Lighting devices and lighting equipment

Abstract

To provide a lighting device for protecting an illumination device, and the illumination device.SOLUTION: A lighting device includes: a regulator circuit including a switching element and a current detection resistor connected in series with the switching element; a power supply circuit which applies a voltage to both ends of a series circuit formed of a light source, the switching element, and the current detection resistor to turn on the light source; and a control unit which adjusts an impedance of the switching element so that the voltage generated in the current detection resistor may be coincident with a target value. When the voltage generated in the current detection resistor exceeds a predetermined first threshold which is higher than the target value, the control unit stops operation of the power supply circuit or the switching element.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a lighting device and an illumination device. [Background technology]

[0002] Patent Document 1 discloses a lighting device that supplies power to a light-emitting element. This lighting device includes a variable voltage source that supplies a variable DC voltage to the light-emitting element, and a transistor that is connected in series with the light-emitting element and controls the current flowing through the light-emitting element. A control circuit receives an instruction regarding the dimming level of the light-emitting element and controls the transistor so that a current corresponding to the received instruction flows through the light-emitting element. The control circuit also controls the variable voltage source so that it outputs a DC voltage that causes a predetermined voltage drop across the transistor. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6928834 Summary of the Invention [Problem to be solved by the invention]

[0004] In Patent Document 1, a transistor connected in series with an LED operates as a linear regulator, and the voltage applied to the LED is kept constant, thereby suppressing ripple in the LED current. In Patent Document 1, a transistor in a high-side buck converter circuit, a light-emitting element, a transistor in a linear regulator circuit, and a resistor element for current detection are connected in series. In this circuit configuration, if a failure occurs in the transistor in the buck converter circuit or the transistor in the linear regulator circuit due to some event, an excessive current may flow in the circuit.

[0005] The present disclosure has been made to solve the above-mentioned problems, and has an object to provide a lighting device and a lighting device that can protect the lighting device. [Means for solving the problem]

[0006] A lighting device according to a first disclosure includes a regulator circuit including a switching element and a current detection resistor connected in series with the switching element; a power supply circuit that applies a voltage to both ends of a series circuit formed by the light source, the switching element, and the current detection resistor to turn on the light source; and a control unit that adjusts the impedance of the switching element so that the voltage generated in the current detection resistor matches a target value, and the control unit adjusts the impedance of the power supply circuit when the voltage generated in the current detection resistor exceeds a predetermined first threshold value that is higher than the target value. Road Stop operation When the voltage generated in the switching element exceeds a predetermined second threshold, the operation of the switching element is stopped. do. [Effects of the Invention]

[0008] In the lighting device according to the first disclosure, when the voltage generated in the current detection resistor exceeds the first threshold, the operation of the switching element of the power supply circuit or the regulator circuit stops, thereby protecting the lighting device. In the lighting device according to the second disclosure, when the voltage generated in the switching element exceeds the second threshold, the operation of the switching element of the power supply circuit or regulator circuit stops, thereby protecting the lighting device. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a circuit block diagram of a lighting device according to a first embodiment. [Figure 2] 5A and 5B are diagrams illustrating the operation of the lighting device when a switching element of the regulator circuit according to the first embodiment fails. [Figure 3] 5A and 5B are diagrams illustrating the operation of the lighting device when a switching element of the buck converter circuit according to the first embodiment fails. [Figure 4] FIG. 10 is a circuit block diagram of a lighting device according to a second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] A lighting device and an illumination device according to each embodiment will be described with reference to the drawings. The same or corresponding components are designated by the same reference numerals, and repeated description may be omitted.

[0011] Embodiment 1 1 is a circuit block diagram of an illumination device 100 according to embodiment 1. The illumination device 100 includes a lighting device 50 and a light source 80. The light source 80 has a plurality of LEDs connected in series as light-emitting elements.

[0012] In the lighting device 50, a smoothing capacitor C1 and a buck converter circuit 10 are connected to the output side of a diode bridge DB1. An AC voltage from an AC power source AC is rectified by the diode bridge DB1 and converted into a DC voltage accompanied by a pulsating voltage by the smoothing capacitor C1. The converted voltage is input to the buck converter circuit 10.

[0013] The buck converter circuit 10 includes a switching element Q1, a diode D1, an inductor L1, and a smoothing capacitor C2. The switching element Q1 is, for example, a metal-oxide-semiconductor field-effect transistor (MOSFET). The switching element Q1 has a drain, a source, and a gate.

[0014] A light source 80 and a regulator circuit 20 are connected in series to the output of the buck converter circuit 10. The regulator circuit 20 includes a switching element Q2 and a current detection resistor R1 connected in series with the switching element Q2. The switching element Q2 is, for example, a MOSFET. The buck converter circuit 10 is a power supply circuit that applies a voltage across the series circuit formed by the light source 80, the switching element Q2, and the current detection resistor R1 to turn on the light source 80.

[0015] The control IC 30 is a composite IC including, for example, a microcomputer and a driver. The control IC 30 has a Q1DRV terminal and a Q2DRV terminal for driving the switching elements Q1 and Q2. The Q1DRV terminal and the Q2DRV terminal are connected to the gates of the switching elements Q1 and Q2, respectively. The control IC 30 also has a Vin terminal for detecting the voltage value input to the lighting device 100. A series circuit of resistors R2 and R3 is connected in parallel with the smoothing capacitor C1. The junction of the resistors R2 and R3 is connected to the Vin terminal.

[0016] The control IC 30 has a VOUT terminal for detecting the voltage generated in the switching element Q2 and an IFB terminal for detecting the LED current. The VOUT terminal is connected to the drain of the switching element Q2. The IFB terminal is connected to the connection point between the switching element Q2 and the current detection resistor R1. The control IC 30 also has a VB terminal that serves as the power supply for the driver that drives the switching elements Q1 and Q2, and a VDD terminal that serves as the power supply for the microcontroller. The VB terminal receives the output voltage V1 from the control power supply circuit 40. The VDD terminal receives the output voltage of the step-down circuit 42.

[0017] The control power supply circuit 40 is, for example, a buck converter circuit. The input voltage Vin is stepped down to a predetermined voltage by the control power supply circuit 40. The stepped-down voltage is smoothed by an electrolytic capacitor C3 to generate a power supply voltage V1. The power supply voltage V1 is, for example, 13 V. The control power supply circuit 40 may be another circuit, such as a flyback circuit, as long as it can obtain the desired voltage. The step-down circuit 42 generates a power supply voltage VDD for the control IC 30 from the power supply voltage V1. The step-down circuit 42 is, for example, a regulator circuit. The power supply voltage VDD is, for example, 3.3 V.

[0018] Next, the steady-state operation of the lighting device 100 will be described. When an input voltage Vin is applied from an AC power supply AC, the control power supply circuit 40 and the step-down circuit 42 operate to generate power supply voltages V1 and VDD. When the power supply voltage VDD rises to a voltage at which the control IC 30 can operate, the control IC 30 starts up. The control IC 30 detects the input voltage Vin, and if the detected voltage is a predetermined voltage, it activates the buck converter circuit 10 and the regulator circuit 20.

[0019] The buck converter circuit 10 performs constant voltage operation to maintain the cathode voltage of the light source 80, i.e., the drain voltage of the switching element Q2, at a constant value. Specifically, the control IC 30 detects the drain voltage of the switching element Q2 at the VOUT terminal as the voltage VQ2 generated in the switching element Q2. The control IC 30 compares the voltage VQ2 with a target voltage stored in the control IC 30 and adjusts the PWM (Pulse Width Modulation) signal output from the Q1DRV terminal based on the comparison result. In this way, the control IC 30 controls the buck converter circuit 10 so that the voltage VQ2 generated in the switching element Q2 matches the target voltage.

[0020] The feedback period in this case is set to a value lower than the commercial frequency to improve the power factor. Therefore, the output of the buck converter circuit 10 generates a voltage accompanied by a ripple voltage of the commercial component. In other words, a ripple voltage with a frequency twice that of the AC power supply is superimposed on the output voltage of the buck converter circuit 10. The ripple voltage varies depending on the capacitance of the smoothing capacitor C2. To reduce the ripple voltage to zero, a large-capacity smoothing capacitor C2 is required, and it is not possible to completely eliminate the ripple voltage with a conventional capacitance.

[0021] The regulator circuit 20 performs constant current operation to maintain a constant current flowing through the light source 80. Specifically, the control IC 30 detects the voltage VR1 generated across the current detection resistor R1 connected in series with the light source 80 at the IFB terminal. The control IC 30 compares the voltage VR1 with a target value pre-stored in the control IC 30 and adjusts the level of the output voltage from the Q2DRV terminal based on the comparison result. In this way, the control IC 30 adjusts the impedance of the switching element Q2 so that the voltage VR1 generated across the current detection resistor R1 matches the target value. The impedance of the switching element Q2 absorbs the ripple voltage, thereby controlling the voltage applied to the light source 80 to a constant value. In other words, the LED current is controlled to a constant value.

[0022] Next, the operation when the switching element Q1 or the switching element Q2 has a short-circuit fault or a half-dead fault will be described. First, the operation when the protection of this embodiment is not performed when the switching element Q1 or the switching element Q2 has a fault will be described.

[0023] First, if switching element Q2 fails and impedance drops, voltage VQ2 generated across switching element Q2 falls below the target voltage. This causes control IC 30 to increase the output voltage of buck converter circuit 10. As a result, excessive current flows through light source 80 and regulator circuit 20 compared to steady-state operation. In this case, depending on the failure state of switching element Q2, the components used in lighting device 100, LEDs, and the heat dissipation structure of the fixture, the lighting device 100 may enter various states, such as not lighting at all or lighting at excessive brightness. In particular, if the lighting operation continues, there is a risk of smoke or fire from electronic components or LEDs. Furthermore, there is a risk of the lighting device 100 falling due to deterioration of the fixture holder.

[0024] Next, if switching element Q1 fails and its impedance drops, control IC 30 attempts to maintain a constant current. To achieve this, control IC 30 increases the impedance of switching element Q2, raising the voltage it bears. Losses in switching element Q2 are determined by the product of the LED current and the voltage generated across switching element Q2. This significantly increases losses in switching element Q2 compared to steady-state operation, potentially leading to thermal failure. If switching element Q2 also fails due to thermal failure, there will be no component to limit the main current path. This could potentially lead to the same problem as the failure of switching element Q2 described above.

[0025] Next, the protection operation according to this embodiment will be described. First, the operation when the switching element Q2 fails will be described. FIG. 2 is a diagram illustrating the operation of the lighting device 100 when the switching element Q2 of the regulator circuit 20 according to embodiment 1 fails. During steady state, the voltage VR1 generated across the current detection resistor R1 is controlled to a constant value so that it matches the target value. When the switching element Q2 fails, the impedance of the switching element Q2 becomes uncontrollable and decreases. This causes the voltage VQ2 generated across the switching element Q2 to decrease. At this time, the control IC 30 attempts to increase the output voltage of the buck converter circuit 10, increasing the current flowing through the current detection resistor R1.

[0026] The control IC 30 stores a predetermined first threshold value that is higher than the target value. When the voltage VR1 generated across the current detection resistor R1 exceeds the first threshold value, the control IC 30 stops the output from the Q1DRV terminal and stops the switching element Q1. This stops the operation of the buck converter circuit 10, and current is no longer supplied to the circuits following the switching element Q1. Therefore, the lighting device 100 can be safely shut down.

[0027] Next, the operation when the switching element Q1 fails will be described. Fig. 3 is a diagram illustrating the operation of the lighting device 100 when the switching element Q1 of the buck converter circuit 10 according to the first embodiment fails. During steady state operation, the voltage VQ2 generated across the switching element Q2 is controlled to a constant value so that it matches the target voltage. If the impedance drops due to a failure of the switching element Q1, an excessive voltage is applied to the light source 80 and the regulator circuit 20. In this case, the control IC 30 attempts to perform constant current control on the regulator circuit 20, and the voltage VQ2 generated across the switching element Q2 increases.

[0028] The control IC 30 stores a predetermined second threshold value that is higher than the target voltage. When the voltage VQ2 generated across the switching element Q2 exceeds the second threshold value, the control IC 30 stops the output from the Q2DRV terminal and stops the operation of the switching element Q2. This interrupts the main current path, preventing current from flowing. This allows the lighting device 100 to be safely shut down.

[0029] In this embodiment, a protection threshold is set for the terminal used for steady-state feedback to detect abnormalities. When the voltage VR1 generated across the current detection resistor R1 exceeds a first threshold, the buck converter circuit 10 stops. When the voltage VQ2 generated across the switching element Q2 exceeds a second threshold, the operation of the switching element Q2 stops. This protects the lighting device 100.

[0030] In particular, in this embodiment, when one of the switching elements Q1 and Q2 fails, the operation of the other normal switching element is stopped to shut down the lighting device 100. This allows the lighting device 100 to be protected with precision and maintain safety. However, the present invention is not limited to this, and the control IC 30 may stop the operation of the buck converter circuit 10 or the switching element Q2 when the voltage VR1 exceeds the first threshold or when the voltage VQ2 exceeds the second threshold.

[0031] As a modification of this embodiment, the buck converter circuit 10 may be a different type of power supply circuit. The light-emitting element constituting the light source 80 may be an organic EL. Furthermore, the control IC 30 is not limited to a composite IC; any circuit capable of feedback control and driving a switching element may be used. The control IC 30 may be realized by hardware such as an independent A / D converter, logic circuit, gate array, or D / A converter.

[0032] These modifications can be applied as appropriate to the lighting devices and illumination devices according to the following embodiments. Note that the lighting devices and illumination devices according to the following embodiments have many points in common with embodiment 1, so differences from embodiment 1 will be mainly described.

[0033] Embodiment 2 4 is a circuit block diagram of a lighting device 200 according to the second embodiment. The lighting device 200 includes a lighting device 250 and a light source 80. In the lighting device 50 according to the first embodiment, the control IC 30 detects the voltage VQ2 generated in the switching element Q2 from the drain voltage of the switching element Q2. In contrast, in the lighting device 250 according to the present embodiment, the control IC 30 detects the voltage VQ2 generated in the switching element Q2 from the voltage generated in the series circuit formed by the light source 80, the switching element Q2, and the current detection resistor R1. In other words, the VOUT terminal is changed to the anode side of the light source 80.

[0034] During steady state operation and when switching element Q1 fails, the LED current is constant and the voltage generated across light source 80 is also constant. Therefore, the voltage VQ2 generated across switching element Q2 can be detected from the voltage on the anode side of light source 80. Therefore, the circuit configuration of this embodiment also enables constant voltage control of buck converter circuit 10 and protection operation in the event of a failure of switching element Q1, based on the voltage at the VOUT terminal.

[0035] The present disclosure is not limited to the above-described embodiments, and various modifications made to the embodiments and other embodiments constructed by combining some of the components of the embodiments are included within the scope of the present disclosure, as long as they do not deviate from the gist of the present disclosure. [Explanation of symbols]

[0036] 10 buck converter circuit, 20 regulator circuit, 30 control IC, 40 control power supply circuit, 42 step-down circuit, 50 lighting device, 80 light source, 100, 200 lighting device, 250 lighting device, AC AC power supply, C1, C2 smoothing capacitor, C3 electrolytic capacitor, D1 diode, DB1 diode bridge, L1 inductor, Q1, Q2 switching element, R1 current detection resistor, R2, R3 resistor

Claims

1. a regulator circuit including a switching element and a current detection resistor connected in series with the switching element; a power supply circuit that applies a voltage across both ends of a series circuit formed by a light source, the switching element, and the current detection resistor to turn on the light source; a control unit that adjusts the impedance of the switching element so that the voltage generated across the current detection resistor matches a target value; Equipped with The control unit When the voltage generated in the current detection resistor exceeds a predetermined first threshold value that is higher than the target value, the operation of the power supply circuit is stopped; A lighting device characterized in that, when a voltage generated in the switching element exceeds a predetermined second threshold, operation of the switching element is stopped.

2. The lighting device according to claim 1 , wherein the control unit controls the power supply circuit so that the voltage generated in the switching element coincides with a target voltage that is lower than the second threshold value.

3. 3. The lighting device according to claim 1, wherein the control unit detects a voltage generated in the switching element from a drain voltage of the switching element.

4. 3. The lighting device according to claim 1, wherein the control unit detects the voltage generated in the switching element from the voltage generated in the series circuit.

5. The lighting device according to any one of claims 1 to 4; the light source; A lighting device comprising:

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