JP2012204317A - Led lighting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To protect a lighting device from abnormal temperature rise due to an abnormal load, while preventing the malfunction of protection operation.SOLUTION: An LED lighting device to perform lighting control of an LED 19 comprises: a drive circuit 14 which controls on/off of a switching element 15; voltage detection circuits 21 and 22 which detect an output-end voltage; first comparison means 23 which compares an output voltage value obtained from the voltage detection circuits with a first reference voltage; second comparison means 24 which compares the output voltage value obtained from the voltage detection circuits with a second reference voltage lower than the first reference voltage; and control means 20 which controls the drive circuit so that it performs protection operation when one of the first and second comparison means notifies that the output voltage value exceeds the first or second reference voltage. If the output voltage value continues to exceed the second reference voltage for a predetermined period of time, the second comparison means 24 notifies the control means 20 of the excess.

Description

  The present invention relates to output abnormality detection and protection means for an LED lighting device for illumination.

  In recent years, light-emitting diodes (LEDs) have begun to spread in place of conventional incandescent bulbs and fluorescent lamps. LEDs have the characteristics of low power consumption and long life, and research and development of LED lighting devices for lighting LEDs are being carried out by various companies.

JP 2007-234414 A

  The LED lighting device turns on an LED by current-limiting control (constant current driving) so that a desired current flows through a load (LED). On the other hand, the LED element itself exhibits a substantially constant voltage characteristic, and the terminal voltage is substantially constant.

  However, in the LED lighting device, the output voltage may increase instantaneously in response to a short-time load impedance fluctuation (particularly an increase) such as output connector insertion / removal, LED removal, or contact failure. This is due to constant current driving of the LED as described above. In such a case, the LED element or the lighting device may be damaged.

  Also, if the load connected to the lighting device is wrong, that is, if an LED outside the proper load impedance range is connected, or if the load impedance is higher than the desired impedance due to aging of the LED element, etc., the power consumption is desired It is assumed that the temperature of the lighting device itself rises and damages internal elements, and the temperature of the lamp also rises.

  In order to deal with these problems, it is common to detect that the desired voltage has been exceeded by an output voltage circuit and to perform a protection operation or a notification operation. However, the former (such as connector insertion / removal) protection requires immediate response immediately after detection, while the latter (such as incorrect load use) requires protection even when the voltage increases slightly relative to the rated output voltage. However, since a thermal malfunction is assumed, there is no problem even if the time from the detection to the protection operation is set longer than the former. If the detection value is set to the latter voltage value in order to satisfy both, a protective operation may occur in a transient operation in a normal use category such as power-on or instantaneous power failure.

  If the detection voltage is set to a voltage that is high enough to prevent malfunction due to protection malfunctions, the temperature will be increased against incorrect load connections and load impedance increases due to deterioration of LEDs and other components connected as loads. The target protection range becomes high.

  An embodiment of the present invention aims to prevent a malfunction of a protective operation and to protect a lighting device from an abnormal temperature rise due to an abnormal load.

  In order to counter the above-described problems, in the embodiment, at least two detection voltage values are set, and in a mode in which the connector is instantaneously destroyed such as connector insertion / removal, the protective operation is performed immediately after detection, and an erroneous load is connected. When a malfunction is assumed, the time until the protection operation is executed is set longer than the former. In addition, the first detection value in which the former detection voltage is set to a high voltage that does not cause malfunction, and the second detection in order to perform overvoltage protection with the lowest detection value assuming the connection of the latter erroneous load. Set the value.

  That is, an LED lighting device according to an embodiment converts an alternating current power supply voltage into a direct current power supply, supplies a direct current from the direct current power supply to an LED connected to an output terminal via a switching element, and controls the lighting of the LED. An LED lighting device for controlling on / off of the switching element, a voltage detection circuit for detecting an output terminal voltage, and comparing an output voltage value obtained from the voltage detection circuit with a first reference voltage First comparison means, second comparison means for comparing an output voltage value obtained from the voltage detection circuit with a second reference voltage lower than the first reference voltage, and one of the first and second comparison means, Control means for controlling the drive circuit to perform a protection operation when notified that the output voltage value exceeds the first or second reference voltage, and the second comparison Stage, a state in which the output voltage value exceeds the second reference voltage and notifies to the control means and continues for a predetermined time.

  It is possible to prevent malfunction of the protective operation and protect the lighting device from an abnormal temperature rise due to an abnormal load.

It is a block diagram which shows the structure of the LED lighting device which concerns on 1st Embodiment. It is a time chart which shows the 1st effect | action of 1st Embodiment. It is a time chart which shows the 2nd effect | action of 1st Embodiment. It is a block diagram which shows the structure of the LED lighting device which concerns on 2nd Embodiment. It is a time chart which shows the effect | action of 2nd Embodiment. It is a block diagram which shows the structure of the LED lighting device which concerns on 3rd Embodiment.

The LED lighting device of the first embodiment converts an AC power supply voltage to a DC power supply, supplies a DC current from the DC power supply to a LED connected to an output terminal via a switching element, and controls the lighting of the LED. An LED lighting device for controlling on / off of the switching element, a voltage detection circuit for detecting an output terminal voltage, and comparing an output voltage value obtained from the voltage detection circuit with a first reference voltage First comparing means for comparing the output voltage value obtained from the voltage detection circuit with a second reference voltage lower than the first reference voltage;
Control means for controlling the drive circuit to perform a protection operation when notified from one of the first and second comparison means that the output voltage value exceeds the first or second reference voltage; And the second comparison means notifies the control means when the output voltage value exceeds the second reference voltage for a predetermined time.

  The LED lighting device according to the second embodiment is the LED lighting device according to the first embodiment, and the protection operation is reduction of output to the LED, stop of output, or blinking.

  The LED lighting device according to the third embodiment is the LED lighting device according to the first embodiment, and the first reference voltage is set to a voltage corresponding to a rated output voltage.

  An LED lighting device according to a fourth embodiment is the LED lighting device according to any one of the first to third embodiments, and a third output voltage value obtained from the voltage detection circuit is lower than a rated voltage. Compared with a reference voltage, it further comprises third comparison means for notifying the control means when the output voltage falls below the third reference voltage.

  The LED lighting device according to the fifth embodiment is the LED lighting device according to any one of the first to fourth embodiments, and includes at least a means for changing the second reference value when the dimming operation is performed. It is characterized by doing.

  Hereinafter, an embodiment of an LED lighting device according to the present invention will be described with reference to the drawings.

[First Embodiment]
FIG. 1 is a block diagram showing the configuration of the LED lighting device according to the first embodiment.

  The DC power supply voltage V <b> 1 is generated from the commercial AC power supply 11 using the full-wave rectifier circuit 12 and the filter capacitor 13. The current supplied from the full-wave rectifier circuit 12 is supplied to the capacitor 18 and the LED 19 via the switch element 15 (NchFET transistor) and the coil 17. The LED 19 is connected to the present lighting device via the output terminal 19a, the anode is connected to the coil 17, and the cathode is connected to the ground. The LED 19 includes a plurality of LED elements connected in series and parallel, for example.

  The drive circuit 14 supplies a gate signal for ON / OFF control of the switch element 16 to the gate of the switch element 16. The drive circuit 14 is an integrated circuit (IC) in which an internal circuit is formed on one chip, for example. The on / off controlled current is stepped down by the inductance of the coil 17, smoothed by the capacitor 18, flows through the LED 19, and causes the LED 19 to emit light. The voltage V2 between the output terminals 19a of the LED 19 is, for example, about 3V to 150V depending on the number of LED elements connected in series. The diode 16 is a flywheel diode that provides a current path for the coil 17 when the switch element 15 is turned off.

  The voltage V2 is divided by the voltage dividing resistors 21 and 22 into the voltage V3. The comparison circuit 23 includes an operational amplifier 26, a feedback resistor 25, and a reference power source 23a that generates a reference voltage Vref1. The reference voltage Vref1 is input to the inverting input terminal of the operational amplifier 26, and the voltage V3 is input to the non-inverting input terminal. The output voltage V4 of the comparison circuit 23 is applied to the resistor 37 via the diode 36. The comparison circuit 23 detects an overvoltage that occurs instantaneously, for example, when the connector of the LED 19 is connected or disconnected while the power is on, or when the LED 19 is removed from the lighting device. . The reference voltage Vref1 is set to a voltage corresponding to a voltage equal to or higher than the rated output voltage of the lighting device.

  The comparison circuit 24 includes an operational amplifier 28, a feedback resistor 27, and a reference power supply 24a that generates a reference voltage Vref2. The reference voltage Vref2 is input to the non-inverting input terminal of the operational amplifier 28, and the voltage V3 is input to the inverting input terminal. The reference voltage Vref2 is a voltage lower than the reference voltage Vref1 of the comparison circuit 23. The comparison circuit 24 detects a load abnormality. This load abnormality includes an improper LED (incorrect load) whose load impedance is larger than an appropriate value and an LED (abnormal load) whose load impedance has increased due to life (deterioration).

  The output voltage of the comparison circuit 24 is applied to the anode of the Zener diode 29 and the base of the transistor 31. The emitter of the transistor 31 is connected to the power supply Vcc via the resistor 30, and the anode of the Zener diode 29 is directly connected to the power supply Vcc. The collector of the transistor 31 is connected to the cathode of the Zener diode 34 and one terminal of the capacitor 32. The anode of the Zener diode 34 is grounded via a diode 35 and a resistor 37, and the other terminal of the capacitor 32 is also grounded. The zener diode 29, the resistor 30, the transistor 31, the capacitor 32, the diode 35, and the resistor 37 constitute a delay circuit 33.

  Next, the operation of the lighting apparatus according to the first embodiment will be described in detail.

  FIG. 2 is a time chart showing the first operation of the first embodiment, where (a) shows the LED terminal voltage V2 in the circuit of FIG. 1, (b) shows the output voltages V4 and V7 of the comparison circuit 23, and (c). Indicates the waveform of the control circuit 20 output voltage V8.

  The waveform of the voltage V2 in FIG. 2A indicates an overvoltage that occurs instantaneously. When an overvoltage exceeding Vref1 is generated as the voltage V2, this overvoltage is detected by the comparison circuit 23 as shown in FIG. The control circuit 20 normally outputs a PWM wave for lighting the LED 19 with a desired brightness to the drive circuit 14, but determines that the logic 1 input of the voltage V7 is an overvoltage occurrence and causes the drive circuit 14 to perform LED protection operation. Command. In this example, the output of the PWM wave is stopped as shown in FIG. 2C, and as a result, the LED 19 is turned off. As another example of the protection operation, the LED output may be reduced or blinked. By blinking, the user can be notified that an abnormality has occurred.

  FIG. 3 is a time chart showing the second operation of the first embodiment, where (a) shows the LED terminal voltage V2 in the circuit of FIG. 1, (b) shows the output voltage V5 of the comparison circuit 24, and (c) shows The collector voltage V6 of the transistor 31, (d) is the input voltage V7 of the control circuit 20, and (e) is the waveform of the output voltage V8 of the control circuit 20.

  The waveform of the voltage V2 in FIG. 3A shows the LED terminal voltage V2 that is higher than normal and is generated when an LED having a load impedance larger than an appropriate value is connected to the lighting device. When the LED terminal voltage V2 exceeds the reference voltage Vref2, the comparison circuit 24 outputs logic 0 and the transistor 31 is turned on. At this time, due to the action of the Zener diode 29, the capacitor 32 is charged with a constant voltage, and the terminal voltage V6 of the capacitor 32 rises as shown in FIG.

  When the terminal voltage V6 of the capacitor 32 exceeds the Zener voltage Vz of the Zener diode 29, the charge charged in the capacitor 32 flows through the resistor 37 via the Zener diode 34 and the diode 35. As a result, the input voltage V7 of the control circuit 20 becomes logic 1 as shown in FIG. When the terminal voltage V6 of the capacitor 32 drops below the zener voltage Vz due to this discharge, the input voltage V7 of the control circuit 20 becomes logic zero. As shown in FIG. 3E, the control circuit 20 responds to the fall of the input voltage V7 with a signal for executing a protection operation (stopping PWM signal output or reducing or blinking the output of the PWM signal). Output. In the present embodiment, when the state in which the output voltage value V2 to the LED 19 exceeds the reference voltage Vref2 continues for a predetermined time t1 or longer, the excess state is notified to the control circuit 20 and the protection operation is performed.

  In this embodiment, an operational amplifier is used as an example, and the reference value is divided into Vref1 and Vref2, and the abnormal voltage is determined. However, the signal may be taken in by a microcomputer or the like, and a binary judgment value may be prepared inside the microcomputer and operated in the same manner.

[effect]
As described above, according to the present embodiment, the apparatus can be protected from an overvoltage that occurs instantaneously and an abnormal temperature rise due to an erroneous load or an abnormal load. That is, it is possible to take countermeasures against abnormal loads without using components that are highly resistant to electrical and thermal reasons.

[Second Embodiment]
Next, an LED lighting device according to a second embodiment will be described with reference to the drawings.

  FIG. 4 is a block diagram showing the configuration of the LED lighting device according to the second embodiment. The same components as those in the first embodiment in FIG. 1 are denoted by the same reference numerals, and detailed description thereof is omitted.

  In the second embodiment, a low voltage detection circuit 40 is provided in addition to the first embodiment of FIG. When an LED having a load impedance lower than an appropriate value is connected to the lighting device, the LED does not emit light at a desired brightness because of constant current driving. The low voltage detection circuit 40 detects that an LED having a load impedance lower than an appropriate value is connected and a short circuit of the output terminal.

  The low voltage detection circuit 40 includes an operational amplifier 41, a reference voltage source 41a that generates a reference voltage Vref3, a resistor 42, and a diode 43. A voltage V3 obtained by dividing the terminal voltage of the LED 19 is input to the non-inverting terminal of the operational amplifier 41. The reference voltage Vref3 is a voltage corresponding to a voltage lower than the rated voltage, for example. The reference voltage Vref3 is input to the inverting terminal of the operational amplifier 41. The output terminal of the operational amplifier 41 is connected to the base of the transistor 31 through the resistor 42 and the diode 43.

  Next, the operation of the second embodiment will be described in detail.

  5A and 5B are time charts showing the operation of the second embodiment, wherein FIG. 5A is a voltage V3 obtained by dividing the LED terminal voltage V2 in the circuit of FIG. 4, and FIG. 5B is an output voltage V9 of the operational amplifier 41. ) Is the terminal voltage V6 of the capacitor 32, (d) is the input voltage V7 of the control circuit 20, and (e) is the waveform of the output voltage V8 of the control circuit 20.

  When an LED whose output terminal is short-circuited or whose load impedance is lower than an appropriate value is connected, the terminal voltage V2 of the LED decreases, and the divided voltage V3 decreases below the reference voltage Vref3 as shown in FIG. V9 falls from logic 1 to logic 0 as shown in FIG. 5B, and as a result, the transistor 30 is turned on. Thereafter, as in the first embodiment of FIG. 3, due to the action of the Zener diode 29, the capacitor 32 is charged with a constant voltage, and the terminal voltage V6 of the capacitor 32 rises as shown in FIG. When the terminal voltage V6 of the capacitor 32 exceeds the Zener voltage Vz, a signal of logic 1 is input to the control circuit 20 as shown in FIG. 5D, and the control circuit 20 performs a protection operation (PWM signal output) on the drive circuit 14. A signal for executing stop or output reduction or blinking) is output. In FIG. 5E, the output of the PWM signal to the drive circuit 14 is stopped.

[effect]
According to the second embodiment, damage to the device due to a short circuit can be prevented, and the user can be informed that an LED having a small power capacity has been connected.

[Third Embodiment]
Next, an LED lighting device according to a third embodiment will be described with reference to the drawings.

  FIG. 6 is a block diagram showing the configuration of the LED lighting device according to the third embodiment. The same components as those in the first embodiment of FIG. 1 are denoted by the same reference numerals, and detailed description thereof is omitted.

  In the third embodiment, in addition to the first embodiment of FIG. 1, a reference voltage variable circuit 50 that varies the reference voltage of the detection voltage according to the dimming level is provided. The reference voltage variable circuit 50 includes a resistor 51, a full-wave rectifier circuit 52, a phototocoupler 53, a resistor 54, and a capacitor 55.

  A PWM dimming signal (AC) input from a control unit (not shown) of the lighting device is converted into a DC current by the resistor 51 and the full-wave rectifier circuit 52, and drives the photocoupler 53 (LED 53a). The full-wave rectifier circuit 52 is insulated from the lighting device body by the photocoupler 53, and a direct current corresponding to the PWM dimming signal flows through the phototransistor 53 b of the photocoupler 53.

  In the RC integration circuit 56 constituted by the resistor 54 and the capacitor 55, the PWM duty is converted into a DC voltage level, and the dimming signal and the level of the safety circuit operation are varied. When the output current to the LED 19 is decreased by dimming, the Vf (Forward Voltage) in the LED decreases accordingly, so the detection voltage (Vref2 in the above-described embodiment) is set to correspond to this. Reduce.

[effect]
According to the third embodiment, in the LED lighting device having a dimming function, it is possible to appropriately vary the reference voltage for detecting an abnormal load according to the dimming level.

  The above description is an embodiment of the present invention, and does not limit the apparatus and method of the present invention, and various modifications can be easily implemented. For example, various inventions can be configured by appropriately combining a plurality of constituent elements disclosed in the embodiment.

  DESCRIPTION OF SYMBOLS 11 ... Commercial alternating current power supply, 12, 52 ... Full wave rectifier circuit, 13, 18, 32 ... Capacitor, 14 ... Drive circuit, 15 ... Switching element, 16, 35, 43 ... Diode, 20 ... Control circuit, 29, 34 ... Zener diode, 19 ... LED, 23, 24 ... operational amplifier, 53 ... photocoupler.

Claims (5)

An LED lighting device that converts an AC power supply voltage into a DC power supply, supplies a DC current from the DC power supply via a switching element to an LED connected to an output end, and controls the lighting of the LED,
A drive circuit for controlling on / off of the switching element;
A voltage detection circuit for detecting the output terminal voltage;
First comparison means for comparing an output voltage value obtained from the voltage detection circuit with a first reference voltage;
Second comparison means for comparing an output voltage value obtained from the voltage detection circuit with a second reference voltage lower than the first reference voltage;
Control means for controlling the drive circuit to perform a protection operation when notified from one of the first and second comparison means that the output voltage value exceeds the first or second reference voltage; Comprising
The LED lighting circuit according to claim 2, wherein the second comparing means notifies the control means when the output voltage value exceeds the second reference voltage for a predetermined time.   The LED lighting device according to claim 1, wherein the protection operation is output reduction, output stop, or blinking to the LED.   The LED lighting device according to claim 1, wherein the first reference voltage is set to a voltage corresponding to a rated output voltage.   Comparing an output voltage value obtained from the voltage detection circuit with a third reference voltage lower than a rated voltage, and further comprising third comparison means for notifying the control means when the output voltage falls below the third reference voltage. The LED lighting device according to any one of claims 1 to 3.   The LED lighting device according to any one of claims 1 to 4, further comprising means for varying at least the second reference value when the light control operation is performed.

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