a constant current flows through the collector of the transistor 41. The constant current circuit forming the bypass circuit 40 is not limited to the circuit example of FIG. 5, and can be changed as appropriate.

  Further, in the present embodiment, the switching element 32 for PWM dimming is a MOSFET, but the switching element 32 may be a switching element such as a bipolar transistor or an IGBT.

  Further, in the present embodiment, the switching element 32 for PWM dimming is connected to the output terminal on the low potential side of the DC power supply circuit 10. However, as shown in FIG. It may be connected to the output terminal on the high potential side of the DC power supply circuit 10. In the lighting device 1 having the circuit configuration shown in FIG. 6, the same components as those of the lighting device 1 described with reference to FIG. 4 or 5 are designated by the same reference numerals, and the description thereof will be omitted.

  In the lighting device 1 shown in FIG. 6, the switch unit 30 includes a switching element 32 and a resistor 34.

  The switching element 32 is a P-channel MOSFET, and is connected between the high-potential-side output end of the DC power supply circuit 10 and the output terminal t4. A parallel circuit of a resistor 57 and a Zener diode 59 is connected between the gate and source of the switching element 32. The gate electrode of the switching element 32 is connected to the low potential side output end of the DC power supply circuit 10 via the resistor 58 and the switching element 56. The switching element 56 is an N-channel MOSFET, and the output signal S1 of the control circuit 20 is directly input to the gate electrode of the switching element 56.

  The resistor 34 constitutes a bypass circuit, and the impedance of the resistor 34 is set so that the current flowing through the semiconductor light source 2 has a second current value in the second state during PWM dimming. The bypass circuit is not limited to the resistor 34, and may be a circuit element other than the resistor as long as the circuit element has an impedance such that the current flowing through the semiconductor light source 2 has the second current value in the second state.

  The operation other than the PWM dimming is the same as that of the lighting device 1 of the first embodiment, and thus the description thereof is omitted.

  When the signal level of the output signal S1 becomes high during PWM dimming, the level shift switching element 56 is turned on, and a current flows from the source electrode of the switching element 32 through the resistors 57 and 58. At this time, a voltage obtained by dividing the output voltage V2 of the DC power supply circuit 10 by the resistors 57 and 58 is applied to the gate electrode of the switching element 32. When the voltage of the gate electrode falls below the threshold voltage with reference to the voltage of the source electrode, the switching element 32 is turned on and a current having the first current value flows in the semiconductor light source 2.

  When the signal level of the output signal S1 becomes low during PWM dimming, the level shift switching element 56 is turned off. When the switching element 56 is turned off, no current flows through the resistors 57 and 58, the voltage of the gate electrode of the switching element 32 becomes substantially the same as the voltage of the source electrode, and the switching element 32 is turned off. When the switching element 32 is turned off, a current having the second current value flows through the resistor 34 to the semiconductor light source 2, so that a voltage drop occurs in the semiconductor light source 2 and the voltage applied to the switching element 32 is reduced.

  As described above, the switch unit 30 of the lighting device 1 may include the switching element 32 and the bypass circuit (the bypass circuits 33 and 40 or the resistor 34). The switching element 32 is connected between the output terminals of the DC power supply circuit 10 via the semiconductor light source 2. The bypass circuit has an impedance that makes the current value of the current flowing through the semiconductor light source 2 the second current value, and is connected in parallel with the switching element 32 in the second state during PWM dimming.

  In the second state during PWM dimming, by supplying a current to the semiconductor light source 2 via the bypass circuit, a voltage drop is generated in the semiconductor light source 2 and the voltage applied to the switching element 31 can be reduced. A device having a lower withstand voltage can be used as the device 31.

  In the present embodiment, the bypass circuit is always connected in parallel with the switching element 32, but a switch for connecting the bypass circuit in parallel with the switching element 32 is provided only in the second state during PWM dimming. Good.

(Embodiment 3)
FIG. 7 shows a circuit diagram of the lighting device 1 of the third embodiment. The same components as those of the lighting device 1 described in the first embodiment are designated by the same reference numerals, and the description thereof will be omitted.

  In the lighting device 1 of the first embodiment, the impedance adjustment circuit 50 sets the impedance of the switching element 31 to an impedance that causes the current flowing through the semiconductor light source 2 to be the second current in the second state during PWM dimming. There is.

  On the other hand, the impedance adjustment circuit 50 of the present embodiment sets the ON resistance of the switching element 32 so that the measured value of the voltage across the switching element 32 does not exceed the upper limit voltage value in the second state during PWM dimming. I am adjusting.

  In the circuit configuration of FIG. 7, the switching element 32 that configures the switch unit 30 is connected between the output terminal t5 and the low-potential-side output end of the DC power supply circuit 10. The switching element 32 is an N-channel type MOSFET.

  The impedance adjustment circuit 50 includes a Zener diode 60 and a resistor 61. The cathode of the Zener diode 60 is connected to the drain electrode of the switching element 32, and the anode of the Zener diode 60 is connected to the gate electrode of the switching element 32. The resistor 61 is connected between the gate electrode of the switching element 32 and the output end of the control circuit 20 (the output terminal of the OR gate 23).

  The operation other than the PWM dimming is the same as that of the lighting device 1 of the first embodiment, and thus the description thereof is omitted.

  When the signal level of the output signal S1 becomes low during PWM dimming, the switching element 32 is turned off and the drain voltage rises. When the drain voltage of the switching element 32 exceeds the Zener voltage VZ60 of the Zener diode 60, the Zener diode 60 becomes conductive and the voltage obtained by subtracting the Zener voltage VZ60 from the drain voltage is applied to the resistor 61 and the gate electrode. When the drain voltage further rises and reaches a voltage near the voltage obtained by adding the threshold voltage Vth of the switching element 32 to the zener voltage VZ60, the switching element 32 starts to turn on, and the impedance between the drain and source electrodes decreases, and the semiconductor Electric current starts to flow to the light source 2. When the current flowing in the semiconductor light source 2 increases, the drain voltage decreases and the impedance between the drain and source electrodes increases, so the voltage between the drain and source electrodes stabilizes near the voltage value (VZ60+Vth). Therefore, by selecting the Zener diode 60 such that the voltage value (VZ60+Vth) becomes a predetermined voltage value smaller than the withstand voltage of the switching element 32, the stress applied to the switching element 32 can be reduced.

  When the voltage value (VZ60+Vth) is set too low, the current flowing through the switching element 32 does not decrease to the second current value even though the switching element 32 is in the second state, and the average light output during dimming is set. Affect. Therefore, by considering the forward voltage-forward current characteristic of the LED 2a and setting the voltage value (VZ60+Vth) to a voltage value that is somewhat high, the current flowing through the semiconductor light source 2 in the second state is compared to the rated lighting current. The current value can be suppressed to a sufficiently small value.

  In the circuit configuration of FIG. 7, the Zener diode 60 is connected between the drain and the gate electrode in order to directly measure the voltage across the switching element 32, but the configuration is not limited to this. In the second state during PWM dimming, the voltage across the switching element 32 is measured, and the signal input to the control terminal (gate electrode) of the switching element 32 is adjusted so that the voltage across the switching element 32 does not exceed a predetermined voltage. Any circuit configuration may be used as long as it has a proper circuit configuration.

  Further, although the switching element 32 is a MOSFET in the circuit configuration of FIG. 7, it may be a switching element such as a bipolar transistor or an IGBT.

  Further, in the circuit configuration of FIG. 7, the PWM dimming switching element 32 is connected to the low-potential-side output end of the DC power supply circuit 10. However, as shown in FIG. 8, the PWM dimming switching element is used. 32 may be connected to the output terminal on the high potential side of the DC power supply circuit 10.

  In the circuit configuration of FIG. 8, the switching element 32 that configures the switch unit 30 is connected between the output terminal on the high potential side of the DC power supply circuit 10 and the output terminal t4.

  The switching element 32 is a P-channel type MOSFET. A series circuit of resistors 57 and 58 and a switching element 56 is connected between the output terminals of the DC power supply circuit 10. The output signal S1 of the control circuit 20 is input to the gate electrode of the switching element 56. The connection point of the resistors 57 and 58 is connected to the gate electrode of the switching element 32. The cathode of the Zener diode 62 is connected to the gate electrode of the switching element 32. The anode of the Zener diode 62 is connected to the anode of the diode 63, and the cathode of the diode 63 is connected to the low potential side output terminal of the DC power supply circuit 10 via the resistor 65. The drain electrode of the switching element 32 is connected to the anode of the diode 64, and the cathode of the diode 64 is connected to the connection point between the diode 63 and the resistor 65. Here, the impedance adjusting circuit 50 is composed of the resistors 57, 58 and 65, the Zener diode 62, the diodes 63 and 64, the switching element 56 and the like.

  The operation other than the PWM dimming is the same as that of the lighting device 1 of the first embodiment, and thus the description thereof is omitted.

  When the signal level of the output signal S1 becomes high and the switching element 56 is turned on during PWM dimming, the output voltage V2 of the DC power supply circuit 10 is divided by the resistors 57 and 58 into the gate electrode of the switching element 32. A voltage is applied. At this time, the potential difference between the source voltage (output voltage V2) of the switching element 32 and the gate voltage (voltage across the resistor 57) becomes equal to or higher than the threshold voltage Vth32, so that the switching element 32 is turned on and the DC power supply circuit 10 The rated lighting current is supplied from the semiconductor light source 2 to the semiconductor light source 2.

  During PWM dimming, when the signal level of the output signal S1 becomes low and the switching element 56 is turned off, the gate voltage of the switching element 32 rises. When the gate voltage increases, the impedance of the switching element 32 increases, the current flowing through the semiconductor light source 2 decreases, and the voltage of the output terminal t4 decreases. Since the connection point between the diode 63 and the resistor 65 is connected to the output terminal t4 via the diode 64, the potential at the connection point between the diode 63 and the resistor 65 becomes substantially the same voltage as the voltage at the output terminal t4. When the potential difference between the output voltage V2 of the DC power supply circuit 10 and the voltage of the output terminal t4 exceeds the Zener voltage VZ62 of the Zener diode 62 due to the decrease of the voltage of the output terminal t4, a part of the current to the resistor 65 is generated. It is supplied from the Zener diode 62 side. This current controls the voltage drop amount of the resistor 57, that is, the gate voltage of the switching element 32, and the impedance of the switching element 32 is adjusted.

  As the potential difference between the output voltage V2 of the DC power supply circuit 10 and the output terminal t4 is larger than (VZ62+Vth32), the gate voltage of the switching element 32 is reduced and the impedance of the switching element 32 is reduced. The value increases. Conversely, as the potential difference between the output voltage V2 of the DC power supply circuit 10 and the output terminal t4 is smaller than (VZ62+Vth32), the gate voltage of the switching element 32 increases and the impedance of the switching element 32 increases. Voltage value decreases. That is, during PWM dimming, during the period when the signal level of the output signal S1 is low (second state), the voltage across the switching element 32 (drain-source voltage) can be adjusted to near (VZ62+Vth32). it can.

  As a result, the current flowing through the semiconductor light source 2 in the second state is controlled to a current value much smaller than the current flowing through the semiconductor light source 2 in the first state.

  The circuit configuration shown in FIG. 8 is an example, and the circuit configuration of the lighting device 1 is not limited to the circuit configuration shown in FIG. In the second state during PWM dimming, the voltage across the switching element 32 is detected by a differential amplifier circuit or the like, and the control terminal of the switching element 32 is adjusted so that the voltage across the switching element 32 does not exceed a predetermined voltage. If so, the lighting device 1 may have any circuit configuration.

  Further, in the lighting device 1 shown in FIG. 8, the switching element 32 for PWM dimming is a MOSFET, but it may be a switching element such as a bipolar transistor or an IGBT.

  As described above, in the impedance adjustment circuit 50 of the lighting device 1, in the second state during PWM dimming, the measured value obtained by directly or equivalently measuring the voltage across the switching element 32 is higher than the withstand voltage of the switching element 32. The impedance across the switching element 32 may be adjusted so as not to exceed the lower upper limit voltage value.

    Accordingly, the voltage across the switching element 32 can be controlled so as not to exceed the upper limit voltage value.

  The configuration of this embodiment may be applied to the lighting device 1 of the second embodiment.

(Embodiment 4)
FIG. 9 shows a circuit diagram of the lighting device 1 of the fourth embodiment. The same components as those of the lighting device 1 described in the first embodiment are designated by the same reference numerals, and the description thereof will be omitted.

  In the first to third embodiments, when the switching element 31 is in the second state during PWM dimming, the switching operation of the DC power supply circuit 10 is stopped so that the output voltage V2 of the DC power supply circuit 10 does not rise excessively. There is. On the other hand, when the switching element 31 is switched from the second state to the first state during the PWM dimming and the DC power supply circuit 10 restarts the switching operation, the output current does not increase rapidly. Therefore, the output voltage V2 exceeds the output voltage immediately after the restart. Shoot, which can cause overcurrent in the output current.

  Therefore, in the lighting device 1 of this embodiment, the function of the overcurrent protection circuit is added to the impedance adjustment circuit 50.

  In the lighting device 1 of the present embodiment, the switch unit 30 includes the switching element 31 which is an npn-type transistor, and the resistor 17 for detecting the output current is provided between the collector of the switching element 31 and the input terminal t3. It is connected.

  The impedance adjusting circuit 50 is a differential amplifier circuit using transistors 71 and 72 and resistors 73 to 76.

  The base of the transistor 72 is connected to the connection point between the resistor 17 and the switching element 31, and a voltage proportional to the output current is applied to the base of one transistor 72 of the differential amplifier circuit. A voltage obtained by dividing the output signal S1 of the control circuit 20 by the resistors 74 and 75 is applied to the base of the other transistor 71 of the differential amplifier circuit, and the collector of the transistor 71 is connected to the base of the switching element 31. ing. A voltage obtained by dividing the voltage of the output terminal t5 by the resistors 76 and 77 is applied to the base of the switching element 31. Further, the base voltage VB72 input to the base of the transistor 72 becomes substantially the same voltage as that generated across the resistor 17.

  The operation other than the PWM dimming is the same as that of the lighting device 1 of the first embodiment, and thus the description thereof is omitted.

  When the signal level of the output signal S1 is high during PWM dimming and the output current flowing through the semiconductor light source 2 is about the first current value, the base voltage VB72 of the transistor 72 (voltage across the resistor 17) of the transistor 71 is The resistance values of the resistor 17 and the voltage dividing resistors 74 and 75 are set so as to be lower than the base voltage VB71. When an overcurrent flows in the semiconductor light source 2 and the base voltage VB72 of the transistor 72 rises to the base voltage VB71 of the transistor 71, the collector current of the transistor 72 increases. As a result, the collector current of the transistor 71 decreases and the base current of the switching element 31 decreases, so that the impedance adjusting circuit 50 as an overcurrent protection circuit operates so as to decrease the current flowing through the semiconductor light source 2.

  When the signal level of the output signal S1 is low during PWM dimming, the base voltage of the transistor 71 forming the differential amplifier circuit decreases and the transistor 71 is turned off, so that the switching element 31 is in the second state. Therefore, the voltage across the switching element 31, that is, the emitter voltage rises. At this time, the base voltage of the switching element 31 also rises to almost the same voltage as the emitter voltage, so that the base current flows through the resistor 77. In order to limit the emitter voltage VE31 in the second state, when the output current is set to the second current value Im which is sufficiently smaller than the first current value (steady load current) in the first mode, the resistance value R77 of the resistor 77 is set. , R77=VE31/(Im/β). As a result, the second current value Im can flow in the semiconductor light source in the second state, and the voltage across the switching element 31 is reduced by causing a voltage drop in the semiconductor light source 2.

  As described above, the impedance adjustment circuit 50 switches the switching element 31 between the first state and the second state in accordance with the output signal S1 of the control circuit 20 during the PWM control, thereby dimming the semiconductor light source 2. The protection operation against overcurrent can be performed.

  Note that the circuit configuration of the overcurrent protection circuit that adds the overcurrent protection function to the switching element 31 for PWM dimming is not limited to the circuit configuration of FIG. It may be configured. For example, in the lighting device 1 shown in FIG. 10, the switching element 31 for PWM dimming is an npn-type transistor, and the operational amplifier circuit is realized by the operational amplifier 79.

  The lighting device 1 shown in FIG. 10 can also realize a protection function against overcurrent by performing the same circuit operation as that of the lighting device 1 shown in FIG.

  In the lighting device 1 shown in FIG. 10, the collector voltage of the switching element 31 increases in the second state in which the output signal S1 becomes low during PWM dimming. When the output current is set to the second current value Im smaller than the first current value (rated load current) in order to limit the collector voltage V31 of the switching element 31 in the second state, the resistance value R76 of the resistor 76 is set to It may be set so that R76=V31/(Im/β). As a result, in the second state, the output current having the second current value Im can be passed through the semiconductor light source 2, and the voltage value applied to the switching element 31 can be reduced due to the voltage drop of the semiconductor light source 2. Since the output of the operational amplifier 79 becomes low in the second state, the diode 80 is connected between the resistor 76 and the output terminal of the operational amplifier 79 so that the current flowing through the resistor 76 does not flow into the operational amplifier 79.

  As described above, the lighting device 1 may further include an overcurrent protection circuit (the impedance adjusting circuit 50 also serves as the overcurrent protection circuit in this embodiment). The overcurrent protection circuit prevents the measured value of the current flowing through the semiconductor light source 2 from exceeding the upper limit current value when the switch unit 30 is in the first state during PWM dimming and full lighting. Adjust the impedance between both ends of.

  This makes it possible to protect the circuit components of the lighting device 1 from overcurrent.

(Embodiment 5)
FIG. 11 shows a circuit diagram of the lighting device 1 of the fifth embodiment. The lighting device 1 of the present embodiment has the same circuit configuration as the lighting device 1 shown in FIG. 7 described in the third embodiment, and the constituent elements common to the lighting device 1 of the third embodiment are the same. Will be assigned and the description thereof will be omitted.

  In the first to fourth embodiments described above, the switching operation of the DC power supply circuit 10 is stopped when the switching element 31 or 32 is set to the second state during PWM dimming. Therefore, the switching element 11 is switched by the AND gate 24 during PWM dimming. The control signal is not input to.

  On the other hand, in the lighting device 1 of the present embodiment, when the switching element 32 is in the second state during the PWM dimming, the high voltage generated across the switching element 32 is detected by the detected value (voltage signal) of the output signal. ) And is input to the output control circuit 21. In the second state, the output control circuit 21 receives the signal obtained by superimposing the high voltage generated across the switching element 32 on the detected value (voltage signal) of the output signal, so that the output current seems to be excessive. In such a state, the output of the DC power supply circuit 10 is suppressed.

  In the lighting device 1 of FIG. 11, the switching element 32 for PWM dimming is an N-channel MOSFET, the cathode of the Zener diode 60 is connected to the drain electrode of the switching element 32, and the anode of the Zener diode 60 is connected to the gate electrode. It is connected. The current sensor 16 outputs a voltage signal proportional to the magnitude of the output current as a measurement signal. In the present embodiment, the addition circuit 82 adds the measurement signal of the current sensor 16 (the signal of the voltage value proportional to the magnitude of the output current) and the voltage of the cathode of the Zener diode 60 (the voltage of the output terminal t5). The generated voltage signal is input to the output control circuit 21.

  In the present embodiment, when the switching element 32 is in the first state during PWM dimming, the impedance of the switching element 32 is sufficiently small and the voltage level of the output terminal t5 is almost zero, so the measurement signal of the current sensor 16 remains unchanged. It is input to the output control circuit 21. On the other hand, when the switching element 32 is in the second state during PWM dimming, the voltage across the switching element 32 rises, the output of the adder circuit 82 increases, and an excessive output current flows to the output control circuit 21. A measurement signal similar to that described above is input. As a result, the output control circuit 21 performs a control operation of stopping the switching operation of the DC power supply circuit 10 or reducing the output voltage of the DC power supply circuit 10.

  FIG. 12 shows a circuit configuration when the resistor 17 is connected instead of the current sensor 16, and the voltage across the resistor 17 is input to the output control circuit 21 via the switching element 32.

  When the switching element 32 is in the first state during PWM dimming, the impedance of the switching element 32 is sufficiently small and the voltage across the switching element 32 becomes substantially zero. Therefore, the measurement signal of the current sensor 16 is directly output to the output control circuit 21. Is entered. On the other hand, when the switching element 32 is in the second state during PWM dimming, the voltage across the switching element 32 rises, so that the output control circuit 21 receives a measurement signal similar to that when an excessive output current flows. Will be entered. As a result, the output control circuit 21 performs a control operation of stopping the switching operation of the DC power supply circuit 10 or reducing the output voltage of the DC power supply circuit 10.

  Further, as shown in FIG. 13, in the second state during PWM dimming, the high voltage generated across the switching element 32 is superimposed on the measured value of the output voltage V2 of the DC power supply circuit 10, and the control circuit 20 is controlled. You may enter it.

  The control circuit 20 includes an overvoltage protection circuit 29 that performs overvoltage protection using the measured value of the output voltage V2 of the DC power supply circuit 10. The control circuit 20 also includes an input voltage monitoring circuit 28 that monitors the input voltage of the DC power supply circuit 10.

  The output of the input voltage monitoring circuit 28, the output of the overvoltage protection circuit 29, and the control signal output from the output control circuit 21 are input to the AND gate 24.

  Therefore, the AND gate 24 outputs the control signal input from the output control circuit 21 to the gate electrode of the switching element 11 only when the input voltage and the output voltage of the DC power supply circuit 10 are within the normal range.

  The overvoltage protection circuit 29 includes a comparator 291 and a constant voltage source 292.

  The inverting input terminal of the comparator 291 is connected to the high-potential-side output terminal of the DC power supply circuit 10 via the resistor 294, and is also connected to the output terminal t5 via the resistor 293. A constant voltage source 292 is connected to the non-inverting input terminal of the comparator 291.

  Here, when the switching element 32 is in the first state during PWM dimming, the voltage of the output terminal t5 becomes the ground level of the circuit, so the voltage obtained by dividing the output voltage V2 of the DC power supply circuit 10 by the resistors 294 and 293. Is input to the inverting input terminal of the comparator 291. In this case, the voltage values of the resistors 294 and 293 are set so that the voltage level of the inverting input terminal falls below the voltage level of the constant voltage source 292, and the output signal of the comparator 291 becomes high. Therefore, the output signal of the output control circuit 21 is input to the switching element 11 of the DC power supply circuit 10, and the DC power supply circuit 10 continues the switching operation.

  At this time, the open-circuit failure of the semiconductor light source 2 or the dropout from the output terminal occurs, the output voltage V2 of the DC power supply circuit 10 rises, and the voltage level of the inverting input terminal of the comparator 29 becomes the voltage level of the constant voltage source 292. Above, the output of comparator 29 goes low. As a result, the output of the AND gate 24 becomes low, and the control signal S2 is not input to the gate electrode of the switching element 11, so that the DC power supply circuit 10 stops the switching operation and the overvoltage generated in the output voltage V2 can be suppressed. .

  On the other hand, when the switching element 32 is in the second state during PWM dimming, the voltage obtained by dividing the output voltage V2 of the DC power supply circuit 10 and the voltage generated across the switching element 32 by the resistors 294 and 293 is the comparator. It is input to the inverting input terminal of 291. In the second state, the voltage across the switching element 32 rises and the voltage level divided by the resistors 294 and 293 exceeds the voltage level of the constant voltage source 292, so the output of the comparator 291 becomes low, and the DC power supply circuit 10 The control signal is not input to the switching element 11 of. As a result, it is possible to avoid the situation where the DC power supply circuit 10 stops the switching operation and the output voltage of the DC power supply circuit 10 increases too much.

  As described above, if the voltage generated when the switching element 32 is in the second state during PWM dimming is superimposed on the measured value of the output voltage of the DC power supply circuit 10, the switching of the DC power supply circuit 10 is performed. The operation can be stopped or the output voltage V2 can be suppressed.

  As described above, the lighting device 1 may further include a power supply control circuit (the control circuit 20 also serves as the present embodiment). The DC power supply circuit 10 has a voltage conversion circuit (for example, a boost chopper circuit) that performs voltage conversion by switching the power supply voltage input from the DC power supply 100. The power supply control circuit controls the switching operation of the voltage conversion circuit 10 based on the measured value of the output voltage or output current of the DC power supply circuit 10. In the second state during PWM dimming, the power supply control circuit controls the switching operation of the voltage conversion circuit based on the value obtained by superimposing the added value proportional to the voltage across the switch unit 30 on the measured value.

  Since the voltage across the switch unit 30 increases in the second state during PWM dimming, the power supply control circuit performs an operation that suppresses the switching operation of the voltage conversion circuit. Therefore, the output voltage of the DC power supply circuit 10 increases. You can avoid a situation where you do too much.

  Note that the circuit configuration for realizing such a function is not limited to the circuit configurations shown in FIGS. 11, 12, and 13, and any other circuit configuration may be used as long as it is a circuit configuration capable of achieving the same operation. ..

  Further, in the lighting devices 1 of Embodiments 1 to 5, the DC power supply circuit 10 is the boost chopper circuit, but the DC power supply circuit 10 may be a buck-boost chopper, a flyback converter, a forward converter, or the like. That is, the DC power supply circuit 10 outputs the power supplied from the power supply to the inductor element to the load side through the rectifier circuit at least from the inductor element connected in series with the load by intermittently switching the power at a high frequency by the switching element. Any circuit configuration may be used as long as the output voltage is boosted or stepped up or down with respect to the power supply voltage.

  Further, the lighting device 1 of Embodiments 1 to 5 is a step-dimming lighting device that switches from the full lighting state to the dimming lighting state when a predetermined voltage value is applied to the input terminal t2. A lighting device that performs continuous dimming according to a rectangular wave dimming signal input from an optical device or the like may be used.

  Further, the control circuit 20 of the lighting device 1 of the first to fifth embodiments may be realized by an analog circuit or a digital circuit. A part or all of the functions of the control circuit 20 may be digitally controlled by software by a microcomputer.

(Embodiment 6)
FIG. 14: is a schematic block diagram of the illuminating device 200 incorporating the lighting device 1 in any one of Embodiments 1-5.

  The illumination device 200 of the present embodiment is, for example, a headlamp device mounted on the vehicle 300, and an external view of the vehicle 300 in which the illumination device 200 is mounted on the vehicle body 301 is shown in FIG. 15.

  The case 201 of the lighting device 200 includes a box-shaped body 202 having an opening on one side, and a translucent cover 203 attached to the opening of the body 202. The semiconductor light source 2 is housed inside the body 202. The semiconductor light source 2 is mounted on the heat dissipation structure 204, which is made of an aluminum alloy and has a plurality of fins. On the heat dissipation structure 204, a reflecting member 205 that reflects the irradiation light from the semiconductor light source 2 forward is attached. Further, below the body 202, a sub case 209 accommodating the lighting device 1 described in the first to fifth embodiments is attached. The lighting device 1 housed in the sub case 209 and the semiconductor light source 2 are electrically connected via a lead wire 208.

  The input terminals t1 and t2 of the lighting device 1 are connected to the positive electrode of the DC power supply 100 (the battery of the vehicle 300) via the switches 101 and 102, respectively. The input terminal t3 of the lighting device 1 is connected to the negative electrode of the DC power supply 100.

  Here, when the switch 101 is turned on, the lighting device 1 supplies a current to the semiconductor light source 2 to light the semiconductor light source 2. When the switch 102 is off, the lighting device 1 lights the semiconductor light source 2 in the full lighting state, and when the switch 102 is on, the lighting device 1 lights the semiconductor light source 2 in the dimming lighting state.

  As described above, the lighting device 200 according to the present embodiment stores the lighting device 1 according to any one of the first to fifth embodiments, the semiconductor light source 2 that the lighting device 1 lights, and the lighting device 1 and the semiconductor light source 2. And 201.

  In addition, the vehicle 300 of the present embodiment includes a lighting device 200 and a vehicle body 201 to which the lighting device 200 is attached.

  Accordingly, it is possible to provide the lighting device 200 and the vehicle 300 in which the switch unit 30 can be a component having a lower withstand voltage.

  The lighting device 200 is not limited to the lighting device that lights the headlight of the vehicle 300. The lighting device 200 may be a lighting device that lights a daytime running lamp or an accessory lamp. In that case, depending on the environment such as lighting or extinguishing other light sources or the environment such as the ambient brightness, the all lighting state and It suffices to switch to one of the dimming lighting states.

1 Lighting device 2 Semiconductor light source 10 DC power supply circuit (voltage conversion circuit)
20 Control circuit (dimming control circuit, overcurrent protection circuit, power supply control circuit)
30 switch part 31,32 switching element 33,40 bypass circuit 34 resistance 50 impedance adjustment circuit 200 lighting device 201 case 300 vehicle body 301 vehicle

Claims (12)

A DC power supply circuit for outputting a DC voltage, a switch unit, a dimming control circuit, and a power supply control circuit ,
The switch unit is connected in series with the semiconductor light source between the output terminals of the DC power supply circuit,
The switch unit is switched between a first state in which a current having a first current value is applied to the semiconductor light source and a second state in which a current having a second current value smaller than the first current value is applied to the semiconductor light source,
The dimming control circuit alternately switches the state of the switch unit between the first state and the second state, and adjusts a duty ratio, which is a temporal ratio between the first state and the second state. It is configured to PWM dimming the semiconductor light source ,
The DC power supply circuit has a voltage conversion circuit that performs voltage conversion by switching a power supply voltage input from a DC power supply,
The power supply control circuit controls the switching operation of the voltage conversion circuit,
The lighting device , wherein the power supply control circuit controls the voltage conversion circuit so as to stop the switching operation in the second state during PWM dimming . Further equipped with an impedance adjustment circuit,
The switch unit has a switching element connected between the output terminals of the DC power supply circuit via the semiconductor light source,
The switching element has a control terminal whose impedance can be adjusted,
The impedance adjustment circuit adjusts the signal input to the control terminal in the second state during PWM dimming to adjust the impedance of the switching element so that the current value of the current flowing through the semiconductor light source is the second value. The lighting device according to claim 1, wherein the lighting device is adjusted to have an impedance that provides a current value.   The lighting device according to claim 2, wherein a withstand voltage of the switching element is lower than a rated load voltage applied to the semiconductor light source. The switch unit has a switching element connected between the output terminals of the DC power supply circuit via the semiconductor light source, and a bypass circuit,
The bypass circuit has an impedance such that a current value of a current flowing through the semiconductor light source is the second current value,
The lighting device according to claim 1, wherein the bypass circuit is connected in parallel with the switching element in the second state during PWM dimming.   In the second state during PWM dimming, the impedance adjustment circuit does not exceed an upper limit voltage value lower than the withstand voltage of the switching element, the measurement value obtained by directly or equivalently measuring the voltage across the switching element. The lighting device according to claim 2, wherein the impedance between both ends of the switching element is adjusted as described above. Further equipped with an overcurrent protection circuit,
The overcurrent protection circuit prevents the measured value of the current flowing through the semiconductor light source from exceeding the upper limit current value when the switch unit is in the first state during PWM dimming and full lighting. The lighting device according to claim 1, wherein impedance between both ends of the switch portion is adjusted.   A DC power supply circuit for outputting a DC voltage, a switch unit, a dimming control circuit, and a power supply control circuit,
  The switch unit is connected in series with the semiconductor light source between the output terminals of the DC power supply circuit,
  The switch unit is switched between a first state in which a current having a first current value is applied to the semiconductor light source and a second state in which a current having a second current value smaller than the first current value is applied to the semiconductor light source,
  The dimming control circuit alternately switches the state of the switch unit between the first state and the second state, and adjusts a duty ratio, which is a temporal ratio between the first state and the second state. It is configured to PWM dimming the semiconductor light source,
  The DC power supply circuit has a voltage conversion circuit that performs voltage conversion by switching a power supply voltage input from a DC power supply,
  The power supply control circuit controls the switching operation of the voltage conversion circuit based on the measured value of the output voltage or the output current of the DC power supply circuit,
  In the second state at the time of PWM dimming, the power supply control circuit sets a value obtained by superimposing an addition value proportional to the voltage across the switch unit on the measured value of the output voltage or the output current of the DC power supply circuit. A lighting device characterized by controlling the switching operation of the voltage conversion circuit based on the above.   Further equipped with an impedance adjustment circuit,
  The switch unit has a switching element connected between the output terminals of the DC power supply circuit via the semiconductor light source,
  The switching element has a control terminal whose impedance can be adjusted,
  The impedance adjustment circuit adjusts the signal input to the control terminal in the second state during PWM dimming to adjust the impedance of the switching element so that the current value of the current flowing through the semiconductor light source is the second value. The lighting device according to claim 7, wherein the impedance is adjusted to a current value.   The switch unit has a switching element connected between the output terminals of the DC power supply circuit via the semiconductor light source, and a bypass circuit,
  The bypass circuit has an impedance such that a current value of a current flowing through the semiconductor light source is the second current value,
  The lighting device according to claim 7, wherein the bypass circuit is connected in parallel with the switching element in the second state during PWM dimming.   Further equipped with an overcurrent protection circuit,
  The overcurrent protection circuit prevents the measured value of the current flowing through the semiconductor light source from exceeding the upper limit current value when the switch unit is in the first state during PWM dimming and full lighting. The lighting device according to claim 7, wherein impedance between both ends of the switch portion is adjusted.   An illumination device comprising: the lighting device according to any one of claims 1 to 10, the semiconductor light source to be turned on by the lighting device, and a case that houses the lighting device and the semiconductor light source. ..   A vehicle comprising: the lighting device according to claim 11; and a vehicle body to which the lighting device is attached.

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