JP6804993B2 - Power supply device and lighting device equipped with this power supply device - Google Patents

Description

An embodiment of the present invention relates to a power supply device and a lighting device including the power supply device.

There is known a power supply device that obtains a desired power by stepping up a voltage supplied from the outside and then stepping down the voltage. The boosting is for improving the power factor, and a power factor improving circuit is used in the power supply device. The step-down is to adjust the voltage for constant current control, and a step-down chopper circuit is used in the power supply device.

The step-down chopper circuit generally uses a field-effect transistor (FET) as a switching element for chopping. The field effect transistor turns on or off the conduction between the drain and the source, which are the input terminals, by the potential difference between the gate, which is the control terminal, and the source, which is the output terminal.

In a step-down chopper circuit using this field effect transistor as a switching element, a bootstrap method is widely applied as a method of supplying a drive power source for the switching element. In the case of a step-down chopper circuit, a diode is connected between the source terminal of the switching element and ground in order to generate a regenerative current when the switching element is off. The diode is connected in a direction that blocks the current flowing from the source terminal to the ground. Therefore, when the step-down chopper circuit is not operating, the potential of the source terminal of the switching element is indefinite. In order to activate the switching element, it is necessary to supply a voltage equal to or higher than a certain value based on the potential of the source terminal to the control terminal. However, if the potential of the source terminal is indefinite, the drive power supply for the switching element cannot be sufficiently secured from the bootstrap circuit, the start-up becomes unstable, and there is a concern that the step-down chopper circuit does not start stably.

Therefore, conventionally, there is a technique for stably starting a switching element by short-circuiting the source terminal of the switching element with the ground at the time of starting and setting the potential of the source terminal as the ground potential.

On the other hand, in this type of power supply device, when an overvoltage of a DC voltage converted by a step-down chopper circuit and output to a load is detected, switching of a switching element is stopped to suppress the overvoltage. For example, when the load attached to the power supply device is removed, the output voltage may rise and become overvoltage. In such a case, since the above-mentioned protection function works, it is possible to prevent the circuit from being destroyed by the overvoltage.

Japanese Patent No. 3775240

However, the output voltage does not drop immediately even if the switching of the switching element is stopped. The output voltage gradually decreases according to the attenuation characteristics of the output capacitor. Therefore, if the load is reattached before the output voltage is completely reduced, an inrush current flows through the load. For example, if the load is a light emitting load using a light emitting diode, the light emitting diode may fail due to the above inrush current. In order to deal with such a problem, it is necessary to add more circuit parts, which hinders the miniaturization and cost reduction of the power supply device.

The problem to be solved by the embodiment of the present invention is a highly reliable power supply device capable of realizing stable starting of a step-down chopper circuit and a protection function against overvoltage without hindering miniaturization and cost reduction. And to provide a lighting device equipped with this power supply.

In one embodiment, the power supply includes a step-down chopper circuit, a short circuit, a control circuit, and a monitoring circuit. In the step-down chopper circuit, a series circuit of an inductor and a capacitor is connected between the output terminal of the switching element and the ground, and the input voltage is applied to the load by switching the switching element with both ends of the capacitor as feed terminals to the load. It is converted into an output voltage according to the above and supplied to the load connected to the power feeding terminal. The short-circuit circuit is connected in parallel with the capacitor, and draws the potential of the connection point between the inductor and the capacitor into the potential of the ground during operation. The control circuit operates the short-circuit circuit before starting the switching control of the switching element, and after the switching of the switching element is stopped, drives the short-circuit circuit to set the potential of the connection point to the ground. Pull into the potential . The monitoring circuit monitors the output voltage, and operates the short-circuit circuit when an abnormality in the output voltage is detected. The protection circuit stops the switching of the switching element when an abnormality is detected in the monitoring circuit.

In one embodiment, the lighting device includes the above power supply device and a light emitting load connected to the power supply terminal of the power supply device and controlled to be lit.

According to one embodiment, it is possible to realize a stable start of the step-down chopper circuit and a protection function against overvoltage without hindering miniaturization and cost reduction, and it is possible to provide a highly reliable power supply device. ..

According to one embodiment, it is possible to realize a stable start of the step-down chopper circuit of the power supply device and a protection function against overvoltage without hindering the miniaturization and cost reduction of the power supply device, and the lighting is highly reliable. Equipment can be provided.

The schematic electric circuit block diagram of the lighting apparatus provided with the power supply device which concerns on this embodiment. The block diagram which shows the main part structure of the control circuit in FIG. The flow chart which shows the operation sequence at the time of power-on of the control circuit in FIG. The flow chart which shows the operation sequence at the time of abnormality detection of the control circuit in FIG.

Hereinafter, embodiments will be described with reference to the drawings.
FIG. 1 is an electric circuit configuration diagram of a lighting device 100 including a power supply device 2 according to the present embodiment. Note that FIG. 1 shows a schematic circuit configuration, and some of the various elements provided in the actual circuit configuration are not shown.

The lighting device 100 includes a light source unit 1 and a power supply device 2. The light source unit 1 is a light emitting load whose lighting is controlled by the power supply device 2, and is detachable from the power supply device 2. The power supply device 2 is fixedly provided in the main body of the lighting device 100.

The light source unit 1 includes a plurality of light emitting diodes (LEDs) D11 and a resistor R11. A plurality of light emitting diodes D11 are connected in series. Although not shown, the light source unit 1 is also connected to a resistance element in parallel with the light emitting diode D11. The resistor R11 is connected to the current output end of the series circuit of the light emitting diode D11. The light source unit 1 is detachably attached to the power supply device 2 at the current input end and the current output end in the series circuit of the light emitting diode D11 and at the end not connected to the light emitting diode D11 of the resistor R11, respectively. Terminals T11, T12, and T13 are provided.

The number of light emitting diodes D11 is arbitrary. The light source unit 1 may be provided with only one light emitting diode D11. Further, a plurality of series circuits of the light emitting diode D11 as shown in FIG. 1 may be connected in parallel. 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 power supply device 2 receives power from an external power source 200 such as a commercial power source, and generates DC power for causing the light emitting diode D11 of the light source unit 1 connected as a load to emit light. Then, the power supply device 2 supplies the generated DC power to the light source unit 1 mounted on the power supply terminals T31, T32, and T33 to control the lighting.

The power supply device 2 includes a rectifier circuit 10, a power factor improving circuit 20, a step-down chopper circuit 30, a control circuit 40, and a mounting detection circuit 50. Further, the power supply device 2 includes various circuit elements of capacitors C1, C2, C3, C4, C5, resistors R1, R2, R3, R4, R5, R6, R7, R8, R9, R101, R102 and a diode D1.

The pair of input ends of the rectifier circuit 10 are connected to the two power supply terminals T21 and T22, respectively. Two power supply lines connected to an external power source 200 such as a commercial power source are connected to the two power supply terminals T21 and T22, respectively. Through this connection, AC power is supplied from the external power supply 200 to the pair of input ends of the rectifier circuit 10. The rectifier circuit 10 rectifies AC power and outputs DC power. The DC power output by the rectifier circuit 10 between the pair of output ends is smoothed by the capacitor C1 and then supplied to the power factor improving circuit 20. One end of the capacitor C1 is connected to one of the output ends of the rectifier circuit 10, and the other end is connected to the ground which is the reference potential of the main circuit. Since the capacitance of the capacitor C1 is about several μF, the voltage across this is a pulsating voltage obtained by full-wave rectifying a sine wave.

The power factor improving circuit 20 boosts the DC power smoothed by the capacitor C1 in order to improve the power factor. The power factor improvement circuit 20 is also referred to as a PFC (power factor correction) circuit. The power factor improving circuit 20 includes a transformer Tr21, a switching element Q21, an electrolytic capacitor C21, a diode D21, and resistors R21 and 22.

The transformer Tr21 includes a coil L21 on the primary side and a coil L22 on the secondary side. In the transformer Tr21, the input end of the coil L21 on the primary side is connected to one end of the capacitor C1, and the output end is connected to the anode of the diode D21. In the transformer Tr21, the input end of the coil L22 on the secondary side is connected to the ground, and the output end is connected to one end of the resistor R22. One end of the resistor R22 is connected to the output end of the coil L22, and the other end is connected to the ZCD terminal of the control circuit 40.

The switching element Q21 is an N-channel field effect transistor (FET). In the switching element Q21, the drain terminal is connected to the connection point between the output end of the coil L21 and the anode of the diode D21, the source terminal is connected to one end of the resistor R21 and the CS terminal of the control circuit 40, and the gate terminal is connected. It is connected to the GD terminal of the control circuit 40. One end of the resistor R21 is connected to the source terminal of the switching element Q21, and the other end is connected to the ground. In the diode D21, the anode is connected to the connection point between the other end of the coil L21 and the drain terminal of the switching element Q21, and the cathode is connected to one end of the electrolytic capacitor C21. One end of the electrolytic capacitor C21 is connected to the cathode of the diode D21, and the other end is connected to the ground E. Both terminals of the electrolytic capacitor C21 serve as output terminals of the power factor improving circuit 20.

By such a connection, a series circuit of the diode D21 and the electrolytic capacitor C21 is formed between the drain terminal and the source terminal of the switching element Q21. On the other hand, the switching element Q21 conducts when the gate signal applied to the gate terminal is turned on, and forms a closed circuit including the capacitor C1, the coil L21, and the resistor R21. Further, the switching element Q21 is opened when the gate signal applied to the gate terminal is turned off, and the closed circuit is cut off. As a result, the electrolytic capacitor C21 is charged by the voltage charged in the capacitor C1 when the switching element Q21 is in the cutoff state, and is discharged when it is in the conductive state. Thus, the power factor improving circuit 20 boosts the DC voltage rectified by the rectifying circuit 10 by the switching operation of the switching element Q21, obtains a predetermined DC voltage, and outputs the DC voltage to the step-down chopper circuit 30.

The step-down chopper circuit 30 includes a switching element Q31, an inductor L31 for storing power, a capacitor C31 for output, a diode D31 for regeneration, and resistors R31 and R32. The switching element Q31 is an N-channel field effect transistor (FET). The switching element Q31 connects the drain terminal to one end of the electrolytic capacitor C21 which is one output terminal of the power factor improving circuit 20, and connects the source terminal to the connection point between the input end of the inductor L31 and the cathode of the diode D31. The gate terminal is connected to the HO terminal of the control circuit 40. The inductor L31 has an input end connected to the source terminal of the switching element Q31 and an output end connected to one end of the capacitor C31. One end of the capacitor C31 is connected to the output end of the inductor L31, and the other end is connected to one end of the resistor R31. One end of the resistor R31 is connected to the other end of the capacitor C31, and the other end is connected to the anode of the diode D31. In the diode D31, the cathode is connected to the connection point between the source terminal of the switching element Q31 and the inductor, and the anode is connected to the ground.

The step-down chopper circuit 30 connects both ends of the capacitor C31 to the power supply terminals T31, T32 and T33 of the power supply device 2. Specifically, in the step-down chopper circuit 30, the side connected to the output end of the inductor L31 of the capacitor C31 is connected to the feeding terminal T31, and the side connected to the resistor R31 of the capacitor C31 is connected to the feeding terminal T33. You are connected. Further, the side of the capacitor C31 connected to the resistor R31 is connected to the power supply terminal T32 via the resistor R32.

Incidentally, when the light source unit 1 as a load is connected to the power supply device 2, the terminal T11 of the light source unit 1 is connected to the power supply terminal T31, and the terminal T12 of the light source unit 1 is connected to the power supply terminal T32. The terminal T13 of the light source unit 1 is connected to T33. The terminal T11 is a current input terminal of the light source unit 1. The terminal T12 is a current output terminal of the light source unit 1.

Through such a connection, the switching element Q31 conducts when the gate signal applied to the gate terminal is turned on, and guides the output current of the power factor improving circuit 20 to the inductor L31. The switching element Q31 is opened when the gate signal applied to the gate terminal is turned off, and cuts off the output current of the power factor improving circuit 20. The inductor L31 stores the DC power when the switching element Q31 is turned on and a DC voltage is applied, and releases the stored DC power when the switching element Q31 is turned off and the DC voltage is no longer applied. The DC power discharged from the inductor L31 is smoothed by the capacitor C31 and supplied to a load connected to the feeding terminals T31, T32, and T33, for example, the light source unit 1.

The mounting detection circuit 50 includes a diode D51 and resistors R51, R52, R53 and R54. In the mounting detection circuit 50, one end of the resistor R54 is connected to the VC2 terminal of the control circuit 40, the other end is connected to the anode of the diode D51, and the cathode of the diode D51 is connected to the power supply terminal T31 of the power supply device 2. .. Further, in the mounting detection circuit 50, a series resistance circuit R51-R52 is formed by the resistor R51 and the resistor R52, one end of the series resistance circuit R51-R52 is connected to the anode of the diode D51, and the other end is connected to the ground. doing. Therefore, the series resistance circuits R51-R52 are connected in parallel with the capacitor C31 of the step-down chopper circuit 30.

The mounting detection circuit 50 connects one end of the resistor R53 to the midpoint of the series resistance circuits R51-R52, and connects the other end of the resistor R53 to the Lamp terminal of the control circuit 40. Here, the mounting detection circuit 50 determines whether or not a load is connected to the power supply terminals T31, T32, and T33 of the power supply device 2 due to a change in the voltage divided by the resistance ratio of the series resistance circuits R51-R52. It is a circuit for making it possible to judge by.

The control circuit 40 is composed of an analog IC (Integrated Circuit). The control circuit 40 has a MULT terminal, a GD terminal, a ZCD terminal, a CS terminal, a Vcc terminal, a VS terminal, a HO terminal, a VB terminal, a VFB terminal, a VDC terminal, an OCP terminal, and a VC2 terminal as external terminals for connecting to the outside. It has an LGND terminal, a Vref terminal, an OP + terminal, an OP- terminal, an ABN terminal, a Lamp terminal, a DISin terminal, and a DIS terminal. Needless to say, the external terminals of the control circuit 40 are not limited to the above terminals.

The MULT terminal is connected to the midpoint of the series resistance circuits R1-R2 formed by the resistor R1 and the resistor R2. The series resistance circuits R1-R2 are connected between both terminals of the capacitor C1. Due to this connection, the potential of the MULT terminal depends on the voltage obtained by dividing the output voltage of the capacitor C1 by the resistance ratio of the series resistance circuits R1-R2. The control circuit 40 detects the input voltage to the power factor improving circuit 20 from the potential of the MULT terminal.

The GD terminal is connected to the gate terminal of the switching element Q21. The control circuit 40 generates a gate signal of the switching element Q21. Then, the control circuit 40 outputs a gate-on or gate-off gate signal from the GD terminal to the gate terminal of the switching element Q21.

The ZCD terminal is connected to the output end of the coil L22 via the resistor R22. The coil L22 supplies the ZCD terminal with a potential corresponding to the amount of change in the current flowing through the coil L21. The control circuit 40 detects the timing at which the current flowing through the coil L21 on the primary side of the transformer Tr21 becomes zero from the potential of the ZCD terminal, and generates a trigger signal for turning on the switching element Q21.

The CS terminal is connected to the source terminal of the switching element Q21. The potential of the CS terminal depends on the current flowing between the drain and the source of the switching element Q21. The control circuit 40 detects the current flowing through the switching element Q21, the so-called switching current, from the potential of the CS terminal.

The Vcc terminal is connected to the anode of the diode D1. The cathode of the diode D1 is connected to the VB terminal and one end of the bootstrap capacitor C2. The other end of the capacitor C2 is connected to the VS terminal and also to the source terminal of the switching element Q31. The control circuit 40 applies a predetermined circuit operating voltage Vcc to the Vcc terminal. When the potential of this circuit operating voltage Vcc is higher than the potential of the source terminal of the switching element Q31, the capacitor C2 is charged. The control circuit 40 detects the potential on one end side of the capacitor C2 (the side connected to the cathode of the diode D1) from the VB terminal, and is connected from the VS terminal to the other end side of the capacitor C2 (the source terminal of the switching element Q31). Detects the potential of the side).

The HO terminal is connected to the gate terminal of the switching element Q31. The control circuit 40 generates a gate signal of the switching element Q31 based on the potential difference between both ends of the capacitor C2. Then, the control circuit 40 outputs a gate-on or gate-off gate signal from the HO terminal to the gate terminal of the switching element Q31.

The VFB terminal is connected to the midpoint of the series resistance circuit R3-R4 formed by the resistor R3 and the resistor R4. The series resistance circuit R3-R4 is connected between both terminals of the capacitor C21. Due to this connection, the potential of the VFB terminal depends on the voltage obtained by dividing the output voltage of the capacitor C21 by the resistance ratio of the series resistance circuits R3-R4. The control circuit 40 detects the amount of change in the DC voltage output from the power factor improving circuit 20 to the step-down chopper circuit 30 from the VFB terminal per fixed time.

The VDC terminal is connected to the connection point between the cathode of the diode D21 in the power factor improving circuit 20 and the drain terminal of the switching element Q31 in the step-down chopper circuit 30. By this connection, a high voltage output from the power factor improving circuit 20 is applied to the VDC terminal. The control circuit 40 generates a circuit operating voltage Vcc or the like from a high voltage applied to the VDC terminal by a drover method.

The OCP terminal is connected to the connection point between the capacitor C31 of the step-down chopper circuit 30 and the resistor R31 via the resistor R5. The potential of the OCP terminal depends on the current flowing through the resistor R31. The current flowing through the resistor R31 is the current flowing through the step-down chopper circuit 30. The control circuit 40 detects the current flowing through the step-down chopper circuit 30 from the potential of the OCP terminal.

The VC2 terminal is connected to the ground via the capacitor C3. Further, the VC2 terminal is connected to the power supply terminal T31 of the power supply device 2 via the resistor R54 and the diode D51. By this connection, a voltage obtained by dividing the potential of the VC2 terminal, that is, the potential corresponding to the charging voltage of the capacitor C3, is applied between the power supply terminal T31 and the power supply terminal T33 of the power supply device 2.

The LGND terminal is connected to the ground.
The Vref terminal is connected to the ground via a parallel circuit of the series resistance circuit R101-R102 formed by the resistor R101 and the resistor R102 and the capacitor C4. The OP + terminal is connected to the midpoint of the series resistance circuits R101-R102. The OP + terminal is also connected to the ground via the capacitor C5. With these connections, the potential of the OP + terminal becomes the potential of the reference voltage determined by the resistance voltage division of the resistors R101 and R102.

The OP-terminal is connected to the power supply terminal T32 of the power supply device 2 via the resistor R9. The potential of the OP-terminal depends on the current flowing through the combined resistance of the resistors R11, R31, and R32. The current flowing through the combined resistance of the resistors R11, R31, and R32 is the current flowing through the feeding terminal T31, that is, the current flowing through the diode D11 of the light source unit 1 when the light source unit 1 which is a load is attached to the power supply device 2. .. The control circuit 40 detects the current flowing through the diode D11 of the light source unit 1, the so-called load current, from the potential of the OP-terminal.

The ABN terminal is connected to the midpoint of the series resistance circuit R7-R8 formed by the resistor R7 and the resistor R8. The series resistance circuit R7-R8 is connected between the connection point between the inductor L31 of the step-down chopper circuit 30 and the capacitor C31 and the ground. That is, the series resistance circuits R7-R8 are connected in parallel with the capacitor C31. With this connection, the potential of the ABN terminal depends on the potential obtained by dividing the DC voltage supplied from the step-down chopper circuit 30 to the load by the resistance ratio of the series resistance circuits R7-R8. The control circuit 40 detects the voltage supplied from the step-down chopper circuit 30 to the light source unit 1 based on the potential of the ABN terminal.

The Lamp terminal is connected to the midpoint of the series resistance circuits R51-R52 via the resistor R53. The series resistance circuit R51-R52 is connected between the power supply terminal T31 and the power supply terminal T33 of the power supply device 2 via a diode D51 for preventing backflow. Due to this connection, the potential of the Lamp terminal depends on the voltage obtained by dividing the voltage corresponding to the potential difference between the power supply terminal T31 and the power supply terminal T33 of the power supply device 2 by the resistance ratio of the series resistance circuits R51-R52. When a load including a resistance element is connected between the power supply terminal T31 and the power supply terminal T33, a current flows through the load and the voltage between the power supply terminal T31 and the power supply terminal T33 drops. There is no voltage drop if no load is connected. The control circuit 40 detects a voltage drop between the power supply terminal T31 and the power supply output terminal T33 from the potential of the Lamp terminal.

The DISin terminal is open. The DISin terminal is used, for example, when a semiconductor element is connected to the outside of the control circuit 40.

The DIS terminal is connected to the connection point between the inductor L31 and the capacitor C31 of the step-down chopper circuit 30 via the resistor R6. A switch is built in between the DIS terminal of the control circuit 40 and the GND, and the control circuit 40 controls the switch on and off. When the switch between the DIS terminal and the GND is turned on, the voltage of the capacitor C31 is discharged via the resistor R6, and the connection point potential between the inductor L31 and the capacitor C31 drops to approximately the GND potential.
Although the resistor R6 can be omitted, it is connected to suppress the discharge current of the capacitor C31 and to relieve the stress on the switch built in between the DIS terminal and the GND. The GND is the reference potential of the control circuit 40, and is connected to the ground which is the reference potential of the main circuit via the LGND terminal.

FIG. 2 is a block diagram showing a main configuration of the control circuit 40.
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 operational amplifier 45, a monitoring circuit 46, a determination circuit 47, and a start circuit 48. In the control circuit 40, each circuit 41 to 48 is composed of an analog circuit. The control circuit 40 may include at least a part of each of the circuits 41 to 48 as a digital circuit, and at least a part of the processing performed by each of the circuits 41 to 48 may be realized by software processing using a computer.

The PFC control circuit 41 generates a gate signal for turning on / off the switching element Q21 based on the potentials of the MULT terminal, the ZCD terminal, the CS terminal, and the VFB terminal. Then, the PFC control circuit 41 controls the operation of the power factor improving circuit 20 by outputting a gate signal from the GD terminal to the gate terminal of the switching element Q21 to turn on / off the switching element Q21. Since the control of the power factor improving circuit 20 by the PFC control circuit 41 and the operation of the power factor improving circuit 20 by the control are well known, the description thereof is omitted here.

The lighting control circuit 42 generates a gate signal for turning on / off the switching element Q31 based on the potentials of the VS terminal and the VB terminal, respectively. Further, the lighting control circuit 42 determines the frequency and duty ratio of the gate signal based on the voltage signal output from the operational amplifier 45. Then, the lighting control circuit 42 controls the operation of the step-down chopper circuit 30 by outputting a gate signal from the HO terminal to the gate terminal of the switching element Q31 to turn on / off the switching element Q31. Since the control of the step-down chopper circuit 30 by the lighting control circuit 42 and the operation of the step-down chopper circuit 30 by the control are well known, the description thereof is omitted here.

The protection circuit 43 usually connects the VDC terminal to the power supply circuit 44. Further, the protection circuit 43 monitors the current flowing through the step-down chopper circuit 30 from the potential of the OCP terminal. Then, when a current abnormality such as an overcurrent is detected, the protection circuit 43 stops the operation of the PFC control circuit 41 and the lighting control circuit 42, and cuts off the connection between the VDC terminal and the power supply circuit 44. Further, the operation of the PFC control circuit 41 and the lighting control circuit 42 is stopped. Further, the protection circuit 43 can receive an abnormal signal from the monitoring circuit 46. Then, even when an abnormal signal is received, the protection circuit 43 stops the operation of the PFC control circuit 41 and the lighting control circuit 42, and cuts off the connection between the VDC terminal and the power supply circuit 44.

The power supply circuit 44 generates a circuit operating voltage Vcc or the like from a high-voltage full-wave rectified voltage taken in via a VDC terminal prior to starting the control circuit 40 by a drover method. Then, the power supply circuit 44 applies the circuit operating voltage Vcc to the Vcc terminal. Further, the power supply circuit 44 appropriately applies a drover voltage including a circuit operating voltage Vcc to another circuit.

The operational amplifier 45 connects the positive electrode terminal (+) to the OP + terminal, the negative electrode terminal (−) to the OP− terminal, and the output terminal to the lighting control circuit 42 and the monitoring circuit 46. The operational amplifier 45 outputs a voltage signal having a magnitude corresponding to the difference between the potential of the OP- terminal and the potential of the OP + terminal to the lighting control circuit 42 and the monitoring circuit 46. As described above, the lighting control circuit 42 adjusts the switching frequency and duty ratio of the switching element Q31 according to the voltage signal from the operational amplifier 45. In this adjustment, the output current of the step-down chopper circuit 30 is feedback-controlled so that the load current corresponding to the potential of the OP-terminal matches the target current corresponding to the potential of the OP + terminal. Here, the operational amplifier 45 functions as an error amplifier. Further, since the light emitting diode has a constant voltage characteristic, the output voltage is increased or decreased by controlling the output current.

The monitoring circuit 46 monitors whether or not the load current is normal from the voltage signal output from the operational amplifier 45. Further, the monitoring circuit 46 monitors whether or not the output voltage of the step-down chopper circuit 30 is normal from the potential of the ABN terminal. When an abnormality in the load current or output voltage is detected, the monitoring circuit 46 outputs an abnormality signal to the protection circuit 43 and the start circuit 48.

The determination circuit 47 monitors the potential of the Lamp terminal, that is, the midpoint potential of the series resistance circuits R51-R52. When no load is attached to the power supply device 2, the voltage applied from the VC2 terminal and the voltage determined by the VF of the resistors R7, R8, R51, R52, R54 and the diode D51 are applied to the Lamp terminal. When a load is mounted on the power supply device 2, a resistor connected in parallel with the light emitting diode D11 of the light source unit 1 which is the load is connected in parallel with the series resistance circuits R7 to R8, so that the resistor is connected to the Lamp terminal. Is applied with a lower voltage than when no load is attached. Detecting this voltage difference, the determination circuit 47 determines that the power supply device 2 is loaded. Then, when it is determined that the power supply device 2 is loaded with a load, the determination circuit 47 outputs a start signal to the start circuit 48.

The start circuit 48 includes a switching element Q48. The switching element Q48 is an N-channel field effect transistor (FET). In the switching element Q48, the drain terminal is connected to the DIS terminal and the source terminal is connected to the GND. Further, the switching element Q48 connects the gate terminal to the output end of the start signal output from the determination circuit 47 and the output end of the abnormal signal output from the monitoring circuit 46, respectively. When a start signal or an abnormal signal is input to the gate terminal, the switching element Q48 conducts conduction and drops the potential of the DIS terminal to the ground potential. Here, the switching element Q48 constitutes a short-circuit circuit that draws the potential of the connection point between the inductor L31 and the capacitor C31 into the ground potential.

When the determination circuit 47 determines that the power supply device 2 is loaded, a start signal is output to the PFC control circuit 41, the lighting control circuit 42, the protection circuit 43, and the monitoring circuit 46. The start signal resets the PFC control circuit 41, the lighting control circuit 42, the protection circuit 43, and the monitoring circuit 46.

Further, the start circuit 48 short-circuits the gate terminal of the switching element Q48 and the DISin terminal of the control circuit 40. Due to this short circuit, the DISin terminal outputs a signal supplied to the gate terminal of the switching element Q48, that is, an activation signal or an abnormality signal. Therefore, when, for example, the base terminal of an N-channel field effect transistor (FET) is connected to the DISin terminal, the field effect transistor operates in the same manner as the switching element Q48.

The circuit operating voltage is applied from the power supply circuit 44 to the PFC control circuit 41, the lighting control circuit 42, the protection circuit 43, and the monitoring circuit 46, but is not applied to the determination circuit 47 and the start-up circuit 48. In the determination circuit 47 and the start circuit 48, the power supply line is connected to the VC2 terminal, and the voltage generated at the VC2 terminal is used as the circuit operating voltage. Therefore, the determination circuit 47 and the start circuit 48 can operate even before the circuit operating voltage Vcc or the like is generated from the high voltage full-wave rectified voltage taken in by the power supply circuit 44 via the VDC terminal.

Next, the main operation sequence of the control circuit 40 will be described with reference to FIGS. 3 and 4.
FIG. 3 is a flow chart showing an operation sequence of the control circuit 40 when the power is turned on. When the external power supply 200 is turned on by turning on the power switch (not shown), the control circuit 40 starts the operation of the procedure shown in the flow chart of FIG.

First, the control circuit 40 confirms whether or not the light source unit 1 is mounted on the power supply device 2 as step ST1. That is, since the voltage generated at the VC2 terminal of the control circuit 40 by turning on the external power supply 200 is applied between the power supply terminal T31 and the power supply terminal T33 of the power supply device 2 via the resistor R54, the control circuit 40 determines. The circuit 47 monitors the potential of the Lamp terminal. The power supply terminals T31, T32, and T33 of the power supply device 2 are connected to the terminals T11, T12 of the light source unit 1. When T13 is mounted, a current flows through a resistance element (not shown) connected in parallel with the light emitting diode D11, and the voltage between the power supply terminal T31 and the power supply terminal T33 drops. Due to this voltage drop, the potential at the midpoint of the series resistance circuits R51-R52 connected between the power supply terminal T31 and the power supply terminal T33 fluctuates. The potential of the Lamp terminal depends on the midpoint potential of the series resistance circuits R51-R52. Therefore, by monitoring the potential of the Lamp terminal by the determination circuit 47, the control circuit 40 can confirm whether or not the light source unit 1 is mounted on the power supply device 2.

The voltage applied between the feeding terminal T31 and the feeding terminal T33 via the resistor, that is, the voltage generated at the VC2 terminal of the control circuit 40 is set to be equal to or lower than the forward voltage of the light emitting diode D11. By doing so, it is possible to prevent a problem that the light emitting diode D11 lights up just by attaching the light source unit 1 to the power supply device 2.

When the light source unit 1 is not mounted on the power supply device 2 (NO in step ST1), the control circuit 40 continues the monitoring operation in step ST1.
When the light source unit 1 is attached to the power supply device 2 or when it is confirmed that the light source unit 1 is attached (YES in step ST1), the control circuit 40 turns on the start circuit 48 as step ST2. That is, in the control circuit 40, when the determination circuit 47 confirms that the light source unit 1 is attached, the determination circuit 47 outputs a start signal to the start circuit 48. By this start signal, the switching element Q48 is conducted in the start circuit 48. Therefore, when the determination circuit 47 outputs the start signal to the start circuit 48, the control circuit 40 can turn on the start circuit 48.

When the switching element Q48 of the start circuit 48 becomes conductive, the potential of the DIS terminal of the control circuit 40 becomes the ground potential. When the potential of the DIS terminal reaches the ground potential, the potential at the connection point between the inductor L31 of the step-down chopper circuit 30 and the capacitor C31 is drawn to the ground potential. As a result, it is equivalent to short-circuiting the source terminal of the switching element Q31 to the ground.

Therefore, the control circuit 40 starts the switching operation of the switching element Q21 of the power factor improving circuit 20 in step ST3, and then starts the switching of the switching element Q31 of the step-down chopper circuit 30 in step ST4. That is, in the control circuit 40, when the determination circuit 47 determines that the power supply device 2 is loaded, a start signal is output from the start circuit 48 to the PFC control circuit 41, the lighting control circuit 42, the protection circuit 43, and the monitoring circuit 46. .. With this start signal, the PFC control circuit 41 generates a gate signal for the switching element Q21, and outputs the generated gate signal from the GD terminal to the switching element Q21 of the power factor improving circuit 20. Thus, the switching element Q21 starts the switching operation. Therefore, when the PFC control circuit 41 starts the control operation, the control circuit 40 can start the switching operation of the switching element Q21.

Similarly, the lighting control circuit 42 generates a gate signal for the switching element Q31 by the start signal, and outputs the generated gate signal from the HO terminal to the switching element Q31 of the step-down chopper circuit 30. Thus, the switching element Q31 starts the switching operation. Therefore, when the lighting control circuit 42 starts the control operation, the control circuit 40 can start the switching operation of the switching element Q31.

Here, before the control circuit 40 turns on the start circuit 48, the source potential of the switching element Q31 is indefinite. However, at the time of step ST4 when the lighting control circuit 42 starts operation, the start circuit 48 is turned on in step ST2 and the source potential of the switching element Q31 is lowered to the ground potential, so that the drive power supply is supplied by the bootstrap circuit. You can secure enough. Therefore, the switching element Q31 can be stably started by controlling the lighting control circuit 42. That is, the step-down chopper circuit 30 can be started stably. The switching element Q48 of the start circuit 48 opens immediately before the step-down chopper circuit 30 starts.

After that, the control circuit 40 performs constant current control as step ST5. That is, in the control circuit 40, the lighting control circuit 42 sets the switching frequency of the switching element Q31 according to the voltage signal of the operational amplifier 45 so that the load current input to the OP- terminal becomes the target constant current input to the OP + terminal. And the duty ratio. By repeating this adjustment, the load current approaches the target constant current. Therefore, the control circuit 40 can perform constant current control by performing feedback control using the operational amplifier 45 as an error amplifier.

Next, the operation sequence when the control circuit 40 detects an abnormality while the constant current control is being performed will be described with reference to the flow chart of FIG.
First, while the constant current control is being performed, the control circuit 40 determines the presence or absence of an abnormality in step ST11. That is, the monitoring circuit 46 activated by the activation signal from the activation circuit 48 monitors whether or not the load current is normal from the voltage signal output from the operational amplifier 45. Then, for example, when the load current exceeds the preset upper limit threshold value or the lower limit threshold value, the monitoring circuit 46 determines that there is an abnormality. Therefore, the control circuit 40 can determine the presence or absence of an abnormality by monitoring the load current by the monitoring circuit 46. If there is no abnormality (NO in step ST11), the control circuit 40 continues to determine whether or not there is an abnormality.

If there is an abnormality (YES in step ST11), the control circuit 40 operates the protection circuit 43 as step ST12. That is, in the control circuit 40, when the monitoring circuit 46 determines that there is an abnormality, the monitoring circuit 46 also outputs an abnormality signal to the protection circuit 43. Upon receiving the abnormal signal, the protection circuit 43 cuts off the connection between the VDC terminal and the power supply circuit 44. Further, the protection circuit 43 stops the operation of the PFC control circuit 41 and the lighting control circuit 42. That is, the switching of the switching elements Q21 and Q31 is stopped. Therefore, when the monitoring circuit 46 outputs an abnormal signal to the protection circuit 43, the control circuit 40 can operate the protection circuit 43.

The control circuit 40 turns on the start circuit 48 as step ST13. That is, in the control circuit 40, when the monitoring circuit 46 determines that there is an abnormality, the monitoring circuit 46 also outputs an abnormality signal to the activation circuit 48. Due to this abnormal signal, the switching element Q48 of the start circuit 48 becomes conductive after the operation of the lighting control circuit 42 is stopped, that is, after the switching of the switching element Q31 is stopped. Therefore, when the monitoring circuit 46 outputs an abnormal signal to the start circuit 48, the control circuit 40 can turn on the start circuit 48, that is, operate the short circuit (switching element Q48). At the time when the start circuit 48 conducts the switching element Q48, the connection between the VDC terminal and the power supply circuit 44 is cut off, and the VCS supply is cut off, so that the monitoring circuit 46 has stopped operating. However, although not shown, since the starting circuit 48 has a function of holding the signal of the monitoring circuit 46, the starting circuit 48 can control the switching element Q48 on / off even if the monitoring circuit 46 is stopped. ..

When the switching element Q48 of the start circuit 48 conducts, the potential of the DIS terminal of the control circuit 40 becomes the ground potential as described above, and the potential of the connection point between the inductor L31 and the capacitor C31 of the step-down chopper circuit 30 reaches the ground potential. Be drawn in.

For example, if the light source unit 1 is removed from the power supply device 2 while constant current control is being performed, the output voltage of the power supply device 2 is opened until the protection circuit 43 stops the operation of the lighting control circuit 42. As the voltage rises, the voltage of the capacitor C31 also rises accordingly. Then, this voltage decreases over time according to the attenuation characteristics until the electric charge of the capacitor C31 is completely removed. Here, if the light source unit 1 is reattached while the voltage is low, an inrush current may flow to the light source unit 1 side and the light emitting diode D11 may fail.

In the present embodiment, when the monitoring circuit 46 determines that there is an abnormality, the connection point between the inductor L31 and the capacitor C31 of the step-down chopper circuit 30 is short-circuited to the ground by the action of the start circuit 48. Therefore, since the electric charge charged in the capacitor C31 becomes zero momentarily, the inrush current does not flow to the light source unit 1 side even if the light source unit 1 is reattached. Therefore, there is no possibility that the light emitting diode D11 of the light source unit 1 will fail due to the inrush current.

By the way, when the switching element Q48 included in the start-up circuit 48 conducts by an abnormal signal from the monitoring circuit 46, it draws out the electric charge charged in the capacitor C31, so that it draws out the electric charge when the capacitor C31 is fully charged. An element that has the ability to withstand the above (current resistance characteristics) is required. Conversely, by determining the capacity of the switching element Q48 according to the capacitance of the capacitor C31 and incorporating it into the start circuit 48, it is possible to eliminate the waste of using a high-capacity (high-priced) switching element.

On the other hand, depending on the performance of the light source unit 1 to be fed, the capacity of the capacitor C31 may have to be larger than the current state. For example, when the light source unit 1 having a flat waveform by increasing the smoothness of the current flowing through the light emitting diode is targeted for control, it is necessary to increase the capacitance of the capacitor C31. When the capacitance of the capacitor C31 is increased, it is necessary to change the switching element Q48 to a high-capacity one having a large withstand current characteristic. However, since the switching element Q48 is incorporated in the control circuit 40 which is made into an IC, if it is changed, the control circuit 40 itself must be remade.

In this regard, the power supply device 2 of the present embodiment short-circuits the gate terminal of the switching element Q48 and the DISin terminal which is an external terminal of the control circuit 40. Therefore, a switching element having a capacity suitable for the capacitance of the capacitor C31 is externally attached to the control circuit 40, and the gate terminal of this switching element is connected to the DISin terminal. Further, the drain terminal of this switching element is connected to the DIS terminal, and the source terminal is connected to the ground. By doing so, a switching element having high capacity can be used as a switching element for short circuit without changing the current control circuit 40.

As described in detail above, the power supply device 2 of one embodiment includes a step-down chopper circuit 30, a short-circuit circuit (switching element Q48), a control circuit 40, and a monitoring circuit 46. The short-circuit circuit is connected in parallel with the capacitor C31 of the step-down chopper circuit 30 and is configured to draw the potential of the connection point between the inductor L31 of the step-down chopper circuit 30 and the capacitor C31 into the ground potential during operation. On the other hand, the control circuit 40 is configured to operate the short-circuit circuit before starting the switching control of the switching element Q31 of the step-down chopper circuit 30. Further, the monitoring circuit 46 monitors the output voltage supplied from the step-down chopper circuit 30 to the light source unit 1 (load) from the potential of the ABN terminal, and operates the short-circuit circuit when an abnormality in the output voltage such as an overvoltage is detected. It is configured as follows.

Therefore, according to the power supply device 2, the potential at the connection point between the inductor L31 and the capacitor C31 of the step-down chopper circuit 30 is drawn into the ground potential before the switching control of the switching element Q31 is started, so that the step-down chopper circuit 30 is used. It can be started stably. Further, even when an abnormality such as an overvoltage of the voltage output to the light source unit 11 occurs, the potential of the connection point between the inductor L31 and the capacitor C31 of the step-down chopper circuit 30 is drawn into the ground potential. Therefore, since the capacitor 31 is immediately discharged and the remaining capacity is reduced, there is no danger that an inrush current will flow into the light source unit 1 even if the light source unit 1 once removed is reattached.
As described above, according to the power supply device 2, stable starting of the step-down chopper circuit 30 and a protection function against overvoltage can be realized by using one short-circuit circuit in combination. Therefore, since circuit components can be saved, it is possible to provide a highly reliable power supply device 2 without hindering miniaturization and cost reduction.
Moreover, in the power supply device 2, the short circuit is composed of the switching element Q48. Therefore, the determination circuit 47 and the monitoring circuit 46 of the control circuit 40 can operate the short-circuit circuit only by outputting the gate signal for conducting the switching element Q48, so that the circuit components can be saved from this point as well. it can.

Further, the power supply device 2 includes a protection circuit 43 that stops switching of the switching elements Q21 and Q31 of the power factor improving circuit 20 and the step-down chopper circuit 30 when an abnormality is detected in the monitoring circuit 46. Therefore, when an abnormality in the output voltage is detected, the power conversion action performed in the power factor improving circuit 20 and the step-down chopper circuit 30 is stopped, so that the safety of the power supply device 2 can be further enhanced.

Further, in the power supply device 2, the control circuit 40 is composed of an integrated circuit, and the integrated circuit includes an external terminal for outputting a signal for conducting the switching element Q48 of the short-circuit circuit, that is, a DISin terminal. Therefore, according to the power supply device 2, for example, even if there is a design change in which the capacitance of the capacitor C31 of the step-down chopper circuit 30 must be increased, a switching element suitable for the capacitance of the capacitor C31 has the same function as the switching element Q48. It can be externally attached to the control circuit 40 so as to have it. As a result, excellent effects such as cost saving due to design change and shortening of design period can be achieved.

On the other hand, the lighting device 100 formed by connecting the light source unit 1 to the power supply terminals T31, T32, and T33 of the power supply device 2 described above does not hinder the miniaturization and cost reduction of the power supply device 2 and protects against overvoltage. The step-down chopper circuit 30 of the power supply device 2 can be started stably while exhibiting the function. Therefore, the reliability of the lighting device 100 can be improved.

The present invention is not limited to the above-described embodiment as it is, and at the implementation stage, the components can be modified and embodied within a range that does not deviate from the gist thereof.

For example, in the above-described embodiment, the switching element Q48 as a short-circuit circuit is composed of a field-effect transistor, but a switching element other than the field-effect transistor may be applied.

Further, in the above embodiment, the start circuit 48 including the short circuit is provided in the control circuit 40, but the start circuit 48 including the short circuit may be provided outside the control circuit 40. Alternatively, a short-circuit circuit may be provided outside the control circuit 40, and a start-up circuit 48 other than the short-circuit circuit may be provided inside the control circuit 40.

Further, in the above embodiment, the load is the light source unit 1, but the power supply device 2 may be used to supply DC power to a load other than the light source unit 1.
Further, in the above embodiment, the load (light source unit 1) is detachable from the power supply device 2, but the load may be fixedly attached to the power supply device 2. In this case, the mounting detection circuit 50 of FIG. 1 can be omitted. If omitted, the control circuit 40, instead of the determination circuit 47, operates the short-circuit circuit before starting the switching control of the switching element Q31.

In addition, various inventions can be formed by an appropriate combination of the plurality of components disclosed in the embodiment. For example, some components may be removed from all the components shown in the embodiments. In addition, components from different embodiments may be combined.

1 ... light source unit, 2 ... power supply, 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 ... operational amplifier, 46 ... monitoring circuit, 47 ... judgment circuit, 48 ... start circuit, 50 ... mounting detection circuit.

Claims (4)

A series circuit of an inductor and a capacitor is connected between the output terminal of the switching element and the ground, and both ends of the capacitor are used as power supply terminals for the load, and the input voltage is set according to the load by switching the switching element. With a step-down chopper circuit that converts to and supplies to the load connected to the power supply terminal;
A short-circuit circuit that is connected in parallel with the capacitor and draws the potential of the connection point between the inductor and the capacitor into the potential of the ground during operation;
With a control circuit that operates the short-circuit circuit before starting switching control of the switching element;
With a monitoring circuit that monitors the output voltage and operates the short-circuit circuit when an abnormality in the output voltage is detected;
A protection circuit that stops switching of the switching element when an abnormality is detected in the monitoring circuit;
A power supply device, characterized in that, after the switching of the switching element is stopped, the short-circuit circuit is driven to draw the potential of the connection point to the potential of the ground . The short circuit includes a switching element that connects the connection point between the inductor and the capacitor to the ground when conducting;
The control circuit and the monitoring circuit operate the short-circuit circuit by outputting a signal for conducting the switching element of the short-circuit circuit to the short-circuit circuit;
The power supply device according to claim 1 . The control circuit is composed of integrated circuits;
The integrated circuit includes an external terminal for outputting a signal for conducting the switching element of the short-circuit circuit;
The power supply device according to claim 2 . With the power supply device according to any one of claims 1 to 3 .
With a light emitting load that is connected to the power supply terminal of this power supply and controlled to light up;
Lighting device equipped with.