JP2014146423A - Current bypass circuit, illumination light source, and illuminating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a current bypass circuit for a light-emitting element capable of reducing temperature rise of the light-emitting element.SOLUTION: A current bypass circuit 50 used for light emission of a light-emission part 2 emitting light by a drive current supplied from a power supply, is connected in parallel to the light-emission part 2, and comprises a thermistor PTC1. When a temperature of the thermistor PTC1 is at a first temperature, a current having a first current value is introduced from the drive current. When the temperature of the thermistor PTC1 is at a second temperature higher than the first temperature, a current of a second current value larger than the first current value is introduced from the drive current.

Description

  The present invention relates to a current bypass circuit used at the time of light emission of a light emitting element, and an illumination light source and an illumination device including the current bypass circuit.

  Light emitting diodes (LEDs) are expected to be a new light source in various devices such as fluorescent lamps and incandescent lamps such as incandescent lamps, because of their high efficiency and long life. Research and development of an illumination light source using this LED is underway. Along with this, development of a drive circuit for driving the LED is also underway (see, for example, Patent Document 1).

JP 2010-86943 A

  However, in such an illuminating device using a light emitting diode, it is desired to reduce an increase in temperature caused by heat generation of the light emitting diode. Such a rise in temperature causes deterioration of the lighting device, so that the life of the lighting device is shortened.

  In view of the above, an object of the present invention is to provide a current bypass circuit that can reduce an increase in temperature when the light emitting element emits light.

  In order to achieve the above object, a current bypass circuit according to an aspect of the present invention is a current bypass circuit used at the time of light emission of a light emitting unit that emits light by a driving current supplied from a power supply, and is parallel to the light emitting unit. A thermistor is connected, and when the temperature of the thermistor is a first temperature, a current of a first current value is drawn from the drive current, and when the temperature of the thermistor is a second temperature higher than the first temperature, A current having a second current value larger than the first current value is drawn from the drive current.

  For example, it further includes a switching element connected in parallel to the light emitting unit and connected to the thermistor at a control terminal. When the temperature of the thermistor is the first temperature, the switching element is turned off, and the thermistor When the temperature of the second current value is the second temperature, the current of the second current value may be drawn from the drive current by turning on the switching element.

  For example, it further includes a first resistor whose one end is connected to the drain of the switching element, and a second resistor whose one end is connected to one end of the thermistor and the gate which is the control terminal of the switching element, One of the other end of the second resistor and the other end of the thermistor is connected to an anode of the light emitting unit, and the other end of the second resistor and the other end of the thermistor are connected to the light emitting unit. One of the other end of the first resistor and the source of the switching element is connected to the anode of the light emitting unit, and the other end of the first resistor and the source of the switching element. The other may be connected to the cathode of the light emitting unit.

  For example, a first resistor having one end connected to the collector of the switching element, and a second resistor having one end connected to one end of the thermistor and the base that is the control terminal of the switching element, One of the other end of the second resistor and the other end of the thermistor is connected to an anode of the light emitting unit, and the other end of the second resistor and the other end of the thermistor are connected to the light emitting unit. One of the other end of the first resistor and the emitter of the switching element is connected to the anode of the light emitting unit, and the other end of the first resistor and the emitter of the switching element. The other may be connected to the cathode of the light emitting unit.

  For example, it further includes a resistor having one end connected to one end of the thermistor, and one of the other end of the resistor and the other end of the thermistor is connected to an anode of the light emitting unit, and the other end of the resistor and The other end of the thermistor may be connected to the cathode of the light emitting unit.

  For example, the resistance change rate based on the resistance value at the reference temperature of the thermistor may increase exponentially as the temperature rises when the temperature of the thermistor exceeds a predetermined temperature.

  For example, the thermistor may have a positive temperature characteristic.

  For example, the thermistor may have a negative temperature characteristic.

  An illumination light source according to an aspect of the present invention includes the current bypass circuit according to any one of the above aspects and the light-emitting portion.

  Moreover, the illuminating device which concerns on 1 aspect of this invention is equipped with the current bypass circuit of the said aspect, and the said light emission part.

  According to the current bypass circuit of the present invention, an increase in temperature can be reduced when the light emitting element emits light.

FIG. 1 is a diagram illustrating a circuit configuration of a drive circuit according to the embodiment. FIG. 2 is a diagram illustrating temperature characteristics of the thermistor according to the embodiment. FIG. 3 is a diagram for explaining the operation of the current bypass circuit according to the embodiment. FIG. 4 is a diagram illustrating an example of a circuit configuration of a current bypass circuit using a thermistor having negative temperature characteristics. FIG. 5 is a diagram illustrating an example of a circuit configuration of a current bypass circuit using a bipolar transistor as a switching element. FIG. 6 is a diagram illustrating an example of a circuit configuration of a current bypass circuit using a P-channel FET as a switching element. FIG. 7 is a diagram illustrating an example of a circuit configuration of a current bypass circuit using a P-channel FET as a switching element and a thermistor having negative temperature characteristics. FIG. 8 is a diagram illustrating a circuit configuration of a current bypass circuit that does not include a switching element. FIG. 9 is an external perspective view of the light bulb shaped lamp according to the embodiment. FIG. 10 is a schematic cross-sectional view of the illumination device according to the embodiment.

  Hereinafter, embodiments will be specifically described with reference to the drawings.

  It should be noted that each of the embodiments described below shows a comprehensive or specific example. The numerical values, shapes, materials, constituent elements, arrangement positions and connecting forms of the constituent elements, steps, order of steps, and the like shown in the following embodiments are merely examples, and are not intended to limit the present invention. In addition, among the constituent elements in the following embodiments, constituent elements that are not described in the independent claims indicating the highest concept are described as optional constituent elements.

(Circuit configuration)
First, the circuit configuration of the current bypass circuit according to the present embodiment will be described with reference to FIG. FIG. 1 is a diagram showing a circuit configuration of a drive circuit including a current bypass circuit according to the present embodiment.

  As shown in FIG. 1, the drive circuit 1 according to the present embodiment is an LED drive circuit (LED lighting circuit) for lighting an LED 2, and includes a first rectifier circuit 10, an inverter 20, and an inverter A control circuit 30, a second rectifier circuit 40, and a current bypass circuit 50 are provided.

  The drive circuit 1 has input terminals P1 and P2 for receiving an AC voltage input. The input terminals P <b> 1 and P <b> 2 are connected to an AC power supply and are connected to the input terminal of the first rectifier circuit 10. For example, a commercial AC power supply is connected to the input terminals P1 and P2 of the drive circuit 1 through a wall switch. The commercial AC power source is a commercial 100V AC power source, that is, a home AC power source. Further, the input terminals P1 and P2 are, for example, caps of a light bulb shaped LED lamp attached to a socket to which AC power is supplied.

  The drive circuit 1 has output terminals P3 and P4 for outputting a DC voltage. The output terminals P3 and P4 are connected to the LED 2 and the current bypass circuit 50, and are connected to the output terminal of the second rectifier circuit 40. The output terminal P3 on the high potential side is connected to the anode side of the LED 2, and the output terminal P4 on the low potential side is connected to the cathode side of the LED 2. The LED 2 is lit by a DC voltage supplied from the drive circuit 1.

  Hereinafter, each component of the drive circuit 1 according to the present embodiment will be described in detail.

  First, the first rectifier circuit 10 will be described. The first rectifier circuit 10 (DB1) is a bridge-type full-wave rectifier circuit composed of four diodes. Two terminals on the input side are connected to an AC power source via input terminals P1 and P2, and the output side Are connected to the smoothing capacitor CD1. The smoothing capacitor CD1 is provided to stabilize the output voltage of the first rectifier circuit 10, and is, for example, an electrolytic capacitor. Although an example in which one smoothing capacitor CD1 is used is shown here, one smoothing capacitor is connected between the input terminal P1 and the two output-side terminals of the first rectifier circuit 10. May be.

  A current fuse element FS (56Ω) is inserted in series in the wiring connecting the AC power source and the first rectifier circuit 10. In addition, a noise filter NF (5 mH) for removing switching noise is inserted in the wiring connecting the negative electrode of the voltage output terminal of the first rectifier circuit 10 and the inverter control circuit 30.

  The first rectifier circuit 10 receives an AC voltage (for example, 50 or 60 Hz) from a commercial AC power source through a wall switch, for example, and full-wave rectifies the AC voltage to output a DC voltage. The DC voltage output from the first rectifier circuit 10 is smoothed by the smoothing capacitor CD1 to become a DC input voltage Vin. The input voltage Vin is supplied to the inverter 20 and the inverter control circuit 30.

  Next, the inverter 20 will be described. The inverter 20 outputs electric power for driving the LED 2. In the present embodiment, inverter 20 converts a DC voltage into an AC voltage. For example, the inverter 20 converts a DC voltage into an AC voltage of several tens of kHz.

  The inverter 20 includes a first transistor Q1, a second transistor Q2 connected in series to the first transistor Q1, a drive transformer T1, an inductor L1, capacitors C5, C6 and C8, and a resistor R4. , R5, R6, R7, R8 and R9.

  In the present embodiment, the inverter 20 is a half-bridge self-excited inverter, and a series circuit including a first transistor Q1 and a second transistor Q2 that perform switching operations alternately is connected to a DC power source. It is configured. In the present embodiment, the first transistor Q1 and the second transistor Q2 are bipolar transistors. Note that in this embodiment, a self-excited inverter refers to an inverter to which feedback is applied using a drive transformer and a plurality of switching elements.

  The collector of the first transistor Q1 is connected to the positive electrode of the DC voltage output terminal of the first rectifier circuit 10 and the capacitor C5. The emitter of the first transistor Q1 is connected to the collector of the second transistor Q2 and the coil of the driving transformer T1 via the resistor R6. The base of the first transistor Q1 is connected to the coil of the drive transformer T1 via the resistor R5. The base of the first transistor Q1 is connected to the collector of the second transistor Q2 and the coil of the driving transformer T1 via a resistor R8.

  The collector of the second transistor Q2 is connected to the emitter of the first transistor Q1 and the coil of the driving transformer T1 via a resistor R6. The emitter of the second transistor Q2 is connected to the negative electrode of the DC voltage output terminal of the first rectifier circuit 10, the coil of the drive transformer T1, the capacitor C6, and the capacitor C8 via the resistor R7. . The base of the second transistor Q2 is connected to the coil of the drive transformer T1 via the resistor R4. The base of the second transistor Q2 is connected to the negative electrode of the DC voltage output terminal of the first rectifier circuit 10 via the resistor R9.

  The drive transformer T1 includes a winding coil including a primary winding (input winding) and a secondary winding (output winding).

  The inductor L1 is a choke inductor, and has one end connected to the output side of the drive transformer T1 and the other end connected to the input side of the second rectifier circuit 40. Capacitor C5 has one end connected to the positive electrode of the DC voltage output terminal of first rectifier circuit 10 and the other end connected to the input side of second rectifier circuit 40.

  In the inverter 20 configured as described above, a predetermined input voltage Vin is applied between both ends of the series circuit of the first transistor Q1 and the second transistor Q2 (to the input terminal of the inverter 20), and the inverter control circuit It operates by being supplied with an activation control signal (trigger signal) from 30. Specifically, the first transistor Q1 and the second transistor Q2 are alternately turned on and off by self-excited oscillation based on the induction of the drive transformer T1, so that alternating current due to series resonance between the inductor L1 and the capacitor C5 is generated. A secondary voltage is induced, and this voltage is supplied to the second rectifier circuit 40.

  Next, an inverter control circuit 30 for controlling the inverter 20 will be described. The inverter control circuit 30 is configured to control the operation of the inverter 20. In the present embodiment, inverter control circuit 30 starts the operation of inverter 20 and maintains the operation of inverter 20.

  The inverter control circuit 30 includes a resistor R2, a capacitor C3 connected in series to the resistor R2, and a trigger diode TD connected to a connection point between the resistor R2 and the capacitor C3.

  The resistor R2 is connected to the positive electrode of the DC voltage output terminal of the first rectifier circuit 10 through the resistor R1, and is connected to the negative electrode of the DC voltage output terminal of the first rectifier circuit 10 through the capacitor C3. Has been. The capacitor C3 is a capacitor for controlling the conduction of the trigger diode TD, and the high potential side is connected to the resistor R2, and the low potential side is connected to the negative electrode of the DC voltage output terminal of the first rectifier circuit 10. . In the inverter control circuit 30, the resistor R2 and the capacitor C3 constitute a time constant circuit.

  The trigger diode TD is a trigger element formed of a diode, and becomes conductive when a voltage exceeding a specified voltage (breakover voltage) is applied. In the present embodiment, the trigger diode TD breaks by the voltage value held in the capacitor C3 and becomes conductive. The trigger diode TD is connected to the base of the second transistor Q2, which is the control terminal of the inverter 20, and the operation of the inverter 20 is started when the trigger diode TD is turned on.

  That is, when the second transistor Q2 is turned on by the inverter control circuit 30, current begins to flow through the inverter 20, and the inductor L1, the capacitor C5, the second rectifier circuit 40, the drive transformer T1, the LED2, and the second transistor Q2 Current flows in the order of. Then, the voltages generated at the bases of the first transistor Q1 and the second transistor Q2 are inverted at the resonance frequency (50 kHz) by the resonance of the inductor L1, the capacitor C5, and the drive transformer T1. Thereby, a steady operation in which the first transistor Q1 and the second transistor Q2 are alternately turned on and off is started.

  As the trigger diode TD, for example, a diac having a voltage breakover of 28 to 36 V can be used.

  Thus, the inverter control circuit 30 is a circuit for starting the inverter 20, and includes a time constant circuit including the resistor R2 and the capacitor C3, and the trigger diode TD that breaks over according to the voltage value of the capacitor C3. . Then, when a trigger signal is input from the inverter control circuit 30 to the inverter 20, self-oscillation of the inverter 20 starts.

  Further, in the present embodiment, the inverter control circuit 30 includes a resistor R1 connected in series to the resistor R2, a capacitor C4 connected in parallel to the resistor R2, and a diode D5 connected in parallel to the resistor R2. , Diodes D6 and D7.

  The diode D5 is a rectifying diode. The anode of the diode D5 is connected to the connection point between the resistor R2 and the capacitor C3 and the trigger diode TD. The cathode of the diode D5 is connected to the connection point between the resistors R1 and R2, the connection point between the first transistor Q1 (emitter) and the second transistor Q2 (collector) in the inverter 20, and the capacitor C4. It is connected. The capacitor C4 has a high potential side connected to the positive electrode of the DC voltage output terminal of the first rectifier circuit 10 and the collector of the first transistor Q1, and a low potential side connected to the cathode of the diode D5. The capacitor C4 is a soft switching capacitor, and is used as appropriate to suppress the generation of noise accompanying switching.

  The diode D6 is a rectifying diode. The diode D6 is connected in parallel with the capacitor C4 and the resistor R1. The anode of the diode D6 is connected to the low potential side of the capacitor C4, and the cathode of the diode D6 is connected to the high potential side of the capacitor C4.

  The diode D7 is a rectifying diode. The anode of the diode D7 is connected to the connection point between the resistor R7 and the capacitor C3. The cathode of the diode D7 is a connection point between the resistors R1 and R2, a connection point between the first transistor Q1 (emitter) and the second transistor Q2 (collector) in the inverter 20, a capacitor C4, and a diode. Connected to the anode of D6.

  Next, the second rectifier circuit 40 will be described. Similarly to the first rectifier circuit 10, the second rectifier circuit 40 (DB2) is a bridge-type full-wave rectifier circuit composed of four diodes, and two terminals on the input side are the output side of the inverter 20. The high potential side of the two output side terminals is connected to the anode side of the current bypass circuit 50, and the low potential side is connected to the cathode side of the current bypass circuit 50. As for the two terminals on the output side, the high potential side is connected to the anode side of the LED 2 via the output terminal P3, and the low potential side is connected to the cathode side of the LED 2 via the output terminal P4.

  One of the two terminals on the input side is connected to the negative electrode of the DC voltage output terminal of the first rectifier circuit 10 via the capacitor C6, and the other of the two terminals on the input side is connected to the first terminal via the capacitor C8. The rectifier circuit 10 is connected to the negative electrode of the DC voltage output terminal.

  The second rectifier circuit 40 receives the AC voltage from the inverter 20, outputs a voltage obtained by full-wave rectification of the AC voltage, and supplies the voltage to the LED 2.

  Note that the second rectifier circuit 40 can be configured, for example, by combining two semiconductor components in which two Schottky diodes are connected in series.

  Two terminals on the output side of the inverter 20 are connected to the smoothing capacitor CD2. The smoothing capacitor CD2 is provided to stabilize the output voltage of the second rectifier circuit 40, and is, for example, an electrolytic capacitor.

  The drive circuit 1 according to the present embodiment is configured as described above.

  The inverter 20, the inverter control circuit 30, and the second rectifier circuit 40 are circuits that are provided to prevent the LED 2 from flickering, and are not necessarily required circuits.

  Further, in the present embodiment, one LED 2 which is an example of a light emitting unit (light emitting element) is turned on by the drive circuit 1, but a plurality of LEDs 2 may be provided as the light emitting unit. In this case, the plurality of LEDs 2 may be connected in series, may be connected in parallel, or the plurality of LEDs 2 may be configured by combining series connection and parallel connection.

(Circuit configuration of current bypass circuit)
Next, the current bypass circuit 50 according to the present embodiment will be described.

  The current bypass circuit 50 includes a thermistor PTC1 connected in parallel to the LED 2, a resistor R10 (first resistor), a switching element Q3, and a resistor R11 (second resistor).

  The thermistor PTC1 has a predetermined temperature characteristic as will be described later. One end of the thermistor PTC1 is connected to the gate of the switching element Q3 and one end of the resistor R11. The other end of the thermistor PTC1 is the source of the switching element Q3, the cathode of the LED 2 (terminal on the cathode side of the light emitting element), and the output terminal. Connected to P4.

  One end of the resistor R10 is connected to the drain of the switching element Q3. The other end of the resistor R10 is connected to the anode (the terminal on the anode side of the light emitting element) of the LED 2, the other end of the resistor R11, and the output terminal P3.

  The switching element Q3 is an n-channel FET (Field Effect Transistor). The drain of the switching element Q3 is connected to one end of the resistor R10. The source of the switching element Q3 is connected to the cathode of the LED 2, the other end of the thermistor PTC1, and the output terminal P4. The gate of the switching element Q3 is connected to one end of the thermistor PTC1 and one end of the resistor R11.

  One end of the resistor R11 is connected to the gate of the switching element Q3 and one end of the thermistor PTC1. The other end of the resistor R11 is connected to the other end of the resistor R10, the anode of the LED 2, and the output terminal P3.

  In the present embodiment, the resistance value of the resistor R10 is 2.2 kΩ, and the resistance value of the resistor R11 is 50 kΩ. The thermistor PTC1 has a resistance value of about 1.8 kΩ at 25 ° C. and has a predetermined temperature characteristic.

  FIG. 2 is a diagram illustrating temperature characteristics of the thermistor PTC1 according to the present embodiment. The horizontal axis in FIG. 2 is the environmental temperature, and the vertical axis is the logarithmic change rate of the resistance value. Here, the rate of change of the resistance value is a value obtained by dividing the resistance value (R) at each environmental temperature by the resistance value (R25) at an environmental temperature of 25 ° C.

  As shown in FIG. 2, the rate of change of the resistance value of the thermistor PTC1 is 2 or less in a predetermined temperature section (around −40 ° C. to + 90 ° C.), but increases rapidly from the vicinity of over 90 ° C. Has characteristics. That is, after exceeding a predetermined temperature interval, the resistance change rate increases rapidly as the temperature increases. In the example of FIG. 2, since the vertical axis is logarithmic, the resistance change rate increases exponentially after exceeding a predetermined temperature interval.

  The current bypass circuit 50 is characterized by the operation of drawing a part of the drive current of the LED 2 at a high temperature by using the temperature dependency of the thermistor PTC1 with the circuit configuration as described above. Details of this operation will be described later.

(Circuit operation)
Next, the operation of the drive circuit 1 according to the present embodiment will be described.

  For example, when the user turns on the wall switch to turn on the LED 2, AC power is supplied to the input terminals P <b> 1 and P <b> 2, and the DC input voltage Vin smoothed by the first rectifier circuit 10 is generated. The input voltage Vin is supplied between the input terminals of the inverter 20 and between the input terminals of the inverter control circuit 30.

  Thereby, the inverter control circuit 30 and the inverter 20 operate | move. That is, when the input voltage Vin is supplied to the inverter control circuit 30, the capacitor C3 of the inverter control circuit 30 is charged, and the trigger diode TD breaks over. As a result, the trigger diode TD becomes conductive, a trigger signal (trigger pulse) is supplied to the base of the second switching element Q2 of the inverter 20, and the second switching element Q2 is turned on.

  When the second switching element Q2 is turned on by the trigger signal, the inverter 20 is activated, and the first switching element Q1 and the second switching element Q2 are alternately turned on and off by self-excited oscillation based on induction of the drive transformer T1. An alternating secondary voltage is induced. As a result, an AC voltage in which the secondary voltage is increased by the series resonance of the inductor L1 and the capacitor C5 is supplied to the second rectifier circuit 40. Then, the AC voltage is full-wave rectified by the second rectifier circuit 40, and a predetermined DC voltage (forward voltage VF) is supplied to the LED 2 via the output terminals P3 and P4. Thereby, LED2 lights with desired brightness.

  When the user turns off the wall switch to turn off the LED 2, the supply of AC power to the input terminals P1 and P2 is stopped, so that the LED 2 is turned off.

(Operation of current bypass circuit)
Next, the operation of the current bypass circuit 50 will be described.

  A light emitting element such as LED 2 tends to have a shortened life when light is emitted at a high temperature. For this reason, when the temperature exceeds a predetermined upper limit value, the current bypass circuit 50 actively draws a part of the drive current of the LED 2. Thereby, under the environment where the predetermined upper limit value is exceeded, the current flowing through the LED 2 is reduced, and the temperature rise of the LED 2 can be reduced.

  In the present embodiment, the predetermined upper limit value is the ambient temperature around the thermistor PTC1 when the junction temperature of the LED 2 is 122 ° C.

  FIG. 3 is a diagram for explaining the operation of the current bypass circuit 50. In the following description, it is assumed that the power (voltage Vop, drive current Iop) supplied from the second rectifier circuit 40 is constant regardless of the temperature. The circuit preceding the second rectifier circuit 40 operates as a substantially constant current source.

  FIG. 3A is a diagram schematically showing a current flow when the temperature is lower than a predetermined upper limit value (during normal operation).

  During normal operation, current I1 flows through resistor R11 and thermistor PTC1, and current IL flows through LED2. Here, when the resistance value of the resistor R11 is expressed as R11 and the resistance value of the thermistor PTC1 is expressed as PTC1, the gate-source voltage Vgs of the switching element Q3 is expressed by Vgs = Vop × PTC1 / (R11 + PTC1).

  During normal operation, the threshold voltage of switching element Q3 (the voltage at which switching element Q3 is turned on) Vth> Vgs is designed. Specifically, as described above, the resistance value of the resistor R11 is 50 kΩ, and the resistance value of the thermistor PTC1 is about 1.8 kΩ. Accordingly, during the normal operation, the switching element Q3 is in the OFF state, so that no current flows through the resistor R10.

  From the above, the current drawn by the current bypass circuit 50 during normal operation is I1 = Vop / (R11 + PTC1). Note that the resistance values of the resistor R11 and the thermistor PTC1 are much larger than the resistance value of the LED 2 in the forward direction, so that the current I1 << current IL. That is, most of the drive current Iop flows through the LED 2.

  FIG. 3B is a diagram schematically showing a current flow when the temperature is equal to or higher than a predetermined upper limit value (during high temperature operation).

  During a high temperature operation, the resistance value of the thermistor PTC1 increases and Vth <Vgs. Therefore, during the high temperature operation, the switching element Q3 is turned on, and the current I2 flows through the resistor R10. That is, the total current drawn by the current bypass circuit 50 during high-temperature operation is I1 + I2 = Vop / (R11 + PTC1) + Vop / R10. In the present embodiment, when the temperature is near a predetermined upper limit value, about 20% of the drive current Iop is drawn into the current bypass circuit 50.

  Thus, the current bypass circuit 50 draws more current during high temperature operation than during normal operation. Therefore, during the high temperature operation, the current IL flowing through the LED 2 is reduced as compared with the normal operation. As a result, during high temperature operation, the amount of heat generated by the LED 2 is reduced as compared with the case where the current bypass circuit 50 is not provided, so that the ambient temperature of the LED 2 can be lowered. Accordingly, the life of the LED 2 is extended.

  Further, as described above, the thermistor PTC1 has a characteristic in which a change in resistance value is small in a predetermined temperature section, and the resistance value rapidly increases after exceeding the predetermined temperature section. Thereby, in the predetermined temperature section, since the current bypass circuit 50 operates as in the normal operation, the change in the luminance of the LED 2 is small. That is, due to such characteristics, the uncomfortable feeling given to the user by the change in the luminance of the LED 2 in the predetermined temperature section can be reduced.

  As described above, the current bypass circuit 50 according to the present embodiment is the current bypass circuit 50 that is used when the LED 2 (light emitting unit) that emits light by the driving current Iop supplied from the power source emits light, and is parallel to the LED 2. And thermistor PTC1 is provided, and when the temperature of the thermistor PTC1 is the first temperature (during normal operation), the current of the first current value is drawn from the drive current Iop, and the temperature of the thermistor PTC1 is higher than the first temperature. At 2 temperatures (during high temperature operation), a current having a second current value larger than the first current value is drawn from the drive current Iop. Here, the first current value includes 0A.

  According to the current bypass circuit 50, a part of the drive current Iop is consumed (bypassed) in the current bypass circuit 50. Therefore, the current flowing through the LED 2 at a high temperature can be reduced and the temperature of the LED 2 can be lowered. Accordingly, the life of the LED 2 and the lighting device using the LED 2 can be extended.

(Modification)
The current bypass circuit of the present invention is not limited to the above embodiment.

  For example, in the above embodiment, the thermistor has a predetermined characteristic as shown in FIG. 2, but FIG. 2 is a diagram showing an example of the temperature characteristic of the thermistor. It is not limited to the characteristics. The resistance value of the thermistor PTC1 may be any resistance value that turns on the switching element Q3 when at least the temperature is equal to or higher than the predetermined upper limit value. That is, in the current bypass circuit 50, the temperature characteristic of the thermistor PTC1 may be a positive temperature characteristic in which the resistance value increases with increasing temperature from room temperature.

  The temperature characteristic of the thermistor may be a negative temperature characteristic in which the resistance value decreases as the temperature rises from at least room temperature.

  FIG. 4 is a diagram illustrating an example of a circuit configuration of a current bypass circuit 50a using a thermistor having negative temperature characteristics.

  The current bypass circuit 50a is different from the current bypass circuit 50 in that a thermistor NTC1 having a negative temperature characteristic and a resistor R12 are connected in series at a location where the resistor R11 and the thermistor PTC1 are connected in series.

  The thermistor NTC1 has negative temperature characteristics as described above. One end of the thermistor NTC1 is connected to the gate of the switching element Q3 and one end of the resistor R12. The other end of the thermistor NTC1 is connected to the other end of the resistor R10, the anode of the LED 2, and the output terminal P3.

  One end of the resistor R12 is connected to the gate of the switching element Q3 and one end of the thermistor PTC1. The other end of the resistor R12 is connected to the source of the switching element Q3, the cathode of the LED 2, and the output terminal P4.

  During normal operation, the resistance value of the thermistor NTC1 is greater than the resistance value of the resistor R12 so that the threshold voltage of the switching element Q3 (the voltage at which the switching element Q3 is turned on) Vth> Vgs. Yes. Accordingly, during the normal operation, the switching element Q3 is in the OFF state, so that no current flows through the resistor R10.

  During high temperature operation, the resistance value of the thermistor NTC1 decreases, and the resistance value of the resistor R12 increases relative to the resistance value of the thermistor NTC1. Thereby, Vth <Vgs. Therefore, at the time of high temperature operation, switching element Q3 is turned on, and a part of drive current Iop is actively drawn into current bypass circuit 50a.

  Therefore, even when the current bypass circuit 50a is used, the ambient temperature of the LED 2 can be lowered during the high temperature operation because the current IL flowing through the LED 2 is reduced compared with the normal operation and the amount of heat generated by the LED 2 is reduced.

  The thermistor NTC1 desirably has a characteristic that the rate of change of the resistance value is small in a predetermined temperature section, and the resistance value rapidly decreases after exceeding the predetermined temperature section. This is because the change in the luminance of the LED 2 can be reduced in the predetermined temperature section.

  In the above embodiment, the n-channel FET is used as the switching element Q3. However, the switching element Q3 is not limited to the FET.

  FIG. 5 is a diagram illustrating an example of a circuit configuration of a current bypass circuit 50b using a bipolar transistor as a switching element.

  In FIG. 5, the switching element Q4 is an npn-type bipolar transistor. The collector of the switching element Q4 is connected to one end of the resistor R10. The emitter of the switching element Q4 is connected to the cathode of the LED 2, the other end of the thermistor PTC1, and the output terminal P4. The base of the switching element Q4 is connected to one end of the thermistor PTC1 and one end of the resistor R11.

  During normal operation, the threshold voltage Vth> Vgs of the switching element Q4 is satisfied, and the switching element Q4 is in the OFF state. During a high temperature operation, the resistance value of the thermistor PTC1 increases, Vth <Vgs, and the switching element Q4 is turned on.

  Therefore, the current bypass circuit 50b can achieve the same effect as the current bypass circuit 50.

  Further, a current bypass circuit may be realized using a P-channel FET as a switching element.

  FIG. 6 is a diagram illustrating an example of a circuit configuration of a current bypass circuit 50c using a P-channel FET as a switching element.

  The current bypass circuit 50c includes a thermistor PTC2, which is connected in parallel to the LED 2, a resistor R13, a switching element Q5, and a resistor R14.

  The thermistor PTC2 has a positive temperature characteristic like the thermistor PTC1. One end of the thermistor PTC2 is connected to the gate of the switching element Q5 and one end of the resistor R14, and the other end of the thermistor PTC2 is connected to the source of the switching element Q5, the anode of the LED2, and the output terminal P3.

  One end of the resistor R13 is connected to the drain of the switching element Q5. The other end of the resistor R13 is connected to the cathode of the LED 2, the other end of the resistor R14, and the output terminal P4.

  The switching element Q5 is a p-channel FET. The drain of the switching element Q5 is connected to one end of the resistor R13. The source of the switching element Q5 is connected to the anode of the LED 2, the other end of the thermistor PTC2, and the output terminal P3. The gate of the switching element Q5 is connected to one end of the thermistor PTC2 and one end of the resistor R14.

  One end of the resistor R14 is connected to the gate of the switching element Q5 and one end of the thermistor PTC2. The other end of the resistor R14 is connected to the other end of the resistor R13, the cathode of the LED 2, and the output terminal P4.

  During normal operation, the resistance value of the thermistor PTC <b> 2 <the resistance value of the resistor R <b> 14 so that the threshold voltage of the switching element Q <b> 5 (the voltage at which the switching element Q <b> 5 is turned on) Vth> Vgs. Yes. Accordingly, during the normal operation, the switching element Q5 is in the OFF state, so that no current flows through the resistor R13.

  During a high temperature operation, the resistance value of the thermistor PTC2 increases and the resistance value of the resistor R12 decreases relative to the resistance value of the thermistor PTC2. Thereby, Vth <Vgs. Therefore, during high temperature operation, switching element Q5 is turned on, and a part of drive current Iop is drawn into current bypass circuit 50c.

  Therefore, the current bypass circuit 50c can achieve the same effect as the current bypass circuit 50.

  As shown in FIG. 7, a circuit configuration using a p-channel FET (switching element Q6) and a thermistor having negative temperature characteristics (thermistor NTC2) may be used. Alternatively, a configuration using a pnp bipolar transistor may be used.

  Moreover, the structure which is not provided with a switching element may be sufficient.

  FIG. 8 is a diagram illustrating a circuit configuration of a current bypass circuit 50e that does not include a switching element.

  The current bypass circuit 50e includes a thermistor NTC3 connected in parallel to the LED 2 and a resistor R16.

  The thermistor NTC3 has negative temperature characteristics. One end of the thermistor NTC3 is connected to one end of the resistor R16, and the other end of the thermistor NTC3 is connected to the anode of the LED 2 and the output terminal P3.

  One end of the resistor R16 is connected to one end of the thermistor NTC3. The other end of the resistor R16 is connected to the cathode of the LED 2 and the output terminal P4.

  In such a circuit, since the resistance value of the thermistor NTC3 decreases as the temperature rises, the current value of the current drawn by the current bypass circuit 50e becomes larger during high temperature operation than during normal operation. That is, the current bypass circuit 50e can achieve the same effect as the current bypass circuit 50.

  The thermistor NTC3 desirably has a characteristic that the rate of change of the resistance value is small in a predetermined temperature section, and the resistance value rapidly decreases after exceeding the predetermined temperature section.

  Thus, by using an inexpensive thermistor and resistor without using a switching element, a current bypass circuit capable of reducing the ambient temperature at a low cost can be realized.

  Further, only the thermistor NTC3 may be connected to the LED 2 in parallel, thereby realizing a current bypass circuit capable of reducing the ambient temperature at a lower cost.

(Light source for lighting)
Next, application examples of the current bypass circuit (current bypass circuits 50 and 50a to 50e) according to the present embodiment will be described. FIG. 9 is an external perspective view of a light bulb shaped lamp 100 that is an illumination light source (LED light source) according to the present embodiment.

  The current bypass circuit according to the present embodiment is applied to a drive circuit, and the drive circuit can be used as an LED light source together with the LED 2 that is turned on. In addition, the LED light source in this Embodiment means the apparatus which mounts LED lighted by arbitrary drive circuits. Examples of LED light sources include not only devices combining LEDs and drive circuits, but also various lighting devices such as lighting devices that replace conventional bulb-type fluorescent lamps, and halogen bulb-substituting lighting devices. Including.

  As shown in FIG. 9, a light bulb shaped lamp 100 according to the present embodiment is a light bulb shaped lamp that is a substitute for a light bulb shaped fluorescent light or an incandescent light bulb, and includes a globe 110, an LED module 120 that is a light source, A support 130, a support member 140, an outer casing 180, and a base 190 are provided.

  The bulb-shaped lamp 100 includes an envelope made up of the globe 110, the outer casing 180, and the base 190.

  The globe 110 is a substantially hemispherical translucent cover for taking out the light emitted from the LED module 120 to the outside of the lamp. Globe 110 in the present embodiment is a glass bulb (clear bulb) made of silica glass that is transparent to visible light. Therefore, the LED module 120 housed in the globe 110 can be viewed from the outside of the globe 110.

  The LED module 120 is covered with a globe 110. Thereby, the light of the LED module 120 incident on the inner surface of the globe 110 passes through the globe 110 and is extracted to the outside of the globe 110. In the present embodiment, the globe 110 is configured to house the LED module 120.

  The shape of the globe 110 is a shape in which one end is closed in a spherical shape and an opening is provided at the other end. Specifically, the shape of the globe 110 is such that a part of a hollow sphere narrows while extending away from the center of the sphere, and an opening is formed at a position away from the center of the sphere. Has been. As the globe 110 having such a shape, a glass bulb having a shape similar to that of a general bulb-type fluorescent lamp or an incandescent bulb can be used. For example, a glass bulb such as an A shape, a G shape, or an E shape can be used as the globe 110.

  Further, the opening of the globe 110 is placed on the surface of the support member 140. In this state, the globe 110 is fixed by applying an adhesive such as silicone resin between the support member 140 and the outer casing 180.

  Note that the globe 110 is not necessarily transparent to visible light, and the globe 110 may have a light diffusion function. For example, a milky white light diffusion film can be formed by applying a resin containing a light diffusing material such as silica or calcium carbonate, or a white pigment or the like to the entire inner surface or outer surface of the globe 110. Thus, by providing the globe 110 with a light diffusion function, light incident on the globe 110 from the LED module 120 can be diffused, so that the light distribution angle of the lamp can be expanded.

  Further, the shape of the globe 110 is not limited to the A shape or the like, and may be a spheroid or an oblate ball. The material of the globe 110 is not limited to a glass material, and a resin such as acrylic (PMMA) or polycarbonate (PC) may be used.

  The LED module 120 is a light emitting module having a light emitting element (LED2), and emits light of a predetermined color (wavelength) such as white. The LED module 120 is held hollow in the globe 110 by the support column 130 and emits light by electric power supplied from the drive circuit 1 or 1A via the lead wires 153a and 153b.

  The column 130 is a long member that extends from the vicinity of the opening of the globe 110 toward the inside of the globe 110. The column 130 functions as a support member that supports the LED module 120, and the LED module 120 is connected to one end of the column 130. On the other hand, a support member 140 is connected to the other end of the column 130.

  The support member 140 is a support base that supports the column 130.

  The outer casing 180 is an outer member. In addition, a drive circuit (current bypass circuit) is disposed inside the outer casing 180.

  The base 190 is a power receiving unit that receives power for causing the LED module 120 (LED2) to emit light from the outside of the lamp. The base 190 is attached to a socket of a lighting fixture, for example. Thereby, the base 190 can receive electric power from the socket of the lighting fixture when the light bulb shaped lamp 100 is turned on. AC power is supplied to the base 190 from, for example, a commercial power supply of AC 100V. The base 190 in the present embodiment receives AC power through two contact points, and the power received by the base 190 is input to the drive circuit. The type of the base 190 is not particularly limited, but in this embodiment, a screwed type Edison type (E type) base is used. For example, the base 190 is of E26 type, E17 type, E16 type, or the like.

  Although an example in which the illumination light source is a light bulb-type LED lamp is shown here, the drive circuit (current bypass circuit) can also be applied to illumination light sources of other shapes such as a straight tube LED lamp. .

(Lighting device)
In addition, the present invention can be realized not only as an illumination light source (bulb-shaped lamp 100) but also as an illumination device including an illumination light source. Hereinafter, lighting device 200 according to the present embodiment will be described with reference to FIG. FIG. 10 is a schematic cross-sectional view of the illumination device 200 according to the embodiment of the present invention.

  As shown in FIG. 10, lighting device 200 according to the present embodiment is used by being mounted on a ceiling in a room, for example, and includes light bulb shaped lamp 100 according to the above-described embodiment and lighting fixture 203.

  The lighting device 203 turns off and turns on the light bulb shaped lamp 100 and includes a device main body 204 attached to the ceiling and a translucent lamp cover 205 that covers the light bulb shaped lamp 100.

  The instrument body 204 has a socket 204a. A base 190 of the light bulb shaped lamp 100 is screwed into the socket 204a. Electric power is supplied to the light bulb shaped lamp 100 through the socket 204a.

  In the above description, the example in which the current bypass circuit according to the present embodiment is mounted on the light bulb shaped lamp 100 as a part of the drive circuit has been described. However, the current bypass circuit according to the present embodiment is not limited to the drive circuit. The LED module 120 or the lighting device 203 may be included separately.

  The current bypass circuit, the light source for illumination, and the illumination device according to the embodiment of the present invention have been described above, but the present invention is not limited to this embodiment.

  For example, in the above description, an example using FETs and bipolar transistors has been described, but other types of transistors such as MOS transistors may be used.

  In the above embodiment, the LED is exemplified as the light emitting element. However, a semiconductor light emitting element such as a semiconductor laser, a solid light emitting element such as an organic EL (Electro Luminescence), or an inorganic EL may be used as the light emitting element.

  Moreover, all the numbers used above are illustrated for specifically explaining the present invention, and the present invention is not limited to the illustrated numbers. Further, the materials of the constituent elements shown above are all exemplified for specifically explaining the present invention, and the present invention is not limited to the exemplified materials. In addition, the connection relationship between the components is exemplified for specifically explaining the present invention, and the connection relationship for realizing the function of the present invention is not limited to this.

  The circuit configuration shown in the circuit diagram is an example, and the present invention is not limited to the circuit configuration. That is, like the above circuit configuration, a circuit that can realize a characteristic function of the present invention is also included in the present invention. For example, the present invention includes a device in which a device such as a switching device (transistor), a resistor, or a capacitor is connected in series or in parallel to a certain device within a range in which a function similar to the above circuit configuration can be realized. It is. In other words, the term “connected” in the above embodiment is not limited to the case where two terminals (nodes) are directly connected, and the two terminals ( Node) is connected through an element.

  As mentioned above, although the current bypass circuit, the light source for illumination, and the illumination device according to one or more aspects have been described based on the embodiment, the present invention is not limited to this embodiment. Unless it deviates from the gist of the present invention, various modifications conceived by those skilled in the art have been made in this embodiment, and forms constructed by combining components in different embodiments are also within the scope of one or more aspects. May be included.

  The current bypass circuit of the present invention can be applied to an LED driving circuit of an LED lamp. That is, the present invention can be widely used in general lighting devices as an LED lamp that replaces a conventional incandescent bulb or the like.

1 Drive circuit 2 LED
10 First rectifier circuit (DB1)
20 Inverter 30 Inverter control circuit 40 Second rectifier circuit (DB2)
50, 50a to 50e Current bypass circuit 100 Light bulb shaped lamp 110 Globe 120 LED module 130 Post 140 Support member 153a, 153b Lead wire 180 Outer casing 190 Base 200 Illuminating device 203 Lighting fixture 204 Appliance body 204a Socket 205 Lamp cover AC AC power supply CD1, CD2 Smoothing capacitor C3, C4, C5, C6, C8 Capacitor T1 Drive transformer D5, D6, D7 Diode FS Current fuse element L1 Inductor NF Noise filter P1, P2 Input terminal P3, P4 Output terminal PTC1, PTC2, NTC1, NTC2 , NTC3 thermistor Q1 first transistor Q2 second transistor Q3, Q4, Q5, Q6 switching element R1, R2, R4 to R16 resistor TD tri Diode

Claims (10)

A current bypass circuit used at the time of light emission of a light emitting unit that emits light by a drive current supplied from a power supply,
Connected in parallel to the light emitting part,
With a thermistor,
When the temperature of the thermistor is the first temperature, a current having a first current value is drawn from the drive current, and when the temperature of the thermistor is a second temperature higher than the first temperature, the current value is larger than the first current value. A current bypass circuit that draws a current having a second current value from the drive current. Furthermore, the switching element is connected in parallel to the light emitting unit, and the thermistor is connected to a control terminal,
When the temperature of the thermistor is the first temperature, the switching element is turned off, and when the temperature of the thermistor is the second temperature, the switching element is turned on, thereby setting the second current value. The current bypass circuit according to claim 1, wherein current is drawn from the drive current. further,
A first resistor having one end connected to the drain of the switching element;
A second resistor having one end connected to one end of the thermistor and a gate that is the control terminal of the switching element;
One of the other end of the second resistor and the other end of the thermistor is connected to the anode of the light emitting unit,
The other end of the second resistor and the other end of the thermistor are connected to the cathode of the light emitting unit,
One of the other end of the first resistor and the source of the switching element is connected to the anode of the light emitting unit,
The current bypass circuit according to claim 2, wherein the other end of the first resistor and the other of the sources of the switching elements are connected to a cathode of the light emitting unit. further,
A first resistor having one end connected to the collector of the switching element;
A second resistor having one end connected to one end of the thermistor and a base that is the control terminal of the switching element;
One of the other end of the second resistor and the other end of the thermistor is connected to the anode of the light emitting unit,
The other end of the second resistor and the other end of the thermistor are connected to the cathode of the light emitting unit,
One of the other end of the first resistor and the emitter of the switching element is connected to the anode of the light emitting unit,
The current bypass circuit according to claim 2, wherein the other end of the first resistor and the other of the emitters of the switching element are connected to a cathode of the light emitting unit. Furthermore, a resistor having one end connected to one end of the thermistor,
One of the other end of the resistor and the other end of the thermistor is connected to the anode of the light emitting unit,
The current bypass circuit according to claim 1, wherein the other end of the resistor and the other end of the thermistor are connected to a cathode of the light emitting unit. The resistance change rate based on a resistance value at a reference temperature of the thermistor increases exponentially with an increase in temperature when the temperature of the thermistor exceeds a predetermined temperature. 2. The current bypass circuit according to item 1. The current bypass circuit according to claim 1, wherein the thermistor has a positive temperature characteristic. The current bypass circuit according to claim 1, wherein the thermistor has a negative temperature characteristic. The current bypass circuit according to any one of claims 1 to 8,
An illumination light source comprising the light emitting unit. The current bypass circuit according to any one of claims 1 to 8,
An illumination device comprising the light emitting unit.

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