JP2011165920A - Led lighting device and illuminating device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a constant current control type LED lighting device capable of switching using a normally on switch and without providing any feedback winding to an inductor. <P>SOLUTION: The LED lighting device includes: a chopper CH including a normally on switch Q1, an inductor L1, a free-wheel diode D1, and a current-detecting impedance element Z1, wherein the current-detecting impedance element is inserted in a position where an increasing current and a decreasing current flow; a load circuit of the light-emitting diode LED; and a control circuit including a switch for controlling the Q1 in the off-state by applying a negative voltage to a gate of the Q1 in the on-state of a control switch CS, and for controlling the Q1 in the on-state by releasing the application of the negative voltage in the state off thereof, wherein a matching means MC turns the control switch on when the terminal voltage of the impedance element reaches a first predetermined value when the increasing current flows, and turns the control switch off when it reaches a second predetermined value when the decreasing current flows. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an LED lighting device and a lighting device including the same.

A wide gap semiconductor is a semiconductor having a large band gap. Wide band gap semiconductor elements such as SiC (silicon carbide), GaN (gallium nitride), and diamond are attracting attention as semiconductors having potentials that greatly exceed the performance limits of Si power devices. Expectations for wide gap semiconductors are also high in this field. These wide band gap semiconductor elements generally have normally-on characteristics in which current flows when the gate voltage is zero (see, for example, Patent Document 1). Further, as representative semiconductor elements using wide band gap semiconductors, JFET (junction FET), SIT (electrostatic induction transistor), MESFET (metal-semiconductor-field-effect-transistor), HFET ( Heterojunction Field Effect Transistor), HEMT (High Electron
Mobility Transistor) and storage FET. In order to reliably turn off a semiconductor element having normally-on characteristics (hereinafter referred to as a normally-on switch), a negative gate voltage control circuit is required.

  On the other hand, it is known that an LED lighting device with high circuit efficiency can be obtained by lighting a light emitting diode using a DC-DC converter (see, for example, Patent Document 2). The DC-DC converter described in Patent Document 2 includes a secondary winding (second inductor) magnetically coupled thereto by energization of an inductor (first inductor) that includes a step-down chopper and passes through an on-state switch element. The voltage induced in the feedback is fed back to keep the switch element on, and when the current flowing through the first inductor becomes zero when the switch element is off, the switch is driven by the back electromotive force generated in the secondary winding. The circuit operates by self-excited constant current control that performs DC-DC conversion by repeating the circuit operation for turning on the element.

JP 2007-006658 A Japanese Patent No. 4123886

  However, the LED lighting device of the prior art has a secondary winding magnetically coupled to the inductor for constant current control of the light emitting diode, and uses the voltage induced in the secondary winding to switch the switching element. Since the ON signal is obtained, the structure of the inductor is complicated, and there is a problem that miniaturization and IC fabrication are hindered.

  It is an object of the present invention to provide a constant current control type LED lighting device that performs switching using a normally-on switch and that does not require a feedback winding in an inductor.

  In order to solve the above-described problems, an LED lighting device according to the present invention includes a DC power source; a normally-on switch, an inductor, a freewheel diode, and a current detection impedance element. Increase and decrease currents flow to the chopper, DC power supply voltage is DC-DC converted and output to the output terminal, and the current detection impedance element is inserted at the position on the circuit where the increase and decrease currents flow A load circuit having a parallel circuit of a light emitting diode and an output capacitor connected to the output end of the chopper; a control switch and a matching means, and the control switch is negative at the gate of the normally-on switch at least when turned on. Apply voltage to control the normally-on switch in the off state And a switch that releases the negative voltage applied to the gate of the normally-on switch when it is off to control the normally-on switch to the on state, and the matching means is interposed between the impedance element and the control switch so that an increased current flows. The control switch is turned on when the terminal voltage of the impedance element reaches the first predetermined value while the control element is turned off when the terminal voltage reaches the second predetermined value when the reduced current is flowing. And a control circuit.

  In the present invention, the chopper includes various choppers such as a step-down chopper, a step-up chopper, and a step-up / step-down chopper. The step-up / step-down chopper is obtained by sequentially connecting a step-up chopper and a step-down chopper. In each of the above choppers, when the normally-on switch is turned on, the increased current flowing from the DC power source flows into the inductor, and when it is turned off, the electromagnetic energy accumulated in the inductor is released and the decreased current flows, and the chopper operation is performed. It is common to do.

  The control circuit includes a control switch and matching means.

  The control switch includes at least a switch that switches the normally-on switch from the on state to the off state. Note that it is allowed to include a second switch for switching the normally-on switch from the off state to the on state if desired. In this case, the switch that switches the normally-on switch from the on state to the off state is the first switch.

  The matching means is interposed between the impedance means and the control switch, and when the increased current flows through the impedance means, the matching switch operates the control switch when the terminal voltage of the impedance means reaches the first predetermined value and is normally on. Turn off the switch. In the case where the reduced current flows, the normally on switch is turned on by controlling the control switch when the terminal voltage of the impedance means reaches the second predetermined value. Note that the second predetermined value is lower than the first predetermined value.

  In the present invention, the matching means only needs to have the above-described function, and the remaining configuration is not particularly limited. However, the matching means can preferably be constituted by a hysteresis comparator. The matching means includes a first detection means for directly detecting the terminal voltage of the impedance means and a second detection means for detecting via the voltage divider, and interlocks when the control switch turns off the normally-on switch. The second detection unit may be switched to the first detection unit.

  Thus, when the normally-on switch is on, an increased current flows from the DC power source to the inductor. When the terminal voltage of the impedance means reaches the first predetermined value, the control switch is turned on via the matching means. Since a negative voltage is applied to the gate of the normally-on switch, the normally-on switch is turned off and the increased current is cut off. Along with this, the electromagnetic energy stored in the inductor is released and a reduced current flows from the inductor, and the control switch is turned off via the matching means to cancel application of the negative voltage to the gate of the normally-on switch. The mullion switch turns on. Thereafter, the above-described circuit operation is repeated to perform the chopper operation.

  Since the load circuit is connected at a position on the circuit where both an increase current and a decrease current accompanying the chopper operation flow, DC-DC voltage conversion is performed, and the light emitting diode of the load connected to the output terminal converts the converted voltage. Lights under constant current control. Note that the output capacitor connected in parallel with the light emitting diode of the load circuit acts to bypass the high frequency component contained in the output of the chopper from the light emitting diode. As a result, the light emitting diode is turned on by the smoothed direct current.

  The supply of control power to the control circuit is not particularly limited in the present invention, but is preferably as follows. That is, a control power supply is obtained from the high voltage side of the load circuit or normally-on switch. In the aspect of obtaining the control power supply from the load circuit, since a DC voltage smoothed by the output capacitor is generated in the load circuit, a voltage higher than the gate threshold voltage of the normally-on switch is obtained from the load circuit to obtain the control power supply. The circuit configuration of the control power supply can be simplified. Further, in the aspect in which the control power supply is obtained from the high voltage side of the normally-on switch, for example, a voltage higher than the gate threshold voltage of the normally-on switch can be obtained from the drain side of the normally-on switch via the dropper.

  The illuminating device of this invention is equipped with the illuminating device main body; The LED lighting device of Claim 1 or 2 arrange | positioned at the illuminating device main body, It is characterized by the above-mentioned.

  In the present invention, the illumination device is meant to include all devices using light emitting diodes as light sources. Therefore, it is allowed to be a lighting fixture, a display device, a sign device, and the like. The illuminating device main body means a remaining portion obtained by removing the LED lighting device from the illuminating device.

  According to the present invention, a normally-on switch is used as a main switching element of a chopper, and a normally-on switch is controlled to be in an off state by applying a negative voltage to the gate of the normally-on switch at least when the switch is on. Including a switch that controls the normally-on switch to be turned on by canceling the application of the negative voltage to the gate of the terminal, and when the increased current flows between the impedance element and the control switch, the terminal voltage of the impedance element is A control circuit that turns on the control switch when the first predetermined value is reached, and turns off the control switch when the second predetermined value lower than the first predetermined value is reached when the reduced current is flowing; By having it, it is easy to turn without using a secondary winding in the inductor. Configuration and will, moreover possible to provide a lighting device which an IC is provided with easy chopper and which together with good properties.

It is a circuit diagram in the 1st form for carrying out the LED lighting device of the present invention. It is a circuit diagram in the 2nd form for carrying out the LED lighting device of the present invention. Similarly, it is the electric current and voltage waveform figure of each part. It is a circuit diagram in the 3rd form for carrying out the LED lighting device of the present invention.

  Hereinafter, embodiments of the present invention will be described in detail.

  With reference to FIG. 1, the 1st form in the LED lighting device of this invention is demonstrated.

  In this embodiment, the LED lighting device includes a DC power source DC, a chopper CH, a load circuit LC, and a control circuit CC.

  The DC power source DC may have any configuration, but may be configured with, for example, a rectifier circuit DB as a main component, and may include a smoothing circuit including a smoothing capacitor C1 if desired. In this embodiment, the rectifier circuit DB is preferably a bridge-type rectifier circuit, and full-wave rectifies the AC voltage of an AC power supply AC, for example, a commercial AC power supply, to obtain a DC voltage.

  In this embodiment, the chopper CH is constituted by a non-insulated step-down chopper. The power part of the chopper CH, that is, the circuit part through which the power supplied to the load passes is configured to include a normally-on switch Q1, an inductor L1, a free wheel diode D1, and a current detecting impedance element Z1. The power section can be divided into a first circuit A and a second circuit B in terms of circuit operation.

  The first circuit A is a circuit that accumulates electromagnetic energy from the DC power supply DC to the inductor L1, and has a configuration in which a series circuit including a normally-on switch Q1, a load circuit LC, and an inductor L1 is connected to the DC power supply DC. . When the normally-on switch Q1 is turned on, an increased current flows from the DC power source DC, and electromagnetic energy is accumulated in the inductor L1.

  The second circuit B is a circuit that discharges electromagnetic energy stored in the inductor L1, and includes a configuration in which a series circuit including a freewheel diode D1 and a load circuit LC is connected to the inductor L1, and a normally-on switch Q1. Decreases current flows from the inductor L1.

  The normally-on switch Q1 is allowed to use various wide gap semiconductors described in the background art section in the present invention, but in this embodiment, a HEMT using a GaN substrate is used. Therefore, the normally-on switch Q1 is a field effect type wide gap semiconductor having a drain, a source, and a gate. The normally-on switch Q1 has a remarkably superior potential compared to a widely used Si semiconductor, and can operate a chopper at an operating frequency of, for example, a GHz class. For this reason, the miniaturization of the inductor L1 can be realized. As a result, the entire LED lighting device can be significantly reduced in size.

  Inductor L1 only needs to have a function of accumulating electromagnetic energy supplied from DC power source DC and then releasing it in the present invention. There is no need. For this reason, it is possible to simplify the structure of the inductor L1 and contribute to its miniaturization.

  The freewheel diode D1 is a means for providing a current path, ie, a second circuit B, for discharging and regenerating electromagnetic energy accumulated in the inductor L1, and for example, a Schottky barrier according to the operating frequency of the chopper CH. A switching diode such as a diode or a PIN diode can be used.

  The current detecting impedance element Z1 is inserted into a position on the circuit through which both an increasing current and a decreasing current flow, that is, a line portion shared by the first circuit A and the second circuit B, and detects each of the currents. It is. For example, a resistor having a small resistance value is used.

  In the case of the step-up chopper, the chopper CH includes a first circuit A in which a series circuit of the inductor L1 and the normally-on switch Q1 is connected to the DC power source DC, and a series circuit of the inductor L1, the freewheel diode D1, and the load circuit LC. A second circuit B connected to the DC power source DC can be used. The step-up / down chopper is as described above.

  The load circuit LC is constituted by a parallel circuit of a light emitting diode LED and an output capacitor C2, and is connected to a position on the circuit through which both an increase current and a decrease current flow. Note that the light emitting diode LED is composed of a single forward or a plurality of series connected in series with respect to the current.

  The control circuit CC includes a control switch CS and matching means MC, and operates by receiving an appropriate control power supply to control on / off of the normally-on switch Q1. In this embodiment, control power is supplied to the control circuit CC from both ends of the load circuit LC.

  The control switch CS is means for switching the normally-on switch Q1 on and off. That is, if the gate of normally-on switch Q1 is connected to the connection point of impedance element Z1 and inductor L1 by turning on control switch CS, a negative voltage is applied to the gate of normally-on switch Q1 with respect to the source. Therefore, the normally-on switch Q1 is turned off. Further, when the control switch CS is turned off and the gate of the normally-on switch Q1 is released from the connection to the connection point between the impedance element Z1 and the inductor L1, or is at the same potential as the source, the normally-on switch Q1 is turned on.

  Matching means MC is interposed between impedance element Z1 and control switch CS, and turns on control switch CS when the increased current reaches the first predetermined value. Further, the control switch CS is turned off when the reduced current reaches the second predetermined value.

  Therefore, when the terminal voltage of the impedance element Z1 reaches the first predetermined value when the increased current is flowing, the matching unit MC turns on the control switch CS, so that the normally-on switch Q1 is turned off. Further, when the terminal voltage of the impedance element Z1 reaches the second predetermined value while the reduced current is flowing, the matching unit MC turns off the control switch CS, so that the normally-on switch Q1 is turned on.

  Next, circuit operation will be described.

  When the DC power source DC is turned on, the normally-on switch Q1 of the chopper CH is turned on, current flows out from the DC power source DC in the first circuit A, and the current increases linearly. This is an increased current, and electromagnetic energy is accumulated in the inductor L1. When the increased current begins to flow through the first circuit A, the terminal voltage of the impedance means Z1 increases in proportion to the increased current. When the terminal voltage reaches the first predetermined value, the matching means MC turns on the control switch CS.

  When the control switch CS is turned on, the gate of the normally on switch Q1 becomes a negative voltage, so that the normally on switch Q1 is turned off and the increased current is cut off. As a result, the electromagnetic energy accumulated in the inductor L1 is released, and a current begins to flow in the second circuit B, and the current decreases linearly. This is the reduced current. When the reduced current reaches the second predetermined value, the matching means MC turns off the control switch CS.

  When the control switch CS is turned off, the application of the negative voltage to the gate of the normally-on switch Q1 is released, so the normally-on switch Q1 is turned on and the increased current starts flowing again. Thereafter, the above circuit operation is repeated to continue the DC-DC conversion operation.

  With reference to FIG. 2, the 2nd form in the LED lighting device of this invention is demonstrated.

  In the present embodiment, the control circuit CC is different from the first embodiment. In the figure, the same parts as those in FIG.

  In this embodiment, the control circuit CC is composed of a P-type FET 1 and an N-type FET 2 to which a control switch CS is connected in parallel. The connection end of the drain of the P-type FET 1 and the source of the N-type FET 2 is connected to the gate of the normally-on switch Q1.

  The matching circuit MC is configured by a hysteresis comparator CPh. The hysteresis comparator CPh has an inverting input terminal connected to one end of the impedance means Z1 on the load circuit LC side, a non-inverting input terminal connected to the reference potential E, and an output terminal connected to the gates of the P-type FET1 and the N-type FET2. Connected. Further, a feedback resistor R1 whose resistance value has been adjusted in advance is connected between the non-inverting input terminal and the output terminal. The reference potential E is formed at the connection point of a voltage divider VD composed of resistors R2 and R3 connected in parallel to the series part of the load circuit LC and impedance means Z1.

Then, when the normally-on switch Q1 is increased current I _U to the impedance means Z1 flows on, the terminal voltage of the impedance means Z1 reaches the first predetermined value, the inverting input terminal of the hysteresis comparator CPh A positive first predetermined value voltage is input to, and a negative maximum output voltage is output to the output terminal. Since this negative maximum output voltage is applied to the gate of the P-type FET 1 of the control switch CS, the P-type FET 1 is turned on. At this time, the N-type FET 2 remains off.

When the P-type FET 1 is turned on, the normally-on switch Q1 has a negative potential, so the normally-on switch Q1 is turned off and the increased current _IU is cut off. Along with this, a reduced current _ID flows from the inductor L1. Since the terminal voltage of the impedance means Z1 when the reduced current _ID is flowing is input to the inverting input terminal of the hysteresis comparator CPh subsequently to the terminal voltage of the increased current, when the value reaches the second predetermined value, This time, the maximum positive voltage is output from the output terminal of the hysteresis comparator CPh. As a result, the P-type FET 1 is turned off and the N-type FET 2 is turned on.

  As a result of turning off the P-type FET 1 and turning on the N-type FET 2, the normally-on switch Q 1 is turned on, so that an increased current flows again to the load circuit LC. Thereafter, the above operation is repeated to perform the chopper operation.

Next, with reference to FIG. 3, the relationship between the current and voltage waveform of each part in the second embodiment of the present invention will be described. That, (a) shows the increased current _{I U} of the waveform of FIG. 3, (b) the waveform of the decreased current _{I D,} (c) is a waveform of the terminal voltage _{V Z1} impedance means, (d) the voltage of the inductor _{V L1} (E) is a waveform of the normally-on switch gate voltage V _GS , and the time axes are aligned. Incidentally, in the figure, it corresponds to when the peak value of the current increases I _U reaches a first predetermined value. Further, this corresponds to the case where the zero value of the decrease current _ID reaches the second predetermined value.

  The current waveform diagram of FIG. 3 is an ideal waveform when there is no delay in control. However, when a delay that cannot be ignored occurs in the control when the increased current is interrupted, the control delay is delayed from the peak value. There is a first predetermined value at a position lower by the corresponding value. In addition, when a delay that cannot be ignored occurs in the control when the reduced current reaches the second predetermined value, a current cutoff time corresponding to the control delay is generated between the reduced current and the next increased current. Occurs.

  With reference to FIG. 4, the 3rd form in the LED lighting device of this invention is demonstrated.

  In the present embodiment, the control circuit CC is different from the second and second embodiments. In the figure, the same parts as those in FIG.

  That is, the control switch CS is mainly composed of the bipolar transistor Q2. In the bipolar transistor Q2, the collector is connected to the gate of the normally-on switch Q1, the source is connected to the source of the normally-on switch Q1 via the control power supply Vdd consisting of a dropper, and the emitter is connected to the connection point of the inductor L1 and the impedance means Z1. is doing.

  The matching means MC is mainly composed of a bipolar transistor Q3 and resistors R4 and R5. The collector of the bipolar transistor Q3 is connected to the base of the bipolar transistor Q2 of the control switch CS via the resistor R4, the emitter is connected to the connection point of the inductor L1 and the impedance means Z1, and the base is connected to the bipolar transistor via the resistor R6. Connected to the collector of Q2. A series circuit of resistors R5 and R4 and a collector / emitter of the bipolar transistor Q3 is connected in parallel to the impedance means Z1.

  Thus, when the normally-on switch Q1 is turned on and an increasing current is flowing, the bipolar transistor Q2 of the control switch CS is turned off and the bipolar transistor Q3 of the matching means MC is turned on. Therefore, the terminal voltage of the impedance means Z1 is divided by the series circuit of the resistor R4 and the resistor R5, and the voltage across the resistor R4 is applied between the base and emitter of the bipolar transistor Q2.

  Therefore, by adjusting the values of the resistors R4 and R5 in advance and setting the value of the resistor R4 to be relatively small, the bipolar transistor Q2 is at a level before the increased current reaches the first predetermined value. Can be configured to be turned off. However, when the increased current reaches the first predetermined value, the bipolar transistor Q2 is turned on and a negative voltage is applied to the gate of the normally-on switch Q1, so that the normally-on switch Q1 is turned off and the increased current is cut off. Is done.

  When the bipolar transistor Q2 is turned on, the bipolar transistor Q3 is turned off. Therefore, when the normally-on switch Q1 is turned off and a decreasing current flows, the bipolar transistor is not divided into the terminal voltage of the impedance means Z1. The voltage is applied to Q2, and the bipolar transistor Q2 continues to be on. However, when the terminal voltage of the impedance means Z1 decreases and reaches the second predetermined value, the bipolar transistor Q2 is turned off without being able to maintain the on state. As a result, the normally-on switch Q1 is turned on again. Thereafter, the above circuit operation is repeated and the chopper operation is continued.

  DESCRIPTION OF SYMBOLS 1 ... P-type FET, 2 ... N-type FET, A ... 1st circuit, B ... 2nd circuit, C1 ... Smoothing capacitor, C2 ... Output capacitor, CC ... Control means, CH ... Chopper, CPh ... Hysteresis comparator, CS ... control switch, D1 ... freewheel diode, DC ... DC power supply, DB ... rectifier circuit, L1 ... inductor, LED ... light emitting diode, LC ... load circuit, MC ... matching circuit, Q1 ... normally-on switch, Z1 ... current detection Impedance means

Claims (3)

DC power supply;
It has a normally-on switch, inductor, freewheeling diode, and impedance element for current detection. When the normally-on switch is turned on, an increased current flows through the inductor, and when the normally-on switch is turned off, a decreased current flows from the inductor to perform chopper operation. A chopper in which the power supply voltage is DC-DC converted and output to the output terminal, and the current detecting impedance element is inserted at a position on the circuit through which the increased current and the decreased current flow;
A load circuit comprising a parallel circuit of a light emitting diode and an output capacitor connected to the output of the chopper;
The control switch includes a control switch and matching means. The control switch applies a negative voltage to the gate of the normally-on switch at least when the switch is on to control the normally-on switch to an off state, and applies a negative voltage to the gate of the normally-on switch when the switch is off. And the matching means is interposed between the impedance element and the control switch, and when the increased current is flowing, the terminal voltage of the impedance element is a first predetermined value. A control circuit that turns on the control switch when reaching a value and turns off the control switch when a second predetermined value lower than the first predetermined value is reached when the reduced current is flowing;
The LED lighting device characterized by comprising.   2. The LED lighting device according to claim 1, wherein the control circuit is configured such that the matching means is a hysteresis comparator. A lighting device body;
The LED lighting device according to claim 1 or 2, wherein the LED lighting device is disposed in a lighting device body;
An illumination device comprising:

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