JP2010154656A - Dc power supply circuit, and led lighting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a DC power supply circuit which has high efficiency and can adjust an output voltage against fluctuation of the received power voltage and to provide a highly efficient LED lighting device using a DC power supply and having high LED light emitting quality. <P>SOLUTION: The DC power supply circuit of a capacitor input system includes a rectifier 6 connected to an AC power supply 5 and a smoothing capacitor C1 connected to output of the rectifier 6, and it supplies power to a load 4 connected to an output terminal. The DC power supply circuit includes a first semiconductor switch SCR1 connected between the smoothing capacitor C1 and the output terminal in a direction where a charge of the smoothing capacitor C1 is discharged to the load and an ignition circuit of the first semiconductor switch SCR1, which supplies a gate signal to a gate of the first semiconductor switch SCR1 so that an ignition phase of the first semiconductor switch SCR1 is delayed as the AC power supply 5 becomes large beyond a first prescribed value. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a DC power supply circuit and an LED lighting device, and more particularly to a DC power supply circuit that is highly efficient and that can adjust an output voltage with respect to fluctuations in a received voltage, and an LED lighting device using the same.

Conventionally, fluorescent lamps and incandescent lamps have been generally used as lighting devices, but in recent years, LED lighting devices in which an LED unit in which a large number of LEDs are connected in series are driven by a switching power supply have come to be used. It was. For example, an example can be seen in Japanese Patent Application Laid-Open No. 11-135274 (Patent Document 1).
Japanese Patent Laid-Open No. 11-135274

The conventional LED lighting device performs output voltage adjustment with a voltage adjustment function of a switching power supply so that the load power supplied to the LED unit is constant. However, since the switching power supply that drives the LED unit includes a circuit that operates at a high frequency of several tens of kHz, the efficiency is stopped by about 90% due to the loss of this circuit.
On the other hand, if it is a capacitor input type DC power supply circuit composed of a rectifier circuit and a DC smoothing capacitor not including a circuit operating at a high frequency, the efficiency can be improved to about 97% to 98%. However, the capacitor input type DC power supply circuit has a problem in that the output voltage cannot be adjusted, and when the power reception voltage fluctuates, the output voltage fluctuates and the brightness of the LED becomes unstable.

  In view of the above problems, an object of the present invention is a high-efficiency, high-efficiency, high-efficiency LED lighting using a direct-current power supply circuit capable of adjusting an output voltage with respect to fluctuations in received voltage To provide an apparatus.

A DC power supply circuit according to the present invention includes a rectifier connected to an AC power supply and a smoothing capacitor connected to an output of the rectifier, and a capacitor input type DC power supply circuit that supplies power to a load connected to an output terminal. A first semiconductor switch connected between the smoothing capacitor and the output terminal in a direction to discharge the electric charge of the smoothing capacitor to the load; and the first power supply as the AC power source exceeds a first predetermined value. An ignition circuit for the first semiconductor switch for supplying a gate signal to a gate of the first semiconductor switch so that an ignition phase of the semiconductor switch is delayed is provided.
Further, the DC power supply circuit of the present invention is characterized in that the ignition circuit generates a reference voltage that decreases as the power supply peak voltage of the AC power supply exceeds the first predetermined value, and the reference voltage generation circuit, A voltage comparison circuit for comparing a reference voltage with the voltage at the output terminal and supplying a gate signal to the gate of the first semiconductor switch when the reference voltage exceeds a second predetermined value with respect to the voltage at the output terminal; It is characterized by.
The DC power supply circuit according to the present invention is characterized in that the reference voltage generation circuit includes reference voltage varying means for varying the reference voltage with respect to the same value of the power supply peak voltage of the AC power supply.
The DC power supply circuit according to the present invention is characterized in that a clamp circuit is provided for clamping the reference voltage to be greater than the second predetermined value.
In the DC power supply circuit of the present invention, the reference voltage is generated by inputting a voltage of the smoothing capacitor.
In the DC power supply circuit according to the present invention, the reference voltage generation circuit includes a first capacitor connected to the positive terminal of the smoothing capacitor, a positive terminal of the smoothing capacitor, and one terminal of a first resistor connected to the anode terminal. A first Zener diode, the first resistor having one terminal connected to the anode terminal of the first Zener diode and the other terminal connected to one terminal of the variable resistor, and the other terminal of the first resistor One terminal is connected to the variable resistor, the other terminal is connected to the negative electrode terminal of the smoothing capacitor, and the connection point is connected to the positive electrode terminal of the smoothing capacitor and one terminal of the first Zener diode. Is connected, and the other terminal is connected to the drain terminal of the second semiconductor switch, and the drain terminal is connected to one terminal of the second resistor. The second semiconductor switch having a source terminal connected to the negative terminal of the smoothing capacitor and a gate terminal connected to a connection point where the other terminal of the first resistor and one terminal of the variable resistor are connected; The voltage at the connection point between the other terminal of the second resistor and the drain terminal of the second semiconductor switch is output as the reference voltage.
In the DC power supply circuit of the present invention, the reference voltage is a second capacitor different from the smoothing capacitor, and can be full-wave rectified to the negative output terminal of the output terminal of the rectifier and the output terminal of the AC power supply. It is generated by inputting a voltage of the second capacitor connected through a diode.
In the DC power supply circuit according to the present invention, the reference voltage generating circuit is configured such that the cathode terminal is connected to one terminal of the second capacitor and the second capacitor, and one terminal of the first resistor is connected to the anode terminal. The first resistor, the first resistor having one terminal connected to the anode terminal of the first Zener diode and the other terminal connected to one terminal of the variable resistor; and the first resistor One terminal is connected to the other terminal, the other terminal is connected to the other terminal of the second capacitor, one terminal is connected to one positive terminal of the smoothing capacitor, and the other terminal Is connected to the drain terminal of the second semiconductor switch, the drain terminal is connected to the other terminal of the second resistor, and the source terminal is connected to the negative terminal of the smoothing capacitor. The second semiconductor switch connected to a connection point where the other terminal of the first resistor and one terminal of the variable resistor are connected, and the other terminal of the second resistor; The voltage at the connection point of the drain terminal of the second semiconductor switch is output as the reference voltage.
The DC power supply circuit according to the present invention is characterized in that the first semiconductor switch is any one of a thyristor, a GTO, and a triac.
In the DC power supply circuit of the present invention, the second semiconductor switch is a MOS transistor or a bipolar transistor.
Further, the LED lighting device of the present invention is characterized in that an LED lighting unit is connected to an output terminal of the DC power supply circuit.

  According to the present invention, it is possible to provide a DC power supply circuit that is highly efficient and that can adjust an output voltage with respect to fluctuations in the received voltage, and a LED lighting device that uses this DC power supply and has high efficiency and high LED emission quality.

  Next, the best mode for carrying out the present invention will be specifically described with reference to the drawings.

(First embodiment)
FIG. 1 shows a circuit configuration of an LED lighting device 1 according to the first embodiment of the present invention. The LED lighting device 1 according to the present embodiment shown in FIG. 1 includes a rectifying circuit 2, a DC smoothing circuit 3, an LED lighting unit 4, and the like. The rectifying circuit 2 is connected to an AC power source 5 such as a commercial power source.

  The rectifier circuit 2 is composed of a full-wave rectifier 6 in which a diode is bridged. Although not shown, a power fuse, a noise suppression capacitor, a current reduction impedance, and the like may be connected for protection.

  The DC smoothing circuit 3 includes diodes D1 and D2, a smoothing capacitor C1, resistors R1 and R2, a variable resistor VR1, a thyristor SCR1, Zener diodes ZD1 and ZD2, a semiconductor switch MOS1, and the like.

The semiconductor switch MOS1 has an N-channel MOS transistor (N-Channel Metal Oxide Semiconductor Field Effect).
However, the present invention is not limited to this, and for example, a bipolar transistor can also be used. The smoothing capacitor C1 can be an aluminum electrolytic capacitor, but is not limited thereto. The Zener diode ZD1 is a Zener diode having a Zener voltage of 7V, and the Zener diode ZD2 is a Zener diode having a Zener voltage of 130V. The Zener voltages of the Zener diodes ZD1 and ZD2 are not intended to be limited to 7V and 130V, but are merely examples, and can be appropriately changed within the scope of the present invention. The thyristor SCR1 is used as a discharging switch element for the smoothing capacitor C1, and is also not limited to the thyristor, and is not limited to the GTO (Gate
Turn-Off thyristor), triac, etc. can be used instead.

  The LED lighting unit 4 is formed by connecting a plurality of LEDs (Light Emitting Diodes) and a current limiting resistor R0 connected in series to each other in parallel. Can also be used.

  The resistors R1, R2, variable resistor VR1, diode D2, Zener diodes ZD1, ZD2, and semiconductor switch MOS1 in the DC smoothing circuit 3 constitute an ignition circuit of the thyristor SCR1, and the resistors R1, R2, variable resistance in this ignition circuit VR1, Zener diode ZD2, and semiconductor switch MOS1 constitute a reference voltage generation circuit 7 that receives the voltage of the smoothing capacitor C1 and generates a reference voltage Vs1 as will be described later.

Next, the connection relationship of each component of the LED lighting apparatus 1 which is this Embodiment is demonstrated.
The full-wave rectifier 6 has an input terminal connected to the AC power supply 5 and a positive output terminal and a negative output terminal connected to the DC smoothing circuit 3 and the LED illumination unit 4.

  The positive output terminal of the full-wave rectifier 6 is connected to the anode terminal of the diode D1 and the cathode terminal of the thyristor SCR1, and the cathode terminal of the diode D1 and the anode terminal of the thyristor SCR1 are commonly connected to the positive terminal of the smoothing capacitor C1. . The negative terminal of the smoothing capacitor C1 is connected to the negative output terminal of the rectifier bridge 6. As can be seen from this configuration, the diode D1 is used for charging the smoothing capacitor C1, and the thyristor SCR1 is used for discharging the smoothing capacitor C1.

  The configuration of the reference voltage generation circuit 7 will be further described. The cathode terminal of the Zener diode ZD2 is connected to the positive electrode terminal of the smoothing capacitor C1, and one terminal of the resistor R2 is connected to the anode terminal of the Zener diode ZD2. One terminal of the variable resistor VR1 is connected to the other terminal of the resistor R2, and the other terminal of the variable resistor VR1 is connected to the negative terminal of the smoothing capacitor C1. Further, one terminal of the resistor R1 is connected to the positive terminal of the smoothing capacitor C1, and the other terminal of the resistor R1 is connected to the drain terminal of the semiconductor switch MOS1. The source terminal of the semiconductor switch MOS1 is connected to the negative terminal of the smoothing capacitor C1. The gate terminal of the semiconductor switch MOS1 is connected to a connection point between the other terminal of the resistor R2 and one terminal of the variable resistor VR1. Here, the voltage at the connection point where the other terminal of the resistor R1 and the drain terminal of the semiconductor switch MOS1 are connected is the reference voltage Vs1.

  The cathode terminal of the Zener diode ZD1 is connected to the connection point (reference voltage Vs1 generation point) where the other terminal of the resistor R1 and the drain terminal of the semiconductor switch MOS1 are connected. The anode terminal of the Zener diode ZD1 is connected to the anode of the diode D2. It is connected. The cathode terminal of the diode D2 is connected to the gate terminal of the thyristor SCR1.

  Here, specific values of each component having the above-described configuration in the LED lighting device 1 in which the rated voltage of the AC power supply 5 is 100 V and the rated frequency is 50 Hz are given as examples (they can be changed as appropriate, and the present invention can be changed). Not limited), resistance value of resistor R1 = 120 kΩ, resistance value of resistor R2 = 120 kΩ, resistance value of variable resistor VR1 = 50 kΩ, capacitance value of smoothing capacitor C1 = 10 μF, Zener diode ZD1 = Zener voltage 130V, Zener Diode ZD2 = Zener voltage 7V. However, it is considered that the received voltage of the AC power supply 5 varies as will be described later. In the following description, these values will be described as examples.

  In the present embodiment, when the reference voltage Vs1 generated by the reference voltage generation circuit 7 is higher than the Zener voltage 7V of the Zener diode ZD1 with respect to the gate terminal voltage (approximately equal to the output voltage V0) of the thyristor SCR1, The thyristor SCR1 is turned on, the smoothing capacitor C1 is discharged, and power is supplied from the smoothing capacitor C1 to the load.

  Next, the reference voltage Vs1 generated by the reference voltage generation circuit 7 will be described with reference to FIG. FIG. 2 shows the C1 voltage Vc1 that is the charging voltage of the smoothing capacitor C1 and the reference voltage generated by the reference voltage generation circuit 7 with respect to the power supply peak voltage from the AC power supply 5 (= the rectified voltage peak value of the full-wave rectifier 6). The characteristic of voltage Vs1 is shown. The C1 voltage Vc1 characteristic of FIG. 2 assumes that the smoothing capacitor C1 is charged with the power supply peak voltage (the rectified voltage peak value of the full-wave rectifier 6). Therefore, the C1 voltage Vc1 has a linear characteristic with respect to the power supply peak voltage. When the C1 voltage Vc1 rises and reaches the point of the Zener voltage ZV2 of the Zener diode ZD2, the Zener diode ZD2 is turned on, and a current flows through the Zener diode ZD2, the resistor R2, and the variable resistor VR1. Since the gate terminal of the semiconductor switch MOS1 is connected to the connection point between the other terminal of the resistor R2 and one terminal of the variable resistor VR1, the semiconductor switch MOS1 exceeds 130V from the point of 130V when the Zener diode ZD2 is turned on. The drain voltage (that is, the reference voltage Vs1) decreases in proportion to the voltage. The one-dot chain line in FIG. 2 shows the characteristics of the reference voltage Vs1 at this time. As shown in FIG. 2, when the power supply peak voltage is a little less than 160V (about 157V), the reference voltage Vs1 becomes almost 0V.

  3 to 5 show waveforms of the C1 voltage Vc1, the reference voltage Vs1, and the output voltage V0 when the power supply voltage of the AC power supply 5 fluctuates. FIG. 3 shows a case where the power supply peak voltage is 130 V or less. FIG. 5 shows a case where the power supply peak voltage is 150V, and FIG.

  With reference to FIG. 3, operation | movement of the LED lighting apparatus 1 is demonstrated about the case where a power supply peak voltage is 130 V or less. When the power supply peak voltage is 130V or less, the Zener diode ZD2 having a Zener voltage of 130V is in an off state, so that no current flows through the series body in which the Zener diode ZD2, the resistor R2, and the variable resistor VR1 are connected in series. The gate voltage is 0V. Therefore, at this time, the semiconductor switch MOS1 is turned off, and the drain terminal voltage (that is, the reference voltage Vs1) is equal to the voltage of the smoothing capacitor C1.

  At time t1, the smoothing capacitor C1 is peak-charged with the power supply peak voltage (130 V or less) by the rectified voltage from the full-wave rectifier 6, and this voltage is maintained until the thyristor SCR1 is turned on at time t2. At time t2 when the instantaneous value of the power supply voltage is 7V lower than the C1 voltage Vc1, the voltage applied to the Zener diode ZD1 becomes 7V, and the Zener diode ZD1 is turned on from this point. When the Zener diode ZD1 is turned on and the voltage input to the gate terminal of the thyristor SCR1 exceeds the on threshold value of the thyristor SCR1, the thyristor SCR1 is turned on. Accordingly, the smoothing capacitor C1 supplies power to the LED lighting unit 4 as a load through the thyristor SCR1. At this time, the output voltage V0 increases stepwise up to approximately the C1 voltage Vc1 (a voltage that is smaller by the ON voltage of the thyristor SCR1). Thereafter, since the smoothing capacitor C1 supplies current to the load, the voltage gradually decreases, and this state continues until time t3 when the instantaneous value of the rectified voltage of the full-wave rectifier 6 increases to the C1 voltage Vc1. When the time t3 elapses, the instantaneous value of the rectified voltage of the full-wave rectifier 6 exceeds the C1 voltage Vc1, so that the reverse voltage is applied to the thyristor SCR1 and the off state is entered. Thereafter, the smoothing capacitor C1 is peak-charged to the power supply peak voltage by the rectified voltage of the full-wave rectifier 6. This is repeated thereafter.

  With reference to FIG. 4, operation | movement of the LED lighting apparatus 1 is demonstrated about the case where a power supply peak voltage is 150V. When the power supply peak voltage is 150V, the Zener diode ZD2 having a Zener voltage of 130V is turned on, so that a current flows through a series body in which the Zener diode ZD2, the resistor R2, and the variable resistor VR1 are connected in series. A voltage divided by the resistance ratio of the resistor R2 and the variable resistor VR1 is applied to the gate voltage. Then, the semiconductor switch MOS1 is turned on, and the drain voltage (that is, the reference voltage Vs1) of the semiconductor switch MOS1 decreases almost in proportion to the divided voltage. When the smoothing capacitor C1 is peak-charged at the power supply peak voltage 150V, it is approximately 40V.

  At time t4, the smoothing capacitor C1 is peak-charged with the power supply peak voltage (150V) by the power supply voltage from the full-wave rectifier 6, and this voltage is maintained until the thyristor SCR1 is turned on at time t5. Time t5 when the rectified voltage instantaneous value of the full-wave rectifier 6 is 7V lower than the reference voltage Vs1 (this voltage changes as shown in FIG. 2 depending on the power supply peak voltage, but is 40V in the example of FIG. 4). , The voltage applied to the Zener diode ZD1 becomes 7V, and the Zener diode ZD1 is turned on from this point. When the Zener diode ZD1 is turned on and the voltage input to the gate terminal of the thyristor SCR1 exceeds the on threshold value of the thyristor SCR1, the thyristor SCR1 is turned on. Accordingly, the smoothing capacitor C1 supplies power to the LED lighting unit 4 that is a load through the thyristor SCR1, and at this time, the output voltage V0 increases in a stepped manner up to approximately the C1 voltage Vc1 (a voltage that is smaller by the ON voltage of the thyristor SCR1). . Thereafter, since the smoothing capacitor C1 supplies current to the load, the voltage gradually decreases, and this state continues until time t6 when the instantaneous value of the power supply voltage reaches the C1 voltage Vc1. As the smoothing capacitor C1 gradually decreases during the time t5 to t6, the gate voltage of the semiconductor switch MOS1 gradually decreases and the drain voltage gradually increases. When the time t6 elapses, the instantaneous value of the rectified voltage of the full-wave rectifier 6 exceeds the C1 voltage Vc1, so that a reverse voltage is applied to the thyristor SCR1 and the thyristor SCR1 is turned off. Thereafter, the smoothing capacitor C1 is peak-charged to the power supply peak voltage by the rectified voltage from the full-wave rectifier 6. At this time, since the gate voltage of the semiconductor switch MOS1 increases, the reference voltage Vs1 also decreases and becomes approximately 40 V at time t7 (t4). This is repeated thereafter.

  With reference to FIG. 5, operation | movement of the LED lighting apparatus 1 is demonstrated about the case where a power supply peak voltage is 160V. When the power supply peak voltage is 160V, the Zener diode ZD2 having a Zener voltage of 130V is in an on state, and a current flows through a series body in which the Zener diode ZD2, the resistor R2, and the variable resistor VR1 are connected in series. A voltage divided by the resistance ratio of the resistor R2 and the variable resistor VR1 is applied to the gate voltage of. At this time, the drain voltage (that is, the reference voltage Vs1) of the semiconductor switch MOS1 drops to almost 0V. This is also shown in FIG. 2 in the characteristic that the reference voltage Vs1 becomes 0V when it is about 160V or more.

  When the power supply peak voltage is 160V, the reference voltage Vs1 becomes 0V as described above. Therefore, even if the instantaneous value of the rectified voltage of the full-wave rectifier 6 becomes 0V, the difference from the reference voltage Vs1 cannot be reduced to 7V. . Therefore, the thyristor SCR1 remains off for the entire period. In this state, as shown in FIG. 5, the output voltage V0 becomes the rectified voltage itself of the full-wave rectifier 6, the smoothing capacitor C1 is maintained charged with the peak voltage of the full-wave rectifier 6, and the reference voltage Vs1. Is in a state of maintaining approximately 0V.

  As can be seen from the above description, according to the present embodiment, the timing at which the thyristor SCR1 is turned on (that is, the discharge of the smoothing capacitor C1) in the range of the phase of the power supply voltage from 90 degrees to 180 degrees as the power supply voltage increases. (Timing) can be delayed, an increase in the output voltage can be suppressed, and there is an effect of stabilizing the power supplied to the load.

FIG. 6 is a diagram for explaining a power adjustment function for adjusting the power supplied to the load by adjusting the output voltage V0 of the DC smoothing circuit 3 of the present embodiment with the variable resistor VR1. FIG. 6 shows characteristics in which the horizontal axis represents the AC input voltage (effective value V) of the power supply voltage, and the vertical axis represents the output power supplied from the DC smoothing circuit 3 to the LED lighting unit 4. FIG. 6 shows that the output power can be adjusted by adjusting the variable resistor VR1. Although three values of the variable resistance VR1 are illustrated, when the value of VR1 changes continuously, the characteristic also changes continuously in the direction of the arrow as the resistance value increases.
Characteristic 1 is an output power characteristic in a region where the power supply peak voltage is lower than the Zener voltage 130V of the Zener diode ZD2, and is a characteristic when the Zener diode ZD2 is in the OFF state. At this time, the output voltage V0 has the waveform shown in FIG.

  Points a1, a2, and a3 indicate points where the Zener diode ZD2 becomes conductive and the semiconductor switch MOS1 starts to turn on. Points a1 to b1, points a2 to b2, and points a3 to b3 are characteristics when the reference voltage Vs1 drops from 130V toward 0V, and the output voltage V0 has a waveform as shown in FIG. Points a1, a2, and a3 are points where the semiconductor switch MOS1 starts to be turned on, and are shifted to the low voltage side of the AC input voltage as the value of the variable resistor VR1 increases. This is because as the value of the variable resistor VR1 increases, the gate voltage of the semiconductor switch MOS1 divided by the resistor R2 and the variable resistor VR1 increases, and the semiconductor switch MOS1 starts to turn on earlier.

  Points b1, b2, and b3 indicate points at which the thyristor SCR1 cannot be turned on when the reference voltage Vs1 in FIG. 4 reaches 7V and further decreases. When the power supply peak voltage rises further and the reference voltage Vs1 becomes 7V or less, the thyristor SCR1 is not turned on, and at time t5 to t6, the thyristor SCR1 is turned on and the voltage of the smoothing capacitor C1 that contributed to the output voltage is lost. The process proceeds to the characteristic 2 in the case of only the output voltage of the full-wave rectifier 6 stepwise. At this time, the output voltage V0 has the waveform shown in FIG.

  Further, since the gate voltage of the semiconductor switch MOS1 increases with respect to the same voltage value of the same smoothing capacitor C1 as the value of the variable resistor VR1 increases, the degree of the decrease of the reference voltage Vs1 increases as the voltage value of the smoothing capacitor C1 increases. . That is, as the value of the variable resistor VR1 increases, the time between the times t4 and t5 shown in FIG. 4 becomes longer, the timing at which the thyristor SCR1 is turned on is delayed, and the discharge of the smoothing capacitor C1 is reduced. The arrows in FIG. 6 indicate the characteristic change as the resistance value of the variable resistor VR1 is increased.

  As described above, according to the present embodiment, the output power can be adjusted by the variable resistor VR1, the output voltage is suppressed when the power supply voltage is over the predetermined voltage, and the output voltage is stepped as the voltage further increases. Can be lowered.

(Second Embodiment)
FIG. 7 shows the configuration of the DC smoothing circuit portion of the LED lighting device 11 according to the second embodiment of the present invention. This embodiment is the same as that of the LED lighting device 1 according to the first embodiment. In the DC smoothing circuit 3, a Zener diode ZD3 is additionally connected to the drain terminal of the semiconductor switch MOS1. The Zener diode ZD3 has an anode terminal connected to the drain terminal of the semiconductor switch MOS1, and a cathode terminal connected to a connection point between the resistor R1 and the cathode terminal of the Zener diode ZD1. The Zener voltage of the Zener diode ZD3 is set to 12V that is slightly larger than the Zener voltage 7V of the Zener diode ZD1. Good). The Zener diode ZD3 becomes a clamp circuit that clamps with a voltage larger than the Zener voltage of the Zener diode ZD1 even when the power supply peak voltage of the AC power supply 5 increases and the reference voltage Vs2 decreases toward 0V. The DC smoothing circuit in the present embodiment is a DC smoothing circuit 13. Other configurations are the same as those of the first embodiment.

  The resistors R1, R2, variable resistor VR1, diode D2, Zener diodes ZD1, ZD2, ZD3, and semiconductor switch MOS1 in the DC smoothing circuit 13 constitute an ignition circuit of the thyristor SCR1, and the resistors R1, R2, variable in the ignition circuit The resistor VR1, the Zener diodes ZD2 and ZD3, and the semiconductor switch MOS1 constitute a reference voltage generation circuit 17 that generates the reference voltage Vs2.

  Next, the reference voltage Vs2 generated by the reference voltage generation circuit 17 will be described with reference to FIG. FIG. 8 shows the C1 voltage Vc1 that is the charging voltage of the smoothing capacitor C1 and the reference voltage generated by the reference voltage generation circuit 17 with respect to the power supply peak voltage from the AC power supply 5 (rectified voltage peak value of the full-wave rectifier 6). The characteristic of Vs2 is shown. The C1 voltage Vc1 characteristic in FIG. 8 assumes that the smoothing capacitor C1 is charged with the power supply peak voltage. Therefore, the C1 voltage Vc1 has a linear characteristic with respect to the power supply peak voltage. When the C1 voltage Vc1 rises and reaches the point of the Zener voltage ZV2 of the Zener diode ZD2, the Zener diode ZD2 is turned on, and a current flows through the Zener diode ZD2, the resistor R2, and the variable resistor VR1. Since the gate terminal of the semiconductor switch MOS1 is connected to the connection point between the other terminal of the resistor R2 and one terminal of the variable resistor VR1, the semiconductor switch MOS1 exceeds 130V from the point of 130V when the Zener diode ZD2 is turned on. The drain voltage (that is, the reference voltage Vs2) decreases in proportion to the voltage. The one-dot chain line in FIG. 8 shows the characteristics of the reference voltage Vs2 at this time. The reference voltage Vs1 in the first embodiment has a power supply peak voltage of slightly less than 160V (about 157V) and the reference voltage Vs1 is almost 0V. In the present embodiment, the reference voltage Vs2 is the zener voltage 12V of the zener diode ZD3. Since it exists, it becomes 12V at about 155V, and even if the power supply peak voltage further increases, it does not decrease below 12V.

  When the power supply peak voltage is 130 V or less, the waveform of the reference voltage Vs2 is the same as the waveform of the reference voltage Vs1 in FIG. 3 in the first embodiment, and therefore the operation is the same as that of the first embodiment. Also in this embodiment, when the power supply peak voltage is 130 V or less, the semiconductor switch MOS1 is in the off state, and the Zener diode ZD3 does not affect the operation at all. Therefore, since it is the same as the operation of FIG. 3 of the first embodiment, the description is omitted.

  When the power supply peak voltage is 150 V, the waveform of the reference voltage Vs2 is the same as the waveform of the reference voltage Vs1 in FIG. 4 in the first embodiment, and therefore the operation is almost the same as in the first embodiment. . More specifically, when the power supply peak voltage is 150 V and the semiconductor switch MOS1 is in the on state, the reference voltage Vs1 is higher than the drain voltage of the semiconductor switch MOS1 by the Zener voltage 12V of the Zener diode ZD3. Points e1, e2, and e3 shown in FIG. 10 described later are obtained by shifting the points a1, a2, and a3 in FIG. 6 shown in the first embodiment to the high voltage side of the AC input voltage. However, the basic operation is the same as the operation in the first embodiment, and a description thereof is omitted here.

  When the power supply peak voltage is 160V, the reference voltage Vs2 does not decrease to 12V or lower, so that the operation is as shown in FIG. 9 unlike FIG. 5 in the first embodiment. With reference to FIG. 9, the operation of the LED lighting device 11 will be described in the case where the power supply peak voltage is 160V. When the power supply peak voltage is 160V, the Zener diode ZD2 having a Zener voltage of 130V is turned on, so that a current flows through a series body in which the Zener diode ZD2, the resistor R2, and the variable resistor VR1 are connected in series. A voltage divided by the resistance ratio of the resistor R2 and the variable resistor VR1 is applied to the gate voltage. The semiconductor switch MOS1 is turned on, and the drain voltage (that is, the reference voltage Vs2) of the semiconductor switch MOS1 applied via the resistor R1 decreases almost in proportion to the divided voltage.

  As shown in FIG. 9, at time t8, the smoothing capacitor C1 is peak-charged with the power supply peak voltage (160V) by the power supply voltage from the full-wave rectifier 6, and this voltage is maintained until the thyristor SCR1 is turned on at time t9. Maintained. When the power supply peak voltage is 160V, the Zener diode ZD2 having a Zener voltage of 130V is in an on state, and a current flows through a series body in which the Zener diode ZD2, the resistor R2, and the variable resistor VR1 are connected in series. A voltage divided by the resistance ratio of the resistor R2 and the variable resistor VR1 is applied to the gate voltage of. At this time, the drain voltage of the semiconductor switch MOS1 drops to almost 0V. Since the Zener diode ZD3 is connected to the drain terminal of the semiconductor switch MOS1, the voltage at the connection point between the resistor R1 and the cathode terminal of the Zener diode ZD3 (that is, the reference voltage Vs2) is about 12V.

  At time t9 when the instantaneous value of the power supply voltage is 7V lower than the reference voltage Vs2 (12V), the voltage applied to the Zener diode ZD1 becomes 7V, and the Zener diode ZD1 is turned on from this point. When the Zener diode ZD1 is turned on and the voltage input to the gate terminal of the thyristor SCR1 exceeds the on threshold value of the thyristor SCR1, the thyristor SCR1 is turned on. Accordingly, the smoothing capacitor C1 supplies power to the LED lighting unit 4 that is a load through the thyristor SCR1, and at this time, the output voltage V0 increases in a stepped manner up to approximately the C1 voltage Vc1 (a voltage that is smaller by the ON voltage of the thyristor SCR1). . Thereafter, since the smoothing capacitor C1 supplies current to the load, the voltage gradually decreases, and this state continues until time t10 when the instantaneous value of the power supply voltage increases to the C1 voltage Vc1. As the smoothing capacitor C1 gradually decreases from time t9 to t10, the gate voltage of the semiconductor switch MOS1 gradually decreases and the drain voltage gradually increases. When the time t10 elapses, the instantaneous value of the power supply voltage becomes higher than the C1 voltage Vc1, so that a reverse voltage is applied to the thyristor SCR1 and the power supply voltage is turned off. Thereafter, the smoothing capacitor C1 is peak-charged to the power supply peak voltage by the power supply voltage from the full-wave rectifier 6. At this time, since the gate voltage of the semiconductor switch MOS1 increases, the reference voltage Vs1 also decreases and becomes approximately 12V at time t11 (t8). This is repeated thereafter.

  Thus, in the present embodiment, a voltage of 7 V or higher is applied to the Zener diode ZD1 at the time t9 when the instantaneous value of the power supply voltage decreases to 5 V (= 12V-7V) or lower, and the Zener diode ZD1. Always turn on. As a result, the thyristor SCR1 is always turned on. Therefore, as shown in FIG. 5 of the first embodiment, the thyristor SCR1 does not turn on after the phase of the power supply voltage is 180 degrees, and b1 → d1, b2 → d2 as shown in FIG. , B3 → d3, the output voltage does not change in a step shape.

  As can be seen from the above description, according to the present embodiment, the discharge timing of the smoothing capacitor C1 can be delayed as the power supply voltage increases, so that an increase in output voltage can be suppressed and supplied to the load. There is an effect to stabilize the power to be.

  FIG. 10 is an explanatory diagram of a power adjustment function that adjusts the power supplied to the load by adjusting the voltage of the present embodiment with the variable resistor VR1. In FIG. 10, the horizontal axis represents the AC input voltage (effective value V) of the power supply voltage, and the vertical axis represents the output power characteristics of the DC smoothing circuit 13 when the LED lighting device 4 is connected. FIG. 10 shows that the output power can be adjusted by adjusting the variable resistor VR1. As in FIG. 6 of the first embodiment, three values of the variable resistor VR1 are illustrated. However, when the value of VR1 changes continuously, the characteristics continue in the direction of the arrow as the resistance value is increased. Change. Characteristic 1 is a characteristic when the power supply peak voltage is lower than the Zener voltage of the Zener diode ZD2 and the Zener diode ZD2 is in the OFF state. The output voltage V0 has the waveform shown in FIG. 3 as in the first embodiment.

  Points e1, e2, and e3 indicate points at which the Zener diode ZD2 starts to conduct. Points e1 to g1, points e2 to g2, and points e3 to g3 are obtained when the reference voltage Vs2 (the output voltage V0 has a difference corresponding to the Zener voltage 12V of the Zener diode ZD3) decreases from 130V toward 0V. The characteristics are as shown in FIG. 4 as in the first embodiment. Point g1, point g2, and point g3 indicate points where the reference voltage Vs2 is 12V when the reference voltage Vs1 is set to the reference voltage Vs2 in FIG. 4, and the instantaneous value of the power supply voltage reaches 5V. When the instantaneous value of the power supply voltage falls below this, the thyristor SCR1 is turned on. A characteristic 3 is an output voltage characteristic when the thyristor SCR1 is kept on from time t8 to t10 as shown in FIG. The output voltage V0 has the waveform shown in FIG. As described above, the points e1, e2, and e3 shift the points a1, a2, and a3 in FIG. 6 shown in the first embodiment to the high voltage side of the AC input voltage due to the influence of the Zener diode ZD3. Will be.

  As described above, according to the present embodiment, the output power can be adjusted by the variable resistor VR1, and the output voltage is suppressed when the power supply voltage is in an overvoltage state equal to or higher than a predetermined value, and the first embodiment in FIG. The output voltage does not change stepwise as shown by b1 → d1, b2 → d2, and b3 → d3.

(Third embodiment)
FIG. 11 shows a configuration of an LED lighting device 21 according to the third embodiment of the present invention. In this embodiment, a reference voltage generation circuit 27 having a different configuration is used instead of the reference voltage generation circuit 7 of the first embodiment. The other configuration is the same as that of the first embodiment. Hereinafter, the configuration of the reference voltage generation circuit 27 different from the first embodiment will be mainly described, and the other will be described as appropriate.

  The reference voltage generation circuit 27 includes a smoothing capacitor C1, diodes D3 and D4, resistors R1 to R3, a Zener diode ZD2 having a Zener voltage of 130V, and a Zener diode ZD4 having a Zener voltage of 150V (the Zener voltage 150V is an example. It may be set to a value slightly larger than the Zener voltage of ZD2), variable resistor VR1, semiconductor switch MOS1, and capacitor Ct.

  The anode terminals of the diodes D3 and D4 are connected to both AC output terminals of the power supply circuit 5 (and the AC input terminal of the full-wave rectifier 6), and the cathode terminals of the diodes D3 and D4 are commonly connected to one terminal of the resistor R3. Has been. The other terminal of the resistor R3 is connected to a connection point where the cathode terminal of the Zener diode ZD2, the cathode terminal of the Zener diode ZD4, and one terminal of the capacitor Ct are connected in common. The other terminal of the capacitor Ct and the anode terminal of the Zener diode ZD4 are connected to the negative terminal of the full-wave rectifier 6, and the anode terminal of the Zener diode ZD2 is connected to one terminal of the resistor R2. One terminal of the variable resistor VR1 is connected to the other terminal of the resistor R2, and the other terminal of the variable resistor VR1 is connected to the negative terminal of the smoothing capacitor C1. Further, one terminal of the resistor R1 is connected to the positive terminal of the smoothing capacitor C1, and the other terminal of the resistor R1 is connected to the drain terminal of the semiconductor switch MOS1. The source terminal of the semiconductor switch MOS1 is connected to the negative terminal of the smoothing capacitor C1. The gate terminal of the semiconductor switch MOS1 is connected to a connection point between the other terminal of the resistor R2 and one terminal of the variable resistor VR1. Here, the voltage at the connection point where the other terminal of the resistor R1 and the drain terminal of the semiconductor switch MOS1 are connected is the reference voltage Vs3.

  The reference voltage Vs3 generated by the reference voltage generation circuit 27 is the same as the characteristic described with reference to FIG. 2 of the first embodiment. That is, the capacitor Ct is charged with the same voltage as the power supply peak voltage of the full-wave rectifier 6 through the diodes D3 and D4. The capacitor Ct is clamped to 150 V by the Zener diode ZD4. The relationship between the voltage of the capacitor Ct and the reference voltage Vs3 is the same as the relationship between the voltage of the smoothing capacitor C1 and the reference voltage Vs1 in the first embodiment.

  When the power supply peak voltage is 130 V or less, the waveform of the reference voltage Vs1 in FIG. 3 is the same as that of the reference voltage Vs2, and the operation of the LED lighting device 21 is the same as that of the first embodiment. Therefore, description of the operation when the power supply peak voltage is 130 V or less is omitted.

  With reference to FIG. 12, operation | movement of the LED lighting apparatus 21 is demonstrated about the case where a power supply peak voltage is 150V. When the power supply peak voltage is 150V, the voltage of the capacitor Ct is not clamped by the Zener diode ZD4 and rises to 150V. At this time, the Zener diode ZD2 having a Zener voltage of 130V is turned on, so that a current flows through a series body in which the Zener diode ZD2, the resistor R2, and the variable resistor VR1 are connected in series. Therefore, the gate voltage of the semiconductor switch MOS1 And a voltage divided by the resistance ratio of the variable resistor VR1 is applied. The semiconductor switch MOS1 is turned on, and the drain voltage (that is, the reference voltage Vs1) of the semiconductor switch MOS1 decreases almost in proportion to the divided voltage. When the capacitor Ct is peak-charged at the power supply peak voltage 150V, the reference voltage Vs3 is approximately 40V (this voltage changes as shown in FIG. 2 depending on the power supply peak voltage, but in the example of FIG. It is).

  At time t12, the smoothing capacitor C1 is peak-charged with the power supply peak voltage (150V) by the rectified voltage from the full-wave rectifier 6, and this voltage is maintained until the thyristor SCR1 is turned on at time t14. The instantaneous value of the power supply voltage, which is the reference voltage Vs3 (about 40 V in the example of FIG. 12), is kept almost constant until time t13, but starts to increase around time t13. This is because the capacity of the capacitor Ct is smaller than the capacity of the smoothing capacitor C1, and thus discharges faster than the smoothing capacitor C1. Accordingly, the gate voltage of the semiconductor switch MOS1 decreases and the reference voltage Vs3 increases from around time t13.

  When the reference voltage Vs3 becomes 7V higher than the instantaneous value of the power supply voltage at time t14, the voltage applied to the Zener diode ZD1 becomes 7V, and at this time, the Zener diode ZD1 is turned on. When the Zener diode ZD1 is turned on and the voltage input to the gate terminal of the thyristor SCR1 exceeds the on threshold value of the thyristor SCR1, the thyristor SCR1 is turned on. Accordingly, the smoothing capacitor C1 supplies power to the LED lighting unit 4 that is a load through the thyristor SCR1, and at this time, the output voltage V0 increases in a stepped manner up to approximately the C1 voltage Vc1 (a voltage that is smaller by the ON voltage of the thyristor SCR1). . Thereafter, since the smoothing capacitor C1 supplies current to the load, the voltage gradually decreases, and this state continues until time t15 when the instantaneous value of the rectified voltage of the full-wave rectifier 6 increases to the C1 voltage Vc1. From time t14 to t15, as the voltage of the capacitor Ct gradually decreases, the gate voltage of the semiconductor switch MOS1 also gradually decreases, and the voltage of the smoothing capacitor C1 also decreases. Accordingly, the reference voltage Vs3 is curved. To change.

  When the time t15 elapses, the instantaneous value of the power supply voltage exceeds the C1 voltage Vc1, so that a reverse voltage is applied to the thyristor SCR1 and the power supply voltage is turned off. Thereafter, the capacitor Ct and the smoothing capacitor C1 are peak charged to the power supply peak voltage by the rectified voltage from the full-wave rectifier 6. At this time, the gate voltage of the semiconductor switch MOS1 increases, whereby the reference voltage Vs1 also decreases and becomes approximately 40V at time t16. This is repeated thereafter.

With reference to FIG. 13, the operation will be described in the case where the power supply peak voltage is 160V.
At time t17, the smoothing capacitor C1 is peak charged with the power supply peak voltage (160V) by the power supply voltage from the full-wave rectifier 6, and this voltage is maintained until the thyristor SCR1 is turned on at time t20. Further, when the power supply peak voltage is 160V, the power supply peak voltage exceeds the Zener voltage 150V of the Zener diode ZD4. Therefore, the voltage of the capacitor Ct is clamped by the Zener diode ZD4 (the power supply peak voltage is reduced by the Zener characteristic of the Zener diode ZD4). When the level exceeding 150V increases, the Zener voltage changes accordingly to clamp at 150V). The Zener diode ZD2 having a Zener voltage of 130V is in an ON state, and a current flows through a series body in which the Zener diode ZD2, the resistor R2, and the variable resistor VR1 are connected in series. Therefore, the gate voltage of the semiconductor switch MOS1 includes the resistor R2 A voltage divided by the resistance ratio of the variable resistor VR1 is applied. At this time, the drain voltage (reference voltage Vs3) of the semiconductor switch MOS1 drops to almost 0V.

  After the time t17, the electric charge of the capacitor Ct is discharged by the capacitor Ct → the Zener diode ZD2 → the resistor R2 → the variable resistor VR1, but the reference voltage Vs3 is still smaller than 7V at the time t18 when the phase of the power supply voltage is 180 degrees. This is a state where the state of about 0V is maintained. Therefore, thyristor SCR1 is not yet turned on at time t18 when the phase of the rectified voltage from full-wave rectifier 6 is 180 degrees.

  When the voltage of the capacitor Ct reaches the time t19 when the time t18 has elapsed, the discharge of the capacitor Ct proceeds, whereby the reference voltage Vs3 starts to increase. In the region where the phase of the rectified voltage from the full-wave rectifier 6 after the time t19 has passed is 180 degrees or more, the rectified voltage from the full-wave rectifier 6 rises and the reference voltage Vs3 also rises, but at the time t20, the reference voltage Vs3 Exceeds the rectified voltage from the full-wave rectifier 6 by 7V. Then, at the time t20, the Zener diode ZD1 is turned on, and the thyristor SCR1 is turned on. Accordingly, the smoothing capacitor C1 supplies power to the LED lighting unit 4 that is a load through the thyristor SCR1, and at this time, the output voltage V0 increases in a stepped manner up to approximately the C1 voltage Vc1 (a voltage that is smaller by the ON voltage of the thyristor SCR1). . Thereafter, since the smoothing capacitor C1 supplies current to the load, the voltage gradually decreases, and this state continues until time t21 when the instantaneous value of the rectified voltage from the full-wave rectifier 6 increases to the C1 voltage Vc1.

  When the time t21 elapses, the instantaneous value of the rectified voltage from the full-wave rectifier 6 exceeds the C1 voltage Vc1, so that a reverse voltage is applied to the thyristor SCR1 and the thyristor SCR1 is turned off. Thereafter, the smoothing capacitor C1 is peak-charged to the power supply peak voltage by the power supply voltage from the full-wave rectifier 6. At this time, since the gate voltage of the semiconductor switch MOS1 increases, the reference voltage Vs1 also decreases and becomes approximately 0V by the time t21. This is repeated thereafter.

  As can be seen from the above description, according to the present embodiment, the output voltage V0 can be adjusted by turning on the thyristor SCR1 in a region where the phase of the power supply voltage is 180 degrees or more (a region where the time t18 has elapsed). Therefore, an increase in the output voltage can be suppressed in a wide phase range of the power supply voltage, and there is an effect of stabilizing the power supplied to the load. Also in this embodiment, the output power can be adjusted in the same manner as shown in FIG. 10 by adjusting the variable resistor VR1.

(Other embodiment 1)
In the above embodiment, the timing for turning on the thyristor SCR1 is performed by one of the DC smoothing circuits 3 (or 13, 23). However, a plurality of DC smoothing circuits 3 (or 13, 23) are connected in parallel, The timing for turning on the thyristor SCR1 can be made different. In order to make the timing of turning on the thyristor SCR1 different in each DC smoothing circuit, the value of the variable resistor VR1 provided in each DC circuit may be made different. Alternatively, the timing for turning on the thyristor SCR1 can be made different by changing the Zener voltages of the Zener diodes ZD1 and ZD2. In this way, the pulsation of the output voltage can be kept small.

  As described above, according to the present invention, in the capacitor input type DC power supply, the output voltage can be adjusted with a simple circuit, and the power supplied to the load can be stabilized.

  The embodiments have been specifically described above. However, these are merely examples, and the present invention is not limited to these embodiments.

  The DC power supply device of the present invention is suitable as a DC power supply device that supplies power to the LED lighting device, but the load is not limited to the LED lighting device and can be applied.

It is a figure which shows the circuit structure of the LED lighting apparatus which is 1st Embodiment by this invention. It is the figure which showed the reference voltage characteristic of the LED lighting apparatus which is 1st Embodiment by this invention. It is the figure which showed each part voltage waveform (when power supply peak voltage = 130V or less) of the LED lighting apparatus which is 1st Embodiment by this invention. It is the figure which showed each part voltage waveform (when power supply peak voltage = 150V) of the LED lighting apparatus which is 1st Embodiment by this invention. It is the figure which showed each part voltage waveform (when power supply peak voltage = 160V) of the LED lighting apparatus which is 1st Embodiment by this invention. It is the figure which showed the output electric power characteristic of the LED lighting apparatus which is 1st Embodiment by this invention. It is the figure which showed the structure of the direct current | flow smoothing circuit of the LED lighting apparatus which is 2nd Embodiment by this invention. It is the figure which showed the reference voltage characteristic of the LED lighting apparatus which is 2nd Embodiment by this invention. It is a figure which shows the operation | movement waveform of the DC power supply device which is 2nd Embodiment by this invention. It is the figure which showed each part voltage waveform (when power supply peak voltage = 160V) of the LED illuminating device which is 2nd Embodiment by this invention. It is a figure which shows the circuit structure of the LED lighting apparatus which is 3rd Embodiment by this invention. It is the figure which showed each part voltage waveform (when power supply peak voltage = 150V) of the LED lighting apparatus which is 3rd Embodiment by this invention. It is the figure which showed each part voltage waveform (when power supply peak voltage = 160V) of the LED lighting apparatus which is 3rd Embodiment by this invention.

Explanation of symbols

1, 21 ... LED lighting device 2 ... rectifier circuits 3, 13, 23 ... DC smoothing circuit 4 ... LED lighting unit 5 ... AC power supply 6 ... full-wave rectifiers 7,17, 27 ... reference voltage generation circuits D1-D4 ... diode C1 ... smoothing capacitor Ct ... capacitor R0-R3 ... resistor VR1 ... variable resistor SCR1 ... thyristors ZD1-ZD4 ... Zener diode MOS1... Semiconductor switch LED... Light emitting diode Vs1 to Vs3.

Claims (11)

In a rectifier connected to an AC power supply and a smoothing capacitor connected to the output of the rectifier, a capacitor input type DC power supply circuit that supplies power to a load connected to an output terminal,
A first semiconductor switch connected between the smoothing capacitor and the output terminal in a direction to discharge the electric charge of the smoothing capacitor to the load;
An ignition circuit for the first semiconductor switch that supplies a gate signal to the gate of the first semiconductor switch so that the ignition phase of the first semiconductor switch is delayed as the AC power source increases beyond the first predetermined value. A DC power supply circuit comprising: The ignition circuit is
A reference voltage generation circuit that generates a reference voltage that decreases as the power supply peak voltage of the AC power supply exceeds the first predetermined value;
A voltage comparison circuit that compares the reference voltage with the voltage at the output terminal and supplies a gate signal to the gate of the first semiconductor switch when the reference voltage exceeds a second predetermined value with respect to the voltage at the output terminal; The DC power supply circuit according to claim 1.   3. The DC power supply circuit according to claim 2, wherein the reference voltage generation circuit includes reference voltage varying means for varying the reference voltage with respect to the same value of the power supply peak voltage of the AC power supply.   4. The DC power supply circuit according to claim 2, further comprising a clamp circuit that clamps the reference voltage to be larger than the second predetermined value. 5.   5. The DC power supply circuit according to claim 2, wherein the reference voltage is generated by inputting a voltage of the smoothing capacitor. 6. The reference voltage generation circuit includes:
The smoothing capacitor;
A first Zener diode having a cathode terminal connected to the positive terminal of the smoothing capacitor and an anode terminal connected to one terminal of a first resistor;
The first resistor having one terminal connected to the anode terminal of the first Zener diode and the other terminal connected to one terminal of the variable resistor;
A variable resistor in which one terminal is connected to the other terminal of the first resistor and the other terminal is connected to a negative terminal of the smoothing capacitor;
A second resistor in which one terminal is connected to a connection point where the positive electrode terminal of the smoothing capacitor and one terminal of the first Zener diode are connected, and the other terminal is connected to the drain terminal of the second semiconductor switch;
A drain terminal is connected to one terminal of the second resistor, a source terminal is connected to the negative terminal of the smoothing capacitor, a gate terminal is connected to the other terminal of the first resistor and one terminal of the variable resistor. The second semiconductor switch connected to the connection point;
With
6. The direct current according to claim 2, wherein a voltage at a connection point between the other terminal of the second resistor and a drain terminal of the second semiconductor switch is output as the reference voltage. 6. Power supply circuit. The reference voltage is
The second capacitor is different from the smoothing capacitor, and the voltage of the second capacitor connected to the negative output terminal of the output terminal of the rectifier and the output terminal of the AC power supply via a diode so as to be capable of full-wave rectification is input. The DC power supply circuit according to claim 2, wherein the DC power supply circuit is generated as described above. The reference voltage generation circuit includes:
The second capacitor;
A first Zener diode having a cathode terminal connected to one terminal of the second capacitor and an anode terminal connected to one terminal of a first resistor;
The first resistor having one terminal connected to the anode terminal of the first Zener diode and the other terminal connected to one terminal of the variable resistor;
A variable resistor in which one terminal is connected to the other terminal of the first resistor and the other terminal is connected to the other terminal of the second capacitor;
A second resistor having one terminal connected to one positive electrode terminal of the smoothing capacitor and the other terminal connected to a drain terminal of a second semiconductor switch;
The drain terminal is connected to the other terminal of the second resistor, the source terminal is connected to the negative terminal of the smoothing capacitor, the gate terminal is connected to the other terminal of the first resistor and one terminal of the variable resistor. The second semiconductor switch connected to the connection point;
With
8. The voltage at a connection point between the other terminal of the second resistor and the drain terminal of the second semiconductor switch is output as the reference voltage. 8. DC power supply circuit according to item.   The DC power supply circuit according to any one of claims 1 to 8, wherein the first semiconductor switch is one of a thyristor, a GTO, and a triac.   The DC power supply circuit according to any one of claims 1 to 9, wherein the second semiconductor switch is a MOS transistor or a bipolar transistor.   An LED lighting device, wherein an LED lighting unit is connected to an output terminal of the DC power supply circuit according to claim 1.

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