JP4726609B2 - Light emitting diode driving device and light emitting diode driving semiconductor device - Google Patents

Description

  The present invention relates to a light emitting diode driving device and a light emitting diode driving semiconductor device for driving a light emitting diode used in a lighting device or the like.

  In recent years, for example, as an indoor or outdoor lighting device, a lighting device using one or a plurality of light emitting diodes (LEDs) in combination for the purpose of power saving has been widely used. A light emitting diode driving device for driving a light emitting diode used in a lighting device, and a light emitting diode driving semiconductor device in which a circuit configuration having the function is formed on a single substrate using a semiconductor or the like have been developed, It has been put into practical use.

  The above-described conventional light emitting diode driving device and light emitting diode driving semiconductor device will be described below with reference to the drawings.

  FIG. 13 is a circuit diagram showing a first example of a conventional light emitting diode driving device (illumination device) (see, for example, Patent Document 1). The circuit configuration of the light-emitting diode driving device shown in FIG. 13 includes a light-emitting diode 102 and a coil 103 connected in series to the light-emitting diode 102. A diode 104 is connected in parallel to the light emitting diode 102 and the coil 103. The diode 104 is provided to supply the counter electromotive force generated in the coil 103 to the light emitting diode 102.

  Further, a power supply unit that applies a pulse voltage to the light emitting diode 102, the coil 103, and the diode 104 is provided. The power supply unit is a switching element that switches application / non-application of the output voltage of the DC power supply 101 and the DC power supply 101. 105. The switching element 105 is composed of, for example, a switching transistor and an oscillator. The diode 104 is configured such that the cathode side is connected to the positive electrode side of the DC power supply 101 and a reverse bias is applied.

  When the switching transistor is turned on by the switching element 105, the light emitting diode driving device configured as described above causes the light emitting diode 102 to emit light by applying the output voltage from the DC power supply 101, and the switching transistor is turned off. When it is, the light emitting diode 102 is caused to emit light using the back electromotive force of the coil 103.

  Next, another conventional light emitting diode driving device and light emitting diode driving semiconductor device will be described below with reference to the drawings.

  FIG. 14 is a circuit diagram showing a second example of a conventional light emitting diode driving device (for example, see Patent Document 2). The circuit configuration of the LED driving device shown in FIG. 14 is that the step-up chopper BUT including the inductor L, the switching element (MOSFET) Q, the diode D, and the control circuit controls the on / off operation of the switching element Q. The storage and release of electromagnetic energy by the inductor L are controlled, and the current is supplied from the inductance L to the light emitting diode LED.

  In this case, the switching element Q is turned off by detecting the current flowing through the light-emitting diode LED by the resistor LD and passing through the error amplifier EA, the integration circuit ICC, and the multiplier M to one end (−side input). Terminal) and the current flowing through switching element Q is detected by resistor SD and input to the other end (+ side input terminal) of comparison circuit CP, and the comparison result of comparison circuit CP is sent to bistable multivibrator BM. This is done by typing.

  On the other hand, for the on-control of the switching element Q, the detection winding LD magnetically coupled to the inductor L detects that the voltage at both ends of the detection winding LD changes in a step-like manner after the inductor L releases energy, and is bistable. This is done by inputting to the multivibrator BM.

The light emitting diode driving device configured as described above stores energy in the inductor L when the switching element Q is on, and uses the back electromotive force of the inductor L when the switching element Q is off. To cause the light emitting diode LED to emit light.
Japanese Patent Laid-Open No. 2001-8443 JP 2001-313423 A

  However, in the light emitting diode driving apparatus (FIG. 13) of the first example in the conventional example as described above, the switching element 105 is simply a combination of a switching transistor and an oscillator, and the switching element is based on a predetermined timing of the oscillator. The on / off timing of 105 is determined. For this reason, if the time during which the switching element 105 is on is too long, the value of the current flowing through the LED 102 increases, and the maximum current value allowed for the LED 102 may be exceeded, causing destruction.

  Further, in order to make the average current flowing through the light emitting diode 102 constant even when the output voltage value of the power supply unit is different, the oscillation frequency of the oscillator and the inductance value of the coil 103 are set according to the output voltage value of the power supply unit. Must be changed. Therefore, when a commercial power supply is used for the power supply unit, the power supply voltage value such as AC100V / AC200V varies greatly depending on the region. Therefore, the oscillation frequency of the oscillator and the inductance value of the coil 103 must be changed each time.

  In addition, when the LED 102 is driven using a voltage rectified by a rectifier circuit or the like using a commercial power supply, the rectified voltage changes greatly, and thus a stable operation cannot be maintained particularly when the voltage becomes low. In order to avoid this problem, it is necessary to add a smoothing capacitor after the rectifier circuit. In this case, the noise terminal voltage level caused by the harmonic current increases, so a separate noise countermeasure circuit is required. As the circuit scale increases, the configuration becomes complicated.

  Further, in the light emitting diode driving device (FIG. 14) of the second example in the above conventional example, the current flowing through the light emitting diode LED is detected by the resistor LD, and the current flowing through the switching element Q is detected by the resistor SD. The power loss due to these resistors increases the power loss of the entire device.

  Furthermore, since it is a step-up chopper method and operates in a discontinuous or current critical mode, the light emitting diode LED emits light only during the period when the switching element Q is off. Since the peak current value flowing to L is less than half of the value, the ability of the light emitting diode cannot be maximized, and no current flows through the LED while the switching element is on. Power conversion efficiency is poor.

  Furthermore, since the inductor L detects that the voltage at both ends of the detection winding LD changes in a step-like manner after the energy is released by the coupling winding LD magnetically coupled to the inductor L, such a configuration is necessary and the circuit scale is increased. Becomes larger.

  The present invention solves the above-mentioned conventional problems, and with a simple configuration, the peak current value flowing through the LED and the ripple width of the pulsating current can be easily controlled, and constant current driving is possible with an average current. The present invention provides a light-emitting diode driving device and a light-emitting diode driving semiconductor device that can suppress power loss.

  In order to solve the above problems, a light emitting diode driving device according to claim 1 of the present invention includes a light emitting diode block having one or a plurality of light emitting diodes, and a transformer connected in series to the light emitting diode block. Connected to one terminal of the series connection circuit loop, and a series connection circuit loop composed of a primary coil and a diode for supplying back electromotive force generated in the primary coil of the transformer to the light emitting diode block A switching power supply unit for applying a voltage to the transformer and the light emitting diode block, and a switching drive circuit connected to the other terminal of the series connection circuit loop for intermittently supplying a current to the light emitting diode block The switching drive circuit has one end at the front. A first switching element connected to the series connection circuit loop, the other end of which is connected to the reference potential of the power supply unit, and the other end of the secondary coil of the transformer whose one end is connected to the reference potential of the power supply unit The first current detection circuit that outputs a bottom value detection signal when the current flowing through the secondary coil of the transformer falls below a preset value, and the current flowing through the first switching element is preset. A second current detection circuit that outputs a peak value detection signal when the value exceeds a predetermined value, and the first current detection circuit connected to a high potential side terminal, a control terminal, and a low potential side terminal of the first switching element. In response to a bottom value detection signal from the circuit, the first switching element is turned on, and in response to a peak value detection signal from the second current detection circuit, the first switching element is turned off. A control circuit that outputs a control signal to a control terminal of the first switching element, a constant current source connected to one end of the series connection circuit loop, and a second end connected to the other end of the constant current source. And a regulator that generates an operating voltage of the switching drive circuit, and a capacitor having one end connected to the regulator and the control circuit and the other end connected to a reference potential of the power supply unit.

  The light emitting diode driving device according to claim 2 of the present invention is the light emitting diode driving device according to claim 1, wherein the first current detection circuit is a current flowing through the secondary side coil of the transformer. An I-V conversion circuit for converting a voltage into a voltage, a first comparator in which an output signal of the IV conversion circuit is input to a positive input terminal, and a first reference voltage is input to a negative input terminal; And a NOR circuit in which an output of one comparator is input to one input terminal and a control signal of the control circuit is input to the other input terminal.

  According to a third aspect of the present invention, there is provided a light emitting diode drive device comprising: a light emitting diode block having one or a plurality of light emitting diodes; a choke coil connected in series to the light emitting diode block; A series connection circuit loop composed of a diode for supplying the generated back electromotive force to the light emitting diode block; and a voltage connected to the light emitting diode block and the choke coil connected to the series connection circuit loop. A light emitting diode driving device including a power supply unit and a switching driving circuit connected to the series connection circuit loop and configured to perform constant current control of a current flowing through the light emitting diode block, wherein the switching driving circuit has one end of the switching driving circuit Connected to a series connection circuit loop, the other end of the power supply unit A first switching element connected to a quasi-potential and a bottom value detection signal are output when the current flowing in the series connection circuit loop is less than or equal to a preset value connected to the high potential side of the first switching element. A first current detection circuit that outputs, a second current detection circuit that outputs a peak value detection signal when a current flowing through the first switching element exceeds a preset value, and a high current level of the first switching element. Connected to the potential side terminal, the control terminal, and the low potential side terminal, receives the bottom value detection signal from the first current detection circuit, turns on the first switching element, and outputs from the second current detection circuit. A control circuit for receiving a peak value detection signal and outputting a control signal for turning off the first switching element to a control terminal of the first switching element; and the series connection circuit A constant current source connected to one end of the switch and a regulator connected to the other end of the constant current source to generate an operating voltage of the switching drive circuit, and one end connected to the regulator and the control circuit The other end is provided with a capacitor connected to the reference potential of the power supply unit.

  According to a fourth aspect of the present invention, there is provided the light emitting diode driving device according to the third aspect, wherein the first current detection circuit is on a high potential side of the first switching element. And two resistors connected in series between the power supply unit and the reference potential of the power supply unit, and a DC voltage divided by the two resistors are input to the positive input terminal, and the first reference voltage is input to the negative input terminal. And a NOR circuit in which an output of the first comparator is input to one input terminal and a control signal of the control circuit is input to the other input terminal.

  Moreover, the light-emitting-diode drive device of Claim 5 of this invention is a light-emitting-diode drive device of Claims 1-4, Comprising: The said power supply part is an alternating current power supply which produces | generates an alternating voltage, The said power supply, A switching circuit that outputs a signal whose potential state changes depending on whether or not the output voltage of the rectifying circuit is equal to or higher than a predetermined value. An on / off control of the first switching element when the output signal of the input voltage detection circuit indicates that the output voltage of the rectifier circuit has reached a predetermined value or more. When the output signal of the input voltage detection circuit indicates that the output voltage of the rectifier circuit has fallen below a predetermined value, the on / off control of the first switching element is stopped. And having a start / stop circuit for outputting a signal.

  The light-emitting diode driving device according to claim 6 of the present invention is the light-emitting diode driving device according to any one of claims 1 to 5, wherein the constant current source is the first switching element. The high-potential side terminal is connected between the regulator and the regulator.

  The light-emitting diode drive device according to claim 7 of the present invention is the light-emitting diode drive device according to any one of claims 1 to 5, wherein the constant current source is an output side of the power supply unit. And the regulator.

  The light-emitting diode drive device according to claim 8 of the present invention is the light-emitting diode drive device according to any one of claims 1 to 7, wherein the second current detection circuit is the first current detection circuit. The on voltage of the switching element is compared with a second reference voltage to detect whether or not the current flowing through the first switching element has reached a preset value.

  The light-emitting diode drive device according to claim 9 of the present invention is the light-emitting diode drive device according to any one of claims 1 to 7, wherein the switching drive circuit has a high-potential side terminal connected to the light-emitting diode drive device. A control signal common to the first switching element is input from the control circuit to the control terminal in parallel with the high potential side terminal of the first switching element, and a current flowing through the first switching element is A second switching element having a small current value and a current having a constant current ratio is connected between the low potential side terminal of the second switching element and the low potential side terminal of the first switching element. The second current detection circuit compares the voltage across the resistor with a second reference voltage, and the current flowing through the first switching element reaches a preset value. And detecting whether Taka not.

  The light-emitting diode drive device according to claim 10 of the present invention is the light-emitting diode drive device according to any one of claims 1 to 9, wherein the switching drive circuit includes the first current detection. A current detection value variable circuit that varies a current detection value of the first current detection circuit by changing a first reference voltage of the circuit from the outside, and the current detection value variable circuit includes a control signal from the outside Thus, the current detection value of the first current detection circuit is varied to change the ripple width of the pulsating current flowing in the light emitting diode.

  The light-emitting diode drive device according to claim 11 of the present invention is the light-emitting diode drive device according to any one of claims 1 to 9, wherein the switching drive circuit includes the first current detection. The first reference voltage of the circuit and the second reference voltage of the second current detection circuit are changed from the outside, and the current detection values of the first current detection circuit and the second current detection circuit are varied. A current detection value variable circuit, wherein the current detection value variable circuit varies the current detection values of the first current detection circuit and the second current detection circuit according to a control signal from the outside; It is possible to adjust the light intensity.

  A light emitting diode driving device according to claim 12 of the present invention is the light emitting diode driving device according to claim 11, and outputs a control signal from the outside for controlling dimming of the light emitting diode. A dimming control circuit for controlling the current detection value of the first current detection circuit and the second current detection circuit according to the external control signal from the dimming control circuit. It is variable.

  The light-emitting diode drive device according to claim 13 of the present invention is the light-emitting diode drive device according to any of claims 5 to 12, wherein the input voltage detection circuit is an output of the power supply unit. Two resistors connected in series between the side and a reference potential, and a DC voltage divided by the two resistors is input to the positive input terminal, and a third reference voltage is input to the negative input terminal. And an output signal of the second comparator is output to the start / stop circuit.

  The light-emitting diode driving device according to claim 14 of the present invention is the light-emitting diode driving device according to any one of claims 5 to 12, wherein the input voltage detection circuit is an output of the power supply unit. The three resistors connected in series between the side and the reference potential and the first divided voltage divided by the three resistors are input to the positive input terminal, and the fourth reference voltage is input to the negative input terminal. A third comparator that is input; a fourth comparator in which the second divided voltage divided by the three resistors is input to the negative input terminal; and the fifth reference voltage is input to the positive input terminal; An AND circuit having input terminals connected to the output terminal of the third comparator and the output terminal of the fourth comparator, and outputting an output signal of the AND circuit to the start / stop circuit; And features.

  The light-emitting diode drive device according to claim 15 of the present invention is the light-emitting diode drive device according to any one of claims 1 to 14, wherein the control circuit has a temperature of the switching drive circuit. It has an overheat protection circuit that stops the on / off control of the first switching element when a predetermined value or more is reached.

  A light-emitting diode drive device according to claim 16 of the present invention is the light-emitting diode drive device according to any one of claims 1 to 15, wherein a reverse recovery time of the diode is 100 nsec or less. It is characterized by.

  According to a seventeenth aspect of the present invention, there is provided a light emitting diode driving semiconductor device having a single configuration of the switching driving circuit in the light emitting diode driving device according to any one of the first to sixteenth aspects. It is formed on a substrate.

  As described above, according to the first aspect of the present invention, when the first switching element is in the ON state, a current flows toward the switching element through the primary coil and the light emitting diode block of the transformer of the series connection circuit loop. The peak value of the element current is controlled by the second current detection circuit. On the other hand, when the switching element is in the OFF state, the current due to the counter electromotive force of the primary coil of the transformer flows to the light emitting diode block through the diode for a predetermined time and operates like a step-down chopper, and its bottom current value is The timing when the first switching element is controlled by the first current detection circuit and the first switching element is switched from on to off is defined by the current value flowing through the first switching element, and the timing when the first switching element is switched from off to on is the secondary coil of the transformer The primary coil and secondary coil of the transformer are configured with a fixed turns ratio, and a current proportional to the current flowing through the light emitting diode during the off period of the first switching element is Since it also flows to the secondary coil, detecting this current value allows it to flow to the light emitting diode. That current it is possible to define a can control the ripple width of pulsating current flowing through the light-emitting diode.

  Therefore, even when the power supply unit outputs a voltage obtained by rectifying the AC voltage from the commercial power supply, the average current flowing through the light-emitting diode block can be made constant without using a smoothing capacitor, and high-accuracy constant-current control is easy. Can be realized.

  Furthermore, since the current flowing through the light emitting diode block always flows during the ON / OFF control period of the switching element, the power conversion efficiency can be increased. Further, the noise terminal voltage level can be kept low without requiring a special circuit.

  Furthermore, even if the voltage value of the commercial power supply such as AC100V / AC200V varies greatly depending on the region, it is not necessary to change the oscillation frequency of the oscillator and the inductance value of the coil each time as in the prior art.

  According to the second invention, it is possible to detect the current flowing through the light emitting diode during the off period of the first switching element, and to easily control the ripple width of the pulsating current flowing through the light emitting diode. it can.

  According to the third aspect of the invention, since the current flowing through the light emitting diode, that is, the current flowing through the series connection circuit loop can be directly controlled while the first switching element is off, the ripple width of the pulsating current flowing through the light emitting diode is achieved. Can be controlled.

  Furthermore, since it is not necessary to use a transformer, it is possible to realize a light emitting diode driving device with high power conversion efficiency that can reduce the size of the light emitting diode driving device.

  According to the fourth aspect of the invention, since the current flowing through the light emitting diode, that is, the current flowing through the series connection circuit loop can be directly controlled while the first switching element is off, the ripple width of the pulsating current flowing through the light emitting diode is achieved. Can be controlled.

  Furthermore, since it is not necessary to use a transformer, it is possible to realize a light emitting diode driving device with high power conversion efficiency that can be further reduced in size.

  Further, according to the fifth invention, the light emitting diode driving device is started / stopped when the input voltage fluctuates greatly as in the case where the power supply unit is constituted by an AC power supply and a rectifier circuit for rectifying the AC voltage. Since the voltage at the time can be set to an arbitrary voltage value, the switching element can be stably operated in consideration of the voltage drop in the LED load connected in series.

  In addition, during one cycle of the output voltage of the rectifier circuit, the period during which current flows through the light emitting diode and the period during which current does not flow can be controlled, so that stable operation is possible without using a smoothing capacitor, and the noise terminal voltage level is reduced. It can be kept low.

  According to the sixth invention, when the constant current source, the regulator, the control circuit, the first and second current detection circuits, and the switching element are built in one semiconductor package, the number of external output terminals of the package is reduced. Therefore, it is possible to realize further high efficiency and downsizing of the light emitting diode driving device.

  Further, according to the seventh invention, power supply to the control circuit when the intermittent on / off operation of the first switching element is stopped and the light emitting diode is turned off does not go through the coil or the light emitting diode. Therefore, the effect that the light emitting diode does not emit weak light is obtained.

  According to the eighth aspect of the invention, it is not necessary to provide a resistor for detecting the current flowing through the light emitting diode as in the prior art to turn off the switching element, and power loss can be suppressed.

  In addition, by adopting a configuration in which the ON voltage of the switching element is compared with the detection reference voltage, the peak value of the element current flowing through the switching element can be detected without using a resistor, so that power loss can be reduced.

  According to the ninth invention, the second switching element for detecting the element current in which a current having a constant current ratio smaller than the element current flowing through the switching element is provided in parallel with the first switching element. As a result, the power loss can be reduced as compared with the case where the element current flowing through the switching element is directly detected by the resistance.

  According to the tenth invention, the ripple width of the pulsating current flowing in the light emitting diode can be easily controlled optimally according to the coil inductance value and the number of light emitting diodes connected in series.

  Further, according to the eleventh and twelfth inventions, the peak value of the current flowing through the light emitting diode block can be adjusted, and the luminance of the light emitting diode can be easily controlled.

  According to the thirteenth aspect, when a commercial power supply is used for the power supply unit, the light emitting / extinguishing period of the light emitting diode can be accurately controlled at a frequency (100 Hz / 120 Hz) double that of the commercial power supply. .

  According to the fourteenth aspect of the present invention, when the output voltage of the power supply section varies greatly as in the case where the power supply section is composed of an AC power supply and a rectifier circuit, the switching element is turned on with respect to the output voltage of the power supply section. Since the voltage value when starting / stopping the off control can be set individually, the switching device can be turned off to protect the driving device when an abnormal high voltage is applied from the power supply unit.

  Further, according to the fifteenth aspect, thermal destruction of the switching element due to an abnormal temperature rise can be avoided, and safety and reliability can be improved. In particular, when the light emitting diode driving device is modularized, it is effective for protecting the light emitting diode from rising in temperature.

  According to the sixteenth aspect, it is possible to reduce power loss in the switching element in the transient state in which the first switching element shifts from the off state to the on state.

  According to the seventeenth aspect of the present invention, the light emitting diode driving device can be further miniaturized by employing the light emitting diode driving semiconductor device in which the switching drive circuit is formed on a single substrate.

Hereinafter, a light emitting diode driving device and a light emitting diode driving semiconductor device according to an embodiment of the present invention will be described in detail with reference to the drawings.
(Embodiment 1)
A first embodiment of the present invention will be described with reference to FIGS.

  FIG. 1 shows a light emitting diode driving device and a light emitting diode driving semiconductor device according to the first embodiment. In FIG. 1, a rectifier circuit (full-wave rectifier circuit) 2 is connected to an AC power source 1 that generates an AC voltage, and generates a full-wave rectified voltage from the AC voltage. Hereinafter, a power supply unit composed of the AC power supply 1 and the rectifier circuit 2 will be described as an example. Here, the other end of the primary side coil of the transformer 3 is connected to the anode terminal of the light emitting diode 5, the cathode terminal of the light emitting diode 5 is connected to the anode terminal of the diode 4, and a series connection circuit loop 6 is formed. The high potential side of 2 is connected to the series connection circuit loop 6, and the low potential side is connected to the reference potential terminal SRCE.

  The light emitting diode 5 is a light emitting diode group in which a plurality of light emitting diodes are connected in series. However, the number of connected light-emitting diodes 5 is not limited to that shown in FIG. 1, and one or more light-emitting diodes may be connected. A common connection portion of the cathode terminal of the light emitting diode 5 and the anode terminal of the diode 4 is connected to the high potential side terminal DRN of the first switching element 7. In FIG. 1, the series connection circuit loop is connected in the order of the voltage source → the temporary coil of the transformer → the light emitting diode. However, the present invention is not limited to this. It is clear that the same effect can be obtained even if the connection order of the transformer and the light emitting diode is reversed. The same applies to the embodiments described below.

  The switching drive circuit 50 includes a first switching element 7, a control circuit 8, a constant current source 9, a regulator 10, an input voltage detection circuit 12, a first current detection circuit 20, and a second current detection circuit 24. The five terminals connected to the outside include a rectified voltage application terminal IN, a feedback terminal FB, a high potential side terminal DRN, a reference potential terminal SRCE, and a control power supply voltage terminal VCC.

  The constant current source 9 is connected between the high potential side terminal DRN of the first switching element 7 and the regulator 10 to supply a constant current. The regulator 10 is connected to the control power supply terminal VCC, and supplies the control power supply voltage Vcc to the switching drive circuit. Supply. A capacitor 11 is connected between the control power supply terminal VCC and the reference potential terminal SRCE. The rectified voltage VIN is applied to the input voltage detection circuit 12 via the rectified voltage application terminal IN.

  The input voltage detection circuit 12 includes two resistors 13 and 14 connected in series, and a comparator 15 that connects an intermediate connection point between the resistors 13 and 14 to a plus input terminal. The high potential side of the series connection resistors 13 and 14 is connected to the rectified voltage application terminal IN, and the low potential side is connected to the reference potential terminal SRCE. The input reference voltage VST is input to the negative input terminal of the comparator 15. The output terminal of the comparator 15 is connected to the start / stop circuit 16 in the control circuit 8. The start / stop circuit 16 is connected to the clock generator 17 and the AND circuit 18. The clock generator 17 is connected to one input terminal of the OR circuit 19 and outputs a clock signal when receiving a start signal from the start / stop circuit 16.

  One end of the secondary coil of the transformer 3 is connected to the reference potential terminal SRCE, and the other end is connected to the first current detection circuit 20 via the feedback terminal FB. The first current detection circuit 20 includes an IV conversion circuit 21, a comparator 22, and a NOR circuit 23 connected to the feedback terminal FB. The output signal of the IV conversion circuit is applied to the plus input terminal of the comparator 22, and the detection reference voltage VSB is applied to the minus input terminal. One input terminal of the NOR circuit 23 is connected to the output terminal of the comparator 22, and the other input terminal is connected to the control terminal GATE of the first switching element 7. The output terminal of the NOR circuit 23 is connected to one input terminal of the OR circuit 19.

  In the second current detection circuit 24, the plus input terminal is connected to the high potential side terminal DRN of the first switching element 7, and the detection reference voltage VSN is inputted to the minus input terminal. The output terminal of the second current detection circuit 24 is connected to one input terminal of the AND circuit 25. The output terminal of the on-time blanking pulse generator 26 is connected to the other input terminal of the AND circuit 25.

  The output terminal of the OR circuit 19 is connected to the set signal terminal S of the RS flip-flop circuit 27. The output signal of the AND circuit 25 is input to the reset signal terminal R of the RS flip-flop circuit 27. One input terminal of the AND circuit 18 is connected to the output terminal Q of the RS flip-flop circuit 27, and the output terminal of the AND circuit 18 is an input of the control terminal of the first switching element 7 and the blanking pulse generator 26 when on. The terminal and one input terminal of the NOR circuit 23 are connected.

  The control circuit 8 receives signals from the first current detection circuit 20, the second current detection circuit 24, and the input voltage detection circuit 12, and performs on / off control of the first switching element 7.

  The operation of the light emitting diode driving device configured as described above will be described below with reference to FIG.

  FIG. 2 is a diagram showing the waveform of the voltage VIN output from the rectifier circuit 2, the waveform of the current ILED flowing through the light-emitting diode 5, and the waveform of the control power supply voltage Vcc in the light-emitting diode driving device according to the first embodiment. . The horizontal axis in FIG.

  The voltage VIN output from the rectifier circuit 2 has a waveform obtained by full-wave rectifying the AC voltage as shown in FIG. The full-wave rectified voltage VIN is supplied to the capacitor 11 via the primary coil of the transformer 3, the light emitting diode 5, the constant current source 9, and the regulator 10. As a result, the voltage across the capacitor 11 increases. The control power supply voltage Vcc of the switching drive circuit 50 is controlled to be a constant voltage by the regulator 10, and the on / off control of the first switching element 7 by the control circuit 8 becomes possible. When the reference voltage Vcc of the control power supply terminal VCC is lower than Vcc0, the first switching element 7 is in a non-switchable state. It is necessary to select so that it does not fall below.

  Further, the full-wave rectified voltage VIN is applied to one end of the resistor 13 of the input voltage detection circuit 12 through the rectified voltage application terminal IN, and is divided by the resistors 13 and 14. The divided voltage VIN14 is applied to the plus input terminal of the comparator 15. The reference voltage VST is applied to the negative input terminal of the comparator 15, and when the voltage VIN 14 divided by the resistors 13 and 14 reaches the reference voltage VST, the comparator 15 sends a high (H) signal to the start / stop circuit 16. Send. The start / stop circuit 16 outputs a start signal, and intermittent on / off control of the first switching element 7 by the control circuit 8 is started.

  When the voltage VIN14 divided by the resistors 13 and 14 falls below the reference voltage VST, the comparator 15 sends a low (L) signal to the start / stop circuit 16. The start / stop circuit 16 outputs a stop signal, and the control circuit 8 stops the control of the first switching element 7. That is, the first switching element 7 is kept off.

  That is, intermittent ON / OFF control of the first switching element 7 is performed during the period T1 when the voltage VIN14 is equal to or higher than the reference voltage VST, and the constant current ILED flows through the light emitting diode 5. During the period T <b> 2 when the voltage VIN <b> 14 is equal to or lower than the reference voltage VST, the first switching element 7 remains off and no current flows through the light emitting diode 5.

  Next, the constant current output operation in the light emitting diode driving apparatus according to the first embodiment will be described with reference to FIGS. 1 and 3.

  FIG. 3 is an operation waveform diagram in a part of the period T1 in FIG. Although the input voltage VIN varies with time, the VINA and VINB periods (T1A, T1B) that can be regarded as substantially constant voltages will now be described.

  In FIG. 3, VIN is the input voltage VIN waveform, VD is the high potential terminal DRN waveform of the first switching element 7, ID is the current waveform flowing through the first switching element 7, and IFB is the secondary of the transformer 3. A current waveform flowing through the side coil, and ILED indicates a current waveform flowing through the light emitting diode 5. The horizontal axis represents time T.

  First, an operation in the period T1A is described.

  Immediately after the start, the start / stop circuit 16 outputs a start signal, so that the first switching element 7 is switched from OFF to ON. An on-time blanking pulse generator 26 is connected to the control terminal GATE of the first switching element 7. The on-time blanking pulse generator 26 receives the output signal of the control circuit 8 and outputs a low (L) signal for a certain time (for example, several hundred nsec) after the first switching element 7 is switched from OFF to ON. Otherwise, a high (H) signal is output.

  This occurs when the output signal of the blanking pulse generator 26 at the time of ON and the output signal of the second current detection circuit 24 are input to the AND circuit 25 so that the first switching element 7 is turned from the OFF state to the ON state. This prevents malfunction of on / off control of the first switching element 7 due to ringing.

  The second current detection circuit 24 compares the ON voltage of the first switching element 7 with the detection reference voltage VSN of the second current detection circuit 24, and the element current ID flowing through the first switching element 7 is a predetermined value. It is detected whether or not the peak value IP has been reached.

  In FIG. 1, when the ON voltage of the first switching element 7 reaches the voltage value VSN, the second current detection circuit 24 outputs a high (H) level signal. The high (H) level signal is input to the reset signal terminal R of the RS flip-flop circuit 27 via the AND circuit 25. The RS flip-flop circuit 27 is reset and outputs a low (L) level signal to the AND circuit 18. When the AND circuit 18 outputs a low (L) level signal, the first switching element 7 is switched from on to off.

  That is, the ON time TONA of the first switching element 7 is defined by a period from when the first switching element 7 is switched from OFF to ON until a high (H) level signal is output from the second current detection circuit 24. Is done.

  Here, the current ILED that flows through the light emitting diode 5 when the first switching element 7 is in the ON state is ILED = ID, and the primary coil of the transformer 3 → the light emitting diode 5 → the direction of the first switching element 7. And increases with time T to the peak current IP. On the other hand, the current ILED flowing through the light emitting diode 5 when the first switching element 7 is in the off state flows through the closed loop of the primary coil of the transformer 3 → the light emitting diode 5 → the diode 4 → the primary coil of the transformer 3 and gradually. It will decrease to. The current waveform flowing through the primary side coil of the transformer 3 is the same as the current waveform flowing through the light emitting diode 5, and this current also flows through the secondary side coil of the transformer 3.

  The first current detection circuit 20 converts the current IFB flowing through the secondary side coil of the transformer 3 into a voltage, and compares it with the input reference voltage VSB of the first current detection circuit 20 to compare the secondary side coil of the transformer 3. It is detected whether or not the current IFB flowing through the current reaches a predetermined bottom value IB. The current IFB flowing through the secondary coil of the transformer 3 is converted into a voltage signal by the IV conversion circuit 21 in the first current detection circuit 20 and compared with the input reference voltage VSB of the comparator 22. When the output voltage signal of the IV conversion circuit 21 becomes equal to or lower than the input reference voltage VSB, the comparator 22 outputs a low (L) level signal to one input terminal of the NOR circuit 23.

  When the low (L) level signal is input to the other input terminal of the NOR circuit 23, that is, only when the first switching element 7 is in the OFF state, the NOR circuit 23 is a high (H) level signal. And a high (H) level signal is input to the set signal terminal S of the RS flip-flop circuit 27 via the OR circuit 19. When set, the RS flip-flop circuit 27 outputs a high (H) level signal to the AND circuit 18. When the AND circuit 18 outputs a high (H) level signal, the first switching element 7 is switched from OFF to ON. That is, the OFF time TOFF of the switching element is defined by a period from when the first switching element 7 is switched from ON to OFF until the first current detection circuit 24 outputs a high (H) level signal.

  As described above, the on / off control of the first switching element 7 by the control circuit 8 is performed during the period T1 in FIG. 2, and the current ID flowing through the first switching element 7 is as shown in FIG. . When the first switching element 7 is in the OFF state, the current that flows through the primary coil of the transformer 3 (that is, the current that flows through the light emitting diode 5) flows such that IFB = ILED = IB is the bottom current. That is, the peak current value IP of the current flowing through the light emitting diode is detected by the second current detection circuit 24, the bottom current value IB is detected by the first current detection circuit 20, and the ON time TONA of the first switching element 7 is detected. And the OFF time TOFF is controlled.

The current ILED flowing through the light-emitting diode 5 is a pulsating current having a peak at IP and a bottom at IB in FIG. 3, and the average current can be expressed by the following equation (1).

ILED = (IP−IB) / 2 Formula (1)

Further, the on-time TONA and the off-time TOFF of the first switching element 7 can be expressed by Expression (2) and Expression (3) when the winding resistance of the transformer 3 and the on-resistance of the first switching element 7 are ignored.

TONA≈L × (IP-IB) / (VINA-VO) (2)

TOFF≈L × (IP−IB) / (VO + VF) (3)

Here, L is the inductance value of the primary coil of the transformer 3, VO is the total value of the forward voltage of the light emitting diode 5, and VF is the forward voltage of the diode 4.

  Next, a difference between the on-time and the off-time of the first switching element 7 in the period T1A will be described with respect to the on-time and the off-time of the first switching element 7 in the period T1B.

Since the input voltage VINB in the period T1B is lower than the input voltage VINA in the period T1A, the ON time TONB of the first switching element 7 in the period T1B can be expressed by Expression (4) and longer than TONA in Expression (2). Become.

TONB≈L × (IP−IB) / (VINB−VO)> TONA (formula 4)

On the other hand, since the off time of the first switching element 7 does not depend on the input voltage VIN, it can be expressed by Expression (3) as in the period T1A.

  As described above, although the on-time of the first switching element 7 varies depending on the fluctuation of the input voltage, the peak current IP and the bottom current IB flowing through the light emitting diode 5 are always controlled to be constant without depending on the fluctuation of the input voltage. 5, a pulsating current having a constant current ripple width Iripple = (IP−IB) flows, and the average current can always be expressed by the equation (1).

  When the light emitting diode driving device and the light emitting diode driving semiconductor device as described above are used, the following effects are obtained.

  Since the light emitting diode driving apparatus according to the first embodiment does not require a resistor for power supply, there is no power loss during startup. In general, power is supplied to the light emitting diode driving device from an input voltage (high voltage) in a direct manner via a resistor. This power supply is performed not only during start / stop but also during normal operation, so that power loss occurs in the resistor. However, according to the configuration of the present embodiment, such a resistor is not necessary.

  Since the current ID flowing through the first switching element 7 detects the on-voltage of the first switching element 7 by the second current detection circuit 24, a conventional detection resistor for current detection becomes unnecessary, and the detection resistor Power loss due to is not generated.

  Furthermore, even if the input voltage varies, the average current flowing through the light-emitting diode can always be controlled to be constant, so a smoothing capacitor is required when driven by a voltage rectified by a rectifier circuit using a commercial power supply for the power supply unit. do not do. Even if the voltage value varies greatly depending on the region, such as AC100V / AC200V, it is not necessary to change the oscillation frequency of the oscillator or the inductance value of the coil each time.

  Furthermore, since the input voltage detection circuit is provided, when a commercial power supply is used as the AC power supply, the period during which the operation can be performed during the double period (100 Hz / 120 Hz) can be accurately controlled, so that stable operation is possible. Since a smoothing capacitor is not required, the noise terminal level can be kept low without requiring a special circuit.

  1 may be integrated on a single semiconductor substrate. In that case, the control power supply voltage terminal VCC, the high potential side terminal DRN of the first switching element 7, the low potential At least five terminals of the side terminal SRCE, the rectified voltage application terminal IN, and the feedback terminal FB are integrated as external connection terminals. By incorporating it into a package having five or more terminals, the number of parts can be greatly reduced, the dimensions of the parts can be reduced, and a more compact and low-priced drive device can be realized. The same applies to the embodiments described below.

  Further, in FIG. 1, the full-wave rectifier circuit 2 is used as means for rectifying the AC voltage, but it is obvious that the same effect can be obtained even if a half-wave rectifier circuit is used. The same applies to the embodiments described below.

  Although omitted in FIG. 1, a clamp circuit such as a Zener diode connected in parallel between the high potential side and the low potential side of the first switching element 7 may be connected. In the intermittent on / off control of the first switching element 7 by the control circuit 8, when the first switching element 7 shifts from the on state to the off state, the high potential side voltage VD of the switching element 7 is The ringing caused by the capacitance or wiring inductance may result in a voltage exceeding the withstand voltage of the first switching element 7, which may lead to the destruction of the first switching element 7. In such a case, By connecting a clamp circuit having a clamp voltage lower than the breakdown voltage of the switching element 7, the voltage VD of the high potential side terminal DRN of the first switching element 7 is clamped by this clamp voltage, and the first switching element 7 It becomes possible to prevent destruction. Thereby, it is possible to realize a light-emitting diode driving device with higher safety.

  Similarly in the following embodiments, the same effect can be obtained by adding a clamp circuit.

Note that, in the transient state where the first switching element 7 transitions from the off state to the on state, if the reverse recovery time (Trr) of the diode 4 is slow, the power loss increases, and thus the reverse of the diode 4 of the first embodiment. The recovery time (Trr) is 100 nsec or less.
(Embodiment 2)
A second embodiment of the present invention will be described with reference to FIG.

  FIG. 4 shows a light emitting diode driving device and a light emitting diode driving semiconductor device according to the second embodiment. In the LED driving apparatus of the second embodiment shown in FIG. 4, the transformer 3 of the first embodiment shown in FIG. 1 is replaced with a choke coil 28, and the configuration of the first current detection circuit 20 is shown in FIG. Unlike the first embodiment, other configurations and basic operations are the same, so members corresponding to the members described in the first embodiment are denoted by the same reference numerals and description thereof is omitted here. The same applies to the embodiments described below.

  In FIG. 4, the high potential side of the rectifier circuit 2 is connected to the anode terminal of the light emitting diode 5 and the cathode terminal of the diode 4, and the low potential side of the rectifier circuit 2 is connected to the reference potential terminal SRCE. The cathode terminal of the light emitting diode 5 is connected to one end of the choke coil 28, and the other end of the choke coil 28 is connected to the anode terminal of the diode 4 to form a series connection circuit loop 6. A common connection between the choke coil 28 and the anode terminal of the diode 4 is connected to the high potential side terminal DRN of the first switching element 7. In FIG. 4, the series connection circuit loop is connected in the order of voltage source → light emitting diode → coil, but is not limited thereto. It is clear that the same effect can be obtained even if the connection order of the coil and the light emitting diode is reversed. The same applies to the embodiments described below.

  In FIG. 1, the feedback terminal FB to which the secondary coil of the transformer 3 and the first current detection circuit 20 are connected is eliminated, and the first current detection circuit 20 is connected to the first switching element 7 as shown in FIG. Connected to the high potential side terminal DRN.

  The first current detection circuit 20 includes two resistors 29 and 30 connected in series, a comparator 22 in which an intermediate connection point between the resistors 29 and 30 is connected to a positive input terminal, and a NOR circuit 23. The The high potential side of the series connection resistors 29 and 30 is connected to the high potential side terminal DRN of the first switching element 7, and the low potential side is connected to the reference potential terminal SRCE. The detection reference voltage VSB is input to the negative input terminal of the comparator 22. One input terminal of the NOR circuit 23 is connected to the output terminal of the comparator 22, and the other input terminal is connected to the control terminal GATE of the first switching element 7. The output terminal of the NOR circuit 23 is connected to one input terminal of the OR circuit 19.

  When the first switching element 7 is in the on state, the high potential side potential of the first switching element 7 is the on voltage. At this time, since the detection reference voltage VSB is set higher than the voltage divided by the resistors 29 and 30, the comparator 22 outputs a low (L) level signal.

  When the first switching element 7 is switched from the on state to the off state, a potential difference of VO + VF is generated across the choke coil 28 due to the counter electromotive force. At this time, a voltage of at least VIN + VF is applied to the high potential side terminal of the first switching element 7, and the voltage divided by the resistors 29 and 30 becomes higher than the detection reference voltage VSB, so that the comparator 22 A high (H) level signal is output.

  When the first switching element 7 is in the OFF state, the current flowing in the closed loop of the diode 4, the light emitting diode 5, and the choke coil 28 is the same as that described in the first embodiment. And is gradually reduced. When the current flowing through the series connection circuit loop 6 decreases, the voltage divided by the resistors 29 and 30 also decreases in a similar manner, and becomes lower than the detection reference voltage VSB at a certain time, and the comparator 22 is low ( An L) level signal is output to one input terminal of the NOR circuit 23. In this case, since the first switching element 7 is in an OFF state, a low (L) level signal is also input to the other input terminal of the NOR circuit 23, and therefore the NOR circuit 23 is at a high (H) level. A signal is output, and a high (H) level signal is input to the set signal terminal S of the RS flip-flop circuit 27 via the OR circuit 19.

  With the configuration as described above, the bottom current IB of the current ILED flowing through the light emitting diode 5 can be detected, so that the same effect as in the first embodiment can be expected. Furthermore, since a transformer is not used, a light-emitting diode driving device that is smaller and less expensive than that of the first embodiment can be realized.

  4 is integrated on a single semiconductor substrate. At that time, the control power supply voltage terminal VCC, the high potential side terminal DRN of the first switching element 7, and the low potential side terminal are integrated. At least four terminals of SRCE and rectified voltage application terminal IN may be integrated as external connection terminals, and by incorporating them in a package having four or more terminals, the number of parts can be greatly reduced, and the dimensions of the parts Accordingly, a light-emitting diode driving device with a smaller size and lower cost can be realized.

Further, in the second embodiment, when the first switching element 7 is in the OFF state, the current flowing through the series connection circuit loop 6 is detected using the high-potential side terminal DRN of the first switching element 7 and the reference Although the voltage divided by the two resistors 29 and 30 connected in series between the potential terminals SRCE is used, the present invention is not limited to this. For example, a decrease amount of the both-terminal potential difference VO + VF of the choke coil 28 may be detected, or a current value flowing through the series connection circuit loop may be monitored using a current sensor or the like.
(Embodiment 3)
A third embodiment of the present invention will be described with reference to FIG.

  FIG. 5 is a diagram showing a light emitting diode driving device and a light emitting diode driving semiconductor device according to the third embodiment. The light-emitting diode driving device according to the third embodiment shown in FIG. 5 has a connection of the constant current source 9, a second switching element 31 connected in parallel with the first switching element 7, and a resistor 32. However, unlike the first embodiment shown in FIG. 1, the other configurations are the same. The constant current source 9 is connected to the rectified voltage application terminal IN.

  For example, when the constant current source 9 is connected as shown in FIG. 1 of the first embodiment, the operation to the switching drive circuit at that time is also performed while the operation of the first switching element 7 is stopped (during the off state). Is supplied from the full-wave rectified voltage VIN → the primary coil of the transformer 3 → the light emitting diode 5 → the high potential side terminal DRN → the constant current source 9 → the regulator 10 → the control power supply voltage terminal VCC. 5 emits weak light.

  On the other hand, in the light emitting diode driving apparatus according to the third embodiment, the power supply to the switching drive circuit while the operation of the first switching element 7 is stopped (during the off state) is full-wave rectification. The path is as follows: voltage VIN → rectified voltage application terminal IN → constant current source 9 → regulator 10 → control power supply voltage terminal VCC. For this reason, while the on / off control of the first switching element 7 is stopped, the light emitting diode 5 has an effect that it does not emit weak light.

  Furthermore, in the third embodiment, the second switching element 31 (N-type MOSFET) in which a current having a constant current ratio smaller than the current flowing through the first switching element 7 flows in parallel with the first switching element 7. ). The high potential side of the second switching element 31 is connected to the high potential side of the first switching element 7, the control terminal is connected to the control terminal GATE of the first switching element 7, and the control circuit 8 performs the same control. A signal is input. The low potential side of the second switching element 31 is connected to one end of the resistor 32, and the other end of the resistor 32 is connected to the reference potential terminal SRCE.

  The second current detection circuit 24 of the third embodiment detects the current flowing through the second switching element 31 with the voltage across the resistor 32 and compares it with the detection reference voltage VSN.

  For example, in the method of detecting the current ID using the ON voltage of the first switching element 7 as in the first embodiment, the current ID is changed from the OFF state to the ON state. Since the current fluctuates for a certain period of time (generally several hundred nsec), the current ID cannot be accurately detected.

On the other hand, when the voltage determined by the resistor 32 (current that has flowed × resistance value of the resistor 32) is compared with the detection reference voltage VSN as in the third embodiment, the first switching element 7 changes from the off state to the on state. Even immediately after the transition, the current ID can be accurately detected. Further, since the large current is not directly detected by the resistor 32, the current of the first switching element 7 with reduced power loss can be detected.
(Embodiment 4)
Embodiment 4 of the present invention will be described with reference to FIG.

  FIG. 6 is a diagram showing a light emitting diode driving device and a light emitting diode driving semiconductor device according to the fourth embodiment. As shown in FIG. 6, the light emitting diode driving apparatus according to the fourth embodiment is different from the third embodiment in the current detection value variable circuit 33 for varying the detection reference voltage VSB of the first current detection circuit 20. The difference is that an external terminal SB to which the current detection value variable circuit 33 is connected is provided. Other configurations are the same.

  In the light emitting diode driving device of the fourth embodiment, the current detection value variable circuit 33 that generates the detection reference voltage VSB is connected to the negative input terminal of the comparator 22 in the first current detection circuit 20. The current detection value variable circuit 33 is connected to the external terminal SB of the switching drive circuit 50, and the detection reference voltage VSB has a variable voltage value according to a control signal input to the external terminal SB.

In the fourth embodiment, the detection reference voltage VSB of the first current detection circuit 20 can be changed by changing the signal level input to the external terminal SB, and the bottom value IB of the current ILED flowing through the light emitting diode 5 is adjusted. It is possible. Although not shown, the ripple width Iripple of the pulsating current can be changed by adjusting the bottom value IB of the current ILED flowing through the light emitting diode 5.
(Embodiment 5)
A fifth embodiment of the present invention will be described with reference to FIGS.

  FIG. 7 is a diagram showing a light emitting diode driving device and a light emitting diode driving semiconductor device according to the fifth embodiment. As shown in FIG. 7, the LED driving apparatus of the fifth embodiment is different from the third embodiment in the detection reference voltage VSB of the first current detection circuit 20 and the detection reference voltage of the second current detection circuit 24. The difference is that a current detection value variable circuit 34 for changing VSN and an external terminal CL to which the current detection value variable circuit 34 is connected are provided. Other configurations are the same.

  In the above configuration, the current detection value variable circuit 34 changes the detection reference voltage VSB and the detection reference voltage VSN in accordance with the control signal input to the external terminal CL, and the comparator 22 in the first current detection circuit 20 respectively. Are input to the negative input terminal and the negative input terminal of the second current detection circuit 24.

  The operation of the light emitting diode driving apparatus according to the fifth embodiment will be described with reference to FIG.

  For example, as shown in FIG. 8, when the signal level VS input to the external terminal CL is changed in three stages and the detection reference voltage VSN and the detection reference voltage VSB are gradually reduced in three stages, the current detection of the drain current ID is performed. Since the bottom value IB of the current IFB flowing in the primary side coil of the level IDP and the transformer 3 also gradually decreases in three steps, the current ILED flowing in the light emitting diode 5 has a constant ripple width Iripple and an average current gradually in three steps. Will begin to decline.

  As described above, the average current of the light-emitting diode 5 changes according to the signal input to the external terminal CL.

  Although the fifth embodiment has been described on the assumption that the average current of the light emitting diode 5 changes in proportion to the fluctuation of the signal level VS input to the external terminal CL, the signal input to the external terminal CL You may operate | move so that the average current of the light emitting diode 5 may change in inverse proportion with respect to a fluctuation | variation. Further, the signal level VS input to the external terminal CL may be defined by either voltage or current, and the same applies to the following embodiments.

  In addition, the case where the signal VS input to the external terminal CL fluctuates digitally in three stages has been described. However, when a linearly changing signal is input, the detection reference voltage VSN fluctuates linearly. The average current of the light emitting diode 5 can also be varied linearly.

When the light emitting diode driving device as described above is used, in addition to the effects shown in the third embodiment, the peak value IP of the current ILED flowing from the outside to the light emitting diode 5 can be adjusted. There is an effect that it becomes easy.
(Embodiment 6)
Embodiment 6 of the present invention will be described with reference to FIG.

  FIG. 9 is a diagram showing a light emitting diode driving device and a light emitting diode driving semiconductor device according to the sixth embodiment. The light emitting diode driving apparatus according to the sixth embodiment shown in FIG. 9 is different from the fifth embodiment shown in FIG. 7 in the configuration of the input voltage detection circuit 12.

  That is, as shown in FIG. 9, the input voltage detection circuit 12 includes three resistors 35, 36, and 37 connected in series between the rectified voltage application terminal IN and the reference potential terminal SRCE, and the resistors 35 and 36. A connection point of the first comparator 38, the resistor 36 and the resistor 37, which inputs the first divided voltage VL of the input voltage VIN output from the connection point to the plus input terminal and inputs the reference voltage VST to the minus input terminal. The second divided voltage VH of the input voltage VIN output from the second comparator 39 is input to the negative input terminal, the reference voltage VST is input to the positive input terminal, the second comparator 39, the output terminal of the first comparator 38 and the second And an AND circuit 40 in which each input terminal is connected to the output terminal of the second comparator 39.

  The output terminal of the AND circuit 40 is connected to the start / stop circuit 16. Here, the voltages VL and VH obtained by dividing the input voltage VIN by the three resistors 35, 36, and 37 always have a relationship of VH <VL.

  Next, the operation of the light emitting diode driving device will be described with reference to FIGS.

  FIG. 10 is a diagram showing waveforms of the current ILED flowing through the light-emitting diode block 5, the first divided voltage VL, and the second divided voltage VH, and the horizontal axis is time T. FIG. As shown in FIG. 10, until the first divided voltage VL reaches the reference voltage VST, the comparator 38 outputs a signal whose signal level is low. On the other hand, since the second divided voltage VH is lower than the first divided voltage VL, the comparator 39 outputs a signal whose signal level is high. Therefore, until the first divided voltage VL reaches the reference voltage VST, the output signal of the AND circuit 40 to which the output signals of the two comparators 38 and 39 are input becomes the low (L) level, and the start / stop circuit 16 Outputs a stop signal, and the switching elements 7 and 31 are in an oscillation stop state (period T2A).

  Next, when the input voltage VIN rises and the first divided voltage VL reaches the reference voltage VST, the comparator 38 outputs a signal whose signal level is high (H) level. On the other hand, since the second divided voltage VH is lower than the first divided voltage VL, the comparator 39 also outputs a signal having a high signal level. Therefore, when the first divided voltage VL reaches the reference voltage VST, the output signal of the AND circuit 40 to which the output signals of the two comparators 38 and 39 are input becomes high level, and the start / stop circuit 16 outputs the start signal. The switching elements 7 and 31 are oscillated (period T1).

  Further, when the input voltage VIN rises and the second divided voltage VH reaches the reference voltage VST, the comparator 39 outputs a signal whose signal level is low. On the other hand, since the first divided voltage VL is higher than the second divided voltage VH, the comparator 38 continues to output a signal whose signal level is high. Therefore, when the second divided voltage VH reaches the reference voltage VST, the output signal of the AND circuit 40 to which the output signals of the two comparators 38 and 39 are input becomes low level, and the start / stop circuit 16 outputs a stop signal. Then, the switching elements 7 and 31 are in an oscillation stop state (period T2B).

  Thereafter, when the input voltage VIN decreases, the second divided voltage VH again falls below the reference voltage VST, and the switching elements 7 and 31 enter an oscillation state (period T1). When the first divided voltage VL falls below the reference voltage VST, the switching elements 7 and 31 are in an oscillation stop state (period T2A).

  That is, as shown in FIG. 10, during the period when the voltage VL obtained by dividing the input voltage VIN is smaller than the reference voltage VST, the on / off control of the first switching element 7 is stopped and the off state is maintained. The light emitting diode is quenched. On the other hand, during the period in which the voltage VL obtained by dividing the input voltage VIN is higher than the reference voltage VST and the voltage VH obtained by dividing the input voltage VIN is lower than the reference voltage VST, the first switching element 7 by the control circuit 8 is used. Can be turned on / off, and the light emitting diode can be turned on.

  Further, during a period in which the voltage VH obtained by dividing the input voltage VIN is higher than the reference voltage VST, the on / off control of the first switching element 7 is stopped and the off state is maintained, so that the light emitting diode is extinguished.

  With the configuration as described above, the upper limit value and the lower limit value of the voltage level at which the on / off control of the first switching element 7 can be controlled with respect to the change of the input voltage VIN can be set. It becomes a protection circuit when a voltage is applied, and a safer LED driving device can be realized.

In the sixth embodiment, two divided voltages are generated using the three resistors 35, 36, and 37 connected in series. However, the present invention is not limited to this. What is necessary is just to be a structure which can prescribe | regulate the upper limit and lower limit of the voltage level which can perform ON / OFF control of the switching element 7 of this.
(Embodiment 7)
A seventh embodiment of the present invention will be described with reference to FIG.

  FIG. 11 shows a light emitting diode driving device and a light emitting diode driving semiconductor device according to the seventh embodiment. However, members corresponding to those described in the first to sixth embodiments are denoted by the same reference numerals, and description thereof is omitted here. The light emitting diode driving device according to the seventh embodiment has a configuration in which an overheat protection circuit 41 is additionally connected to the input terminal of the AND circuit 18 with respect to the sixth embodiment.

  By adding the overheat protection circuit 41 as in the above configuration, the device temperature when the first switching element 7 generates heat due to loss can be detected. In particular, in a semiconductor device in which the switching drive circuit 50 is formed on a single substrate, the device temperature can be detected with high accuracy.

  The overheat protection circuit 41 outputs a signal for forcibly turning off the first switching element 7 to the AND circuit 18 when the temperature of the first switching element 7 abnormally increases. The temperature of the first switching element 7 is lowered by stopping the switching operation. As a method of releasing the first switching element 7 from the OFF state, a latch mode in which the DC voltage power supply to the light emitting diode driving device is temporarily stopped and this OFF state is maintained until the power supply is started again, and overheat protection is performed. There are two types of self-recovery modes in which the first switching element 7 is held in the off state until the temperature becomes equal to or lower than the temperature specified by the circuit 41, and the off state is automatically canceled when the temperature becomes lower than the specified temperature.

By adopting the configuration as described above, it is possible to avoid the thermal destruction of the first switching element 7 due to an abnormal temperature rise, so that safety and reliability can be further improved.
Furthermore, when the light emitting diode driving device is modularized, it is effective for protecting the light emitting diode from rising in temperature.
(Embodiment 8)
Embodiment 8 of the present invention will be described with reference to FIG.

  FIG. 12 shows a light emitting diode driving device and a light emitting diode driving semiconductor device according to the eighth embodiment. The light emitting diode driving device according to the eighth embodiment has a configuration in which a dimming control circuit 42 is additionally connected to the external terminal CL with respect to the seventh embodiment.

  For example, when an 8-bit microcomputer is used as the dimming control circuit 42, 256-level dimming can be performed according to an external signal. Although not shown, a fixed resistor and a variable resistor are connected in series between the control power supply voltage terminal VCC and the reference potential terminal SRCE, and a voltage divided by the two resistors is input to the external terminal CL, whereby a variable resistance value is obtained. By changing the, stepless dimming is possible.

  With the above configuration, the average current value of the current ILED flowing through the light emitting diode 5 can be adjusted from the outside, and a light emitting diode driving device having a dimming function can be realized with a simple configuration.

  The light emitting diode driving device and the light emitting diode driving semiconductor device of the present invention can easily control the peak current value and the ripple width of the pulsating current flowing in the LED with a simple configuration, and the constant current driving can be performed by the average current. It is possible and can suppress power loss to a low level, and can be used for all apparatuses and devices using light emitting diodes, and is particularly useful as an LED lighting device.

1 is a circuit diagram of a light-emitting diode driving apparatus according to Embodiment 1 of the present invention. Signal waveform diagram of each part in the light emitting diode driving apparatus of the first embodiment Waveform diagram of T1 period in the light emitting diode driving apparatus of the first embodiment Circuit diagram of light-emitting diode driving apparatus according to Embodiment 2 of the present invention Circuit diagram of light-emitting diode driving apparatus according to Embodiment 3 of the present invention Circuit diagram of light-emitting diode driving apparatus according to Embodiment 4 of the present invention Circuit diagram of light emitting diode driving apparatus according to Embodiment 5 of the present invention Signal waveform diagram of each part in the light emitting diode driving apparatus of Embodiment 5 Circuit diagram of light-emitting diode driving apparatus according to Embodiment 6 of the present invention Signal waveform diagram of each part in the light emitting diode driving apparatus of the sixth embodiment Circuit diagram of light-emitting diode driving apparatus according to Embodiment 7 of the present invention Circuit diagram of light-emitting diode driving apparatus according to Embodiment 8 of the present invention Circuit diagram of light emitting diode driving device of first example in conventional example Circuit diagram of light emitting diode driving apparatus of second example in conventional example

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 AC power supply 2 Rectifier circuit 3 Transformer 4 Diode 5 Light emitting diode 6 Series connection circuit loop 7, 31 Switching element 8 Control circuit 9 Constant current source 10 Regulator 11 Capacitor 12 Input voltage detection circuit 13, 14, 29, 30, 32, 35 , 36, 37 Resistor 15, 22, 38, 39 Comparator 16 Start / stop circuit 17 Clock generator 18, 25, 40 AND circuit 19 OR circuit 20, 24 Current detection circuit 21 IV conversion circuit 23 NOR circuit 26 When ON Blanking pulse generator 27 RS flip-flop circuit 28 Choke coil 33, 34 Current detection value variable circuit 41 Overheat protection circuit 42 Dimming control circuit 50 Switching drive circuit

Claims (17)

A light emitting diode block having one or a plurality of light emitting diodes, a primary coil of a transformer connected in series to the light emitting diode block, and a back electromotive force generated in the primary coil of the transformer is supplied to the light emitting diode block A series connection circuit loop composed of diodes for
A power source connected to one terminal of the series connection circuit loop, for applying a voltage to the transformer and the light emitting diode block;
A light emitting diode driving device including a switching driving circuit connected to the other terminal of the series connection circuit loop and intermittently supplying a current to the light emitting diode block;
The switching drive circuit is
A first switching element having one end connected to the series connection circuit loop and the other end connected to a reference potential of the power supply unit;
One end is connected to the other end of the secondary coil of the transformer connected to the reference potential of the power supply unit, and when the current flowing through the secondary coil of the transformer is less than a preset value, a bottom value detection signal is output. A first current detection circuit for outputting;
A second current detection circuit that outputs a peak value detection signal when a current flowing through the first switching element is equal to or greater than a preset value;
The first switching element is connected to the high potential side terminal, the control terminal, and the low potential side terminal, receives the bottom value detection signal from the first current detection circuit, turns on the first switching element, A control circuit for receiving a peak value detection signal from a second current detection circuit and outputting a control signal for turning off the first switching element to a control terminal of the first switching element;
A constant current source connected to one end of the series connection circuit loop;
A regulator connected to the other end of the constant current source and generating an operating voltage of the switching drive circuit;
A light emitting diode driving device comprising a capacitor having one end connected to the regulator and a control circuit and the other end connected to a reference potential of the power supply unit. The first current detection circuit includes:
An IV conversion circuit that converts a current flowing in the secondary coil of the transformer into a voltage;
A first comparator in which an output signal of the IV conversion circuit is input to a positive input terminal and a first reference voltage is input to a negative input terminal;
2. The light emitting diode drive according to claim 1, further comprising a NOR circuit in which an output of the first comparator is input to one input terminal and a control signal of the control circuit is input to the other input terminal. apparatus. A light emitting diode block having one or a plurality of light emitting diodes, a choke coil connected in series to the light emitting diode block, and a diode for supplying back electromotive force generated in the choke coil to the light emitting diode block; A series connection circuit loop configured; and
A power supply unit connected to the series connection circuit loop, for applying a voltage to the light emitting diode block and the choke coil;
A light emitting diode driving device including a switching drive circuit connected to the series connection circuit loop and configured to perform constant current control of a current flowing through the light emitting diode block;
The switching drive circuit is
A first switching element having one end connected to the series connection circuit loop and the other end connected to a reference potential of the power supply unit;
A first current detection circuit that is connected to a high potential side of the first switching element and outputs a bottom value detection signal when a current flowing through the series connection circuit loop is equal to or lower than a preset value;
A second current detection circuit that outputs a peak value detection signal when a current flowing through the first switching element is equal to or greater than a preset value;
The first switching element is connected to the high potential side terminal, the control terminal, and the low potential side terminal, receives the bottom value detection signal from the first current detection circuit, turns on the first switching element, A control circuit for receiving a peak value detection signal from a second current detection circuit and outputting a control signal for turning off the first switching element to a control terminal of the first switching element;
A constant current source connected to one end of the series connection circuit loop;
A regulator connected to the other end of the constant current source and generating an operating voltage of the switching drive circuit;
A light emitting diode driving device comprising a capacitor having one end connected to the regulator and a control circuit and the other end connected to a reference potential of the power supply unit. The first current detection circuit includes:
Two resistors connected in series between a high potential side of the first switching element and a reference potential of the power supply unit;
A first comparator in which a DC voltage divided by the two resistors is input to a positive input terminal, and a first reference voltage is input to a negative input terminal;
4. The light emitting diode drive according to claim 3, further comprising: a NOR circuit in which an output of the first comparator is input to one input terminal and a control signal of the control circuit is input to the other input terminal. apparatus. The power supply unit is
AC power source for generating AC voltage,
A rectifier circuit that rectifies and outputs an AC voltage of the AC power source,
The switching drive circuit is
An input voltage detection circuit that outputs a signal whose potential state changes depending on whether the output voltage of the rectifier circuit is equal to or higher than a predetermined value;
The control circuit includes:
When the output signal of the input voltage detection circuit indicates that the output voltage of the rectifier circuit has exceeded a predetermined value, the on / off control of the first switching element is activated, and the output signal of the input voltage detection circuit 2. A start / stop circuit that outputs a signal for stopping on / off control of the first switching element when the output voltage of the rectifier circuit is lower than a predetermined value. The light-emitting diode driving device according to claim 4. The constant current source is:
6. The light emitting diode driving device according to claim 1, wherein the light emitting diode driving device is connected between a high potential side terminal of the first switching element and the regulator. The constant current source is:
6. The light emitting diode driving device according to claim 1, wherein the light emitting diode driving device is connected between an output side of the power supply unit and the regulator. The second current detection circuit includes:
The ON voltage of the first switching element is compared with a second reference voltage to detect whether or not the current flowing through the first switching element has reached a preset value. The light-emitting-diode drive device in any one of Claim 1-7. The switching drive circuit is
A high-potential side terminal is connected in parallel with the high-potential side terminal of the first switching element, a control signal common to the first switching element is input from the control circuit to the control terminal, and the first switching element is input to the first switching element. A second switching element in which a current having a small current value and a constant current ratio flows with respect to the flowing current;
A resistor connected between the low potential side terminal of the second switching element and the low potential side terminal of the first switching element;
The second current detection circuit includes:
The voltage across the resistor is compared with a second reference voltage to detect whether or not the current flowing through the first switching element has reached a preset value. 8. The light-emitting diode driving device according to any one of 7 above. The switching drive circuit is
A current detection value variable circuit for changing a current detection value of the first current detection circuit by changing a first reference voltage of the first current detection circuit from the outside;
The current detection value variable circuit is:
10. The ripple width of the pulsating current flowing in the light emitting diode is changed by changing a current detection value of the first current detection circuit by an external control signal. A light emitting diode driving device according to claim 1. The switching drive circuit is
The first reference voltage of the first current detection circuit and the second reference voltage of the second current detection circuit are changed from the outside, and the first current detection circuit and the second current detection circuit It has a current detection value variable circuit that varies the current detection value,
The current detection value variable circuit is:
The dimming of the light emitting diode is enabled by varying the current detection values of the first current detection circuit and the second current detection circuit according to an external control signal. Item 10. The light-emitting diode driving device according to any one of Items 9. Providing a dimming control circuit for outputting a control signal from the outside for controlling dimming of the light emitting diode;
The current detection value variable circuit is:
12. The light emitting diode driving device according to claim 11, wherein current detection values of the first current detection circuit and the second current detection circuit are varied by the external control signal from the dimming control circuit. . The input voltage detection circuit is
Two resistors connected in series between the output side of the power supply unit and a reference potential;
A second comparator in which the DC voltage divided by the two resistors is input to the positive input terminal and the third reference voltage is input to the negative input terminal;
13. The light emitting diode driving device according to claim 5, wherein an output signal of the second comparator is output to the start / stop circuit. The input voltage detection circuit is
Three resistors connected in series between the output side of the power supply unit and a reference potential;
A third comparator in which a first divided voltage divided by the three resistors is input to a positive input terminal and a fourth reference voltage is input to a negative input terminal;
A fourth comparator in which the second divided voltage divided by the three resistors is input to the negative input terminal, and the fifth reference voltage is input to the positive input terminal;
An AND circuit in which each input terminal is connected to an output terminal of the third comparator and an output terminal of the fourth comparator;
13. The light emitting diode driving device according to claim 5, wherein an output signal of the AND circuit is output to the start / stop circuit. The control circuit includes:
The light emission according to any one of claims 1 to 14, further comprising an overheat protection circuit that stops on / off control of the first switching element when a temperature of the switching drive circuit reaches a predetermined value or more. Diode drive device. 16. The light emitting diode driving device according to claim 1, wherein a reverse recovery time of the diode is 100 nsec or less. 17. A semiconductor device for driving a light emitting diode, wherein the configuration of the switching drive circuit in the light emitting diode driving device according to claim 1 is formed on a single substrate using a semiconductor.

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