JP6098209B2 - LED lighting device, LED bulb and LED module substrate - Google Patents

Description

  The present invention relates to an LED lighting device, an LED bulb, and an LED module substrate.

  In recent years, as LED brightness has increased, LED bulbs are becoming popular in place of incandescent bulbs and bulb-type fluorescent lamps. In an LED bulb, a configuration is required that prevents an excessive input current from continuing when a lighting circuit fails. For example, Patent Document 1 discloses a configuration in which a self-recovering temperature fuse is inserted in an input line in an LED lighting apparatus having a constant current drive circuit. In this document, when an abnormality occurs in the constant current drive circuit and the ambient temperature exceeds the operation value of the self-recovery temperature fuse, the self-recovery temperature fuse operates and the drive circuit is shut off.

  Patent Document 2 discloses a configuration in which a thermal fuse is displaced on the LED module board side on the lighting circuit board in a light bulb-type LED lamp having a lighting circuit board and an LED module board. In this configuration, when the temperature of the LED on the LED module substrate or the transistor on the lighting circuit exceeds a predetermined temperature, the temperature fuse is blown and the lighting circuit is opened.

JP 2010-1114060 A JP 2010-103028 A

  By the way, in the failure mode in the LED lighting circuit, there is one in which the overcurrent in the output from the lighting circuit to the LED is continued. For example, when the constant current control function of the constant current circuit fails, the maximum output current may continue to be supplied to the LED. In such a failure mode, as will be described in detail later, the temperature rise on the LED module substrate is more conspicuous than the temperature rise of other components. Here, as the heat dissipation structure of the LED in the LED bulb, a configuration is generally adopted in which the LED module substrate is placed in contact with the housing of the LED bulb and heat is radiated by heat conduction from the LED to the housing. And a housing | casing is normally comprised with resin instead of a metal for weight reduction of a LED bulb. Therefore, when the overheating of the LED module substrate is not properly prevented, a resin casing in contact with the LED module substrate is softened or deformed, and there arises a problem that it becomes difficult to remove the failed LED bulb.

  However, as in Patent Document 1 or Patent Document 2, the configuration using the thermal fuse has the following problems. First, there is a mounting problem. When a thermal fuse is disposed on the lighting circuit board, the thermal fuse cannot properly detect the temperature of the LED module board that rises the fastest. In addition, in order to place the thermal fuse body in contact with the LED module substrate while connecting the thermal fuse in series to the input line of the lighting circuit, it is necessary to route the wiring in a narrow space inside the LED bulb. It is not realistic. In addition, a part of the input line is routed around the switching circuit on the lighting circuit, which may increase the noise terminal voltage, which is not preferable. Second, there is a cost problem. Thermal fuses generally have a smaller DC rated voltage than the AC rated voltage. For example, in a general temperature fuse (for example, a radial type temperature fuse manufactured by Uchihashi Estec Co., Ltd.), the AC rated voltage is AC250V, whereas the DC rated voltage is DC50V. Therefore, in consideration of the fact that the LED array voltage exceeds 50V in a relatively high output LED bulb, it is necessary to connect a thermal fuse in series with the LED array and mount it directly on the LED module board. It is necessary to use a thermal fuse, and the increase in cost becomes a problem.

  Therefore, an object of the present invention is to provide an LED lighting device and an LED bulb that can reliably prevent overheating of the LED module substrate with a simple configuration.

  The LED lighting device according to the present invention has a current fuse, a lighting circuit board that converts an input current input through the current fuse into a direct current and outputs it, and an LED array into which the output current of the lighting circuit board is input And a protection circuit having a temperature detection element that detects the temperature of the LED module board and a switch element that short-circuits the LED array when the temperature detected by the temperature detection element exceeds a predetermined value.

  Here, the temperature detection element or the temperature detection element and the switch element are preferably mounted on the LED module substrate. Further, it is preferable that the LED module substrate has a front surface and a back surface, the LED array is mounted on the front surface side, and the temperature detection element or the temperature detection element and the switch element are mounted on the back surface side.

  The LED bulb of the present invention includes the LED lighting device described above, a base connected to the input end of the LED lighting device, and a housing that houses the LED lighting device and has a base attached thereto. Here, the casing is made of resin, and the LED module substrate is attached in contact with the casing.

  An LED module substrate of the present invention includes an LED array to which a direct current is input, a temperature detection element, a protection circuit having a switch element that short-circuits the LED array when a temperature detected by the temperature detection element exceeds a predetermined value, and an LED And an array and a substrate on which a protection circuit is mounted.

  Here, it is preferable that the substrate has a front surface and a back surface, the LED array is mounted on the front surface, and the temperature detection element and the switch element are mounted on the back surface.

It is a circuit diagram of the LED lighting device by embodiment of this invention. It is a figure which shows the internal structure of the LED light bulb by embodiment of this invention. 1 is an external view of an LED bulb according to an embodiment of the present invention. It is a figure explaining operation | movement of a comparative example. It is a figure explaining operation | movement of embodiment of this invention.

  FIG. 1 shows a circuit diagram of an LED lighting device 100 according to an embodiment of the present invention. The LED lighting device 100 includes a lighting circuit board 200 and an LED module board 300, and an AC voltage such as a commercial power supply is input to the lighting circuit board 200, and an output current of the lighting circuit board 200 is output via the output wiring 400 to the LED module board. 300.

  The lighting circuit board 200 includes an AC input circuit including a fuse 201 connected in series to an input line and a filter capacitor 202 connected between the input lines. The fuse 201 is a current fuse that is melted and opened when a current exceeding the operating point is continuously energized for a predetermined period, and may be a general-purpose current fuse generally used for LED bulbs. You may make it connect noise filter elements, such as a common mode coil or a normal mode coil, to an alternating current input circuit as needed. A rectifier circuit including a diode bridge 203 for full-wave rectification of the input voltage and a capacitor 204 connected between the output ends of the diode bridge is connected to the subsequent stage of the AC input circuit.

  The lighting circuit board 200 includes a transformer 205, a switching element 206, a diode 207, a smoothing capacitor 208, a current detection resistor 210, an operational amplifier 211, a reference voltage source 212, a photocoupler 213, and a PWM control circuit 214 after the rectifier circuit. Provide a circuit. In this embodiment, the converter circuit is an insulation type flyback converter, and a so-called one-converter type flyback circuit having a power factor correction function is employed. The converter circuit converts the input current into a direct current and outputs it to the LED module substrate 300. Hereinafter, for convenience of explanation, a portion including the transformer 205, the switching element 206, the diode 207, and the smoothing capacitor 208 is referred to as a main circuit, and a current detection resistor 210, an operational amplifier 211, a reference voltage source 212, a photocoupler 213, and a PWM control circuit 214. The part including “” is referred to as a control unit.

  In the main circuit, energy is accumulated by the primary winding of the transformer 205 during the ON period of the switching element 206, and the energy is charged to the smoothing capacitor 209 from the secondary winding side via the diode 208 during the OFF period of the switching element 206. The The step-down ratio is determined by the turn ratio of the secondary winding to the primary winding, and the output current is determined by the ON duty (ON period width) of the switching element 206.

  In the control unit, a voltage proportional to the LED current is generated in the current detection resistor 210 inserted in the output line of the converter circuit, and this voltage is input to the negative input terminal (−) of the operational amplifier 211. A reference voltage corresponding to the set LED current is input from the reference voltage source 212 to the positive input terminal (+) of the operational amplifier 211. A feedback resistor or a capacitor (not shown) is connected between the negative input terminal and the output terminal of the operational amplifier 211, and an error between the negative input terminal voltage and the positive input terminal voltage is output at the output terminal. The output terminal of the operational amplifier 211 is input to the photodiode side of the photocoupler 213. In the photocoupler 213, the output state of the output phototransistor is determined according to the current flowing through the input photodiode. The PWM control circuit 214 performs PWM control of the switching element 206 with an ON width based on the output state of the photocoupler 213. That is, the control unit feedback-controls the output current of the main circuit so that the detected LED current detected by the current detection resistor 210 is equal to the set LED current value determined by the reference voltage source 212.

  The LED module substrate 300 includes an LED array 310 into which the output current of the lighting circuit substrate 200 is input, and a protection circuit 320 connected in parallel to the LED array 310. The LED array 310 includes a plurality of LED elements 301 connected in series. The protection circuit 320 includes a thermistor 321 (temperature detection element), a transistor 322 (switch element), and a resistor 323. In this embodiment, the thermistor 321 is a positive characteristic thermistor (a temperature sensitive resistance element having a positive resistance temperature characteristic), and the transistor 322 is an FET. The source terminals of the thermistor 321 and the transistor 322 are connected to the low potential side of the input line of the LED module substrate 300, and the drain terminals of the resistor 323 and the transistor 322 are connected to the high potential side. The voltage applied to the LED array 310 is divided by the thermistor 321 and the resistor 323, and the voltage generated in the thermistor 321 is input to the gate terminal of the transistor 322. The thermistor 321 is disposed in contact with the LED module substrate 300.

  When the temperature of the LED module substrate 300 rises, the resistance value of the thermistor 321 increases and the gate voltage of the transistor 322 increases. When the gate voltage exceeds the threshold value, the transistor 322 becomes conductive and both ends of the LED array 310 are short-circuited. Note that the temperature of the thermistor 321 when the transistor 322 is conductive is referred to as a detected temperature. The detected temperature is determined by the set LED voltage, the temperature-resistance characteristic of the thermistor 321, the resistance value of the resistor 323, and the threshold value of the gate voltage of the transistor 322. As described above, when the detected temperature is equal to or lower than the predetermined value, the non-conducting state of the transistor 322 is maintained, and when the detected temperature exceeds the predetermined value, the transistor 322 is turned on.

  Here, an example of the electrical characteristics of the LED lighting device 100 will be described. The input voltage is assumed to be 100V and 200V, but is designed to correspond to a power supply voltage range of 90V to 220V in consideration of power supply voltage fluctuations. However, it is assumed that the converter circuit of the lighting circuit board 200 is designed to operate at the maximum duty when the input voltage is 80 V with respect to the power supply voltage 90 V, further considering a margin in circuit design. It is assumed that the set voltage of the LED array 310 is 125 V and the set current is 400 mA. Therefore, the set power of the LED array 310 is 50 W.

Table 1 shows LED voltage (output voltage), LED current (output current), and LED power (output power) with respect to power supply voltage fluctuation. By the feedback operation in the converter circuit of the lighting circuit board 200, the LED current and the LED power are controlled to constant values of 400 mA and 50 W, respectively, in the input voltage range of 80V to 220V.

  FIG. 2 is an internal configuration diagram of the LED bulb 1 incorporating the LED lighting device 100 according to the present embodiment, and FIG. 3 is an external view of the LED bulb 1. 2 and 3, the LED bulb 1 includes the LED lighting device 100 (the lighting circuit board 200, the LED module board 300, and the output wiring 400), the base 2, the housing 3, and the cover 4 described above. The base 2 is an E17, E26 or E39 base, and the base part and the side part are connected to the input terminals T1 and T2 of the lighting circuit board 200 via the input wiring W, respectively. The housing 3 (hatched portion in FIG. 2) is made of resin, and a tapered cylindrical hollow portion is formed therein. An opening on one end side (feeding side) of the housing 3 is converged and fixed to the base 2, and a cover 4 is attached to the opening on the other end side (light irradiation side). A lighting circuit board 200 having a shape corresponding to the cross-sectional shape in the optical axis direction is attached to the cylindrical cavity of the housing 3. The LED module substrate 300 is disposed perpendicular to the optical axis direction in the opening on the light irradiation side of the housing 3. The cover 4 is made of transparent or translucent glass, and is attached as necessary. In the lighting circuit board 200, the radiation fins 215 are attached to the switching element 206 and the diode 207.

  In the LED module substrate 300, the components of the LED array 310 and the protection circuit 320 are mounted on the substrate 350. The substrate 350 has a surface 350a on the light emitting side and a back surface 350b on the side facing the surface 350a. The LED array 310 (LED element 301) is mounted on the surface 350a. The outer edge portion of the back surface 350b is disposed in contact with the fixed surface 3a of the housing 3, heat of the LED module substrate 300 is conducted to the housing 3 through the fixed surface 3a, and heat dissipation of the LED array 310 is performed.

  Here, the protection circuit 320 is preferably mounted on the back surface 350b side. Thereby, the components of the protection circuit 320 do not affect the optical characteristics of the LED bulb 1. Further, it is easier to secure the mounting space on the back surface 350b on which the connection terminals of the output wiring 400 are mounted than on the front surface 350a on which the LED array 310 is mounted, and the protection circuit 320 can be arranged at a desired position. it can.

The operation of the LED lighting device (comparative example) when the protection circuit 320 is not connected to this embodiment will be described. Table 2 shows electrical characteristics of a comparative example when the switching element 206 is driven by the PWM control circuit 214 with the maximum duty. This assumes a state in which one of the components of the control circuit (210 to 214) fails and the PWM control circuit 214 keeps driving the switching element 206 with the maximum duty. As can be seen from Table 2, at an input voltage of 200 V, 119.7 W of power exceeding twice the rated power of 50 W is input to the LED array 310.

    FIG. 4 shows changes in the temperatures of the transformer 205, the radiation fins 215, and the LED module substrate 300 when the input voltage is 200 V in Table 2. FIG. 2 shows the measurement points of the transformer 205, the heat radiation fin 215, and the LED module substrate 300 as 205p, 215p, and 300p, respectively. Note that the temperature of the front surface 350a of the LED module substrate 300 and the back surface 350b are substantially equal. In FIG. 4, the normal output state as shown in Table 1 is maintained before t0, and the temperatures of the transformer 205, the heat radiation fin 215, and the LED module substrate 300 are 95 ° C., 90 ° C., and 100 ° C., respectively. Shall be. It is assumed that an abnormal output state as shown in Table 2 occurs at time t0.

    As can be seen from FIG. 4, the temperature of the LED module substrate 300 rapidly rises compared to the temperatures of the transformer 205 and the heat radiation fins 215. At the time t1 when the temperature of the transformer 205 reaches 115 ° C. (temperature increase is 20 deg), the temperature of the LED module substrate 300 rises to 173 ° C. Here, in order to prevent an excessive protection operation (operation that protects an abnormal state in spite of a normal state), it is desirable that the detected temperature rise is 20 degrees or more with respect to the normal operation. According to the comparative example, the LED module substrate 300 is overheated while detecting a 20 deg temperature rise in the transformer 205 or the heat radiation fin 215.

    For this reason, in the configuration for detecting the temperature of the transformer 205 and the like of the lighting circuit board 200, the temperature of the LED module board 300 is changed to the softening temperature of the resin of the casing 3 (for example, while detecting a predetermined amount of temperature rise of the transformer 205). , 160 ° C.). Therefore, in this embodiment, the temperature of the component on the lighting circuit board 200 is not detected, but the temperature of the LED module board 300 is directly detected and before the detected temperature reaches the softening temperature of the resin of the housing 3. The operation of the LED lighting device 100 (lighting circuit board 200) is stopped.

    Specifically, in the LED lighting device 100 of the present embodiment, the detected temperature is 140 ° C. FIG. 5 shows changes in the temperatures of the transformer 205, the heat radiation fin 215, and the LED module substrate 300 when the input voltage is 200 V in Table 2 in this embodiment. As in FIG. 4, the normal output state as shown in Table 1 is maintained before t0, and the temperatures of the transformer 205, the heat radiation fin 215, and the LED module substrate 300 are 95 ° C., 90 ° C., and 100 ° C., respectively. Suppose that it was ℃. It is assumed that an abnormal output state as shown in Table 2 occurs at time t0. As shown in FIG. 5, at the time t2 when the temperature of the LED module substrate 300 reaches 140 ° C., the transistor 322 is turned on, whereby the fuse 201 is blown immediately after that and the input current is cut off. Therefore, the temperature of each part falls after t2.

    As described above, the thermistor 321 of the protection circuit 320 is disposed in contact with the LED module substrate 300. As a result, when the LED module substrate 300 is overheated, the resistance value of the thermistor 321 increases and the transistor 322 becomes conductive. When the transistor 322 is turned on, both ends of the LED array 310, that is, the output current of the lighting circuit board 200 is short-circuited. When the overcurrent state due to the short circuit of the output current continues for a predetermined period, the fuse 201 is melted and the input to the lighting circuit board 200 is cut off. Note that, for the predetermined period, the fuse 201 is blown out in a short time (for example, 1 second or less) after the transistor 322 short-circuits the output of the lighting circuit board 200 due to the characteristics of a general current fuse.

    Note that even when the lighting circuit board 200 is in a normal state and the ambient temperature is high, the transistor 322 can be turned on as the resistance value of the thermistor 321 increases. However, since the feedback control of the converter circuit of the lighting circuit board 200 is operating properly, only the same current as the LED current during normal lighting (400 mA in the above example) flows through the transistor 322. Therefore, until the temperature of the thermistor 321 decreases, the current temporarily does not flow through the LED array 310, but the fuse 201 of the lighting circuit board 200 is not blown. That is, the LED bulb 1 is not disabled only by an increase in detection temperature caused by an increase in ambient temperature.

    As described above, according to the configuration of the present embodiment, the following various advantageous effects can be obtained.

(1) Prevention of softening of the housing 3 According to the present embodiment, the temperature of the LED module board 300 is directly detected, and when the detected temperature exceeds a predetermined value, the input current of the lighting circuit board 200 is cut off and the LED lighting device 100 The operation can be stopped. Therefore, softening or deformation of the housing 3 attached in contact with the LED module substrate 300 can be reliably prevented.

(2) Simplification of the LED lighting device 100 According to the present embodiment, the only components added as the protection circuit 320 are the thermistor 321, the transistor 322, and the resistor 323. And since the current fuse generally mounted in the input part of LED lighting device is utilized as a fuse, it is not necessary to provide another fuse, such as a temperature fuse, for the electric current interruption in the lighting circuit board 200. Therefore, the present invention can be implemented with a simple and low-cost configuration.

(3) Suppression of shortening life of LED bulb 1 According to the present embodiment, when the LED module substrate 300 is under a high temperature exceeding the detection temperature, the output current from the lighting circuit substrate 200 is not the LED array 310, It flows to transistor 322. In this operation, the fuse 201 is not blown, and can be turned on again when the temperature of the LED module substrate 300 is lowered. Therefore, the LED array 310 does not emit light at a high temperature, and the LED bulb 1 is not disabled by detecting the high temperature state once, and the life of the LED element 301 and the LED bulb 1 can be prevented from being shortened. it can.

(4) Ensuring optical characteristics of the LED bulb 1 According to the configuration of the present embodiment, since the protection circuit 320 is disposed on the back surface 350b side of the LED module substrate 300, the optical characteristics on the surface 350a side where the LED array 310 is disposed. Is not disturbed. Therefore, desired optical characteristics can be obtained in the same manner as a general LED bulb.

(5) Ease of assembly of the LED bulb 1 According to this embodiment, since the protection circuit 320 is mounted on the LED module substrate 300, no additional wiring is required between the lighting circuit substrate 200 and the LED module substrate 300. The LED bulb 1 can be easily assembled and is advantageous in its manufacture.

(6) Ease of introduction of protection configuration According to the configuration of the present embodiment, since the protection circuit 320 is mounted on the LED module substrate 300, this embodiment can be replaced with a lighting circuit substrate 200 having a general circuit configuration. Applicable to. Therefore, in the existing LED bulb, the present invention can be implemented only by replacing the LED module substrate with the LED module substrate 300 of the above embodiment. Thus, the present invention is easy to introduce and highly versatile.

  Although preferred embodiments of the present invention have been described above, the present invention can be modified in various ways as follows.

Modification Example of Protection Circuit Mounting In the above embodiment, the configuration in which all the components of the protection circuit 320 are mounted on the LED module substrate 300 is shown. However, the thermistor 321 and the resistor 323 are mounted on the LED module substrate 300 and the transistor 322 is mounted. Can also be mounted on the lighting circuit board 200. In this case, it is necessary to provide a gate wiring from the contact point of the thermistor 321 and the resistor 323 to the gate terminal of the transistor 322 between the lighting circuit board 200 and the LED module board 300. Only needed. In addition, according to this modification, said effect (1) thru | or (5) is acquired.

  Further, the protection circuit 320 may be mounted between the output lines on the lighting circuit board 200, and the thermistor 321 may be in contact with the back surface 350b of the LED module board 300. However, it is a condition that the separation distance between the lighting circuit board 200 and the LED module board 300 is small enough to contact the back surface 350b in a state where the thermistor 321 is axially mounted. In addition, according to this modification, said effect (1) thru | or (5) is acquired.

Modification of Temperature Detection Element In the above embodiment, the positive characteristic thermistor is used as the temperature detection element of the protection circuit 320, but a negative characteristic thermistor may be used. In this case, a negative characteristic thermistor may be connected between the gate and drain of the transistor 322, and a voltage dividing resistor (corresponding to the resistor 323) may be connected between the gate and source.

-Modification of switch element In the above embodiment, a transistor made of an FET is used as the switch element of the protection circuit 320. However, if the element can change the conduction state in accordance with the input voltage or input current, the relay switch Other types of switch elements may be used.

In the above embodiment, an insulating flyback circuit is used as the converter circuit of the lighting circuit board 200. However, if a DC current can be output, the converter circuit can be other than a non-insulated step-down chopper circuit or the like. The circuit of the form may be sufficient. Moreover, although the structure which feeds back LED current (output current) was shown in the said embodiment, it is good also as a structure which feeds back LED electric power (output electric power). In this case, a voltage detection circuit for detecting the output voltage and a multiplier for multiplying the detection output voltage and the detection output current are further provided. The output of the multiplier is input to the negative input terminal of the operational amplifier 211, and the voltage corresponding to the set LED power is input from the reference voltage source 212 to the positive input terminal of the operational amplifier 211. That is, PWM control is performed so that the output power corresponding to the product of the detected output voltage and the detected output current is equal to the set LED power, and the LED power is feedback-controlled.

DESCRIPTION OF SYMBOLS 1 LED bulb 2 Base 3 Case 100 LED lighting device 200 Lighting circuit board 201 Fuse (current fuse)
300 LED module substrate 310 LED array 320 protection circuit 321 thermistor (temperature detection element)
322 transistor (switch element)
350 substrate 350a front surface 350b back surface

Claims (6)

An LED lighting device,
A lighting circuit board that has a current fuse, converts the input current input through the current fuse into a direct current, and outputs the direct current;
An LED module substrate on which the LED array is mounted to the output current of the lighting circuit board is projected input via an input line,
A switch element for short-circuiting between the input line of the LED array when the temperature detected by the temperature detecting element and the temperature detection element for detecting the temperature of the LED module substrate exceeds a predetermined value, the LED module substrate LED lighting device that includes a protection circuit mounted on the. The LED lighting device according to claim 1 , wherein the LED module substrate has a front surface and a back surface, the LED array is mounted on the front surface side, and the temperature detection element and the switch element are mounted on the back surface side. LED lighting device. LED lighting device according to claim 1 or 2 ,
A base connected to an input end of the LED lighting device;
An LED bulb comprising a housing that houses the LED lighting device and to which the base is attached. 4. The LED bulb according to claim 3 , wherein the casing is made of resin, and the LED module substrate is attached in contact with the casing. An LED module substrate,
A LED array direct current is input through the input line,
A protection circuit having a switching element temperature detected by the temperature detecting element and the temperature sensing element is short-circuited between the input line of the LED array if it exceeds a predetermined value,
An LED module substrate comprising the LED array and a substrate on which the protection circuit is mounted. 6. The LED module substrate according to claim 5 , wherein the substrate has a front surface and a back surface, the LED array is mounted on the front surface, and the temperature detection element and the switch element are mounted on the back surface.

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