JP2013037938A - Led lighting device and method of controlling led lighting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce or eliminate a flicker without using a switching power supply nor a high capacity capacitor.SOLUTION: An LED lighting device comprises: a first rectifying element B1 for rectifying an AC voltage to output a rectified voltage Vr from between a first terminal T1 and a second terminal T2; an LED element 11 connected at one end to the first terminal; a current control section 12 for controlling a current flowing through the LED element; a first capacitive element C1 connected between the first terminal and the second terminal; a current direction limiting section 13 connected in series with the first capacitive element between the first terminal and the second terminal so as to limit the direction of current flow; and a control section 14. The control section controls the current direction limiting section to limit the direction of current flow to a direction from the first terminal to the second terminal when the rectified voltage is higher than a charging voltage Vc across the first capacitive element, and to remove the limitation of the direction of current flow when the rectified voltage is equal to or lower than the charging voltage and the current flowing through the LED element is lower than a predetermined value.

Description

  The present invention relates to an LED lighting device used for illumination or the like and a method for controlling the LED lighting device.

  A conventional LED bulb for lighting (LED lighting device) includes a switching power source that converts an AC voltage supplied from an AC power source into a DC voltage, and the converted DC voltage includes a plurality of LEDs connected in series. The LED element is supplied (for example, see Patent Document 1).

  However, switching power supplies are expensive. Moreover, although the switching power supply has an electrolytic capacitor, the electrolytic capacitor has low heat resistance and has a shorter lifetime than the LED element. Therefore, the life of the electrolytic capacitor determines the life of the LED bulb. Furthermore, although the switching power supply needs noise countermeasures, it is not easy to perform in a limited space of the LED bulb.

  On the other hand, an inexpensive LED bulb that does not use a switching power supply is known. In this LED bulb, the AC voltage supplied from the AC power source is full-wave rectified by a rectifier element (bridge diode), and the rectified voltage is applied to the LED element to light the LED element. Further, the current control unit controls the current flowing through the LED element to a constant current.

JP 2010-287430 A

  In the LED bulb that does not use the above-described switching power supply, a voltage equal to or higher than the forward voltage Vf × N is required to light up the N LEDs. For example, since the rectified voltage periodically changes between 0 V and 140 V, the period during which the LED element is lit (that is, the conduction width in which the LED element is conducted) is the period during which the rectified voltage is equal to or higher than Vf × N. Limited to. The conduction width depends on the maximum value of the rectified voltage, N, and the like, but is, for example, about 50% of the period during which the AC voltage is supplied. That is, a phenomenon called flicker (flicker) in which the LED element is alternately turned on and off is generated. Flicker does not appear in LED bulbs that use switching power supplies. This flicker has a problem of adversely affecting the user of the LED bulb.

  In such an LED bulb, as shown in FIG. 6, flicker can be reduced by connecting, for example, a capacitor C1 of about 1.5 μF between the output terminals of the rectifying element B1. However, flicker cannot be eliminated. That is, as shown in FIG. 7, the current flowing through the LED element 11 is equal to or less than a constant current for a period of about 15% of the period during which the AC voltage is supplied, and thus the LED element 11 is turned off during this period. That is, the conduction width is about 85%.

  Flicker can be eliminated by using a capacitor having a large capacity of 4 to 5 μF. However, since such a large-capacity capacitor of 4 to 5 μF is large, there is a problem that it does not fit in the case of the LED bulb.

  Therefore, an object of the present invention is to provide an LED lighting device and a method for controlling the LED lighting device that can reduce or eliminate flicker without using a switching power supply and a large-capacity capacitor.

An LED lighting device according to an embodiment according to one aspect of the present invention,
A first rectifying element that rectifies an AC voltage supplied from an AC power source and outputs a rectified voltage between the first terminal and the second terminal;
An LED element having one end connected to the first terminal;
A current control unit that is connected between the other end of the LED element and the second terminal and controls a current flowing through the LED element;
A first capacitive element connected between the first terminal and the second terminal;
A current direction limiting unit that is connected in series to the first capacitive element between the first terminal and the second terminal and is capable of limiting a direction in which a current flows;
A control unit for controlling the current direction limiting unit,
The controller is
When the rectified voltage becomes higher than the charging voltage across the first capacitive element, the current direction limiting unit is controlled so as to limit the direction of current flow from the first terminal to the second terminal. With
When the rectified voltage is equal to or lower than the charging voltage and the current flowing through the LED element becomes less than a predetermined value, the current direction limiting unit is controlled to release the limitation on the direction of current flow. And

In the LED lighting device,
The current direction limiting unit is
A second rectifier element connected in series to the first capacitor element between the first terminal and the second terminal, and causing a current to flow from the first terminal toward the second terminal;
A switching element connected in parallel to the second rectifying element,
The controller is
When the rectified voltage becomes higher than the charging voltage, the switch element is controlled to be off,
When the rectified voltage becomes equal to or lower than the charging voltage, and the current flowing through the LED element becomes less than the predetermined value, the switch element may be controlled to be turned on.

In the LED lighting device,
The current direction limiting unit is
A third rectifier element that is connected in series to the switch element between both ends of the second rectifier element and that allows a current to flow from the second terminal to the first terminal when the switch element is turned on; Good.

In the LED lighting device,
The second rectifying element has an anode connected to the first terminal, a cathode connected to one end of the first capacitive element,
The other end of the first capacitive element is connected to the second terminal,
The third rectifying element has a cathode connected to the first terminal,
The switch element may have one end connected to the anode of the third rectifying element and the other end connected to the cathode of the second rectifying element.

In the LED lighting device,
The controller is
A set signal generation circuit that generates a set signal when the current flowing through the LED element becomes less than the predetermined value;
A reset signal generation circuit that generates a reset signal in a period in which the rectified voltage is higher than the charging voltage;
A set-reset circuit that controls the switch element to be turned on when the set signal is input and controls the switch element to be turned off regardless of the set signal when the reset signal is input. Good.

In the LED lighting device,
The current controller is
A current control transistor having one end connected to the other end of the LED element;
A current detection resistor connected between the other end of the current control transistor and the second terminal;
A reference voltage circuit for supplying a reference voltage to the control terminal of the current control transistor,
The control unit may determine that a current flowing through the LED element is less than the predetermined value based on a voltage of the current detection resistor.

In the LED lighting device,
The reference voltage circuit is
A first resistor having one end connected to the first terminal;
One end is connected to the other end of the first resistor, the other end is connected to the second terminal, and a reference voltage generating element that generates the reference voltage between the one end and the other end may be included.

In the LED lighting device,
The set signal generation circuit includes:
A fourth rectifying element having an anode connected to the other end of the current control transistor;
A second capacitive element connected between the cathode of the fourth rectifying element and the second terminal;
A PNP transistor having a base connected to the other end of the current control transistor, an emitter connected to a cathode of the fourth rectifying element, and outputting the set signal from a collector.

In the LED lighting device,
The set / reset circuit includes:
A first NPN transistor having the reset signal supplied to a base, a collector connected to the cathode of the fourth rectifying element, and an emitter connected to the second terminal;
A thyristor, wherein an anode is connected to a cathode of the fourth rectifying element, and the set signal is supplied to a control terminal;
A switch element control circuit that controls the switch element to be turned on when the anode and the cathode of the thyristor are in a conductive state and controls the switch element to be turned off when the thyristor is in a non-conductive state.

In the LED lighting device,
The switch element may include a P-type MOS transistor having a source connected to the cathode of the second rectifier element and a drain connected to the anode of the third rectifier element.

In the LED lighting device,
The current direction limiting unit is
You may have the 1st voltage limiting element connected between the gate and source | sauce of the said P-type MOS transistor.

In the LED lighting device,
The current direction limiting unit is
A second resistor connected between the gate and source of the P-type MOS transistor may be included.

In the LED lighting device,
The switch element control circuit includes:
A control signal output circuit that outputs a high-level control signal when the anode and cathode of the thyristor are in a conductive state and outputs the low-level control signal when in a non-conductive state;
An N-type MOS transistor having a drain connected to the gate of the P-type MOS transistor, a source connected to the second terminal, and the control signal supplied to the gate may be included.

In the LED lighting device,
The switch element control circuit includes:
A second voltage limiting element connected between the gate and source of the N-type MOS transistor may be included.

In the LED lighting device,
The control signal output circuit is
A second NPN transistor having a base connected to the cathode of the thyristor and an emitter connected to the second terminal;
A third resistor connected between a base of the second NPN transistor and the second terminal;
A fourth resistor connected between the collector of the second NPN transistor and the first terminal;
A third NPN transistor having a base connected to the collector of the second NPN transistor, an emitter connected to the second terminal, and outputting the control signal from the collector;
And a fifth resistor connected between the collector of the third NPN transistor and the first terminal.

In the LED lighting device,
In the reset signal generation circuit, a non-inverting input terminal is connected to the first terminal, an inverting input terminal is connected between the first capacitor element and the second rectifying element, and the reset signal is output from an output terminal. May be included.

In the LED lighting device,
The reset signal generation circuit includes:
A sixth resistor connected between the first terminal and the non-inverting input terminal of the amplifier;
A seventh resistor connected between the non-inverting input terminal and the second terminal of the amplifier;
An eighth resistor connected between the first capacitive element and the second rectifying element and between the inverting input terminal of the amplifier;
And a ninth resistor connected between the inverting input terminal and the second terminal of the amplifier.

In the LED lighting device,
A discharge resistor connected in parallel to both ends of the first capacitive element may be provided.

An LED lighting device control method according to an embodiment of one aspect of the present invention includes:
A first rectifying element that rectifies an AC voltage supplied from an AC power source and outputs a rectified voltage between the first terminal and the second terminal;
An LED element having one end connected to the first terminal;
A current control unit that is connected between the other end of the LED element and the second terminal and controls a current flowing through the LED element;
A first capacitive element connected between the first terminal and the second terminal;
A current direction limiting unit that is connected in series to the first capacitive element between the first terminal and the second terminal and is capable of limiting a direction in which a current flows;
A control unit for controlling the current direction limiting unit, and a control method of an LED lighting device comprising:
By the control unit,
When the rectified voltage becomes higher than the charging voltage across the first capacitive element, the current direction limiting unit is controlled so as to limit the direction of current flow from the first terminal to the second terminal. With
When the rectified voltage is equal to or lower than the charging voltage and the current flowing through the LED element becomes less than a predetermined value, the current direction limiting unit is controlled to release the limitation on the direction of current flow. And

In the control method of the LED lighting device,
The current direction limiting unit is
A second rectifier element connected in series to the first capacitor element between the first terminal and the second terminal, and causing a current to flow from the first terminal toward the second terminal;
A switching element connected in parallel to the second rectifying element,
By the control unit,
When the rectified voltage becomes higher than the charging voltage, the switch element is controlled to be off,
When the rectified voltage becomes equal to or lower than the charging voltage, and the current flowing through the LED element becomes less than the predetermined value, the switch element may be controlled to be turned on.

  According to the LED lighting device and the method for controlling the LED lighting device according to one aspect of the present invention, the first capacitor is provided between the first terminal and the second terminal of the first rectifying element that rectifies the supplied AC voltage. The element and the current direction limiting unit are connected in series. In addition, when the rectified voltage from the first rectifying element becomes higher than the charging voltage at both ends of the first capacitive element, the current flows so as to limit the direction in which the current flows from the first terminal to the second terminal. The direction limiter is controlled. Thereby, while the rectified voltage is increased to the maximum value, the first capacitor element can be charged with the rectified voltage.

  In addition, when the rectified voltage is reduced to be equal to or lower than the charging voltage and the current flowing through the LED element becomes less than a predetermined value, the current direction limiting unit is controlled so as to release the restriction on the direction in which the current flows. . As a result, even if the rectified voltage decreases from the maximum value, the current direction limiter limits the direction in which the current flows until the current of the LED element decreases. The maximum value of the rectified voltage can be maintained. A charging voltage higher than the reduced rectified voltage can be supplied from the first capacitor element to the LED element at the timing when the current of the LED element decreases. Therefore, at the timing when the current of the LED element decreases, the current can be returned to a predetermined value or more by the charging voltage, and the LED element can be kept on.

  As described above, since the charge charged in the first capacitor element is not discharged until necessary timing, the first capacitor element having a small capacity can efficiently supply the LED element. That is, flicker can be reduced or eliminated without using a switching power supply and a large-capacity capacitor.

It is a block diagram which shows schematic structure of the LED lighting device which concerns on Example 1 of this invention. It is a circuit diagram of the LED lighting device which concerns on Example 1 of this invention. It is a wave form diagram of the LED lighting device which concerns on Example 1 of this invention. It is a figure which shows the relationship between the alternating voltage and the capacity | capacitance value into which the electric current of the LED lighting device which concerns on Example 1 of this invention and the conventional LED lighting device flows continuously. It is a block diagram which shows schematic structure of the LED lighting device which concerns on Example 2 of this invention. It is a circuit diagram of the conventional LED lighting device. It is a wave form diagram of the conventional LED lighting device.

  Embodiments according to the present invention will be described below with reference to the drawings.

  FIG. 1 is a block diagram illustrating a schematic configuration of an LED lighting device according to Embodiment 1 of the present invention. As shown in FIG. 1, the LED lighting device includes a first rectifying element B1, an LED element 11, a current control unit 12, a first capacitor element C1, a resistor (discharge resistor) R1, and a current direction limit. Unit 13 and control unit 14. The LED lighting device is, for example, an LED bulb for illumination or information display.

  The rectifying element B1 is a bridge diode composed of four diodes, and full-wave rectifies the AC voltage supplied from the AC power supply to output a rectified voltage Vr from between the first terminal T1 and the second terminal T2.

  The LED element 11 has an anode (one end) connected to the first terminal T1 of the rectifying element B1 and is supplied with the rectified voltage Vr. The current control unit 12 is connected between the cathode (the other end) of the LED element 11 and the second terminal T2 of the rectifying element B1, and controls the current flowing through the LED element 11.

  The first capacitive element C1 is connected between the first terminal T1 and the second terminal T2. The resistor R1 is connected in parallel to both ends of the first capacitive element C1. The resistor R1 is for discharging the charge of the first capacitive element C1 when the AC power supply is off, and has a resistance value of several MΩ, for example.

  The current direction limiting unit 13 is connected in series to the first capacitive element C1 between the first terminal T1 and the second terminal T2. In this embodiment, the current direction limiting unit 13 is connected between the first terminal T1 and one end of the first capacitive element C1. The current direction limiting unit 13 is configured to be capable of limiting the direction of current flow from the first terminal T1 to the second terminal T2.

  In the present embodiment, the current direction limiting unit 13 includes a diode (second rectifier element) D1, a diode (third rectifier element) D2, and a switch element SW1.

  The diode D1 is connected in series to the first capacitive element C1 between the first terminal T1 and the second terminal T2, and allows current to flow from the first terminal T1 to the second terminal T2. In this embodiment, the diode D1 has an anode connected to the first terminal T1, and a cathode connected to one end of the first capacitor element C1.

  The switch element SW1 is connected in parallel to the diode D1. The diode D2 is connected in series with the switch element SW1 between both ends of the diode D1, and flows a current from the second terminal T2 to the first terminal T1 when the switch element SW1 is turned on. In this embodiment, the cathode of the diode D2 is connected to the first terminal T1. The switch element SW1 has one end connected to the anode of the diode D2, and the other end connected to the cathode of the diode D1.

  The control unit 14 controls the current direction limiting unit 13. Specifically, the control unit 14 determines the direction in which the current flows when the rectified voltage Vr becomes higher than the charging voltage Vc across the first capacitor element C1, that is, when the first condition is satisfied, the first terminal T1. The current direction limiting unit 13 is controlled so as to limit to the direction of the second terminal T2. Further, the control unit 14 restricts the direction in which the current flows when the rectified voltage Vr becomes equal to or lower than the charging voltage Vc and the current flowing through the LED element 11 becomes less than a predetermined value, that is, when the second condition is satisfied. The current direction limiting unit 13 is controlled so as to release More specifically, the control unit 14 controls the switch element SW1 to be turned off when the first condition is met, and controls the switch element SW1 to be turned on when the second condition is met.

  Next, an example of a specific circuit configuration of the LED lighting device of FIG. 1 will be described with reference to FIG.

  FIG. 2 is a circuit diagram of the LED lighting device according to Embodiment 1 of the present invention. As shown in FIG. 2, the LED element 11 includes N (N is a positive integer) LEDs (LED1 to LEDN) connected in series.

  The current control unit 12 includes an N-type MOS transistor (current control transistor) Q1, a current detection resistor R2, a resistor (first resistor) R3, and a Zener diode (reference voltage generating element) ZD1.

  In the N-type MOS transistor Q1, the drain (one end) is connected to the cathode (the other end) of the LED element 11. The current detection resistor R2 is connected between the source (the other end) of the N-type MOS transistor Q1 and the second terminal T2.

  The resistor R3 has one end connected to the first terminal T1 through the diode D1. That is, one end of the resistor R3 is connected to the cathode of the diode D1.

  The Zener diode ZD1 has a cathode (one end) connected to the other end of the resistor R3, an anode (other end) connected to the second terminal T2, and generates a reference voltage between the cathode and the anode. The cathode of the Zener diode ZD1 is also connected to the gate (control terminal) of the N-type MOS transistor Q1.

  The resistor R3 and the Zener diode ZD1 function as a reference voltage circuit. That is, the reference voltage circuit supplies the reference voltage to the gate of the N-type MOS transistor Q1.

  The switch element SW1 of the current direction limiting unit 13 is composed of a P-type MOS transistor Q7. In the P-type MOS transistor Q7, the source is connected to the cathode of the diode D1, and the drain is connected to the anode of the diode D2.

  The current direction limiting unit 13 includes a Zener diode (first voltage limiting element) ZD3 and a resistor (second resistor) R17. Zener diode ZD3 has an anode connected to the gate of P-type MOS transistor Q7 and a cathode connected to the source of P-type MOS transistor Q7. The resistor R17 is connected between the gate and source of the P-type MOS transistor Q7.

  The control unit 14 includes a set signal generation circuit 21, a reset signal generation circuit 22, and a set reset circuit 23.

  The set signal generation circuit 21 generates the set signal S when the current flowing through the LED element 11 becomes less than a predetermined value based on the voltage across the current detection resistor R2.

  The reset signal generation circuit 22 generates the reset signal R during a period in which the rectified voltage Vr is higher than the charging voltage Vc.

  The set reset circuit 23 controls the switch element SW1 to be turned on when the set signal S is input, and controls the switch element SW1 to be turned off regardless of the set signal S when the reset signal R is input.

  The set signal generation circuit 21 includes a diode (fourth rectifier element) D3, a second capacitor element C2, a PNP transistor Q2, and resistors R4 and R5.

  The diode D3 has an anode connected to the connection point between the source of the N-type MOS transistor Q1 and the resistor R2. The second capacitive element C2 is connected between the cathode of the diode D3 and the second terminal T2.

  The PNP transistor Q2 has a base connected to the source of the N-type MOS transistor Q1 via a resistor R4, an emitter connected to the cathode of the diode D3, and outputs a set signal S from the collector via a resistor R5.

  The reset signal generation circuit 22 includes an amplifier (comparator) IC1, a resistor (sixth resistor) R6, a resistor (seventh resistor) R7, a resistor (eighth resistor) R8, and a resistor (ninth resistor) R9. ,including.

  In the amplifier IC1, a non-inverting input terminal (+) is connected to the first terminal T1 via a resistor R6, and an inverting input terminal (−) is connected between the first capacitive element C1 and the diode D1 via a resistor R8. Connected and outputs a reset signal R from the output terminal. In this embodiment, it is assumed that the output terminal of the amplifier IC1 is an open collector.

  The resistor R7 is connected between the non-inverting input terminal (+) of the amplifier IC1 and the second terminal T2. The resistor R9 is connected between the inverting input terminal (−) of the amplifier IC1 and the second terminal T2.

  The set / reset circuit 23 includes an NPN transistor (first NPN transistor) Q3, an NPN transistor (second NPN transistor) Q4, an NPN transistor (third NPN transistor) Q5, and an N type. MOS transistor Q6, thyristor TH1, zener diode (second voltage limiting element) ZD2, resistor R10, resistor R11, resistor (third resistor) R12, resistor (fourth resistor) R13, resistor ( (5th resistance) R14, resistance R15, and resistance R16 are included.

  The NPN transistor Q3 has a base connected to the output terminal of the amplifier IC1, a collector connected to the cathode of the diode D3 via the resistor R10, and an emitter connected to the second terminal T2. The base of the NPN transistor Q3 is also connected to the cathode of the diode D3 via the resistor R11. Thereby, the voltage of the cathode of the diode D3 (the voltage of the second capacitive element C2) can be supplied to the output terminal of the amplifier IC1 as a power source.

  In the thyristor TH1, the anode is connected to the cathode of the diode D3 via the resistor R10, and the set signal S is supplied to the control terminal.

  The NPN transistor Q4 has a base connected to the cathode of the thyristor TH1, and an emitter connected to the second terminal T2.

  The resistor R12 is connected between the base of the NPN transistor Q4 and the second terminal T2. The resistor R13 is connected between the collector of the NPN transistor Q4 and the first terminal T1. In this embodiment, the resistor R13 is connected to the first terminal T1 via the diode D1.

  The NPN transistor Q5 has a base connected to the collector of the NPN transistor Q4, an emitter connected to the second terminal T2, and outputs a control signal C from the collector.

  The resistor R14 is connected between the collector of the NPN transistor Q5 and the first terminal T1. In this embodiment, the resistor R14 is connected to the first terminal T1 through the diode D1. The resistor R13 and the resistor R14 may be directly connected to the first terminal T1 without going through the diode D1.

  The NPN transistor Q4, the NPN transistor Q5, the resistor R12, the resistor R13, and the resistor R14 function as a control signal output circuit. That is, the control signal output circuit outputs a high-level control signal C when the anode and cathode of the thyristor TH1 are in a conductive state, and outputs a low-level control signal C when the thyristor TH1 is in a non-conductive state.

  In the N-type MOS transistor Q6, the drain is connected to the gate of the P-type MOS transistor Q7 via the resistor R15, the source is connected to the second terminal T2, and the control signal C is supplied to the gate. Since the rectified voltage Vr is applied between the source and the drain when the N-type MOS transistor Q6 is off, the N-type MOS transistor Q6 needs to have a breakdown voltage equal to or greater than the maximum value of the rectified voltage Vr.

  Zener diode ZD2 has a cathode connected to the gate of N-type MOS transistor Q6 and an anode connected to the source of N-type MOS transistor Q6. The resistor R16 is connected between the gate and source of the N-type MOS transistor Q6.

  The control signal output circuit, the N-type MOS transistor Q6, the Zener diode ZD2, the resistor R15, and the resistor R16 function as a switch element control circuit. That is, the switch element control circuit controls the P-type MOS transistor Q7 (switch element SW1) to be on when the anode and the cathode of the thyristor TH1 are conductive, and turns off the P-type MOS transistor Q7 when the thyristor TH1 is non-conductive. Configured to control.

  Next, the operation of the LED lighting device will be described with reference to the waveform diagram of FIG. FIG. 3 is a waveform diagram of the LED lighting device according to Embodiment 1 of the present invention. This waveform diagram is obtained when the first capacitor C1 is about 1.47 μF, the frequency of the AC voltage is about 50 Hz, and the effective value of the AC voltage is about 100V. The constant current flowing through the LED element 11 is about 20 mA. Hereinafter, a half cycle of the AC voltage from time t1 to time t5 in FIG. 3 will be described.

  First, at time t1 in FIG. 3, when the rectified voltage Vr becomes higher than the charging voltage Vc as the AC voltage increases, the control unit 14 controls the P-type MOS transistor Q7 to be turned off. Since the current flows in the direction from the first terminal T1 to the second terminal T2 via the diode D1 from the time t1 to the time t2, that is, while the rectified voltage Vr increases to the maximum value, the first rectified voltage Vr Can be charged.

  The circuit level operation of the control unit 14 at this time will be described. When the rectified voltage Vr becomes higher than the charging voltage Vc, the amplifier IC1 generates a high level reset signal R. As a result, the NPN transistor Q3 is turned on, and the charge of the second capacitive element C2 is discharged through the resistor R10. Further, the voltage of the anode of the thyristor TH1 becomes substantially equal to the voltage of the second terminal T2, and the anode and the cathode of the thyristor TH1 become non-conductive. As a result, the base voltage of the NPN transistor Q4 becomes substantially equal to the voltage of the second terminal T2 via the resistor R12, so that the NPN transistor Q4 is turned off. Then, the NPN transistor Q5 is turned on, and the control signal C, that is, the gate voltage of the N-type MOS transistor Q6 is lowered. Then, the N-type MOS transistor Q6 is turned off. Therefore, the gate-source voltage of the P-type MOS transistor Q7 becomes almost zero via the resistor R17, and the P-type MOS transistor Q7 is turned off.

  When the rectified voltage Vr reaches the maximum value at time t2, the charging voltage Vc of the first capacitor element C1 also reaches the maximum value. That is, the first capacitor element C1 is peak charged. The maximum value of the charging voltage Vc at this time is substantially equal to the value obtained by subtracting the forward voltage of the diode D1 from the maximum value of the rectified voltage Vr.

  From time t2 to time t4, the rectified voltage Vr decreases as the AC voltage decreases. However, since the P-type MOS transistor Q7 is turned off and the diode D1 is present, the charge of the first capacitor element C1 is not discharged to the LED element 11 side, so the charging voltage Vc is maintained at the maximum value. As described above, since the resistor R1 has a resistance value of several MΩ (for example, 3 MΩ), the charging voltage Vc hardly decreases through the resistor R1 during a period of about a half cycle of the AC voltage. ing.

  When the rectified voltage Vr decreases and becomes equal to or lower than the charging voltage Vc at time t3, the amplifier IC1 sets the reset signal R to a low level. As a result, the NPN transistor Q3 is turned off. Therefore, the second capacitor C2 is charged via the diode D3 by the voltage generated in the resistor R2 by the current flowing through the LED element 11. Thus, the period during which the reset signal R is at a high level, that is, the period during which the reset signal R is generated is from time t1 to time t3.

  At time t4, when the rectified voltage Vr further decreases and becomes less than a voltage necessary for the LED element 11 to light, the current flowing through the LED element 11 becomes less than a predetermined value. At this time, the control unit 14 controls the P-type MOS transistor Q7 to be turned on. As a result, a charging voltage Vc higher than the reduced rectified voltage Vr can be supplied from the first capacitive element C1 to the LED element 11 via the turned-on P-type MOS transistor Q7 and the diode D2. That is, the rectified voltage Vr rises to a value approximately equal to the charging voltage Vc. Therefore, at the timing when the current of the LED element 11 decreases, the current can be returned to a predetermined value or more by the charging voltage Vc, and the LED element 11 can be kept lit. That is, there is no period during which the LED element 11 is turned off.

  The circuit level operation of the control unit 14 at this time will be described. When the current flowing through the LED element 11 becomes less than a predetermined value, the voltage across the resistor R2 decreases, and the base voltage of the PNP transistor Q2 decreases. On the other hand, the emitter voltage of the PNP transistor Q2 becomes higher than the base voltage due to the voltage charged in the second capacitor element C2. Accordingly, the PNP transistor Q2 is turned on, and the set signal S becomes substantially equal to the voltage charged in the second capacitor element C2. Thereby, the anode and cathode of thyristor TH1 are electrically connected.

  Then, the NPN transistor Q4 is turned on because the base voltage increases. The NPN transistor Q5 is turned off because the base voltage is low. As a result, the control signal C, that is, the gate voltage of the N-type MOS transistor Q6 rises, so that the N-type MOS transistor Q6 is turned on. Therefore, the P-type MOS transistor Q7 is turned on with the gate voltage lowered. At this time, the maximum value of the control signal C is limited by the Zener diode ZD2, and the maximum value of the gate-source voltage of the P-type MOS transistor Q7 is limited by the Zener diode ZD3.

  After the time t4, the LED element 11 is turned on by the charging voltage Vc, so that the charging voltage Vc decreases with the passage of time. That is, the rectified voltage Vr also decreases.

  On the other hand, when the absolute value of the AC voltage starts from decreasing to increasing, the rectified voltage Vr becomes higher than the charging voltage Vc at time t5. That is, the state is similar to that at time t1 described above. Therefore, the control unit 14 controls the P-type MOS transistor Q7 to be turned off. As a result, while the rectified voltage Vr increases to the maximum value, the first capacitive element C1 can be charged with the rectified voltage Vr.

  After time t5, the operation is similar to that from time t1 to time t4. In this way, flicker is eliminated.

  The charging voltage Vc is supplied from the first capacitive element C1 to the LED element 11 via the P-type MOS transistor Q7 and the diode D2 that are turned on, and therefore, between the source and drain of the P-type MOS transistor Q7, A voltage obtained by subtracting the forward voltage or the like of the LED element 11 from the charging voltage Vc is added. Therefore, the breakdown voltage of the P-type MOS transistor Q7 may be lower than the maximum value of the charging voltage Vc. As an example, when the effective value of the AC voltage is about 100V, the withstand voltage may be about 100V.

  Next, the effect of the LED lighting device of Example 1 will be described in comparison with the conventional LED lighting device of FIG.

  FIG. 4 is a diagram illustrating a relationship between an AC voltage and a capacitance value through which current continuously flows in the LED lighting device according to Embodiment 1 of the present invention and the conventional LED lighting device. The vertical axis in FIG. 4 represents the effective value of the AC voltage, and the horizontal axis represents the value of the first capacitive element C1.

  Characteristics A and B show the relationship between the effective value of the AC voltage in which current continuously flows (no flicker) in the LED element 11 of the LED lighting device of Example 1 and the capacitance value of the first capacitor element C1. . Characteristic A has an alternating voltage frequency of 60 Hz, and characteristic B is 50 Hz.

  Characteristics C and D show the relationship between the effective value of the alternating voltage in which current continuously flows in the LED element 11 of the conventional LED lighting device of FIG. 6 and the value of the first capacitor element C1. Characteristic C has an alternating voltage frequency of 60 Hz, and characteristic D is 50 Hz. The conventional LED lighting device of FIG. 6 has a configuration in which the current direction limiting unit 13, the control unit 14, the first capacitive element C1, and the resistor R1 are removed from the LED lighting device of Example 1 of FIG. ing.

  As can be seen from the comparison between the characteristics A and C, in the LED lighting device of Example 1, the current to the LED element 11 is lower than that of the conventional LED lighting device in the range where the first capacitance element C1 is about 3 μF or less. Flows continuously. The effective value of the AC voltage necessary for the current to continuously flow through the LED element 11 is, for example, about 125 V in the conventional LED lighting device when the first capacitance element C1 is 1 μF, but the LED of Example 1 In the lighting device, it is about 111V. Further, for example, when the first capacitance element C1 is 1.47 μF, the effective value is about 105 V in the conventional LED lighting device, but is about 96 V in the LED lighting device of Example 1.

  Also from the comparison of characteristics B and D, in the LED lighting device of Example 1, the current continues to the LED element 11 at a lower voltage than the conventional LED lighting device in the range where the first capacitance element C1 is about 3 μF or less. You can see that it is flowing. The effective value of the AC voltage necessary for the current to continuously flow through the LED element 11 is, for example, about 140 V in the conventional LED lighting device when the first capacitance element C1 is 1 μF, but the LED of Example 1 In the lighting device, it is about 117V. Further, for example, when the first capacitance element C1 is 1.47 μF, the effective value is about 112 V in the conventional LED lighting device, but is about 103 V in the LED lighting device of the first embodiment.

  Thus, in the LED lighting device of Example 1, for example, the first capacitor element C1 is about 1.47 μF, and the current is continuously supplied to the LED element 11 at the voltage and frequency of commercial AC in Japan. It can flow. That is, flicker can be eliminated.

  On the other hand, in the conventional LED lighting device, for example, if the first capacitance element C1 is about 1.47 μF, flicker cannot be eliminated at the voltage and frequency of commercial AC in Japan.

  That is, in the LED lighting device according to the first embodiment, as compared with the conventional LED lighting device, flicker is eliminated by the first capacitance element C1 having a small capacitance value as long as the AC voltage frequency and effective value are equal. Can do.

  Note that the characteristics shown in FIG. 4 are merely examples, and specific voltages and capacitance values slightly change depending on the adjustment of the constant of each element. However, in the LED lighting device of Example 1, the effect that the current continuously flows to the LED element 11 at a lower voltage than that of the conventional LED lighting device under the condition that the first capacitor element C1 is a small capacity is not changed.

  Thus, according to the present embodiment, the first capacitive element C1 and the diode D1 are connected in series between the first terminal T1 and the second terminal T2 of the first rectifying element B1 that rectifies the supplied AC voltage. The switch element SW1 is connected in parallel to the diode D1. The diode D1 is configured to pass a current from the first terminal T1 to the second terminal T2.

  In addition, when the rectified voltage Vr from the first rectifier element B1 becomes higher than the charging voltage Vc across the first capacitor element C1, the switch element SW1 is controlled to be turned off. As a result, while the rectified voltage Vr increases to the maximum value, the first capacitive element C1 can be charged with the rectified voltage Vr via the diode D1.

  Further, when the rectified voltage Vr decreases to be equal to or lower than the charging voltage Vc and the current flowing through the LED element 11 becomes less than a predetermined value, the switch element SW1 is controlled to be turned on. As a result, even if the rectified voltage Vr decreases from the maximum value, the switch element SW1 is turned off until the current of the LED element 11 decreases, so that the charging voltage Vc of the first capacitive element C1 is almost equal to the rectified voltage Vr. Can hold the maximum value. Then, at the timing when the current of the LED element 11 decreases, a charging voltage Vc higher than the reduced rectified voltage Vr can be supplied from the first capacitor element C1 to the LED element 11 via the switch element SW1. Therefore, at the timing when the current of the LED element 11 decreases, the current can be returned to a predetermined value or more by the charging voltage Vc, and the LED element 11 can be kept lit.

  As described above, since the charge charged in the first capacitor element C1 is not discharged until a necessary timing, the first capacitor element C1 having a small capacity can be efficiently supplied to the LED element 11. That is, flicker can be reduced without using a switching power supply and a large-capacity capacitor. Furthermore, flicker can be eliminated by adjusting the capacitance value of the first capacitor element C1.

  Further, the first capacitor element C1 only needs to be able to be charged / discharged and may have a small capacity, and thus it is not necessary to use an electrolytic capacitor having a short life. For example, a ceramic capacitor having a longer life than an electrolytic capacitor can be used. Accordingly, the LED lighting device can be operated at a higher temperature than the conventional LED lighting device, and the life of the LED lighting device can be extended. Such an effect is particularly useful when the LED lighting device is used as an LED bulb.

  In the second embodiment, the connection position of the current direction limiting unit 13 is different from the first embodiment.

  FIG. 5 is a block diagram showing a schematic configuration of an LED lighting device according to Embodiment 2 of the present invention. As shown in FIG. 5, in the LED lighting device, one end of the first capacitive element C1 is connected to the first terminal T1, and the current direction limiting unit 13 includes the other end of the first capacitive element C1 and the second terminal T2. Connected between and. Similar to the first embodiment, the current direction limiting unit 13 is configured to be able to limit the direction in which the current flows from the first terminal T1 to the second terminal T2.

  The specific configuration of the current direction limiting unit 13 is as follows. The diode D1 has an anode connected to the other end of the first capacitive element C1, and a cathode connected to the second terminal T2. The diode D2 has a cathode connected to the other end of the first capacitive element C1. The switch element SW1 has one end connected to the anode of the diode D2, and the other end connected to the cathode of the diode D1. The switch element SW1 can be configured by, for example, an N-type MOS transistor or a P-type MOS transistor. Since the other circuit configuration is the same as that of the first embodiment shown in FIG. 1, the same components are denoted by the same reference numerals and description thereof is omitted. Further, since the operation is the same as that of the first embodiment, the description thereof is omitted.

  According to the second embodiment having such a configuration, the same effect as that of the first embodiment can be obtained.

  As mentioned above, although the Example of this invention was explained in full detail, a concrete structure is not limited to the said Example, A various deformation | transformation can be implemented in the range which does not deviate from the summary of this invention.

B1 Bridge diode (first rectifier)
T1 1st terminal T2 2nd terminal 11 LED element 12 Current control unit 13 Current direction limiting unit 14 Control unit 21 Set signal generation circuit 22 Reset signal generation circuit 23 Set reset circuit SW1 Switch element D1 Diode (second rectifier element)
D2 diode (third rectifier)
D3 diode (fourth rectifier)
TH1 Thyristor ZD1 Zener diode (reference voltage generator)
ZD2 Zener diode (second voltage limiting element)
ZD3 Zener diode (first voltage limiting element)
C1 First capacitive element C2 Second capacitive element IC1 Amplifier Q1 N-type MOS transistor (current control transistor)
Q2 PNP transistor Q3 NPN transistor (first NPN transistor)
Q4 NPN transistor (second NPN transistor)
Q5 NPN transistor (third NPN transistor)
Q6 N-type MOS transistor Q7 P-type MOS transistor R1 Resistance (discharge resistance)
R2 Current detection resistor R3 Resistance (first resistor)
R4, R5 resistor R6 resistor (sixth resistor)
R7 resistance (7th resistance)
R8 resistance (8th resistance)
R9 resistance (9th resistance)
R10, R11 resistor R12 resistor (third resistor)
R13 resistance (4th resistance)
R14 resistor (5th resistor)
R15, R16 resistor R17 resistor (second resistor)

Claims (20)

A first rectifying element that rectifies an AC voltage supplied from an AC power source and outputs a rectified voltage between the first terminal and the second terminal;
An LED element having one end connected to the first terminal;
A current control unit that is connected between the other end of the LED element and the second terminal and controls a current flowing through the LED element;
A first capacitive element connected between the first terminal and the second terminal;
A current direction limiting unit that is connected in series to the first capacitive element between the first terminal and the second terminal and is capable of limiting a direction in which a current flows;
A control unit for controlling the current direction limiting unit,
The controller is
When the rectified voltage becomes higher than the charging voltage across the first capacitive element, the current direction limiting unit is controlled so as to limit the direction of current flow from the first terminal to the second terminal. With
When the rectified voltage is equal to or lower than the charging voltage and the current flowing through the LED element becomes less than a predetermined value, the current direction limiting unit is controlled to release the limitation on the direction of current flow. LED lighting device. The current direction limiting unit is
A second rectifier element connected in series to the first capacitor element between the first terminal and the second terminal, and causing a current to flow from the first terminal toward the second terminal;
A switching element connected in parallel to the second rectifying element,
The controller is
When the rectified voltage becomes higher than the charging voltage, the switch element is controlled to be off,
2. The LED lighting according to claim 1, wherein when the rectified voltage becomes equal to or lower than the charging voltage and a current flowing through the LED element becomes less than the predetermined value, the switch element is controlled to be turned on. apparatus. The current direction limiting unit is
A third rectifier element is provided which is connected in series to the switch element between both ends of the second rectifier element, and causes a current to flow from the second terminal to the first terminal when the switch element is turned on. The LED lighting device according to claim 2. The second rectifying element has an anode connected to the first terminal, a cathode connected to one end of the first capacitive element,
The other end of the first capacitive element is connected to the second terminal,
The third rectifying element has a cathode connected to the first terminal,
4. The LED lighting device according to claim 3, wherein one end of the switch element is connected to an anode of the third rectifier element, and the other end is connected to a cathode of the second rectifier element. The controller is
A set signal generation circuit that generates a set signal when the current flowing through the LED element becomes less than the predetermined value;
A reset signal generation circuit that generates a reset signal in a period in which the rectified voltage is higher than the charging voltage;
A set-reset circuit that controls the switch element to be turned on when the set signal is input and controls the switch element to be turned off regardless of the set signal when the reset signal is input. The LED lighting device according to claim 4. The current controller is
A current control transistor having one end connected to the other end of the LED element;
A current detection resistor connected between the other end of the current control transistor and the second terminal;
A reference voltage circuit for supplying a reference voltage to the control terminal of the current control transistor,
The LED lighting device according to claim 5, wherein the control unit determines that a current flowing through the LED element is less than the predetermined value based on a voltage of the current detection resistor. The reference voltage circuit is
A first resistor having one end connected to the first terminal;
One end connected to the other end of the first resistor, the other end connected to the second terminal, and a reference voltage generating element for generating the reference voltage between the one end and the other end. The LED lighting device according to claim 6. The set signal generation circuit includes:
A fourth rectifying element having an anode connected to the other end of the current control transistor;
A second capacitive element connected between the cathode of the fourth rectifying element and the second terminal;
A PNP transistor having a base connected to the other end of the current control transistor, an emitter connected to a cathode of the fourth rectifying element, and outputting the set signal from a collector. The LED lighting device according to claim 6 or 7. The set / reset circuit includes:
A first NPN transistor having the reset signal supplied to a base, a collector connected to the cathode of the fourth rectifying element, and an emitter connected to the second terminal;
A thyristor, wherein an anode is connected to a cathode of the fourth rectifying element, and the set signal is supplied to a control terminal;
A switching element control circuit for controlling the switching element to be turned on when the anode and the cathode of the thyristor are in a conductive state and controlling the switching element to be turned off when the thyristor is in a non-conductive state. Item 9. The LED lighting device according to Item 8. The switch element includes a P-type MOS transistor having a source connected to a cathode of the second rectifier element and a drain connected to an anode of the third rectifier element. LED lighting device according to. The current direction limiting unit is
The LED lighting device according to claim 10, further comprising a first voltage limiting element connected between a gate and a source of the P-type MOS transistor. The current direction limiting unit is
The LED lighting device according to claim 10 or 11, further comprising a second resistor connected between a gate and a source of the P-type MOS transistor. The switch element control circuit includes:
A control signal output circuit that outputs a high-level control signal when the anode and cathode of the thyristor are in a conductive state and outputs the low-level control signal when in a non-conductive state;
11. An N-type MOS transistor having a drain connected to the gate of the P-type MOS transistor, a source connected to the second terminal, and the control signal supplied to the gate. Item 13. The LED lighting device according to any one of Items 12. The switch element control circuit includes:
The LED lighting device according to claim 13, further comprising a second voltage limiting element connected between a gate and a source of the N-type MOS transistor. The control signal output circuit is
A second NPN transistor having a base connected to the cathode of the thyristor and an emitter connected to the second terminal;
A third resistor connected between a base of the second NPN transistor and the second terminal;
A fourth resistor connected between the collector of the second NPN transistor and the first terminal;
A third NPN transistor having a base connected to the collector of the second NPN transistor, an emitter connected to the second terminal, and outputting the control signal from the collector;
The LED lighting device according to claim 13, further comprising a fifth resistor connected between a collector of the third NPN transistor and the first terminal. In the reset signal generation circuit, a non-inverting input terminal is connected to the first terminal, an inverting input terminal is connected between the first capacitor element and the second rectifying element, and the reset signal is output from an output terminal. The LED lighting device according to any one of claims 5 to 15, further comprising: an amplifier that outputs. The reset signal generation circuit includes:
A sixth resistor connected between the first terminal and the non-inverting input terminal of the amplifier;
A seventh resistor connected between the non-inverting input terminal and the second terminal of the amplifier;
An eighth resistor connected between the first capacitive element and the second rectifying element and between the inverting input terminal of the amplifier;
The LED lighting device according to claim 16, further comprising a ninth resistor connected between the inverting input terminal and the second terminal of the amplifier. The LED lighting device according to any one of claims 1 to 17, further comprising a discharge resistor connected in parallel to both ends of the first capacitor element. A first rectifying element that rectifies an AC voltage supplied from an AC power source and outputs a rectified voltage between the first terminal and the second terminal;
An LED element having one end connected to the first terminal;
A current control unit that is connected between the other end of the LED element and the second terminal and controls a current flowing through the LED element;
A first capacitive element connected between the first terminal and the second terminal;
A current direction limiting unit that is connected in series to the first capacitive element between the first terminal and the second terminal and is capable of limiting a direction in which a current flows;
A control unit for controlling the current direction limiting unit, and a control method of an LED lighting device comprising:
By the control unit,
When the rectified voltage becomes higher than the charging voltage across the first capacitive element, the current direction limiting unit is controlled so as to limit the direction of current flow from the first terminal to the second terminal. With
When the rectified voltage is equal to or lower than the charging voltage and the current flowing through the LED element becomes less than a predetermined value, the current direction limiting unit is controlled to release the limitation on the direction of current flow. A method for controlling the LED lighting device. The current direction limiting unit is
A second rectifier element connected in series to the first capacitor element between the first terminal and the second terminal, and causing a current to flow from the first terminal toward the second terminal;
A switching element connected in parallel to the second rectifying element,
By the control unit,
When the rectified voltage becomes higher than the charging voltage, the switch element is controlled to be off,
The LED lighting according to claim 19, wherein when the rectified voltage becomes equal to or lower than the charging voltage and the current flowing through the LED element becomes less than the predetermined value, the switch element is turned on. Control method of the device.

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