JP5732608B2 - Semiconductor light-emitting element lighting device and lighting fixture using the same - Google Patents

Description

  The present invention relates to a semiconductor light emitting device lighting device for lighting a semiconductor light emitting device such as a light emitting diode (LED) and a lighting fixture using the same.

  According to Patent Document 1 (Japanese Patent No. 4100400), it is proposed to use a microcomputer as a control means for controlling on / off of a switching element in an apparatus for lighting an LED using a switching power supply circuit. Has been. In this conventional example, a first amplifier for detecting a load voltage and a second amplifier for detecting a load current are connected to a first input terminal and a second input terminal of the microcomputer, respectively, and the switching element is driven on / off. A driver circuit unit for connecting to the output terminal of the microcomputer is connected. In the microcomputer, there are a reference value generation unit that generates a reference value from the detection value of the load voltage and the detection value of the load current, an error calculation unit that calculates an error between the actual detection value and the reference value, and an error calculation unit And a PWM control unit that PWM-controls the ON period of the switching element in a direction that reduces the error.

Japanese Patent No. 4100400 (Claim 8, 0049-0051, FIG. 7, FIG. 6)

  In the technique of Patent Document 1, a control mode in which an external signal such as a dimming signal is input to a microcomputer that controls on / off of a switching element has not been assumed. In recent years, microcomputers for control have also become faster, so if you use the processing functions of the microcomputer in a time-sharing manner, it will be possible to input external signals such as dimming signals and reflect them in the control. Conceivable. However, if the external signal input process is started at the timing when the switching element is turned on, a situation may occur in which the switching element cannot be turned off until the external signal input process is completed. In that case, the current flowing through the switching element may become excessive, or the inductance element may be magnetically saturated, resulting in a decrease in control accuracy.

  According to the present invention, when the current flowing through the inductance element reaches a predetermined value when the switching element is turned on, the switching element is controlled to be off, and when the switching element is turned off, the current discharged from the inductance element to the semiconductor light emitting element through the regenerative diode is zero. Then, in a lighting device for a semiconductor light-emitting element that controls on / off of the switching element, an object is to input an external signal such as a dimming signal to a microcomputer that controls on / off of the switching element and reflect it in the control.

  In order to solve the above problems, the invention of claim 1 is, as shown in FIG. 1, a switching element Q1 connected in series to a DC power source (capacitor C1) and controlled to be turned on and off at a high frequency; and the switching element Q1 An inductor L1 that is connected in series and through which a current flows from the DC power source when the switching element Q1 is turned on; energy stored in the inductor L1 when the switching element Q1 is turned on; and the semiconductor light emitting element 4 when the switching element Q1 is turned off A regenerative diode D1 that discharges to the switching element; current detecting means (resistor R1) that detects a current flowing through the switching element Q1; and when the current value detected by the current detecting means reaches a predetermined value, the switching element Q1 is turned off. At the same time, when the energy discharge of the inductor L1 is completed, In a lighting device for a semiconductor light emitting device comprising a control means for turning on the etching element Q1, the control means includes an A / D conversion input terminal P0 for reading a current value detected by the current detection means (resistor R1), and It is characterized by comprising a one-chip microcomputer 5 having a zero-crossing detection terminal P2 for detecting completion of energy discharge of the inductor L1 and an output terminal P1 for controlling on / off of the switching element Q1.

The invention of billed claim 1, characterized in that the front Symbol zero cross detection pin P2 was also used the A / D conversion input terminal P0 (FIG. 5, FIG. 6).

A second aspect of the present invention, in the lighting device of the semiconductor light emitting device according to claim 1 Symbol placement, the 1-chip microcomputer 5, an external signal input terminal for inputting an external signal including a dimming signal or sensor signal P3~P5 And an external signal read processing unit (# 5 and # 6 in FIG. 3) for reading the external signal during the OFF period of the switching element Q1, and a peak for resetting the predetermined value according to the read external signal And a current setting processing unit (# 7 in FIG. 3).

The invention according to claim 3, in the lighting device of the semiconductor light emitting device according to claim 2 Symbol placement, the external signal is a square wave signal having a sufficiently low frequency as compared with the ON / OFF frequency of the switching element Q1, the The external signal reading processing unit measures the on period or the off period of the rectangular wave signal by observing the state of the rectangular wave signal for each off period of the switching element Q1.

A fourth aspect of the present invention, in the lighting device of the semiconductor light emitting device according to claim 3 Symbol placement, the external signal reading processing unit over a plurality of cycles of the low frequency of the ON period or OFF period of the measured the square wave signal An averaging processing unit (# 20 and # 22 in FIG. 4) for averaging is provided.

According to a fifth aspect of the present invention, in the lighting device for a semiconductor light emitting element according to any one of the second to fourth aspects, the one-chip microcomputer 5 includes a plurality of the external signal input terminals P3 to P5, The signal reading processing unit sequentially reads external signals from the external signal input terminals P3 to P5 during different off periods of the switching element Q1.

The invention of claim 6 is a lighting apparatus comprising the lighting device for a semiconductor light emitting element according to any one of claims 1 to 5 and the semiconductor light emitting element to which a current is supplied from the lighting device (FIG. 8).

  According to the configuration of the present invention, when the peak value of the current flowing through the switching element, the value of the inductance element, the terminal voltage of the semiconductor light emitting element, and the voltage of the DC power supply are determined, the ON period and the OFF period of the switching element are uniquely determined. Therefore, processing other than the on / off control of the switching element, for example, reading processing of an external signal such as a dimming signal can be reliably performed during the predictable waiting time.

It is a circuit diagram of the lighting device of Embodiment 1 of the present invention. It is a circuit diagram which shows the structural example of the sensor which gives an external signal to the lighting device of Embodiment 1 of this invention. It is a flowchart which shows the whole operation | movement of the microcomputer used for the lighting device of Embodiment 1 of this invention. It is a flowchart of the signal reading process part of the microcomputer used for the lighting device of Embodiment 1 of this invention. It is a circuit diagram of the lighting device of Embodiment 2 of the present invention. It is a circuit diagram of the lighting device of Embodiment 3 of the present invention. It is a circuit diagram of various switching power supply circuits to which the present invention can be applied. It is sectional drawing which shows schematic structure of the lighting fixture of Embodiment 5 of this invention.

(Embodiment 1)
FIG. 1 is a circuit diagram of a lighting device according to Embodiment 1 of the present invention. This lighting device includes a step-down chopper circuit 3 that steps down a DC voltage of a smoothing capacitor C1 that is a DC power source and supplies a DC current to a semiconductor light emitting element 4 that is a load, and a control circuit (microcomputer 5). .

  The smoothing capacitor C1 serving as a DC power supply is charged with a DC voltage obtained by full-wave rectifying a commercial AC power supply using a full-wave rectifier (not shown), for example. Generally, a filter circuit for removing high frequency components is provided on the AC input side of the full-wave rectifier. Further, a power factor correction circuit using a step-up chopper circuit or the like may be interposed between the DC output side of the full-wave rectifier and the smoothing capacitor C1.

  The step-down chopper circuit 3 includes an inductor L1 connected in series to the semiconductor light emitting element 4 that is lit by a direct current, and a series circuit of the inductor L1 and the semiconductor light emitting element 4 between both ends of a smoothing capacitor C1 that serves as a DC power source. The switching element Q1 to be connected is connected in parallel with the series circuit of the inductor L1 and the semiconductor light emitting element 4, and is connected in a direction in which the stored energy of the inductor L1 is discharged to the semiconductor light emitting element 4 when the switching element Q1 is turned off. The regenerative diode D1 is provided. Further, an output capacitor C2 is connected in parallel with the semiconductor light emitting element 4. The output capacitor C2 is set to have a capacitance so that a pulsating component due to the on / off of the switching element Q1 is smoothed and a smoothed DC current flows through the semiconductor light emitting element 4. The semiconductor light emitting element 4 may be an LED module in which a plurality of LEDs are connected in series, in parallel, or in series-parallel.

  The switching element Q1 is driven on and off at a high frequency by a one-chip microcomputer 5 for control. The microcomputer 5 includes an A / D conversion input terminal P0, a binary output terminal P1, and binary input terminals P2 to P5 in addition to the power supply terminal Vcc and the ground terminal GND.

  The A / D conversion input terminal P0 has a function of converting an analog input voltage into a digital value and taking it in. The binary output terminal P1 has a function of outputting either a high level signal or a low level signal. The binary input terminals P2 to P5 have a function of determining whether the input voltage is at a high level or a low level.

  A voltage across the current detection resistor R1 connected in series with the switching element Q1 is input to the A / D conversion input terminal P0 as a detection value of the switching current. A gate driver circuit formed by connecting inverters G1 to G4 in parallel is connected to the binary output terminal P1. A voltage induced in the secondary winding n2 of the inductor L1 is input to the binary input terminal P2 via the resistor R5. A dimming signal output from the dimming circuit 6 is input to the binary input terminal P5. Sensor signals output from the sensors 7a and 7b are input to the binary input terminals P4 and P3, respectively. The sensor 7a is, for example, a temperature sensor (see FIG. 2A), and the sensor 7b is, for example, a color sensor (see FIG. 2B), but is not limited thereto.

  When a control power supply voltage equal to or higher than a predetermined voltage is supplied between the power supply terminal Vcc and the ground terminal GND, a control operation as shown in a flowchart of FIG. It switches to High / Low at a high frequency of. When the binary output terminal P1 becomes Low level, the output of the gate driver circuit formed by connecting the inverters G1 to G4 in parallel becomes High level.

  When the output of the gate driver circuit becomes High level, the gate drive voltage divided by the resistors R3 and R4 in FIG. 1 is applied between the gate and source of the switching element Q1 made of MOSFET. Since the resistor R1 is a small resistor for current detection, it hardly affects the drive voltage between the gate and the source.

  When the switching element Q1 is turned on, a current flows from the positive electrode of the capacitor C1 to the negative electrode of the capacitor C1 via the output capacitor C2, the inductor L1, the switching element Q1, and the resistor R1. At this time, the chopper current i flowing through the inductor L1 is a current that rises substantially linearly unless the inductor L1 is magnetically saturated. This current is detected by the resistor R1 and input to the A / D conversion input terminal P0 of the microcomputer 5.

  At the A / D conversion input terminal P0 of the microcomputer 5, the input voltage is A / D converted and converted into a digital value, and obtained as a detected value of the switching current. When the detected value of the switching current reaches a predetermined value set in the microcomputer 5, the microcomputer 5 sets the binary output port P1 to the high level. As a result, the output of the gate driver circuit formed by connecting the inverters G1 to G4 in parallel becomes a low level.

  At this time, since the gate driver circuit operates so as to draw current from the output terminal, the diode D2 in FIG. 1 is turned on, and the gate-source charge of the switching element Q1 is drawn through the resistor R2, thereby comprising the MOSFET. The switching element Q1 is quickly turned off.

  When the switching element Q1 is turned off, the electromagnetic energy stored in the inductor L1 is released to the output capacitor C2 via the regenerative diode D1. At this time, since the voltage across the inductor L1 is clamped to the voltage Vc2 of the output capacitor C2, the current i of the inductor L1 decreases with a substantially constant slope (di / dt≈−Vc2 / L1).

  When the voltage Vc2 of the capacitor C2 is high, the current i of the inductor L1 is rapidly attenuated. When the voltage Vc2 of the capacitor C2 is low, the current i of the inductor L1 is slowly attenuated. Therefore, even if the peak value of the current flowing through the inductor L1 is constant, the time until the current i of the inductor L1 disappears changes. The required time is shorter as the voltage Vc2 of the capacitor C2 is higher and longer as the voltage Vc2 is lower.

  During the period when the current i flows through the inductor L1, a voltage corresponding to the slope of the current i of the inductor L1 is generated in the secondary winding n2 of the inductor L1. This voltage disappears when the current i of the inductor L1 finishes flowing. The timing is detected at the binary input terminal P2.

  When the induced voltage of the secondary winding n2 applied to the binary input terminal P2 via the resistor R5 disappears, the state of the binary input terminal P2 changes from High level to Low level. In response to this change, the microcomputer 5 sets the binary output terminal P1 to the low level. As a result, the output of the gate driver circuit formed by connecting the inverters G1 to G4 in parallel becomes High level, and the switching element Q1 is turned on again. Thereafter, the same operation is repeated.

  In this way, a DC voltage obtained by stepping down the voltage of the capacitor C1 is obtained at the output capacitor C2. This DC voltage is supplied to the semiconductor light emitting element 4 via the output connector CON2. When a light emitting diode (LED) is used as the semiconductor light emitting element 4, when the forward voltage of the LED is Vf and the number of series is n, the voltage Vc2 of the output capacitor C2 is clamped to approximately n × Vf.

  When the number n of LEDs in series is large, the voltage Vc2 of the output capacitor C2 is high, so that the voltage difference (Vc1−Vc2) from the voltage Vc1 of the capacitor C1 is small. For this reason, the voltage shared by the inductor L1 when the switching element Q1 is on is small, and the rising speed di / dt = (Vc1−Vc2) / L1 of the current i flowing through the inductor L1 is slow. As a result, the time until the current i flowing through the inductor L1 reaches a predetermined peak value becomes longer, and the on-time of the switching element Q1 becomes longer.

  When the switching element Q1 is off, the back electromotive force generated at both ends of the inductor L1 is clamped to the voltage Vc2 (= n × Vf) of the capacitor C2. For this reason, when the number n of LEDs in series is large, the voltage applied to the inductor L1 is large when the switching element Q1 is turned off, and the decay rate di / dt = −Vc2 / L1 of the current i flowing through the inductor L1 becomes fast. As a result, the time until the current i flowing through the inductor L1 becomes zero becomes short, and the OFF time of the switching element Q1 becomes short.

  When the number n of LEDs in series is small, the on-time of the switching element Q1 becomes short and the off-time becomes long, contrary to the above description. That is, when the number n of LEDs in series is small, the voltage Vc2 of the output capacitor C2 is low, and the voltage difference (Vc1−Vc2) from the voltage Vc1 of the capacitor C1 becomes large. For this reason, the voltage shared by the inductor L1 when the switching element Q1 is turned on is large, and the rising speed di / dt = (Vc1−Vc2) / L1 of the current i flowing through the inductor L1 is increased. As a result, the time until the current i flowing through the inductor L1 reaches a predetermined peak value is shortened, and the ON time of the switching element Q1 is shortened.

  When the switching element Q1 is off, the back electromotive force generated at both ends of the inductor L1 is clamped to the voltage Vc2 (= n × Vf) of the capacitor C2. For this reason, when the number n of LEDs in series is small, the voltage applied to the inductor L1 when the switching element Q1 is off is small, and the decay rate di / dt = −Vc2 / L1 of the current i flowing through the inductor L1 is slow. As a result, the time until the current i flowing through the inductor L1 becomes zero becomes long, and the OFF time of the switching element Q1 becomes long.

  Thus, according to the lighting device of the present embodiment, when the number n of LEDs in series increases, the ON time of the switching element Q1 automatically increases and the OFF time decreases, and when the number n of LEDs in series decreases, The on time of the switching element Q1 is automatically shortened and the off time is lengthened automatically. Accordingly, the constant current characteristic can be maintained regardless of the number n of LEDs in series.

  Here, the configuration of the control power supply circuit 10 will be described. In the present embodiment, the charging current is supplied from the positive electrode of the capacitor C1 to the positive electrode of the capacitor C3 via the dropper resistors R31 to R34, and as a more efficient power supply means, the secondary winding of the inductor L1 in a steady state. The configuration in which the capacitor C3 is charged from n2 is also used. A Zener diode ZD1 is connected in parallel as a constant voltage circuit that regulates the voltage of the capacitor C3. Further, the voltage of the capacitor C3 is stabilized by the three-terminal regulator REG to generate the control power supply voltage Vcc for the microcomputer 5.

  The voltage of the capacitor C1 is, for example, a voltage (about 140 V) near the peak value of the commercial AC power supply voltage (100 V, 50/60 Hz). A charging current is supplied from the capacitor C1 to the capacitor C3 for supplying the control power supply voltage Vcc via the step-down resistors R31 to R34.

  When the voltage of the capacitor C3 rises and the output voltage of the three-terminal regulator REG rises above the operable voltage of the microcomputer 5, the on / off operation of the switching element Q1 is started, and a high-frequency triangular wave current flows through the inductor L1. A high-frequency rectangular wave voltage is generated in the next winding n2.

  A voltage generated in the secondary winding n2 of the inductor L1 when the switching element Q1 is turned on causes a current to flow through the diode D10, the capacitor C10, and the resistor R10, and the capacitor C10 is charged. When the switching element Q1 is turned off, a voltage having a reverse polarity is generated in the secondary winding n2 of the inductor L1, and the capacitor C3 is charged via the diode D3 and the resistor R10 by a voltage obtained by adding this voltage and the charging voltage of the capacitor C10. Current flows. As a result, the voltage of the capacitor C3 tries to rise further. However, since a constant voltage circuit composed of the Zener diode ZD1 is connected in parallel to the capacitor C3, the voltage of the capacitor C3 is clamped by the constant voltage circuit. It is regulated by the Zener voltage of ZD1. In addition, a highly accurate control power supply voltage Vcc suitable for the operation of the microcomputer 5 is generated by the three-terminal regulator REG.

  The capacitor C4 connected in parallel with the capacitor C3 is a small-capacitance capacitor for bypassing the high-frequency component of the charging current via the diode D3.

  Next, the control operation of the control microcomputer 5 will be described with reference to the flowchart of FIG. When the prescribed power supply voltage Vcc is supplied to the control microcomputer 5, the operation starts from step # 1 in FIG.

In # 1, initialization processing is executed and various registers and the like are initialized.
In # 2, the binary output terminal P1 is set to the Low level. At this time, the switching element Q1 is turned on when the output of the gate driver circuit becomes a high level.

  In # 3, the voltage across the current detection resistor R1 is taken from the A / D conversion input terminal P0, and it is determined whether or not the current detection value exceeds a predetermined value Ip. If the current detection value does not exceed the predetermined value Ip, step # 3 is repeated until the current detection value exceeds the predetermined value Ip.

  In # 4, the binary output terminal P1 is set to the high level. At this time, when the output of the gate driver circuit becomes a low level, the switching element Q1 is turned off.

  In steps # 5 and # 6, a flow as shown in FIG. 4 described later is executed to read the dimming signal output from the dimming circuit 6 and the sensor signals output from the sensors 7a and 7b.

  In # 7, the predetermined value Ip used for the determination in # 3 is reset based on the dimming signal and sensor signal read in # 5 and # 6.

  In # 8, the binary input terminal P2 is monitored, and if it is determined as High level, it is determined that the induced voltage of the secondary winding n2 is being generated, and Step # 8 is repeated. If it is determined as the Low level, it is determined that the induced voltage of the secondary winding n2 has disappeared, and the process returns to the step # 2. Thereafter, the same operation is repeated.

  Here, the signal reading process of # 5 and # 6 will be described. Since the control microcomputer 5 generally has a time measurement function, in steps # 5 and # 6, the time when the binary input ports P3 to P5 change state from the previous High level to the Low level is stored. When the time when the binary input ports P3 to P5 change from the Low level to the High level is acquired next time, the time difference is calculated, so that each of the binary input ports P3 to P5 is at the Low level. Can measure the length of the period. By the same method, the length of the period when the binary input ports P3 to P5 are at the high level can also be measured.

  While the microcomputer 5 is in the loop of step # 3 and step # 8 in FIG. 3, High / Low of the binary input ports P3 to P5 cannot be read, but the switching frequency of the switching element Q1 is several tens. Since the frequency is as high as kHz, steps # 5 and # 6 are frequently circulated every switching cycle, and it can be said that there is no particular problem in reading a low-frequency rectangular wave voltage signal. In the first place, temperature information and dimming information are not urgent information that does not allow any control delay. Therefore, by averaging the measured values for a plurality of periods of a low-frequency rectangular wave voltage signal, The Low period can be detected with an accuracy that does not interfere with practical use. The averaging process may be performed using a general method, for example, a method in which the maximum value and the minimum value are excluded from the measurement values for the past five times and the remaining simple average is obtained.

  In addition, the reading process of all the binary input ports P3 to P5 may be executed sequentially between step # 3 and step # 8, but this signal reading process is not a highly urgent process. You may make it read sequentially in the separate OFF period of the switching element Q1.

  FIG. 4 illustrates a signal reading process flow. Here, the process of reading the sensor signal output from the sensor 7a from the binary input terminal P4 will be described, but the same applies to the other binary input terminals P3 and P5.

In # 11, the current state of the binary input terminal P4 is acquired. The state of the binary input terminal P4 is determined to be either High or Low.
In # 12, the previous state of the binary input terminal P4 is read.

  In # 13, the current state of the binary input terminal P4 acquired in # 11 is compared with the previous state of the binary input terminal P4 read in # 12, and it is determined whether or not they match. If they match, this means that the state of the binary input terminal P4 has not changed this time, and the process is terminated without doing anything. If it is determined that there is a mismatch, it means that the state of the binary input terminal P4 has changed this time, and the process proceeds to # 14.

  In # 14, the current time is acquired using the time measuring function of the microcomputer 5. Since the acquired current time is the time when the state of the binary input terminal P4 is changed this time, if the time difference from the time (starting time) at which the state of the binary input terminal P4 changed before is calculated, the binary time is obtained. The time when the state of the input terminal P4 is at the high level or the time when it is at the low level can be calculated.

  In # 15, the time difference between the time when the state of the binary input terminal P4 has changed before (the start time previously stored in # 16) and the current time acquired in # 14 is calculated. After the calculation is performed, the previous start time becomes unnecessary, so the current time acquired in # 14 is overwritten and stored as the start time for new time measurement (# 16).

  In # 17, the current port state (high level or low level) of the binary input terminal P4 is stored. Specifically, the current port state acquired in # 11 is stored. This information is read as the previous port state when the step # 12 is executed next time.

  In # 18, it is determined whether or not the current port state is the high level. If it is the High level, the process proceeds to # 19, the time difference calculated in # 15 is stored as the length of the latest Low period, and the past several Low periods and the latest Low period are averaged in # 20. . If the current port state is Low level in # 18, the process proceeds to # 21, the time difference calculated in # 15 is stored as the length of the latest High period, and the past several High periods are stored in # 22. Average the latest High period.

  The dimming signal output from the dimming circuit 6 is not limited. For example, a rectangular wave voltage signal of 1 kHz may be used, or a rectangular shape of 100 Hz or 120 Hz obtained by shaping a phase-controlled AC voltage. A wave voltage signal may be used.

  For example, when a 1 kHz duty signal is used as the dimming signal, the binary input port P5 of the microcomputer 5 determines whether the dimming signal is high level or low level. For example, when the dimming signal is high level, a predetermined value is obtained. The value Ip may be set to the minimum value, and the predetermined value Ip may be set to the maximum value when the dimming signal is at the low level. By controlling in this way, the light output is controlled to increase or decrease in proportion to the period during which the dimming signal is at the low level. As another control mode, the microcomputer 5 measures the ratio between the period when the dimming signal is at the high level and the period when the dimming signal is at the low level, and sets a predetermined value Ip according to the ratio. You may do it.

  When a signal such as DALI or DMX512 is used as the dimming signal, control according to each protocol may be performed.

  The configuration of the temperature sensor 7a is not limited. For example, an oscillation circuit whose oscillation state changes with temperature may be used. As an example, as shown in FIG. 2A, a Schmitt inverter G5 and a CR circuit for setting a time constant are combined to form a low-frequency astable oscillation circuit, and the capacitor Ct for setting the time constant is charged or discharged. If a temperature-sensitive resistance element such as a PTC (positive temperature characteristic) or NTC (negative temperature characteristic) thermistor is used for all or part of the resistor Rt, the oscillation state (oscillation cycle, on period, off) depends on the environmental temperature. Square wave voltage signals with different periods can be generated. By reading the rectangular wave voltage signal at the binary input port P4 of the microcomputer 5, the external temperature can be easily detected.

  Although the configuration of the color sensor 7b is not limited, for example, a plurality of photoconductive elements such as photodiodes, phototransistors, or CdS are provided, and color filters having different color temperatures are attached to the respective light receiving surfaces. What is necessary is just to comprise so that the ratio of a light reception output can be detected. As an example, as shown in FIG. 2B, a Schmitt inverter G6 and a CR circuit for setting a time constant are combined to form a low-frequency astable oscillation circuit, and a resistor that charges and discharges the capacitor C6 for setting the time constant. If a cold color filter FL1 is attached to the phototransistor PT1 connected in series with R6, and a warm color filter FL2 is attached to the phototransistor PT2, an unstable oscillation is generated according to the light intensity ratio of the cold color and the warm color. Since the ratio of the charge time constant and the discharge time constant of the capacitor C6 for setting the circuit time constant changes, rectangular wave voltage signals having different duty ratios are generated in accordance with the ratio of the cold color light reception intensity and the warm color light reception intensity. it can. By reading the rectangular wave voltage signal through the binary input port P3 of the microcomputer 5, the color temperature can be easily detected.

  Next, control that reflects the temperature information detected by the temperature sensor 7a and the color temperature information detected by the color sensor 7b will be exemplified.

  When the environmental temperature detected by the temperature sensor 7a is high, the conversion efficiency of the semiconductor light emitting element 4 is generally lowered and the light output is lowered. Therefore, the predetermined value Ip is set so as to compensate for the reduced light output. Reset higher. Conversely, when the environmental temperature is low, the predetermined value Ip is reset to a lower value.

  When a white light emitting diode is used as the semiconductor light emitting element 4, white is realized by combining phosphors that convert the light output of the blue light emitting diode to yellow, so that when the drive current increases, the blue temperature is high. When the driving current is reduced, a yellowish white light emission color having a low color temperature is obtained. The color temperature can be corrected using this characteristic.

  For example, when the color temperature detected by the color temperature sensor 7b is low, the average value of the drive current is increased by setting the predetermined value Ip higher to increase the color temperature of the emitted color. On the other hand, when the detected color temperature is high, the average value of the drive current is decreased by setting the predetermined value Ip lower, thereby lowering the color temperature of the emitted color. However, when this control is performed, the output capacitor C2 is omitted to enable intermittent lighting so that the overall light output does not change due to the color temperature control, and the chopper operation is intermittently performed as the predetermined value Ip increases. It is good to control to extend the period to stop.

  The types of the sensors 7a and 7b and the contents of the control are not limited. In short, the sensor state is read during the OFF period of the switching element Q1, and the ON period of the subsequent switching element Q1 is terminated. Anything that is reflected in the control of the value Ip is included in the scope of the present embodiment.

(Embodiment 2)
FIG. 5 is a circuit diagram of Embodiment 2 of the present invention. In this embodiment, a gate driver circuit is built in the output stage of the binary output terminal P1. The A / D conversion input terminal P0 of the microcomputer 5 is also used as a zero cross detection terminal.

  In the first embodiment, a gate driver circuit (parallel circuit of inverters G1 to G4) for driving a MOSFET is added to the output of the one-chip microcomputer 5. However, a binary output terminal P1 such as a totem pole output circuit is used. If an output circuit having a high driving capability is used, the MOSFET can be directly driven, and the circuit configuration can be simplified.

  In the first embodiment, the binary input terminal P2 is used to detect the disappearance of the voltage induced in the secondary winding n2. In the present embodiment, a diode is connected to the A / D conversion input terminal P0. By connecting an OR circuit composed of D4 and D5, the voltage across the current detection resistor R1 is detected during the ON period of the switching element Q1, and the induced voltage of the secondary winding n2 is detected during the OFF period of the switching element Q1. It is configured to do.

  That is, the timing at which the detection value of the switching current is obtained in the current detection resistor R1 is only the on period of the switching element Q1, and the detection value of the switching current is not generated in the current detection resistor R1 in the off period of the switching element Q1. On the other hand, it is only necessary to detect the zero cross of the regenerative current by monitoring the induced voltage of the secondary winding n2 due to the regenerative current flowing from the inductor L1 via the regenerative diode D1 only in the off period of the switching element Q1. is there. Therefore, the binary input terminal P2 can be used for another purpose by using the A / D conversion input terminal P0 also as the zero cross detection terminal during the OFF period of the switching element Q1.

  Even if the diode D4 is omitted, the operation is not hindered, but the diode D5 is necessary. The diode D5 is cut off when the switching element Q1 is turned on, and is provided to disconnect the secondary winding n2 from the A / D conversion input terminal P0.

  In the present embodiment, the added sensor 7c is not particularly limited, but may be a sensor that detects a secular change, for example. As a specific example, in the astable oscillation circuit shown in FIG. 2 (a), if the capacitor Ct is an electrolytic capacitor having a shorter life than the film capacitor and the resistor Rt is a fixed resistor, the oscillation period is long at the beginning of the life. At the end, the oscillation period is shortened due to capacity loss. By detecting the change in the oscillation cycle and controlling to increase the predetermined value Ip that is the peak value of the switching current at the end of the lifetime, wasteful power consumption is suppressed at the beginning of the lifetime, and brightness is reached at the end of the lifetime. Can be prevented.

  In addition, a human sensor or a brightness sensor may be added. If these sensors are used, for example, the semiconductor light-emitting element 4 is turned on only when the surroundings are dark and a person is detected. It is also possible to realize power saving control that achieves the dimming output set in 6.

  In the first and second embodiments, the timing of voltage disappearance of the secondary winding n2 of the inductor L1 is detected to detect the timing at which the current flowing through the inductor L1 becomes substantially zero. The specific means may be changed as long as it is a means capable of detecting the timing at which the regenerative current disappears, such as detecting an increase in the reverse voltage of the diode D1 or detecting a drop in the voltage across the switching element Q1. Absent.

(Embodiment 3)
In the first and second embodiments, the circuit example in which the switching element Q1 of the step-down chopper circuit 3 is disposed on the low potential side has been described. However, as illustrated in FIG. 6 or FIG. 7A, the switching of the step-down chopper circuit 3a is performed. It goes without saying that the present invention can be applied even when the element Q1 is arranged on the high potential side.

  When the switching element Q1 of the step-down chopper circuit 3a is arranged on the high potential side, a high side driver 8 is required as shown in FIG. 6, but the switching element Q1 is turned on at both ends of the current detection resistor R1. When the voltage gradually increases and reaches a predetermined value, a gradually decreasing triangular wave voltage is obtained. Therefore, there is an advantage that a current peak detection function and a zero cross detection function can be realized by one A / D conversion input terminal P0.

(Embodiment 4)
FIG. 7 shows configuration examples of various switching power supply circuits to which the present invention can be applied. The present invention may be applied not only to the step-down chopper circuit 3a as shown in FIG. 7 (a) but also to various switching power supply circuits as shown in FIGS. 7 (b) to 7 (d). FIG. 7B shows an example of the step-up chopper circuit 3b, FIG. 7C shows an example of the flyback converter circuit 3c, and FIG. 7D shows an example of the step-up / step-down chopper circuit 3d.

  In particular, when the configuration of the switching power supply circuit is any one of a step-down chopper circuit, a flyback converter circuit, and a buck-boost chopper circuit, the ON period of the switching element Q1 varies depending on the input voltage, but the switching element Q1 is turned off. Since the period has little variation due to the unique property that the terminal voltage of the semiconductor light emitting element 4 is substantially constant, other processing (reading of an external signal, etc.) can be executed using the time vacant. Further, even if other processes (# 5 to # 7) that have started executing in the idle time are prolonged, the timing of the zero cross detection (# 8) is only slightly delayed, and the switching element Q1 is turned off. So there is no risk of overstressing the circuit.

(Embodiment 5)
FIG. 8 shows a schematic configuration of an LED lighting fixture with a separate power source using the LED lighting device of the present invention. In this separate power supply type LED lighting fixture, the dimming / lighting device 1 as a power supply unit is built in a case different from the casing 42 of the LED module 40. By doing so, the LED module 40 can be thinned, and the dimming / lighting device 1 as a separate power supply unit can be installed regardless of the location.

  The instrument housing 42 is made of a metal cylinder that is open at the lower end, and the lower end open portion is covered with a light diffusion plate 43. The LED module 40 is disposed so as to face the light diffusion plate 43. Reference numeral 41 denotes an LED mounting board on which the LEDs 4a to 4d of the LED module 40 are mounted. The appliance housing 42 is embedded in the ceiling 100, and is wired from the dimming / lighting device 1 as a power supply unit arranged behind the ceiling via a lead wire 44 and a connector 45.

  A circuit as described in the first to fourth embodiments is accommodated in the dimming / lighting device 1 as a power supply unit. A series circuit (LED module 40) of the LEDs 4a to 4d corresponds to the semiconductor light emitting element 4 described above.

  In the present embodiment, the dimming / lighting device 1 as a power supply unit is exemplified as a separate power supply type LED lighting device housed in a housing different from the LED module 40, but the power supply unit is mounted in the same housing as the LED module 40. You may use the lighting device of this invention for the stored power supply integrated LED lighting fixture.

  The lighting device of the present invention is not limited to a lighting fixture, and may be used as various light sources, for example, a backlight of a liquid crystal display, a light source of a copying machine, a scanner, a projector, or the like.

  In the description of each embodiment described above, a light emitting diode is exemplified as the semiconductor light emitting element 4, but the present invention is not limited to this, and may be, for example, an organic EL element or a semiconductor laser element.

Q1 Switching element L1 Inductor D1 Diode R1 Current detection resistor 4 Semiconductor light emitting element 5 Control circuit (1-chip microcomputer)

Claims (6)

A switching element connected in series to a DC power source and controlled to be turned on and off at a high frequency; an inductance element connected in series with the switching element and through which a current flows from the DC power source when the switching element is turned on; and when the switching element is turned on A regenerative diode that discharges energy stored in the inductance element to the semiconductor light emitting element when the switching element is off; current detection means for detecting a current flowing through the switching element; and a current value detected by the current detection means is predetermined. In a lighting device for a semiconductor light-emitting element, comprising a control means for turning off the switching element when reaching a value and turning on the switching element when energy emission of the inductance element is completed,
The control means includes an A / D conversion input terminal that reads a current value detected by the current detection means, a zero-cross detection terminal that detects completion of energy emission of the inductance element, and an output that controls on / off of the switching element. A one-chip microcomputer equipped with a terminal ,
Lighting device of the semiconductor light emitting element characterized and this was also used the zero-cross detection terminal and the A / D conversion input terminal. The one-chip microcomputer includes an external signal input terminal for inputting an external signal including a dimming signal or a sensor signal, and an external signal read processing unit that reads the external signal while the switching element is off. 2. The lighting device for a semiconductor light emitting element according to claim 1, further comprising a peak current setting processing unit for resetting the predetermined value in accordance with an external signal. The external signal is a rectangular wave signal having a frequency sufficiently lower than the on / off frequency of the switching element, and the external signal reading processing unit changes the state of the rectangular wave signal for each off period of the switching element. 3. The lighting device for a semiconductor light emitting element according to claim 2, wherein an on period or an off period of the rectangular wave signal is measured by observation. 4. The semiconductor light emitting device according to claim 3, wherein the external signal reading processing unit includes an averaging processing unit that averages an on period or an off period of the measured rectangular wave signal over a plurality of periods of the low frequency. Element lighting device. The one-chip microcomputer includes a plurality of the external signal input terminals, and the external signal read processing unit sequentially reads external signals from the external signal input terminals during different off periods of the switching elements. The lighting device for a semiconductor light emitting element according to claim 2. A lighting device comprising the lighting device for a semiconductor light-emitting element according to claim 1 and a semiconductor light-emitting element to which a current is supplied from the lighting device.

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