JP6245433B2 - LED power supply device and LED lighting device - Google Patents

Description

  The present invention relates to an LED power supply device and an LED lighting device using the LED power supply device.

  Patent Document 1 discloses an LED lighting device including a step-down circuit capable of performing constant current control and constant voltage control. The LED lighting device includes a constant current control circuit that generates a current setting feedback signal for preventing the output current value from exceeding the constant current value, and the output voltage value from exceeding the constant voltage value. And a constant voltage control circuit for generating a voltage setting feedback signal. The switching element of the step-down circuit is driven by a current setting feedback signal and a voltage setting feedback signal. When constant number of LEDs that are less than the maximum connectable number are connected, constant current control is performed, and when more LEDs than the maximum connectable number are connected or when there is no load due to LED disconnection The constant voltage control is performed.

  Patent Document 2 discloses an LED driving device that determines the connection state of an LED light source from the detection result of the output current and adjusts the output to the LED. The LED driving device includes a converter that outputs a DC voltage to the LED light source and a current detection unit that detects a current flowing through the LED light source. If the detected current exceeds the threshold value, the LED light source is connected and the converter output voltage is adjusted so that the LED current becomes the set value. If the detected current is less than the threshold value, the LED light source is connected. As a result, the output voltage is gradually reduced. Thereby, the output of the LED driving device is set to a standby state or a stopped state.

Japanese Patent No. 4971254 Japanese Patent No. 4169008

  However, according to the configuration of Patent Document 1, constant voltage control is performed so that the output voltage becomes the upper limit set value when the LED disconnection causes a no-load state. Therefore, there is a problem that a high voltage is generated between the output terminals when there is no load.

  Further, according to the configuration of Patent Document 2, since the output voltage is gradually reduced after no load is detected, it takes a long time to reach a predetermined low voltage state. Therefore, there is a problem that a desired protective function is not exhibited because a high voltage is generated at the output terminal of the LED driving device during the reduction period of the output voltage.

  By the way, when the input power supply is an AC power supply, a voltage of about 140 V (at 100 VAC) to 280 V (at 200 VAC) is applied to the primary side of the converter circuit. Such a configuration that directly generates a control voltage of about 5 to 15 V from a high primary voltage via a resistor has a large loss, and a configuration that directly generates the control voltage by a voltage regulator is expensive. Therefore, generally, when the input power supply is an AC power supply, the power generated on the secondary side of the converter circuit is used to generate the control power supply. Here, according to the configuration of Patent Document 2, the output voltage continues to decrease even after reaching a predetermined low output voltage. Therefore, when the output voltage is reduced in a configuration in which the input power supply is an AC power supply and the control power supply is generated according to the secondary output of the converter circuit, the control power supply is secured when the output voltage becomes very low. May not be maintained and the protection state may not be maintained. Similarly, when the output voltage is stopped, the protection state is not maintained.

  Therefore, the present invention provides an LED power supply device that does not generate a high voltage at an output terminal even in a no-load state and that can maintain a stable power-supply protection operation by securing a control power supply and an LED illumination using the same It is an object to provide an apparatus.

  The LED power supply device of the present invention includes an output terminal connected to both ends of the LED, a switching power supply circuit that can apply a DC voltage to the output terminal, a no-load detection unit that detects a no-load state of the output terminal, and an output terminal And a control unit that is supplied with power according to the driving of the switching power supply circuit and that causes the switch element to conduct when a no-load state is detected.

  According to the LED power supply device, when the LED power supply device is unloaded, the output terminal is forcibly short-circuited by the switch element, so that a high voltage is not generated at the output terminal even in the no-load state. In addition, it is possible to maintain the output short-circuit state by securing the control power supply by driving the switching power supply circuit for flowing current in the LED power supply device. Thereby, the safety | security at the time of the instrument replacement | exchange, inspection, etc. at the time of abnormality of LED power supply device improves.

  Here, it is preferable that the control unit is configured to reduce the output current of the switching power supply circuit when the switch unit is conducting. Thereby, the heat_generation | fever of the component of a switching power supply circuit and switch element in an output short circuit state can be reduced.

  Furthermore, a current detection unit including a plurality of current detection resistors inserted in the output current path of the switching power supply circuit is provided, and the control unit switches the switching power supply so that the current detected by the current detection unit matches the current target value. It may be configured to control the output current of the circuit and increase the combined resistance value of the current detection unit when the switch element is turned on. Thereby, the accuracy of the constant current control in the output reduction state at the time of no-load detection is improved, and the circuit operation in the output short-circuit state is further stabilized.

  The switch unit may include an auxiliary LED connected in series to the switch element. As a result, it is possible to notify the user that an abnormality that causes a no-load condition has occurred and that the LED power supply device is powered on.

  Further, the control unit may make the switch element conductive even when the LED is turned off. Thereby, it is possible to prevent the LED from being left in a state where a voltage is generated at the output terminal after the LED is turned off.

  The LED lighting device of the present invention includes the above-described LED power supply device and an LED. Thereby, it is possible to provide an LED lighting device with improved safety when replacing or inspecting an appliance when an abnormality occurs such as when there is no load.

It is a figure which shows the LED lighting apparatus containing the LED power supply device by the 1st Embodiment of this invention. It is a figure which shows the other example of the electric current detection part of FIG. It is a figure explaining operation | movement of the LED power supply device by 1st Embodiment. It is a figure explaining operation | movement of the LED power supply device by 1st Embodiment. It is a figure which shows the LED lighting apparatus containing the LED power supply device by the 2nd Embodiment of this invention. It is a figure which shows one modification of the structure for the power supply voltage generation in each embodiment.

Embodiment 1. FIG.
In FIG. 1, the circuit block diagram of the LED lighting apparatus 3 containing the LED power supply device 1 which concerns on embodiment of this invention is shown. The LED lighting device 3 includes an LED power supply device 1 and an LED 2. The LED power supply device 1 has input terminals T1 and T2 and output terminals T3 and T4. The power supply voltage from the AC power supply AC is input to the input terminals T1 and T2, and the DC output from the output terminals T3 and T4 is supplied to the LED2. Is done. The LED 2 may be an LED module composed of a plurality of LEDs connected in series, and both ends of the LED 2 are connected to the output terminals T3 and T4.

  The LED power supply device 1 includes an input circuit 10, a switching power supply circuit 20, a no-load detection unit 30, a current detection unit 35, a switch unit 40, and a control unit 50. In the description of the present specification, it is convenient for each circuit or component to belong to which block, and the present invention is not bound thereto.

  The input circuit 10 includes a full-wave rectifier 11 and a capacitor 12, and further includes a current fuse, a noise filter, and the like as necessary. In the input circuit 10, the full-wave rectifier 11 is formed of a diode bridge, the input voltage from the AC power supply AC is full-wave rectified by the full-wave rectifier 11, and the full-wave rectified output is input to the switching power supply circuit 20.

  The switching power supply circuit 20 includes a switching element 21, a transformer 22, a diode 23, and a smoothing capacitor 24. The switching power supply circuit 20 is formed of an insulating flyback converter, and constitutes a so-called one-converter type flyback step-down circuit having a power factor improving function.

  In the switching power supply circuit 20, energy is accumulated by the primary winding N <b> 1 of the transformer 22 during the on period of the switching element 21, and the energy passes through the diode 23 from the secondary winding N <b> 2 side of the transformer 22 during the off period of the switching element 21. Thus, the smoothing capacitor 24 is charged. The step-down ratio is determined by the turn ratio of the secondary winding N2 to the primary winding N1, and the output current is determined by the ON duty (ON width) in the PWM control of the switching element 21. In the following description, the voltage of the smoothing capacitor 24 of the switching power supply circuit 20 (voltage applied to the no-load detection unit 30 described later) is referred to as “power supply output voltage”, and the voltage between the output terminals T3 and T4 is referred to as “device output”. It is called “voltage”. Further, a current passing through a current detection unit 35 described later is referred to as “power supply output current”, and a current that returns from the output terminal T3 to the output terminal T4 is referred to as “device output current”.

  The no-load detection unit 30 includes a voltage dividing circuit including voltage detection resistors 31 and 32 made of high resistance elements, and is connected in parallel to the output terminal of the switching power supply circuit 20. A divided value of the power supply output voltage detected by the no-load detection unit 30 (hereinafter referred to as “voltage detection value”) is input to the control unit 50.

  The current detection unit 35 includes a current detection resistor 36 made of a low resistance element, and is connected in series to the output terminal of the switching power supply circuit 20, that is, inserted into the path of the power supply output current. A voltage conversion value (hereinafter referred to as “current detection value”) of the power supply output current detected by the current detection unit 35 is input to the control unit 50.

  The switch unit 40 includes a switch element 41 such as a MOSFET and is connected in parallel to the output terminals T3 to T4. When the switch element 41 is turned on by a signal from the control unit 50, the output terminals T3-T4 are short-circuited.

  The control unit 50 includes a PWM control circuit 51, a starting resistor 52, a diode 53, a photocoupler 54, an output control circuit 55, and a diode 56. The control unit 50 is supplied with power according to the driving of the switching power supply circuit 20, and based on the detection results from the no-load detection unit 30 and the current detection unit 35 described above, the switching element 21 and the switch unit 40 of the switching power supply circuit 20. The operating state of the switch element 41 is controlled.

  The PWM control circuit 51 includes an input unit Vcc, an input unit FB, an output unit OUT, and a ground unit GND, and includes, for example, a driver IC. The input unit Vcc is connected to the high potential output terminal of the full-wave rectifier 11 via a starting resistor 52 and connected to the auxiliary winding N3 of the transformer 22 via a diode 53. As a result, the input unit Vcc is supplied with a small amount of current from the full-wave rectified output when the PWM control circuit 51 is activated, and after the activation, the power generated in the auxiliary winding N3 as the switching element 21 is driven is controlled by the control power supply. Supplied as Thereby, the control power supply after starting of the PWM control circuit 51 is ensured, and the operation is continued. The control power source is assumed to be a constant voltage by a constant voltage circuit (not shown) such as a smoothing circuit in the PWM control circuit 51.

  The input unit FB is connected to the output terminal of the photocoupler 54, and the output unit OUT is connected to the gate terminal of the switching element 21. The PWM control circuit 51 determines the pulse width (on duty) of the gate signal output from the output unit OUT according to the level of the signal input from the input unit FB, and performs PWM control of the switching element 21.

  The photocoupler 54 includes a photodiode on the input side and a phototransistor on the output side. The photodiode is connected to the output unit AMP of the output control circuit 55, and the phototransistor is connected to the input unit FB of the PWM control circuit 51. In the photocoupler 54, signal transmission from the output control circuit 55 having a different reference potential to the PWM control circuit 51 is performed by photoelectric conversion from a photodiode to a phototransistor.

  The output control circuit 55 includes an input unit Vcc, an input unit VSNS, an input unit ISNS, an output unit AMP, an output unit SW1, and a ground unit GND, and is configured by a microcomputer and / or an analog circuit. The input unit Vcc is connected to the auxiliary winding N4 of the transformer 22 via a diode 56. Thereby, the electric power generated in the auxiliary winding N4 as the switching element 21 is driven is supplied as a control power source. The control power source is assumed to be constant voltage by a constant voltage circuit (not shown) such as a smoothing circuit in the output control circuit 55. A voltage detection value from the no-load detection unit 30 is input to the input unit VSNS, and a current detection value from the current detection unit 35 is input to the input unit ISNS.

  In the output control circuit 55, an error between the current detection value input from the input unit ISNS and a preset current target value is amplified by an error amplifier (not shown), and an error amplification signal is output from the output unit AMP. . The error amplification signal is input to the input unit FB of the PWM control circuit 51 via the photocoupler 54, and the PWM control circuit 51 determines the ON width in the PWM control in a direction to eliminate the error indicated by the error amplification signal. That is, the control unit 50 operates so that the ON width is decreased when the current detection value is larger than the current target value, and is increased when the current detection value is smaller than the current target value. As a result, feedback control (constant current control) is performed so that the detected current value matches the target current value, that is, the power supply output current is constant at the target value.

  In the output control circuit 55, a comparator (not shown) compares the voltage detection value input from the input unit VSNS with a preset voltage threshold value, and if the voltage detection value exceeds the voltage threshold value, A forced short circuit signal is output. The switch element 41 is turned on by this forced short circuit signal, and the output terminals T3-T4 are forcibly shorted. This prevents the device output voltage from being generated in a no-load state.

  Here, it is preferable that the output control circuit 55 reduces the power supply output current when the switch element 41 is conducting. Thereby, in the forced short circuit state of T3-T4, the heat_generation | fever of each component of the switching power supply circuit 20 and the switch element 41 can be reduced. The reduction range of the power supply output current is allowed to the extent that the control power supply of the control unit 50 (PWM control circuit 51 and output control circuit 55) can be secured by driving the switching power supply circuit 20.

  The power supply output current may be reduced by reducing the current target value in the output control circuit 55 or by increasing the combined resistance value of the current detection unit 35. According to the configuration in which the combined resistance value of the current detection unit 35 is increased when no load is detected, the current detection accuracy when the current is reduced can be maintained, and the circuit operation when the power supply output current is reduced can be further stabilized.

  FIG. 2 shows an example of a configuration for increasing the combined resistance value of the current detection unit 35. The current detection unit 35 includes current detection resistors 36a and 36b and a switch element 37 such as a MOSFET, and the current detection resistor 36a and a series circuit of the current detection resistor 36b and the switch element 37 are connected in parallel. The output control circuit 55 has an output unit SW2, and the logic of the output signal from the output unit SW2 is set to high during normal lighting to turn on the switch element 37. When no load is detected (forced short circuit), the output unit The logic of the output signal from SW2 is set to low (or the signal output is stopped), and the switch element 37 is turned off. As a result, the current detection resistors 36a and 36b are connected in parallel during normal lighting, and the current detection resistor 36b is disconnected during no-load detection, and the combined resistance value of the current detection unit 35 increases.

  By appropriately selecting the resistance value of the current detection resistors 36a and 36b and the reduction width of the power supply output current, the power supply output current is simply increased by increasing the combined resistance value in the current detection unit 35 without changing the current target value. Can be reduced. For example, when the power supply output current at the time of forced short circuit is ½ of the power supply output current at the time of normal lighting, the resistance values of the current detection resistors 36a and 36b are made equal to the combined resistance value at the time of normal lighting. Thus, the combined resistance value at the time of forced short circuit may be doubled. Note that, when the switch element 41 is forcibly short-circuited, the current target value may be reset according to the combined resistance value of the current detection resistors 36a and 36b and the reduction range of the power supply output current. Further, in the current detection unit 35, one current detection resistor and a parallel circuit of the other current detection resistor and the switch element 37 may be connected in series. Also in this case, the ON / OFF logic of the switch element 37 is the same as in FIG.

  3A and 3B are timing charts of the output short-circuit operation. FIG. 3A shows the output voltage and the operating state of the switch element 41. Regarding the output voltage, the device output voltage is indicated by a solid line, and the power supply output voltage is indicated by a broken line. FIG. 3B shows the power supply current output and the operating state of the switch element 41. It is assumed that the normal lighting operation is performed until time t1, and that power supply output voltage≈device output voltage = Vn and power supply output current = In.

  It is assumed that at t1, the LED power supply 1 is in a no-load state because the LED2 is disconnected or the LED2 is removed from the LED power supply 1. Due to the occurrence of a no-load condition, the power supply output current becomes zero, and the power supply output voltage and the device output voltage rise.

  When the power supply output voltage reaches the voltage threshold Vth immediately after t1, the output control circuit 55 outputs a forced short circuit signal to turn on the switch element 41. As a result, as shown in FIG. 3A, the device output voltage becomes substantially zero (including the voltage drop due to the on-resistance of the switch element 41), and the power supply output voltage is very much equivalent to the voltage drop of the current detection resistor 36 and the like. Low voltage. Note that the output control circuit 55 invalidates the comparison between the voltage detection value and the voltage threshold value and maintains the ON state of the switch element 41 after outputting the forced short circuit signal.

  Here, in the output control circuit 55, as shown in FIG. 3B, the power supply output current is reduced so that the power supply output current becomes a current (Is) at the time of forced short circuit that is lower than that during normal lighting (In). As a result, the protection state in which the device output voltage is substantially zero and the power supply output current is Is is maintained.

  As described above, according to the present embodiment, when the LED power supply device 1 becomes unloaded, the output terminal thereof is forcibly short-circuited. No voltage is generated and the control power supply can be secured by driving the switching power supply circuit 20 for allowing the power supply output current to flow, and the short circuit state (protection state) can be continued. Thereby, the safety | security at the time of the instrument replacement | exchange at the time of abnormality in the LED power supply device 1 or the LED lighting device 3, an inspection, etc. improves. Moreover, heat generation of the circuit components can be prevented by reducing the power supply output current when the output is forcibly short-circuited.

Embodiment 2. FIG.
In the first embodiment, the configuration in which the device output is forcibly short-circuited when a no-load state occurs is shown. In the present embodiment, however, a configuration in which a forced short-circuit of the output can be recognized by the user is shown. FIG. 4 shows a circuit configuration diagram of the LED lighting device 3 including the LED power supply device 1 of the present embodiment. The present embodiment is the same as the first embodiment shown in FIG. 1 except for the configuration of the switch unit 40, and thus a duplicate description is omitted.

  In the present embodiment, the switch unit 40 includes a series circuit of a switch element 41 and an auxiliary LED 42. That is, a series circuit of the switch element 41 and the auxiliary LED 42 is connected in parallel to the output terminals T3-T4. It is assumed that the auxiliary LED 42 is disposed so as to be visible from the outside of the housing of the LED power supply device 1. When the switch element 41 is forcibly short-circuited when no load is detected, the auxiliary LED 42 connected in series to the switch element 41 emits light. Therefore, an abnormality such as an LED disconnection has occurred, and the LED power supply 1 is powered. It is possible to notify the user that it has been inserted. Note that only a device output voltage (for example, several volts) corresponding to the voltage drop of the auxiliary LED 42 is generated between the output terminals T3 and T4.

  Further, the power supply output current may be controlled within a range in which the control power supply can be secured by driving the switching power supply circuit 20 to change the light emission state of the auxiliary LED 42. For example, the light emission intensity of the auxiliary LED 42 may be changed by changing the current target value periodically or randomly. Further, in the current detection resistor switching configuration as shown in FIG. 2, the light emission intensity of the auxiliary LED 42 can be changed by periodically turning on and off the switch element 37. In this way, by changing the light emission intensity of the auxiliary LED 42, the user is informed that an abnormality has occurred and the LED power supply device 1 when the LED power supply device 1 or the LED lighting device 3 is replaced or inspected. It can be recognized more intuitively that the power is turned on.

<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.

-Modification of Circuit Configuration of Switching Power Supply Circuit 20 In each of the above embodiments, a so-called one-converter type isolated flyback converter is shown as the switching power supply circuit 20, but the switching power supply circuit 20 is another type of step-down converter. There may be. For example, the switching power supply circuit 20 may be a circuit including a power factor correction circuit and a flyback converter circuit. In this case, the auxiliary windings N3 and N4 only have to be provided in the transformer constituting the flyback converter circuit or the coil constituting the power factor correction circuit. The switching power supply circuit 20 may be a circuit including a power factor correction circuit and a non-insulated step-down chopper circuit. In this case, the auxiliary windings N3 and N4 only have to be provided in the choke coil constituting the step-down chopper circuit. Alternatively, in the case of such a non-insulated converter, the PWM control circuit 51 and the output control circuit 55 all have the same reference potential (ground), so that all control power supplies can be supplied from one auxiliary winding provided in the choke coil. May be generated.

-Modification of control power generation configuration In each of the above embodiments and modifications, the control power is generated from the auxiliary winding of the inductor element such as the transformer 22 as a configuration for generating the control power according to the driving of the switching power supply circuit 20. However, the configuration for generating the control power supply is not limited to this. For example, as shown in FIG. 5, the control power source on the PWM control circuit 51 side may be generated from a snubber circuit connected in parallel to the switching element 21. The snubber circuit includes a capacitor 25 and a diode 26 connected in series. The capacitor 25 is connected to the drain terminal of the switching element 21 and the anode of the diode 26 is connected to the source terminal (reference potential). The connection point between the capacitor 25 and the diode 26 is connected to the anode of the diode 52. Thereby, the pulsed voltage generated in the capacitor 25 during the operation of the switching power supply circuit 20 can be used for generation of the control power supply.

-Modification of No-Load Detection Unit 30 In each of the above embodiments, the voltage dividing circuit that detects the divided value of the power supply output voltage is shown as the no-load detection unit 30, but the no-load detection unit is not limited to this. For example, the no-load detection unit 30 may be an illuminance sensor. In this case, when the illuminance sensor is arranged in the vicinity of the LED 2 and the illuminance exceeding the predetermined value is not detected even though the switching power supply circuit 20 is driven, the output control circuit 55 detects that there is no load. You may be made to do. Further, the no-load detection unit may be configured by the current detection unit 35. In this case, the output control circuit 55 may detect that there is no load when the detection current cannot be obtained even though the switching power supply circuit 20 is driven. In this case, as in the case where the no-load detection unit 30 detects the power supply output voltage, the output control circuit 55 disables the no-load detection by the current detection unit 35 after outputting the forced short-circuit signal and turns on the switch element 41. The state shall be maintained.

-Modification regarding the operation timing of the switch part 40 In each said embodiment, although the switch element 41 of the switch part 40 was turned on at the time of no-load detection, the operation | movement completion | finish of LED power supply device 1 (namely, light extinction) Alternatively, the switch element 41 may be turned on. Thereby, it is possible to prevent the smoothing capacitor 24 from being left in a charged state after the LED is turned off. In this way, the switch element 41 can serve both as a protection operation when there is no load and a residual voltage discharge operation when the light is extinguished.

-Modification of current control in control unit 50 In each of the above-described embodiments, the configuration in which the power supply output current is feedback-controlled in the control unit 50 has been described, but the power supply output current may be subjected to feedforward control. In this case, the current detection unit 35 may be omitted, but it is preferable that some impedance element is included in the path in order to stabilize the power supply output current at the time of a forced short circuit.

1 LED power supply 2 LED
3 LED lighting device 20 switching power supply circuit 30 no-load detection unit 35 current detection unit 36, 36a, 36b current detection resistor 40 switch unit 41 switch element 42 auxiliary LED
50 Control unit T3, T4 Output terminal

Claims (6)

An LED power supply,
An output terminal connected to both ends of the LED;
A switching power supply circuit capable of applying a DC voltage to the output terminal;
A no-load detection unit for detecting the no-load state of the output terminal;
A switch unit having a switch element connected in parallel to the output terminal;
An LED power supply apparatus comprising: a control unit that operates by a control power supply that is supplied according to driving of the switching power supply circuit, and that causes the switch element to conduct when the no-load state is detected. 2. The LED power supply device according to claim 1, wherein the control power supply can be secured by driving the switching power supply circuit with the output current of the switching power supply circuit when the control unit is conducting the switch element. 3. configured LED power supply to the low reduction in a range. The LED power supply device according to claim 2, further comprising a current detection unit including a plurality of current detection resistors inserted in an output current path of the switching power supply circuit,
The control unit controls the output current of the switching power supply circuit so that the current detected by the current detection unit matches a current target value, and the combined resistance value of the current detection unit when the switch element is turned on LED power supply configured to increase.   4. The LED power supply device according to claim 1, wherein the switch unit includes an auxiliary LED connected in series to the switch element. 5.   5. The LED power supply device according to claim 1, wherein the control unit is configured to make the switch element conductive even when the LED is turned off. 6.   An LED lighting device comprising: the LED power supply device according to any one of claims 1 to 5; and the LED.

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