JP2010165546A - Lighting device and illumination apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce electric power loss, and to comparatively freely set a current flowing through the light source, in a lighting device lighting a light source to be turned on by direct current. <P>SOLUTION: A conversion circuit 150 converts alternating current into direct current to turn on a light source LA. A choke coil L41 (impedance element) is electrically connected to the conversion circuit 150 in series. An alternating voltage generating circuit 110 generates alternating voltage to be applied to a series circuit of the choke coil L41 and the conversion circuit 150. A control circuit 160 controls a frequency of the alternating voltage generated by the alternating voltage generating circuit 110 based on the current detected by a current detection circuit 170. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a lighting device for lighting a light source that is lit by a direct current.

In order to reduce power consumption in lighting fixtures, inverter-type lighting fixtures using fluorescent lamps or the like as a light source are increasing. Moreover, using LED which is low power consumption as a light source is also performed.
Since the LED has a limited light distribution performance, the advantages of both can be utilized by using it in combination with a fluorescent lamp that can illuminate a wide area.

JP 2003-264090 A

In an inverter-type lighting fixture, a DC voltage (for example, 400 V) is generated from an AC voltage (for example, 50 Hz to 60 Hz, 100 V to 254 V) input from a commercial power source, and a high frequency AC voltage (for example, 50 kHz to 90 kHz) is generated from the generated DC voltage. ) And applied to a load circuit including a fluorescent lamp.
When the generated DC voltage is directly applied to an LED to light it, the number of LEDs to be electrically connected in series is determined by the relationship with the voltage drop per LED, and the degree of freedom in lighting fixture design is increased. Damaged.
In addition, when the generated DC voltage is stepped down and applied to the LED, if a step-down circuit using a resistor or the like is used, power loss occurs in the step-down circuit and the efficiency of the circuit decreases.

  The present invention has been made to solve the above-described problems, for example, in a case where a relatively high voltage DC power source is used in a lighting device for lighting a light source that is lit by a DC current such as an LED. Another object of the present invention is to make it possible to set the current flowing through the light source relatively freely with little power loss.

A lighting device according to the present invention includes a conversion circuit that converts an alternating current into a direct current for lighting a light source;
A series circuit having an impedance element having a frequency characteristic electrically connected in series with the conversion circuit;
And an AC voltage generation circuit that generates an AC voltage to be applied to the series circuit.

  According to the lighting device of the present invention, since the impedance element limits the current flowing through the light source, the AC voltage generation circuit generates even if the voltage value of the AC voltage generated by the AC voltage generation circuit is relatively high. By adjusting the frequency of the alternating voltage, the current flowing through the light source can be set relatively freely, and there is an effect that the power loss is small.

FIG. 3 is an overall configuration diagram illustrating a configuration of a lighting fixture 800 according to Embodiment 1. FIG. 3 is an electric circuit diagram illustrating a circuit configuration of the lighting device 100 according to the first embodiment. FIG. 6 shows an example of voltages and currents of respective parts of the lighting device 100 according to Embodiment 1. FIG. 6 shows a modification of the current detection circuit 170 in the first embodiment. FIG. 6 illustrates a modification of the conversion circuit 150 in Embodiment 1; FIG. 10 shows another modification of the conversion circuit 150 and the light source LA in the first embodiment. FIG. 6 is an overall configuration diagram illustrating a configuration of a lighting fixture 800 according to Embodiment 2. FIG. 6 is an overall configuration diagram showing a configuration of a lighting fixture 800 in Embodiment 3. FIG. 10 is an overall configuration diagram showing a modification of lighting fixture 800 in Embodiment 3. FIG. 6 is an overall configuration diagram illustrating a configuration of a lighting fixture 800 according to Embodiment 4.

Embodiment 1 FIG.
The first embodiment will be described with reference to FIGS.

FIG. 1 is an overall configuration diagram showing a configuration of a lighting fixture 800 in this embodiment.
The lighting fixture 800 includes the lighting device 100 and the light source LA. The light source LA is a light source such as an LED that is lit by a direct current. The lighting device 100 inputs power from an AC power source AC such as a commercial power source, generates a direct current for lighting the light source LA, and lights the light source LA.

The lighting device 100 includes an AC voltage generation circuit 110, a series circuit 140, a control circuit 160, a current detection circuit 170, and a voltage detection circuit 180.
The AC voltage generation circuit 110 receives AC power (for example, 50 Hz to 60 Hz, 100 V to 254 V) from the AC power source AC, converts the frequency and voltage, and generates an AC voltage (for example, 50 kHz to 100 kHz, 400 V). The AC voltage generation circuit 110 operates according to instructions from the control circuit 160.
The series circuit 140 is a load circuit for the AC voltage generation circuit 110 in which the choke coil L41, the coupling capacitor C42, and the conversion circuit 150 are electrically connected in series.
The coupling capacitor C42 is a capacitor for removing the DC component of the AC voltage generated by the AC voltage generation circuit 110, and has a sufficiently large capacitance. In the case where the AC voltage generated by the AC voltage generation circuit 110 has no DC component, the coupling capacitor C42 may be omitted.
The choke coil L41 (impedance element) is a coil that limits the current flowing through the conversion circuit 150.
The conversion circuit 150 converts an alternating current (hereinafter referred to as “series circuit current i _S ”) input from the alternating voltage generation circuit 110 via the choke coil L41 into a direct current. The direct current converted by the conversion circuit 150 is a current for turning on the light source LA (hereinafter referred to as “light source current I _LA ”).
The current detection circuit 170 detects the series circuit current i _S.
The voltage detection circuit 180 detects a voltage generated in the conversion circuit 150.
The control circuit 160 controls the lighting device 100 as a whole. The control circuit 160 (frequency control circuit) instructs the AC voltage generation circuit 110 based on the series circuit current i _S detected by the current detection circuit 170, and the light source current I _LA becomes a predetermined current value (hereinafter referred to as “target”). The frequency of the AC voltage generated by the AC voltage generation circuit 110 (hereinafter referred to as “generation frequency f”) is adjusted so as to be “current I ₀ ”). Further, the control circuit 160 determines whether an abnormality such as a failure of the light source LA has occurred based on the voltage detected by the voltage detection circuit 180. If it is determined that an abnormality has occurred, the control circuit 160 instructs the AC voltage generation circuit 110 to stop generating the AC voltage.

FIG. 2 is an electric circuit diagram showing a circuit configuration of the lighting device 100 according to this embodiment.
The AC voltage generation circuit 110 includes a diode bridge DB1, an active filter circuit 120, and a half bridge circuit 130.
The diode bridge DB1 (rectifier circuit) generates a pulsating voltage by full-wave rectifying AC power input from the AC power supply AC.
The active filter circuit 120 (DC voltage generation circuit) boosts the pulsating voltage generated by the diode bridge DB1 to generate a DC voltage. The active filter circuit 120 includes a PFC, a coil L21, a switching element Q22, a rectifying element D23, and a smoothing capacitor C24. The PFC controls the switching element Q22 to repeatedly turn on and off the switching element Q22. While the switching element Q22 is on, the pulsating voltage generated by the diode bridge DB1 is applied to the coil L21, and a current flows through the coil L21. When the switching element Q22 is turned off, the current flowing through the coil L21 charges the smoothing capacitor C24 via the rectifying element D23. As a result, the smoothing capacitor C24 is charged with the boosted voltage. The power factor of the lighting device 100 is improved by adjusting the timing at which the PFC turns on and off the switching element Q22. The cathode terminal of the smoothing capacitor C24 is electrically connected to a ground wiring having a reference potential in the lighting device 100.
The half bridge circuit 130 (inverter circuit) is a circuit in which two switching elements Q31 and Q32 are electrically connected in series, and are electrically connected to both ends of the smoothing capacitor. The two switching elements Q31 and Q32 are turned on or off in accordance with a drive signal from the control circuit. When the two switching elements Q31 and Q32 are alternately turned on and off at the generation frequency f, a rectangular wave voltage having the generation frequency f is generated at the connection point b of the two switching elements Q31 and Q32. The AC voltage generation circuit 110 outputs a rectangular wave voltage generated at the connection point b as an AC voltage. Further, when both the switching elements Q31 and Q32 are kept off, a rectangular wave voltage is not generated at the connection point b, and the AC voltage generation circuit 110 stops generating the AC voltage.

The conversion circuit 150 includes a diode bridge DB2 and a smoothing capacitor C51.
The diode bridge DB2 (rectifier circuit) performs full-wave rectification on the series circuit current i _S to charge the smoothing capacitor C51 and generate a current for lighting the light source LA.
The smoothing capacitor C51 smoothes the alternating current component (ripple) of the current generated by the diode bridge DB2 so that the light source current becomes substantially constant.
The diode bridge DB2 is configured using a high-speed diode or the like having a sufficiently short reverse recovery time with respect to the generation frequency f. Alternatively, a high-speed diode and a general-type diode may be combined to increase the switching speed with a high-speed diode and increase the breakdown voltage with the general-type diode.

The current detection circuit 170 has two rectifier elements D71 and D72 and a current detection resistor R73. In the current detection circuit 170, the two rectifying elements D71 and D72 extract only the component in one direction (the direction from right to left in FIG. 2) from the series circuit current i _S and flow through the current detection resistor R73. A voltage generated at both ends of the current detection resistor R73 (hereinafter referred to as “current detection voltage v _id ”) is output.
The voltage detection circuit 180 has two voltage dividing resistors R81 and R82. The voltage detection circuit 180 divides the voltage generated at the connection point c between the choke coil L41 and the diode bridge DB2 by the two voltage dividing resistors R81 and R82, and the voltage generated at both ends of the voltage dividing resistor R82 (hereinafter referred to as “voltage”). Detection voltage v _vd ”).

The control circuit 160 includes a voltage comparison unit 161, a frequency adjustment unit 162, a signal generation unit 163, a drive circuit 164, and an abnormality determination unit 165.
The voltage comparison unit 161 compares the current detection voltage v _id output from the current detection circuit 170 with a predetermined voltage value (hereinafter referred to as “reference voltage V _ref ”) to determine which is larger.
The frequency adjustment unit 162 determines the generation frequency f of the AC voltage generated by the AC voltage generation circuit 110 based on the determination result of the voltage comparison unit 161. The frequency adjustment unit 162 determines the length of the period when the voltage comparison unit 161 determines that the current detection voltage v _id is greater than the reference voltage V _ref, and the voltage comparison unit 161 determines that the current detection voltage v _id is less than the reference voltage V _ref. If the calculated ratio is equal to a predetermined value (hereinafter referred to as “target ratio”), it is determined that the light source current I _LA is equal to the target current I ₀ and is generated. The frequency f is maintained as it is. When the calculated ratio is larger than the target ratio, the frequency adjustment unit 162 determines that the light source current I _LA is larger than the target current I ₀ and increases the generation frequency f. When the calculated ratio is smaller than the target ratio, the frequency adjustment unit 162 determines that the light source current I _LA is smaller than the target current I ₀ and decreases the generation frequency f.
The signal generation unit 163 generates a control signal having the generation frequency f determined by the frequency adjustment unit 162.
Based on the control signal generated by the signal generation unit 163, the drive circuit 164 generates a drive signal for alternately turning on and off the two switching elements Q31 and Q32 at the generation frequency f.
As a result, the light source current I _LA becomes substantially equal to the target current I ₀ .

The abnormality determination unit 165 determines whether an abnormality has occurred based on the voltage detection voltage v _vd output from the voltage detection circuit 180.
For example, if any of the LEDs connected in series in the light source LA has an open failure, the light source current I _LA becomes 0, and the smoothing capacitor C51 is only charged and is not discharged, so the voltage across the light source LA increases. . The voltage generated at the connection point c takes a value between a voltage obtained by adding the voltage across the light source LA and a voltage obtained by subtracting the voltage across the light source LA from the voltage charged in the coupling capacitor C42. The maximum value of the voltage generated at the point c becomes high and the minimum value becomes low. When the voltage detection voltage v _vd is equal to or higher than the predetermined voltage, or when the voltage detection voltage v _vd is equal to or lower than the predetermined voltage, the abnormality determination unit 165 (open circuit protection circuit) It is determined that the voltage across LA has become abnormally high.
In addition, if any of the LEDs connected in series in the light source LA has a short circuit failure, the light source current I _LA is kept substantially equal to the target current I ₀ , so there is no problem even if the light source LA is lit as it is. The voltage at both ends of the light source LA is lowered by the amount of the short-circuited LED. Therefore, the maximum value of the voltage generated at the connection point c is low and the minimum value is high. When the maximum value of the voltage detection voltage v _vd is equal to or lower than the predetermined voltage, or when the minimum value of the voltage detection voltage v _vd is equal to or higher than the predetermined voltage, the abnormality determination unit 165 It is determined that the voltage across the light source LA has become abnormally low.

When the abnormality determination unit 165 determines that an abnormality has occurred, the signal generation unit 163 does not generate a control signal. Thereby, since the drive circuit 164 does not generate a drive signal, the two switching elements Q31 and Q32 continue to be in an OFF state, and the AC voltage generation circuit 110 stops generating the AC voltage.
Thereby, when abnormality occurs in the light source LA, the lighting device 100 is safely stopped.

FIG. 3 is a diagram showing an example of the voltage / current of each part of the lighting device 100 according to this embodiment.
The capacitances of the smoothing capacitor C24, the coupling capacitor C42, and the smoothing capacitor C51 are sufficiently large and are charged to an equilibrium state. During the period shown in FIG. 3, the voltage charged in these capacitors is It shall be constant. Hereinafter, the voltage across the smoothing capacitor C51, is referred to as a DC voltage _{V 0,} the voltage across the coupling capacitor C42, is referred to as a coupling voltage _{V 1,} the voltage across the smoothing capacitor C51, is referred to as a source voltage _{V LA.} The coupling voltage V ₁ is approximately half of the DC voltage V ₀ .

It is assumed that the abnormality determination unit 165 determines that no abnormality has occurred, the drive circuit 164 generates a drive signal having the generation frequency f, and the two switching elements Q31 and Q32 are alternately turned on and off. For example, at time _{t 1,} the switching element Q31 is turned on, at time _{t 2, the} switching element Q31 is turned off. During this time, the switching element Q32 remains off. Between the time t ₂ and time t ₃ is the dead-off time for preventing a short circuit. At time _{t 3,} in turn, the switching element Q32 is turned on at time _{t 4,} the switching element Q32 is turned off. Between the time _{t 4} and time _{t 5} is, again, is a dead-off time. At time _{t 5,} the switching element Q31 is turned on again, thereafter repeated. The period in which the two switching elements Q31 and Q32 are repeatedly turned on and off is the reciprocal of the generation frequency f.

During a period in which the switching element Q31 is on (hereinafter referred to as “high potential period”), a voltage generated at the connection point b (hereinafter referred to as “voltage v _b ”) is substantially equal to the DC voltage V ₀ . Since a current flowing from left to right in FIG. 2 flows through the choke coil L41, the voltage generated at the connection point c (hereinafter referred to as “voltage v _c ”) is obtained by adding the light source voltage V _LA to the coupling voltage V ₁ . Voltage. Voltage across the choke coil L41 (hereinafter referred to as "coil voltage v _L".), The voltage v since the difference between the _b and the voltage v _c, a substantially constant voltage is applied to the choke coil L41, the series circuit current i _S increases with a substantially constant slope. Hereinafter, the maximum value of the series circuit current i _S is referred to as the maximum current I ₁ .

In the dead-off time after the end of the high potential period, the series circuit current i _S quickly becomes zero. In the process, the coil voltage v _L temporarily increases, but after the series circuit current i _S becomes 0, the coil voltage v _L also becomes 0, so the voltage v _b is almost half of the DC voltage V ₀ . become.

In the period the switching element Q32 is turned on (hereinafter referred to as "low potential period".), Voltage v _b is substantially zero. The choke coil L41, since current flows toward the left from the right in FIG. 2, the voltage v _c, a voltage obtained by subtracting the source voltage V _LA from coupling voltage V _1. Coil voltage v _L, the high potential period and the sign is substantially the same voltage of the opposite. The series circuit current i _S flows in the opposite direction to the high potential period, and increases with a substantially constant slope substantially the same as that of the high potential period. If the length of the high potential period is equal to the length of the low potential period, the maximum value in the reverse direction of the series circuit current i _S is approximately equal to the maximum current I ₁ in the high potential period.

In the dead-off time after the end of the low potential period, the series circuit current i _S quickly becomes zero. In the process, the coil voltage v _L temporarily increases, but after the series circuit current i _S becomes 0, the coil voltage v _L also becomes 0, so the voltage v _b is almost half of the DC voltage V ₀ . become.

The series circuit current i _S is full-wave rectified by the diode bridge DB2, and the full-wave rectified current (hereinafter referred to as “rectified current i _r ”) is a current that charges the smoothing capacitor C51 (hereinafter “capacitor current i _C ”). And a light source current I _LA for turning on the light source LA. Since the light source voltage V _LA is substantially constant, the light source current I _LA is also substantially constant according to the voltage-current characteristics of the light source _LA . Since the smoothing capacitor C51 is in equilibrium, the rectified current i _r is the light source current I and total _{current LA} charging the smoothing capacitor C51 when larger, the light source current I when the rectified current i _r is smaller than the source current I _LA The total amount of current that discharges the smoothing capacitor C51 to make up for _LA is equal. That is, in FIG. 3, the area of the range indicated by the diagonal line rising to the right is equal to the area of the range indicated by the diagonal line rising to the left. Therefore, the light source current I _LA is proportional to the maximum current I _1, if a negligible dead-off time, which is approximately half of the maximum current I _1.

The current detection voltage v _id is a voltage proportional to a portion of the series circuit current i _S that is greater than or equal to zero.

If the maximum current I ₁ is large, the period in which the current detection voltage v _id is greater than the reference voltage V _ref becomes long, and the frequency adjustment unit 162 increases the generation frequency f. Thereby, the length of the high potential period and the low potential period is shortened. Since the increase slope of the series circuit current i _S is substantially constant, the maximum current I ₁ is reduced by reducing the length of the high potential period and the low potential period.
Conversely, if the maximum current I ₁ is small, the period during which the current detection voltage v _id is greater than the reference voltage V _ref is shortened, and the frequency adjustment unit 162 decreases the generation frequency f. Thus, the length of the high potential period and the low potential period is long, the maximum current I ₁ is increased.
Therefore, the generation frequency f can be adjusted so that the light source current I _LA is equal to the target current I ₀ .

In the above description, the frequency adjustment unit 162, based on the ratio of the length of the current detection voltage _{v id} and the length of the reference voltage _{V ref} is greater than period, the current detection voltage _{v id} the reference voltage _{V ref} is smaller than the period Te, it is determined whether the light source current I _LA is equal to the target current I _0, it is determined the generation frequency f, configuration checked by other configurations, whether the light source current I _LA is equal to the target current I ₀ It may be.
For example, a maximum voltage detection unit is provided instead of the voltage comparison unit 161, the maximum voltage detection unit detects the maximum value of the current detection voltage _vid , and the frequency adjustment unit 162 detects the current detected by the maximum voltage detection unit. A configuration may be used in which it is determined whether the light source current I _LA is equal to the target current I ₀ based on the maximum value of the voltage v _id and the generation frequency f is determined.

In addition, the configuration of the current detection circuit 170 is not limited to that described above, and may be another configuration.
FIG. 4 is a diagram showing a modification of the current detection circuit 170 in this embodiment.
The current detection circuit 170 includes a current transformer CT4, two rectifier elements D75 and D76, and a current detection resistor R77. The current transformer CT4 is electromagnetically coupled to the series circuit 140 and generates a current proportional to the series circuit current i _S. The two rectifying elements D75 and D76 perform full-wave rectification on the current generated by the current transformer CT4. The current detection resistor R77 converts the current rectified by the two rectifying elements D75 and D76 into a voltage. Current detecting circuit 170, the voltage across the current detection resistor R77, and outputs it as a current detection voltage _{v id.}
Since the current detection circuit 170 having this configuration is electrically insulated from the AC voltage generation circuit 110 and the series circuit 140, it is not necessary to install between the coupling capacitor C42 and the AC voltage generation circuit 110, and the choke coil L41. And the AC voltage generation circuit 110 may be installed at other positions. In addition, the series circuit current i _S may be detected by providing a secondary winding in the choke coil L41 instead of the current transformer CT4.

In the above description, the current detection circuit 170 indirectly detects the light source current I _LA by detecting the series circuit current i _S. However, the current detection circuit 170 directly detects the light source current I _LA. Also good.

Furthermore, the configuration of the conversion circuit 150 is not limited to that described above, and may be other configurations.
FIG. 5 is a diagram showing a modification of the conversion circuit 150 in this embodiment.
The conversion circuit 150 includes a transformer T53 (insulating transformer) in addition to the diode bridge DB2 and the smoothing capacitor C51. The primary winding of the transformer T53 is electrically connected in series with the choke coil L41 and the coupling capacitor C42, and the diode bridge DB2 inputs the excited current to the secondary winding of the transformer T53 and performs full-wave rectification.
By varying the turns ratio of the transformer T53, it is possible to widen the range that can be set for the target current I _0. Further, the primary side and the secondary side can be insulated by the transformer T53.

FIG. 6 is a diagram showing another modification of the conversion circuit 150 and the light source LA in this embodiment.
The conversion circuit 150 includes two rectifying elements D54 and D55. The cathode terminal (cathode) of the rectifying element D54 and the anode terminal (anode) of the rectifying element D55 are electrically connected to the coupling capacitor C42.
The light source LA has two LED circuits in which a plurality of LEDs are connected in series. In one of the LED circuits, the cathode side terminal is electrically connected to the anode terminal of the rectifying element D54, and the anode side terminal is electrically connected to the choke coil L41 via the conversion circuit 150. In the other LED circuit, the anode side terminal is electrically connected to the cathode terminal of the rectifying element D55, and the cathode side terminal is electrically connected to the choke coil L41 via the conversion circuit 150.
The series circuit current i _S is half-wave rectified by the two rectifying elements D54 and D55 and divided into two, and each of the divided currents flows through the LED circuit of the light source LA to light the LED.
Thereby, the two LED circuits of the light source LA are alternately lit at the generation frequency f. Since the lighting time per LED is shortened, the life of the light source LA is lengthened.
Further, since the configuration of the conversion circuit 150 is simplified, the number of parts of the lighting device 100 can be reduced, and the size and weight can be reduced and the manufacturing cost can be reduced.

As yet another modification, a configuration in which the smoothing capacitor C51 is deleted from the configuration of the conversion circuit 150 shown in FIGS. In that case, since the flow through the source LA is not removed high frequency components of the rectified current i _r (ripple) is a light source LA is flashing at twice the frequency of the generated frequency f.

Since the lighting device 100 in this embodiment includes the choke coil L41 that is electrically connected in series with the conversion circuit 150 that converts the series circuit current i _S into the light source current I _LA that turns on the light source LA, the choke coil L41 is connected in series. limits the circuit current i _S, by changing the frequency of the series circuit current i _S, it is possible to control the light source current I _LA.

In the lighting device 100, the control circuit 160 controls the generation frequency f of the AC voltage generated by the AC voltage generation circuit 110 so that the light source current I LA for lighting the light source _LA becomes the target current I ₀ . There is no need to step down and power consumption can be reduced accordingly.

In the lighting device 100, the abnormality determination unit 165 determines that the light source voltage V _LA is equal to or higher than a predetermined voltage value, the drive circuit 164 stops generating the drive signal, and the AC voltage generation circuit 110 receives the AC voltage. Since the generation is stopped, the lighting device 100 can be safely stopped when the light source LA has an open failure.

In the lighting device 100, the abnormality determination unit 165 determines that the light source voltage V _LA is equal to or lower than a predetermined voltage value, the drive circuit 164 stops generating the drive signal, and the AC voltage generation circuit 110 receives the AC voltage. Since the generation is stopped, the lighting device 100 can be safely stopped when the light source LA is short-circuited.

  Since the lighting fixture 800 has the lighting device 100 as described above and the light source LA that is turned on by the direct current generated by the lighting device 100, the light source LA can be turned on with a predetermined brightness.

The lighting fixture 800 may have a configuration including a light source such as a fluorescent lamp in addition to a light source LA such as an LED that is lit by a direct current. Thereby, both the advantages of fluorescent lamps and the advantages of LEDs can be utilized.
In that case, a lighting device that lights a fluorescent lamp or the like can share the AC voltage generation circuit 110 of the lighting device 100. Since the AC voltage generation circuit in the lighting device that lights a fluorescent lamp or the like is different from the AC voltage generation circuit 110 in controlling the frequency of the generated AC voltage, only a half-bridge circuit is provided. The dedicated half-bridge circuit receives the DC voltage generated by the active filter circuit 120 and generates a high-frequency AC voltage.
Thereby, the number of parts of the lighting fixture 800 can be reduced, and a reduction in size and weight, a reduction in manufacturing cost, and energy saving can be achieved.

  Note that the AC voltage generation circuit 110 may have a configuration including a step-down chopper circuit instead of the active filter circuit 120, or may have a configuration including only a smoothing capacitor for smoothing.

Embodiment 2. FIG.
The second embodiment will be described with reference to FIG.
In addition, about the part which is common in Embodiment 1, the same code | symbol is attached | subjected and description is abbreviate | omitted.

FIG. 7 is an overall configuration diagram showing the configuration of the lighting fixture 800 in this embodiment.
The lighting device 100 includes a capacitor C43 instead of the choke coil L41 in the first embodiment.
Further, the conversion circuit 150 does not have the smoothing capacitor C51 and is configured only from the diode bridge DB2.

  Capacitor C43 (impedance element) limits the current flowing through conversion circuit 150. In the first embodiment, since the choke coil L41 limits the current flowing through the conversion circuit 150, the higher the generation frequency f of the AC voltage generated by the AC voltage generation circuit 110, the smaller the current flowing through the conversion circuit 150. The lower the generation frequency f, the larger the current flowing through the conversion circuit 150. In contrast, in this embodiment, since the capacitor C43 limits the current flowing through the conversion circuit 150, the lower the generation frequency f, the smaller the current flowing through the conversion circuit 150, and the higher the generation frequency f, the conversion circuit 150. The current flowing through becomes larger.

When the frequency adjustment unit 162 determines that the light source current I _LA is larger than the target current I ₀ , the frequency adjustment unit 162 decreases the generation frequency f. When determining that the light source current I _LA is smaller than the target current I ₀ , the frequency adjustment unit 162 increases the generation frequency f.

Thus, the element connected in series with the conversion circuit 150 is not limited to an inductive reactance element such as the choke coil L41 but may be a capacitive reactance element such as the capacitor C43. In either case, since the reactance element limits the series circuit current i _S, by changing the frequency of the series circuit current i _S, it is possible to control the light source current I _LA.

  Furthermore, the element connected in series with the conversion circuit 150 is not limited to a reactance element such as a coil or a capacitor, but may be an impedance element having a resistance component as long as the impedance changes depending on the frequency. However, when the impedance element has a resistance component, power loss occurs in the impedance element, so that the resistance component of the impedance element is preferably small, and is preferably a pure reactance element such as a coil or a capacitor.

Embodiment 3 FIG.
A third embodiment will be described with reference to FIGS.
In addition, about the part which is common in Embodiment 1, the same code | symbol is attached | subjected and description is abbreviate | omitted.

FIG. 8 is an overall configuration diagram showing the configuration of the lighting fixture 800 in this embodiment.
The lighting fixture 800 includes a plurality of light sources LA1 and LA2. Both of the light sources LA1 and LA2 are light sources such as LEDs that are lit by a direct current. Target current _{I 0} of the light source LA1 (hereinafter referred to as _{"I 01".)} And the target current _{I 0} of the light source LA2 (hereinafter referred to as _{"I 02".)} And may be the same, or different Also good.

The lighting device 100 includes a plurality of choke coils L41a and L41b and a plurality of conversion circuits 150a and 150b corresponding to the plurality of light sources LA1 and LA2.
A circuit in which the choke coil L41a and the conversion circuit 150a are electrically connected in series and a circuit in which the choke coil L41b and the conversion circuit 150b are electrically connected in series are electrically connected in parallel and electrically connected in series with the coupling capacitor C42. ing.
The conversion circuit 150a generates a direct current that lights the light source LA1. The conversion circuit 150b generates a direct current that lights the light source LA2.

The inductance of the choke coil L41a (hereinafter referred to as “L ₁ ”) and the inductance of the choke coil L41b (hereinafter referred to as “L ₂ ”) are set to values that satisfy the following expression.

The slope of the series circuit current i _S during the high potential period and the low potential period is inversely proportional to the inductance of the choke coils L41a and L41b. Thus, for example, if multiple inductance _{L 2} is _{L 1} of the choke coil L41a of the choke coil L41b, the series circuit current flowing through the choke coil L41b _{i S} (hereinafter referred to as _{"i S2".)} Is, in series through the choke coil L41a It becomes half of the circuit current i _S (hereinafter referred to as “i _S1 ”). As a result, the light source current I _LA (hereinafter referred to as “I _LA2 ”) flowing through the light source LA2 becomes half of the light source current I _LA (hereinafter referred to as “I _LA1 ”) flowing through the light source LA1.

The current detection circuit 170 detects a current obtained by adding the series circuit current i _S1 and the series circuit current i _S2 . The control circuit 160 controls the generation frequency f based on the current detected by the current detection circuit 170. The inductance _{L 1} of the choke coil L41a, by the ratio of the inductance _{L 2} of the choke coil L42b, since definite ratio between the series circuit current _{i S1} and a series circuit current _{i S2,} the control based on the current which is the sum of both The light source currents I _LA1 and I _LA2 can be controlled to be equal to the target currents I ₀₁ and I ₀₂ , respectively.

  The voltage detection circuit 180 includes two rectifier elements D83 and D84 in addition to the voltage dividing resistors R81 and R82. The rectifier element D83 has an anode terminal electrically connected to a connection point between the choke coil L41a and the conversion circuit 150a, and a cathode terminal electrically connected to the voltage dividing resistor R81. The rectifier element D84 has an anode terminal electrically connected to a connection point between the choke coil L41b and the conversion circuit 150b, and a cathode terminal electrically connected to the voltage dividing resistor R81. Since the two rectifying elements D83 and D84 are OR-connected, the connection between the choke coil L41a and the conversion circuit 150a and the connection between the choke coil L41b and the conversion circuit 150b are connected to the two voltage dividing resistors R81 and R82. The higher voltage of the points is applied. Thereby, the control circuit 160 can detect an abnormality when the voltage across either of the light sources LA1 and LA2 becomes abnormally high.

The configuration for making the ratio of the series circuit current i _S1 and the series circuit current i _S2 constant is not limited to the configuration described above, and may be another configuration.
FIG. 9 is an overall configuration diagram showing a modified example of the lighting fixture 800 in this embodiment.
The lighting device 100 uses a balancer B43 as the choke coils L41a and L41b. In this configuration, the ratio between the series circuit current i _S1 and the series circuit current i _S2 can be set by the turn ratio of the balancer B43.

As described above, when a plurality of light sources LA1 and LA2 having different voltage-current characteristics are lit, the AC voltage generation circuit 110 is configured to have a constant ratio between the series circuit current i _S1 and the series circuit current i _S2. The number of parts of the lighting device 100 can be reduced, the size and weight can be reduced, and the energy can be saved.

Embodiment 4 FIG.
The fourth embodiment will be described with reference to FIG.
In addition, about the part which is common in Embodiment 1, the same code | symbol is attached | subjected and description is abbreviate | omitted.

FIG. 10 is an overall configuration diagram showing the configuration of the lighting fixture 800 in this embodiment.
The lighting fixture 800 has a dimming function that can adjust the brightness of the light source LA based on the dimming signal generated by the dimming signal generation device 200.
The dimming signal generation device 200 is a remote controller, for example, and generates a dimming signal representing the dimming degree of the light source LA desired by the user. The dimming signal represents the dimming degree of the light source LA by, for example, the duty ratio of the PWM signal.

The lighting device 100 includes a dimming signal input circuit 190 in addition to the configuration described in the first embodiment.
The dimming signal input circuit 190 inputs the dimming signal generated by the dimming signal generation device 200.
The control circuit 160 sets the target current I ₀ based on the dimming degree represented by the dimming signal input by the dimming signal input circuit 190, and generates the light source current I _{LA to} be equal to the set target current I _0. Adjust the frequency f.
For example, a method described in the first embodiment, i.e., the frequency adjustment unit 162, the length of the current sense voltage _{v id} reference voltage _{V ref} is greater than the period, the current detection voltage _{v id} of the reference voltage _{V ref} is smaller than the period In the case of the method of determining the generation frequency f by comparing the ratio with the length with the target ratio, the frequency adjusting unit 162 sets the target ratio to be large when the dimming degree is used to light the light source LA brightly. When the target current I ₀ is increased and the light control level is such that the light source LA is lit darkly, the target current I ₀ is decreased by setting the target ratio small. The relationship with the target ratio may be calculated in advance from the dimming degree and written in a storage device such as a ROM, and the frequency adjustment unit 162 may be configured to calculate the target ratio from the dimming degree by referring to the relationship. The frequency adjustment unit 162 may be configured to calculate the target ratio from the dimming degree using a calculation formula for calculating the target ratio from the dimming degree.
Alternatively, the dimming signal input circuit 190 based on the dimming degree represents the dimming signal input may be configured to vary the reference voltage V _ref to the voltage comparing unit 161 compares the current sense voltage v _id. The voltage comparison unit 161 sets the reference voltage V _ref to be high when the light source LA is lit brightly, and sets the reference voltage V _ref to be low when the light source LA is dimly lit. When the dimming signal input by the dimming signal input circuit 190 is a PWM signal, the dimming signal may be integrated with the integrating circuit that generates the reference voltage _Vref .

  As a result, the brightness of the light source LA can be changed within a predetermined range instead of turning on the light source LA with a constant brightness.

100 lighting device, 110 AC voltage generation circuit, 120 active filter circuit, 130 half bridge circuit, 150 conversion circuit, 160 control circuit, 161 voltage comparison unit, 162 frequency adjustment unit, 163 signal generation unit, 164 drive circuit, 165 abnormality determination Unit, 170 current detection circuit, 180 voltage detection circuit, 190 dimming signal input circuit, 200 dimming signal generation device, 800 lighting fixture, AC AC power supply, B43 balancer, C24, C51 smoothing capacitor, C42 coupling capacitor, C43 capacitor, CT4 current transformer, D23, D54, D55, D71, D72, D75, D76, D83, D84 rectifier, DB1, DB2 diode bridge, f generation frequency, I ₀ target current, I ₁ maximum current, i _C capacitor current, I _LA source current, _{i r} rectified current i _S series circuit current, L21 coils, L41 choke coil, LA source, Q22, Q31, Q32 switching element, R73, R77 a current detection resistor, R81, R82 voltage divider resistor, T53 transformer, _{V 0} the DC voltage, _{V 1} binding voltage , _v b, _{v c} voltage, _{v L} coil _{voltage, V LA} source _{voltage, v id} current detection _{voltage, V ref} reference _{voltage, v vd} voltage detection voltage.

Claims (6)

A conversion circuit that converts alternating current into direct current that turns on the light source;
A series circuit having an impedance element having a frequency characteristic electrically connected in series with the conversion circuit;
A lighting device comprising: an AC voltage generation circuit that generates an AC voltage applied to the series circuit.   The lighting device according to claim 1, wherein the impedance element is a choke coil or a capacitor. The lighting device further includes:
The frequency control circuit for controlling the frequency of the AC voltage generated by the AC voltage generation circuit so that the DC current for lighting the light source has a predetermined current value. Lighting device. The lighting device further includes:
The open fault protection circuit which stops the production | generation of the alternating voltage by the said alternating voltage generation circuit when the both-ends voltage of the said light source is more than predetermined voltage value, The any one of Claim 1 thru | or 3 characterized by the above-mentioned. The lighting device described in 1. The lighting device further includes:
5. The circuit according to claim 1, further comprising a short-circuit fault protection circuit that stops generation of an AC voltage by the AC voltage generation circuit when a voltage across the light source is equal to or lower than a predetermined voltage value. The lighting device described in 1.   6. A lighting apparatus comprising: the lighting device according to claim 1; and a light source that is lit by a direct current generated by the lighting device.

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