JP6658193B2 - Power supply device and lighting device provided with the power supply device - Google Patents

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, a voltage supplied from the outside is boosted by a boost chopper having a power factor improvement function. 2. Description of the Related Art There is known a power supply device that obtains desired power by stepping down by a step-down chopper after boosting .

  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 and off conduction between a drain and a source by a potential difference between a gate and a 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 at the ground may be used. In this case, since the potential of the source of the FET is undefined, it is necessary to devise the potential supplied to the gate.

  When the power supply device is started, first, the operation of the step-up chopper is started, and thereafter, the operation of the step-down chopper is started. Then, the step-down chopper generates a voltage to be supplied to the control terminal of the switching element by using a voltage obtained by the operation of the step-up chopper. For this reason, depending on the operation state of the boost 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 normally performed. Could not be started.

JP 2015-185450 A

  It is an object of the present invention 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 according to the embodiment includes a power factor improvement circuit, a step-down chopper, a signal generation circuit, a control circuit, and a power generation circuit. The power factor improvement circuit outputs a first output voltage. The step-down chopper is configured to connect a high potential of the first output voltage to the input terminal, and to chop an element capable of turning on / off conduction between the input terminal and the output terminal by a potential difference between the control terminal and the output terminal. 2 as a second switching element to reduce the first output voltage. The signal generation circuit generates a switching signal to be supplied to the control terminal for chopping by the step-down chopper. The control circuit sets the first output voltage in advance during an overshoot period from when the first output voltage becomes equal to or higher than the predetermined first threshold to when it becomes lower than the predetermined second threshold. The first switching element is controlled to approach a predetermined target voltage, and the first switching element is turned off during the overshoot period. When the step-down chopper stops chopping, the power generation circuit includes charging means for charging using a current flow to the first switching element, and the first switching element is converted from the charge stored by the charging means. Generates operating power of the signal generation circuit for setting the potential of the control terminal to a starting potential for turning on the second switching element over the entire period in which the device is in the off state.

  According to the present invention, it is possible 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.

FIG. 2 is a diagram illustrating an electric circuit configuration of the lighting device according to the embodiment. FIG. 2 is a block diagram illustrating a main configuration of a control circuit in FIG. 1. FIG. 3 is a diagram illustrating a voltage VDC and a time change of an operation of the PFC control circuit in FIG. 2 when the lighting device illustrated in FIG. 1 is started. FIG. 4 is an explanatory diagram of an abnormality monitoring operation according to one embodiment.

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

(Constitution)
FIG. 1 is a diagram showing 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 various elements provided in an actual circuit configuration is omitted.

  The lighting 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 in the main body.

  The light source unit 1 includes a plurality of light emitting diodes (LEDs) D11 as light sources and a resistor R11. The plurality of light emitting diodes D11 are connected in series. The resistor R11 is connected to a current output terminal in the series circuit of the light emitting diode D11. The number of the light emitting diodes D11 is arbitrary. Only one light emitting diode D11 may be provided. Further, a plurality of light emitting diodes D11 in series as shown in FIG. 1 may be connected in parallel. Terminals T11, T12, and T13 for connecting to the power supply 2 are respectively provided at the current input terminal and the current output terminal in the series circuit of the light emitting diode D11 and at 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) as a light source instead of the light emitting diode D11. 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 may not be 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 to cause the light emitting diode D11 to emit light. The power supply device 2 includes a rectifier circuit 10, a power factor improvement circuit 20, a step-down chopper circuit 30, a control circuit 40, capacitors C1, C2, C3, C4, C5, and C6, and resistors R1, R2, R3, R4, R5, and 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 supply 200 such as a commercial power supply are connected to the two terminals T21 and T22, respectively. As a result, AC power supplied from the external power supply 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 by the rectifier circuit 10 between the pair of output terminals of the rectifier circuit 10 is supplied to the power factor correction circuit 20 after being smoothed by the capacitor C1.

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

  The transformer Tr21 includes one coil L21 on the primary side and two coils L22 and L23 on the secondary side. The first terminal of the coil L21 is connected to one of the output terminals 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 this 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 is the voltage VDC output from the power factor correction circuit 20. The voltage VDC is supplied to the step-down chopper circuit 30 and 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 a 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 terminals of the rectifier circuit 10 and the ground. Thus, the resistors R2 and R3 form a voltage dividing circuit for dividing the potential difference between the potential of the output terminal of the rectifier circuit 10 and the ground potential, that is, the voltage supplied to the power factor correction circuit 20. The 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. Thus, the resistors R4 and R5 form a voltage dividing circuit that divides the potential difference between the potential of the second end of the coil L21 and the ground potential, that is, the voltage supplied from the power factor improving circuit 20 to the step-down chopper circuit 30. ing. The connection point between the resistors R4 and R5 is connected to the VFB terminal of the control circuit 40.

  The diode D2 has an anode and a cathode connected to the Vcc terminal and the VB terminal of the control circuit 40, respectively. Thus, the diode D2 allows the current output from the Vcc terminal of the control circuit 40 to pass to the VB terminal. Further, the diode D2 prevents backflow to the VS terminal.

  The capacitor C3 is connected to the VS terminal and the VB terminal of the control circuit 40, respectively. When the potential of the VB terminal is higher than the potential of the VS terminal, the capacitor C3 outputs 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. 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 used as a filter but need not be.

In this embodiment, an FET is used as the second switching element Q31. The drain of the second switching element Q31 is connected to the first terminal of the capacitor C21 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 terminal of the second switching element Q31, is connected to the HO terminal of the control circuit. The source as the output terminal 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 including 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, the coils L31 and L32, the diode D31, and the capacitor C31 form a step-down chopper. The resistor R31 is for detecting a current flowing through the light emitting diode D11, and generates a potential of 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.

  Both ends of the resistor R32 are respectively connected to terminals T32 and T33 that 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.

  The 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 point of the resistors R8, R9, R10 is connected to the ABN terminal of the control circuit 40. The resistors R8 and R9 constitute a voltage detection circuit of the output of the step-down chopper circuit, and the capacitor C6 and the resistor R10 constitute a voltage change detection circuit of the output of the step-down chopper circuit.

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

  The control circuit 40 may be realized as, for example, an IC (integrated circuit) circuit, a part of the configuration may be provided outside the IC, or the entire configuration may be configured by an analog circuit. The control circuit 40 includes a PFC control circuit 41, a lighting control circuit 42, a protection circuit 43, a power supply 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. Further, a part of the processing performed by each circuit included in the control circuit 40 can be realized by software processing using a computer.

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

  The MULT terminal is a terminal for monitoring an 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. Then, by detecting the voltage of L23 induced by the current flowing through the coil L21 at the ZCD terminal, it is detected that the current of the coil L21 has become zero.

  The potential of the CS terminal changes according to the current flowing between the drain and the 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 a reference potential of the HO terminal and the VB terminal.

  The VB terminal is a power 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 an operating voltage of the control circuit 40.

  The potential of the OCP terminal becomes 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 the present embodiment.

  The COMP terminal is a terminal that charges the capacitors C4 and C5 as described later. The COMP terminal is a terminal for taking in a voltage generated by discharging from the capacitors C4 and C5.

The potential at the OP− terminal is a voltage corresponding to a current flowing through the light emitting diode D11 and a voltage drop based on the resistor R11, and is a potential difference generated between the terminals T12 and T13. Set the size of the resistance value of the resistor R11 in accordance with the load of the light emitting diode D11, that is, is set in accordance with the current value to flow, so as to match a target value the value of OP- is preset The output current of the power supply device 2 is feedback-controlled. When the terminal T12 of the light source unit 1 is not in contact with the terminal T32, no detection voltage is input to the OP- terminal. If the value of OP- does not match the target value for a certain period of time, it is estimated that the power supply device 2 is abnormal. 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 properly mounted and for monitoring an abnormality of the power supply device 2.

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

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

  The lighting control circuit 42 uses the voltage between the VB terminal and the VS terminal to generate a switching signal for turning on / off the second switching element Q31 (hereinafter, referred to as a second switching signal). Note that the lighting control circuit 42 performs feedback control such 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 with respect to chopping in the step-down chopper circuit 30. Generate a second switching signal. 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 44 generates a dropper power supply using the voltage VDC taken from the VDC terminal when the protection circuit 43 starts up. Certain time dropper power supply launched generated using the voltage VDC, and supplies the operation voltage for operating the respective circuits in the control circuit 40, and a voltage Vcc. The power supply circuit 44 is configured to secure an arbitrary power supply (not shown) from the power supply device 2. After the timeout of the dropper power supply, an operation voltage for operating each circuit from the arbitrary power supply, and a voltage Vcc.

The error amplifier 45 is a differential amplifier. The reference value OP + is input to a 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 between the potential of the OP− terminal and the reference value OP +. The output of the error amplifier 45 is input to the lighting control circuit 42 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, the operation of the lighting device 100 configured as described above will be described.

(Operation in a steady operation state)
First, an 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 becomes 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 calculates the voltage supplied to the power factor correction circuit 20, the difference between the voltage VDC and its target value, the upper limit of the current set according to the current flowing through the switching element Q21, and the current flowing through the coil L21. By adjusting the first switching signal according to the timing at which the value becomes zero, boost chopping is controlled by a well-known self-excited oscillation method. Note that the target voltage is set to, for example, 400V. The PFC control circuit 41 obtains a voltage corresponding to a difference between the potential of the VFB terminal and a predetermined reference potential by an error amplifier (not shown) and adjusts the voltage to adjust the frequency and the duty ratio of the first switching signal. Add to your feedback. However, the voltage obtained by the above-described error amplifier is taken in and out of the CR circuit formed by the resistor R7 and the capacitors C4 and C5 to reduce the fluctuation of the voltage. Thus, the PFC control circuit 41 adjusts the response speed of the feedback to prevent the oscillation phenomenon.

  The monitoring circuit 46 does not operate the protection circuit 43 in a situation where no abnormality described later occurs.

  Further, in a steady operation state, the step-down chopper circuit 30 reduces the voltage supplied from the power factor correction circuit 20 while 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 so that it becomes constant. 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 controls the second switching signal so that the magnitude of the current flowing through the light emitting diode D11 approaches an appropriate magnitude for causing the light emitting diode D11 to emit light at an intensity corresponding to the set value of the emission intensity. Adjust frequency and duty ratio.

  At this time, power for operating the lighting control circuit 42 is obtained by a bootstrap method. 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, so that the voltage Vcc output from the Vcc terminal can be supplied to the VB terminal. 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 becomes VF. It is supplied to the terminal. Thus, power can always be supplied to the VB terminal.

(Operation at startup)
Next, the operation at the time of starting the lighting device 100 will be described.

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

  When the lighting device 100 is not operating, both the first switching element Q21 and the second switching element Q31 are off. 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 of the DC power first appears as the voltage VDC. When the 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 PFC control circuit 41 monitors the potential of the VFB terminal, and outputs the first switching signal from the terminal GD when the voltage VDC is lower than the target voltage and lower than the set protection threshold. As a result, the first switching signal is supplied to the first switching element Q21, and the first switching element Q21 repeats on / off for boost chopping. Then, voltage VDC gradually increases as shown in FIG. Note that the target voltage and the protection threshold may be arbitrarily determined by, for example, a 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, the bootstrap operation is not performed. However, when a current is generated in the coil L21 when the first switching element Q21 is on, a voltage is induced in the coil L21. This 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, thereby charging the capacitor C3. Thus, the transformer Tr21, the resistor R1, the capacitor C2, and the diode D1 function as charging means for charging the capacitor C3 using the current flow to the first switching element Q21.

Now, in FIG. 3, at time T1, the voltage VDC has reached the protection threshold.
When the voltage VDC becomes 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 a certain degree of overshoot occurs. Then, at time T2, the voltage VDC is lower than the target voltage. As described above, when the voltage VDC becomes lower than the target voltage, the PFC control circuit 41 restarts outputting the first switching signal. Note that the PFC control circuit 41 may restart the output of the first switching signal when the voltage VDC becomes lower than a restart threshold determined separately from the target voltage. The restart threshold corresponds to the second threshold, and may be arbitrarily determined by, for example, a designer of the lighting device 100, the power supply device 2, or the control circuit 40. However, the restart threshold is preferably set as a value equal to or smaller than the protection threshold, and more preferably as a value smaller than the protection threshold. The restart threshold is typically set to a value equal to or lower than the target voltage.

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

  The lighting control circuit 42 starts operating a little after the voltage VDC overshoots. That is, the lighting control circuit 42 may start when the first switching element Q21 is in the off state because of the overshoot period.

  At this time, since the step-down chopper circuit 30 has stopped operating, the second switching element Q31 is in the off state, and no regenerative current is generated. Therefore, the potential of the source of the second switching element Q31, that is, the potential of the VS terminal is undefined. That is, the second switching element Q31 cannot be turned on unless a potential (hereinafter, referred to as a starting potential) having a prescribed potential difference with respect to the indefinite potential is generated at the gate.

  However, at this time, since the chopping operation in the power factor correction circuit 20 has been 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 to the starting potential is set. Cannot be obtained from coil L22.

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

  Note that the capacitor C3 maintains the voltage between the VB terminal and the VS terminal at the voltage required by the lighting control circuit 42 for setting the potential of the HO terminal to the starting potential over the entire period of the overshoot period. An element having a capacity capable of accumulating as much charge as possible is used. In addition, the transformer Tr21 is configured so that a voltage required to charge the capacitor C3 with the above-described amount of charge can be induced in the coil L22 after the lighting device 100 is started and before the overshoot period. When the current of the coil L21 is constant, 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. It is determined as follows.

  Thus, the voltage required by the control circuit 40 for setting the potential of the HO terminal to the starting potential throughout the overshoot period is always input to the VB terminal. Therefore, by using the voltage between the VB terminal and the VS terminal, the lighting control circuit 42 can 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 determine the lighting control circuit 42 from the output voltage of the power factor correction circuit 20 and the charge stored in the capacitor C3. This means that a power generation circuit for generating the operating power of the above 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 to lower than the target voltage corresponding to the second threshold corresponds to the overshoot period. . By the above operation, during the overshoot period, the voltage VDC is reduced, 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, it is possible to reliably start the step-down chopper circuit 30 even if the power factor improvement circuit 20 continues the chopping operation during the overshoot period.

(Abnormality monitoring operation)
The monitoring circuit 46 monitors the potential of the ABN terminal. As described above, the voltage at the ABN terminal indicates the amount of change or the voltage value of the voltage supplied from the step-down chopper circuit 30 to the light source unit 1 per fixed time. Then, 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, for example, when the load is dropped. In addition, when the voltage of the ABN terminal becomes equal to or higher than a predetermined voltage value, it is determined that there is an abnormality. 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, a region where the voltage is equal to or more than the threshold value Vth1 or equal to or more than the gradient Vth2 (region indicated by oblique lines in FIG. 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 between the potential of the OP− terminal and the reference value OP +. The potential of the OP- terminal is a potential corresponding to the magnitude of the load of the light emitting diode D11 when the light source unit 1 is properly mounted, and the detection voltage is lower 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 higher than the OP + terminal, and is maximum (High) when the light source unit 1 is not properly mounted. Therefore, the monitoring circuit 46 determines that the error is abnormal 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 period of time. For example, when the high level continues, it is assumed that the light source unit 1 is not properly mounted or that the input to the OP- terminal is missing. If the Low continues, the 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.

  The monitoring circuit 46 activates the protection circuit 43 and shuts off the supply of the voltage VDC to the power supply circuit 44 when it is determined to be abnormal. As a result, the supply of the operating voltage from the power supply circuit 44 to each unit 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 implemented in the following various modifications.

  The capacitor C3 is commonly used for the bootstrap operation and for starting the step-down chopper circuit 30, but a separate capacitor may be provided for each application. Further, the bootstrap method 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 different type of load than 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 provided by way of example and are not intended to limit the scope of the invention. These new embodiments can be implemented in other various forms, and various omissions, replacements, and changes can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are also included in the invention described in the claims and their equivalents.
Hereinafter, the inventions described in the claims of the present application are appended.
[Supplementary Note 1] A power factor improving circuit including a first switching element for chopping and outputting a first output voltage;
A step-down chopper that includes, as a second switching element for chopping, an element that can turn on / off conduction between the input terminal and the output terminal by a potential difference between the control terminal and the output terminal, and that steps down the first output voltage; ;
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 set to a predetermined value except during an overshoot period from when the first output voltage is equal to or higher than a predetermined first threshold to when the first output voltage is lower than a predetermined second threshold. 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, the charging device includes a charging unit that uses a current flow to the first switching element to charge the first switching element. A power generation circuit that continuously generates operation power of the signal generation circuit over the entire period of the off-state.
[Supplementary Note 2] The signal generation circuit includes a pair of terminals for receiving the supply of the operating power, and a withstand voltage between the pair of terminals is determined by an electrode of the capacitor when the charging unit charges the capacitor. 2. The power supply according to claim 1, wherein the power supply is equal to or higher than a voltage applied therebetween.
[Supplementary Note 3] The power supply device according to Supplementary Note 1 or 2, wherein the power generation circuit charges the capacitor while the second switching element is off when the step-down chopper is performing chopping. .
[Supplementary Note 4] The power supply device according to any one of Supplementary Notes 1 to 3;
A light-emitting element that emits light at a voltage obtained by stepping down the first output voltage with the step-down chopper.

  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.

Claims (4)

A power factor improving circuit including a first switching element for chopping and outputting a first output voltage;
The high potential of the first output voltage is connected to the input terminal, a second for the chopping element which can conduct on / off of the output end and the input end by a potential difference between the output terminal and the control terminal A step-down chopper provided as a switching element for stepping down the first output voltage;
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 set to a predetermined value except during an overshoot period from when the first output voltage is equal to or higher than a predetermined first threshold to when the first output voltage is lower than a predetermined second threshold. 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, the charging device includes a charging unit that uses a current flow to the first switching element to charge the first switching element. A power generation circuit that continuously generates operation power of the signal generation circuit for setting the potential of the control terminal to a starting potential for turning on the second switching element over the entire period of the off state; Power supply device comprising: Said signal generating circuit includes a pair of terminals for receiving a supply of the operating power, and the breakdown voltage between the pair of terminals, the voltage applied between the electrodes of the capacitor when charging the charging means child capacitor The power supply device according to claim 1, which is as described above. Wherein the power generation circuit, when the step-down chopper is running chopping power supply according to claim 1 or claim 2 wherein the second switching element is the charging means during a period when turned off to charge the capacitor apparatus. A power supply device according to any one of claims 1 to 3, and
A light-emitting element that emits light at a voltage obtained by stepping down the first output voltage with the step-down chopper.