JP5822670B2 - LED lighting device - Google Patents

Description

  The present invention relates to an LED lighting device.

  LED attracts attention as a light source excellent in environmental performance, and has come to be used as general lighting in houses and offices as LED lighting. Among LED lighting, there is a bulb-type LED lighting that has a base similar to that of an incandescent light bulb and is attached to an incandescent light bulb, and is controlled by a phase control method that has been used as a dimming means for the incandescent light bulb. There are also products corresponding to optical devices (hereinafter simply referred to as dimmers).

  Many dimmers conduct and block between an AC power supply and a load by turning on and off a triac that is a semiconductor element. After the triac is turned on (ignited), it is turned off (extinguishes) again unless a current larger than a predetermined current value called a holding current continues to flow. Many dimmers are designed on the assumption that the load is an incandescent bulb. If the load is an incandescent light bulb, a sufficient current exceeding the holding current flows from the time when the triac is turned on to the time near the zero cross of the AC power supply, and the triac is maintained in the on state. However, in LED lighting with LEDs as the load, the current is smaller than incandescent bulbs. Therefore, sufficient current exceeding the holding current does not flow from the time when the triac is turned on to the time near the zero cross of the AC power supply, and the zero cross of the AC power supply does not flow. There is a possibility that the triac turns off before reaching the vicinity. Hereinafter, this phenomenon is referred to as false extinction. In particular, in a situation where erroneous extinction occurs randomly or in a situation where there are variations in the timing of erroneous extinction, the operation of the LED lighting device becomes unstable and flickering occurs.

  As one means for solving the above-described problem, an LED lighting device having a function of continuously flowing a current equal to or higher than the holding current to the triac to prevent erroneous arc extinction can be considered. As such an LED lighting device, there is a device described in Patent Document 1, for example. In this device, a dummy load such as a constant current circuit is connected in parallel with the DC-DC converter that supplies power to the LED, and the current flows through the dummy load so that the current flowing through the triac exceeds the holding current. In addition, flowing current through the dummy load in this way also serves to reset the timer circuit of the dimmer and turn on the triac that has been turned off again.

JP 2010-140824 A

  In the technique described in Patent Document 1, by providing a dummy load, a current equal to or higher than the holding current is always kept flowing. This can solve the above problem, but the holding current differs depending on the dimmer, and there are many dimmers that require a current of 30 mA or more to maintain the triac on state. In particular, when an LED lighting device is configured using a capacitor input type circuit, the input current becomes substantially zero during the discharge period of the smoothing capacitor, so that it is required that all currents larger than the holding current flow to the dummy load. Here, when the effective value of the voltage applied to the dummy load is 100 V and the current flowing through the dummy load is 30 mA, the loss of the dummy load is 3 W. In view of the fact that most of the bulb-type LED illuminations that have been commercialized consume less than 10 W, it is not desirable in terms of efficiency to generate a loss of 3 W with only a dummy load.

  An object of this invention is to implement | achieve an efficient LED lighting device which can suppress a flicker by operating a dimmer stably.

In order to solve the above problem, a rectifier circuit that converts a phase-controlled AC power supply voltage into a rectified voltage, and a DC output connected to the DC output of the rectifier circuit through a diode, the DC voltage is smoothed by the rectified voltage A DC-DC conversion circuit that converts the DC voltage and supplies power to the LED load, and a current setting circuit that outputs a current setting value of the DC-DC conversion circuit based on the rectified voltage. and an LED lighting device, comprising: a variable resistance circuit connected to the DC output of the rectifier circuit, and a resistance value setting circuit for varying the resistance value of the variable resistance circuit based on the rectified voltage, the variable resistor circuit comprises a series of resistors and switching elements, the resistance value setting circuit, when the rectified voltage is higher than the desired reference voltage, and controls to turn off the switching element, wherein the Allowed The resistance value of the resistor circuit is increased, the resistance value setting circuit includes a regulator circuit for clamping the rectified voltage at a desired voltage value, by comparing the output voltage of the regulator circuit and the desired threshold, the rectifier And a comparator that indirectly determines whether or not the voltage is higher than the reference voltage, and the series body is connected to the output of the regulator circuit to form an LED lighting device.

  According to the LED lighting device of the present invention, it is possible to stably operate the dimmer to suppress flickering and to realize an efficient LED lighting device.

It is a block diagram of the LED lighting device of the present invention. FIG. 3 is an internal circuit diagram of a phase control type dimmer. It is an operation | movement waveform at the time of connecting an incandescent lamp to the phase control system dimmer. It is a structural example of the variable resistance circuit and resistance value setting circuit in the LED lighting device of this invention. It is an example of an operation waveform of the LED lighting device of the present invention. It is a structural example of the variable resistance circuit and resistance value setting circuit in the LED lighting device of this invention. It is an output voltage waveform of a regulator circuit. It is a specific circuit structural example of the LED lighting device of this invention. It is a power supply circuit for control circuits in the LED lighting device of this invention.

  Embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a block diagram of an LED lighting device according to the present invention. In FIG. 1, the right side from the rectifier circuit 102 is the LED lighting device of the present invention. The rectifying circuit 102 rectifies the AC power supply voltage phase-controlled by the dimmer 101 to generate a rectified voltage. The direct current output of the rectifier circuit 102 is connected to the capacitor 104 via the diode 103. The capacitor 104 smoothes the rectified voltage and generates a DC voltage. That is, the LED lighting device in the present embodiment is a capacitor input type circuit. As a result, the pulsation of the DC voltage is reduced, and it becomes easy for the subsequent DC-DC conversion circuit 105 to suppress the pulsation of the current flowing through the LED. The DC-DC conversion circuit 105 converts a DC voltage and supplies power to the LED load 106. Regarding the LED load 106, the number of LEDs and the connection form are not limited, and an LED module incorporating a protection element or the like may be included.

  A variable resistance circuit 107 is connected to the DC output of the rectifier circuit 102. The resistance value setting circuit 108 outputs a resistance value setting signal for changing the resistance value of the variable resistance circuit 107 based on the rectified voltage. The variable resistance circuit 107 and the resistance value setting circuit 108 control the on / off state of the triac in the dimmer 101 according to the rectified voltage, and reset the timer circuit of the dimmer 101 to turn on the triac again. Play a role. The current setting circuit 109 outputs the current setting value of the DC-DC conversion circuit 105 based on the rectified voltage. The current setting circuit 109 enables control of the LED current according to the operation of the dimmer 101, that is, dimming.

  Before describing specific operations, the dimmer 101 will be described. FIG. 2 shows an outline of an internal circuit of the phase control type dimmer 101 using a triac. As shown in FIG. 2, the triac 110 is connected between the AC power supply 100 and the load 115. In parallel with the triac 110, a timer circuit that is a series body of a resistor 111, a variable resistor 112, and a capacitor 113 is connected. A connection point between the variable resistor 112 and the capacitor 113 is connected to the gate of the triac 110 via the diac 114.

  FIG. 3 shows waveforms of the on / off state of the triac 110, the load voltage, and the load current when an incandescent bulb is connected as the load 115. During the on period of the triac 110, the load voltage is substantially the same as the voltage of the AC power supply 100. Since the incandescent lamp is almost pure resistance, the waveform of the load current is similar to the voltage. In the vicinity of the zero cross of the AC power supply 100, when the load current becomes smaller than the holding current of the triac 110, the triac 110 is turned off. During the off period of the triac 110, a minute current flows from the AC power source 100 to the path of the resistor 111, the variable resistor 112, the capacitor 113, and the load 115, and charges are stored in the capacitor 113. Since the impedance of the dimmer 101 is sufficiently larger than that of the incandescent lamp, the load voltage is substantially zero. When the voltage on the capacitor 113 rises and the diac 114 is turned on, the triac 110 is turned on again. When the resistance value of the variable resistor 112 is increased by operating the dimmer 101, the time until the triac 110 is turned on again becomes longer. As a result, the load power is reduced, and the light output is reduced for an incandescent bulb.

  In the present invention, the load 115 in FIG. 2 is the LED lighting device in FIG. 1 and has different characteristics from the incandescent bulb. Specifically, the impedance is higher than that of an incandescent bulb, and it is not necessarily pure resistance like an incandescent bulb. Therefore, the operation waveform is not always the same as in FIG.

  FIG. 4 is a configuration example of the variable resistance circuit 107 and the resistance value setting circuit 108 in the LED lighting device of the present invention. The resistance value setting circuit 108 includes resistors 116 and 117, a comparator 118, and a DC voltage source 119, and outputs a resistance value setting signal that becomes L level when the rectified voltage is higher than a desired reference voltage.

  The variable resistance circuit 107 includes a series body of a resistor 120 and a MOSFET 122 serving as a switching element, and a resistor 121 connected in parallel with the series body, and the resistance value is changed to a binary value by turning on and off the MOSFET 122. . Instead of the MOSFET 122, other types of switching elements such as bipolar transistors and IGBTs may be used.

  If the rectified voltage is higher than the reference voltage, the MOSFET 122 is turned off, and the resistance value of the variable resistance circuit 107 is increased by the amount that the resistor 120 is disconnected. Note that the resistance value of the variable resistance circuit 107 is not necessarily a binary value, and may be configured to continuously change depending on the rectified voltage. In addition, the specific configurations of the variable resistance circuit 107 and the resistance value setting circuit 108 are not particularly limited as long as the operation described below can be realized.

  FIG. 5 shows operation waveforms of the LED lighting device of the present invention, and shows a waveform of a rectified voltage, a DC voltage, a rectified current, and a resistance value of the variable resistance circuit 107. Here, the DC voltage is the voltage of the capacitor 104 as described above. The rectified current is a DC output current of the rectifier circuit 102 and has substantially the same waveform as that obtained by rectifying the current flowing through the dimmer 101.

  When the triac 110 is turned on, the rectified voltage rises to almost the same voltage level as that of the AC power supply 100. At this time, the rectified voltage becomes higher than the reference voltage, and the resistance value of the variable resistance circuit 107 increases. In addition, since a current for charging the capacitor 104 starts to flow from the AC power supply 100 via the dimmer 101, the rectifier circuit 102, and the diode 103, the rectified current also increases rapidly. Since the current for charging the capacitor 104 decreases as the DC voltage increases as the capacitor 104 is charged, the rectified current also gradually decreases.

  Near the time when the DC voltage reaches the maximum value and charging of the capacitor 104 is completed (hereinafter, simply referred to as completion of charging), the rectified current and the current flowing through the variable resistance circuit 107 substantially coincide. At this time, the resistance value of the variable resistance circuit 107 is set so that the rectified current becomes smaller than a desired reference current. Further, if the reference current is set smaller than the holding current of the triac 110, the triac 110 is turned off. The holding current varies depending on the dimmer, but is 5 mA at the minimum. Therefore, if the reference current is set to be less than 5 mA, the TRIAC can be reliably turned off when charging is completed for almost all the dimmers.

  The resistance value of the variable resistance circuit 107 at this time is set based on the reference current and the maximum value of the assumed rectified voltage. For example, when considering use with an AC power supply voltage of 100 Vac, the rectified voltage at the completion of charging is approximately 141 V at the maximum. Therefore, when the rectified voltage is 141 V, the resistance value is set larger than 28.2 kΩ (= 141 V ÷ 5 mA) so that the rectified current is smaller than 5 mA of the reference current.

  Of course, if the variable resistor circuit 107 in FIG. 4 is not connected and the variable resistor circuit 107 is opened when the rectified voltage is higher than the reference voltage, the charging is completed for almost all the dimmers. Sometimes the TRIAC can be reliably turned off. Strictly speaking, however, the resistors 116 and 117 which are elements of the resistance value setting circuit 108 in FIG. 4 are also considered to be part of the variable resistor circuit 107, so that the variable resistor circuit 107 is completely opened. Difficult to do. Therefore, even when the resistor 121 is not connected, it is necessary to set the resistance values of the resistors 116 and 117 as described above.

  After the triac 110 is turned off, the rectified voltage drops as shown in FIG. When the rectified voltage becomes lower than the reference voltage, the resistance value of the variable resistance circuit 107 decreases. A current is passed from the AC power supply 100 to the variable resistor circuit 107 via the timer circuit and rectifier circuit 102 of the dimmer 101, the timer circuit is reset, and the triac 110 is turned on again. Note that the DC-DC conversion circuit 105 operates stably by the energy stored in the capacitor 104 even when the triac 110 is off.

  As a problem of LED lighting devices so far, in each cycle of the AC power supply, the case where the triac is erroneously extinguished and the case where it is not erroneously extinguished randomly or the timing of erroneous extinction varies. In some cases, the operation of the dimmer may become unstable. When the operation of the dimmer becomes unstable in this way, flickering occurs in the LED load.

  As a countermeasure so far, there is a method of stably operating the dimmer by connecting a dummy load to the DC output of the rectifier circuit to prevent erroneous extinction of the triac. In this method, as the current flowing through the dummy load is increased, it can be expected to adapt to a wider range of dimmers. However, considering the decrease in efficiency due to increased dummy load loss, it is not realistic.

  On the other hand, in the present invention, the triac 110 is intentionally turned off at the same timing whenever charging of the capacitor 104 is completed. Even in such a system, the dimmer 101 and the DC-DC conversion circuit 105 can be operated stably, and flickering can be prevented. In addition, the method of the present invention is more efficient than the method of flowing a current larger than the holding current by the dummy load.

  FIG. 6 shows another example of the variable resistance circuit 107 and the resistance value setting circuit 108. In the circuit of FIG. 6, the resistor 123, the Zener diode 124, and the MOSFET 125 constitute a regulator circuit 126. Instead of the MOSFET 125, other types of semiconductor elements such as bipolar transistors may be used. The regulator circuit 126 is a component for both the variable resistance circuit 107 and the resistance value setting circuit 108 in FIG. Therefore, as shown in FIG. 4, the variable resistance circuit 107 and the resistance value setting circuit 108 are not divided by broken lines.

  As shown in FIG. 7, the regulator circuit 126 clamps the rectified voltage at a desired voltage value. The clamp voltage can be set as the Zener voltage of the Zener diode 124. The comparator 127 indirectly determines whether or not the rectified voltage is higher than the reference voltage by comparing the output voltage of the regulator circuit 126 with a desired threshold value. This threshold value can be set by the voltage value of the DC voltage source 128. Further, the comparator 127 outputs a resistance value setting signal that becomes L level when the rectified voltage is higher than the reference voltage. By reducing the level of the rectified voltage by the regulator circuit 126, even when the reference voltage is as low as several volts to several tens of volts, the accuracy of comparison by the comparator 127 is not impaired.

  The output of the regulator circuit 126 is connected in parallel with a resistor 129 and a series body of MOSFET 131 which is a switching element, and a resistor 130. Instead of the MOSFET 131, other types of switching elements such as bipolar transistors and IGBTs may be used. When the rectified voltage becomes higher than the reference voltage, the resistance value setting signal becomes L level, and the MOSFET 131 is turned off. The resistance value of the variable resistance circuit 107 is increased by the amount that the resistor 130 is disconnected.

  As shown in FIG. 7, when the rectified voltage is higher than the Zener voltage of the Zener diode 124, the output voltage of the regulator circuit 126 becomes substantially equal to the Zener voltage. Further, when the MOSFET 131 is off, the current flowing through the variable resistance circuit 107 has a value determined by the Zener voltage and the resistor 130. Here, when the charging of the capacitor 104 is completed, in order to make the rectified current smaller than the reference current, the Zener voltage and the resistance value of the resistor 130 are determined so that the current value determined by the Zener voltage and the resistance 130 becomes smaller than the reference current. Good. When the reference current is 5 mA and the Zener voltage is 10 V, the resistance value of the resistor 130 may be set to be larger than 2 kΩ (= 10 V ÷ 5 mA).

  FIG. 8 specifically shows the configuration of the rectifier circuit 102 and the DC-DC conversion circuit 105 in the LED lighting device shown in FIG. In FIG. 8, the full-wave rectifier circuit using the diode bridge 133 corresponds to the rectifier circuit 102 of FIG. A step-down chopper circuit including a diode 134, a MOSFET 135 as a switching element, a choke coil 136, a capacitor 137, a current detection resistor 138, a control circuit 139, and a control circuit power supply circuit 140 is the DC-DC of FIG. This corresponds to the conversion circuit 105. A resistor 132 for preventing inrush current is added as a component not shown in FIG. In addition, a fuse, a filter capacitor, or the like may be added. Depending on the voltage of the LED load 106, a step-up / step-down chopper or a step-up chopper may be used instead of a step-down chopper, and a flyback converter may be used if insulation is necessary. Instead of MOSFET 135, other types of switching elements such as bipolar transistors and IGBTs may be used.

  In FIG. 8, the control circuit 139 controls the current output from the DC-DC conversion circuit 105 to the LED load 106 according to the current setting value. Specifically, it is possible to control the MOSFET 135 until the current flowing through the MOSFET 135 reaches a current set value. By controlling the current flowing through the MOSFET 135, the current flowing through the LED load 106 can be indirectly controlled. Such a control circuit 139 can be easily configured by using a commercially available LED control IC. Of course, without using the control IC, it may be configured by combining discrete components such as a comparator, or may be configured as software using a microcomputer or a digital signal processor.

  The control circuit power supply circuit 140 is connected to the cathode of the diode 103 and converts the DC voltage of the capacitor 104 to generate the power supply voltage of the control circuit 139. Specifically, the operation voltage of the control IC, the comparator, the operational amplifier, etc. in the control circuit 139 is generated. Although the wiring (connection) is omitted in FIG. 8, the control circuit power supply circuit 140 generates power supply voltages for the resistance value setting circuit 108, the current setting circuit 109, and the like as necessary.

  As a specific configuration of the control circuit power supply circuit 140, a regulator circuit using a resistor 141, a Zener diode 142, and a MOSFET 143 is conceivable as shown in FIG. Instead of the MOSFET 143, other types of elements such as bipolar transistors may be used. In addition to FIG. 9, other types of regulator circuits such as a three-terminal regulator may be configured.

  Here, the control circuit power supply circuit 140 may be connected to the anode of the diode 103 and convert the rectified voltage before being smoothed by the capacitor 104 to generate the power supply voltage of the control circuit. For example, when the variable resistance circuit 107 and the resistance value setting circuit 108 shown in FIG. 6 are configured, the output voltage of the regulator circuit 126 can be smoothed to generate the power supply voltage of the control circuit. However, in this case, when charging of the capacitor 104 is completed, the rectified current is increased by the amount of current flowing through the control circuit power supply circuit 140, which is contrary to the aim of making the rectified current smaller than the reference current. In other words, this is equivalent to reducing the resistance value of the variable resistance circuit 107 by the resistance value of the control circuit power supply circuit 140. Therefore, such a configuration is not suitable for the LED lighting device of the present invention.

  On the other hand, if the control circuit power supply circuit 140 is connected as shown in FIG. 8, the control circuit power supply is supplied during the period from the completion of charging of the capacitor 104 until the charging of the capacitor 104 resumes, that is, during the discharging period of the capacitor 104. The circuit 140 is disconnected from the AC power supply 100. That is, when the capacitor 104 is completely charged, the current flowing through the control circuit power supply circuit 140 does not increase the rectified current. Therefore, it can be said that this is an effective connection method for making the rectified current smaller than the reference current.

  In addition to providing the control circuit power supply circuit 140 as shown in FIG. 8, the power supply voltage of the control circuit may be generated using the voltage generated in the DC-DC conversion circuit 105. For example, a method of providing an auxiliary winding on the choke coil 136 is conceivable. This method is also similar to the method of FIG. 8 in that the DC voltage of the capacitor 104 is converted to generate the power supply voltage of the control circuit, and the same effect can be realized.

DESCRIPTION OF SYMBOLS 100 AC power supply 101 Dimmer 102 Rectifier circuit 103, 134 Diode 104, 113, 137 Capacitor 105 DC-DC conversion circuit 106 LED load 107 Variable resistance circuit 108 Resistance value setting circuit 109 Current setting circuit 110 Triac 111, 116, 117, 120, 121, 123, 129, 130, 132, 138, 141 Resistance 112 Variable resistance 114 Diac 115 Load 118, 127 Comparator 119, 128 DC voltage source 122, 125, 131, 135, 143 MOSFET
124, 142 Zener diode 126 Regulator circuit 133 Diode bridge 136 Choke coil 139 Control circuit 140 Power supply circuit for control circuit

Claims (4)

A rectifier circuit for converting a phase-controlled AC power supply voltage into a rectified voltage, a capacitor connected to a DC output of the rectifier circuit via a diode, smoothing the rectified voltage to generate a DC voltage, and the DC voltage An LED lighting device comprising: a DC-DC conversion circuit that converts and supplies power to an LED load; and a current setting circuit that outputs a current setting value of the DC-DC conversion circuit based on the rectified voltage,
A variable resistance circuit connected to a DC output of the rectifier circuit; and a resistance value setting circuit that varies a resistance value of the variable resistance circuit based on the rectified voltage;
The variable resistance circuit includes a series body of a resistor and a switching element,
The resistance value setting circuit controls the switching element to be turned off when the rectified voltage is higher than a desired reference voltage, and increases the resistance value of the variable resistance circuit,
The resistance value setting circuit compares a regulator circuit that clamps the rectified voltage with a desired voltage value and an output voltage of the regulator circuit with a desired threshold value to determine whether the rectified voltage is higher than the reference voltage. An LED lighting device , wherein the series body is connected to an output of the regulator circuit . The LED lighting device according to claim 1,
The regulator circuit includes a resistor, a semiconductor element, and a Zener diode, and clamps the rectified voltage with a Zener voltage of the Zener diode . In the LED lighting device according to claim 1 or 2,
The DC-DC conversion circuit controls a current output to the LED load according to the current setting value, converts a voltage generated on the cathode side of the diode, and converts the control circuit and the resistance value setting circuit. And a control circuit power supply circuit for generating a power supply voltage of the current setting circuit . In the LED lighting device according to claim 3,
The LED lighting device, wherein the control circuit power supply circuit is a regulator circuit including a resistor, a semiconductor element, and a Zener diode .