Power Supply Circuit and Illumination Apparatus

According to one embodiment, provided is a power supply circuit including a power conversion unit, a controller, and an integrated circuit. The power conversion unit converts an AC voltage into a different voltage. The integrated circuit includes a current regulator that can switch between a first state in which a part of a current flowing through the power supply path flows to an input terminal and a second state in which a current flowing to the input terminal is lower than that of the first state, a controller power supply that converts a voltage into a driving voltage and supplies the driving voltage to the controller, a connection terminal for connecting an auxiliary power supply used for generating the driving voltage, and a protection circuit that blocks or decreases, when an auxiliary power supply voltage of the auxiliary power supply decreases, a current flowing to the input terminal.

DETAILED DESCRIPTION

According to one embodiment, there is provided a power supply circuit including a power conversion unit, a controller, and an integrated circuit. The power conversion unit converts an AC voltage, supplied through a power supply path, into a different voltage and supplies the converted voltage to a load. The controller controls the power conversion unit to perform the voltage conversion. The integrated circuit includes an input terminal that is electrically connected to the power supply path, a current regulator that can switch between a first state in which a part of a current flowing through the power supply path flows to the input terminal and a second state in which a current flowing to the input terminal is lower than that of the first state, a controller power supply that converts a voltage, supplied through the current regulator, into a driving voltage corresponding to the controller and supplies the driving voltage to the controller, a connection terminal for connecting an auxiliary power supply which is used for generating the driving voltage, and a protection circuit that blocks or decreases, when an auxiliary power supply voltage of the auxiliary power supply decreases, a current flowing to the input terminal.

According to another embodiment, there is provided an illumination apparatus including an illumination load and a power supply circuit. The power supply circuit includes a power conversion unit, a controller, and an integrated circuit. The power conversion unit converts an AC voltage, supplied through a power supply path, into a different voltage and supplies the converted voltage to a load. The controller controls the power conversion unit to perform the voltage conversion. The integrated circuit includes an input terminal that is electrically connected to the power supply path, a current regulator that can switch between a first state in which a part of a current flowing through the power supply path flows to the input terminal and a second state in which a current flowing to the input terminal is lower than that of the first state, a controller power supply that converts a voltage, supplied through the current regulator, into a driving voltage corresponding to the controller and supplies the driving voltage to the controller, a connection terminal for connecting an auxiliary power supply which is used for generating the driving voltage, and a protection circuit that blocks or decreases, when an auxiliary power supply voltage of the auxiliary power supply decreases, a current flowing to the input terminal.

Hereinafter, each embodiment will be described with reference to the drawings.

The drawings are schematic or conceptual, and a relationship between the thickness and the width of each portion, size ratios between portions, and the like are not necessarily limited to being the same as those of actual ones. In addition, even when the same portion is illustrated in the drawings, the dimension, ratio, and the like thereof may vary depending on the drawings.

In this specification and the respective drawings, the same elements are represented by the same reference numerals, and the description thereof will not be repeated.

FIG. 1is a block diagram schematically illustrating an illumination apparatus according to an embodiment.

As illustrated inFIG. 1, an illumination apparatus10includes an illumination load12(load) and a power supply circuit14. The illumination load12includes an illumination light source16such as a light-emitting diode (LED). The illumination light source16may be an organic light-emitting diode (OLED) or the like. As the illumination light source16, for example, a light-emitting element having forward voltage drop is used. The illumination load12turns on the illumination light source16by the application of an output voltage and the supply of an output current from the power supply circuit14. Values of the output voltage and the output current are determined according to the illumination light source16.

The power supply circuit14is connected to an AC power supply2and a dimmer3. In this specification, “connection” refers to electrical connection and includes cases where elements are not physically connected to each other and cases where elements are connected to each other through another element.

The AC power supply2is, for example, a commercial power supply. The dimmer3generates an AC voltage VCT with a controlled conduction angle from an AC power supply voltage VIN of the AC power supply2. The power supply circuit14converts the AC voltage VCT, supplied from the dimmer3, into a DC voltage and outputs the DC voltage to the illumination load12to turn on the illumination light source16. In addition, the power supply circuit14dims the illumination light source16in synchronization with the AC voltage VCT with a controlled conduction angle. The dimmer3is provided as necessary and may not be provided. When the dimmer3is not provided, the power supply voltage VIN of the AC power supply2is supplied to the power supply circuit14.

Examples of a method of controlling a conduction angle using the dimmer3include phase control (leading edge control) of controlling a conduction phase in a period from a zero-cross point of an AC voltage to a point at which an absolute value of the AC voltage is maximum; and reverse phase control (trailing edge control) of controlling a blocking phase in a period from a point at which an absolute value of an AC voltage is maximum to a zero-cross point of the AC voltage.

The phase control dimmer3has the following characteristics, for example. The circuit configuration is simple, and a relatively high electrical load can be handled. However, when a triac is used, a low-load operation is difficult to perform. Therefore, when so-called power supply dipping in which a power supply voltage is temporarily decreased occurs, the operation is likely to be unstable. In addition, when a capacitive load is connected, an inrush current is generated. Therefore, compatibility with a capacitive load is low.

On the other hand, the reverse phase control dimmer3has the following characteristics, for example. The operation can be performed at a low load; even when a capacitive load is connected, an inrush current is not generated; and even when power supply dipping occurs, the operation is stable. However, since the circuit configuration is complicated and the temperature is likely to rise, the reverse phase control dimmer3is not suitable to a high load. In addition, when an inductive load is connected, a surge is generated.

In this embodiment, a configuration in which the dimmer3is connected in series between terminals4and6of a pair of power supply lines through which the power supply voltage VIN is supplied is described as an example. However, other configurations may also be adopted.

The power supply circuit14includes a power conversion unit21, a controller22, an integrated circuit23, and an overcurrent protection unit24.

The power conversion unit21converts the AC voltage VCT with a controlled conduction angle, supplied through a first power supply path26a, into a different voltage and supplies the converted voltage to the illumination load12. The power conversion unit21includes an AC-DC converter21aand a DC-DC converter21b. The AC-DC converter21aconverts the AC voltage VCT, supplied through the first power supply path26a, into a first DC voltage VDC1.

The DC-DC converter21bis connected to the AC-DC converter21athrough a second power supply path26b. The DC-DC converter21bconverts the first DC current VDC1, supplied from the second power supply path26b, into a second DC voltage VDC2 having a predetermined voltage value corresponding to the illumination load12; and supplies the second DC voltage VDC2 to the illumination load12. The absolute value of the second DC voltage VDC2 is different from the absolute value of the first DC voltage VDC1. For example, the absolute value of the second DC voltage VDC2 is lower than the absolute value of the first DC voltage VDC1. In this example, the DC-DC converter21bis a step-down converter. By the supply of the second DC voltage VDC2, the illumination light source16of the illumination load12is turned on.

The controller22detects a conduction angle of the AC voltage VCT and controls the power conversion unit21to perform the voltage conversion according to the detected conduction angle. For example, the controller22controls the DC-DC converter21bto perform the conversion from the first DC voltage VDC1 to the second DC voltage VDC2. In this example, the controller22controls the operation of the DC-DC converter21bthrough the overcurrent protection unit24. For example, the controller22generates a dimming signal DMS corresponding to the detected conduction angle and inputs the dimming signal DMS to the overcurrent protection unit24. In this way, the controller22controls the overcurrent protection unit24according to the detected conduction angle. As a result, the controller22dims the illumination light source16in synchronization with the conduction angle control of the dimmer3. As the controller22, for example, a microprocessor may be used.

The overcurrent protection unit24is connected to an output terminal8of the power supply circuit14on the low potential side. That is, the overcurrent protection unit24is connected to an end of the illumination load12on the low potential side. The overcurrent protection unit24detects a current flowing to the illumination load12(illumination light source16). The overcurrent protection unit24performs feedback control of the DC-DC converter21bbased on the dimming signal DMS input from the controller22and the detected current. For example, when an overcurrent flows to the illumination light source16, the overcurrent protection unit24performs the feedback control of the DC-DC converter21bto decrease the current. As a result, the overcurrent protection unit24inhibits an overcurrent from flowing to the illumination light source16.

The integrated circuit23is a component composed of a chip. On the integrated circuit23, for example, an input terminal40, a first reference potential terminal41, a current regulator42, a control terminal43, a controller power supply44, an output terminal45, a second reference potential terminal46, a connection terminal47, and a protection circuit48are provided.

The input terminal40is electrically connected to the first power supply path26aand inputs a voltage corresponding to the AC voltage VCT. The first reference potential terminal41is electrically connected to the first power supply path26a. The first reference potential terminal41returns a current flowing to the input terminal40to the first power supply path26a. For example, the first reference potential terminal41is connected to a ground of the AC-DC converter21a. For example, the first reference potential terminal41is set to substantially the same potential as that of the ground of the AC-DC converter21a.

The current regulator42is connected to the input terminal40and regulates a current flowing to the input terminal40. The current regulator42switches between a first state in which a part of a current flowing through the first power supply path26aflows to the input terminal40and a second state in which a current flowing to the input terminal40is lower than that of the first state. As a result, the current regulator42regulates, for example, a current flowing through the first power supply path26a. In the first state, the maximum value of a current flowing to the input terminal40is, for example, higher than or equal to a holding current of a triac which is used for the dimmer3. In the second state, for example, a current does not substantially flow to the input terminal40. For example, the first state is the conduction state, and the second state is the non-conduction state. In the second state, a small current which has no effect on the operation may flow to the input terminal40.

The control terminal43is connected to the current regulator42. In addition, the control terminal43is connected to the controller22. The controller22generates a control signal CGS according to the detected conduction angle and inputs the control signal CGS to the current regulator42through the control terminal43. As a result, the controller22controls the switching of the current regulator42between the first state and the second state.

The controller power supply44is connected to the current regulator42. The controller power supply44converts a voltage, input through the current regulator42, into a DC driving voltage VDD corresponding to the controller22. The output terminal45is connected to the controller power supply44and the controller22and outputs the driving voltage VDD to the controller22. For example, the second reference potential terminal46is connected to a ground of the controller22. For example, the second reference potential terminal46is set to substantially the same potential as that of the ground of the controller22.

The connection terminal47is the terminal for connecting a backup capacitor50(auxiliary power supply) which is used for generating the driving voltage VDD. The protection circuit48detects a decrease in the impedance of the backup capacitor50. That is, the protection circuit48detects the short-circuit of the backup capacitor50. When the impedance of the backup capacitor50is lower than or equal to a predetermined value, the protection circuit48decreases or blocks a current flowing to the input terminal40. In other words, when a voltage (auxiliary power supply voltage) of the backup capacitor50is decreased, the protection circuit48blocks or decreases a current flowing to the input terminal40.

The AC-DC converter21aincludes a rectifier circuit30, a smoothing capacitor32, an inductor34, a filter capacitor36, and rectifying devices37and38.

The rectifier circuit30is, for example, a diode bridge. Input terminals30aand30bof the rectifier circuit30are connected to a pair of input terminals4and5. The AC voltage VCT subjected to phase control or reverse phase control by the dimmer3is input to the input terminals30aand30bof the rectifier circuit30. For example, the rectifier circuit30performs full-wave rectification on the AC voltage VCT and generates a ripple voltage after the full-wave rectification between a high potential terminal30cand a low potential terminal30d.

The smoothing capacitor32is connected between the high potential terminal30cand the low potential terminal30dof the rectifier circuit30. The smoothing capacitor32smoothes a ripple voltage which is rectified by the rectifier circuit30. As a result, the first DC current VDC1 appears on both ends of the smoothing capacitor32.

The inductor34is connected to the input terminal4in series. For example, the inductor34is connected to the first power supply path26ain series. The filter capacitor36is connected between the input terminals4and5. For example, the filter capacitor36is connected to the first power supply path26ain parallel. The inductor34and the filter capacitor36remove noise which is included in, for example, the AC voltage VCT.

The rectifying devices37and38are, for example, diodes. An anode of the rectifying device37is connected to the input terminal30aof the rectifier circuit30. An anode of the rectifying device38is connected to the input terminal30bof the rectifier circuit30.

The DC-DC converter21bis connected to both ends of the smoothing capacitor32. As a result, the first DC voltage VDC1 is input to the DC-DC converter21b. The DC-DC converter21bconverts the first DC voltage VDC1 into the second DC voltage VDC2 having a different absolute value and outputs the second DC voltage VDC2 to output terminals7and8of the power supply circuit14. The illumination load12is connected to the output terminals7and8. The illumination load12turns on the illumination light source16through the second DC voltage VDC2 supplied from the power supply circuit14.

For example, the current regulator42includes switching devices60and61, resistors62and63, a zener diode64, and a switch65.

As the switching device60, for example, FET or GaN-HEMT may be used. In the following description, the switching device60is assumed as FET. In addition, in this example, the switching device60is normally-off type. The switching device60may also be normally-on type.

A drain of the switching device60is connected to the input terminal40. The input terminal40is connected to a cathode of the rectifying device37and a cathode of the rectifying device38. The drain of the switching device60is connected to the cathode of the rectifying device37and the cathode of the rectifying device38through the input terminal40. That is, the drain of the switching device60is connected to the first power supply path26athrough the input terminal40and the respective rectifying devices37and38.

Along with the application of the AC voltage VCT, a current having one polarity flows to the drain of the switching device60through the rectifying device37. Along with the application of the AC voltage VCT, a current having the other polarity flows to the drain of the switching device60through the rectifying device38. As a result, a ripple voltage after the full-wave rectification of the AC voltage VCT is applied to the drain of the switching device60.

A gate of the switching device60is connected to an end of the resistor62and a cathode of the zener diode64. The other end of the resistor62is connected to the cathode of the rectifying device37and the cathode of the rectifying device38. An anode of the zener diode64is connected to the second reference potential terminal46.

A ripple voltage is applied to the cathode of the zener diode64through the resistor62and the respective rectifying devices37and38. As a result, a substantially constant voltage corresponding to a breakdown voltage of the zener diode64is applied to the gate of the switching device60. Accordingly, a substantially constant current flows between the drain and a source of the switching device60. In this way, the switching device60functions as a constant current device. For example, the switching device60regulates a current flowing to the input terminal40.

In this example, the switching device61is an npn transistor. The switching device61is normally-off type. For example, the switching device61may be FET or GaN-HEMT. The switching device61may also be normally-on type.

A collector of the switching device61is connected to an end of the switch65. The other end of the switch65is connected to the gate of the switching device60. That is, the collector of the switching device61is connected to the gate of the switching device60through the switch65.

The switch65is normally-on type. As the switch65, for example, a bipolar transistor or FET may be used.

An emitter of the switching device61is connected to the second reference potential terminal46. A base of the switching device61is connected to an end of the resistor63. The other end of the resistor63is connected to the control terminal43. That is, the base of the switching device61is connected to the controller22through the resistor63and the control terminal43.

The controller22inputs the control signal CGS to the base of the switching device61. For example, by switching the control signal CGS, input from the controller22, from Lo to Hi, the switching device61is switched from the off state to the on state.

When the switching device61is switched on after switching on the switch65, the gate of the switching device60is set to a potential of the ground of the controller22. As a result, the switching device60is switched off. That is, by switching off the switching device61, the current regulator42is switched to the second state; and by switching off the switching device61, the current regulator42is switched to the first state.

In addition, a path switching unit66is provided on the current regulator42. On the path switching unit66, a first resistor R1, a second resistor R2, a third resistor R3, switches SW1and SW2, an npn transistor67, and a resistor68are provided.

An end of the first resistor R1, an end of the second resistor R2, and an end of the third resistor R3are connected to the source of the switching device60, respectively. The other end of the second resistor R2is connected to an end of the switch SW1. The other end of the switch SW1is connected to the other end of the first resistor R1. The other end of the third resistor R3is connected to an end of the switch SW2. The other end of the switch SW2is connected to the other end of the first resistor R1. That is, the first resistor R1, the second resistor R2, and the third resistor R3are connected to each other in parallel. The switch SW1is normally-off type. The switch SW2is normally-on type. As the switches SW1and SW2, for example, a bipolar transistor or FET may be used.

A collector of the npn transistor67is connected to the gate of the switching device60. An emitter of the npn transistor67is connected to an end of the resistor68. A base of the npn transistor67is connected to the source of the switching device60. The other end of the resistor68is connected to the other end of the first resistor R1.

By switching on and off the respective switches SW1and SW2, the path switching unit66forms plural different paths of a current flowing to the input terminal40. For example, the path switching unit66forms a first path in which the respective switches SW1and SW2are switched on; and the respective resistors R1to R3connected to each other in parallel are connected to the source of the switching device60. For example, the path switching unit66forms a second path in which the respective switches SW1and SW2are switched off; and only the first resistor R1is connected to the source of the switching device60. For example, the path switching unit66forms a third path in which the switch SW1is switched off; the switch SW2is switched on; and the first resistor R1and the third resistor R3connected to each other in parallel are connected to the source of the switching device60.

A combined resistance value of the respective resistors R1to R3is lower than a resistance value of the first resistor R1. Accordingly, the maximum value of a current flowing to the input terminal40through the first path is higher than the maximum value of a current flowing to the input terminal40through the second path.

A combined resistance value of the first resistor R1and the third resistor R3is lower than a resistance value of the first resistor R1. In addition, the combined resistance value of the first resistor R1and the third resistor R3is higher than the combined resistance value of the respective resistors R1to R3. Accordingly, the maximum value of a current flowing to the input terminal40in the third path is higher than the maximum value of a current flowing to the input terminal40in the second path and is lower than the maximum value of a current flowing to the input terminal40in the first path.

The maximum value of a current flowing to the input terminal40in the first path is, for example, approximately 300 mA. The maximum value of a current flowing to the input terminal40in the second path is, for example, approximately 0.5 mA. The maximum value of a current flowing to the input terminal40in the third path is, for example, approximately 2 mA. The maximum value of a current flowing to the input terminal40in the first path is, for example, higher than or equal to the holding current of the triac which is used for the dimmer3. The maximum value of a current flowing to the input terminal40in the third path is, for example, lower than the holding current of the triac which is used for the dimmer3.

For example, the controller power supply44includes a rectifying device71, a resistor72, a switch73, and a regulator74.

An anode of the rectifying device71is connected to the other end of the first resistor R1. That is, the anode of the rectifying device71is connected to the source of the switching device60through the path switching unit66. A cathode of the rectifying device71is connected to an end of the resistor72. The other end of the resistor72is connected to an end of the switch73. The other end of the switch73is connected to an input terminal of the regulator74. The switch73is normally-on type. As the switch73, for example, a bipolar transistor or FET may be used.

In addition, the other end of the resistor72is also connected to an end of the backup capacitor50through the connection terminal47. The other end of the backup capacitor50is connected to the low potential terminal30dof the rectifier circuit30. An output terminal of the regulator74is connected to the controller22through the output terminal45of the integrated circuit23.

When the current regulator42is in the first state, a ripple voltage is input from the first power supply path26ato the backup capacitor50through the switching device60, the path switching unit66, the rectifying device71, the resistor72, and the switch73, thereby charging the backup capacitor50. The backup capacitor50may be charged by the smoothing capacitor32. At the same time, a substantially DC voltage, which is obtained by the backup capacitor50smoothing a ripple voltage from the first power supply path26a, is input to the regulator74. The regulator74generates the substantially constant DC driving voltage VDD from the input DC voltage and outputs the driving voltage VDD to the controller22. As a result, the driving voltage VDD is supplied to the controller22.

In this way, the backup capacitor50is used for generating the driving voltage VDD. For example, the backup capacitor50is connected in parallel to an output path through which the driving voltage VDD is output to the controller22; and smoothes the driving voltage VDD.

In addition, when the current regulator42is switched from the first state to the second state, charges accumulated in the backup capacitor50are supplied to the regulator74. As a result, when the current regulator42is in the second state, the controller22may be temporarily driven by the charges accumulated in the backup capacitor50. The capacity of the backup capacitor50is, for example, approximately 10 μF to 20 μF.

In addition, a constant power circuit80is provided on the controller power supply44. For example, the constant power circuit80includes a semiconductor device81, resistors82and83, a shunt regulator84, and a switch85. In this example, the semiconductor device81is an npn transistor. The semiconductor device81is normally-off type. As the semiconductor device81, for example, FET or GaN-HEMT may be used. The semiconductor device81may also be normally-on type.

A collector of the semiconductor device81is connected to the other end of the first resistor R1. A base of the semiconductor device81is connected to an end of the resistor82, an end of the resistor83, and a cathode of the shunt regulator84. An emitter of the semiconductor device81is connected to an end of the switch85. The other end of the switch85is connected to the first reference potential terminal41. The switch85is normally-off type. As the switch85, for example, a bipolar transistor or FET may be used.

The first reference potential terminal41is connected to an end of the resistor51which is provided outside the integrated circuit23. The other end of the resistor51is connected to the low potential terminal30dof the rectifier circuit30. As a result, the first reference potential terminal41is connected to the first power supply path26athrough the resistor51.

The other end of the resistor82is connected to the collector of the semiconductor device81. The other end of the resistor82is connected to a reference terminal of the shunt regulator84.

The reference terminal of the shunt regulator84is connected to a connection terminal86. The connection terminal86is connected to an end of the resistor52and an end of the resistor53. The other end of the resistor52is connected to the respective cathodes of the rectifying devices37and38. The other end of the resistor53is connected to the low potential terminal30dof the rectifier circuit30. In addition, a capacitor54is connected to the resistor53in parallel.

As a result, a voltage, which is obtained by the resistors52and53dividing a ripple voltage from the first power supply path26a, is input to the reference terminal of the shunt regulator84as a reference voltage.

An anode of the shunt regulator84is connected to a connection terminal87. The connection terminal87is connected to the low potential terminal30dof the rectifier circuit30.

In the controller power supply44, a base potential of the semiconductor device81changes depending on the ripple voltage which is input to the reference terminal of the shunt regulator84. That is, the base potential of the semiconductor device81changes depending on the root-mean-square of the AC voltage VCT. For example, when the absolute value of the AC voltage VCT is maximum, the base potential of the semiconductor device81is maximum.

When the base potential of the semiconductor device81increases, a collector current of the semiconductor device81increases, and a source potential of the switching device60increases. That is, the controller power supply44changes the source potential of the switching device60depending on the absolute value of the AC voltage VCT. Since a gate potential of the switching device60is substantially constant, a drain current of the switching device60can be changed by changing the source potential. Specifically, by increasing the source potential, the drain current decreases; and by reducing the source potential, the drain current increases.

Accordingly, when the absolute value of the AC voltage VCT is high, the drain current of the switching device60decreases; and when the absolute value of the AC voltage VCT is low, the drain current of the switching device60increases.

In this way, the constant power circuit80decreases a current flowing to the input terminal40along with an increase in the absolute value of the AC voltage VCT and increases a current flowing to the input terminal40along with a decrease in the absolute value of the AC voltage VCT. As a result, for example, the power consumed in the controller power supply44can be made substantially constant. The power being substantially constant refers to the state in which the power consumed in the controller power supply44is within a predetermined error range.

One input terminal of the protection circuit48is connected between the resistor72and the switch73. As a result, the ripple voltage from the first power supply path26ais input to the protection circuit48. In addition, another input terminal of the protection circuit48is connected to the output terminal of the regulator74. As a result, the driving voltage VDD is input to the protection circuit48.

In the power-on state (in which the power supply voltage VIN starts to be supplied), the protection circuit48detects whether the impedance of the backup capacitor50is lower than or equal to a predetermined value or not. That is, the protection circuit48detects whether the backup capacitor50is short-circuited or not in the power-on state.

On the protection circuit48, for example, a band gap reference voltage circuit and a comparator are provided. The protection circuit48generates a band gap reference in the reference voltage circuit based on the ripple voltage from the first power supply path26a. In addition, by comparing the band gap reference to the driving voltage VDD in the comparator, the protection circuit48detects whether the driving voltage VDD is lower than or equal to a predetermined value.

When the impedance of the backup capacitor50decreases, the smoothing degree of the ripple voltage decreases. Therefore, the driving voltage VDD decreases. Accordingly, when the driving voltage VDD is lower than or equal to the predetermined value, the protection circuit48detects that the impedance of the backup capacitor50decreases. For example, when the driving voltage VDD is lower than or equal to 0.5 V, the protection circuit48detects that the impedance of the backup capacitor50decreases. Hysteresis may be given to the threshold for detection, for example, 1 V during rising and 0.5 V during falling.

In addition, the protection circuit48is connected to the respective switches65,73,85, SW1, and SW2through lines (not illustrated). The switching on and off of the respective switches65,73,85, SW1, and SW2is controlled by the protection circuit48.

As described above, the switches65,85, and SW1are normally-off type. Accordingly, in the power-on state, the switches65,85, and SW1are in the off state. On the other hand, the switches73and SW2are normally-on type. Accordingly, in the power-on state, the switches73and SW2are in the on state. That is, in the power-on state, the path switching unit66is set to the third path.

When it is detected that the impedance of the backup capacitor50does not decrease (that the voltage of the backup capacitor50does not decrease), the protection circuit48switches on the switches65,85, and SW1. As a result, the gate of the switching device60is connected to the collector of the switching device61, the emitter of the semiconductor device81is connected to the first reference potential terminal41, and the path switching unit66is set to the first path. As a result, the integrated circuit23is in a state in which the normal operation can be performed.

On the other hand, when it is detected that the impedance of the backup capacitor50decreases (that the voltage of the backup capacitor50decreases), the protection circuit48switches off the switches73and SW2. As a result, the input of a voltage to the regulator74is blocked, and the path switching unit66is set to the second path. As a result, the protection circuit48decreases a current flowing to the input terminal40. In addition, the protection circuit48stops the output of the driving voltage VDD from the output terminal45.

Resistors55and56and a capacitor57are further connected to the controller22. An end of the resistor55is connected to the respective cathodes of the rectifying devices37and38. The other end of the resistor55is connected to an end of the resistor56. The other end of the resistor56is connected to the low potential terminal30dof the rectifier circuit30. The capacitor57is connected to the resistor56in parallel. A connection point between the resistors55and56is connected to the controller22. As a result, a voltage corresponding to a voltage dividing ratio of the resistors55and56is input to the controller22as a detection voltage for detecting the absolute value of the AC voltage VCT.

For example, based on the detection voltage, the controller22detects whether the conduction angle of the AC voltage VCT is controlled or not; and the type of the conduction angle control (phase control or reverse phase control). When the conduction angle is controlled, the controller22detects the conduction angle. Based on the detection result, the controller22generates the dimming signal DMS and inputs the dimming signal DMS to the overcurrent protection unit24. For example, the controller22inputs a PWM signal corresponding to the detected conduction angle to the overcurrent protection unit24as the dimming signal DMS.

The overcurrent protection unit24includes a differential amplifier circuit90and a semiconductor device91. In this example, the semiconductor device91is an npn transistor. The semiconductor device91is normally-off type. The semiconductor device91may be, for example, a pnp transistor or FET. The semiconductor device91may also be normally-on type.

For example, the differential amplifier circuit90includes an operational amplifier92and a capacitor93. The capacitor93is connected between an output terminal of the operational amplifier92and an inverted input terminal of the operational amplifier92.

A non-inverted input terminal of the operational amplifier92is connected to the output terminal8. That is, the non-inverted input terminal of the operational amplifier92is connected to an end of the illumination load12on the low potential side. As a result, a current flowing to the illumination light source16can be detected. When a light-emitting element such as an LED is used as the illumination light source16, a voltage of the illumination light source16is substantially constant according to forward voltage drop. Accordingly, when a light-emitting element such as an LED is used as the illumination light source16, a current flowing to the illumination light source16can be appropriately detected by the connection to the end of the illumination load12on the low potential side.

The inverted input terminal of the operational amplifier92is connected to an end of a resistor94. The other end of the resistor94is connected to an end of a resistor95, an end of a capacitor96, and an end of a resistor97. The other end of the resistor95and the other end of the capacitor96are connected to the low potential terminal30dof the rectifier circuit30. The other end of the resistor97is connected to the controller22. In this way, the inverted input terminal of the operational amplifier92is connected to the controller22through the resistors94and97. The dimming signal DMS is input from the controller22to the inverted input terminal of the operational amplifier92.

For example, a DC voltage, which is obtained by the capacitor96smoothing the PWM signal, is input to the inverted input terminal of the operational amplifier92as the dimming signal DMS. For example, a DC voltage corresponding to a dimming degree of the dimmer3is input to the inverted input terminal of the operational amplifier92as the dimming signal DMS. A voltage level of the dimming signal DMS is set according to a voltage level of the detection voltage which is input to the non-inverted input terminal. More specifically, for example, a voltage level of the dimming signal DMS corresponding to a desired dimming degree is set so as to be substantially the same as a voltage level of the detection voltage of a case where the illumination light source16emits light with a luminance corresponding to the dimming degree.

In this way, the detection voltage corresponding to a current flowing to the illumination light source16is input to the non-inverted input terminal of the operational amplifier92, and the dimming signal DMS is input to the inverted input signal of the operational amplifier92. As a result, a signal corresponding to a difference between the detection voltage and the dimming signal DMS is output from the output terminal of the operational amplifier92. As the detection voltage becomes higher than the dimming signal DMS, an output of the operational amplifier92increases. That is, when an overcurrent flows to the illumination light source16, the output of the operational amplifier92increases. In this way, in this example, the dimming signal DMS is used as a reference value. When dimming is not performed, a substantially constant DC voltage which is a reference value may be input to the inverted input terminal of the operational amplifier92.

A collector of the semiconductor device91is connected to the DC-DC converter21b. An emitter of the semiconductor device91is connected to the low potential terminal30dof the rectifier circuit30. A base of the semiconductor device91is connected to the output terminal of the operational amplifier92. As a result, a collector current of the semiconductor device91is controlled by the output from the operational amplifier92.

As described above, when the detection voltage is higher than the dimming signal DMS, the output of the operational amplifier92increases. Accordingly, for example, when the detection voltage is higher than the dimming signal DMS, the semiconductor device91is switched on; and when the detection voltage is lower than or equal to the dimming signal DMS, the semiconductor device91is switched off. For example, as the detection voltage becomes higher than the dimming signal DMS, the collector current of the semiconductor device91increases.

When the semiconductor device91is switched on, the DC-DC converter21bstops the power supply to the illumination load12. As a result, an overcurrent can be inhibited from flowing to the illumination light source16.

FIGS. 2A and 2Bare graphs illustrating an operation of a controller according to an embodiment.

Hereinafter, an operation example in which the protection circuit48detects that the impedance of the backup capacitor50does not decrease; and the integrated circuit23can perform the normal operation will be described.

For example, the controller22is activated in response to the supply of the driving voltage VDD from the controller power supply44and determines the control type of the dimmer3based on the detection voltage.

InFIGS. 2A and 2B, the horizontal axis represents the time (t); and the vertical axis represents the detection voltage Vdet.

FIG. 2Aillustrates a waveform example of the detection voltage Vdet when the AC voltage VCT is supplied from the phase control dimmer3.

FIG. 2Billustrates a waveform example of the detection voltage Vdet when the AC voltage VCT is supplied from the reverse phase control dimmer3.

As illustrated inFIGS. 2A and 2B, the controller22sets a first threshold voltage Vth1 and a second threshold voltage Vth2 for the detection voltage Vdet. The absolute value of the second threshold voltage Vth2 is higher than the absolute value of the first threshold voltage Vth1. The first threshold voltage Vth1 is, for example, approximately 1 V. The second threshold voltage Vth2 is, for example, approximately 3 V.

The controller22keeps a time dt until the detection voltage Vdet reaches the second threshold voltage Vth2 after the detection voltage Vdet reaches the first threshold voltage Vth1. The controller22acquires a gradient dV/dt from a difference dV between the first threshold voltage Vth1 and the second threshold voltage Vth2; and the time dt. The controller22determines whether the gradient dV/dt is higher than or equal to a predetermined value; determines the type of the conduction angle control as phase control when the gradient dV/dt is higher than or equal to the predetermined value; and determines the type of the conduction angle control as reverse phase control when the gradient dV/dt is lower than the predetermined value. In order to keep the time dt, for example, an internal clock may be used, or a timer may be provided outside the apparatus.

The controller22regularly performs the determination until the input of the power supply voltage VIN or the AC voltage VCT stops. The determination may be performed, for example, on a half-wave basis of the power supply voltage VIN or the AC voltage VCT or on a half-wave basis of a predetermined number.

FIGS. 3A to 3Care graphs schematically illustrating an operation of a controller according to an embodiment.

FIGS. 3A to 3Cillustrate an operation example of the controller22when the type of the conduction angle control is determined as phase control.

InFIGS. 3A to 3C, the horizontal axis represents the time t.

InFIG. 3A, the vertical axis represents the detection voltage Vdet.

InFIG. 3B, the vertical axis represents a voltage value of the control signal CGS.

InFIG. 3C, the vertical axis represents a voltage which is input to the controller power supply44.

As illustrated inFIGS. 3A to 3C, when the controller22determines the type of the conduction angle control as phase control, the controller22detects the conduction angle of the AC voltage VCT based on the determination result. For example, the controller22determines a period in which the detection voltage Vdet is higher than or equal to the first threshold voltage Vth1 as a conduction period Ton for the conduction angle control of the dimmer3. In addition, the controller22determines a period in which the detection voltage Vdet is lower than the first threshold voltage Vth1 as a blocking period Toff for the conduction angle control of the dimmer3. As a result, the controller22detects the conduction angle of the AC voltage VCT based on a ratio of the conduction period Ton and the blocking period Toff. The conduction angle may be detected based on the second threshold voltage Vth2. The conduction angle may be detected based on a threshold different from the first threshold voltage Vth1 and the second threshold voltage Vth2.

After detecting the conduction angle of the AC voltage VCT, the controller22generates the dimming signal DMS with a duty ratio corresponding to the conduction angle and inputs the generated dimming signal DMS to the overcurrent protection unit24. As a result, the illumination light source16is dimmed according to the AC voltage VCT of which the conduction angle is controlled by phase control.

In addition, when a value of the detection voltage Vdet is lower than the first threshold voltage Vth1, the controller22sets the control signal CGS as Lo. That is, the controller22switches off the switching device61and switches the current regulator42to the first state. When a value of the detection voltage Vdet is higher than or equal to the first threshold voltage Vth1, the controller22sets the control signal CGS as Hi. That is, the controller22switches on the switching device61and switches the current regulator42to the second state. In other words, when the AC voltage VCT is lower than a predetermined value, the controller22switches the current regulator42to the first state; and when the AC voltage VCT is higher than or equal to the predetermined value, the controller22switches the current regulator42to the second state.

In addition, when the type of the conduction angle control is determined as phase control, the controller22delays a time when the current regulator42is switched from the first state to the second state to be slower by a first micro time MT1 than a time when a voltage value of the detection voltage Vdet is switched from the state of being lower than the first threshold voltage Vth1 to the state of being higher than or equal to the first threshold voltage Vth1.

For example, it is assumed that a triac is used for the dimmer3which performs the conduction angle control using phase control; and an LED is used as the illumination light source16. A consumption current of the LED is lower than that of an incandescent lamp or the like. Therefore, unless the above-described operation is performed, a holding current, which is required for turning on the triac when the AC voltage VCT is lower than or equal to a predetermined value, cannot flow. Therefore, the operation of the dimmer3may be unstable.

On the other hand, in the power supply circuit14according to the embodiment, by controlling the operation of the current regulator42as described above, the holding current, which is required for turning on the triac when the AC voltage VCT is lower than or equal to a predetermined value, can flow to the current regulator42(to the input terminal40of the integrated circuit23). As a result, the operation of the dimmer3can be stabilized. In addition, by delaying the switching time of the current regulator42by the first micro time MT1, the operation of the dimmer3can be further stabilized.

When the current regulator42is in the second state, the power is not supplied to the controller power supply44. Accordingly, when the type of the conduction angle control is determined as phase control, the power is not supplied to the controller power supply44in a period obtained by decreasing the conduction period Ton by the first micro time MT1. In this way, when the type of the conduction angle control is determined as phase control, the controller22switches the current regulator42to the second state and decreases the power supply to the controller power supply44in at least a part of the conduction period Ton. For example, the controller22stops the power supply to the controller power supply44.

When the type of the conduction angle control is determined as phase control, in the blocking period Toff and the period of the first micro time MT1, a voltage is input to the regulator74and the backup capacitor50; and the regulator74operates due to the input voltage. On the other hand, in the remaining period (period obtained by subtracting the first micro time MT1 from the conduction time Ton), the regulator74operates due to charges accumulated in the backup capacitor50.

FIGS. 4A to 4Care graphs schematically illustrating an operation of a controller according to an embodiment.

FIGS. 4A to 4Cillustrate an operation example of the controller22when the type of the conduction angle control is determined as reverse phase control.

The horizontal axis and the vertical axis ofFIGS. 4A to 4Care the same as those ofFIGS. 3A to 3C.

As illustrated inFIGS. 4A to 4C, when the controller22determines the type of the conduction angle control as reverse phase control, first, the controller22also detects the conduction angle of the AC voltage VCT. For example, the controller22determines a period in which the detection voltage Vdet is higher than or equal to the first threshold voltage Vth1 as a conduction period Ton for the conduction angle control of the dimmer3. In addition, the controller22determines a period in which the detection voltage Vdet is lower than the first threshold voltage Vth1 as a blocking period Toff for the conduction angle control of the dimmer3. As a result, the controller22detects the conduction angle of the AC voltage VCT based on a ratio of the conduction period Ton and the blocking period Toff.

After detecting the conduction angle of the AC voltage VCT, the controller22generates the dimming signal DMS with a duty ratio corresponding to the conduction angle and inputs the generated dimming signal DMS to the overcurrent protection unit24. As a result, the illumination light source16can be dimmed according to the AC voltage VCT of which the conduction angle is controlled by reverse phase control.

When a value of the detection voltage Vdet is lower than the first threshold voltage Vth1, the controller22sets the control signal CGS as Lo and switches the current regulator42to the first state. When a value of the detection voltage Vdet is higher than or equal to the first threshold voltage Vth1, the controller22sets the control signal CGS as Hi and switches the current regulator42to the second state.

In addition, when the type of the conduction angle control is reverse phase control, the controller22advances a time when the current regulator42is switched from the second state to the first state to be faster by a second micro time MT2 than a time when a voltage value of the detection voltage Vdet is switched from the state of being higher than or equal to the first threshold voltage Vth1 to the state of being lower than the first threshold voltage Vth1.

For example, the controller22stores a time of the half-wave conduction period Ton which is detected in the previous cycle; and switches the current regulator42from the second state to the first state at a time which is faster by the second micro time MT2 than the time of the half-wave conduction period Ton.

In reverse phase control, due to the effect of charges accumulated in the filter capacitor36or the like, the conduction period Ton may be longer than the actual conduction period of the dimmer3. When the conduction period Ton is longer than the actual conduction period, for example, the duty ratio of the dimming signal DMS changes; and the dimming degree of the illumination light source16changes.

By setting the current regulator42to the first state and causing a part of a current flowing through the first power supply path26ato flow to the input terminal40of the integrated circuit23, the charges accumulated in the filter capacitor36or the like can be drawn to the current regulator42. As a result, in the power supply circuit14, the conduction angle of the AC voltage VCT subjected to reverse phase control can be more reliably detected. The illumination light source16can be dimmed with high precision. In addition, as described above, by advancing the switching time of the current regulator42by the second micro time MT2, the charges accumulated in the filter capacitor36or the like can be more appropriately drawn. The detection precision of the conduction angle can be further enhanced.

When the type of the conduction angle control is determined as reverse phase control, the power is not supplied to the controller power supply44in a period obtained by decreasing the conduction period Ton by the second micro time MT2. In this way, when the type of the conduction angle control is determined as reverse phase control, the controller22switches the current regulator42to the second state and decreases the power supply to the controller power supply44in at least a part of the conduction period Ton. For example, the controller22stops the power supply to the controller power supply44.

When the type of the conduction angle control is determined as reverse phase control, in the blocking period Toff and the period of the second micro time MT2, a voltage is input to the regulator74and the backup capacitor50; and the regulator74operates due to the input voltage. On the other hand, in the remaining period (period obtained by subtracting the second micro time MT2 from the conduction time Ton), the regulator74operates due to charges accumulated in the backup capacitor50.

In the power supply circuit14according to the embodiment, the current regulator42and the controller power supply44are integrated on the integrated circuit23. As a result, for example, the size of the circuit can be reduced. For example, the circuit can be easily mounted to a light bulb type housing or the like.

In addition, in the power supply circuit14according to the embodiment, when the impedance of the backup capacitor50decreases, a current flowing to the input terminal40of the integrated circuit23decreases. As a result, for example, when the backup capacitor50is short-circuited, a high current is inhibited from flowing to the integrated circuit23. For example, heat generation of the integrated circuit23caused by a high current can be suppressed. Accordingly, even when a part of the circuit is integrated, deterioration in reliability can be suppressed.

In addition, in the power supply circuit14, in the power-on state, the path switching unit66of the integrated circuit23is activated in the third path. When the impedance of the backup capacitor50decreases, the path switching unit66is switched to the second path. The maximum value of a current flowing through the third path is higher than the maximum value of a current flowing through the second path. As a result, the charging of the backup capacitor50is promoted, and the detection of the impedance of the backup capacitor50can be promoted.

The path switching unit66may be activated in the second path without providing the third path. However, in this case, since a time is required for charging the backup capacitor50, a time is required for the detection. When the third path is not provided, that is, when the third resistor R3is not provided, for example, it is only necessary that a state in which the first resistor R1and the second resistor R2are connected to each other in parallel be set as a first path; and a state in which only the first resistor R1is connected be set as a second path. In addition, when the third path is provided, as described above, the maximum value of a current flowing through the third path is lower than the maximum value of a current flowing through the first path. As a result, for example, when the protection circuit48is broken, a high current is inhibited from flowing to the integrated circuit23.

In the above-described embodiments, when the impedance of the backup capacitor50decreases, the path switching unit66is switched to the second path to decrease a current flowing to the input terminal40of the integrated circuit23. However, the embodiment is not limited thereto. By switching off a path which is connected to the input terminal40, a current flowing to the input terminal40may be practically blocked.

For example, it is assumed that there is a power supply circuit which supplies power to a controller power supply in all the phases of an AC voltage. In such a power supply circuit, a current flows to the controller power supply, for example, even in a phase angle period which is unnecessary for dimming; and the power loss of the power supply circuit is huge.

On the other hand, in the power supply circuit14according to the embodiment, the conduction angle of the AC voltage VCT is detected; and the power supply to the controller power supply44is decreased in at least a part of the conduction period Ton of the detected conduction angle. In addition, at least when the AC voltage VCT is switched from the conduction period Ton to the blocking period Toff, the power is supplied to the controller power supply44. As a result, in the power supply circuit14, power loss can be suppressed. In addition, by suppressing power loss, heat generation of the power supply circuit14can be suppressed. In addition, by suppressing the heat generation, the current regulator42and the controller power supply44can be easily integrated.

In addition, in the power supply circuit14, in the case of phase control, the backup capacitor50is charged with a current for causing the holding current to flow to the triac of the dimmer3; and in the case of reverse phase control, the backup capacitor50is charged with a current for drawing charges from the filter capacitor36or the like. As a result, power loss can be more appropriately suppressed.

In addition, in the power supply circuit14, the constant power circuit80is provided on the controller power supply44such that power consumed in the controller power supply44is made to be substantially constant. As a result, for example, when an input voltage is high (when the absolute value of the AC voltage VCT is high), an increase in power loss can be suppressed. The power loss of the power supply circuit14can be more appropriately suppressed. The constant power circuit80is not limited to the above-described circuit and may be any circuit capable of making the power consumed in the controller power supply44substantially constant.

Hereinbefore, the embodiments are described using the specific examples. However, the embodiments are not limited thereto, and various modifications can be made.

The illumination light source16is not limited to an LED. For example, organic electro-luminescence (organic EL) or organic light-emitting diode (OLED) may be used. In the illumination load12, plural illumination light sources16may be connected to each other in series or in parallel.

In the above-described embodiments, the illumination load12is described as a load. However, the load is not limited thereto. For example, a heater or other loads may be used. In the above-described embodiments, the power supply circuit14which is used for the illumination apparatus10is described as a power supply circuit. However, the power supply circuit is not limited thereto. For example, any power supply circuit corresponding to a load may be used. In addition, a voltage which is supplied to a load is not limited to a DC voltage. For example, an AC voltage or a ripple voltage may be used.