JP2017200249A - Dc power supply and led lighting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a DC power supply configured to prevent a failure in the case where an AC power supply voltage is reversely inputted to a DC output terminal.SOLUTION: A DC power supply (100) comprises: AC input terminals (T1 and T2) and DC output terminals (T3 and T4); a switching power supply circuit (200) by which an AC power supply voltage is converted into a DC output voltage and the DC output voltage is outputted to secondary-side output nodes (N1 and N2); and an inverse input cutoff circuit (300) configured to conduct the secondary-side output nodes and the DC output terminals by receiving an operation voltage (Va) that is generated with the converting operation of the switching power supply circuit in a case where the AC power supply voltage is inputted from the AC input terminals, and open-circuit the secondary-side output nodes and the DC output terminals in a case where the operation voltage is not generated.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a DC power supply device and an LED lighting device.

  Generally, a DC power supply device such as an LED lighting device is connected to an AC power supply such as a commercial power supply via an input connection portion and an input wiring, and is connected to the LED via an output connection portion and an output wiring. In such a DC power supply device, an input AC power supply voltage is converted into a predetermined DC output, and this DC output is supplied to a load such as an LED (for example, Patent Document 1).

JP 2014-35943 A

  In a DC power supply device such as an LED lighting device, normally, an AC wiring to be connected from an AC power supply to an AC input terminal of the DC power supply device and a DC wiring to be connected from a load to a DC output terminal of the DC power supply device , In a manner that can be identified by color coding of the coating. However, in the wiring work of the DC power supply device, the AC wiring is connected to the DC output terminal due to some error, that is, the AC power supply voltage may be reversely input to the DC output terminal. In this case, as will be described in detail later, the DC power supply device fails.

  Then, this invention makes it a subject to provide the DC power supply device and LED lighting device provided with the structure which prevents a failure when an alternating current power supply voltage is reversely input into a direct-current output terminal.

  A DC power supply device according to the present disclosure includes an AC input terminal and a DC output terminal, a switching power supply circuit that converts an AC power supply voltage into a DC output voltage and outputs the DC output voltage to a secondary output node, and a secondary output node Between the secondary output node and the DC output terminal in response to the operating voltage generated by the switching operation of the switching power supply circuit when the AC power supply voltage is input from the AC input terminal. And a reverse input cutoff circuit configured to open between the secondary output node and the DC output terminal when no operating voltage is generated.

  According to the DC power supply device of the present disclosure, the reverse input cutoff circuit is connected between the secondary output node of the switching power supply circuit and the DC output terminal of the DC power supply device. When the AC power supply voltage is correctly input from the AC input terminal to the switching power supply circuit, the reverse input cutoff circuit is turned on by the operating voltage generated by the conversion operation, and the DC output voltage is output to the DC output terminal. Is done. On the other hand, when the AC power supply voltage is not input from the AC input terminal to the switching power supply circuit and no operating voltage is generated, the reverse input cutoff circuit is opened. That is, when the AC power supply voltage is reversely input to the DC output terminal instead of the AC input terminal of the DC power supply device, the secondary output node and the DC output terminal are opened, so the AC power supply voltage is switched to the switching power supply circuit. Is not applied to the secondary side circuit. As a result, a DC power supply device having a configuration for preventing failure when an AC power supply voltage is reversely input to the DC output terminal is realized.

  In the first embodiment, the operating voltage is generated by a constant voltage circuit that rectifies and smoothes the voltage generated in the auxiliary winding of the inductor element included in the switching power supply circuit. As a result, the operating voltage is generated using a circuit for generating the control voltage in the switching power supply circuit, so that the reverse input cutoff circuit is realized with a simple configuration.

  In the second embodiment, the operating voltage is an output voltage of a constant voltage circuit that generates a constant voltage by stepping down the DC output voltage. As a result, the operating voltage is generated using a circuit for generating the control voltage in the switching power supply circuit, so that the reverse input cutoff circuit is realized with a simple configuration. In addition, when the AC power supply voltage is correctly input from the AC input terminal to the switching power supply circuit, when the DC output terminals are short-circuited, the reverse input cutoff circuit is opened due to a drop in the DC output voltage and the operating voltage, resulting in a short circuit. Since the current is cut off, an output short-circuit protection function is also realized.

  In the third mode, the operating voltage is generated by a voltage dividing circuit that divides the DC output voltage. As a result, the operating voltage is generated using the voltage dividing circuit for detecting the DC output voltage of the switching power supply circuit, so that the reverse input cutoff circuit is realized with a simple configuration. In addition, when the AC power supply voltage is correctly input from the AC input terminal to the switching power supply circuit, when the DC output terminals are short-circuited, the reverse input cutoff circuit is opened due to a decrease in the DC output voltage and its divided value. Since the short-circuit current is interrupted, the output short-circuit protection function is also realized.

  In the first to third embodiments, the DC output terminal is composed of a positive output terminal and a negative output terminal, the secondary output node is composed of a positive output node and a negative output node, and the reverse input cutoff circuit includes a transistor and a diode, The transistor has an input electrode, an output electrode, and a control electrode, and is connected between the negative output terminal and the negative output node with the input electrode on the negative output terminal side and the output electrode on the negative output node side, and the operating voltage is controlled. The diode is configured to be applied between the electrode and the output electrode, and the diode is connected between the positive output node and the positive output terminal with the direction from the positive output node toward the positive output terminal as the forward direction, or from the negative output terminal to the negative electrode A transistor is connected in series between the negative output node and the negative output terminal with the direction toward the output node as the forward direction. Thus, the reverse input cutoff circuit is realized with a simple configuration using the transistor and the diode.

  In the fourth mode, the DC output terminal is composed of a positive output terminal and a negative output terminal, the secondary output node is composed of a positive output node and a negative output node, and the reverse input cutoff circuit is connected from the negative output terminal to the negative output node. A thyristor connected between the negative output terminal and the negative output node with the direction toward the forward direction as a forward direction may be provided, and a trigger current may be supplied between the gate and the cathode of the thyristor based on the operating voltage. Thus, the reverse input cutoff circuit is realized with a simple configuration using a thyristor.

  In the fifth embodiment, the DC output terminal is composed of a positive output terminal and a negative output terminal, the secondary output node is composed of a positive output node and a negative output node, and the reverse input cutoff circuit is connected from the positive output node to the positive output terminal. A thyristor connected between the positive output node and the positive output terminal with the forward direction as the forward direction, or a thyristor connected between the negative output terminal and the negative output node with the direction from the negative output terminal to the negative output node as the forward direction The operating voltage is a rectified voltage of a voltage generated in the auxiliary winding of the inductor element included in the switching power supply circuit, and the trigger current is passed between the gate and the cathode of the thyristor based on the rectified voltage. May be. Thus, even when a constant voltage circuit for generating a control voltage or a voltage dividing circuit for detecting a DC output voltage is not provided on the secondary side of the switching power supply circuit, a reverse input blocking circuit having a relatively simple configuration Is realized.

  The LED lighting device according to the present disclosure includes any one of the DC power supply devices described above, and the output capacitor connected in parallel to the secondary output node is an electrolytic capacitor. Thus, the reverse input cutoff circuit is particularly useful when the polarity of the secondary part of the switching power supply circuit is determined, such as when the output capacitor is an electrolytic capacitor for reducing LED output ripple. .

  The LED lighting device according to the present disclosure includes any one of the DC power supply devices described above, and the switching power supply circuit includes a step-down converter for supplying power to the LEDs. Thus, the reverse input cutoff circuit is particularly useful when the withstand voltage of the secondary part of the switching power supply circuit is lower than the AC power supply voltage.

It is a circuit diagram of the LED lighting device by a 1st embodiment of this indication. It is a circuit diagram of the LED lighting device by a 2nd embodiment of this indication. It is a circuit diagram of the LED lighting device by a 3rd embodiment of this indication. It is a circuit diagram of the LED lighting device by a 4th embodiment of this indication. It is a circuit diagram of the LED lighting device by a 5th embodiment of this indication.

<First Embodiment>
FIG. 1 shows an LED lighting device 100 that is a DC power supply device according to the first embodiment of the present disclosure. The LED lighting device 100 has AC input terminals T1 and T2 and DC output terminals T3 and T4. When correctly wired, AC input terminals T1 and T2 are connected to AC lines W1 and W2 from an AC power source AC such as a commercial power source, and DC output terminals T3 and T4 are connected to terminals T5 and T6 of the LED unit 50. DC wirings W3 and W4 are connected. Thereby, in normal use, the LED lighting device 100 is supplied with an AC voltage from the AC input terminals T1 and T2, and outputs a DC voltage or a DC current from the DC output terminals T3 and T4. The LED unit 50 includes an arbitrary number of LEDs 50a connected in series.

  The LED lighting device 100 includes a switching power supply circuit 200 and a reverse input cutoff circuit 300. The switching power supply circuit 200 is provided on the AC input terminals T1 and T2, and the reverse input cutoff circuit 300 is connected between the secondary output nodes N1 and N2 of the switching power supply circuit 200 and the DC output terminals T3 and T4. . In the following description, the DC output terminals T3 and T4 are also referred to as a positive output terminal T3 and a negative output terminal T4, respectively, and the secondary output nodes N1 and N2 are also referred to as a positive output node N1 and a negative output node N2, respectively. In the present disclosure, regarding a switching element such as an FET or a diode, “conduction” and “on” are substantially synonymous, and “open” and “off” are substantially synonymous.

  The switching power supply circuit 200 includes an input circuit 210, a DC / DC converter 220, a detection circuit 230, an auxiliary power supply circuit 240, and a control circuit 250, converts an input AC voltage into a DC output voltage, and converts the DC output voltage to a secondary side. Output to output nodes N1 and N2.

  The input circuit 210 includes current fuses 1 and 2, a diode bridge 3, an input capacitor 4, and a noise filter as necessary. An AC voltage from the AC power source AC is input to the input circuit 210, and the full-wave rectified output from the diode bridge 3 is slightly smoothed by the input capacitor 4 and input to the DC / DC converter 220.

  In the present embodiment, the DC / DC converter 220 is an isolated flyback converter, and constitutes a so-called one-converter flyback circuit having a power factor improving function. The DC / DC converter 220 includes a switching element 5, a transformer 6, a current detection resistor 7, a diode 8, and an output capacitor 9. In the present embodiment, since the DC / DC converter 220 is a power factor improving type, the capacity of the output capacitor 9 is sufficiently larger than the capacity of the input capacitor 4, and the output capacitor 9 is composed of an electrolytic capacitor or the like. In the present embodiment, since the switching element 5 is made of a MOSFET, the switching element 5 is also referred to as an FET 5 hereinafter. The reference point on the primary winding 6a side of the transformer 6 (that is, the low potential electrode side node of the input capacitor 4) is referred to as the primary side ground G1, and the reference point on the secondary winding 6b side (that is, the output capacitor 9). The low potential electrode side node) is referred to as a secondary side ground G2.

  In PWM control of the DC / DC converter 220, energy is accumulated on the primary winding 6a side during the ON period of the FET 5, and the energy is transferred from the secondary winding 6b side to the output capacitor 9 via the diode 8 during the OFF period of the FET 5. It is charged and supplied to the LED 50a. The output of the DC / DC converter 220 is determined by the ON duty (ON width) of the FET 5, the turn ratio of the secondary winding 6b to the primary winding 6a, and the like. The FET 5 is PWM driven by a gate signal output from the primary side control circuit 251. In the following description, the DC output current (LED current) of the DC / DC converter 220 is referred to as “output current”, and the DC output voltage of the DC / DC converter 220 is referred to as “output voltage”.

  The detection circuit 230 includes a current detection circuit including the current detection resistor 10 and a voltage detection circuit 235 including the resistors 11, 12 and 13, and uses the secondary side ground G2 as a reference potential. The current detection resistor 10 includes a low resistance element inserted between the secondary side ground G2 and the cathode end of the LED unit 50. Voltage detection circuit 235 includes a voltage dividing circuit connected to secondary side output nodes N1-N2. In the drawing, the voltage detection circuit 235 is shown by three series resistors 11 to 13, but the number of series resistors connected is arbitrary.

  The auxiliary power supply circuit 240 includes a primary side constant voltage circuit 241 and a secondary side constant voltage circuit 242. The constant voltage circuit 241 includes an auxiliary winding 6 c of the transformer 6, a diode 14, a capacitor 15, and a Zener diode 16. The constant voltage circuit 241 rectifies and smoothes the voltage generated in the auxiliary winding 6c with the diode 14 and the capacitor 15 with the primary side ground G1 as a reference to generate the primary side control voltage Vcc1. The control voltage Vcc1 is clamped by the Zener diode 16 so as to be equal to or lower than the upper limit value. The constant voltage circuit 242 includes an auxiliary winding 6 d of the transformer 6, a diode 17, a capacitor 18, and a voltage regulator circuit 19. The voltage regulator circuit 19 is a series regulator, a three-terminal regulator, or the like. The constant voltage circuit 242 rectifies and smoothes the voltage generated in the auxiliary winding 6d with the diode 17 and the capacitor 18 with the secondary side ground G2 as a reference, and converts the rectified and smoothed voltage into a constant voltage by the voltage regulator circuit 19 to obtain a secondary voltage. Side control voltage Vcc2 is generated.

  The control circuit 250 includes a primary side control circuit 251, a secondary side control circuit 252, a resistor 20 and a photocoupler 21. The primary side control circuit 251 is activated by receiving a voltage drop of the rectified output of the diode bridge 3 through the activation resistor 20 with the primary side ground G1 as a reference, and thereafter operates by receiving the control voltage Vcc1. The primary-side control circuit 251 includes a PWM control driver IC and the like, and PWM-drives the FET 5 according to a signal input from the photocoupler 21, a detection input from the current detection resistor 7, and the like. The secondary side control circuit 252 receives the control voltage Vcc2 and operates based on the secondary side ground G2. The secondary control circuit 252 amplifies the error between the current detection value from the current detection resistor 10 and the current target value and outputs an error signal, and the voltage detection value and voltage target value (upper limit value) from the voltage detection circuit 235. ) And an operational amplifier that outputs an error signal.

  The error signal from the secondary side control circuit 252 is transmitted to the primary side control circuit 251 via the photocoupler 21, and the primary side control circuit 251 determines the PWM drive ON width of the FET 5 according to the error signal. Therefore, in the control circuit 250, constant current control is executed so that the detected current value matches the current target value, or constant voltage control is executed so that the detected voltage value matches the upper limit value. In general, the secondary side control circuit 252 is configured such that constant current control is selected during normal lighting and constant voltage control is selected during no load.

  Next, the reverse input cutoff circuit 300 will be described. In the following description, the state in which the AC wirings W1 and W2 are correctly connected to the AC input terminals T1 and T2 is referred to as “normal connection”, and the AC power supply voltage is the LED lighting device 100 (switching power supply circuit 200) in this normal connection state. The state input to is referred to as “normal input”. On the other hand, the state in which the AC wirings W1 and W2 are erroneously connected to the DC output terminals T3 and T4 instead of the AC input terminals T1 and T2 is referred to as “AC reverse connection”. A state in which a reverse input is made to the apparatus 100 is referred to as an “AC reverse input”.

  Here, the operation at the time of AC reverse input when there is no reverse input cutoff circuit 300 will be described. First, when the DC output terminal T4 has a higher potential than the DC output terminal T3, a voltage having a reverse polarity is applied to the output capacitor 9 (electrolytic capacitor), causing the output capacitor 9 to fail. Further, regardless of the phase of the AC power supply voltage, when the AC power supply voltage exceeds the withstand voltage of the output capacitor 9, the diode 8, or the voltage detection circuit 235, each component fails. Thus, if AC reverse input occurs without the reverse input cutoff circuit 300, the switching power supply circuit 200 may fail. The reverse input cut-off circuit 300 cuts off the application of the AC power supply voltage to the secondary side components (that is, the output capacitor 9, the diode 8, and the voltage detection circuit 235) of the switching power supply circuit 200 in such an AC reverse connection. To do.

  The reverse input cutoff circuit 300 is connected between the secondary output nodes N1 and N2 and the DC output terminals T3 and T4, and includes a transistor 31, a diode 32, and a resistor 33. In this embodiment, since the transistor 31 is a MOSFET, the transistor 31 is hereinafter referred to as an FET 31. The drain of the FET 31 is connected to the negative output terminal T4, the source is connected to the negative output node N2, and the resistor 33 is connected between the gate and the source. Between the gate and source of the FET 31, the rectified and smoothed output from the constant voltage circuit 242 is supplied as the operating voltage Va. The anode of the diode 32 is connected to the positive output node N1, and the cathode is connected to the positive output terminal T3. The diode 32 may be connected in series with the FET 31 between the negative output terminal T4 and the negative output node N2 with the direction from the negative output terminal T4 toward the negative output node N2 as the forward direction. Further, the operating voltage Va may be the control voltage Vcc2.

  At the time of normal input, the DC / DC converter 220 operates to apply the operating voltage Va between the gate and source of the FET 31, and the FET 31 is turned on (conductive). As a result, the output current flows through the positive output node N1, the diode 32, the positive output terminal T3, the DC wiring W3, the LED unit 50, the DC wiring W4, the negative output terminal T4, the FET 20, and the negative output node N2. Light.

  At the time of AC reverse connection, the primary side control circuit 251 does not start because the start voltage is not supplied via the start resistor 20, and the FET 5, that is, the DC / DC converter 220 does not operate. Accordingly, since no voltage is generated in the auxiliary winding 6d, the constant voltage circuit 242 does not generate the operating voltage Va, and the FET 31 is maintained in an open state.

  In the phase where the positive electrode output terminal T3 is at a higher potential than the negative electrode output terminal T4 during AC reverse input, the diode 32 is turned off, so that the AC power supply voltage is not applied to the secondary circuit of the switching power supply circuit 200. If there is no diode 32, a current path through a regenerative diode (not shown) of the FET 31 is generated even if the FET 31 is in an OFF state. Further, even if the FET 31 is a transistor that does not have a regenerative diode, a reverse voltage is applied to the transistor, causing a failure of the transistor. Therefore, the diode 32 needs to be connected with the direction from the positive output node N1 toward the positive output terminal T3 as the forward direction or the direction from the negative output terminal T4 toward the negative output node N2 as the forward direction.

  Further, in the phase where the positive output terminal T4 is at a higher potential than the negative output terminal T3 at the time of AC reverse input, the FET 31 is in the OFF state, so that no AC power supply voltage is applied to the secondary circuit of the switching power supply circuit 200. As described above, during the AC reverse input, the reverse input cutoff circuit 300 blocks the reverse input of the AC power supply voltage.

  Here, as in the case where the output capacitor 9 is an electrolytic capacitor for reducing the LED output ripple (that is, the ripple of the light output caused by the ripple of the LED current), the polarity of the secondary side component of the switching power supply circuit 200 Is determined to be particularly useful. However, of course, the technique of the present disclosure can also be applied when the output capacitor 9 is a nonpolar part such as a film capacitor or a ceramic capacitor. Further, the reverse input cutoff circuit 300 is particularly useful when the withstand voltage of the secondary side component is lower than the AC power supply voltage, such as when the DC / DC converter 220 is a step-down converter. However, of course, the technique of the present disclosure can also be applied when the DC / DC converter 220 is a boost converter.

  As described above, the LED lighting device 100 according to the present embodiment includes the switching power supply circuit 200 that converts an AC power supply voltage into a DC output voltage and outputs the DC output voltage to the secondary output nodes N1 and N2, and the secondary side. The reverse input cutoff circuit 300 is connected between the output nodes N1 and N2 and the DC output terminals T3 and T4. The reverse input cutoff circuit 300 is an operating voltage generated in accordance with the conversion operation of the switching power supply circuit 200 during normal input. In response to Va, the secondary output nodes N1 and N2 and the DC output terminals T3 and T4 are electrically connected. When the operating voltage Va is not generated, the secondary output nodes N1 and N2 and the DC output terminals T3 and T4 are connected. It is configured to open the gap.

  As a result, the reverse input cutoff circuit 300 is turned on by the operating voltage Va generated by the DC conversion operation during normal input and the output voltage is output to the DC output terminals T3 and T4, while the DC conversion operation is performed during AC reverse connection. Stops and the reverse input cut-off circuit 300 is opened. That is, since the secondary output node and the DC output terminal are opened at the time of AC reverse input, the AC power supply voltage is not reversely input to the secondary circuit of the switching power supply circuit 200. Thereby, the LED lighting device 100 provided with the structure which prevents the failure at the time of AC reverse input is implement | achieved.

  In addition, since the reverse input cutoff circuit 300 includes the FET 31 and the diode 32 connected with the above-described polarity between the secondary output nodes N1 and N2 and the DC output terminals T3 and T4, the reverse input cutoff circuit 300 includes Realized with a simple configuration.

  In this embodiment, the operating voltage Va is generated by a constant voltage circuit 242 that rectifies and smoothes a voltage generated in the auxiliary winding 6d of the transformer 6. That is, since the operating voltage Va is generated using the constant voltage circuit 242 for generating the control voltage Vcc2, the reverse input cutoff circuit 300 is realized with a simple configuration.

<Second Embodiment>
In the first embodiment, the operation voltage Va and the control voltage Vcc2 are obtained from the auxiliary winding 6d of the transformer 6. However, in the present embodiment, the operation voltage Va and the control voltage Vcc2 are obtained from the output voltage. The configuration is shown. In the present embodiment, the same or corresponding components as those in the first embodiment are denoted by the same reference numerals, and redundant description thereof is omitted.

  In FIG. 2, the LED lighting device 100 of this embodiment is shown. In the present embodiment, the auxiliary power supply circuit 240 includes a constant voltage circuit 243 that steps down the output voltage and generates a constant voltage. For example, the constant voltage circuit 243 includes a transistor 22, a resistor 23, a Zener diode 24, and a capacitor 25, and constitutes a series regulator. The collector of the transistor 22 is connected to a node having the same potential as the positive output node N1, the base is connected to the secondary side ground G2 via the Zener diode 24, and the emitter voltage becomes the control voltage Vcc2 and the operating voltage Va. The constant voltage circuit 243 may be configured with a three-terminal regulator or the like.

  The operation during normal input and AC reverse input is substantially the same as in the first embodiment. That is, at the time of normal input, the DC / DC converter 220 operates and the FET 31 is turned on by the operating voltage Va (control voltage Vcc2) generated by the constant voltage circuit 243, whereby the output current is supplied to the LED 50a. At the time of AC reverse input, since the DC / DC converter 220 does not operate, the output voltage and the operating voltage Va are not generated, and the FET 31 is maintained in the off state. Therefore, the AC power supply voltage is not applied to the secondary side circuit of the switching power supply circuit 200.

  The constant voltage circuit 243 in the present embodiment and the constant voltage circuit 242 in the first embodiment may be used in combination. As a result, the control voltage Vcc2 and the operating voltage Va can be reliably generated.

  It should be noted that the FET 31 can be kept on by the residual voltage of the output capacitor 9 in a short period after the DC / DC converter 220 stops operating due to, for example, turning off the AC power supply AC, but in this embodiment, this period is It can be ignored as it is short enough. This is because the DC wires W3 and W4 are pulled out from the DC output terminals T3 and T4 in a short period immediately after the AC power supply AC is cut off, and the AC wires W1 and W2 (drawn from the AC input terminals T1 and T2). Alternatively, it is difficult to consider connecting other AC wirings to the DC output terminals T3 and T4.

  As described above, also in the present embodiment, as in the first embodiment, the LED lighting device 100 having a configuration for preventing a failure at the time of reverse AC input is realized with a simple configuration using the FET 31 and the diode 32. . In particular, in this embodiment, the operating voltage Va is an output voltage of the constant voltage circuit 243 that steps down the output voltage to generate a constant voltage. As described above, since the operating voltage Va is generated using the circuit for generating the control voltage Vcc2, the reverse input cutoff circuit 300 having a simple configuration is realized. In addition, when the DC output terminals T3 to T4 are short-circuited during normal input, the FET 31 is opened due to a decrease in the output voltage and the operating voltage Va and the short-circuit current is cut off. Can also function.

<Third Embodiment>
In the first and second embodiments, the configuration in which the operating voltage Va is generated by the auxiliary power supply circuit 240 is shown, but in the present embodiment, the configuration in which the operating voltage Va is generated by the detection circuit 230 is shown. In the present embodiment, the same or corresponding components as those in the first or second embodiment are denoted by the same reference numerals, and redundant description thereof is omitted.

  In FIG. 3, the LED lighting device 100 of this embodiment is shown. In the present embodiment, a detection voltage (voltage of the resistor 13) by the voltage detection circuit 235 of the detection circuit 230 is applied between the gate and source of the FET 31 as the operating voltage Va. However, in the voltage detection circuit 235 which is a voltage dividing circuit, the voltage dividing ratio for generating the operating voltage Va is set to a voltage dividing ratio for detecting the output voltage (ratio of the resistance value of the resistor 13 to the resistance value of the resistors 11 to 13). ) May be different. In this case, the detection voltage and the operating voltage Va are acquired from different resistance division nodes. A voltage dividing circuit for operating the FET 31 may be provided separately from the voltage detection circuit 235. The voltage dividing circuit in this case may be, for example, a discharge resistor for residual voltage discharge of the output capacitor 9. An input resistor that adjusts the input impedance from the voltage detection circuit 235 to the FET 31 and the secondary side control circuit 252 (for example, an operational amplifier) may be appropriately connected.

  The operation during normal input and AC reverse input is substantially the same as in the second embodiment. That is, at the time of normal input, the DC / DC converter 220 operates and the FET 31 is turned on by the operating voltage Va generated by the voltage detection circuit 235, whereby the output current is supplied to the LED 50a. At the time of AC reverse input, since the DC / DC converter 220 does not operate, the output voltage and the operating voltage Va are not generated, and the FET 31 is maintained in the off state. Therefore, the AC power supply voltage is not applied to the secondary side circuit of the switching power supply circuit 200.

  As described above, also in the present embodiment, as in the first embodiment, the LED lighting device 100 having a configuration for preventing a failure at the time of reverse AC input is realized with a simple configuration using the FET 31 and the diode 32. . In particular, in the present embodiment, since the operating voltage Va is generated using the voltage detection circuit 235 that divides the output voltage, the reverse input cutoff circuit 300 having a simple configuration is realized. Similarly to the second embodiment, when the DC output terminals T3 to T4 are short-circuited during normal input, the FET 31 is opened due to the decrease in the output voltage and the operating voltage Va, and the short-circuit current is cut off. The reverse input cutoff circuit 300 can also serve as an output short-circuit protection function.

<Fourth Embodiment>
In the first to third embodiments, the reverse input cutoff circuit 300 includes the FET 31 and the diode 32. However, in the present embodiment, the reverse input cutoff circuit 300 includes a thyristor. In this embodiment, the same or corresponding components as those in the first to third embodiments are denoted by the same reference numerals, and redundant description thereof is omitted.

  In FIG. 4, the LED lighting device 100 of this embodiment is shown. In the present embodiment, the reverse input cutoff circuit 300 includes a thyristor 34 and a resistor 35. The anode of the thyristor 34 is connected to the negative output terminal T4, the cathode is connected to the negative output node N2, and the gate is connected to the constant voltage circuit 242 via the resistor 35. That is, a trigger current is applied between the gate and cathode of the thyristor 34 based on the operating voltage Va. 4 shows a configuration in which the operating voltage Va is generated by the constant voltage circuit 242 as in the first embodiment, but the operating voltage Va is the constant voltage circuit as in the second or third embodiment. 243 or a voltage dividing circuit (voltage detection circuit 235, discharge resistor (not shown), etc.).

  The operation during normal input and AC reverse input is substantially the same as in the first embodiment. That is, during normal input, the DC / DC converter 220 operates and the thyristor 34 is turned on by the operating voltage Va. As a result, the output current flows from the positive output node N1 → the positive output terminal T3 → the DC wiring W3 → the LED unit 50 → the DC wiring W4 → the negative output terminal T4 → the thyristor 34 → the negative output node N2, and this current flows through the thyristor 34. It is also a holding current. At the time of AC reverse input, the DC / DC converter 220 does not operate, so that the operating voltage Va is not generated and the thyristor 34 is maintained in the OFF state. Therefore, the AC power supply voltage is not applied to the secondary side circuit of the switching power supply circuit 200.

  As described above, also in the present embodiment, the LED lighting device 100 having a configuration for preventing a failure at the time of AC reverse input is realized as in the first embodiment. The reverse input cutoff circuit 300 is realized with a simple configuration using the thyristor 34.

<Fifth Embodiment>
In the first to fourth embodiments, the configuration on the premise that the switching power supply circuit 200 has the secondary side control circuit 252 is shown. However, in the present embodiment, the switching power supply circuit 200 is configured to have the secondary side control circuit. The structure in the case of not having is shown. In the present embodiment, the same or corresponding components as those in the first to fourth embodiments are denoted by the same reference numerals, and redundant description thereof is omitted.

  In FIG. 5, the LED lighting device 100 of this embodiment is shown. In the present embodiment, in the switching power supply circuit 200, feedback control (constant current control or constant voltage control) of output current or output voltage is not performed, and feedforward control by the primary side control circuit 251 is performed.

  The reverse input cutoff circuit 300 includes a thyristor 34, a diode 36, a resistor 37, and an auxiliary winding 6 e of the transformer 6. The anode of thyristor 34 is connected to negative output terminal T4, and the cathode is connected to negative output node N2. One end of the auxiliary winding 6e is connected to the gate of the thyristor 34 via the diode 36 and the resistor 37, and the other end is connected to the secondary side ground G2. That is, a trigger current flows from the gate to the cathode of the thyristor 34 based on the voltage (operation voltage Va) generated in the auxiliary winding 6e. The anode of the thyristor 34 may be connected to the positive output node N1, and the cathode may be connected to the positive output terminal T3. In this case, the other end of the auxiliary winding 6e is connected not to the secondary side ground G2 but to the same potential node as the positive output terminal T3. Since the auxiliary winding 6e only needs to generate the trigger current of the thyristor 34, the auxiliary winding 6e has fewer turns than the auxiliary winding 6d (see FIGS. 1, 3 and 4) for generating the control voltage Vcc2. Although the configuration is included in the fourth embodiment, when the thyristor 34 is connected between the negative output terminal T4 and the negative output node N2, the operating voltage Va applied to the gate is the output voltage. May be obtained from a voltage dividing circuit (such as a discharge resistor (not shown)) that steps down the voltage.

  The operation during normal input and AC reverse input is substantially the same as in the fourth embodiment. That is, at the time of normal input, the DC / DC converter 220 operates and the thyristor 34 is turned on by the voltage generated in the auxiliary winding 6e. Thereby, an output current is supplied to the LED 50a, and this output current also serves as a holding current of the thyristor 34. At the time of AC reverse input, since the DC / DC converter 220 does not operate, no voltage is generated in the auxiliary winding 6e, and the thyristor 34 is maintained in the off state. Therefore, the AC power supply voltage is not applied to the secondary side circuit of the switching power supply circuit 200.

  As described above, also in the present embodiment, as in the first embodiment, the LED lighting device 100 having a configuration for preventing a failure at the time of reverse AC input is realized. In particular, in this embodiment, even when the constant voltage circuit 242 or 243 or the voltage detection circuit 235 is not provided, the reverse input cutoff circuit 300 having a relatively simple configuration is realized.

<Modification>
Although preferred embodiments of the present invention have been described above, the present invention can be modified into various modes as shown below, for example.

(1) Modifications related to DC power supply In each of the above embodiments, the LED lighting device 100 using the LED unit 50 (LED 50a) as a load is shown as the DC power supply, but other DC loads (for example, a discharge for DC lighting) are shown. The present invention is also applicable to a DC power supply device for driving an electric lamp or the like.

(2) Modifications related to FET 31 In the first to third embodiments, the FET is used as the transistor 31 of the reverse input cutoff circuit 300. However, a bipolar transistor such as an IGBT is used instead of the FET. Also good. In the present disclosure, an input electrode, an output electrode, and a control electrode of a transistor mean a drain, a source, and a gate, respectively, when the transistor is an FET, and a collector, an emitter, and a base when the transistor is a bipolar transistor. Each means.

(3) Modification Regarding DC / DC Converter 220 In the above embodiments, the DC / DC converter 220 is a flyback converter. However, the DC / DC converter 220 is not limited to a buck converter, a buck boost converter, or the like. It may be a format converter. In this case, the auxiliary winding corresponding to the auxiliary winding 6d or 6e may be provided in the inductor element (choke coil) of each converter.

6 Transformer (inductor element)
6d, 6e Auxiliary winding 31 FET (transistor)
32 Diode 34 Thyristor 100 LED lighting device (DC power supply)
200 switching power supply circuit 235 voltage detection circuit (voltage dividing circuit)
242, 243 Constant voltage circuit 300 Reverse input cutoff circuit N1 Positive output node (secondary output node)
N2 Negative output node (secondary output node)
T1, T2 AC input terminal T3 Positive output terminal (DC output terminal)
T4 Negative output terminal (DC output terminal)

Claims (9)

A DC power supply device having an AC input terminal and a DC output terminal,
A switching power supply circuit that converts an AC power supply voltage into a DC output voltage and outputs the DC output voltage to a secondary output node;
Connected between the secondary output node and the DC output terminal, and receiving the operating voltage generated along with the conversion operation of the switching power supply circuit when the AC power supply voltage is input from the AC input terminal, A reverse input cutoff circuit configured to conduct between a secondary output node and the DC output terminal and to open between the secondary output node and the DC output terminal when the operating voltage is not generated And a DC power supply device.   2. The DC power supply device according to claim 1, wherein the operating voltage is generated by a constant voltage circuit that rectifies and smoothes a voltage generated in an auxiliary winding of an inductor element included in the switching power supply circuit.   3. The DC power supply device according to claim 1, wherein the operating voltage is an output voltage of a constant voltage circuit that generates a constant voltage by stepping down the DC output voltage.   3. The DC power supply device according to claim 1, wherein the operating voltage is generated by a voltage dividing circuit that divides the DC output voltage. In the direct-current power supply device according to any one of claims 2 to 4, the direct-current output terminal comprises a positive output terminal and a negative output terminal, the secondary output node comprises a positive output node and a negative output node,
The reverse input cutoff circuit comprises a transistor and a diode;
The transistor has an input electrode, an output electrode, and a control electrode, and is connected between the negative output terminal and the negative output node with the input electrode on the negative output terminal side and the output electrode on the negative output node side. The operating voltage is applied between the control electrode and the output electrode,
The diode is connected between the positive output node and the positive output terminal with a direction from the positive output node toward the positive output terminal as a forward direction, or in a forward direction from the negative output terminal to the negative output node. A DC power supply device connected in series with the transistor between the negative output node and the negative output terminal as a direction. In the direct-current power supply device according to any one of claims 2 to 4, the direct-current output terminal comprises a positive output terminal and a negative output terminal, the secondary output node comprises a positive output node and a negative output node,
The reverse input cutoff circuit includes a thyristor connected between the negative output terminal and the negative output node with a direction from the negative output terminal to the negative output node as a forward direction, and based on the operating voltage, the thyristor A DC power supply device configured such that a trigger current is passed between the gate and the cathode. The DC power supply device according to claim 1, wherein the DC output terminal comprises a positive output terminal and a negative output terminal, the secondary output node comprises a positive output node and a negative output node,
The reverse input cutoff circuit is a thyristor connected between the positive output node and the positive output terminal with the direction from the positive output node toward the positive output terminal as a forward direction, or from the negative output terminal to the negative output node A thyristor connected between the negative output terminal and the negative output node with the direction toward the forward direction as a forward direction,
The operating voltage is a rectified voltage of a voltage generated in an auxiliary winding of an inductor element included in the switching power supply circuit, and a trigger current is passed between the gate and the cathode of the thyristor based on the rectified voltage. Configured DC power supply.   8. An LED lighting device comprising the DC power supply device according to claim 1, wherein the output capacitor connected in parallel to the secondary output node is an electrolytic capacitor. The LED lighting device comprising the DC power supply device according to claim 1, wherein the switching power supply circuit includes a step-down converter for supplying power to the LED.

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