JP2017175894A - Power supply device and lighting system including power supply device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve a reliable start-up of a step-down chopper operation.SOLUTION: A power supply device of an embodiment includes a boost chopper, a step-down chopper, a signal generating circuit, a power generating circuit, and a control circuit. During other than an overshoot period from the time when a first output voltage has become a predetermined first threshold or more to the time when the first output voltage has become less than a predetermined second threshold, the control circuit controls a first switching element so as to bring the first output voltage close to a predetermined target voltage, while, during the overshoot period, the control circuit controls the first switching element in an off state. The power generating circuit includes charging means that charges using a current flow into the first switching element while the step-down chopper stops chopping, and continues generating operation power of the signal generating circuit from charges accumulated by the charging means over the entire period when the first switching element is in an off state.SELECTED DRAWING: Figure 1

Description

  Embodiments described herein relate generally to a power supply device and a lighting device including the power supply device.

  In order to realize a power supply device having harmonic improvement and constant current characteristics, a power supply device having a PFC unit and a constant current control unit, for example, boosting a voltage supplied from the outside with a boost chopper having a power factor improvement function Then, a power supply device that obtains desired power by stepping down with a step-down chopper is known. .

  In a step-down chopper, a field-effect transistor (FET) is typically used as a switching element for chopping. An FET is a switching element that can turn on / off conduction between a drain and a source by a potential difference between the gate and the source.

  For example, in a step-down chopper using an FET as a switching element, a high side configuration in which the source potential of the FET is not on the ground may be used. In this case, since the potential of the source of the FET becomes indefinite, it is necessary to devise the potential supplied to the gate.

  When starting up the power supply device, first, the operation of the step-up chopper is started, and then the operation of the step-down chopper is started. The step-down chopper generates a voltage to be supplied to the control terminal of the switching element by using a voltage obtained with the operation of the step-up chopper. For this reason, depending on the operating state of the step-up chopper, a voltage sufficient to generate a voltage to be supplied to the control terminal of the switching element may not be obtained. In such a case, the operation of the step-down chopper is normal. There was a fear that it could not be started.

JP 2015-185450 A

  An object of the present invention is to provide a power supply device capable of reliably starting a step-down chopper operation and a lighting device including such a power supply device.

  The power supply device of the embodiment includes a power factor correction circuit, a step-down chopper, a signal generation circuit, a control circuit, and a power generation circuit. The power factor correction circuit outputs a first output voltage. The step-down chopper includes, as a second switching element for chopping, an element that can turn on / off conduction between the input end and the output end due to a potential difference between the control end and the output end, and steps down the first output voltage. . The signal generation circuit generates a switching signal to be given to the control terminal for chopping by the step-down chopper. The control circuit sets the first output voltage in advance in a period other than the overshoot period from when the first output voltage becomes equal to or higher than the predetermined first threshold to below the predetermined second threshold. The first switching element is controlled to approach the predetermined target voltage, and the first switching element is turned off during the overshoot period. The power generation circuit includes charging means for charging using the current flow to the first switching element when the step-down chopper stops chopping, and the first switching element is generated from the charge stored in the charging means. The operating power of the signal generation circuit is generated over the entire period in which is in the OFF state.

  ADVANTAGE OF THE INVENTION According to this invention, the illuminating device provided with the power supply device which can start a pressure | voltage fall chopper operation | movement reliably, and such a power supply device can be provided.

The figure which shows the electric circuit structure of the illuminating device which concerns on one Embodiment. The block diagram which shows the principal part structure of the control circuit in FIG. The figure showing the time change of operation | movement of voltage VDC and the PFC control circuit in FIG. 2 at the time of starting of the illuminating device shown in FIG. Explanatory drawing of the abnormality monitoring operation | movement which concerns on one Embodiment.

  Hereinafter, embodiments will be described with reference to the drawings.

(Constitution)
FIG. 1 is a diagram illustrating an electric circuit configuration of a lighting device 100 according to the present embodiment. FIG. 1 shows a schematic circuit configuration, and illustration of some of the various elements provided in the actual circuit configuration is omitted.

  The illumination device 100 includes a light source unit 1 and a power supply device 2. The light source unit 1 is detachable from the main body of the lighting device 100. The power supply device 2 is fixedly provided on the main body.

  The light source unit 1 includes a plurality of light emitting diodes (LEDs) D11 and a resistor R11 as light sources. The plurality of light emitting diodes D11 are connected in series. The resistor R11 is connected to the current output terminal in the series circuit of the light emitting diode D11. The number of light emitting diodes D11 is arbitrary. Only one light emitting diode D11 may be provided. A plurality of series circuits of light emitting diodes D11 as shown in FIG. 1 may be connected in parallel. Terminals T11, T12, and T13 for connecting to the power supply device 2 are respectively connected to the current input terminal and the current output terminal of the series circuit of the light emitting diode D11 and the end of the resistor R11 that is not connected to the light emitting diode D11. It is connected. The light source unit 1 may be provided with another type of light emitting device such as an organic EL (electroluminescence) instead of the light emitting diode D11 as a light source. The reason why the light source unit 1 is detachable from the main body is that the light source unit 1 can be replaced. The light source unit 1 may be fixedly connected to the power supply device 2 and not replaceable.

  The power supply device 2 receives power supply from an external power supply 200 such as a commercial power supply, and generates power to be supplied to the light source unit 1 for causing the light emitting diode D11 to emit light. The power supply device 2 includes a rectifier circuit 10, a power factor correction circuit 20, a step-down chopper circuit 30, a control circuit 40, capacitors C1, C2, C3, C4, C5, C6, resistors R1, R2, R3, R4, R5, R6. , R7, R8, R9, R10 and diodes D1, D2.

  A pair of input terminals of the rectifier circuit 10 are connected to two terminals T21 and T22, respectively. Two power lines connected to an external power source 200 such as a commercial power source are connected to the two terminals T21 and T22, respectively. As a result, AC power supplied from the external power source 200 is input to the pair of input terminals of the rectifier circuit 10. The rectifier circuit 10 rectifies AC power and outputs DC power obtained thereby. The DC power output from the rectifier circuit 10 between the pair of output ends of the rectifier circuit 10 is supplied to the power factor correction circuit 20 after being smoothed by the capacitor C1.

  The power factor correction circuit 20 boosts the supplied DC power to improve the power factor. The power factor correction circuit 20 is also referred to as a PFC (power factor correction) circuit. The power factor correction circuit 20 includes a transformer Tr21, a first switching element Q21, an electrolytic capacitor C21, and a resistor R21.

  The transformer Tr21 includes a primary side coil L21 and secondary side coils L22 and L23. The first end of the coil L21 is connected to one of the output ends of the rectifier circuit 10 and one end of the capacitor C1. The other end of the capacitor C1 is connected to the ground potential of the main circuit. The drain of the first switching element Q21 and the anode of the diode D20 are connected to the second end of the coil L21, and the cathode of the diode D20 and the first end of the electrolytic capacitor C21 are connected. The source of the first switching element Q21 is connected to the CS terminal of the control circuit 40 and is connected to the ground potential via the resistor R21. The second end of the electrolytic capacitor C21 is connected to the ground potential. The gate of the first switching element Q21 is connected to the GD terminal of the control circuit 40. In the present embodiment, an FET is used as the first switching element Q21. Thus, the coil L21, the first switching element Q21, the diode D20, and the electrolytic capacitor C21 form a boost chopper circuit. The potential difference between the potential at the connection point between the second end of the coil L21 and the first end of the electrolytic capacitor C21 and the ground potential becomes the output voltage VDC of the power factor correction circuit 20. The voltage VDC is supplied to the step-down chopper circuit 30 and is supplied between the VDC terminal and the LGND terminal of the control circuit 40.

  One end of the coil L22 is connected to the VB terminal of the control circuit 40 via a rectifier circuit formed by connecting a resistor R1, a capacitor C2, and a diode D1 in series. The other end of the coil L22 is connected to the VS terminal of the control circuit 40. Thus, the coil L22 induces a voltage based on the potential of the VS terminal by the current generated in the coil L21, and supplies the voltage between the VB terminal and the VS terminal of the control circuit 40.

  One end of the coil L23 is connected to the ZCD terminal of the control circuit 40 via the resistor R23, and the other end is connected to the ground potential. Thus, the coil L23 induces a voltage based on the ground potential by the current generated in the coil L21, and supplies the voltage to the ZCD terminal of the control circuit 40.

  The resistors R2 and R3 are connected in series between one of the output ends of the rectifier circuit 10 and the ground. Thus, the resistors R2 and R3 form a voltage dividing circuit that divides the potential difference between the output terminal potential of the rectifier circuit 10 and the ground potential, that is, the voltage supplied to the power factor correction circuit 20. A connection point between the resistor R2 and the resistor R3 is connected to the MULT terminal of the control circuit 40.

  The resistors R4 and R5 are connected in parallel between the first end and the second end of the electrolytic capacitor C21. As a result, the resistors R4 and R5 form a voltage dividing circuit that divides the potential difference between the potential at the second end of the coil L21 and the ground potential, that is, the voltage supplied from the power factor correction circuit 20 to the step-down chopper circuit 30. ing. A connection point between the resistor R4 and the resistor R5 is connected to the VFB terminal of the control circuit 40.

  The diode D2 has its anode and cathode connected to the Vcc terminal and VB terminal of the control circuit 40, respectively. Thus, the diode D2 passes the current output from the Vcc terminal of the control circuit 40 so as to be input to the VB terminal. Further, the diode D2 prevents a backflow with respect to the VS terminal.

  The capacitor C3 is connected to the VS terminal and the VB terminal of the control circuit 40, respectively. The capacitor C3 has a voltage output from the rectifier circuit formed by the resistor R1, the capacitor C2, and the diode D1 and a voltage Vcc described later output from the Vcc terminal when the potential of the VB terminal is higher than the potential of the VS terminal. Is charged.

  The step-down chopper circuit 30 includes at least a second switching element Q31, a coil L31, a diode D31, and a capacitor C31. Note that L32 is not necessarily used as a filter, but may be omitted.

  In the present embodiment, an FET is used as the second switching element Q31. The drain of the second switching element Q31 is connected to the first end of the capacitor 21 of the power factor correction circuit 20. That is, the drain of the second switching element Q31 corresponds to the input terminal of the step-down chopper circuit 30. The gate which is the control end of the second switching element Q31 is connected to the HO terminal of the control circuit. The source as the output end of the second switching element Q31 is connected to one end of the coil L31. The other end of the coil L31 is an output of the step-down chopper circuit. The source of the second switching element Q31 is connected to the ground potential via a series circuit of a coil L32 and a diode D31. The anode of the diode D31 is connected to the ground potential. Thus, the second switching element Q31, coils L31 and L32, diode D31 and capacitor C31 form a step-down chopper. The resistor R31 is for detecting the current flowing through the light emitting diode D11, and generates a potential having a magnitude corresponding to the current at a connection point between the capacitor C31 and the resistor R31. The connection point between the capacitor C31 and the resistor R31 is connected to the OCP terminal of the control circuit 40 via the resistor R6.

  The connection point between the coil L31 and the capacitor C31 corresponds to the output terminal of the step-down chopper. This connection point is connected to a terminal T31 that contacts the terminal T11 of the light source unit.

  The resistor R32 is connected at both ends to terminals T32 and T33 which are in contact with the terminals T12 and T13 of the light source unit, respectively. The connection point between the resistor R32 and the terminal T32 is connected to the OP-terminal of the control circuit 40. The terminal T33 is connected to the ground potential via the resistor R31.

  The capacitor C4 is connected between the COMP terminal and the LGND terminal of the control circuit 40. The resistor R7 and the capacitor C5 are connected in series between the COMP terminal and the LGND terminal of the control circuit 40.

  Resistors R8 and R9 are connected in series between the coil L31 and the LGND terminal. The capacitor C6 and the resistor R10 are connected in series between the coil L31 and a connection point between the resistor R8 and the resistor R9. The connection points of the resistors R8, R9, and R10 are connected to the ABN terminal of the control circuit 40. Resistors R8 and R9 constitute a voltage detection circuit that outputs a step-down chopper circuit, and capacitor C6 and resistor R10 constitute a voltage change detection circuit that outputs a step-down chopper circuit.

  FIG. 2 is a block diagram showing a main configuration of the control circuit 40.

  The control circuit 40 may be realized, for example, as an IC (integrated circuit) circuit, a part of the configuration may be provided outside the IC, or all the configurations may be configured by analog circuits. The control circuit 40 includes a PFC control circuit 41, a lighting control circuit 42, a protection circuit 43, a power circuit 44, an error amplifier 45, and a monitoring circuit 46. However, some or all of the circuits included in the control circuit 40 may be individually configured. In addition, a part of processing performed in each circuit included in the control circuit 40 can be realized by software processing using a computer.

  Prior to describing the function of each circuit included in the control circuit 40, a terminal having an input function among the terminals included in the control circuit 40 will be described. The corresponding terminals are the MULT terminal, ZCD terminal, CS terminal, VS terminal, VB terminal, VFB terminal, VDC terminal, OCP terminal, COMP terminal, OP-terminal and ABN terminal.

  The MULT terminal is a terminal for monitoring the input voltage to the power factor correction circuit 20.

  The potential of the ZCD terminal changes according to the voltage induced in the coil L23. And it detects that the electric current of the coil L21 became zero by detecting the voltage of L23 induced by the electric current which flows into the coil L21 with a ZCD terminal.

  The potential of the CS terminal changes according to the current flowing between the drain and source of the first switching element Q21. That is, the CS terminal is a terminal for monitoring the magnitude of the current.

  The potential of the VS terminal is a terminal for determining the reference potential of the HO terminal and the VB terminal.

  The VB terminal is a power supply terminal for generating a voltage at the HO terminal, and the power is supplied from the Vcc terminal via the diode D2. The voltage generated by the coil L22 is supplied to the VB terminal via the resistor R1, the capacitor C2, and the diode D1. The voltage supplied from the Vcc terminal is supplied based on, for example, a voltage generated by a coil (not shown) magnetically coupled to the coil L31 of the step-down chopper circuit 30.

  The VFB terminal has a potential corresponding to the output voltage VDC of the power factor correction circuit 20. That is, the VF terminal is a terminal for monitoring the magnitude of the voltage VDC.

  The VDC terminal is a terminal for taking in the voltage VDC as the operating voltage of the control circuit 40.

  The potential of the OCP terminal is a potential corresponding to the current flowing through the resistor R31. The current flowing through the resistor R31 is the current flowing through the light emitting diode D11. That is, the OCP terminal is a terminal for monitoring the magnitude of the current supplied to the light emitting diode D11, and is used for overcurrent protection in this embodiment.

  The COMP terminal is a terminal for charging the capacitors C4 and C5 as will be described later. The COMP terminal is a terminal for taking in a voltage generated by the discharge from the capacitors C4 and C5.

  The potential of the OP− terminal is a voltage corresponding to a voltage drop based on the current flowing through the light emitting diode D11 and the resistor R11, and is a potential difference generated between the terminals T12 and T13. The magnitude of the resistance value of the resistor R11 is set according to the load of the light emitting diode D11, that is, set according to the current value to be passed, and the power source is set so that the value of OP− matches the preset target value. The output current of the device 2 is feedback controlled. When the terminal T12 of the light source unit 1 is not in contact with the terminal T32, the detection voltage is not input to the OP-terminal. Further, when the value of OP− does not match the target value for a certain period of time, an abnormality of the power supply device 2 is estimated. Therefore, in the present embodiment, the OP-terminal is also used as a terminal for monitoring whether or not the light source unit 1 is normally mounted and whether the power supply device 2 is abnormal.

  The ABN terminal receives an output corresponding to a change amount or potential of a voltage supplied from the step-down chopper circuit 30 to the light source unit 1. The amount of change is detected by a voltage dividing circuit as a voltage detection circuit formed by the resistors R8 and R9 and a differentiation circuit as a voltage change detection circuit formed by the capacitor C6 and the resistor R10. That is, the ABN terminal is a terminal for monitoring the amount of change per certain time of the voltage supplied from the step-down chopper circuit 30 to the light source unit 1.

  Now, the PFC control circuit 41 performs self-oscillation control by turning on / off the first switching element Q21 based on the respective potentials of the MULT terminal, ZCD terminal, COMP terminal, CS terminal, and VFB terminal. Since the existing process can be used for the process for this control, the detailed description is abbreviate | omitted. The first switching signal is a high-frequency signal of about 40 to 50 kHz, for example.

  The lighting control circuit 42 uses a voltage between the VB terminal and the VS terminal to generate a switching signal (hereinafter referred to as a second switching signal) for turning on / off the second switching element Q31. The lighting control circuit 42 performs feedback control for chopping in the step-down chopper circuit 30 so that the potential of the OP− terminal matches the reference potential of OP +, that is, the current flowing through the light emitting diode D11 is constant. A second switching signal is generated. Thus, the lighting control circuit 42 corresponds to a signal generation circuit.

  The protection circuit 43 normally has a VDC terminal connected to the power supply circuit 44. The protection circuit 43 cuts off the connection between the VDC terminal and the power supply circuit 44 under the control of the monitoring circuit 46.

  The power supply circuit 46 generates a dropper power supply using the voltage VDC taken from the VDC terminal when the control circuit 46 is started up. The dropper power supply generated by using the voltage VDC supplies an operating voltage for operating each circuit in the control circuit 40 for a certain period of time from the start-up and the voltage Vcc. Further, the power supply circuit 46 is configured to secure an arbitrary power supply (not shown) from the power supply device 2, and after the dropper power supply has timed out, an operating voltage for operating each circuit from the arbitrary power supply, and a voltage Vcc is generated.

  The error amplifier 45 is a differential amplifier, and the reference value OP + is input to the non-inverting input terminal, and the OP− terminal is connected to the inverting input terminal. The error amplifier 45 outputs a voltage having a magnitude corresponding to the difference in the potential of the OP− terminal with respect to the reference value OP +. The output of the error amplifier 45 is input to the lighting control circuit 44 and the monitoring circuit 46.

  The monitoring circuit 46 monitors the abnormality of the lighting device 100 based on the voltage output from the error amplifier 45 and the potential of the ABN terminal. The monitoring circuit 46 controls the protection circuit 43 so as to stop the output from the GD terminal when an abnormality is detected.

  Next, operation | movement of the illuminating device 100 comprised as mentioned above is demonstrated.

(Operation in steady operating conditions)
First, the operation in a steady operation state will be described.

  In a steady operation state, the power factor correction circuit 20 performs step-up chopping so that the voltage VDC is set to a predetermined target voltage while performing phase compensation. This is realized by the PFC control circuit 41 supplying the first switching signal to the gate of the first switching element Q21. The PFC control circuit 41 includes a voltage supplied to the power factor correction circuit 20, a difference between the voltage VDC and its target value, an upper limit value of a current set according to a current flowing through the switching element Q21, and a current flowing through the coil L21. By adjusting the first switching signal at the timing when becomes zero, etc., boost chopping is controlled by a well-known self-excited oscillation method. The target voltage is set to 400V, for example. The PFC control circuit 41 obtains a voltage corresponding to the difference between the potential of the VFB terminal and a predetermined reference potential by an error amplifier (not shown), and adjusts the frequency and duty ratio of the first switching signal. Add to the feedback. However, the voltage fluctuation is reduced by putting the voltage obtained by the error amplifier in and out of the CR circuit formed by the resistor R7 and the capacitors C4 and C5. Accordingly, the PFC control circuit 41 adjusts the response speed of feedback to prevent an oscillation phenomenon.

  The monitoring circuit 46 does not operate the protection circuit 43 in a situation where an abnormality described later does not occur.

  In the steady operation state, the step-down chopper circuit 30 steps down the voltage supplied from the power factor correction circuit 20, and the current flowing through the light-emitting diode D11 is large enough to cause the light-emitting diode D11 to emit light with appropriate intensity. Step-down chopping to be constant at This is realized by supplying the second switching signal generated by the lighting control circuit 42 to the gate of the second switching element Q31. The lighting control circuit 42 sets the second switching signal so that the magnitude of the current flowing through the light emitting diode D11 is close to an appropriate magnitude for causing the light emitting diode D11 to emit light with an intensity corresponding to the set value of the emission intensity. Adjust the frequency and duty ratio.

  At this time, power for operating the lighting control circuit 42 is obtained by a bootstrap system. That is, when the second switching element Q31 is turned off while the second switching element Q31 is repeatedly turned on / off, the regenerative current of the coil L31 flows through the capacitor C31, the resistor R31, the diode D31, and the coil L32. . As a result, the potential of the VS terminal decreases to near the ground potential. At this time, the Vcc terminal generates the Vcc voltage with reference to the ground potential, and the voltage Vcc output from the Vcc terminal can be supplied to the VB terminal. Further, when the voltage supplied from the coil L22 via the resistor R1, the capacitor C2, and the diode D1 is supplied to the VB terminal and the voltage Vcc output from the Vcc terminal is not supplied to the VB terminal, the voltage is VF. Supplied to the terminal. In this way, power can always be supplied to the VB terminal.

(Operation at start-up)
Next, the operation at the start of the lighting device 100 will be described.

  FIG. 3 is a diagram illustrating the time change of the voltage VDC and the operation of the selection circuit 43 when the lighting apparatus 100 is started.

  When the illumination device 100 is not operating, both the first switching element Q21 and the second switching element Q31 are in the off state. When the DC power obtained by the rectifier circuit 10 and the capacitor C1 is supplied to the power factor correction circuit 20, the voltage VDC first shows the voltage of the DC power. When this voltage VDC is supplied to the power supply circuit 44, the power supply circuit 44 generates a dropper power supply for a certain period of time, whereby the other circuits of the control circuit 40 are started.

  The PFS control circuit 41 monitors the potential of the VFB terminal, and outputs the first switching signal from the terminal GD if the voltage VDC is less than the protection threshold set larger than the target voltage. As a result, the first switching signal is supplied to the first switching element Q21, and the first switching element Q21 is repeatedly turned on / off for boost chopping. Then, voltage VDC gradually increases as shown in FIG. The target voltage and the protection threshold value may be arbitrarily determined by, for example, the designer of the lighting device 100, the power supply device 2, or the control circuit 40. However, the protection threshold is set as a value slightly larger than the target voltage.

  At this time, the step-down chopper circuit 30 has not been started yet. That is, no bootstrap operation is performed. However, when the first switching element Q21 is on, a current is generated in the coil L21, so that a voltage is induced in the coil L21. The voltage is rectified by a rectifier circuit formed by the resistor R1, the capacitor C2, and the diode D1, and then applied to the VB terminal, whereby the capacitor C3 is charged. Thus, the transformer Tr21, the resistor R1, the capacitor C2, and the diode D1 function as a charging unit that charges the capacitor C3 using the current flow to the first switching element Q21.

In FIG. 3, the voltage VDC has reached the protection threshold at time T1.
As described above, when the voltage VDC is equal to or higher than the protection threshold, the PFC control circuit 41 stops outputting the second switching signal. Thereby, the first switching element Q21 is turned off.

  In FIG. 3, since the output of the second switching signal is stopped, the voltage VDC starts to decrease after some overshoot occurs. At time T2, the voltage VDC is less than the target voltage. As described above, when the voltage VDC becomes less than the target voltage, the PFC control circuit 41 resumes outputting the first switching signal. Note that the PFC control circuit 41 may resume the output of the first switching signal when the voltage VDC becomes less than the restart threshold value set separately from the target voltage. The restart threshold value corresponds to the second threshold value, and may be arbitrarily determined by the designer of the lighting device 100, the power supply device 2, or the control circuit 40, for example. However, the restart threshold value is preferably set as a value equal to or smaller than the protection threshold value, and more preferably as a value smaller than the protection threshold value. The restart threshold is typically set to a value equal to or lower than the target voltage.

In this manner, the first switching element Q21 is continuously turned off during a period from when the voltage VDC is equal to or higher than the protection threshold to when it is lower than the target voltage (hereinafter referred to as an overshoot period).
In FIG. 3, since the voltage VDC subsequently converges to the target voltage without exceeding the protection threshold, the PFC control circuit 41 continues to output the first switching signal.

  Now, the lighting control circuit 42 starts to operate slightly after the overshoot occurs in the voltage VDC. That is, the lighting control circuit 42 may be started when the first switching element Q21 is in an off state because of the overshoot period.

  At this time, since the step-down chopper circuit 30 stops operating, the second switching element Q31 is in an OFF state, and no regenerative current is generated. For this reason, the potential of the source of the second switching element Q31, that is, the potential of the VS terminal is indefinite. That is, the second switching element Q31 cannot be turned on unless a potential having a specified potential difference (hereinafter referred to as a starting potential) is generated at the gate.

  However, at this time, since the chopping operation in the power factor correction circuit 20 is stopped, no voltage is induced in the coil L22, and the voltage required by the lighting control circuit 42 to set the potential of the HO terminal as the starting potential is set. It cannot be obtained from the coil L22.

  On the other hand, a voltage obtained by adding the voltage across the capacitor C3 to the voltage Vcc is input between the VB terminal and the VS terminal.

  In addition, as the capacitor C3, the voltage between the VB terminal and the VS terminal is maintained at the voltage required by the lighting control circuit 42 to set the potential of the HO terminal as the starting potential over the entire overshoot period. An element having a capacity capable of accumulating as much charge as possible is used. Further, the transformer Tr21 is configured so that a voltage required to charge the capacitor C3 with the amount of charge can be induced in the coil L22 after the lighting device 100 is started and before the overshoot period. Since the voltage induced in the coil L22 is proportional to the ratio of the number of turns of the coil L22 to the number of turns of the coil L21 when the current of the coil L21 is constant, the voltage necessary for the charging can be induced by the ratio. Determine as follows.

  Thus, the voltage required by the control circuit 40 in order to set the potential of the HO terminal as the starting potential throughout the entire overshoot period is always input to the VB terminal. Therefore, the lighting control circuit 42 can use the voltage between the VB terminal and the VS terminal to set the potential of the HO terminal as the starting potential, and can turn on the second switching element Q31. Thus, the power supply circuit 44 and the circuit formed by the transformer Tr21, the resistor R1, the capacitor C2, the diode D1 and the capacitor C3 are used to calculate the lighting control circuit 42 from the output voltage of the power factor correction circuit 20 and the charge stored in the capacitor C3. Thus, a power generation circuit for generating the operating power is formed.

  On the other hand, the period from when the voltage VDC corresponding to the first output voltage becomes equal to or higher than the protection threshold value corresponding to the first threshold value to become less than the target voltage corresponding to the second threshold value corresponds to the overshoot period. . With the above operation, during the overshoot period, the voltage VDC is lowered and the first switching element Q21 is turned off. Thus, the PFC control circuit 41 that realizes the above operation realizes a function as a control circuit for the above control.

  That is, according to the power supply device 2, the step-down chopper circuit 30 can be reliably started even if the chopping operation in the power factor correction circuit 20 is continued during the overshoot period.

(Abnormality monitoring operation)
The monitoring circuit 46 monitors the potential at the ABN terminal. As described above, the voltage at the ABN terminal represents the change amount or voltage value of the voltage supplied from the step-down chopper circuit 30 to the light source unit 1 per certain time. The monitoring circuit 46 determines that there is an abnormality when the amount of change is equal to or greater than a predetermined amount. For example, the monitoring circuit 46 determines that there is an abnormality when the voltage supplied from the step-down chopper circuit 30 to the light source unit 1 fluctuates sharply, such as when the load is dropped. Also, when the voltage at the ABN terminal becomes equal to or higher than a predetermined voltage value, it is determined as abnormal. That is, as shown in FIG. 4, when the vertical axis represents time and the vertical axis represents the output voltage value of the step-down chopper circuit 30, the voltage is greater than or equal to the threshold value Vth1 or greater than or equal to the slope Vth2 (the area indicated by the slanted line in the figure). Is determined to be abnormal.

  The monitoring circuit 46 monitors the voltage output from the error amplifier 45. As described above, the error amplifier 45 outputs a voltage having a magnitude corresponding to the difference in the potential of the OP− terminal with respect to the reference value OP +. The potential of the OP-terminal is a potential corresponding to the load of the light emitting diode D11 when the light source unit 1 is correctly mounted, and the detected voltage when the light source unit 1 is not correctly mounted. Not entered. That is, the voltage output from the error amplifier 45 is low when the potential of the OP− terminal is larger than that of the OP + terminal, and is maximum (High) when the light source unit 1 is not correctly attached. Therefore, the monitoring circuit 46 determines that an abnormality occurs when the voltage output from the error amplifier 45 is equal to or higher than a predetermined voltage, or when the High or Low state continues for a certain time. For example, when high continues, it is assumed that the light source unit 1 is not correctly mounted or that the input to the OP-terminal is missing. If Low continues, a failure of the second switching element Q31 of the step-down chopper circuit 30 is estimated. Therefore, the monitoring circuit 46 determines that these are abnormal.

  If the monitoring circuit 46 determines that there is an abnormality, the monitoring circuit 46 operates the protection circuit 43 to cut off the supply of the voltage VDC to the power supply circuit 44. Thereby, the supply of the operating voltage from the power supply circuit 44 to each part in the control circuit 40 is stopped, and the operations of the power factor correction circuit 20 and the step-down chopper circuit 30 are also stopped.

  This embodiment can be variously modified as follows.

  The capacitor C3 is shared for bootstrap operation and for starting the step-down chopper circuit 30, but a separate capacitor may be provided for each application. Further, the bootstrap system may not be used for switching of the step-down chopper circuit 30.

  The power supply device 2 may be used to supply power to a load of a different type from the light source unit 1. That is, the power supply device 2 may be incorporated in a device of a different type from the lighting device 100 or may be realized as an independent device.

  Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

  DESCRIPTION OF SYMBOLS 1 ... Light source unit, 2 ... Power supply device, 10 ... Rectifier circuit, 20 ... Power factor improvement circuit, 30 ... Step-down chopper circuit, 40 ... Control circuit, 41 ... PFC control circuit, 42 ... Lighting control circuit, 43 ... Protection circuit, 44 ... power supply circuit, 45 ... error amplifier, 46 ... monitoring circuit, 100 ... lighting device, 200 ... external power supply, C1, C2, C3, C4, C5, C6, C31 ... capacitor, C21 ... electrolytic capacitor, D1, D2, D31 ... Diode, D11 ... Light emitting diode, L21, L22, L23, L31 ... Coil, Q21 ... First switching element, Q31 ... Second switching element, R1, R2, R3, R4, R5, R6, R7, R8 , R9, R10, R11, R21, R31, R32 ... resistors, Tr21 ... transformer.

Claims (4)

A power factor correction circuit including a first switching element for chopping and outputting a first output voltage;
A step-down chopper for stepping down the first output voltage, comprising, as a second switching element for chopping, an element capable of turning on / off the conduction between the input end and the output end due to a potential difference between the control end and the output end; ;
A signal generation circuit for generating a switching signal to be supplied to the control terminal for chopping by the step-down chopper;
The first output voltage is determined in advance except for an overshoot period from when the first output voltage becomes equal to or higher than a predetermined first threshold value to less than a predetermined second threshold value. A control circuit for controlling the first switching element so as to approach the target voltage, and for turning off the first switching element during the overshoot period;
When the step-down chopper stops chopping, charging means is provided for charging using the flow of current to the first switching element, and the first switching element is derived from the charge stored in the charging means. A power generation circuit that continuously generates operating power of the signal generation circuit over the entire period of the off-state;
A power supply device comprising:   The signal generation circuit includes a pair of terminals for receiving supply of the operating power, and a withstand voltage between the pair of terminals is a voltage applied between electrodes of the capacitor when the charging unit charges the capacitor. The power supply device according to claim 1 which is the above.   3. The power supply device according to claim 1, wherein the power generation circuit charges the capacitor during a period in which the second switching element is off when the step-down chopper is executing chopping. A power supply device according to any one of claims 1 to 3;
A light emitting element that emits light by a voltage obtained by stepping down the first output voltage with the step-down chopper;
A lighting device comprising: