WO2019117205A1

WO2019117205A1 - Light-emitting diode drive device

Info

Publication number: WO2019117205A1
Application number: PCT/JP2018/045711
Authority: WO
Inventors: 信道高場; 義博萩原; 福井　康人
Original assignee: パーソルＡｖｃテクノロジー株式会社
Priority date: 2017-12-12
Filing date: 2018-12-12
Publication date: 2019-06-20

Abstract

This light-emitting diode drive device drives a light-emitting diode. The light-emitting diode drive device comprises: a rectification circuit that rectifies AC input signals; a smoothing capacitor that smooths rectified signals; a switch element that switches the rectification circuit and the smoothing capacitor between connection and disconnection; a voltage setting circuit that sets a target value for the smoothing capacitor voltage; a threshold value setting circuit that sets the threshold value for the voltage of rectified signals; and a control circuit that controls the switching on and off of the switch element in accordance with an output signal from the threshold value setting circuit. If the voltage of the rectified signal is at least a threshold value, the control circuit switches off the switch element. Output from the smoothing capacitor is supplied to the light-emitting diode.

Description

Light emitting diode drive

The present invention relates to a light emitting diode drive device for driving a light emitting diode.

In recent years, light emitting diodes (LEDs: Light-Emitting Diodes) have been used as various light sources. For example, LEDs are increasingly used for lighting bulbs used in homes, backlights for TVs, outdoor street lights, and LED displays, and are expected to be used for many electric devices in the future.

An LED drive device is used to light an LED (see, for example, Patent Document 1). In the LED drive device, a high frequency drive method such as PWM (Pulse-Width Modulation) drive is often employed. This is because AC (Alternating Current) input voltage varies, and various voltages exist from 100v to 240v depending on the country. In order to obtain a constant brightness even if the voltage changes, switching is performed on the AC input, and once replaced with a square wave of high frequency (about several tens to several hundreds KHz). This enables the LED to be driven at a stable voltage that does not depend on the voltage of the AC input.

LEDs are in demand worldwide. There is a need for a system that stably drives LEDs even if AC voltages vary in size or vary from country to country.

JP 2012-226917 A

However, in the above LED driving device, the AC input is replaced with a high frequency rectangular wave. For this reason, a transmitting circuit and a transformer for switching are required, and there is a problem that the scale of the circuit is increased and the cost is increased. Further, high frequency noise is generated by the switching operation, so that radiation noise to the AC input is generated, and there is a problem that it is necessary to provide a component for preventing radiation in the AC input line.

The present invention provides a light emitting diode drive device capable of stably driving a light emitting diode, which does not require switching operation at a frequency higher than the frequency of the AC input.

A light emitting diode drive apparatus according to an embodiment of the present invention is a light emitting diode drive apparatus for driving a light emitting diode, the rectification circuit rectifying an AC input signal, the smoothing capacitor smoothing the rectified signal, and A switching element for switching between connection and disconnection of a rectifier circuit and the smoothing capacitor; a voltage setting circuit for setting a target value of the voltage of the smoothing capacitor; and a threshold setting circuit for setting a threshold of the voltage of the rectified signal. A control circuit which controls switching between on and off of the switch element in accordance with an output signal of the threshold setting circuit, and when the voltage of the rectified signal is equal to or higher than the threshold, the control circuit controls the switch The element is turned off and the output from the smoothing capacitor is supplied to the light emitting diode.

According to the embodiment of the present invention, when the output signal of the rectifier circuit is equal to or higher than the threshold value, the rectifier circuit and the smoothing capacitor are not connected. That is, while the voltage of the output signal of the rectifier circuit is high, no voltage is supplied from the rectifier circuit to the smoothing capacitor. As a result, the voltage of the smoothing capacitor is suppressed to be higher than a predetermined voltage, and a DC voltage can be generated stably. Even when the AC voltage input to the light emitting diode drive device is high, the light emitting diode can be stably driven.

In one embodiment, the threshold setting circuit outputs a signal according to the voltage of the rectified signal, and the control circuit turns on the switch element according to the magnitude of the output signal of the threshold setting circuit. It may control switching between and off.

In one embodiment, the threshold and the target value of the voltage of the smoothing capacitor may have the same magnitude.

In one embodiment, the switch element may be a field effect transistor, the rectifier circuit may be connected to a drain of the switch element, and the smoothing capacitor may be connected to a source of the switch element.

In one embodiment, the voltage setting circuit may supply a voltage of the same magnitude as a target value of the voltage of the smoothing capacitor to the gate of the switch element.

In one embodiment, when the voltage of the smoothing capacitor is lower than the target value, the drain and the source of the switch element may conduct.

In one embodiment, the control circuit may make the gate voltage of the switch element smaller than the target value when the voltage of the rectified signal is equal to or higher than the threshold.

In one embodiment, the switch element may be an n-channel MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor).

In one embodiment, the voltage setting circuit may include a smoothing capacitor for smoothing the rectified signal, and a Zener diode connected to the smoothing capacitor of the voltage setting circuit.

In one embodiment, the Zener voltage of the Zener diode may be set according to a target value of the voltage of the smoothing capacitor.

In one embodiment, the light emitting diode driver may further include a diode provided between the rectifier circuit and the switch element.

In one embodiment, an anode of the diode may be connected to the rectifier circuit, and a cathode of the diode may be connected to the switch element.

In one embodiment, the threshold setting circuit may be connected to a node between the rectifier circuit and an anode of the diode.

In one embodiment, the voltage setting circuit may be connected to a node between the rectifier circuit and an anode of the diode.

In one embodiment, the light emitting diode drive device is provided between the rectifier circuit and the switch element, and the harmonic wave suppression that reduces harmonic components generated according to the current flowing from the rectifier circuit to the smoothing capacitor. It may further comprise a circuit.

In one embodiment, the harmonic suppression circuit may include a coil that reduces the harmonic component, and a capacitor that holds a charge when the switch element is off.

In one embodiment, the light emitting diode drive device may further include a constant current source device that sets the magnitude of the current flowing through the light emitting diode to a constant value.

In one embodiment, a voltage may be supplied from the voltage setting circuit to the constant current source device.

In one embodiment, the light emitting diode drive device may further include a light control device that changes the magnitude of the current set by the constant current source device.

In one embodiment, the light control device further includes an insulated communication device that receives a control signal from a control device driven by a power supply independent of the AC input signal, and the constant current source according to the control signal. The magnitude of the current set by the device may be changed.

In the light emitting diode drive device according to the embodiment of the present invention, a switch element is provided between the rectifying diode and the smoothing capacitor. The switch element can cut off the voltage set by the constant voltage setting circuit as a threshold. When the voltage charged to the smoothing capacitor becomes the voltage set by the constant voltage setting circuit, the switch element is cut off. Thereby, the maximum charging voltage of the smoothing capacitor is determined, and this voltage becomes the voltage supplied to the light emitting diode. The control circuit cuts off the switch element while the AC input voltage is higher than the maximum charging voltage of the smoothing capacitor. Thereby, the power consumption of the switch element can be suppressed.

In the light emitting diode drive device according to the embodiment of the present invention, the switching operation at a frequency higher than the frequency of the AC input is unnecessary. The light emitting diode drive device according to the embodiment can drive the light emitting diode with a constant voltage regardless of the magnitude of the AC input voltage.

The light emitting diode drive device according to the embodiment of the present invention suppresses the flow of harmonic components generated at the time of inrush current generation to the smoothing capacitor as radiation noise to the AC input side. In the light emitting diode drive device according to the embodiment, a coil is connected in series between the rectifier circuit and the switch element, and a harmonic capacitor is disposed in the subsequent stage. With the switch element cut off, the harmonic capacitors are charged through the coil at the instant when the AC input reaches the maximum voltage. Also, at the moment when the switch element is turned on, the charge of the harmonic capacitor moves to the smoothing capacitor, and the smoothing capacitor is charged. Thereby, harmonics can be suppressed.

The light emitting diode drive device according to the embodiment can generate a constant voltage without flowing out the harmonic generated by the charging current of the smoothing capacitor. The primary charging capacitor may be a capacitor with a small capacity to compensate for the discharge of the smoothing capacitor, and the small capacity capacitor can significantly reduce harmonic components.

In the light emitting diode drive device according to the embodiment of the present invention, the rectifier circuit, the switch element and the smoothing capacitor become a power supply device that generates a high voltage for driving the light emitting diode. In addition, the light emitting diode drive device includes a constant current source device that determines the amount of current of the light emitting diode on the basis of a low voltage separately generated from the AC input. Thus, even when the AC input voltage fluctuates, the light emitting diode can be stably driven.

In the light emitting diode drive device according to the embodiment of the present invention, the switching operation at a frequency higher than the frequency of the AC input is unnecessary. For this reason, the coil for a switching and the components for preventing radiation become unnecessary, and a light emitting diode drive device can be implement | achieved inexpensively.

It is a block diagram of the light emitting diode drive device concerning the embodiment of the present invention. It is a figure showing an example of the circuit of the light emitting diode drive concerning an embodiment of the present invention. (A) to (h) is a figure which shows the voltage waveform in each component of the light emitting diode drive device based on embodiment of this invention. It is a figure which shows the dynamic range of LED drive voltage which concerns on embodiment of this invention. It is a block diagram of the light emitting diode drive device concerning the embodiment of the present invention. It is a figure showing an example of the circuit of the light emitting diode drive concerning an embodiment of the present invention. (A) to (h) is a figure which shows the voltage waveform and electric current waveform in each component of the light emitting diode drive device based on embodiment of this invention. It is a block diagram of the light emitting diode drive device concerning the embodiment of the present invention. It is a figure showing an example of the circuit of the light emitting diode drive concerning an embodiment of the present invention. It is a figure which shows the relationship between the base voltage of the transistor which concerns on embodiment of this invention, and the brightness | luminance of LED.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. The same reference numerals are given to the same components, and in the case of duplication, the description thereof will be omitted. The following embodiments are exemplifications, and the present invention is not limited to the following embodiments. For example, the materials and components shown in the description of the embodiments are illustrative, and the present invention is not limited thereto. In addition, the circuit configuration of each component (for example, a constant voltage setting circuit and the like) is an example, and other circuit configurations having equivalent functions may be used.

FIG. 1 is a view showing a light emitting diode drive device 100 according to an embodiment of the present invention.

The light emitting diode drive device 100 includes a power supply device 110, a light emitting diode (LED) device 120, and a constant current source device 130. The LED device 120 includes a plurality of light emitting diodes A09. The light emitting diode drive device 100 drives a plurality of light emitting diodes A09 to emit light.

The power supply device 110 converts alternating current voltage into direct current voltage. The power supply device 110 receives, for example, an AC wave (AC input) transmitted from a power plant to a house or the like, and supplies a constant voltage to the LED device 120. The power supply device 110 can stably output a constant voltage regardless of the magnitude of the AC input voltage.

The power supply device 110 shown in FIG. 1 includes a rectifier circuit A02, a smoothing capacitor A03, a diode A04, a constant voltage setting circuit A05, a threshold setting circuit A06, a control circuit A07, and a switch element A08.

The rectifier circuit A02 is, for example, a full-wave rectifier circuit having a diode bridge, and rectifies an AC input signal. For example, the AC input device A01 outputs an AC voltage transmitted from a power plant from two cores, and the output is input to the rectifier circuit A02. The rectifier circuit A02 rectifies the input voltage (input signal).

The signal output from the rectifier circuit A02 is rectified in the positive direction around 0 V, and is input to the smoothing capacitor A03 via the diode A04 and the switch element A08. The smoothing capacitor A03 smoothes the signal rectified by the rectifying circuit A02 to generate a constant voltage. The output (constant voltage) of the smoothing capacitor A03 is supplied to the LED device 120, and the plurality of light emitting diodes A09 emit light.

The constant voltage setting circuit A05 sets a target value of the voltage of the smoothing capacitor A03. The target value of the voltage of the smoothing capacitor A03 is, for example, the maximum value of the charging voltage of the smoothing capacitor. The threshold setting circuit A06 sets the threshold of the voltage of the signal rectified by the rectification circuit A02. The switch element A08 switches between connection and disconnection of the rectifier circuit A02 and the smoothing capacitor A03. The control circuit A07 controls switching between on and off of the switch element A08 according to the output signal of the threshold setting circuit A06. The control circuit A07 performs control to turn off the switch element A08 when the voltage of the signal rectified by the rectification circuit A02 is equal to or higher than the threshold. The control circuit A07 performs control to turn on the switch element A08 when the voltage of the signal rectified by the rectification circuit A02 is less than the threshold.

In the power supply device 110, a target constant voltage is set by the constant voltage setting circuit A05. When the voltage charged in the smoothing capacitor A03 exceeds the voltage set by the constant voltage setting circuit A05, the switch element A08 is cut off. As a result, the voltage stored in the smoothing capacitor A03 becomes the voltage set by the constant voltage setting circuit A05.

Here, it is assumed that the operation is shifted in the direction in which the switch element A08 is cut off in accordance with the voltage set by the constant voltage setting circuit A05. At this time, in the process of shifting the input of the switch element A08 to a high voltage, the charge stored in the smoothing capacitor A03 continues to be discharged toward the LED device 120. Therefore, the switch element A08 is not completely cut off, and the current continues to flow through the switch element A08 in the state where the high voltage is applied. In this state, the switch element A 08 consumes power, resulting in an operation of keeping the voltage. Since the amount of heat generation of the switch element A08 becomes large, a large heat dissipation structure is required, which may make it difficult to realize. For this reason, it is conceivable to completely cut off the switch element A08 during a period in which the smoothing capacitor A03 is discharged.

Therefore, in the present embodiment, the threshold value set by the threshold value setting circuit A06 is used, and the switch element A08 is completely cut off by the control circuit A07 while the AC input voltage is high. Thus, the switch element A08 is always in the cutoff state except at the moment of charging the smoothing capacitor A03, and the power supply device 110 with reduced power consumption can be realized.

The threshold setting circuit A06 detects the output voltage of the rectifier circuit A02, and sends information corresponding to the magnitude relation between the output voltage and the threshold to the control circuit A07. A diode A04 is provided between the rectifier circuit A02 and the switch element A08 so that the threshold setting circuit A06 accurately detects the output voltage of the rectifier circuit A02. The anode of the diode A04 is connected to the rectifier circuit A02, and the cathode is connected to the switch element A08. The constant voltage setting circuit A05 and the threshold setting circuit A06 are connected to a node between the rectifier circuit A02 and the anode of the diode A04. The diode A04 enables the threshold setting circuit A06 to accurately detect the output voltage of the rectifier circuit A02 without being affected by the switch element A08.

With this series of operations, the power supply device 110 can stably supply the voltage set by the constant voltage setting circuit A05 to the LED device 120 even if the AC input voltage fluctuates. For example, even if the AC input voltage fluctuates significantly, such as 100 V to 240 V, the voltage can be stably supplied by setting the setting voltage of the constant voltage setting circuit A05 to a voltage lower than the peak voltage of the AC input. .

As the constant voltage setting circuit A05, for example, a Zener diode may be adopted, a circuit having a transistor may be adopted, or an IC including a complex circuit may be adopted. This enables more accurate detection. Similarly, for example, a Zener diode, a transistor, or an IC may be employed as the threshold setting circuit A06. This can increase the accuracy of the set value.

The constant current source device 130 sets the magnitude of the current flowing to the light emitting diode device 120 constant. The constant current source device 130 includes a constant current setting circuit A11 and a constant current source circuit A12. In this example, a voltage is supplied from the constant voltage setting circuit A05 to the constant current setting circuit A11. The constant current setting circuit A11 supplies a reference voltage to the constant current source circuit A12. The constant current source circuit A12 sets the magnitude of the constant current flowing through the light emitting diode device 120 according to the reference voltage.

The constant current source device 130 is used to drive the light emitting diode device 120 using the output of the power supply device 110 as a power supply. Thus, the light emitting diode device 120 can be driven with a constant current based on a stable voltage.

Next, an example of the circuit configuration of the light emitting diode drive device 100 will be described. FIG. 2 is a diagram showing an example of a circuit of the light emitting diode drive device 100 according to the embodiment.

In the example shown in FIG. 2, the switch element A08 is a field effect transistor. The drain of the switch element A08 is connected to the rectifier circuit A02 via a diode A04. The source of the switch element A08 is connected to one end of the smoothing capacitor A03. The other end of the smoothing capacitor A03 is connected to the ground (GND). In this example, the switch element A08 is an n-channel MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor), but another switch element may be used.

In the example shown in FIG. 2, the constant voltage setting circuit A05 includes a diode B10, a resistor B11, a smoothing capacitor B12, and Zener diodes B13 and B19. The resistor B14 is a connection resistor. One end of the smoothing capacitor B12 is connected to a node between the rectifier circuit A02 and the anode of the diode A04 via the diode B10. The other end of the smoothing capacitor B12 is connected to GND. The smoothing capacitor B12 smoothes the signal rectified by the rectification circuit A02. One end of the smoothing capacitor B12 is connected to the cathode of the Zener diode B13 via the resistor B11. The Zener diode B13 and the Zener diode B19 are connected in series, and the anode of the Zener diode B19 is connected to GND. The cathode of the Zener diode B13 is connected to the gate of the switch element A08.

Zener voltages of the Zener diodes B13 and B19 are set in accordance with a target value of the voltage of the smoothing capacitor A03. For example, the Zener voltage obtained from the pair of Zener diodes B13 and B19 connected in series is set to the same magnitude as the target value of the voltage of the smoothing capacitor A03. The constant voltage setting circuit A05 supplies a voltage of the same magnitude as the target value of the voltage of the smoothing capacitor A03 to the gate of the switch element A08.

In the example shown in FIG. 2, the threshold setting circuit A06 is a voltage dividing circuit including the resistors B15 and B16. One end of the voltage dividing circuit is connected to a node between the rectifier circuit A02 and the anode of the diode A04. The other end of the voltage dividing circuit is connected to GND. Further, in the example shown in FIG. 2, the control circuit A07 includes a switch element B18. The resistor B17 is a connection resistor. In this example, the switch element B18 is a field effect transistor. The drain of the switch element B18 is connected to the gate of the switch element A08. The source of the switch element B18 is connected to GND. The gate of the switch element B18 is connected to the node between the resistor B15 and the resistor B16. That is, a voltage corresponding to the voltage division ratio of the threshold setting circuit A06 is supplied to the gate of the switch element B18. The threshold setting circuit A06 outputs a signal according to the voltage and voltage division ratio of the rectified signal, and the output signal is supplied to the gate of the switch element B18. The control circuit A07 controls switching between on and off of the switch element A08 in accordance with the magnitude of the output signal of the threshold value setting circuit A06.

FIG. 3A to FIG. 3H are diagrams showing voltage waveforms in respective components of the light emitting diode drive device 100. FIG.

In this example, the AC input of the AC input device A01 assumes an AC wave transmitted from a power plant. FIG. 3A shows the waveform of the output voltage C01 of the AC input device A01. As indicated by the solid line and the broken line in FIG. 3A, the output voltage C01 is a two-phase alternating current. The output voltage C01 is input to the rectifier circuit A02. FIG. 3B shows the waveform of the output voltage C02 of the rectifier circuit A02. A voltage C02 of a waveform obtained by full-wave rectifying the output voltage C01 is output from the rectifier circuit A02. The solid line in FIG. 3D indicates the waveform of the output voltage C04 of the smoothing capacitor A03.

The output voltage C02 (full-wave rectified wave) is input to a diode A04, a constant voltage setting circuit A05, and a threshold setting circuit A06.

In the constant voltage setting circuit A05, a voltage C05 having a waveform shown by a solid line in FIG. 3E is generated by the diode B10 and the smoothing capacitor B12. A constant voltage C06 having a waveform shown by a solid line in FIG. 3F is generated by the resistor B11 and the Zener diodes B13 and B19. The Zener voltage of the series-connected Zener diodes B13 and B19 is set to the same magnitude as the target value of the voltage of the smoothing capacitor A03. A constant voltage C06 having the same magnitude as the target value of the voltage of the smoothing capacitor A03 is supplied to the gate of the switch element A08. When the voltage of the smoothing capacitor A03 is lower than the target value, the drain and source of the switch element A08 conduct.

The constant voltage setting circuit A05 of the present embodiment is a circuit used to set a voltage. Since the operation can be performed with a small current, it is possible to realize the constant voltage setting circuit A05 with components having low withstand voltage, withstand current, and the like.

The threshold setting circuit A06 can arbitrarily set the threshold for the AC input by changing the voltage dividing ratio of the voltage dividing circuit. For example, the threshold is set to the same magnitude as the target value of the voltage of the smoothing capacitor A03.

For example, when the voltage of the signal rectified by the rectifier circuit A02 is a threshold, the voltage dividing ratio of the voltage dividing circuit is set such that the gate voltage of the switch element B18 becomes the gate threshold voltage. When the voltage of the signal rectified by the rectifier circuit A02 is equal to or higher than the threshold, the switch element B18 is turned on. When the voltage of the signal rectified by the rectifier circuit A02 is less than the threshold value, the switch element B18 is substantially turned off. When the switch element B18 is on, the gate voltage of the switch element A08 becomes smaller than the target value. In the example shown in FIG. 2, when the switch element B18 is on, the gate of the switch element A08 is connected to GND. Thereby, the switch element A08 is cut off.

In the state where the switch element A08 is cut off, the output voltage of the rectifier circuit A02 is output as it is from the diode A04, but no current flows. When the output voltage of the rectifier circuit A02 is higher than the voltage of the charge stored in the smoothing capacitor A03 while the switch element A08 is in the conductive state, the voltage generated by the rectifier circuit A02 is output as it is. When the output voltage of the rectifier circuit A02 is lower than the voltage applied to the smoothing capacitor A03, the diode A04 is cut off and a voltage applied to the smoothing capacitor A03 is output. As a result, the voltage C03 of the diode A04 has a waveform as shown in FIG. 3 (c).

To the gate of the switch element A08, a voltage C07 having a waveform shown by a solid line in FIG. 3G, which is generated from the output C06 of the constant voltage setting circuit A05 and the output of the control circuit A07, is applied. When the output C02 of the rectifier circuit A02 is higher than the output C06 of the constant voltage setting circuit A05, the switch element A08 is cut off and no current flows. When the output C02 of the rectifier circuit A02 is lower than the output C06 of the constant voltage setting circuit A05, the source and the drain of the switch element A08 conduct, and the smoothing capacitor A03 is charged.

When the AC input is large, power consumption of the switch element A 08 can be suppressed by generating no power consumption.

The constant current setting circuit A11 includes a switch element F04 and resistors F01, F02 and F06. In this example, the switch element F04 is an NPN bipolar transistor, but another switch element may be used. The resistors F01 and F02 connected in series constitute a voltage dividing circuit. One end of this voltage dividing circuit is connected to a node between the Zener diode B13 and the Zener diode B19. The other end of this voltage dividing circuit is connected to GND. The collector of the switch element F04 is connected to a node between the Zener diode B13 and the Zener diode B19. The emitter of the switch element F04 is connected to GND via a resistor F06. The base of the switch element F04 is connected to the node between the resistor F01 and the resistor F02. That is, a voltage corresponding to the voltage dividing ratio of the voltage dividing circuit is supplied to the base of the switch element F04.

The constant current source circuit A12 includes a switch element F05 and a resistor F07. In this example, the switch element F05 is an NPN bipolar transistor, but another switch element may be used. The collector of the switch element F05 is connected to the LED device 120. The emitter of the switch element F05 is connected to GND via a resistor F07.

A reference voltage is generated with a voltage division ratio of the resistors F01 and F02 using a voltage set by voltage division of the Zener diodes B13 and B19 as a power supply. This reference voltage is the base voltage of the switch element F04. The emitter output of the switch element F04 is a reference voltage supplied to the base of the switch element F05. The solid line in FIG. 3H indicates the waveform of the reference voltage C08 supplied to the base of the switch element F05. Since the emitter voltage to the base of the switch element F05 is fixed, the collector current (Ic) of the switch element F05 is uniquely determined, and the current flowing to the LED device 120 is determined.

FIG. 4 shows the dynamic range of the voltage for driving the LED device 120. FIG. 4 shows the waveform of the output voltage C02 of the rectifier circuit A02, the waveform of the output voltage C04 of the smoothing capacitor A03, and the waveform of the emitter voltage C09 of the switch element F05.

The output voltage C04 of the smoothing capacitor A03 is the upper limit voltage of the dynamic range. The emitter voltage C09 of the switch element F05 is the lower limit voltage of the dynamic range. The LED device 120 can connect the light emitting diodes until the number of forward voltages Vf falls between the two voltages.

According to the present embodiment, when the output signal of the rectifier circuit A02 is equal to or higher than the threshold value, the rectifier circuit A02 and the smoothing capacitor A03 are not connected. That is, while the voltage of the output signal of the rectifier circuit A02 is high, no voltage is supplied from the rectifier circuit A02 to the smoothing capacitor A03. As a result, the voltage of the smoothing capacitor A03 is suppressed from becoming higher than a predetermined voltage, and a DC voltage can be generated stably. Even when the AC voltage input to the light emitting diode drive device 100 is high, the light emitting diode A09 can be stably driven.

Next, measures against harmonics in the light emitting diode drive device 100 will be described. FIG. 5 is a diagram showing a light emitting diode drive device 100 including the harmonic suppression circuit A10.

By adding the harmonic suppression circuit A10 to the light emitting diode drive device 100 described above, it is possible to reduce the harmonics regulated in various countries in the world. The harmonic suppression circuit A10 is provided between the rectifier circuit A02 and the switch element A08. The harmonic suppression circuit A10 reduces harmonic components generated in accordance with the current flowing from the rectifier circuit A02 to the smoothing capacitor A03. The harmonic suppression circuit A10 includes, for example, a coil and a capacitor, and reduces a harmonic by configuring a filter for inrush current. The configuration other than the harmonic suppression circuit A10 of the light emitting diode drive device 100 shown in FIG. 5 is the same as that of the light emitting diode drive device 100 shown in FIG.

In a general power supply, an inrush current occurs at the top of the AC input. However, in the light emitting diode drive device 100 according to the embodiment, the current flows into the smoothing capacitor A03 via the switch element A08. In the light emitting diode drive device 100 according to the embodiment, a current flows at the moment when the switch element A 08 is turned on, and harmonic measures for obtaining a high effect are performed using this feature. Needless to say, the harmonic suppression circuit A10 can be configured by a single coil or a single capacitor depending on the circuit configuration.

FIG. 6 is a view showing an example of a circuit of the light emitting diode drive device 100 according to the embodiment. The harmonic suppression circuit A10 includes a coil D01 that reduces harmonic components, and a capacitor D02 that holds a charge when the switch element A08 is off. One end of the coil D01 is connected to the rectifier circuit A02 via a diode A04. The other end of the coil D01 is connected to one end of the capacitor D02 and the drain of the switch element A08. The other end of the capacitor D02 is connected to GND.

FIGS. 7A to 7H are diagrams showing voltage waveforms and current waveforms in each component of the light emitting diode drive device 100. FIG.

In the circuit configuration shown in FIG. 2, the output voltage E02 of the diode A04 has a waveform shown in FIG. 7 (b) with respect to the output voltage E01 of the rectifier circuit A02 shown in FIG. 7 (a). The smoothing capacitor A03 is charged at the timing when the current waveform E03 of the smoothing capacitor A03 shown by the solid line in FIG. 7C becomes a pulse shape. The current waveform E03 generated at the time of charging the smoothing capacitor A03 is a basic waveform of harmonics.

In a general power supply device, a smoothing capacitor is connected immediately after the rectification circuit. Therefore, the charging current is generated at the top of the waveform of the output voltage E01. In the present embodiment, measures against harmonics are taken by utilizing the fact that the timing at which the smoothing capacitor is charged is shifted.

In the light emitting diode drive device 100 of the present embodiment, the output voltage E01 of the rectifier circuit A02 reaches its maximum value (peak) in a state where the switch element A08 is cut off. When the coil D01 and the capacitor D02 are disposed in the light emitting diode drive device 100, the capacitor D02 is charged at the timing when the output voltage E01 reaches the maximum value. Because of the filtering effect of the coil D01 and the capacitor D02, the charging waveform E05 of the capacitor D02 is a waveform with a low frequency as shown by the solid line in FIG. 7 (e). Since the charging operation of the capacitor D02 is performed in a state where the switch element A08 is cut off, no harmonic component flows out to the AC input side.

In the light emitting diode drive device 100 provided with the harmonic suppression circuit A10, the output voltage E04 of the diode A04 has a waveform shown by a solid line in FIG. 7 (d). As shown in FIG. 7D, the top of the output of the rectifier circuit A02 is smoothed (voltage is kept) by the capacitor D02. Then, the smoothing capacitor A03 is charged at the moment when the switch element A08 conducts.

The deviation of this timing is shown in FIG. 7 (h). The solid line in FIG. 7F indicates the discharge current waveform E06 of the capacitor D02. The solid line in FIG. 7G indicates the charging current waveform E07 of the smoothing capacitor A03.

The solid line in FIG. 7 (h) indicates a waveform E08 obtained by combining the waveforms in FIG. 7 (e) to FIG. 7 (g). The low rise portion of the waveform is the waveform E05 charged to the capacitor D02. The waveform which is sharp at the top and bottom becomes a waveform in which the charge moves from the capacitor D02 to the smoothing capacitor A03. The waveform rising sharply in the upward direction is the charging current waveform E07 to the smoothing capacitor A03. The waveform that falls sharply downward is the discharge current waveform E06 of the capacitor D02. At the moment when current flows from the capacitor D02 to the smoothing capacitor A03, the diode A04 is in a cut-off state. Since harmonics can not be seen from the AC input direction on the front stage of the rectifier circuit A02, it is possible to implement harmonic countermeasures.

Next, an embodiment for adjusting the brightness of the light emitting diode will be described. In the light emitting diode drive device 100, the brightness can be adjusted by changing the reference voltage of the constant current source circuit A12.

FIG. 8 is a view showing the light emitting diode drive device 100 to which the light control device 140 is connected. The dimmer 140 changes the magnitude of the current set by the constant current source circuit A12. The light emitting diode drive device 100 may include the light control device 140. The configuration other than the light control device 140 of the light emitting diode drive device 100 shown in FIG. 8 is the same as that of the light emitting diode drive device 100 shown in FIG.

The light control device 140 includes an LED current control device F08, an isolated communication device F13, and a current control circuit F14.

The LED current controller F08 is driven by a power supply independent of the AC input signal from the AC input device A01. The control signal output from the LED current control device F08 is transmitted from the data transmission circuit E15 of the isolated communication device F13 to the data reception circuit E16. The control signal transmitted to the data reception circuit E16 is transmitted to the current control circuit F14. The current control circuit F14 changes the magnitude of the current set by the constant current source device 130 according to the control signal.

The light emitting diode drive device 100 may be configured to be directly connected to an AC input transmitted from a power plant. An insulation band F19 is provided on the assumption that insulation is necessary for control from the outside. The control data generated by the LED current control device F18 present outside is transferred from the data transmission circuit E15 to the data reception circuit E16 via the insulating part by the isolated communication device F13, and data is set in the current control circuit F14. As a result, the reference voltage of the constant current source circuit A12 is controlled, and the amount of current of the LED device 120 is arbitrarily changed to change the luminance of the LED device 120.

FIG. 9 is a diagram showing an example of a circuit of the light emitting diode drive device 100 according to the embodiment. In the example shown in FIG. 9, the insulated communication device F13 includes resistors F09, F10, and F12, a switch element F11, and a photocoupler F17. In this example, the switch element F11 is an NPN-type bipolar transistor, but another switch element may be used.

The resistor F09 and the resistor F10 connected in series constitute a voltage dividing circuit. One end of the voltage dividing circuit is connected to the LED current controller F08, and the other end is connected to GND. The base of the switch element F11 is connected to the node between the resistor F09 and the resistor F10.
One end of the resistor F12 is connected to the LED current control device F08, and the other end is connected to the photocoupler F17. The collector of the switch element F11 is connected to the photocoupler F17, and the emitter is connected to GND.

In the example shown in FIG. 9, the current control circuit F14 is a resistor. One end of the resistor F14 is connected to the photocoupler F17. One end of the resistor F14 is connected to GND via a photocoupler F17. The other end of the resistor F14 is connected to a node between the resistor F01 and the resistor F02. That is, the other end of the resistor F14 is connected to the base of the switch element F04.

The LED current control device F08 includes a microcomputer and the like. The control signal output from the LED current control device F08 controls the current flowing through the switch element F11. The control signal is transmitted to the resistor F14 via the photocoupler F17 across the insulating portion F19. The control signal is transmitted to the base of switch element F04 that constitutes the emitter follower. When the base voltage of the switch element F04 changes, the base voltage of the switch element F05 changes. Thereby, the magnitude of the current flowing to the LED device 120 is changed.

FIG. 10 is a diagram showing the relationship between the base voltage of the switch element F05 and the luminance of the LED. The vertical axis indicates the brightness of the LED, and the horizontal axis indicates the base voltage of the switch element F05. As the current flowing through the resistor F14 connected to the LED current control device F08 is gradually increased, the base voltage of the switch element F05 gradually decreases, and the current flowing through the LED device 120 decreases. As a result, the luminance of the light emitted from the LED device 120 is reduced.

In the above-mentioned example, although LED drive control is performed from the exterior of an insulation part via photocoupler F17, the present invention is not limited to this. For example, similar LED drive control can be realized by performing control using another insulating portion, such as using a transformer.

As described above, the light emitting diode drive device 100 according to the embodiment is a device for driving the light emitting diode A09. The light emitting diode drive device 100 includes a rectifier circuit A02 that rectifies an AC input signal, a smoothing capacitor A03 that smoothes the rectified signal, and a switch element A08 that switches connection and disconnection between the rectifier circuit A02 and the smoothing capacitor A03. A constant voltage setting circuit A05 for setting a target value of the voltage of the smoothing capacitor A03; a threshold setting circuit A06 for setting a threshold of the voltage of the rectified signal; and a switch element A08 according to an output signal of the threshold setting circuit A06. And a control circuit A07 that controls switching between on and off. When the voltage of the rectified signal is equal to or higher than the threshold, the control circuit A07 turns off the switch element A08. The output from the smoothing capacitor A03 is supplied to the light emitting diode A09.

According to the embodiment of the present invention, when the output signal of the rectifier circuit A02 is equal to or higher than the threshold, the rectifier circuit A02 and the smoothing capacitor A03 are not connected. That is, while the voltage of the output signal of the rectifier circuit A02 is high, no voltage is supplied from the rectifier circuit A02 to the smoothing capacitor A03. As a result, the voltage of the smoothing capacitor A03 is suppressed from becoming higher than a predetermined voltage, and a DC voltage can be generated stably. Even when the AC voltage input to the light emitting diode drive device 100 is high, the light emitting diode A09 can be stably driven.

In one embodiment, the threshold setting circuit A06 outputs a signal according to the voltage of the rectified signal, and the control circuit A07 turns on the switch element A08 according to the magnitude of the output signal of the threshold setting circuit A06. You may control the switching off.

In one embodiment, the threshold and the target value of the voltage of the smoothing capacitor A03 may have the same magnitude.

In one embodiment, the switch element A08 may be a field effect transistor, the rectifier circuit A02 may be connected to the drain of the switch element A08, and the smoothing capacitor A03 may be connected to the source of the switch element A08.

In one embodiment, the constant voltage setting circuit A05 may supply a voltage of the same magnitude as the target value of the voltage of the smoothing capacitor A03 to the gate of the switch element A08.

In one embodiment, when the voltage of the smoothing capacitor A03 is lower than the target value, the drain and source of the switch element A08 may conduct.

In one embodiment, the control circuit A07 may make the gate voltage of the switch element A08 smaller than a target value when the voltage of the rectified signal is equal to or higher than a threshold.

In one embodiment, the switch element A08 may be an n-channel MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor).

In one embodiment, the constant voltage setting circuit A05 may include a smoothing capacitor B12 for smoothing a rectified signal, and Zener diodes B13 and B19 connected to the smoothing capacitor B12 of the constant voltage setting circuit A05.

In one embodiment, the Zener voltages of the Zener diodes B13 and B19 may be set according to the target value of the voltage of the smoothing capacitor A03.

In one embodiment, the light emitting diode drive device 100 may further include a diode A04 provided between the rectifier circuit A02 and the switch element A08.

In an embodiment, the anode of the diode A04 may be connected to the rectifier circuit A02, and the cathode of the diode A04 may be connected to the switch element A08.

In one embodiment, the threshold setting circuit A06 may be connected to a node between the rectifier circuit A02 and the anode of the diode A04.

In one embodiment, the constant voltage setting circuit A05 may be connected to a node between the rectifier circuit A02 and the anode of the diode A04.

In one embodiment, the light emitting diode drive device 100 is provided between the rectifier circuit A02 and the switch element A08 to reduce harmonics that reduces harmonic components generated in accordance with the current flowing from the rectifier circuit A02 to the smoothing capacitor A03. It may further include a circuit A10.

In one embodiment, the harmonic suppression circuit A10 may include a coil D01 that reduces harmonic components, and a capacitor D02 that holds a charge when the switch element A08 is off.

In one embodiment, the light emitting diode drive device 100 may further include a constant current source device 130 that sets the magnitude of the current flowing through the light emitting diode A09 constant.

In one embodiment, a voltage may be supplied to the constant current source device 130 from the constant voltage setting circuit A05.

In one embodiment, the light emitting diode drive device 100 may further include a light control device 140 that changes the magnitude of the current set by the constant current source device 130.

In one embodiment, the light control device 140 further includes an insulated communication device F13 that receives a control signal from the LED current control device F08 driven by a power supply independent of an alternating current input signal, and the constant current according to the control signal The magnitude of the current set by the source device 130 may be changed.

In the light emitting diode drive device 100 according to the embodiment of the present invention, the switch element A08 is disposed between the rectifier circuit A02 and the smoothing capacitor A03. The smoothing capacitor A03 is charged with a voltage lower than that of the AC input, and a predetermined voltage is output. The switch element A08 is turned on when the voltage of the smoothing capacitor A03 becomes lower than the control terminal voltage (gate voltage). In addition, when the AC input is equal to or higher than the threshold, the switch element A08 is forcibly turned off, whereby the power consumption of the switch element A08 can be suppressed.

The light emitting diode drive device 100 according to the embodiment of the present invention can stably generate a constant voltage under conditions that the AC input is unstable or change, for example, the output of the power plant is unstable. It can be output. Further, for example, by adopting the light emitting diode drive device 100 provided with the harmonic suppression circuit A10 according to the embodiment of the present invention, it is not necessary to take measures against harmonics in the other parts, and the electric product can be manufactured inexpensively. it can.

The present invention is particularly useful in the field of light emitting diode driving devices for driving light emitting diodes.

100: light emitting diode drive device 110: power supply device 120: light emitting diode device 130: constant current source device 140: light control device A01: AC input device A02: rectification circuit A03: smoothing capacitor A04: diode A05: constant voltage setting circuit A06: Threshold setting circuit A07: Control circuit A08: Switch element A09: Light emitting diode A10: Harmonic suppression circuit A11: Constant current setting circuit A12: Constant current source circuit B10: Diode B11: Resistor B12: Smoothing capacitor B13: Zener diode B14: Connection resistance B15: Resistor B16: Resistor B17: Connection resistance B19: Switch element B19: Zener diode D01: Coil D02: Capacitor F01: Resistor F02: Resistor F04: Transistor F05: Transistor F06: Resistor Device F07: Resistor F08: LED current control device F09: Resistor F10: Resistor F11: Transistor F12: Resistor F13: Insulated communication device F14: Current control circuit F15: Data transmission circuit F16: Data reception circuit F17: Photo coupler F19: Insulated part

Claims

A light emitting diode drive device for driving a light emitting diode, comprising:
A rectifier circuit that rectifies an AC input signal;
A smoothing capacitor for smoothing the rectified signal;
A switch element that switches connection and disconnection between the rectifier circuit and the smoothing capacitor;
A voltage setting circuit for setting a target value of the voltage of the smoothing capacitor;
A threshold setting circuit for setting a threshold of a voltage of the rectified signal;
A control circuit that controls switching between on and off of the switch element according to an output signal of the threshold setting circuit;
Equipped with
If the voltage of the rectified signal is greater than or equal to the threshold, the control circuit turns off the switch element;
A light emitting diode drive device for supplying an output from the smoothing capacitor to the light emitting diode.
The threshold setting circuit outputs a signal according to the voltage of the rectified signal,
The light emitting diode drive device according to claim 1, wherein the control circuit controls switching between on and off of the switch element in accordance with a magnitude of an output signal of the threshold value setting circuit.
The light emitting diode drive device according to claim 1 or 2, wherein the threshold and the target value of the voltage of the smoothing capacitor have the same magnitude.
The switch element is a field effect transistor,
The rectification circuit is connected to the drain of the switch element,
The light emitting diode drive device according to any one of claims 1 to 3, wherein the smoothing capacitor is connected to a source of the switch element.
The light emitting diode drive device according to claim 4, wherein the voltage setting circuit supplies a voltage having the same magnitude as a target value of the voltage of the smoothing capacitor to a gate of the switch element.
The light emitting diode drive device according to claim 5, wherein when the voltage of the smoothing capacitor is lower than the target value, the drain and the source of the switch element become conductive.
The light emitting diode drive device according to claim 5 or 6, wherein the control circuit makes the gate voltage of the switch element smaller than the target value when the voltage of the rectified signal is equal to or higher than the threshold.
The light emitting diode drive device according to any one of claims 1 to 7, wherein the switch element is an n-channel MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor).
The voltage setting circuit is
A smoothing capacitor for smoothing the rectified signal;
A Zener diode connected to the smoothing capacitor of the voltage setting circuit;
The light emitting diode drive device according to any one of claims 1 to 8, comprising:
The light emitting diode drive device according to claim 9, wherein a Zener voltage of the Zener diode is set according to a target value of a voltage of the smoothing capacitor.
The light emitting diode drive device according to any one of claims 1 to 10 further provided with a diode provided between said rectifier circuit and said switch element.
The light emitting diode drive device according to claim 11, wherein an anode of the diode is connected to the rectification circuit, and a cathode of the diode is connected to the switch element.
The light emitting diode drive device according to claim 12, wherein the threshold setting circuit is connected to a node between the rectifier circuit and an anode of the diode.
The light emitting diode drive device according to claim 12, wherein the voltage setting circuit is connected to a node between the rectifier circuit and an anode of the diode.
The harmonic suppression circuit which is provided between the said rectifier circuit and the said switch element, and reduces the harmonic component generate | occur | produced according to the electric current which flows into the said smoothing capacitor from the said rectifier circuit is further equipped with any one of Claim 1 to 14 A light emitting diode drive device according to any one of the above.
The harmonic suppression circuit is
A coil for reducing the harmonic component;
A capacitor for retaining charge when the switch element is off;
The light emitting diode drive device according to claim 15, comprising:
The light emitting diode drive device according to any one of claims 1 to 16, further comprising a constant current source device which sets a magnitude of a current flowing through the light emitting diode to a constant value.
The light emitting diode drive device according to claim 17, wherein a voltage is supplied from the voltage setting circuit to the constant current source device.
The light emitting diode drive device according to claim 17 or 18, further comprising a dimmer for changing the magnitude of the current set by the constant current source device.
The light control device
It further comprises an isolated communication device that receives a control signal from a control device driven by a power supply independent of the AC input signal,
20. The light emitting diode drive device according to claim 19, wherein the magnitude of the current set by the constant current source device is changed according to the control signal.