JP2015153473A - Lighting device, and luminaire - Google Patents

Abstract

A lighting device and a lighting fixture capable of charging a bootstrap capacitor with a more simplified circuit are provided.
A buck converter circuit includes a switching element Q1 having a first terminal (for example, drain) connected to a DC power supply VPFC, and a choke coil L1 having one end connected to a second terminal (for example, a source) of the switching element Q1. . One end of the smoothing capacitor C4 is connected to the choke coil L1. The lighting device 1 includes a resistor R5 for discharging the electric charge accumulated in the smoothing capacitor C4. The capacitor C2 is a bootstrap capacitor that is connected to the control circuit 3 and serves as a power source for stably performing high-side driving of the switching element Q1. The lighting device 1 includes a charging power source Vdz5 that charges the capacitor C2 via the diode D21 by turning on (that is, conducting) the switching element Q2.
[Selection] Figure 1

Description

  The present invention relates to a lighting device and a lighting fixture.

  2. Description of the Related Art Conventionally, for example, as disclosed in Japanese Patent Application Laid-Open No. 2011-155748, a lighting device including a converter circuit that drives a switching element on the high side is known. In order to drive the switching element on the high side, it is necessary to secure a power source for a control circuit that inputs a control signal to the switching element. As a typical example of the power supply method, a bootstrap power supply system is known, and this is also used in the conventional technology. Specifically, in the above-described conventional technology, a switching element is also provided on the low side, and the charging path to the bootstrap capacitor is formed by turning off the high side switching element and turning on the low side switching element at the time of startup. .

JP 2011-155748 A

  A lighting device for illumination may be provided with a resistor for discharging the charge of the smoothing capacitor on the output side in order to ensure safety when the light emitting module is attached or detached. The inventor of the present application has found a problem that charging is insufficient because the potential at one end of the bootstrap capacitor is raised due to the current flowing through the resistor.

  The present invention has been made to solve the above-described problems, and an object thereof is to provide a lighting device and a lighting fixture that can suppress insufficient charging of a bootstrap capacitor.

  A lighting device according to the present invention includes a first switching element having a first terminal connected to a DC power source, a buck converter circuit having a choke coil having one end connected to a second terminal of the first switching element, and one end having the choke A smoothing capacitor connected to the other end of the coil, one end connected to the one end of the smoothing capacitor, a resistor for discharging the charge of the smoothing capacitor, a control power supply, and a control terminal of the first switching element A control circuit for supplying a signal, one end connected to the second terminal, a bootstrap capacitor for supplying power to the control circuit, a voltage higher than the control power supply, and connected to the other end of the bootstrap capacitor And a charging power source for charging the bootstrap capacitor.

  A lighting fixture according to the present invention includes: a light emitting module including a light emitting element and a resistor connected in parallel to the light emitting element; and a lighting device that is connected to the light emitting module and lights the light emitting element. The apparatus includes: a first switching element having a first terminal connected to a DC power source; a buck converter circuit having a choke coil having one end connected to the second terminal of the first switching element; and one end connected to the other end of the choke coil. Control connected to the connected smoothing capacitor, one end connected to the one end of the smoothing capacitor, connected to a resistor for discharging the electric charge of the smoothing capacitor, and a control power supply, and to supply a control signal to the control terminal of the first switching element A circuit, a bootstrap capacitor having one end connected to the second terminal and supplying power to the control circuit, and higher than the control power supply Outputs pressure, and a charging power supply for charging said bootstrap capacitor connected to the other end of the bootstrap capacitor.

  According to the present invention, the bootstrap capacitor can be charged by the charging power supply even when the bootstrap capacitor cannot be sufficiently charged by the control power supply due to the discharging resistor connected to the smoothing capacitor. Insufficient charging can be suppressed.

It is a circuit diagram which shows the lighting device and lighting fixture concerning embodiment of this invention. It is the circuit diagram which extracted a part of lighting device concerning an embodiment of the invention partially.

  FIG. 1 is a circuit diagram showing a lighting device 1 according to an embodiment of the present invention and a lighting fixture 10 having the same. The lighting fixture 10 includes a lighting device 1 and a light emitting module 2. The light emitting module 2 includes at least one LED element 2a and a resistor RL connected in parallel with the LED element 2a, and typically has a configuration often employed in a straight tube type LED. The lighting device 1 is connected to the light emitting module 2 via the positive electrode output terminal 5a and the negative electrode output terminal 5b, and lights the LED element 2a. Instead of the LED element 2a in the present embodiment, an organic EL element may be used.

  The lighting device 1 includes a buck converter circuit 4 connected to the capacitor C1. The buck converter circuit 4 is a so-called non-insulated step-down converter. Capacitor C1 is charged by DC power supply VPFC. A DC voltage generated from a commercial AC power supply (not shown) is supplied from a DC power supply VPFC via a rectifier circuit (or a power factor correction circuit) (not shown). The buck converter circuit 4 includes a switching element Q1 having a first terminal (for example, drain) connected to the DC power supply VPFC, and a choke coil L1 having one end connected to a second terminal (for example, source) of the switching element Q1. The switching element Q1 is an n-channel MOSFET and is driven on the high side. The cathode of the diode D2 is connected to the second terminal of the switching element Q1. The anode of the diode D2 is grounded. The smoothing capacitor C4 has one end connected to the choke coil L1 and the other end connected to the resistor R6. That is, a series circuit of the choke coil L1, the smoothing capacitor C4, and the resistor R6 is provided, and this series circuit is connected in parallel to the diode D2. The resistor R6 is for detecting the LED current flowing through the light emitting module 2. The control terminal (for example, gate) and the second terminal of the switching element Q1 are connected via a resistor R2. The lighting device 1 includes a control circuit 3 which is a high voltage integrated circuit. The control circuit 3 is connected to the control power supply Vcc1 and connected to the control terminal of the switching element Q1 via the resistor R1 to supply a control signal. The voltage detected by the resistor R6 for detecting the LED current is input to the control circuit 3, and based on this detected voltage, the control circuit 3 allows the current flowing through the LED element 2a to be a constant current. The switching element Q1 is turned on / off.

  The lighting device 1 includes a resistor R5 for discharging the electric charge accumulated in the smoothing capacitor C4. The resistor R5 is a voltage dividing circuit in which a resistor R51 and a resistor R52 are connected in series, and can be used when determining the connection of the light emitting module described later. For convenience, these resistors R51 and R52 are also referred to as one resistor R5. One end of the resistor R5 is connected to one end (that is, a positive terminal) of the smoothing capacitor C4, and the other end of the resistor R5 is grounded. Since the electric charge of the smoothing capacitor C4 can be discharged by the resistor R5, the safety in attaching and detaching the light emitting module 2 is ensured. The voltage divided by the resistors R51 and R52 is input to the control circuit 3. In addition, when the light emitting module connection determination mentioned later in this invention is abbreviate | omitted, this resistance R5 may consist of one resistive element.

(Bootstrap circuit)
The lighting device 1 includes a capacitor C2. The capacitor C2 is a bootstrap capacitor that is connected to the control circuit 3 and serves as a power source for stably performing high-side driving of the switching element Q1. One end of the capacitor C2 is connected to the control circuit 3, and is also connected to the second terminal of the switching element Q1. The other end of the capacitor C2 is preferably connected to the cathode of a high voltage diode D21. The cathode of the diode D1 is connected to the connection point between the other end of the capacitor C2 and the cathode of the diode D21, and the anode of the diode D1 outputs a control power supply voltage of, for example, about 15V to 20V via the resistor R4. Connected to Vcc1. A capacitor C3 having one end connected to the control power supply Vcc1 and the other end grounded is provided for charging the capacitor C2 or stabilizing the control power supply Vcc1.

  The lighting device 1 includes a charging power source Vdz5 that charges the capacitor C2 via the diode D21 by turning on (that is, conducting) the switching element Q2. The charging power source Vdz5 is generated from the DC power source VPFC by the power source generation circuit, and outputs a voltage (for example, about 38 V) higher than the control power source Vcc1. Typically, this power generation circuit is not shown, but a resistor having one end connected to the DC power source VPFC and outputting a voltage from the other end, and a Zener having the other end connected to the anode and the other end grounded. A circuit composed of a diode may be used. The charging power supply Vdz5 is connected to the second terminal of the switching element Q1 through the resistor R3. By turning on switching element Q2, charging power supply Vdz5 → switching element Q2 → diode D21 → capacitor C2 → second terminal (specifically source) of switching element Q1 → choke coil L1 → resistor R5 → ground potential A “charging path” is formed, which is shown in FIG.

  The lighting device 1 includes a Zener diode Dz26 that is connected in parallel to the control circuit 3 like the capacitor C2. The anode of the Zener diode Dz26 is connected to one end of the capacitor C2, and the cathode of the Zener diode Dz26 is connected to the other end of the capacitor C2. The charging power supply Vdz5 is higher than the control power supply Vcc1, whereas the inter-terminal voltage of the control circuit 3 is often limited. Therefore, the Zener diode Dz26 can protect the application of an excessive voltage between the terminals of the control circuit 3.

(Light emitting module connection determination using Vdz5)
The lighting device 1 includes a resistor R3 inserted in series between the charging power source Vdz5 and the second terminal of the switching element Q1. Specifically, the resistor R3 has one end connected between the positive electrode output terminal 5a and the second terminal (for example, source) of the switching element Q1, and the other end connected to the charging power source Vdz5. Since it is desired to prevent the buck converter circuit 4 from being driven when the light emitting module 2 is not connected to the lighting device 1, the lighting device 1 has a function of detecting whether or not the light emitting module 2 is connected. Specifically, when the light emitting module 2 is connected, both ends of the resistor RL are connected to the positive output terminal 5a and the negative output terminal 5b, so that when the resistor RL is attached in parallel to the resistor R5, the resistor R51, The voltage divided by R52 decreases. On the other hand, when the light emitting module 2 is removed, the voltage divided by the resistors R51 and R52 increases. Therefore, the control circuit 3 determines whether or not the voltage divided by the resistors R51 and R52 is equal to or less than a predetermined value, whereby the load, that is, the light emitting module 2 is connected to the positive output terminal 5a and the negative output terminal 5b. It is detected whether it was done. Furthermore, in the present embodiment, the charging power supply Vdz5 applies a voltage to one end of the resistor R5 via the resistor R3 and the choke coil L1 for the light emitting module connection determination. As a result, the charging power source Vdz5 can be used together as a power source for determining the connection of the light emitting module.

  The present invention is not limited to this, and the charging power source Vdz5 may not be used as a power source for determining the connection of the light emitting module. In that case, for example, a resistor may be connected in parallel between the drain and source of the switching element Q1, and the power source for determining the connection of the light emitting module may be taken out from the DC power source VPFC.

(Switching circuit for charging the bootstrap capacitor and light emitting module connection)
The lighting device 1 includes a switching element Q2 that switches electrical connection between the charging power source Vdz5 and the capacitor C2 between conduction and interruption. In the present embodiment, the switching element Q2 is a p-channel MOSFET, and a resistor R20 that connects the control terminal (for example, gate) and the second terminal (for example, source) of the switching element Q2 is also provided. The first terminal (for example, drain) of the switching element Q2 is connected to the anode of the diode D21. A control terminal of the switching element Q2 is connected to a second terminal (for example, a collector) of the switching element Q3. In the present embodiment, the switching element Q3 is an npn bipolar transistor, the connection point of resistors R31 and R32 is connected to the base, and the emitter is grounded. One end of the series circuit of the resistors R31 and R32 is connected to the trigger power supply Vtrg, and the other end of the series circuit is grounded.

  The trigger power supply Vtrg generates a trigger signal that is high for a certain period before the buck converter circuit 4 is activated. Control for generating the trigger signal is not particularly limited, but the control circuit 3 or another control circuit controls the trigger power supply Vtrg so that the trigger signal is generated when a switch (not shown) of the lighting device 1 is turned on. May be. This trigger signal provides a period in which the switching element Q2 is turned off (that is, shut off) after the lighting device 1 is switched on and before the buck converter circuit 4 is actually activated (that is, the switching operation of the switching element Q1 is started). By doing in this way, the lighting device 1 performs the light emitting module connection determination mentioned above in the state which interrupted | blocked the switching element Q2 before starting of the buck converter circuit 4. FIG. Thereafter, after the elapse of a predetermined period (preferably after completion of the light emitting module connection determination), the trigger signal becomes low and the switching element Q2 is turned on, whereby charging of the capacitor C2 is started. Preferably, if the light emitting module 2 is not connected as a result of the light emitting module connection determination, the buck converter circuit 4 is not activated and the switching element Q2 is kept off so that the capacitor C2 is not charged. Good.

  As described above, in the present embodiment, the bootstrap capacitor (that is, the capacitor C2) and the charging power source Vdz5 can be shut off by turning off the switching element Q2 when determining the connection of the light emitting module. If this interruption is not performed at the time of determining the connection of the light emitting module, a charging path (dashed arrow in FIG. 1) including the capacitor C2 is formed, and the current flowing through the charging path is added to the resistors R5 and RL. In this embodiment, such a summation of currents can be avoided, so that deterioration in accuracy of the light emitting module connection determination can be suppressed.

  FIG. 2 is a circuit diagram in which a part of the lighting device 1 is partially extracted. A capacitor that is a bootstrap capacitor in order for the control circuit 3 to stably supply a control signal (that is, a gate drive signal) to the switching element Q1 that is driven on the high side, as is often used as a bootstrap power supply system. It is necessary to charge C2 to be a power source for the control circuit 3. The capacitor C2 is charged when the buck converter circuit 4 is activated. The lighting device 1 includes a resistor R5 for discharging the smoothing capacitor C4, and the light emitting module 2 includes a resistor RL connected in parallel to the LED element 2a. For the sake of convenience, the parallel circuit of the resistors R5 and RL is shown as a resistor Rx in FIG. The control circuit 3 includes a constant current source Icc corresponding to the consumption current consumed by the control circuit 3. The current Vcc of the constant current source Icc flows into the resistor Rx, thereby raising the potential Vx in FIG. . If it is attempted to charge the capacitor C2 only with the control power supply Vcc1 (current I1 in FIG. 2), the charging of the capacitor C2 is suppressed by the amount that the potential Vx is raised. Since the resistors R5 and RL typically have a size of several hundred kΩ, the resistor Rx must be increased to some extent accordingly. If the resistance Rx is large, even if the current of the constant current source Icc is as small as about several tens of μA, for example, the potential Vx is not negligible when performing the necessary charging of the capacitor C2, which is a bootstrap capacitor. In this regard, in the present embodiment, the charging power supply Vdz5 having a voltage higher than that of the control power supply Vcc1 is separately provided, so that the capacitor C2 can be sufficiently charged by the current I2. The current I3 in FIG. 2 describes the current that flows when the light emitting module connection is determined.

  As described above, according to the lighting device 1, even when the control power supply Vcc1 cannot sufficiently charge the capacitor C2 by the residual charge discharging resistor R5 connected to the smoothing capacitor C4, a high voltage provided separately is provided. The capacitor C2 can be reliably charged by the charging power source Vdz5. Since the capacitor C2 can be charged by the charging power source Vdz5, the bootstrap capacitor (that is, the capacitor C2) can be charged with a more simplified circuit.

  In the above description, the problem of insufficient charging due to the resistor Rx including the resistor RL has been described. However, even if a light emitting module that does not include the resistor RL is connected to the lighting device 1, a problem of insufficient charging due to the resistor R5 may occur. Therefore, the present invention can exert its effect regardless of the presence or absence of the resistor RL. Note that the switching elements Q2 and Q3 are not necessarily indispensable components in the present invention, and are preferable improvements for suppressing deterioration in accuracy of the light emitting module connection determination. Therefore, the switching elements Q2 and Q3 may be omitted.

  In the lighting device 1 according to the present embodiment, charging shortage of the bootstrap capacitor (capacitor C2) is suppressed using the charging power supply Vdz5. On the other hand, for example, there is a technique of providing a low-side switching element such as Japanese Patent Application Laid-Open No. 2011-155748 and turning it on at the start-up for charging the bootstrap capacitor. Compared with such a conventional technique, in the lighting device 1 according to the present embodiment, it is possible to suppress problems such as an increase in the number of switching elements and a complicated control at the start-up due to the bootstrap capacitor charging. it can.

The calculation result regarding the charging of the capacitor C2 in the lighting device 1 described above is shown below.
Vcc1 = R4 × I1 + Rx (I1 + I3) + Vfd1 + Vc2
Vdz5 = R3 × I3 + Rx (I1 + I3)
I1 = Icc
Rx = 1 / (1 / R5 + 1 / RL)
I3 = (Vdz5−Rx × I1) / (R3 + Rx)
Vc2 = Vcc1- (R4 + Rx) * I1-Vfd1-Rx * (Vdz5-Rx * I1) / (R3 + Rx)
Here, Vfd1 is a forward voltage of the diode D1, and Vc2 is a voltage of the capacitor C2. The resistance value of each element in the above equation is such that the value of the voltage Vc2 is higher than the voltage to charge the capacitor C2, which is a bootstrap capacitor (that is, the voltage necessary for driving the control circuit 3). And so on.

DESCRIPTION OF SYMBOLS 1 Lighting device, 2 Light emitting module, 2a LED element, 3 Control circuit, 4 Buck converter circuit, 5a Positive output terminal, 5b Negative output terminal, 10 Lighting fixture, C2 capacitor (bootstrap capacitor), C4 Smoothing capacitor, Vcc1 Control power supply , Vdz5 charging power supply, VPFC DC power supply

Claims (6)

A first switching element having a first terminal connected to a DC power supply; and a buck converter circuit having a choke coil having one end connected to the second terminal of the first switching element;
A smoothing capacitor having one end connected to the other end of the choke coil;
One end connected to the one end of the smoothing capacitor, and a resistor for discharging the charge of the smoothing capacitor;
A control circuit connected to a control power supply and supplying a control signal to a control terminal of the first switching element;
A bootstrap capacitor having one end connected to the second terminal and supplying power to the control circuit;
A power supply for outputting a voltage higher than the control power supply and charging the bootstrap capacitor by connecting to the other end of the bootstrap capacitor;
A lighting device comprising: A positive output terminal connected to the one end of the smoothing capacitor and a negative output terminal connected to the other end of the smoothing capacitor;
A resistor having one end connected between the positive output terminal and the second terminal of the first switching element and the other end connected to the charging power source;
The lighting device according to claim 1.   The lighting device according to claim 2, further comprising: a second switching element that switches electrical connection between the charging power source and the bootstrap capacitor between conduction and interruption.   4. The lighting device according to claim 3, wherein whether or not a load is connected to the positive electrode output terminal and the negative electrode output terminal in a state where the second switching element is cut off before the buck converter circuit is activated. 5.   The lighting device according to claim 1, further comprising a Zener diode connected in parallel with the bootstrap capacitor. A light emitting module comprising a light emitting element and a resistor connected in parallel with the light emitting element;
A lighting device connected to the light emitting module to light the light emitting element;
With
The lighting device is
A first switching element having a first terminal connected to a DC power supply; and a buck converter circuit having a choke coil having one end connected to the second terminal of the first switching element;
A smoothing capacitor having one end connected to the other end of the choke coil;
One end connected to the one end of the smoothing capacitor, and a resistor for discharging the charge of the smoothing capacitor;
A control circuit connected to a control power supply and supplying a control signal to a control terminal of the first switching element;
A bootstrap capacitor having one end connected to the second terminal and supplying power to the control circuit;
A power supply for outputting a voltage higher than the control power supply and charging the bootstrap capacitor by connecting to the other end of the bootstrap capacitor;
A lighting fixture comprising:

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