JP2011258431A - Power supply circuit, illumination device and illumination system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power supply circuit which supplies normal electric power to a load even if a phase control dimmer malfunctions.SOLUTION: The power supply circuit 821 inputs phase-controlled AC power to generate DC power. A rectifier circuit 110 rectifies the phase-controlled AC power. A DC-DC converter circuit 120 generates DC power from the electric power that the rectifier circuit rectifies. A delay circuit 140 allows the DC-DC converter circuit 120 to start operating after the power supply circuit 821 starts inputting the phase-controlled AC power and a predetermined delay time is passed.

Description

  The present invention relates to a power supply circuit that supplies power to a load such as an LED.

In order to limit the power supplied to a load such as a light bulb, there is a technique for controlling the phase of AC power supplied to the load using a thyristor or the like.
Some illumination systems that use a light bulb as a light source use a phase control dimmer to dimm the brightness of the light bulb. There is an illumination system in which a light source is an LED and a power supply circuit that supplies electric power to the LED inputs phase-controlled AC power.

JP 2004-296205 A

In some rare cases, the phase control dimmer may malfunction. In spite of the low dimming degree, the phase control does not work immediately after the power is turned on, and a large amount of power may be supplied to the load. Since this is an event on the order of milliseconds, there is no problem for a load with a slow response such as a light bulb. On the other hand, in the case of a load with a quick response like an LED, there may be a flash phenomenon in which the LED is lit brightly for a moment.
The present invention has been made to solve the above-described problems, for example, and has an object to supply a normal power to a load even when a phase control dimmer malfunctions. To do.

  A power supply circuit according to the present invention is a power supply circuit that receives phase-controlled AC power and generates DC power, a rectifier that rectifies the phase-controlled AC power, and power rectified by the rectifier circuit, The DC / DC converter circuit that generates the DC power and the power supply circuit start the operation of the DC / DC converter circuit after a predetermined delay time has elapsed since the input of the phase-controlled AC power was started. And a delay circuit.

  According to the power supply circuit of the present invention, even when the phase control dimmer malfunctions, normal power can be supplied to the load.

FIG. 2 is a system configuration diagram showing a configuration of an illumination system 800 in the first embodiment. FIG. 3 shows a configuration of a phase control dimmer 810 and a light source circuit 822 in Embodiment 1. FIG. 6 is a waveform diagram showing an example of a voltage waveform 711 of AC power phase-controlled by the phase control dimmer 810 in the first embodiment. The wave form diagram which shows another example of the voltage waveform 711 of the alternating current power which the phase control dimmer 810 in Embodiment 1 phase-controlled. The wave form diagram which shows another example of the voltage waveform 711 of the alternating current power which the phase control dimmer 810 in Embodiment 1 controlled in phase. 3 is a circuit configuration diagram illustrating a circuit configuration of a power supply circuit 821 in Embodiment 1. FIG. FIG. 3 is a waveform diagram showing an example of a voltage waveform at each part in the first embodiment. FIG. 6 is a waveform diagram showing another example of the voltage waveform at each part in the first embodiment.

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

FIG. 1 is a system configuration diagram showing a configuration of an illumination system 800 in this embodiment.
The illumination system 800 includes a phase control dimmer 810 and an illumination device 820. The illumination system 800 is, for example, a phase control dimming LED system.

  The phase control dimmer 810 inputs the dimming degree, and phase-controls the AC power supplied from the AC power source AC such as a commercial power source according to the input dimming degree. That is, the phase control dimmer 810 conducts / cuts off the power supply line that supplies power from the AC power source AC such as a commercial power source to the lighting device 820 according to the phase of the voltage, thereby supplying power supplied to the lighting device 820. Adjust.

  The lighting device 820 includes a power supply circuit 821 and a light source circuit 822.

  The power supply circuit 821 receives AC power phase-controlled by the phase control dimmer 810 and generates DC power. The DC power generated by the power supply circuit 821 is supplied to the light source circuit 822. The power supply circuit 821 is, for example, an LED lighting device.

  The light source circuit 822 is connected to the power supply circuit 821. The light source circuit 822 includes a light source. The light source is turned on by DC power supplied from the power supply circuit 821. The light source circuit 822 is, for example, an LED module.

  FIG. 2 is a diagram showing the configuration of the phase control dimmer 810 and the light source circuit 822 in this embodiment.

  The light source circuit 822 includes one or more light sources 823. The light source 823 is, for example, a light emitting diode (LED). The number of the light sources 823 is four, for example. The number of the light sources 823 may be any number. When the number of light sources 823 is plural, the light sources 823 are electrically connected in series, for example. The plurality of light sources 823 may be electrically connected in parallel, for example, or a circuit in which a plurality of light sources 823 are electrically connected in series may be electrically connected in parallel. When a plurality of light sources 823 (or a circuit in which the light sources 823 are connected in series) are connected in parallel, the light source circuit 822 has a configuration for equalizing the current flowing through the plurality of light sources 823, such as a current mirror circuit. It may be.

  The phase control dimmer 810 includes, for example, a dimming signal input terminal 811, a thyristor 812, and a control circuit 813.

  The dimming signal input terminal 811 is a terminal for inputting a dimming signal. The dimming signal represents the dimming degree. The phase control dimmer 810 may be configured to input a dimming signal from an infrared light receiver, for example, instead of inputting the dimming signal from the dimming signal input terminal 811. Further, the phase control dimmer 810 is not configured to input the dimming degree by the dimming signal, but may be configured to input the dimming degree by inputting a user's operation using a rotary knob or an operation button. Good.

  The thyristor 812 is interposed in a power supply line that supplies AC power from the AC power supply AC to the power supply circuit 821. The thyristor 812 is a switch that is turned on when the drive pulse generated by the control circuit 813 is input and turned off when the flowing current becomes zero.

  The control circuit 813 generates a drive pulse that drives the thyristor 812. The control circuit 813 detects the zero crossing of the voltage of the AC power supplied from the AC power supply AC. The control circuit 813 generates a drive pulse when a delay time according to the input light control level has elapsed from the time when the zero cross is detected. The delay time is smaller as the dimming degree is higher (brighter) and larger as the dimming degree is lower (darker).

FIG. 3 is a waveform diagram showing an example of a voltage waveform 711 of AC power phase-controlled by the phase control dimmer 810 in this embodiment.
The thyristor 812 is turned on after the control circuit 813 generates the drive pulse until the voltage of the AC power supplied from the AC power supply AC becomes zero. During this period (conduction period 702), the voltage waveform 711 of AC power phase-controlled by the phase control dimmer 810 is substantially equal to the voltage waveform of AC power supplied from the AC power supply AC. In periods other than the conduction period 702, the AC power phase-controlled by the phase control dimmer 810 is cut off and the voltage becomes zero.
The conduction period 702 is less than or equal to half the period 701 of AC power supplied from the AC power supply AC. The conduction period 702 expressed by a phase angle is called a conduction angle. The conduction angle is theoretically not less than 0 degrees and not more than 180 degrees. In practice, the lower limit of the conduction angle is greater than 0 degrees and the upper limit of the conduction angle is less than 180 degrees.

  When the dimming degree is high, the control circuit 813 generates a drive pulse with a short delay time after the voltage of the AC power supplied from the AC power supply AC crosses zero, so that the conduction period 702 becomes longer as shown in this figure. The conduction angle increases. Thereby, the power supplied from the AC power supply AC to the lighting device 820 increases, and the light source 823 is lit brightly.

  Although the current waveform is not shown, for example, there is a differential current (pulse current) that flows at the moment when the thyristor 812 is turned on, and a current that flows during the period when the thyristor 812 is turned on.

  FIG. 4 is a waveform diagram showing another example of a voltage waveform 711 of AC power phase-controlled by the phase control dimmer 810 in this embodiment.

  When the dimming degree is low, the control circuit 813 generates a drive pulse with a long delay time after the voltage of the AC power supplied from the AC power supply AC crosses zero, so that the conduction period 702 is shortened as shown in this figure. The conduction angle becomes small. Thereby, the power supplied from the AC power supply AC to the lighting device 820 is reduced, and the light source 823 is lit darkly.

FIG. 5 is a waveform diagram showing still another example of a voltage waveform 711 of AC power phase-controlled by the phase control dimmer 810 in this embodiment.
The phase control dimmer 810 may malfunction immediately after the power is turned on.

  For example, if the power is turned on at time 721, the thyristor 812 may be kept on during the next half cycle (half cycle). This period is called an erroneous conduction period 703. Originally, since the thyristor 812 is turned on only during the conduction period 702, the power supplied from the AC power supply AC to the lighting device 820 should be small, but during the erroneous conduction period 703, the thyristor 812 is turned on for a half cycle. Since the state is maintained, large power is supplied from the AC power supply AC to the lighting device 820.

  The cause of malfunction is thought to be due to current delay, but it will not be described in detail here. The illumination system 800 of this embodiment does not prevent malfunction of the phase control dimmer 810, and the illumination system 800 operates normally as a whole even if the phase control dimmer 810 malfunctions. .

FIG. 6 is a circuit configuration diagram showing a circuit configuration of the power supply circuit 821 in this embodiment.
The power supply circuit 821 includes a rectifier circuit 110, a DC / DC conversion circuit 120, a control power supply circuit 130, and a delay circuit 140.

  The rectifier circuit 110 rectifies the phase-controlled AC power input from the phase control dimmer 810 by the power supply circuit 821 to make the voltage waveform a pulsating current (phase-controlled). The rectifier circuit 110 includes a diode bridge 111, for example. The diode bridge 111 is a bridge connection of four diodes and performs full-wave rectification.

The DC / DC converter circuit 120 receives the power rectified by the rectifier circuit 110, converts the input power, and generates DC power. The DC power generated by the DC / DC conversion circuit 120 is supplied to the light source circuit 822 as an output of the power supply circuit 821. The DC / DC converter circuit 120 is a DC-DC converter circuit.
The DC / DC conversion circuit 120 is, for example, a flyback converter circuit. The DC / DC conversion circuit 120 includes, for example, a control IC 121, a switching element Q22, a transformer T23, a diode D26, and a smoothing capacitor C27.

The control IC 121 operates using the DC control power supplied from the control power circuit 130 as a power source. The control IC 121 turns on / off the switching element Q22 at a high frequency. The control IC 121 includes a ground terminal GND, a power supply terminal VCC, an output terminal OUT, and a protection signal input terminal OVP.
The ground terminal GND is electrically connected to a ground wiring having a primary side reference potential of the power supply circuit 821. The power supply terminal VCC is electrically connected to the output of the control power supply circuit 130. The control IC 121 receives the DC control power generated by the control power supply circuit 130 via the power supply terminal VCC. The output terminal OUT outputs a drive signal for driving the switching element Q22. The protection signal input terminal OVP inputs a protection signal. The protection signal input terminal OVP is, for example, an overvoltage protection terminal. The control IC 121 stops its operation while inputting the protection signal. That is, the control IC 121 does not generate a drive signal for turning on and off the switching element Q22 at a high frequency, and keeps the switching element Q22 in the off state. In this example, the control IC 121 determines that a protection signal is input when the potential of the protection signal input terminal OVP is high.

  The switching element Q22 is a switch that is turned on / off by a drive signal generated by the control IC 121. The switching element Q22 is, for example, an enhancement type NMOS field effect transistor (FET).

  The transformer T23 has two coils L24 and L25 that are magnetically coupled. The primary coil L24 is electrically connected in series with the switching element Q22 and is electrically connected to the output of the rectifier circuit 110. When the switching element Q22 is on, the pulsating voltage of the power rectified by the rectifier circuit 110 is applied to both ends of the primary side coil L24, and a current flows through the primary side coil L24. When the switching element Q22 is turned off, the current flowing through the primary coil L24 becomes zero. A voltage proportional to the voltage across the primary coil L24 is generated at both ends of the secondary coil L25.

  The secondary coil L25, the diode D26, and the smoothing capacitor C27 of the transformer T23 are electrically connected to each other to form a closed circuit. The diode D26 is a rectifier circuit. The direction of the diode D26 is a direction in which current flows only in the direction in which the smoothing capacitor C27 is charged. The direction of the secondary coil L25 is a direction in which a voltage is generated that turns off the diode D26 when the switching element Q22 is on. When the switching element Q22 is on, the diode D26 is turned off by the voltage generated at both ends of the secondary coil L25, so that no current flows through the coil L25. When the switching element Q22 is turned off, a current proportional to the current that has been flowing through the primary coil L24 until then flows through the coil L25. The diode D26 is turned on, and the smoothing capacitor C27 is charged by the current flowing through the secondary coil L25. The smoothing capacitor C27 smoothes the current flowing through the secondary coil L25. Both ends of the smoothing capacitor C27 are electrically connected to the light source circuit 822 as outputs of the DC / DC conversion circuit 120 (and the power supply circuit 821).

  The smoothing capacitor C27 is charged only during the conduction period 702 in which the thyristor 812 is on. Therefore, if the conduction period 702 is long, the DC power supplied from the power supply circuit 821 to the light source circuit 822 becomes large, and the light source 823 is lit brightly. On the other hand, if the conduction period 702 is short, the DC power supplied from the power supply circuit 821 to the light source circuit 822 becomes small, and the light source 823 is lit darkly. In this way, phase control dimming in which the brightness of the light source 823 is changed by changing the conduction angle of the phase control dimmer 810 is realized.

  Further, when the control IC 121 does not generate a drive signal for turning on and off the switching element Q22 at a high frequency and the switching element Q22 is continuously off, no current flows through the temporary side coil L24. No current flows and the smoothing capacitor C27 is not charged. For this reason, the light source 823 is not turned on.

  The control power supply circuit 130 receives the power rectified by the rectifier circuit 110, converts the input power, and generates DC control power (control power supply). The DC control power generated by the control power supply circuit 130 is supplied to the DC / DC conversion circuit 120. The control power circuit 130 is a control DC power generation circuit. The control power supply circuit 130 includes, for example, a three-terminal regulator 131.

The delay circuit 140 delays the start of operation of the DC / DC conversion circuit 120. The delay circuit 140 starts the operation of the DC / DC converter circuit 120 after a predetermined delay time has elapsed after the power supply circuit 821 starts to input the phase-controlled AC power.
The delay time is, for example, not less than 0.5 times and not more than 3 times the cycle of the AC power supply AC. As described above, the erroneous conduction period 703 of the phase control dimmer 810 corresponds to a half cycle of the AC power supply AC. For this reason, the delay time is required to be more than a half cycle of the AC power supply AC. For example, if the frequency of the AC power supply AC is 50 Hz, the delay time is set to 10 milliseconds or more, and if it is 60 Hz, it is set to 8.33 milliseconds or more. In order to make the power supply circuit 821 correspond to two or more frequencies, the delay time is set to the delay time when the frequency is the lowest. For example, in order to correspond to 50 Hz and 60 Hz, the delay time is set to 10 milliseconds or more.
Conversely, it is not necessary to set the delay time too long. If the delay time is set too long, it may be recognized as a reaction delay by the user, or the phase control dimmer 810 may repeatedly malfunction. For this reason, it is desirable that the delay time be one cycle or less of the AC power supply AC. Depending on the configuration of the delay circuit 140, if the power is turned on again immediately after the power is turned off, the delay time may be shorter than the set value. . In that case, it is desirable to set the delay time to 3 cycles or less of the AC power supply AC. For example, when the frequency of the AC power supply AC is 60 Hz, the delay time is set to 50 milliseconds or less.

The delay circuit 140 is, for example, a differentiation circuit. The delay circuit 140 includes, for example, two voltage dividing resistors R41 and R42, a voltage dividing capacitor C43, and a diode D44. The two voltage dividing resistors R41 and R42 are electrically connected in series with each other, and are electrically connected to the output of the control power supply circuit 130. A connection point between the two voltage dividing resistors R41 and R42 is electrically connected to a protection signal input terminal OVP of the control IC 121. The voltage dividing capacitor C43 is electrically connected in parallel with the voltage dividing resistor R41. The diode D44 is a rectifier circuit. The diode D44 is electrically connected in parallel with the voltage dividing resistor R42. The direction of the diode D44 is a direction that turns off when the voltage of the DC control power generated by the control power supply circuit 130 is positive. The diode D44 is for quickly extracting the charge charged in the voltage dividing capacitor C43 when the voltage of the DC control power generated by the control power supply circuit 130 becomes zero. It should be noted that a capacitor having a relatively small capacitance may be electrically connected in parallel with each of the two voltage dividing resistors R41 and R42 in order to extract the electric charge of the voltage dividing capacitor C43 more quickly.
The voltage dividing ratio of the two voltage dividing resistors R41 and R42 is set so that the potential of the protection signal input terminal OVP is lowered to a potential lower than a threshold voltage for determining whether or not the control power supply circuit 130 is inputting a protection signal. The resistance value of the voltage dividing resistor R42 and the capacitance of the voltage dividing capacitor C43 are such that the potential of the protection signal input terminal OVP is lowered to the threshold voltage for determining whether or not the control power supply circuit 130 is inputting the protection signal. This time is set to be 0.5 to 3 times the cycle of the AC power supply AC.

FIG. 7 is a waveform diagram showing an example of the voltage waveform of each part in this embodiment.
The horizontal axis indicates time. The vertical axis represents voltage.
A voltage waveform 711 indicated by a thick solid line is a voltage waveform of AC power subjected to phase control input by the power supply circuit 821. In this example, due to a malfunction of the phase control dimmer 810, there is a half-cycle erroneous conduction period 703.
A voltage waveform 714 indicated by a thick solid line is a voltage waveform of DC control power generated by the control power supply circuit 130. The control power supply circuit 130 adjusts so that the voltage of the generated DC control power does not exceed the voltage 704 indicated by the thin broken line. The control IC 121 becomes operable when the voltage of the DC control power generated by the control power supply circuit 130 exceeds the voltage 705 indicated by a thin broken line.
A voltage waveform 715 indicated by a thick broken line is a voltage waveform of the protection signal generated by the delay circuit 140. The control IC 121 determines that the protection signal has been input when the potential of the protection signal generated by the delay circuit 140 exceeds the voltage 706 indicated by the thin broken line. The voltage 706 is lower than the voltage 705.
A voltage 707 indicated by a thin broken line is a voltage obtained by dividing the voltage 704 by the voltage dividing ratio of the two voltage dividing resistors R41 and R42. The voltage 707 is lower than the voltage 706.

At time 721, power is turned on.
At time 722, a false conduction period 703 begins. The voltage value of the DC control power generated by the control power supply circuit 130 gradually increases and exceeds the voltage 705 at which the control IC 121 can operate at time 723.
Prior to time 722, voltage dividing capacitor C43 is not charged. For this reason, the potential of the protection signal generated by the delay circuit 140 is equal to the voltage value of the DC control power generated by the control power supply circuit 130. After time 722, the voltage dividing capacitor C43 is gradually charged, and the potential of the protection signal generated by the delay circuit 140 is higher than the voltage value of the DC control power generated by the control power supply circuit 130. The potential is lowered by the amount of the voltage across C43.
At time 723, since the voltage dividing capacitor C43 has not yet been charged so much, the potential of the protection signal generated by the delay circuit 140 exceeds the voltage 706 that the control IC 121 determines that the protection signal is input. For this reason, the control IC 121 stops the operation and continuously turns off the switching element Q22. Since the smoothing capacitor C27 is not charged, the light source 823 is not turned on.

Thereafter, as the voltage dividing capacitor C43 is charged, the potential of the protection signal generated by the delay circuit 140 decreases, and at time 724, the threshold voltage 706 for determining whether or not the control IC 121 is inputting the protection signal. Below. The control IC 121 generates a drive signal for turning on / off the switching element Q22 at a high frequency. Thereby, the DC-DC converter circuit 120 starts operation.
When the smoothing capacitor C27 is charged up to a voltage at which the light source 823 is turned on, the light source 823 is turned on with brightness corresponding to the dimming degree.

  If there is no delay circuit 140, the control IC 121 starts operation at time 723 and generates a drive signal for turning on and off the switching element Q22 at a high frequency. For this reason, during the erroneous conduction period 703, the smoothing capacitor C27 is charged to the same extent as when the dimming degree is 100%, and the light source 823 is lit brightly. Thereafter, as the smoothing capacitor C27 discharges, the light source 823 becomes darker and the brightness is adjusted to the dimming degree. That is, the light source 823 is lit brightly for a moment like a flash.

  On the other hand, since the power supply circuit 821 of this embodiment includes the delay circuit 140, the control power supply circuit 130 does not operate at least until the erroneous conduction period 703 ends. For this reason, the above flash phenomenon does not occur.

FIG. 8 is a waveform diagram showing another example of the voltage waveform of each part in this embodiment.
The horizontal axis indicates time. The vertical axis represents voltage. Portions common to those in FIG.

  In this example, since the phase control dimmer 810 did not malfunction, the power supply circuit 821 inputs AC power whose phase is normally controlled.

At time 722, the thyristor 812 is turned on, and the voltage value of the DC control power generated by the control power supply circuit 130 starts to increase.
At time 723, the voltage value of the DC control power generated by the control power supply circuit 130 exceeds the voltage 705, and the control IC 121 becomes operable. At this time, since the potential of the protection signal generated by the delay circuit 140 is higher than the voltage 706, the control IC 121 does not generate a drive signal for turning on and off the switching element Q22 at a high frequency, and the switching element Q22 maintains the off state. Therefore, the smoothing capacitor C27 is not charged and the light source 823 is not lit.
At time 724, the potential of the protection signal generated by the delay circuit 140 falls below the voltage 706, and the control IC 121 generates a drive signal for turning on and off the switching element Q22 at high frequency. The DC / DC conversion circuit 120 starts its operation. When the smoothing capacitor C27 is charged up to a voltage at which the light source 823 is turned on, the light source 823 is turned on with brightness corresponding to the dimming degree.

As described above, even when the phase control dimmer 810 does not malfunction, the control power supply circuit 130 operates with a delay corresponding to the delay time of the delay circuit 140 as in the case where the phase control dimmer 810 malfunctions. Start.
However, since the delay time of the delay circuit 140 is not more than three times the period of the AC power supply AC (60 milliseconds in the case of 50 Hz), it is hardly perceived by the user.

  Note that the DC / DC converter circuit 120 is not limited to a flyback converter circuit, and may be a non-insulated circuit such as a buck converter circuit. Alternatively, the DC / DC conversion circuit 120 may be a boost type circuit such as a boost converter circuit. The DC / DC converter circuit 120 may be a circuit having such a characteristic that power supplied to the light source circuit 822 is reduced when the conduction angle is reduced.

  Further, the configuration for delaying the start of operation of the DC / DC converter circuit 120 is not limited to the configuration using the protection signal input terminal of the control IC 121, and for example, the rise of the voltage of the DC control power generated by the control power supply circuit 130 is delayed. Thus, the configuration may be such that the control IC 121 delays reaching the voltage 705 at which the control IC 121 can operate. Alternatively, a switch is provided between the output of the rectifier circuit 110 and the input of the DC / DC converter circuit 120. The switch is turned off until the delay time elapses, and is turned on after the delay time elapses. It may be a configuration.

  The configuration described above is an example, and a configuration in which a configuration of a non-major part is replaced with another configuration such as an existing technology may be used.

  As described above, the operation start of the DC / DC converter circuit 120 is delayed until a predetermined delay time elapses after the power supply circuit 821 starts input of phase-controlled AC power, and after the delay time elapses, By starting the operation of the DC / DC conversion circuit 120, even if the phase control dimmer 810 malfunctions, the occurrence of a flash phenomenon in which the light source 823 is lit brightly for a moment can be suppressed, and the entire illumination system 800 can be suppressed. Works as normal.

  110 rectifier circuit, 111 diode bridge, 120 DC / DC converter circuit, 121 control IC, 130 control power supply circuit, 131 three-terminal regulator, 140 delay circuit, 701 period, 702 conduction period, 703 false conduction period, 704, 705, 706 707 voltage, 711, 714, 715 voltage waveform, 721, 722, 723, 724 time, 800 lighting system, 810 phase control dimmer, 811 dimming signal input terminal, 812 thyristor, 813 control circuit, 820 lighting device, 821 Power supply circuit, 822 light source circuit, 823 light source, AC AC power supply, C27 smoothing capacitor, C43 voltage dividing capacitor, D26, D44 diode, GND ground terminal, L24, L25 coil, OUT output terminal, OVP protection signal input terminal, Q22 Switching element, R41, R42 Voltage dividing resistor, T23 transformer, VCC power supply terminal.

Claims (6)

In a power supply circuit that receives phase-controlled AC power and generates DC power,
A rectifier circuit for rectifying the phase-controlled AC power;
A DC-DC converter circuit that generates the DC power from the power rectified by the rectifier circuit;
A power supply circuit comprising: a delay circuit that starts operation of the DC / DC converter circuit after a predetermined delay time has elapsed since the power supply circuit started to input the phase-controlled AC power; .   2. The power supply circuit according to claim 1, wherein a delay time of the delay circuit is not less than 0.5 times and not more than 3 times the period of the AC power. The delay circuit generates a protection signal until a predetermined delay time elapses after the power supply circuit starts inputting the phase-controlled AC power,
The DC / DC converter circuit has a protection signal input terminal for inputting the protection signal generated by the delay circuit, and stops operating when the protection signal input terminal is inputting the protection signal. The power supply circuit according to claim 1 or 2. The power supply circuit has a control power supply circuit that generates DC control power from the phase-controlled AC power,
The DC / DC converter circuit operates using the DC control power generated by the control power circuit as a power source,
The delay circuit includes a voltage dividing capacitor and a voltage dividing resistor for dividing the voltage of the DC control power generated by the control power supply circuit, and the voltage generated at both ends of the voltage dividing resistor is used as the protection signal. The power supply circuit according to claim 3. A power supply circuit according to any one of claims 1 to 4,
An illumination device comprising: a light source that is lit by direct current power generated by the power supply circuit. A phase control dimmer that inputs the dimming degree and controls the phase of the AC power according to the inputted dimming degree;
The power supply circuit according to any one of claims 1 to 4, wherein the phase control dimmer inputs AC power controlled in phase.
An illumination system comprising: a light source that is lit by DC power generated by the power supply circuit.

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