JP2015170673A - Led power supply for illumination - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an LED power supply for illumination in which feedback control of a forward current is not required, and light control with no flicker can be performed smoothly in the whole light control area.SOLUTION: An LED power supply of a one converter type comprises: a filter circuit 11, a full-wave rectifier 21, a switching circuit 41, and a microcomputer 81. The switching circuit 41 receives a full-wave rectification voltage V1, and supplies a forward current to an LED 61, by an interlock of a fly back transformer T1, a switching element Q1, a diode D1, and an electrolytic capacitor C2. The microcomputer 81 calculates a load current value for the lighting control condition by multiplying the current command value for the total light by coefficient in accordance with the detection value of the voltage V1, coefficient in accordance with detection value of load voltage Vf, and a lighting control rate, and outputs a rectangular wave voltage signal to the switching element Q1 in an ON width in accordance with the obtained load current value for the lighting control condition.

Description

  The present invention relates to an illumination LED power supply with a dimming function.

  A light-emitting diode (LED) power supply device for illumination basically requires constant current control due to the characteristics of the forward voltage and forward current of the LED. In this constant current control, in order to supply a continuous current to an LED, a switching circuit incorporating a storage element such as an inductance element, a switching element, and an electrolytic capacitor has been widely used.

  A conventional control circuit for driving the switching element is composed of an analog circuit. For example, in the analog control circuit of FIG. 16, the forward current of the LED is detected, a difference between the forward current and the target current is obtained by a comparator or the like, a PWM signal corresponding to the difference is created, and switching is performed. The element is driven.

  Patent Document 1 discloses that dimming control according to an external dimming signal is performed using an analog circuit that feedback-controls a detected value of the forward current of the LED. The dimming control of Patent Document 1 is an amplitude control method, and the current amplitude is adjusted by feedback control of the forward current, so that the forward current becomes a continuous current corresponding to the dimming signal. However, in the case of deep dimming around 0%, the detection of the forward current is stopped because the detection of the forward current becomes difficult, and the control is switched to the amplitude control according to only the target current value.

  However, the analog control circuit has a problem that the responsiveness to fluctuations in the input voltage is poor, and particularly in an illumination LED that reacts sensitively to slight fluctuations in current, the problem becomes significant. There was room for improvement.

  On the other hand, Patent Document 2 discloses dimming control by a microcomputer (hereinafter referred to as a microcomputer). In the dimming control of Patent Document 2, in dimming in a shallow region, a continuous current corresponding to the dimming signal is supplied to the LED by amplitude control. However, in dimming in a deep region, the amplitude control is stopped, and the switching element connected in series with the LED is driven at a low frequency of about 100 Hz to several kHz. Thereby, the forward current is intermittently paused at a low frequency, and the length of the current pause period is adjusted by the dimming rate (intermittent current control method). Since the LED blinks at a low frequency, the average value of the light output is adjusted according to the dimming rate.

JP 2010-067831 A JP 2009-123681 A

  In Patent Document 2, the feedback of the forward current is executed regardless of the shallow depth of light control. However, as described in Patent Document 1, in the case of deep light control around 0%, There was a problem that it would be difficult to detect. The reason will be briefly explained.

  An LED power supply device includes many sources of leakage magnetic flux, and a magnetic field and an electric field fly around. An electromotive force is generated in a circuit element by a magnetic field or an electric field, and this becomes noise of a control signal such as a feedback signal. In particular, in a region where light control is deep, the feedback signal becomes small, and the level difference (SN ratio) between the noise and the signal is almost eliminated, so that it is easily affected by noise. In this background, in order to reduce the size and increase the efficiency of the power supply device, the circuit elements are concentrated in a very narrow space, and accordingly, the control signal level must be designed to be small. is there. When feedback control is performed in such an environment, an accurate feedback signal cannot be obtained due to the influence of noise, the forward current of the LED is disturbed, and flickering occurs.

  In Patent Document 1, a method of stopping the feedback control of the forward current in the case of deep dimming is used. This feedback control is a countermeasure against fluctuations in the input voltage of the switching circuit and the forward voltage of the LED (also referred to as a load voltage here). If this is stopped, the forward current changes in voltage. Will be affected as it is, causing flickering. Further, in Patent Document 1, there is a problem that flicker is likely to occur even when shifting from a shallow region of light control to a deep region and when shifting from a deep region to a shallow region.

  Further, in Patent Document 2, when the above-described intermittent current control is started in the case of deep dimming, the power supply device operates intermittently (about 100 Hz to several kHz), so that beat occurs in the inductor and the transformer. There is also a problem.

  The present invention has been made in view of the above problems, and the object of the present invention is to eliminate the need for forward current detection and its feedback control, and to perform all adjustments from a light control region to a light control region. An object of the present invention is to provide an illumination LED power source that enables smooth dimming control without flicker in the light region.

  In order to solve the above-mentioned problems, the inventor noticed that the input voltage of the switching circuit and the LED load voltage are not easily affected by noise, and further, using a microcomputer, instantaneously processes the detected values of these voltages. It has been found that if the switching element is driven with the ON width corrected in this way, fluctuations in the forward current can be suppressed and good dimming control can be realized without using feedback control of the forward current.

That is, the LED power source for illumination of the present invention is
A voltage generation circuit that generates a full-wave rectified voltage or a DC voltage of a certain level or higher;
A switching circuit that receives the output voltage of the voltage generation circuit and generates a continuous current to the LED for illumination connected between the terminals of the storage element by interlocking the built-in inductance element, switching element, and storage element;
An input voltage detection circuit for detecting an output voltage of the voltage generation circuit as an input voltage (Vin);
A load voltage detection circuit for detecting a load voltage (Vf) of the LED;
And a microcomputer for determining the magnitude of a continuous current flowing through the LED.
The microcomputer is
The current command value (A) indicating the magnitude of the continuous current to the LED for making the all-light state,
An input voltage coefficient (B) corresponding to the detection signal of the input voltage (Vin), and
A load coefficient (C) corresponding to the detection signal of the load voltage (Vf), and
Multiply the dimming rate (D) according to the dimming signal from the outside to calculate the magnitude of the continuous current to the LED for the dimming state (A × B × C × D), A rectangular wave voltage signal is output to the switching element with an ON width corresponding to the calculated magnitude of the continuous current.

  The microcomputer has a data table of the load coefficient (C), and the data table is a correction value set so that the rated current of the LED is maintained with respect to the change of the load voltage (Vf). It is preferable that the number sequence is.

  Here, the microcomputer indexes the load coefficient data table by the average value of the detection signals of the load voltage (Vf) including the already detected signal, and loads the load coefficient (C ) Is preferably taken out.

  The microcomputer has a data table of the input voltage coefficient (B), and the data table is a correction set so that the rated current of the LED is maintained with respect to the change of the input voltage (Vin). A sequence of values is preferred.

  Here, when the output voltage of the voltage generation circuit is a full-wave rectified waveform, the microcomputer uses the input voltage coefficient data table as a peak of the full-wave rectified waveform in the detection signal of the input voltage (Vin). Indexed by value, or indexed by a value obtained by converting the detection signal of the input voltage (Vin) into a peak value of a full-wave rectified waveform, and the input voltage coefficient (B) corresponding to the peak value or the converted value is It is preferable to take out.

  On the other hand, when the output voltage of the voltage generation circuit is a direct current waveform of a certain level or more, the microcomputer indexes the data table of the input voltage coefficient by the average value of the detection signal of the input voltage (Vin), It is preferable to take out the input voltage coefficient (B) corresponding to the average value.

  In the present invention, in a switching circuit including an inductance element, a switching element, and a storage element, the switching element is driven based on a rectangular wave signal output from a microcomputer, and a continuous current corresponding to the dimming rate is generated by the interlocking of each element. Supplied to the LED. That is, the amplitude control of the LED becomes possible. The detected values of input voltage (Vin) and load voltage (Vf) that are not easily affected by noise are input to the microcomputer. Then, the microcomputer uses the current command value (A) for making it all light (100% lighting), the input voltage coefficient (B) according to the input voltage (Vin), and the load according to the load voltage (Vf). The coefficient (C) is multiplied by the dimming rate (D) to calculate the magnitude of the continuous current to the LED for the dimming state (A × B × C × D). Further, the microcomputer outputs a rectangular wave voltage signal to the switching element with an ON width corresponding to the calculated continuous current.

  If the microcomputer is used in this way, the detected values of the input voltage and the load voltage can be processed instantaneously. When these voltages fluctuate, the switching element is instantly corrected based on the detected value with the ON width. Therefore, fluctuations in the forward current can be suppressed without using forward current feedback control. Therefore, according to the present invention, smooth dimming control without flickering can be satisfactorily performed in all the areas from a shallow area to a deep area without performing forward current detection and feedback control thereof. There is an effect.

It is a block circuit diagram which shows the structure of Embodiment 1 of this invention. It is a calculation flowchart which shows operation | movement of Embodiment 1 of this invention. The block circuit diagram which shows the structure (one converter system) of Embodiment 2 of this invention. The block circuit diagram which shows the structure (two converter system) of Embodiment 3 of this invention. It is a figure which shows the sampling method of the LED forward voltage of the said Embodiment 2. FIG. It is a figure which shows the sampling method of the input voltage of the full wave rectification waveform of the said Embodiment 2. It is a figure which shows the sampling method of the input voltage of the direct current | flow waveform beyond the fixed level of the said Embodiment 3. FIG. It is a figure which shows another sampling method of the LED forward voltage of the said Embodiment 2. FIG. It is a figure which shows another sampling method of the input voltage of the full wave rectification waveform of the said Embodiment 2. FIG. It is a figure for demonstrating the operation example of the switching circuit of this invention. It is a wave form diagram which shows the example of operation simulation of the switching circuit of this invention. It is a wave form diagram which shows the example of operation simulation of the forward current when the fluctuation | variation arises in the input voltage of the power supply device for 100V. It is a wave form diagram which shows the example of operation simulation of the forward current when the fluctuation | variation arises in the input voltage of the power supply device for 100V. It is a wave form diagram which shows the example of operation simulation of the forward current when the fluctuation | variation arises in the input voltage of the power supply device for 200V. It is a wave form diagram which shows the example of operation simulation of the forward current when the fluctuation | variation arises in the input voltage of the power supply device for 200V. The block circuit diagram which shows the structure of the power supply device provided with the conventional analog type control circuit.

(Embodiment 1)
FIG. 1 shows a circuit configuration of an illumination LED power source according to Embodiment 1 of the present invention. The LED power supply for illumination 10 includes a voltage generation circuit 2, a switching circuit 4, an LED load 6, a microcomputer 8, an input voltage detection circuit 12, and a load voltage detection circuit 14.

  The voltage generation circuit 2 converts the AC voltage from the external AC power supply AC into a predetermined DC voltage and supplies the DC voltage to the switching circuit 4. The input voltage Vin to the switching circuit 4 is detected by the input voltage detection circuit 12 and the detected value is input to the microcomputer 8.

  The switching circuit 4 includes an inductance element L1, a switching element Q1, and an electrolytic capacitor C1. The electrolytic capacitor C1 corresponds to the electricity storage device of the present invention. When the switching circuit 4 receives the input voltage Vin, the inductance element L1, the switching element Q1, and the electrolytic capacitor C1 work together to store a predetermined charge in the electrolytic capacitor C1, and are connected between the terminals of the electrolytic capacitor C1. A predetermined continuous current is supplied to the LED load 6.

  The forward voltage Vf of the LED load 6 is detected by the load voltage detection circuit 14, and the detected value is input to the microcomputer 8. A dimming signal from an external dimmer or the like is input to the microcomputer 8. The microcomputer 8 calculates the magnitude of the continuous current flowing through the LED load based on the current command value stored in the memory, the input voltage coefficient, the load coefficient, and the dimming rate according to the dimming signal. In order to output a rectangular wave signal to the switching element Q1 with an ON width corresponding to the magnitude of the continuous current. A specific operation example of the microcomputer 8 will be described with reference to FIG.

  The microcomputer 8 has a plurality of data tables as shown in FIG.

The current command value data table A is a sequence of current command values, and this current command value is the magnitude of the forward current (continuous current to the LED) required to make it all light (100% dimming). Indicates. Usually, the numerical sequence is in the range of 300 mA to 2000 mA. For example, it may be a sequence of current command values corresponding to the soft start function. When the rated current is 600 mA, a sequence of current command values corresponding to the elapsed time from the start of lighting is provided as a data table so that the forward current gradually increases to 600 mA over several hundred milliseconds from the start of lighting. Also good.
In addition, it is good also as a numerical sequence of the current command value corresponding to the time-dependent change of LED load.
Note that a value fixed as the current command value may be written in the microcomputer without providing the data table.

  The input voltage coefficient data table B is a sequence of input voltage coefficients corresponding to the detection signal of the input voltage Vin. Usually, the numerical sequence is in the range of 0.6 to 1.4. For example, it can be a sequence of correction values set so that the rated current of the LED is maintained even when the input voltage Vin varies. Thereby, fluctuations in the forward current of the LED due to fluctuations in the input voltage Vin from the AC power source AC or the like can be eliminated.

  The load coefficient data table C is a sequence of load coefficients corresponding to the detection signal of the load voltage Vf. Usually, a numerical sequence is set in the range of 0.6 to 1.4. For example, it can be a sequence of correction values set so that the rated current of the LED is maintained even when the load voltage Vf varies.

  The dimming signal is input to the microcomputer in the range of 0% dimming to 100% dimming.

  The on width calculation routine in the microcomputer 8 is as follows. First, the current current command value is read from the current command value data table A. For example, 600 mA of the rated current of the LED load is read. From the load coefficient data table C, the load coefficient corresponding to the detection signal of the load voltage Vf is read. Here, assuming that one of the LED elements is damaged and the load voltage Vf fluctuates, for example, 0.9 is read. The reason of 0.9 is to suppress the supply current. From the input voltage coefficient data table B, the input voltage coefficient corresponding to the detection signal of the input voltage Vin is read. Here, for example, 1.2 is read assuming that the AC power supply AC fluctuates and the input voltage Vin decreases. In addition, it is assumed that the dimming signal D currently input to the microcomputer 8 indicates a dimming rate of 5%. In such a case, the microcomputer 8 multiplies the current command value (600 mA) by the load coefficient (0.9), the input voltage coefficient (1.2), and the dimming rate (0.05). (600 × 0.9 × 1.2 × 0.05 = 32.4), 32.4 mA is calculated as the magnitude of the forward current for achieving the dimming state. As described above, when the rated current is 600 mA, the forward current of 5% dimming is 30 mA. However, as a result of correction based on voltage fluctuation, a forward current of 32.4 mA can flow when there is no voltage fluctuation. The switching element Q1 is driven with the ON width, and the same 30 mA flows as when there is no voltage fluctuation in the load. A rectangular wave voltage signal (for example, 0-5V signal) is output to the switching element Q1 with the ON width. Thus, the on width calculation routine is completed once.

  This calculation routine is executed for each voltage sampling pitch. Depending on the processing capability of the microcomputer (MPU), the calculation routine is preferably executed approximately every 100 to 1000 μsec. When the drive voltage of the switching element is 12V, a level conversion circuit 16 that converts the output voltage 5V of the microcomputer 8 to 12V as shown in FIG. 1 may be provided between the microcomputer 8 and the switching element Q1.

  In Patent Documents 1 and 2, the fluctuation of the input voltage is dealt with by feedback control of the forward current. However, in this embodiment, there is no feedback control of forward current as in Patent Documents 1 and 2, and instead, the microcomputer 8 of this embodiment has each of the input voltage Vin and the load voltage Vf that are less susceptible to noise. A detection value is input. The microcomputer 8 can instantaneously process the detected values of the input voltage Vin and the load voltage Vf. When these voltages fluctuate, the microcomputer 8 controls the switching element Q1 with an ON width that is instantaneously corrected based on the detected values. Since it can be driven, fluctuations in forward current can be suppressed. Accordingly, smooth dimming control without flickering can be satisfactorily performed in all regions from a light-dimming region to a deep region without detecting forward current and its feedback control.

  Further, if this calculation routine is used, the dimming control method does not change depending on the dimming rate. Therefore, “flicker” associated with the shift of the control method as in Patent Document 1 does not occur, and “beat” associated with the shift of the control method as in Patent Document 2 does not occur.

(Embodiment 2)
FIG. 3 shows a circuit configuration of an illumination LED power source according to Embodiment 2 of the present invention. The LED power source 110 for illumination has a circuit configuration when the present invention is adopted in an insulating one converter.

  As shown in FIG. 3, 11 is a filter circuit for countermeasures against EMI, 21 is a full-wave rectifier, 41 is a switching circuit, 81 is a control circuit, and has a built-in MPU (micro processor unit). The switching circuit 41 is a flyback converter, and a voltage dividing circuit of resistors R11 and R12, a flyback transformer T1, a switching element Q1, a diode D1, an electrolytic capacitor C2, a voltage dividing circuit of resistors R21 and R22. It consists of and. The transformer T1 corresponds to the inductance element of the present invention. The MPU calculates the ON width of the rectangular wave signal that drives the switching element Q1. Reference numeral 51 denotes an interface circuit that insulates the dimming signal and processes it into a signal in a format that is easily recognized by the MPU in the control circuit 81.

  A capacitor C1 is provided after the full-wave rectifier 21. The control circuit 81 is configured to divide the full-wave rectified voltage V1 (corresponding to the input voltage Vin) for calculating the input voltage coefficient by the voltage dividing circuit of the resistor R11 and the resistor R12 connected between the terminals of the capacitor C1. It is supplied to the A / D converter of the internal MPU.

  A series circuit of a primary coil of the transformer T1 and a switching element Q1 is further connected between the terminals of the capacitor C1. A capacitor C3 is connected between the drain and source of the switching element Q1 in order to execute on / off driving (pseudo-resonance method) with a change in switching period.

A series circuit of a diode D1 and an electrolytic capacitor C2 is connected to the secondary coil of the flyback transformer T1. The voltage dividing circuit of the resistor R21 and the resistor R22 connected between the terminals of the electrolytic capacitor C2 converts the voltage division of the forward voltage Vf of the LED load for calculating the load coefficient into the control circuit 81 via the insulation amplifier 31. Supplied to the MPU A / D converter.
In this way, the detected values of the full-wave rectified voltage V1 and the forward voltage Vf are input to the MPU of the present embodiment, and the MPU processes these detected values instantaneously and is corrected instantaneously based on the detected values. The switching element Q1 is driven with the ON width. As a result, fluctuations in the forward current of the LED load 61 can be suppressed. Therefore, smooth light control without flickering can be satisfactorily performed in the insulated one converter.

(Embodiment 3)
FIG. 4 shows a circuit configuration of an illumination LED power source according to Embodiment 3 of the present invention. The LED power supply 210 for illumination has a circuit configuration when the present invention is applied to a non-insulated two-converter.

  As shown in FIG. 4, 11 is a filter circuit for EMI countermeasures, 21 is a full-wave rectifier, 43 is a switching circuit, 83 is a control circuit, and has a built-in MPU. The switching circuit 43 is a step-down chopper circuit, and includes a voltage dividing circuit of resistors R11 and R12, a diode D1, an electrolytic capacitor C2, an inductance element L1 such as a coil, a switching element Q1, a resistor R21, and a resistor R22. And a voltage dividing circuit. The MPU calculates the ON width of the rectangular wave that drives the switching element Q1. Reference numeral 51 denotes an interface circuit that insulates the dimming signal and processes it into a signal in a format that is easily recognized by the MPU in the control circuit 83. Reference numeral 71 denotes a power factor correction circuit composed of a boost shopper circuit or the like. A capacitor C1 is provided between the full-wave rectifier 21 and the power factor correction circuit 71, and an electrolytic capacitor is provided between the power factor correction circuit 71 and the switching circuit 43. C3 is provided.

  The voltage dividing circuit of the resistor R11 and the resistor R12 connected between the terminals of the electrolytic capacitor C3 can divide the output voltage V2 (corresponding to the input voltage Vin) of the power factor correction circuit for calculating the input voltage coefficient. The A / D converter of the MPU in the control circuit 83 is supplied.

  Further, a series circuit of an electrolytic capacitor C2, an inductance element L1, and a switching element Q1 is connected between the terminals of the electrolytic capacitor C3. Note that a diode D1 is connected between the terminals of the series circuit of the electrolytic capacitor C2 and the inductance element L1, and a regenerative current from the inductance element L1 passes through the diode D1 during the OFF period of the switching element Q1 and is a positive electrode of the electrolytic capacitor C2. It is designed to flow to the side. Further, a voltage dividing circuit of resistors R21 and R22 is connected between terminals of the series circuit of the inductance element L1 and the switching element Q1.

The voltage dividing circuit of the resistor R21 and the resistor R22 supplies the divided voltage of the negative voltage V3 of the electrolytic capacitor C2 to the A / D converter of the MPU in the control circuit 83. The calculation of V2-V3 = Vf is executed by the MPU internal program, and the forward voltage Vf of the LED load is obtained.
In this way, the detected values of the output voltage V2 and the forward voltage Vf of the power factor correction circuit are input to the MPU of this embodiment, and the MPU processes these detected values instantaneously, and instantaneously based on the detected values. The switching element Q1 is driven with the ON width corrected to. As a result, fluctuations in the forward current of the LED load 61 can be suppressed. Therefore, smooth dimming control without flicker can be satisfactorily performed in the non-insulated two-converter.

  FIG. 5 shows a load coefficient reading method in the second and third embodiments. The load coefficient data table C is indexed from the average value of the forward voltage Vf of the LED load to read the load coefficient. You may index using the value which averaged the maximum value and minimum value of the detected value. This data table C is a sequence of correction values for allowing the rated current (in all light) to flow even when the forward voltage Vf of the LED load changes.

  FIG. 6 shows a method for reading an input voltage coefficient in the one-converter system of the second embodiment. The input voltage coefficient data table B is indexed using the peak value of the pulsating full-wave rectified voltage V1 as a key, and the input AC voltage coefficient is read. This data table B is a sequence of correction values for allowing the rated current (in all light) to flow even when the full-wave rectified voltage V1 changes.

  FIG. 7 shows a method of reading an input voltage coefficient in the two-converter system of the third embodiment. The data table B 'is indexed by the average value of the output voltage V2 of the power factor correction circuit 71, and the input voltage coefficient is read. The output voltage V2 of the power factor correction circuit 71 as a voltage generation circuit has a direct current waveform of a certain level or higher. You may index using the value which averaged the maximum value and minimum value of the detected value. This data table B ′ is a correction value for allowing the rated current (in all light) to flow even when the output voltage V2 of the power factor correction circuit 71 changes due to the influence of fluctuations in the AC voltage or the like. It is a sequence of numbers.

  FIG. 8 shows another method of reading the load coefficient in the second and third embodiments. In this example, the MPUs in the control circuits 81 and 83 index the load coefficient data table by the average value of the detection signals of the load voltage Vf including the already detected signals, and calculate the load coefficient according to the average value. Take out. What is characteristic in this example is that the detected value of the pulsating load voltage Vf is not added and averaged as it is, but the load voltage Vf is sampled at a specific timing in a period corresponding to one cycle of the AC power supply. is there. The sampling is executed in accordance with the cycle of the AC power source. A value obtained by averaging the obtained detection values is used as a key for indexing table data.

  FIG. 9 shows another method of reading the input voltage coefficient in the second embodiment. In this example, the detection timing of the fluctuation of the full-wave rectified voltage V1 is 10 points per cycle of the AC power supply. The MPU in the control circuit 81 indexes the input voltage coefficient data table B by the peak value (sample points 3 and 8) of the full-wave rectified waveform among the sample points 1 to 10 of the full-wave rectified voltage V1, or The sample points other than 3 and 8 are indexed by the value converted into the peak value of the full-wave rectified waveform, and the input voltage coefficient corresponding to the peak value or the converted value to the peak value is taken out.

  What is characteristic in this example is that the index key changes instantaneously based on the detected value of the full-wave rectified voltage V1 at any sampling point when the instantaneous input AC voltage drops, and the input voltage coefficient The indexing position of the data table B is instantaneously moved. As a result, the ON width of the switching element Q1 is calculated by the new input voltage coefficient, and the instantaneous input AC voltage can be instantly dealt with. The sample points per cycle are preferably set in the range of 5 points to 100 points.

  FIG. 10 shows an operation example of the one-converter power supply circuit according to the second embodiment. The waveforms of the full-wave rectified voltage V1, the rectangular wave signal, and the forward current If at dimming rates of 100%, 60%, and 20% from the left are arranged in the horizontal direction.

  When the on-width of a rectangular wave signal at a dimming rate of 100% is represented by 1.0, the on-width at a dimming rate of 60% is represented by 0.6, and the on-width at a dimming rate of 20% is represented by 0.2. Can do. However, the ON width when there is no change in the input voltage V1 and the load voltage Vf is shown. Since the flyback circuit is used in the one-converter system, the current on the secondary side of the transformer T1 increases when the rectangular wave signal is off, and decreases when the rectangular wave signal is on. The average value of the transformer secondary-side current waveform indicated by the triangular waveform is the LED forward current If. Here, since the quasi-resonant method is employed, the switching period also changes as the ON width changes.

  When the dimming rate is changed from 100% to 60%, the ON width is simply 0.6 under the condition that there is no voltage fluctuation. Even when the dimming rate is decreased from 60% to 20%, the ON width is simply 0.2 under the condition that there is no voltage fluctuation. However, when the dimming rate is 60% and the full-wave rectified voltage V1 is instantaneously decreased (A → B) as shown in FIG. 10, the ON width is set according to the detection value at the immediately following sample point. Immediately changed from 0.6 to 0.8. Thereby, the forward current If is maintained at the level before the fluctuation, and the influence of the decrease in the full-wave rectified voltage V1 can be covered. When the voltage V1 further decreases, the ON width is further changed from 0.8 to 0.85 according to the detection value at the subsequent sample point.

  FIG. 11 shows an example of an operation simulation of the one-converter power supply circuit according to the second embodiment. When the dimming in the shallow region and the dimming in the deep region are freely changed, the gate voltage waveform of the switching element Q1 is arranged in the lower stage, and the drain voltage waveform is arranged in the upper stage. As the waveform is on the right side, the ON period T1 of the gate waveform becomes narrower. It can be seen that the switching period varies because the quasi-resonant method is employed. It can also be seen that the zero voltage period T2 of the drain voltage waveform gradually narrows with the change in the ON width T1.

12 to 15 show examples of operation simulation of power supply voltage drop response characteristics in the one-converter power supply circuit of the second embodiment.
The response waveform of the forward current If of the LED when the input AC power supply voltage drops by 30% for 30 milliseconds is shown. The frequency of the AC power supply is 60 hertz. The angle given to each waveform indicates the phase angle of the voltage waveform at the start of the voltage drop.
In the figure, the upper waveform is the waveform of the LED forward current If, and the lower waveform is the waveform of the full-wave rectified voltage V1. The period in which the voltage is rising in the middle waveform indicates the period during which the input AC power supply voltage is recognized by the microcomputer.
12 and 13 show the case where the rated voltage of the LED is 100V, and FIGS. 13 and 14 show the case where the rated voltage of the LED is 200V.
Regardless of the phase angle (5 °, 20 °, 45 °, 70 °, 90 °, 110 °, 135 °, 150 °, 175 °), the output waveform of the LED will not be disturbed, It can be seen that an orderly output waveform is obtained.

4, 41, 43 Switching circuit 6, 61 LED load 8, 81, 83 Control circuit (microcomputer)
10, 110, 210 LED power supply for illumination 11 Filter circuit 12 Input voltage detection circuit 14 Load voltage detection circuit 16 Level conversion circuit 21 Full-wave rectifier (voltage generation circuit)
51 Interface circuit 71 Power factor correction circuit (voltage generation circuit)
A Current command value data table B Input voltage coefficient data table C Load coefficient data table V1 Full-wave rectified voltage (corresponding to the input voltage of the present invention)
Output voltage of the V2 power factor correction circuit (corresponding to the input voltage of the present invention)
Vf Load voltage (forward voltage)

Claims (6)

A voltage generation circuit that generates a full-wave rectified voltage or a DC voltage of a certain level or higher;
A switching circuit that receives the output voltage of the voltage generation circuit and generates a continuous current to the LED for illumination connected between the terminals of the storage element by interlocking the built-in inductance element, switching element, and storage element;
An input voltage detection circuit that detects an output voltage of the voltage generation circuit as an input voltage (Vin);
A load voltage detection circuit for detecting the load voltage (Vf) of the LED;
A microcomputer for determining the magnitude of a continuous current flowing through the LED;
An illumination LED power source comprising: the microcomputer,
In the current command value indicating the magnitude of the continuous current to the LED to make it all light state,
An input voltage coefficient according to a detection signal of the input voltage (Vin), and
A load coefficient corresponding to a detection signal of the load voltage (Vf), and
Dimming rate according to the dimming signal from the outside,
To calculate the amount of continuous current to the LED for dimming,
A lighting LED power supply, wherein a rectangular wave voltage signal is output to the switching element with an ON width corresponding to the calculated continuous current. In the LED power supply for illumination according to claim 1,
The microcomputer has a data table of the load coefficient, and the data table is a sequence of correction values set so that the rated current of the LED is maintained with respect to changes in the load voltage (Vf). An LED power supply for illumination, characterized in that there is. The illumination LED power supply according to claim 2,
The microcomputer indexes the load coefficient data table by the average value of the detection signals of the load voltage (Vf) including the already detected signal, and extracts the load coefficient (C) according to the average value. An LED power supply for illumination characterized by the above. In the LED power supply for illumination according to claim 1,
The microcomputer has a data table of the input voltage coefficient, and the data table is a sequence of correction values set so that the rated current of the LED is maintained with respect to changes in the input voltage (Vin). The LED power supply for illumination characterized by being. The illumination LED power supply according to claim 4,
When the output voltage of the voltage generation circuit is a full-wave rectified waveform, the microcomputer indexes the data table of the input voltage coefficient by the peak value of the full-wave rectified waveform in the detection signal of the input voltage (Vin). Alternatively, the detection signal of the input voltage (Vin) is indexed by a value converted into a peak value of a full-wave rectified waveform, and an input voltage coefficient corresponding to the peak value or the converted value is extracted. LED power supply for lighting. The illumination LED power supply according to claim 4,
When the output voltage of the voltage generation circuit is a direct current waveform of a certain level or more, the microcomputer indexes the data table of the input voltage coefficient by the average value of the detection signal of the input voltage (Vin), the average An LED power supply for illumination, wherein an input voltage coefficient corresponding to the value is extracted.