JP5374757B2 - Power supply device, LED device, and light source device - Google Patents

Description

  The present invention relates to a power supply device that supplies a voltage to an LED, and an LED device and a light source device including the power supply device.

  Compared with fluorescent lamps and other discharge lamps that have been used as light sources in the past, LEDs are attracting attention as light sources because of their low power consumption and long life, and comparisons of tens to hundreds of mA are possible. LEDs capable of flowing large currents are used not only in residential lighting equipment, but also in light sources such as lighting equipment for factories and offices, road lighting equipment, industrial lighting equipment, and display devices. It was.

  A power supply device that is used in such a light source device and supplies a voltage to an LED often uses a constant current power source to improve the efficiency of the device. In addition, a configuration in which a plurality of LEDs are connected in series has become mainstream in order to improve the efficiency of the power supply or reduce the cost.

  For example, the AC voltage is full-wave rectified, the full-wave rectified DC voltage is supplied to the high-frequency inverter circuit, and a desired voltage and current are supplied to a light source in which a plurality of LEDs are connected in series to the output side of the high-frequency inverter circuit. A power supply device (light emitting device) is disclosed (see Patent Document 1).

Japanese Patent Laid-Open No. 10-321914

  In a conventional power supply device as disclosed in Patent Document 1, a smoothing capacitor for removing ripples is often provided on the output side of a high-frequency inverter circuit in order to supply a stable voltage and current to an LED as a load. Moreover, in order to light many LEDs efficiently, when the structure which connects many LEDs in series is employ | adopted, it is necessary to make the output voltage of a power supply device high according to the number of LEDs.

  However, in the conventional power supply device, even if the input power supply (input voltage) is cut off during maintenance of the power supply device or a light source device using the power supply device (for example, a lighting device or a display device), the load Therefore, when the voltage of the smoothing capacitor provided on the output side of the power supply device is lower than the forward voltage of the LED, the electric charge stored in the smoothing capacitor is hardly consumed. For this reason, the voltage of the smoothing capacitor is maintained for a long time, and there is a risk of electric shock if the maintenance worker touches it by mistake. In particular, in the case of a load having a configuration in which a large number of LEDs are connected in series, the voltage maintained by the smoothing capacitor also increases. Although a configuration in which a resistor is connected in parallel to the smoothing capacitor may be employed, when an input voltage is applied, a current always flows through the resistor, which is not preferable from the viewpoint of suppressing power consumption.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a power supply device capable of enhancing the safety of maintenance work while suppressing power consumption, and an LED device and a light source device including the power supply device. And

According to a first aspect of the present invention, there is provided a power supply device including a voltage conversion unit that converts an input voltage into an output voltage, a capacitor provided in parallel on the output side of the voltage conversion unit, and a discharge having one end connected to the capacitor. A first transistor having a collector connected to the other end of the discharge resistor, a second transistor having a collector connected to the base of the first transistor, and an input voltage determination for determining the presence or absence of an input voltage And an output terminal of the input voltage determination circuit is connected to a base of the second transistor, and the first transistor is connected via the second transistor according to the determination by the input voltage determination circuit. and it controls the conduction and non-conduction of transistor, and wherein the Citea Rukoto to the discharge resistor to a connection or disconnection in parallel with the capacitor.

According to a second aspect of the present invention, there is provided a power supply device according to the first aspect , further comprising: a resistor connected between a base and a collector of the first transistor; and a Zener diode having a cathode connected to the base of the first transistor. Features.

Power supply according to the third invention, in the first invention, characterized in that it comprises connected multiple resistor between said first transistor base-collector and base-emitter of.

Power supply according to the fourth invention, in any one of the first invention to third invention, the input voltage determining circuit includes: a diode connected to an anode to an output end of said voltage conversion unit, to the cathode of the diode A parallel circuit of a connected resistor and a capacitor is provided, and the presence or absence of an input voltage is determined according to the presence or absence of the voltage of the capacitor.

Power supply apparatus according to a fifth invention, in any one of the first invention to third invention, the input voltage determining circuit includes a resistor the output voltage of the voltage converter is applied, the current flowing through the resistor The present invention is characterized in that the presence or absence of an input voltage is determined in accordance with the presence or absence of the input.

An LED device according to a sixth aspect of the invention includes the power supply device according to any one of the first to fifth inventions, and a series LED group to which a voltage is supplied by the power supply device.

A light source device according to a seventh aspect of the invention includes the power supply device according to any one of the first to fifth inventions, and a plurality of LEDs connected in series to which a voltage is supplied by the power supply device. And

  In the first invention, a capacitor provided in parallel on the output side of the voltage conversion unit, and a discharge circuit for discharging the charge of the capacitor when the voltage of the capacitor becomes lower than a predetermined value are provided. As a load, it can be set as the some LED (series LED group) connected in series, for example. In this case, the capacitor is connected in parallel with the plurality of LEDs. For example, when the input voltage is applied and the output voltage of the voltage converter is supplied to a plurality of LEDs connected in series, the voltage of the capacitor is a predetermined value (for example, the total value of forward voltages of the LEDs). ) It will never be lower and the discharge circuit will not work. In addition, for example, when the input voltage is cut off and the voltage of the capacitor becomes lower than a predetermined value (for example, the total value of the forward voltage of each of the plurality of LEDs), the discharge circuit is activated to discharge the capacitor charge. To do. This prevents unnecessary power consumption when the input voltage is applied, and discharges and lowers the capacitor charge when the input voltage is interrupted. Even if touched by mistake, it is possible to prevent an electric shock and improve the safety of maintenance work.

In addition , an input voltage determination circuit for determining the presence or absence of the input voltage is provided, and when the input voltage determination circuit determines that there is no input voltage, the discharge circuit discharges the capacitor. When the input voltage is cut off, the output voltage converted by the voltage conversion unit decreases, and the voltage of the capacitor also decreases. When the voltage of the capacitor becomes lower than the total value of the forward voltages of each of the plurality of LEDs, no current flows through each LED, so that the charge stored in the capacitor is maintained. By discharging the charge of the capacitor with the discharge circuit, the voltage of the capacitor can be lowered to a safe value or less, and the safety of maintenance work can be improved.

The discharge circuit includes a discharge resistor connected in parallel to the capacitor, and further includes a switch circuit connected in series with the discharge resistor. When the input voltage determination circuit determines that there is no input voltage, the switch circuit connects the discharging resistor in parallel with the capacitor. Thereby, since the electric charge stored in the capacitor is discharged through the discharging resistor, the voltage of the capacitor can be lowered to a safe value or less, and the safety of maintenance work can be improved. The switch circuit includes a first transistor connected in series with the discharging resistor, and a second transistor for controlling conduction and non-conduction of the first transistor according to the determination by the input voltage determination circuit And a series circuit of a resistor and a Zener diode for applying a bias voltage to the first transistor. If it is determined that there is an input voltage, the second transistor turns off the first transistor. Thus, the first transistor prevents the discharging resistor from being connected in parallel with the capacitor. If it is determined that there is no input voltage, the second transistor makes the first transistor conductive. As a result, the first transistor connects the discharging resistor in parallel with the capacitor.

In the second aspect, a bias voltage is applied to the first transistor in series circuit of the resistor and Zener diode. For example, a voltage divided by a series circuit of a resistor and a Zener diode is applied to the base of the first transistor as a bias voltage. Thereby, since the bias voltage of the first transistor becomes a constant voltage by the voltage of the Zener diode, the first transistor can be operated by a constant current operation, and it is possible to suppress the discharge current from becoming steep and to reduce power loss. Can be suppressed.

In the third invention, the switch circuit controls conduction and non-conduction of the first transistor connected in series with the discharge resistor and the determination by the input voltage determination circuit. And a plurality of resistors connected in series for applying a bias voltage to the first transistor. If it is determined that there is an input voltage, the second transistor turns off the first transistor. Thus, the first transistor prevents the discharging resistor from being connected in parallel with the capacitor. If it is determined that there is no input voltage, the second transistor makes the first transistor conductive. As a result, the first transistor connects the discharging resistor in parallel with the capacitor. A bias voltage is applied to the first transistor by a series circuit including a plurality of resistors. For example, a voltage divided by a series circuit of two resistors is applied to the base of the first transistor as a bias voltage. Thereby, since the bias voltage of the first transistor becomes a voltage corresponding to the current flowing through the resistor, the first transistor can be operated by the constant resistance operation, and the discharge current is suppressed from being sharp, Loss can be suppressed.

In the fourth invention, the input voltage determination circuit includes a diode provided on the output side of the voltage converter, and a parallel circuit of a resistor and a capacitor connected to the cathode of the diode, and the voltage of the capacitor is determined. The presence or absence of an input voltage is determined according to the presence or absence. When the input voltage is cut off, the output voltage converted by the voltage conversion unit is reduced and the voltage of the capacitor of the parallel circuit is also reduced, so that the presence or absence of the input voltage can be reliably determined.

In the fifth invention, the input voltage determination circuit includes a resistor provided in series on the output side of the voltage converter, and determines the presence or absence of the input voltage according to the presence or absence of the current flowing through the resistor. When the input voltage is cut off, the output voltage converted by the voltage converter decreases, and the current flowing through the resistor (for example, the current in the series LED group as a load) does not flow. Can be determined.

In the sixth aspect of the invention, the power supply device and a series LED group to which a voltage is supplied by the power supply device are provided. This prevents unnecessary power consumption when the input voltage is applied, and discharges and lowers the capacitor charge when the input voltage is interrupted. Even if it touches accidentally, it can prevent receiving an electric shock and can provide the LED device which can raise the safety | security of maintenance work.

In the seventh invention, the power supply device and a plurality of LEDs connected in series to which a voltage is supplied by the power supply device are provided. This prevents unnecessary power consumption when the input voltage is applied, and discharges and lowers the capacitor charge when the input voltage is interrupted. It is possible to provide a light source device (for example, a lighting device or a display device) that can prevent an electric shock even when touched by mistake and can increase the safety of maintenance work.

  According to the first invention, when the input voltage is applied, the generation of useless power consumption is suppressed, and when the input voltage is cut off, the charge of the capacitor is discharged and lowered. Even when a maintenance worker touches it by mistake, it is possible to prevent an electric shock and to improve the safety of the maintenance work.

Further , the voltage of the capacitor can be lowered to a safe value or less, and the safety of maintenance work can be improved.

Further , since the electric charge stored in the capacitor is discharged through the discharging resistor, the voltage of the capacitor can be lowered to a safe value or less, and the safety of maintenance work can be improved.

According to the second invention, since the bias voltage of the first transistor becomes a constant voltage by the voltage of the Zener diode, the first transistor can be operated by a constant current operation, and the discharge current is prevented from being steep. In addition, power loss can be suppressed.

According to the third invention, since the bias voltage of the first transistor becomes a voltage corresponding to the current flowing through the resistor, the first transistor can be operated by a constant resistance operation, and the discharge current becomes steep. It is possible to suppress power loss.

According to the fourth invention, when the input voltage is cut off, the output voltage converted by the voltage conversion unit is reduced, and the voltage of the capacitor of the parallel circuit is also reduced. be able to.

According to the fifth aspect, since the output voltage converted by the voltage conversion unit is reduced by cutting off the input voltage and no current flows through the LED, the presence or absence of the input voltage can be reliably determined.

According to the sixth aspect of the invention, it is possible to provide an LED device that can improve the safety of maintenance work.

According to the seventh aspect of the present invention, it is possible to provide a light source device (for example, a lighting device or a display device) that can improve the safety of maintenance work.

It is a block diagram which shows an example of a structure of the light source device which concerns on this Embodiment. It is a time chart which shows an example of the output voltage of the power supply device of this Embodiment. 6 is a block diagram illustrating an example of a configuration of a light source device according to Embodiment 2. FIG. FIG. 10 is a block diagram illustrating an example of a configuration of a light source device according to a third embodiment.

Embodiment 1
Hereinafter, the present invention will be described with reference to the drawings illustrating embodiments thereof. FIG. 1 is a block diagram showing an example of the configuration of the light source device according to this embodiment. The light source device of the present embodiment includes a light source unit 50 in which a power supply device 100 and a plurality of LEDs (light emitting diodes) 1 are connected in series. The light source device is, for example, an illumination device that uses an LED as a light source for illumination, or a display device that uses an LED as a light source for display. In the example of FIG. 1, only one series of light source units 50 (loads) in which a plurality of LEDs 1 are connected in series is illustrated, but the present invention is not limited to this, and is configured by a plurality of LEDs 1. The light source unit 50 may include a plurality of series circuits connected in parallel. In addition, in FIG. 1, although the light source device is shown as an example, it is not limited to a light source device, An LED apparatus provided with the power supply device 100 and series LED group may be sufficient. The LED device may be any electrical device as long as it includes a series LED group.

  An AC voltage (for example, AC100, AC200V, etc.) such as a commercial power supply is applied as an input voltage to the input side of the power supply apparatus 100. Note that the input voltage may be a DC voltage (for example, DC 100 V) of a secondary battery or the like.

  The rectifier circuit 10 rectifies (full-wave rectification or half-wave rectification) the input voltage applied to the power supply device 100. The smoothing capacitor 11 smoothes the voltage rectified by the rectifier circuit 10. The voltage converter 12 converts the input voltage, that is, the voltage smoothed by the smoothing capacitor 11 into a DC voltage.

  The voltage conversion unit 12 includes, for example, a switching element such as a switching transformer and an FET (or transistor), and outputs a high-frequency AC voltage to the output side by turning on / off the FET at a high frequency of about 20 kHz. The voltage converter 12 may be configured to PWM control the input voltage by PWM control, and any configuration may be adopted as long as the input voltage can be converted into a required output voltage. Can do.

  The voltage converted by the voltage converter 12 is rectified by the diode 13 and smoothed by the smoothing capacitor 14. The smoothing capacitor 14 is provided in parallel on the output side of the voltage converter 12 and removes high-frequency noise, ripples, and the like generated in the voltage converter 12. The power supply apparatus 100 outputs the voltage smoothed by the smoothing capacitor 14 as an output voltage. The output voltage can be appropriately determined according to how many LEDs 1 are connected in series in the light source unit 50 as a load, that is, the total value of the forward voltages of the LEDs. The output voltage is, for example, 50V, 60V,.

  The power supply device 100 is provided on the output side of the voltage conversion unit 12, and in addition to the smoothing capacitor 14 connected in parallel to the plurality of LEDs 1, the voltage of the smoothing capacitor 14 has a predetermined value (for example, the forward direction of each of the plurality of LEDs 1). A discharge circuit for discharging the electric charge of the smoothing capacitor 14 when the voltage becomes lower than the total voltage is provided. Here, the predetermined value varies depending on the number, characteristics (forward voltage of the individual LEDs 1) of the plurality of LEDs 1 connected in series as a load, and is not necessarily limited to a specific fixed value. Further, it varies depending on the use state (temperature, energization time) and the like. In any case, the predetermined value can be said to be the voltage of the smoothing capacitor 14 in a state where the electric charge of the smoothing capacitor 14 remains charged and no current flows through the LEDs 1 connected in series. The discharge circuit is a resistor 20 as a discharge resistor connected in parallel to the smoothing capacitor 14. One end of the resistor 20 is connected to the positive side of the output voltage, and the other end of the resistor 20 is connected to the switch circuit 40.

  The switch circuit 40 includes a first transistor 41, a second transistor 42, a resistor 43, a Zener diode 44, a resistor 46, and the like. The other end of the resistor 20 is connected to the collector of the first transistor 41, and the emitter of the first transistor is connected to the ground level via the resistor 46. The base of the first transistor 41 is connected to the collector of the second transistor, and the emitter of the second transistor is connected to the ground level. A series circuit of a resistor 43 and a Zener diode 44 is connected between the collector and the emitter of the first transistor 41, and the first transistor 41 and the second transistor are connected to the connection point between the resistor 43 and the cathode of the Zener diode 44. The collectors of two transistors 42 are connected. The output terminal of the input voltage determination circuit 30 for determining the presence or absence of the input voltage is connected to the base of the second transistor 42.

  That is, the switch circuit 40 switches between the first transistor 41 connected in series with the resistor 20 as a discharging resistor and the conduction and non-conduction of the first transistor 41 according to the determination by the input voltage determination circuit 30. A second transistor 42 for controlling, and a series circuit of a resistor 43 and a Zener diode 44 for applying a bias voltage to the first transistor 41 are provided.

  One end of a resistor 15 is connected between the output terminal of the voltage converter 12 and the anode of the diode 13. The other end of the resistor 15 is connected to the input end of the input voltage determination circuit 30. The resistance value of the resistor 15 can be set as appropriate according to the output voltage of the voltage converter 12. Note that the resistor 15 may be omitted depending on the output voltage of the voltage converter 12.

  The input voltage determination circuit 30 includes a diode 31, a capacitor 32, a resistor 33, and the like. That is, the input voltage determination circuit 30 includes a diode 31 provided on the output side of the voltage converter 12, and a parallel circuit of a resistor 33 and a capacitor 32 connected to the cathode of the diode 31. The presence or absence of an input voltage is determined according to the presence or absence. When the input voltage is applied, the capacitor 32 is charged by the voltage converted by the voltage converter 12, and a predetermined voltage is generated at both ends of the capacitor 32. On the other hand, when the input voltage is cut off, the voltage converted from the voltage converter 12 is not output, so the voltage of the capacitor 32 is discharged by the resistor 33 and becomes zero.

  That is, when an input voltage is applied, a predetermined voltage is output from the input voltage determination circuit 30 to drive the second transistor 42. For this reason, the base voltage of the first transistor 41 becomes almost the ground level, the first transistor 41 becomes non-conductive, the resistor 20 is cut off by the switch circuit 40, and no current flows through the resistor 20, Will not work.

  On the other hand, when the input voltage is interrupted, a predetermined voltage is not output from the input voltage determination circuit 30, and the second transistor 42 is turned off (off). For this reason, a bias voltage having a constant voltage substantially equal to the Zener voltage of the Zener diode 44 is applied to the base of the first transistor 41, the first transistor 41 operates (conducts) in a constant current operation, and the resistor 20 The switch circuit 40 is connected to the ground level, a current flows through the resistor 20, and the discharge circuit is activated.

  FIG. 2 is a time chart showing an example of the output voltage of the power supply apparatus 100 of the present embodiment. 2A shows a change in output voltage in the case of a conventional case as a comparative example, and FIG. 2B shows a change in output voltage in the case of the power supply apparatus 100 of the present embodiment. When the input voltage is cut off at time t1, as shown in FIG. 2A, in the conventional case, the output voltage, that is, the voltage charged in the smoothing capacitor, is obtained from the total value of the forward voltages of the LEDs. When the voltage drops, no current flows through the LED, so the charge of the smoothing capacitor is not discharged and a high voltage is maintained for a long time. On the other hand, in the case of the present embodiment, as shown in FIG. 2 (b), the discharge circuit operates at time t1, so that the charge of the smoothing capacitor is discharged quickly and the output voltage is zero or sufficient. The voltage becomes very low.

  With the above configuration, when an input voltage is applied and an output voltage is supplied to a plurality of LEDs 1 connected in series, the voltage of the smoothing capacitor 14 is the total value (predetermined value) of the forward voltages of the LEDs 1. It will never be lower and the discharge circuit will not work. In addition, when the input voltage is cut off and the voltage of the smoothing capacitor 14 becomes lower than the total value (predetermined value) of the forward voltages of the plurality of LEDs 1, the discharge circuit is activated to discharge the charge of the smoothing capacitor 14. To do. Thereby, when the input voltage is applied, generation of useless power consumption is suppressed, and when the input voltage is cut off, the electric charge of the smoothing capacitor 14 is discharged and lowered. The voltage on the output side of the apparatus 100 can be set to zero or a sufficiently low voltage to prevent an electric shock even when the maintenance worker touches it by mistake, and the safety of the maintenance work can be improved.

  In addition, an input voltage determination circuit 30 that determines the presence or absence of an input voltage is provided. When the input voltage determination circuit 30 determines that there is no input voltage, the discharge circuit discharges the electric charge of the smoothing capacitor 14. When the input voltage is cut off, the output voltage converted by the voltage conversion unit 12 decreases, and the voltage of the smoothing capacitor 14 also decreases. When the voltage of the smoothing capacitor 14 becomes lower than the total value of the forward voltages of the plurality of LEDs 1, no current flows through each LED 1, so that the charge stored in the smoothing capacitor 14 is maintained. By discharging the electric charge of the smoothing capacitor 14 by the discharge circuit (resistor 20), the voltage of the smoothing capacitor 14 can be lowered to a safe value or less, and the safety of maintenance work can be improved.

  The discharge circuit includes a resistor 20 connected in parallel to the smoothing capacitor 14, and further includes a switch circuit 40 connected in series with the resistor 20. When the input voltage determination circuit 30 determines that there is no input voltage, the switch circuit 40 connects the resistor 20 to the smoothing capacitor 14 in parallel. Thereby, since the electric charge stored in the smoothing capacitor 14 is discharged through the resistor 20, the voltage of the smoothing capacitor can be lowered to a safe value or less, and the safety of maintenance work can be improved.

  When the input voltage determination circuit 30 determines that there is no input voltage, the second transistor 42 makes the first transistor 41 conductive. Thus, the first transistor 41 connects the resistor 20 to the smoothing capacitor 14 in parallel. In this case, a voltage divided by a series circuit of the resistor 43 and the Zener diode 44 is applied to the base of the first transistor 41 as a bias voltage. Thereby, since the bias voltage of the first transistor 41 becomes a constant voltage by the Zener voltage of the Zener diode 44, the first transistor 41 can be operated by the constant current operation, and the discharge current is prevented from being steep. In addition, power loss can be suppressed.

  The input voltage determination circuit 30 includes a diode 31 provided on the output side of the voltage converter 12 and a parallel circuit of a resistor 33 and a capacitor 32 connected to the cathode of the diode 31. The presence or absence of an input voltage is determined according to the presence or absence. When the input voltage is cut off, the output voltage converted by the voltage conversion unit 12 is lowered and the voltage of the capacitor 32 is also lowered, so that the presence or absence of the input voltage can be reliably determined.

  In addition, the light source device of the present embodiment includes a power supply device 100 and a plurality of LEDs 1 connected in series to which a voltage is supplied by the power supply device 100. This prevents unnecessary power consumption when the input voltage is applied, and discharges and lowers the capacitor charge when the input voltage is interrupted. It is possible to provide a light source device (for example, a lighting device or a display device) that can prevent an electric shock even when touched by mistake and can increase the safety of maintenance work.

Embodiment 2
FIG. 3 is a block diagram illustrating an example of the configuration of the light source device according to the second embodiment. The difference from the first embodiment is that a resistor 45 is used in place of the Zener diode 44 of the switch circuit 40, and the rest is the same as in the first embodiment.

  In the second embodiment, the switch circuit 40 controls conduction and non-conduction of the first transistor 41 according to the determination by the first transistor 41 connected in series with the resistor 20 and the input voltage determination circuit 30. A second transistor 42, a plurality of resistors 43 and 45 connected in series for applying a bias voltage to the first transistor 41, and a resistor 46 connected to the emitter of the first transistor. . If it is determined that there is an input voltage, the second transistor 42 makes the first transistor 41 non-conductive. As a result, the first transistor 41 prevents the resistor 20 from being connected in parallel to the smoothing capacitor 14. When it is determined that there is no input voltage, the second transistor 42 makes the first transistor 41 conductive. Thus, the first transistor 41 connects the resistor 20 to the smoothing capacitor 14 in parallel. In addition, a bias voltage is applied to the first transistor 41 by a series circuit including a plurality of resistors 43 and 45. That is, a voltage divided by the series circuit of the two resistors 43 and 45 is applied to the base of the first transistor 41 as a bias voltage. As a result, the bias voltage of the first transistor 41 becomes a voltage corresponding to the current flowing through the resistor 45, so that the first transistor 41 can be operated by a constant resistance operation, and the discharge current is prevented from becoming steep. In addition, power loss can be suppressed.

Embodiment 3
FIG. 4 is a block diagram illustrating an example of the configuration of the light source device according to the third embodiment. The difference from the first embodiment is that a resistor 34 provided in series on the output side of the voltage converter 12 is provided instead of the diode 31 of the input voltage determination circuit 30. That is, in the third embodiment, the current flowing through the LED 1 is detected as a voltage by the resistor 34, and the presence or absence of the input voltage is determined according to the presence or absence of the detected voltage (that is, the current flowing through the LED 1).

  In the third embodiment, the input voltage determination circuit 30 includes a resistor 34 connected in series to the LED 1, and determines the presence or absence of an input voltage according to the presence or absence of a current flowing through the resistor 34. When the input voltage is cut off, the output voltage converted by the voltage conversion unit 12 decreases, and no current flows through the LED 1, so it is possible to reliably determine the presence or absence of the input voltage.

  In the third embodiment, the Zener diode 44 of the switch circuit 40 may be replaced with the resistor 45 as in the second embodiment.

  In the first to third embodiments, the transistors 41 and 42 may be replaced with FETs. A resistor for limiting the discharge current may be connected between the emitter of the transistor 41 and the ground level. Further, the transistors 41 and 42 are not limited to the so-called NPN type, but may be a PNP type.

  In the first to third embodiments described above, the resistor 20 is connected in parallel with the smoothing capacitor 14 in accordance with the conduction and non-conduction of the transistor 41. However, the present invention is not limited to this, and the resistor 20 is connected in series. The relay may be connected to a contact. In this case, the relay is excited by the input voltage, and the contact is opened when the input voltage is present, and the contact is closed when there is no input voltage.

1 LED
12 Voltage converter 13 Diode 14 Smoothing capacitor (capacitor)
20 Resistance (Resistance for discharge, discharge circuit)
DESCRIPTION OF SYMBOLS 30 Input voltage determination circuit 31 Diode 32 Capacitor 33, 34 Resistance 40 Switch circuit 41 1st transistor 42 2nd transistor 43, 45, 46 Resistance 44 Zener diode 50 Light source part

Claims (7)

In a power supply device including a voltage conversion unit that converts an input voltage into an output voltage,
A capacitor provided in parallel on the output side of the voltage converter;
A discharging resistor having one end connected to the capacitor ;
A first transistor having a collector connected to the other end of the discharging resistor;
A second transistor having a collector connected to the base of the first transistor;
An input voltage determination circuit for determining the presence or absence of an input voltage;
With
An output terminal of the input voltage determination circuit is connected to a base of the second transistor;
Depending on the determination by the input voltage determination circuit, the conduction and non-conduction of the first transistor are controlled via the second transistor, and the discharging resistor is connected or disconnected in parallel with the capacitor. power apparatus according to claim Citea Rukoto as. A resistor connected between a base and a collector of the first transistor ;
A Zener diode having a cathode connected to a base of the first transistor ;
The power supply device according to claim 1, characterized in that it comprises a. The power supply device according to claim 1, characterized in that it comprises connected multiple resistor between the base and collector and base-emitter of the first transistor. The input voltage determination circuit includes:
A diode having an anode connected to the output terminal of the voltage converter;
A parallel circuit of a resistor and a capacitor connected to the cathode of the diode;
The power supply device according to any one of claims 1 to 3, characterized in that is arranged to determine the presence or absence of the input voltage in accordance with the presence or absence of the voltage of the capacitor. The input voltage determination circuit includes:
A resistor to which an output voltage of the voltage converter is applied ;
The power supply device according to any one of claims 1 to 3, characterized in that is arranged to determine the presence or absence of the input voltage in response to the presence or absence of current flowing through the resistor. An LED device comprising: the power supply device according to any one of claims 1 to 5 ; and a series LED group to which a voltage is supplied by the power supply device. A light source device comprising: the power supply device according to any one of claims 1 to 5 ; and a plurality of LEDs connected in series to which a voltage is supplied by the power supply device.

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