WO2007074866A1 - Circuit d'attaque de dispositif d'émission de lumière - Google Patents

Circuit d'attaque de dispositif d'émission de lumière Download PDF

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Publication number
WO2007074866A1
WO2007074866A1 PCT/JP2006/326052 JP2006326052W WO2007074866A1 WO 2007074866 A1 WO2007074866 A1 WO 2007074866A1 JP 2006326052 W JP2006326052 W JP 2006326052W WO 2007074866 A1 WO2007074866 A1 WO 2007074866A1
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Prior art keywords
voltage
constant current
control signal
current source
circuit
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PCT/JP2006/326052
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English (en)
Japanese (ja)
Inventor
Masashi Fukuda
Kengo Takahama
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Sharp Kabushiki Kaisha
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Publication of WO2007074866A1 publication Critical patent/WO2007074866A1/fr

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Classifications

    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
    • H05B45/30—Driver circuits
    • H05B45/37—Converter circuits
    • H05B45/3725—Switched mode power supply [SMPS]
    • H05B45/38—Switched mode power supply [SMPS] using boost topology
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
    • H05B45/30—Driver circuits
    • H05B45/395—Linear regulators
    • H05B45/397—Current mirror circuits
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
    • Y02B20/00—Energy efficient lighting technologies, e.g. halogen lamps or gas discharge lamps
    • Y02B20/30—Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED]

Definitions

  • the present invention relates to a light emitting element driving circuit that drives a light emitting element at a constant current.
  • a light emitting diode (hereinafter abbreviated as LED) emits light when a voltage higher than the forward voltage Vf is applied.
  • the LED forward voltage Vf has the property that it increases with decreasing temperature and decreases with increasing temperature. Therefore, as a method of causing the LED to emit light correctly even when the forward voltage Vf changes with temperature, a constant current source has been conventionally connected in series with the LED to control the amount of current flowing through the LED. Methods are known (for example, Patent Documents 1 to 3).
  • FIG. 10 is a diagram showing a configuration of a conventional LED drive circuit.
  • the LED drive circuit 81 shown in FIG. 10 drives four LEDs connected in series (hereinafter referred to as LED array 87) at a constant current. More specifically, the constant current source 82 is connected to the LED array 87 in series.
  • the booster circuit 83 boosts the input voltage Vin and supplies the obtained boosted voltage Vb to the LED array 87 and the constant current source 82.
  • the resistors 84a and 84b are connected in series and divide the boosted voltage Vb.
  • the comparator 85 compares the divided voltage obtained by the resistors 84a and 84b with the reference voltage Vr provided by the reference power supply 86, and outputs a boost control signal 90 indicating the comparison result.
  • the booster circuit 83 changes the level of the boost voltage Vb based on the boost control signal 90.
  • Vb VrX (Rl + R2) / R2... hi)
  • Vb Vi + Vf X 4--(2)
  • the boost voltage Vb is determined so as to satisfy the following equation (3) derived from the above equation (2) and Vi> Vmin.
  • Patent Document 4 discloses a charge pump type booster circuit capable of arbitrarily setting an output voltage.
  • Patent Document 1 Japanese Patent Laid-Open No. 2002-359090
  • Patent Document 2 Japanese Unexamined Patent Publication No. 2003-152224
  • Patent Document 3 Japanese Unexamined Patent Publication No. 2005-11895
  • Patent Document 4 Japanese Unexamined Patent Publication No. 2000-166220
  • FIG. 11 is a graph showing the temperature characteristics of the boosted voltage Vb in the LED drive circuit 81. As shown in FIG. Figure 11 shows the boost voltage Vb when the operating temperature range is 20 ° C up to 85 ° C, and four times the LED forward voltage Vf (Vf X
  • the voltage Vi across the constant current source 82 is minimized at 20 ° C. Therefore, when designing the LED drive circuit 81, the boosted voltage Vb is determined so as to satisfy Vi ( ⁇ 20 ° C.)> Vmin.
  • the constant current source 82 operates when the minimum operating voltage Vmin is applied to both ends. Therefore, the power consumption in the constant current source 82 can be suppressed to (VminX Id) ideally.
  • the above formula (4) is established for power consumption Pi (25 ° C) at room temperature, and the constant current source 82 consumes more power than necessary at room temperature. Since the above equation (4) holds even at room temperature, it can be said that the constant current source 82 always consumes more power than necessary within the operating temperature range.
  • an object of the present invention is to provide a light emitting element driving circuit that drives a light emitting element at a constant current stably and with low power consumption.
  • a first aspect of the present invention is a light emitting element driving circuit for driving a light emitting element at a constant current, a constant current source connected in series to the light emitting element to be driven,
  • a booster circuit that boosts an input voltage and applies the obtained boosted voltage to the light emitting element and the constant current source
  • a comparison circuit that compares the voltage detected by the detection circuit with a reference voltage and outputs a boost control signal indicating a comparison result
  • the booster circuit changes the level of the boosted voltage based on the boost control signal.
  • a second aspect of the present invention is the first aspect of the present invention.
  • the step-up circuit is a chitotsuba type step-up circuit including a coil and a switch that switches a flow of current that has passed through the coil.
  • the switch is controlled by a control signal whose duty ratio changes according to the boost control signal.
  • a third aspect of the present invention is the first aspect of the present invention.
  • the booster circuit is a charge pump booster circuit including a capacitor and a switch for switching a connection state of the capacitor,
  • the switch has a control signal whose duty ratio changes according to the boost control signal. It is controlled by.
  • a fourth aspect of the present invention provides, in the first aspect of the present invention,
  • the boost control signal is an analog signal indicating a difference between a voltage detected by the detection circuit and the reference voltage.
  • the light emitting element driving circuit detects the voltage across the constant current source and compares the detected voltage with the reference voltage so that the voltage across the constant current source becomes the reference voltage.
  • the boosted voltage is generated while performing feedback control so as to match the above. Therefore, even if the characteristics of the light emitting element (for example, the forward voltage Vf of the LED) fluctuate due to the operating temperature or the variation between elements, the voltage across the constant current source is kept constant, and the light emitting element is stably stabilized. Can be driven. Also, even if the operating temperature changes, keeping the voltage across the constant current source at a low level (for example, a level close to the minimum operating voltage) prevents the constant current source from consuming more power than necessary. can do. In this manner, the light emitting element can be driven with a constant current stably and with low power consumption.
  • the characteristics of the light emitting element for example, the forward voltage Vf of the LED
  • the second aspect of the present invention it is possible to obtain a light-emitting element driving circuit that drives a light-emitting element at a constant current stably and with low power consumption, using a chiyotsuba booster circuit.
  • the third aspect of the present invention it is possible to obtain a light emitting element driving circuit that drives a light emitting element at a constant current stably and with low power consumption using a charge pump booster circuit.
  • the voltage across the constant current source can be matched with the reference voltage with high accuracy by controlling the booster circuit using the analog boost control signal.
  • FIG. 1 is a diagram showing a configuration of an LED drive circuit according to first and second embodiments of the present invention.
  • FIG. 2 is a circuit diagram of a constant current source of the LED drive circuit shown in FIG.
  • FIG. 3 is a circuit diagram of a booster circuit of the LED drive circuit according to the first embodiment of the present invention.
  • FIG. 4A is a signal waveform diagram showing changes in input / output signals when the voltage of the boost control signal is high in the booster circuit shown in FIG.
  • FIG. 4B is a signal waveform diagram showing changes in input / output signals when the voltage of the boost control signal is low in the booster circuit shown in FIG.
  • FIG. 5 is a graph showing the temperature characteristics of the boosted voltage of the LED drive circuit shown in FIG.
  • FIG. 6 is a circuit diagram of a booster circuit of an LED drive circuit according to a second embodiment of the present invention.
  • FIG. 7 is a signal waveform diagram showing a change in the signal of the booster circuit shown in FIG.
  • FIG. 8 is a diagram showing another usage pattern of the LED drive circuit shown in FIG.
  • FIG. 9 is a graph showing the temperature characteristics of the boosted voltage when used in the form shown in FIG.
  • FIG. 10 is a diagram showing a configuration of a conventional LED drive circuit.
  • FIG. 11 is a graph showing the temperature characteristics of the boosted voltage of the LED drive circuit shown in FIG.
  • FIG. 1 is a diagram showing a configuration of an LED drive circuit according to the first embodiment of the present invention.
  • the LED drive circuit 1 shown in FIG. 1 includes a constant current source 2, a booster circuit 3, a differential amplifier 4, 5, and a reference power supply 6, and includes four LEDs connected in series (LED array 7). Is driven at a constant current.
  • the input voltage Vin is supplied to the LED drive circuit 1.
  • the booster circuit 3 boosts the input voltage Vin and outputs the obtained boosted voltage Vb.
  • the booster circuit 3 changes the level of the boost voltage Vb based on the boost control signal 10.
  • the booster circuit 3 increases the boost voltage Vb when the voltage of the boost control signal 10 is equal to or higher than a predetermined value, and decreases the boost voltage Vb otherwise (details will be described later).
  • the output terminal of the booster circuit 3 is connected to the current input terminal of the constant current source 2.
  • the current output terminal of the constant current source 2 is connected to the anode side terminal of the LED array 7, and the power sword side terminal of the LED array 7 is grounded. Thereby, each LED included in the LED array 7 is driven by the constant current source 2 at a constant current.
  • the differential amplifier 4 functions as a detection circuit that detects the voltage across the constant current source 2. More specifically, the positive input terminal of the differential amplifier 4 is connected to the current input terminal of the constant current source 2, and the negative input terminal of the differential amplifier 4 is connected to the current output terminal of the constant current source 2. Yes.
  • the differential amplifier 4 amplifies and outputs a potential difference (a voltage between both ends) between the current input terminal and the current output terminal of the constant current source 2.
  • the differential amplifier 5 functions as a comparison circuit that compares the voltage detected by the differential amplifier 4 with a reference voltage. More specifically, the negative input terminal of the differential amplifier 5 is connected to the output terminal of the differential amplifier 4, and the reference power supply 6 is connected to the positive input terminal of the differential amplifier 5. It is. The reference power supply 6 supplies a reference voltage E1.
  • the differential amplifier 5 amplifies the difference between the output voltage of the differential amplifier 4 and the reference voltage E1, and outputs it as an analog boost control signal 10.
  • the voltage of the boost control signal 10 is high when the reference voltage E1 is higher than the output voltage of the differential amplifier 4, and is low otherwise.
  • the boost control signal 10 shows the result of comparing the output voltage of the differential amplifier 4 with the reference voltage E1.
  • the LED drive circuit 1 detects the voltage across the constant current source 2 and compares the detected voltage with the reference voltage E1, so that the voltage Vi across the constant current source 2 becomes the reference voltage E1. While performing feedback control to match, boost voltage Vb is generated.
  • FIG. 2 is a circuit diagram of the constant current source 2.
  • the constant current source 2 shown in FIG. 2 includes P-channel MOS transistors 21 to 23, N-channel MOS transistors 24 and 25, a reference power supply 26, and a resistor 27.
  • the constant current source 2 has terminals 28a to 28c.
  • the terminal 28a is supplied with a boosted voltage Vb, the terminal 28b is connected to the negative input terminal of the differential amplifier 4, and the terminal 28c is connected to the anode side terminal of the LED array 7.
  • the sources of the P-channel MOS transistors 21 to 23, 25 are connected to the terminal 28a, and the drains of the P-channel MOS transistors 21, 22 are connected to both the terminals 28b, 28c. .
  • the gates of P-channel MOS transistors 21 to 23 and the drain of P-channel MOS transistor 23 are connected to the drain of N-channel MOS transistor 24.
  • the source of the N-channel MOS transistor 24 is connected to the reference power supply 26, and the source of the N-channel MOS transistor 25 and the gates of the N-channel MOS transistors 24 and 25 are connected to the resistor 27.
  • N-channel MOS transistors 24 and 25 constitute a current mirror circuit.
  • the reference voltage supplied by the reference power supply 26 is E and the resistance value of the resistor 27 is R
  • P-channel MOS transistors 21 and 23 form a current mirror circuit, and similarly, P-channel MOS transistors 22 and 23 also form a current mirror circuit.
  • the current Ic flows through the source of the P-channel MOS transistor 23.
  • the constant current source 2 outputs a current (I c X 2) twice the current Ic to the LED array 7 via the terminal 28c.
  • the potential difference between terminals 28a and 28b matches the voltage drop across P-channel MOS transistors 21 and 22.
  • FIG. 3 is a circuit diagram of the booster circuit 3.
  • the booster circuit 3a shown in FIG. 3 includes constant current sources 31, 32, a switch 33, a capacitor 34, a hysteresis comparator 35, a reference power supply 36, a comparator 37, an N-channel MOS transistor 38, a coil 39, a diode 40, and a capacitor 41. Is a Chietsuba type booster circuit. Further, the booster circuit 3a has terminals 42a to 42c. An input voltage Vin is applied to the terminal 42a, a boost control signal 10 is applied to the terminal 42b, and a boost voltage Vb is output from the terminal 42c.
  • the input voltage Vin is applied to the current input terminal of the constant current source 31 via the terminal 42a.
  • the current output terminal of the constant current source 31 is connected to the “a” contact of the switch 33.
  • the current input terminal of the constant current source 32 is connected to the b contact of the switch 33, and the current output terminal of the constant current source 32 is grounded.
  • the output contact of the switch 33 is connected to one electrode of the capacitor 34, the plus side input terminal of the hysteresis comparator 35, and the minus side input terminal of the comparator 37.
  • the other terminal of the capacitor 34 is grounded.
  • the negative input terminal of the hysteresis comparator 35 is connected to a reference power supply 36 that supplies a reference voltage E2.
  • the hysteresis comparator 35 is a comparison circuit having hysteresis characteristics with a hysteresis width Vh.
  • the hysteresis comparator 35 outputs a high level signal when the voltage applied to the positive input terminal (hereinafter referred to as voltage Vp) exceeds (E2 + VhZ2), and when the voltage Vp falls below (E2 ⁇ VhZ2), the hysteresis comparator 35 outputs a low level signal. A level signal is output.
  • the boost control signal 10 is given to the positive side input terminal of the comparator 37 via the terminal 42b.
  • the comparator 37 compares the voltage Vp applied to the negative input terminal with the voltage of the boost control signal 10 applied to the positive input terminal.
  • the output terminal of the comparator 37 is connected to the gate of the N-channel MOS transistor 38.
  • the source of the N-channel MOS transistor 38 is grounded, and the drain of the N-channel MOS transistor 38 is connected to one end of the coil 39 and the anode of the diode 40.
  • the input voltage Vin is applied to the other end of the coil 39 via the terminal 42a.
  • the power sword of the diode 40 is connected to one electrode of the capacitor 41 and the terminal 42c. The other electrode of the capacitor 41 is grounded.
  • 4A and 4B are signal waveform diagrams showing changes in input / output signals in the booster circuit 3a.
  • 4A shows a signal change when the voltage of the boost control signal 10 is high
  • FIG. 4B shows a signal change when the voltage of the boost control signal 10 is low.
  • the negative input terminal of the comparator 37 is supplied with a voltage Vp that changes in a triangular waveform in a range from (E2 ⁇ VhZ2) to (E2 + VhZ2).
  • the boost control signal 10 at a certain level is applied to the positive input terminal of the comparator 37.
  • the comparator 37 outputs a high level signal when the voltage of the boost control signal 10 is equal to or higher than the voltage Vp, and outputs a low level signal otherwise. Therefore, the output signal of the comparator 37 is a signal having a certain duty ratio that changes between a high level and a low level.
  • the N-channel MOS transistor 38 While the output signal of the comparator 37 is at a high level, the N-channel MOS transistor 38 is turned on. During this time, the current passing through the coil 39 flows to the ground via the N-channel MOS transistor 38. When the output signal of the comparator 37 changes to low level, the N-channel MOS transistor 38 is turned off, and the current passing through the coil 39 is Flows into capacitor 41 via node 40. Thereby, the capacitor 41 is charged. In this way, the booster circuit 3a boosts the input voltage Vin by switching the current flow that has passed through the coil 39 using the N-channel MOS transistor 38.
  • the booster circuit 3a changes the level of the boost voltage Vb based on the boost control signal 10 by the following method.
  • the voltage of the boost control signal 10 is high (FIG. 4A)
  • the output signal from the comparator 37 has a long and low period.
  • the voltage of the boost control signal 10 is low (FIG. 4B)
  • the period during which the voltage of the boost control signal 10 is equal to or lower than the voltage Vp is long, so the low level period is long in the output signal of the comparator 37.
  • the duty ratio of the output signal of the comparator 37 changes according to the boost control signal 10.
  • the boosted voltage Vb increases when the charge accumulation amount of the capacitor 41 is large, and decreases when the charge accumulation amount of the capacitor 41 is small.
  • the amount of charge stored in the capacitor 41 increases as the period during which the N-channel MOS transistor 38 is on is longer (that is, as the period during which the output signal of the comparator 37 is at a high level is longer). Therefore, the boost voltage Vb increases when the voltage of the boost control signal 10 is high, because the charge storage amount of the capacitor 41 is large.
  • the charge storage amount of the capacitor 41 is small! / , Descend for.
  • the boost control signal 10 is controlled by controlling the N-channel MOS transistor 38 using the switch control signal whose duty ratio changes according to the boost control signal 10. Based on this, the level of the boost voltage Vb can be changed.
  • FIG. 5 is a diagram showing the temperature characteristics of the boosted voltage Vb in the LED drive circuit 1.
  • Figure 5 shows the step-up voltage Vb when the operating temperature range is ⁇ 20 ° C to 85 ° C, and four times the LED forward voltage Vf (V f X 4). The difference between the two graphs shown in FIG. 5 is equal to the voltage Vi across the constant current source 2.
  • the forward voltage Vf of an LED increases as the temperature decreases and decreases as the temperature increases.
  • the LED drive circuit 1 is designed so that the voltage Vi across the constant current source 2 matches the reference voltage E1. Perform feedback control. Therefore, even if the operating temperature changes, the voltage Vi across the constant current source 2 does not change and always matches the reference voltage E1.
  • the graph of the boosted voltage Vb is a graph obtained by translating the voltage (Vf X 4) graph vertically by the reference voltage E1.
  • the constant current source 2 does not consume more power than necessary.
  • the booster circuit 3 is controlled by using an analog boost control signal 10 indicating the difference between the voltage Vi across the constant current source 2 and the reference voltage E1, so the voltage Vi across the constant current source 2 is used as a reference.
  • the voltage E1 can be matched with high accuracy.
  • the LED drive circuit 1 detects the voltage Vi between both ends of the constant current source 2, and compares the detected voltage with the reference voltage E1, whereby both ends of the constant current source 2 are detected. While performing feedback control so that the voltage V i matches the reference voltage E1, the boost voltage Vb is generated. Therefore, even if the forward voltage Vf of the LED fluctuates due to the operating temperature and variations between elements, the voltage Vi across the constant current source 2 can always be kept constant, and the LED can be driven stably at a constant current. Even if the operating temperature changes, the constant current source 2 consumes more power than necessary by keeping the voltage Vi across the constant current source 2 at a low level (for example, a level close to the minimum operating voltage Vmin). Can be prevented. As described above, according to the LED driving circuit 1 according to the present embodiment, the LED can be driven with a constant current stably and with low power consumption.
  • the LED drive circuit according to the second embodiment of the present invention has the configuration shown in FIG. 1, and includes a booster circuit 3b shown in FIG. 6 instead of the booster circuit 3a shown in FIG.
  • a booster circuit 3b shown in FIG. 6 instead of the booster circuit 3a shown in FIG.
  • details of the booster circuit 3 b will be described, and description of points that are common to the first embodiment will be omitted.
  • FIG. 6 is a circuit diagram of the booster circuit 3 included in the LED drive circuit according to the second embodiment.
  • the booster circuit 3b shown in FIG. 6 is a charge pump type booster including a hysteresis comparator 51, a reference power supply 52, an AND gate 53, noters 54 and 55, switches SA1 to SA8, SB1 to SB5, and capacitors C1 to C5. Circuit.
  • the booster circuit 3b includes terminals 56a to 5 6c.
  • An input voltage Vin is applied to the terminal 56a
  • a boost control signal 10 is applied to the terminal 56b
  • a boost voltage Vb is output from the terminal 56c.
  • the boost voltage Vb is 5 times the input voltage Vin.
  • one electrode of the capacitor C1 is grounded via the switch SA1, and the other electrode is connected to the terminal 56a via the switch SA2.
  • a switch SB1 force is provided between the terminal 56a and one electrode of the capacitor C1 (the electrode on the side where the switch SA1 is connected).
  • a switch SB2 is provided between the other electrode of the capacitor C1 and one electrode of the capacitor C2 (the electrode on the side to which the switch SA3 is connected).
  • Switches SB3 and SB4 are provided in the same manner.
  • a switch SB5 force is provided between the other electrode of the capacitor C4 (the electrode on the side where the switch SA8 is connected) and the terminal 56c.
  • Capacitor C5 is provided between terminal 56c and ground.
  • the AND gate 53 is supplied with a clock signal CLK having a predetermined frequency.
  • the AND gate 53 outputs a logical product of the clock signal CLK and the output signal of the hysteresis comparator 51.
  • the nofer 54 outputs the output signal of the AND gate 53 in a non-inverted manner.
  • the output signal of the notch 54 is given to the control terminals of the switches SB1 to SB5.
  • the notifier 55 inverts the output signal of the AND gate 53.
  • the output signal of the buffer 55 is applied to the control terminals of the switches SA1 to SA8. Therefore, the switches SA1 to SA8 are turned on at the same time, and the switches SB1 to SB5 are turned on at the same time when the switches SA1 to SA8 are turned off (see FIG. 7).
  • the capacitor C5 is the sum of the input voltage Vin and the voltage charged in the capacitors C1 to C4, that is, the input Charged by a voltage 5 times the voltage Vin.
  • the potential difference between both electrodes of capacitor C5 is output as boosted voltage Vb.
  • the booster circuit 3b The input voltage Vin is boosted by controlling the switches SA1 to SA8 and the switches SB1 to SB5 alternately on and off, and switching the connection state of the capacitors C1 to C5.
  • the booster circuit 3b changes the level of the boost voltage Vb based on the boost control signal 10 by the following method. As shown in FIG. 6, the boost control signal 10 is given to the positive side input terminal of the hysteresis comparator 51 via the terminal 56b. The negative input terminal of the hysteresis comparator 51 is connected to the reference power supply 52 that supplies the reference voltage E3.
  • the hysteresis comparator 51 is a comparison circuit having hysteresis characteristics with a hysteresis width VH.
  • the hysteresis comparator 51 outputs a high level signal when the voltage of the boost control signal 10 becomes (E3 + VHZ 2) or more, and outputs a low level signal when the voltage of the boost control signal 10 becomes (E3 ⁇ VHZ 2) or less. Output.
  • the output signal of the NAND gate 53 changes at a predetermined frequency similarly to the clock signal CLK.
  • the charge pump circuit composed of the switches SA1 to SA8, SB1 to SB5 and the capacitors C1 to C5 performs a boosting operation, and the boosted voltage Vb rises.
  • the duty ratio of the output signal of the AND gate 53 is a value other than zero (for example, 50%).
  • the output signal of the AND gate 53 is fixed at the low level. Therefore, after the voltage of the boost control signal 10 becomes (E3 ⁇ VHZ2) or less, the charge pump circuit does not perform the boost operation and the boost voltage Vb drops. At this time, the duty ratio of the output signal of the AND gate 53 is 0%. As described above, the duty ratio of the output signal of the AND gate 53 changes according to the boost control signal 10.
  • the switches SA1 to SA8 and SB1 to SB5 are controlled by using the switch control signal whose duty ratio changes according to the boost control signal 10, thereby boosting the voltage. Based on the control signal 10, the level of the boost voltage Vb can be changed.
  • the LED drive circuit of this embodiment including the booster circuit 3b shown in FIG.
  • the LED can be driven with a constant current stably and with low power consumption.
  • the 1S LED drive circuit that has been described so far for the case where the LED drive circuit drives four LEDs may drive one or more arbitrary LEDs.
  • the LED driving circuit 1 may drive two LEDs connected in series (hereinafter referred to as LED array 8) as shown in FIG. Even in this case, the LED drive circuit 1 generates the boost voltage Vb while performing feedback control so that the voltage across the constant current source 2 matches the reference voltage E1.
  • FIG. 9 is a diagram showing temperature characteristics of the boosted voltage Vb when the LED array 8 is driven.
  • the following equation (5) is established among the boosted voltage Vb, the voltage Vi across the constant current source 2, and the forward voltage Vf of each LED.
  • the graph of the boosted voltage Vb is a graph obtained by translating the voltage (Vf X 2) graph by the reference voltage E1 in the vertical direction.
  • Vb Vi + Vf X 2--(5)
  • the same LED driving circuit 1 can be used when driving four LEDs and when driving two LEDs.
  • the same LED driving circuit 1 can be used to drive n or less LEDs as long as the boosting circuit 3 can generate a boosted voltage Vb that satisfies the following equation (6).
  • Vb Vi + Vf X n ⁇ ' ⁇ (6)
  • the LED driving circuit for driving the LED has been described as an example of the light emitting element driving circuit so far, the electoric luminescence element (EL element) is driven by the same method in the same way. A light emitting element driving circuit can be obtained. These EL element drive circuit and filament ball drive circuit have the same effect as the LED drive circuit.
  • the light-emitting element driving circuit provides a constant current drive for a light-emitting element stably and with low power consumption. Since it has the effect of being able to move, it can be used for light emitting element drive circuits that drive LEDs, EL elements, and filament balls.

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Abstract

L'invention concerne une source (2) de courant constant qui est reliée en série à un réseau (7) de diodes LED à attaquer. Un circuit de préamplificateur (3) préamplifie une tension d'entrée (Vin) et applique la tension obtenue de démarrage (Vb) sur le réseau (7) de diodes LED et sur la source (2) de courant constant. Un amplificateur différentiel (4) détecte les tensions aux deux extrémités de la source (2) de courant constant, et un amplificateur différentiel (5) compare la tension détectée à une tension de référence (E1). Le circuit de préamplificateur (3) modifie le niveau de la tension de démarrage (Vb) en fonction du signal analogique de commande de démarrage (10) fourni en sortie de l'amplificateur différentiel (5). Dans un circuit de préamplificateur de type à découpage (3a), le commutateur qui commute la circulation du courant ayant traversé une bobine est commandé par un signal de commande, dont le rapport cyclique varie en fonction du signal de commande de démarrage (10). Dans un circuit de préamplificateur du type à pompe à charge (3b), le commutateur qui commute les états de connexion d'un condensateur est également commandé par le signal de commande. Ceci permet d'attaquer de manière stable un dispositif d'émission de lumière grâce à un courant constant avec une consommation de faible puissance.
PCT/JP2006/326052 2005-12-28 2006-12-27 Circuit d'attaque de dispositif d'émission de lumière WO2007074866A1 (fr)

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JP2005-379031 2005-12-28
JP2005379031 2005-12-28

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Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2010539707A (ja) * 2007-09-14 2010-12-16 イクシス コーポレーション プログラム可能なｌｅｄ駆動装置
WO2010130588A3 (fr) * 2009-05-11 2011-01-06 Austriamicrosystems Ag Convertisseur de tension et procédé de conversion de tension
JP2011023750A (ja) * 2010-10-26 2011-02-03 Panasonic Corp 発光素子駆動装置および発光装置
CN103200730A (zh) * 2012-01-06 2013-07-10 苏州璨宇光学有限公司 电流控制电路及其相应的发光二极管模块
CN103533695A (zh) * 2012-07-03 2014-01-22 成都市宏山科技有限公司 Led恒流驱动系统
CN103533699A (zh) * 2012-07-03 2014-01-22 成都市宏山科技有限公司 用于系统测试中发光二极管的恒流驱动电路
CN104735863A (zh) * 2013-12-24 2015-06-24 理察·蓝德立·葛瑞 在低输入电压操作下适用于直接式led驱动器的防闪烁电路
WO2017117723A1 (fr) * 2016-01-05 2017-07-13 Tridonic Gmbh & Co. Kg Pompe de charge à deux étages pour excitateurs de led
AT519927A1 (de) * 2017-04-26 2018-11-15 Zkw Group Gmbh Speiseschaltung zur Versorgung von LEDs aus einer primären Gleichspannung
AT520880A1 (de) * 2017-04-26 2019-08-15 Zkw Group Gmbh Speiseschaltung zur Versorgung von LEDs aus einer primären Gleichspannung
WO2021008384A1 (fr) * 2019-07-17 2021-01-21 深圳市洲明科技股份有限公司 Système de réglage de rétroaction d'alimentation électrique et écran de visualisation

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JP2004022929A (ja) * 2002-06-19 2004-01-22 Matsushita Electric Ind Co Ltd Ｄｃ−ｄｃ昇圧方法
JP2004051014A (ja) * 2002-07-22 2004-02-19 Toyoda Gosei Co Ltd 車両用ｌｅｄヘッドランプ装置
JP2005011895A (ja) * 2003-06-17 2005-01-13 Nintendo Co Ltd Ｌｅｄ駆動回路

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Publication number Priority date Publication date Assignee Title
JP2004022929A (ja) * 2002-06-19 2004-01-22 Matsushita Electric Ind Co Ltd Ｄｃ−ｄｃ昇圧方法
JP2004051014A (ja) * 2002-07-22 2004-02-19 Toyoda Gosei Co Ltd 車両用ｌｅｄヘッドランプ装置
JP2005011895A (ja) * 2003-06-17 2005-01-13 Nintendo Co Ltd Ｌｅｄ駆動回路

Cited By (15)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2010539707A (ja) * 2007-09-14 2010-12-16 イクシス コーポレーション プログラム可能なｌｅｄ駆動装置
US9112405B2 (en) 2009-05-11 2015-08-18 Ams Ag Voltage converter with step-down converter circuit and method for converting voltage
WO2010130588A3 (fr) * 2009-05-11 2011-01-06 Austriamicrosystems Ag Convertisseur de tension et procédé de conversion de tension
JP2011023750A (ja) * 2010-10-26 2011-02-03 Panasonic Corp 発光素子駆動装置および発光装置
CN103200730A (zh) * 2012-01-06 2013-07-10 苏州璨宇光学有限公司 电流控制电路及其相应的发光二极管模块
CN103533695A (zh) * 2012-07-03 2014-01-22 成都市宏山科技有限公司 Led恒流驱动系统
CN103533699A (zh) * 2012-07-03 2014-01-22 成都市宏山科技有限公司 用于系统测试中发光二极管的恒流驱动电路
CN104735863A (zh) * 2013-12-24 2015-06-24 理察·蓝德立·葛瑞 在低输入电压操作下适用于直接式led驱动器的防闪烁电路
WO2017117723A1 (fr) * 2016-01-05 2017-07-13 Tridonic Gmbh & Co. Kg Pompe de charge à deux étages pour excitateurs de led
GB2561483A (en) * 2016-01-05 2018-10-17 Tridonic Gmbh & Co Kg Two-stage charge pump for LED drivers
GB2561483B (en) * 2016-01-05 2021-08-04 Tridonic Gmbh & Co Kg Two-stage charge pump for LED drivers
AT519927A1 (de) * 2017-04-26 2018-11-15 Zkw Group Gmbh Speiseschaltung zur Versorgung von LEDs aus einer primären Gleichspannung
AT519927B1 (de) * 2017-04-26 2019-02-15 Zkw Group Gmbh Speiseschaltung zur Versorgung von LEDs aus einer primären Gleichspannung
AT520880A1 (de) * 2017-04-26 2019-08-15 Zkw Group Gmbh Speiseschaltung zur Versorgung von LEDs aus einer primären Gleichspannung
WO2021008384A1 (fr) * 2019-07-17 2021-01-21 深圳市洲明科技股份有限公司 Système de réglage de rétroaction d'alimentation électrique et écran de visualisation

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