JP5561467B2 - LED lighting device - Google Patents

Description

  The present invention relates to an LED lighting device including a non-insulated step-down chopper.

  A light-emitting diode lighting device including a non-insulated step-down chopper is known (for example, see Patent Document 1). In the light-emitting diode lighting device including the step-down chopper described in FIG. 2 of Patent Document 1, a resistance element 61 having a small resistance value is connected between the FET 5 serving as the first switching element and the first inductor 7. The resistor element 61 is connected between the base and emitter of the bipolar transistor 21 which is the second switching element. The collector of the transistor 21 is connected to the gate terminal of the FET 5. The first inductor 7 and the free wheel diode 11 are connected in series between the output terminals.

  When the FET 5 is turned on, the increased current flows from the DC power source 4 through the resistor element 61, the first inductor 7 and the capacitor 9 connected in parallel to the load LED circuit 8, and the first inductor 7 is charged. . Then, when the voltage across the resistance element 61 reaches a bias for operating the transistor 21, the transistor 21 is turned on, whereby the FET 5 is turned off. The voltage across the resistor element 61 is used as the base bias of the transistor 21. When this voltage reaches a predetermined voltage, the transistor 21 is turned on to turn off the FET 5, so that the turn-off timing is set to the second inductor. 12 can always be accurately taken without being influenced by the voltage value induced in the circuit 12. That is, the FET 5 can always be switched accurately.

  When the FET 5 is turned off, the electromagnetic energy stored in the first inductor 7 is released through the free wheel diode 11 and a reduced current is continuously supplied to the capacitor 9. When the reduced current becomes 0, the FET 5 is turned on again and the above operation is repeated.

  Then, when the charging voltage of the capacitor 9 becomes equal to or higher than the forward voltage of the LED circuit 8, a current flows through the LED circuit 8, and the LED of the LED circuit 8 is lit.

  An LED lighting device equipped with a non-insulated step-down chopper has a relatively simple circuit configuration, can be miniaturized, has high circuit efficiency, and easily obtains a desired low voltage. It is suitable for mounting on a bulb-type LED having an LED with a low load voltage. Bulb-shaped LEDs have recently attracted attention as light sources that replace conventional incandescent bulbs for the purpose of energy saving.

  It is also known that the output current of the non-insulated step-down chopper is converted into a voltage by a resistor R2 and input to the control terminal of the control circuit 24 via a diode D2 to form a current feedback configuration (see, for example, Patent Document 2). .)

  In addition to those corresponding to incandescent light bulbs equipped with E26 type caps that are commercially available for general lighting, LED bulbs are further equipped with smaller caps, for example, E17 type caps. It has been pursued.

Japanese Patent No. 4123886 Japanese Patent Laying-Open No. 2005-142137 (particularly paragraph 0029 and FIG. 5)

  In an LED lighting device using a non-insulated step-down chopper, it is effective to further reduce the size of the non-insulated step-down chopper in order to meet the demand for further miniaturization of the bulb-type LED. As a means for realizing this, it is conceivable to apply an integration technique centering on a semiconductor device.

  On the other hand, commercial AC power supplies use various values of voltage in each country, so if a light-emitting diode lighting device can be configured to adapt to various voltages with minimal design changes, it is compatible with each country. The bulb-type LED can be manufactured at a relatively low cost.

  In order to reduce the size of the inductor, the non-insulated step-down chopper is preferably configured to operate at a high frequency.

  The present invention provides an LED lighting device that integrates non-insulated step-down choppers to achieve further miniaturization, can be easily adapted to various power supply voltages, and has good control response in high-frequency operation. Is an issue.

LED lighting device of the present invention includes a DC power supply; switching element includes a first circuit for increasing current flows when the switching element comprises an impedance element and the inductor current detection in series, the inductor and the freewheel diode in series A second circuit through which a reduced current flows when the switching element is turned off ; and a control unit that controls the switching element , wherein the current detection impedance element is connected between the cathode of the free hole diode and the source of the switching element, the secondary winding of increasing current flowing through the current detection impedance element switching element is turned oN turns off the switching element when it reaches a predetermined value, and magnetically coupled to the inductor in response to a decrease the current flowing through the inductor Oh the switching element based on the induced voltage in the It is intended to be, from the power unit and the control unit is an IC with a single package, a secondary winding control power is magnetically coupled to the inductor of the IC including at least a switching element of the switching device and freewheel diode A non-insulated step-down chopper that is supplied and at least a current detecting impedance element and an inductor are externally attached to the IC; and a light emission connected to a position on the circuit through which both the increased current and the decreased current of the non-insulated step-down chopper flow. Ru Monodea which comprises a; and the diode.

  In the present invention, the DC power supply may have any configuration. For example, the DC power source may include a rectifier circuit as a main component, and may include a smoothing circuit including a smoothing capacitor if desired. In this case, the rectifier circuit is preferably a bridge-type rectifier circuit, and full-wave rectifies the AC voltage of an AC power source, for example, a commercial AC power source, to obtain DC. If desired, the rectifier circuit can be integrated in a single package of an IC described later. In this case, it is preferable to attach a smoothing capacitor externally.

  A non-insulated step-down chopper is a kind of a well-known step-down chopper circuit that converts an input DC voltage to a lower DC voltage and outputs it, but the circuit has a non-insulated structure from the input end to the output end. Yes. While the insulated step-down chopper includes an insulated output transformer, the non-insulated step-down chopper does not use an insulated output transformer as described above, which is suitable for downsizing the LED lighting device.

  The power section of the non-insulated step-down chopper, that is, the circuit section through which the power supplied to the load passes, is configured to include a switching element, a current detecting impedance element, an inductor, and a free wheel diode. The power section can be divided into a first circuit and a second circuit in terms of circuit operation. The first circuit is a circuit that charges an inductor from a DC power source, that is, stores electromagnetic energy, and has a configuration in which a series circuit including a switching element, a current detecting impedance element, an inductor, and a load circuit is connected to the DC power source. Thus, when the switching element is turned on, an increased current flows from the DC power source, and electromagnetic energy is accumulated in the inductor. On the other hand, the second circuit is a circuit that releases the electromagnetic energy accumulated in the inductor, and has a configuration in which a series circuit of a free wheel diode and a load circuit is connected to the inductor, and the switching element is turned off. Sometimes a reduced current flows from the inductor.

  In the above, the load circuit is loaded with a light emitting diode described later, but can include an output capacitor connected in parallel to the light emitting diode as desired. The output capacitor bypasses a high frequency generated mainly due to switching so as not to flow to the light emitting diode of the load.

  The inductor is provided with a secondary winding magnetically coupled thereto. When an increase current and a decrease current flow through the inductor, a voltage is induced in the secondary winding as will be described later. The secondary winding is allowed to be one or plural. The number of secondary windings can be appropriately selected according to the configuration of the control unit. In the present invention, the secondary winding supplies control power to the control unit and forms an ON signal for the switching element.

  The control unit is a means for controlling the operation of the non-insulated step-down chopper by controlling on and off of the switching element, and the specific circuit configuration is not particularly limited in the present invention. Control power is supplied. Then, in order to turn on and off the switching element, when the increased current flowing through the current detection impedance element reaches a predetermined value, the switching element is turned off.

  In order to turn off the switching element when the increased current reaches the first predetermined value, for example, the control terminal of the switching element is short-circuited by a switching element such as a bipolar transistor that responds to the terminal voltage of the current detection impedance element. In addition, if a comparator is interposed between the current detection impedance element and the switch element in order to cause the switch element to respond as described above, even if the terminal voltage of the current detection impedance element is a very small value, the switch element is turned off. Can be performed reliably. As a result, since the power loss of the current detecting impedance element is reduced, the circuit efficiency is increased, the temperature characteristic is not affected by the switch element, and the temperature characteristic is improved. The switch element and the comparator can be operated by a control power source supplied from the secondary winding of the inductor.

  On the other hand, in order to turn on the switching element, the following control may be performed. That is, when the reduced current flowing from the inductor becomes 0, a voltage due to the back electromotive force is induced in the secondary winding. Based on this voltage, an ON signal of the switching element is formed and supplied to the switching element. And turn it on. The ON signal can be formed by directly or indirectly using a voltage induced in the secondary winding.

  In the present invention, at least the switching element and the above-described control unit among the circuit components constituting the power element of the switching element, the current detection impedance element, and the free wheel diode constitute an IC having a single package. Note that the current detecting impedance element is externally attached to the IC for the reason that it is a component subject to design change so as to correspond to various power supply voltages.

  Inductors are so-called power components because load power passes through them in the same way as the circuit components of the power section described above. However, the inductor is a component subject to design change to accommodate various power supply voltages. Externally. In addition, since the inductor is larger than the semiconductor component, there is also a reason that it is difficult to adapt to the IC.

  In addition, when the switching element and the free wheel diode in the power section are integrated into an IC, the switching element and the free wheel diode that are complementary in operation can be obtained by configuring the semiconductor device to share heat dissipation means. , And can be thermally coupled through heat dissipation means. As a result, the amount of heat generated by the IC is substantially constant regardless of fluctuations in the power supply voltage, so that the size can be reduced by sharing the heat dissipating means.

  In the present invention, a light emitting diode and a switching element, which will be described later, can be thermally coupled if desired. In other words, when the light emitting diode is in a failure mode and abnormally generates heat, the temperature of the thermally coupled switching element is excessively raised to destroy the switching element so that the circuit can be in the open mode. it can. Thereby, it is possible to cause the switching element that controls switching of the LED lighting circuit to perform a protection operation when the light emitting diode is abnormal.

  If the thermal coupling is performed via the heat dissipation means of the light emitting diode, the distance between the light emitting diode and the switching element can be freely set to some extent. The degree of freedom is improved.

  Since the IC includes the control unit of the switching element, the distance of the conductor connecting the switching element and the control unit is remarkably shortened. As a result, the resistance of the conductor connecting between them and the floating capacitance Becomes smaller. As a result, it is effective in reducing signal delay due to resistance and reactance of the conductor pattern.

  The light-emitting diode is energized and lit by the constant-current controlled output current of the non-insulated step-down chopper by connecting to the position on the circuit through which both the increasing current and the decreasing current of the non-insulating step-down chopper flow. The light emitting diode may be a series circuit in which a plurality of the light emitting diodes are connected in series, or may be a single light emitting diode. Further, a plurality of these may be connected in parallel via a uniformed shunt circuit or the like to constitute a load circuit.

  In addition, since the light emitting diode is not particularly limited in its light emission characteristics, package mode, and the like, various known light emission characteristics, package modes, ratings, and the like can be appropriately selected and used. However, white light emitting diodes are generally used for general illumination.

In the present invention described on the following, IC allows that the power unit and the control unit is configured by separate semiconductor chips. That is, the semiconductor chip of the power unit can be set to a relatively high voltage specification, and the semiconductor chip of the control unit can be set to a relatively low voltage specification. When the power unit includes a switching element and a free wheel diode, they may be integrated on a common semiconductor chip or a different semiconductor chip may be provided.

In the present invention, a free wheel diode is externally attached to the IC. Thereby, it is possible to design a freewheel diode having an optimum specification according to the power supply voltage and the load power.

The LED lighting device of the present invention can be incorporated in a lighting fixture. In this case, the luminaire is a concept including an LED bulb, and includes a luminaire main body and an LED lighting device. The lighting fixture uses LED as a light source, and its use is generally for lighting purposes, but is not limited thereto. The luminaire main body refers to all remaining portions from which the LED lighting device is removed from the luminaire .

In the present invention, due to the provision of the non-isolated step-down chopper configured power and control parts in IC provided in a single package containing at least the switching element of the switching element and the freewheel diode, the non-isolated buck To provide an LED lighting device that can be further miniaturized and that can easily be adapted to various power supply voltages since an impedance element for current detection and an inductor are externally attached to the IC. Can do .

It is a circuit diagram of the 1st form for carrying out the LED lighting device of the present invention. It is the typical circuit arrangement | positioning figure centering on IC similarly. It is a circuit diagram of the 2nd form for implementing the LED lighting device of the present invention. It is the typical circuit arrangement | positioning figure centering on IC similarly.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  The first form shown in FIG. 1 corresponds to the first invention. The LED lighting device includes a DC power source DC, a non-insulated step-down chopper SDC, and a light emitting diode LED.

  The DC power source DC includes a full-wave rectifier circuit DB and a smoothing capacitor C1 whose input ends are connected to an AC power source AC such as a commercial AC power source having a rated voltage of 100V. The smoothing capacitor C1 can be connected between the output terminals of the full-wave rectifier circuit DB to form a smoothed voltage including an appropriate ripple on the DC output of the full-wave rectifier circuit DB. Also, a noise prevention capacitor C2 is connected between the input terminals of the full-wave rectifier circuit DB.

  The non-insulated step-down chopper SDC includes a first circuit A, a second circuit B, and a control unit CC. The first circuit A includes a switching element Q1, a current detecting impedance unit Z1 and an inductor L1 in series, and is connected to a DC power source DC and a light emitting diode LED of a load described later so that an increased current flows when the switching element Q1 is turned on. To do. The second circuit B includes an inductor L1 and a freewheel diode D1 in series, and a reduced current flows when the switching element Q1 is turned off. The control unit CC controls the switching element Q1, and is supplied with control power from a secondary winding L2, which will be described later, to drive the non-insulated step-down chopper SDC by self-excitation.

  The non-insulated step-down chopper SDC has its terminals D and E connected to the output terminal of the DC power source DC, its terminal Vdd connected to one end on the control unit CC side of the secondary winding L2, and its terminal out connected to the inductor L1. Is connected to one end on the freewheel diode D1 side, and the terminal CS is connected to one end on the switching element Q1 side of the impedance element for current detection Z1. The other end of the secondary winding L2 connected to the inductor L1 and the other end on the freewheel diode D1 side of the impedance element for current detection Z1 are connected as shown in the figure. The other end of the inductor L1 and the terminal E are connected to the output terminals t1 and t2. An output capacitor C2 is connected to the output terminals t1 and t2.

  Further, in the non-insulated step-down chopper SDC, a range indicated by a dotted line in the figure surrounded by the terminals D, Vdd, CS, out and A is constituted by an IC 10 which will be described later.

  In this embodiment, the switching element Q1 of the non-insulated step-down chopper SDC is composed of an FET (field effect transistor), and a pair of main terminals (drain and source) are connected in series to the first circuit A. The first circuit A forms a charging circuit for the inductor L1 via the output capacitor C2 and / or a load circuit LC described later, and the second circuit B receives the inductor L1 and the freewheel diode D1 via the output capacitor C2. Thus, a discharge circuit of the inductor L1 is formed. In this embodiment, the current detecting impedance unit Z1 is formed of a resistor, but an inductor or a capacitor having an appropriate resistance component can be used as desired.

  The desired number of light-emitting diodes LED are connected in series and connected in parallel with the output capacitor C2 to form a load circuit LC, which is connected between the output terminals t1 and t2 of the non-insulated step-down chopper SDC. Lights up by being energized by the output current of the step-down chopper SDC.

  Control unit CC includes a drive circuit GD of switching element Q1 and a turn-off circuit TOff, receives control power from secondary winding L2 magnetically coupled to inductor L1, and is based on a voltage induced in secondary winding L2. Thus, an on / off signal of the switching element Q1 is formed.

  The drive circuit GD applies a voltage induced in the secondary winding L2 as a drive signal between the control terminal (gate) of the switching element Q1 and one main terminal (drain) while the increased current flows. The switching element Q1 is kept on. The other end of the secondary winding L2 is connected to the other main terminal (source) of the switching element Q1 via the impedance means Z1. In addition to the above configuration, a capacitor C3 is interposed in series between one end of the secondary winding L2 and the control terminal (gate) of the switching element Q1. Further, a Zener diode ZD1 is connected between the output terminals of the control unit CC so that an overvoltage is applied between the control terminal (gate) of the switching element Q1 and one main terminal (drain) so that the switching element Q1 is not destroyed. An overvoltage protection circuit is formed.

  The turn-off circuit TOff includes a comparator CP1, a switch element Q2, and first and second control circuit power supplies ES1 and ES2. The reference voltage circuit is connected to the inverting input terminal of the comparator CP1. The reference voltage circuit includes a Zener diode ZD2, and receives a power supply from the second control circuit power supply ES2 to generate a reference voltage to generate a reference voltage. A connection point between the first switching element Q1 and the current detecting impedance unit Z1 is connected to the non-inverting input terminal of the comparator CP1, and an input voltage is applied to the comparator CP1. The output terminal of the comparator CP1 is connected to the base of a switch element Q2, which will be described later, and an output voltage is applied to turn it on. Note that the base of the switch element Q2 is connected to the first control circuit power supply ES1 via the resistor R1 to supply control power to the comparator CP1.

  The switch element Q2 is composed of a bipolar transistor, the collector of which is connected to the control terminal of the switching element Q1, and the emitter of which is connected to the connection point between the current detecting impedance element Z1 and the inductor L1. Therefore, when the switch element Q2 is turned on, the output terminal of the drive circuit GD is short-circuited. As a result, the switching element Q1 is turned off.

  The first control circuit power supply ES1 is configured by connecting a series circuit of a diode D2 and a capacitor C4 to both ends of the secondary winding L2, and is generated in the secondary winding L2 when the inductor L1 is charged. The capacitor C4 is charged via the diode D2 with the induced voltage.

  The second control circuit power source ES2 is configured in the same manner as described above by connecting a series circuit of a diode D3 and a capacitor C5 to both ends of the secondary winding L2.

  The start-up circuit ST includes a resistor R2 connected between the drain and gate of the switching element Q1, and includes a capacitor C3, a secondary winding L2, an inductor L1, and an output capacitor C2, and is mainly a resistor when the DC power source DC is turned on. A positive starting voltage determined by R2 is applied to the gate of the switching element Q1, and the non-insulated step-down chopper SDC is started.

  Next, circuit operation will be described.

  In the DC power source DC, the capacitance of the smoothing capacitor C1 is set to a relatively low value, for example, and the fifth harmonic ratio of the input current waveform is 60% or less. As a result, the harmonic of the input current waveform is Japan. Satisfies the harmonic standard (JIS C61000-3-2 Class C) of 25W or less.

  When the DC power source DC is turned on and the non-insulated step-down chopper SDC is started up by the starting circuit ST, the switching element Q1 is turned on, and the output capacitor C2 and / or the load circuit LC of the first circuit A from the DC power source DC is turned on. An increasing current increases linearly through the light emitting diode LED. Due to this increased current, a positive voltage is induced in the secondary winding L2 on the capacitor C3 side, and this induced voltage applies a positive voltage to the control terminal (gate) of the switching element Q1 via the capacitor C3. The switching element Q1 is maintained in the on state and the increased current continues to flow. At the same time, a voltage drop occurs in the current detecting impedance means Z1 due to the increased current, and the dropped voltage is applied as an input voltage to the non-inverting input terminal of the comparator CP1 of the turn-off circuit TOff.

  When the input voltage of the comparator CP1 increases as the increase current increases and exceeds a reference voltage set to a predetermined value, the comparator CP1 operates and a positive output voltage is generated at its output terminal. As a result, the switch element Q2 of the turn-off circuit TOff is turned on and the output terminal of the drive circuit GD is short-circuited, so that the switching element Q1 of the non-insulated step-down chopper SDC is turned off and the increased current is cut off.

  When the switching element Q1 is turned off, the electromagnetic current stored in the inductor L1 is released by the increase current flowing during the on period, and the inside of the second circuit B including the inductor L1 and the freewheel diode D1 is output. A reduced current flows out via the capacitor C2 and / or the light emitting diode LED of the load circuit LC. At this time, since the control terminal (gate) of the switching element Q1 is at a negative potential, the switching element Q1 is maintained in the OFF state, and the reduced current continues to flow.

  When the emission of the electromagnetic energy accumulated in the inductor L1 ends and the reduced current becomes zero, a positive counter electromotive force is generated in the inductor L1, and the voltage induced in the secondary winding L2 is reversed. Since the capacitor C4 side again turns positive, when this induced voltage is applied to the control terminal (gate) of the switching element Q1 via the capacitor C3, the switching element Q1 is again turned on and increased again. Current begins to flow.

  Thereafter, the circuit operation similar to the above is repeated, the increased current and the decreased current are combined, and the load current having a triangular waveform flows, whereby the light emitting diode LED of the load circuit LC is lit.

  Next, the IC 10 will be described with reference to FIG. The IC 10 constitutes an IC including a single package P including the switching element Q1 of the non-insulated step-down chopper SDC and the power part of the freewheel diode D1 and the control part CC. The circuit components are connected in the manner shown in FIG. 1 inside the IC 10, and the connection pins D, E, out, CS, and Vdd are led out to the outside.

  The switching element Q1 and the freewheel diode D1 are mounted on the high voltage chip, but the control unit CC is mounted on the low voltage chip. Note that the switching element Q1 and the free wheel diode D1 may be mounted on a single high-voltage chip, or may be mounted on different high-voltage chips.

  Then, the DC power source DC, the current detection impedance element Z1, the inductor L1, and the output capacitor C2 are connected to the connection pins D, E, out, CS, and Vdd of the IC 10 as shown in the figure, thereby providing a non-insulated step-down chopper. SDC is configured.

  Next, the 2nd form for implementing the LED lighting device of this invention with reference to FIG. 3 and FIG. 4 is demonstrated. 1 and 2 are denoted by the same reference numerals and description thereof is omitted.

  In this embodiment, the impedance element Z1 is located between the connection point of the switching element Q1 and the freewheel diode D1 and the inductor L1 as a position on the circuit where both the increased current and the decreased current of the non-insulated step-down chopper SDC flow in a non-smooth state. Is inserted in series. The control unit CC is configured so that the switching element Q1 is turned on and off according to the voltage drop generated in the current detecting impedance element Z1.

  Further, inside the IC 10, a dropper, for example, a voltage divider composed of a series circuit of resistors R3 and R4 connected to a DC power source DC and a capacitor C6 connected in parallel to the resistor R4 are provided, and a control power source is obtained from both ends of the capacitor C6. A power generation unit VdS is provided to supply control power to the control unit CC.

  When the switching element Q1 is turned on and the increased current flowing through the current detection impedance element Z1 reaches the first predetermined value, the control unit CC turns off the switching element Q1, and the decreased current flowing during the off period is the first current. When the second predetermined value is smaller than the predetermined value (for example, 0), the switching element Q1 is turned on again, and thereafter the on / off control of the switching element Q1 is repeated at a high frequency.

  In the present embodiment described above, since the control power supply is created inside the IC 10, the IC 10 has four connection pins.

  DESCRIPTION OF SYMBOLS 10 ... IC, A ... 1st circuit, B ... 2nd circuit, C1 ... Smoothing capacitor, C2 ... Output capacitor, CC ... Control means, CP1 ... Comparator, D1 ... Freewheel diode, CS, D, E, out , Vdd ... connection terminal, D2, D3 ... diode, DC ... DC power supply, DB ... full-wave rectifier circuit, DG ... drive circuit, ES1 ... first control circuit power supply, ES2 ... second control circuit power supply, L1 ... inductor L2 ... secondary winding, LED ... light emitting diode, LC ... load circuit, PM ... power module, Q1 ... switching element, Q2 ... switch element, SDC ... step-down chopper, ST ... start-up circuit, t1, t2 ... output terminal, TOff: Turn-off circuit, Z1: Impedance means for current detection

Claims (3)

DC power supply;
Switching element, a first circuit which increases current flows during on of the switching element comprises an impedance element and the inductor current detection in series, the reduction current flows when off of the switching element includes said inductor and the freewheel diode in series 2 and a control unit for controlling the switching element , wherein the impedance element for current detection is connected between a cathode of the free hole diode and a source of the switching element, and the control unit includes the switching element. induced but turns off the switching element when an increase current turned on flows through the current detecting impedance element reaches a predetermined value, the secondary winding which is magnetically coupled to the inductor in response to a decrease current flowing through the inductor the scan based on the the voltage Is intended to turn on the switching element, wherein the power unit and the control unit including at least the switching element of the switching element and the freewheel diode and an IC provided in a single package, the control power of the IC is the the inductor is supplied from the secondary winding which is magnetically coupled to a non-isolated step-down chopper is external with respect to at least the current detecting impedance element contact and said inductor said IC;
Wherein the light emitting diode current increases and decreases a current of the non-insulated type step-down chopper is connected to a position on the circuit flowing together;
The LED lighting device characterized by comprising . The IC, the power unit and the control unit and the claim 1 Symbol mounting of the LED lighting device, characterized in that it is constituted by separate semiconductor chips. The freewheel diode, LED lighting device according to claim 1 or 2, wherein it is configured to be externally attached to the IC.

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