JP2011070883A - Power supply circuit for led lighting device and led lighting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent flickering of an LED. <P>SOLUTION: A diode bridge 105 and an auxiliary circuit 109 are connected in parallel with respect to a triac 103. The auxiliary circuit 109 includes: a current path through which an auxiliary current Ir exceeding its holding current from the triac 103 flows; a detection part R2 which detects a power supply current Iac flowing through the diode bridge 105; and a control part by which the current path is opened when the power supply current Iac becomes equal to or lower than a threshold which is larger than the holding current of the triac 103, and the current path is closed when the power supply current Iac exceeds the threshold. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a power supply circuit for an LED lighting device and an LED lighting device.

In a general lighting device using a light bulb or the like as a light source, in order to adjust the amount of light, a power supply circuit incorporating a triac is widely known. Such a power supply circuit has a configuration in which a triac, a rectifier circuit, and a voltage adjustment circuit are sequentially connected between an AC power supply and a light source.
In recent years, development of an illumination device using an LED as a light source (referred to as an “LED illumination device” in this specification) is progressing due to a demand for energy saving and the like.
Since a power supply circuit having a dimming function using a triac can be manufactured in a small size and at low cost, it is desired to apply this power supply circuit to an LED lighting device as it is.
Reference should be made to Patent Document 1 and Patent Document 2 as prior documents related to the present invention.

JP 2006-32032 A JP 2007-227155 A

According to the study by the present inventors, when the power supply circuit is directly applied to an LED lighting device,
The light emission of the LED was not stable and flicker was observed. The current required to emit an LED is very small compared to a light bulb, etc., so when the current is not stable when switching the triac on or off, or when noise such as surge current enters the power circuit, the power circuit The current flowing through the current may decrease instantaneously. On the other hand, in order to keep the triac on, it is necessary that a current exceeding a predetermined holding current flows in the triac. Therefore, when the current flowing through the power supply circuit becomes less than the triac holding current for some reason, the triac is reset (turned off), and the current supply to the LED is stopped. This is thought to cause flickering.

Therefore, the present inventors have thought that such flickering can be prevented if a current exceeding the holding current always flows to the triac (in other words, a leakage state). For this reason, an auxiliary circuit is provided in parallel with the rectifier and voltage regulator circuit connected to the triac, and the auxiliary circuit has a weak current exceeding the holding current (referred to as “compensation current” in this specification). Always).
However, even if it is weak, always flowing the compensation current leads to power consumption, which may cause a reduction in the efficiency of the LED lighting device.

Therefore, the present inventors have conceived the present invention by considering that the compensation current is supplied to the auxiliary circuit only when necessary to prevent the triac from being turned off.
The first aspect of the present invention is defined as follows. That is,
A power supply circuit for an LED lighting device including a triac, a rectifier circuit, and a voltage adjustment circuit,
The rectifier circuit and the auxiliary circuit are connected in parallel to the triac,
The auxiliary circuit includes a first current path through which a current exceeding the holding current flows from the triac, a detection unit that detects a power supply current flowing through the rectifier circuit, and a first current that is larger than the holding current of the triac. And a controller that opens the first current path when the threshold current is below a threshold value and closes the first current path when the power supply current exceeds the first threshold value. Power supply circuit for equipment.

  According to the power supply circuit for the LED lighting device of the first aspect defined as described above, on / off of the first current path of the auxiliary circuit is controlled based on the value of the power supply current flowing from the triac to the rectifier circuit. The Therefore, before the power supply current becomes lower than the triac holding current, that is, when the power supply current becomes lower than the first threshold value larger than the holding current, a current larger than the holding current (compensation) is supplied to the first current path of the auxiliary circuit. Current) can be prevented from inadvertently turning off a triac that should be kept on. When the power supply current exceeds the first threshold value, the possibility that the triac is turned off is extremely reduced, and therefore the flow of the compensation current to the first current path of the auxiliary circuit is stopped. Thereby, useless power consumption can be suppressed.

The second aspect of the present invention is defined as follows. That is,
A power supply circuit for an LED lighting device including a triac, a rectifier circuit, and a voltage adjustment circuit,
The rectifier circuit and the auxiliary circuit are connected in parallel to the triac,
The auxiliary circuit includes a second current path for causing a current exceeding the holding current to flow from the triac for a predetermined time immediately after the triac is turned on. .

According to the power supply circuit for the LED lighting device of the second aspect defined as described above, the compensation current exceeding the holding current from the triac for a predetermined time immediately after the triac is switched on is the second current path. Shed through.
Here, immediately after the TRIAC is switched on, the power supply current becomes unstable (vibrates), and the value may be equal to or less than the TRIAC holding current. Possible causes of unstable power supply current include charging / discharging timing of a smoothing capacitor attached to the rectifier circuit and resonance between the capacitor and inductance in the power supply circuit.
According to the power supply circuit defined in the second aspect, while the power supply current is unstable, the triac in the state that should be kept on is unexpectedly turned off by supplying a compensation current to the second current path of the auxiliary circuit. Can be prevented. Then, wasteful current consumption can be prevented by appropriately setting the energization time of the compensation current.

It is a figure which shows the power supply circuit for LED lighting apparatuses which concern on embodiment of this invention. 2 is a timing chart showing the operation of the element shown in FIG. 1. It is a figure which shows the power supply circuit for LED lighting apparatuses which concern on other embodiment of this invention. 4 is a timing chart showing the operation of the element shown in FIG. 3.

  FIG. 1 shows a power supply circuit for an LED lighting device according to an embodiment of the present invention. In FIG. 1, 101 indicates an LED illumination device, and 103 indicates a triac. The LED lighting device 101 includes a diode bridge 105 that constitutes a rectifier circuit, a DC-DC converter 107 that constitutes a voltage adjustment circuit, and an auxiliary circuit 109, and the diode bridge 105 and the auxiliary circuit 109 are parallel to the triac 103. Is provided. In the figure, D1 and D2 are rectifying diodes, R1 is a resistor for flowing current immediately after the triac 103 is turned on, R2 is a resistor for detecting the current flowing through the LED lighting device 101, and R3 and R4 are switching The gate resistance of the element Q1, R5, R6, and R7 are resistors for generating the reference voltage Vref, Q1 is a switching element for controlling the current flowing through the resistor R1, Q2 is a comparator whose output is an open collector, and ZD1 is a reference voltage A zener diode for stabilization is shown.

  The auxiliary circuit 109 has a current path through which a compensation current exceeding the holding current flows from the triac 103, and includes a resistor R2 that constitutes a detection unit that detects the power source current Iac flowing through the diode bridge 105, and the power source current Iac is Comparator Q2 that constitutes a controller for opening a current path when the threshold current is larger than a holding current or less and closing the current path when power supply current Iac exceeds the threshold value.

  The output of the comparator Q2 is an open collector, and the detection voltage Vr is input to the inverting input terminal (− terminal) of the comparator Q2, and the reference voltage Vref is input to the non-inverting input terminal (+ terminal). The reference voltage Vref is generated by dividing the control circuit power source generated by the DC-DC converter 107 by resistors R5, R6, and R7 connected in series.

  The operation of the current path will be described below with reference to FIG. In the comparator Q2, when the detection voltage Vr is larger than the reference voltage Vref, that is, when the power supply current Iac flowing through the LED lighting device 101 is large, the transistor Tr of the output unit of the comparator Q2 is turned on and the output of the comparator Q2 becomes low level. . When the detection voltage Vr is lower than the reference voltage Vref, that is, when the power supply current Iac flowing through the LED lighting device 101 is small, the transistor Tr of the output unit of the comparator Q2 is turned off, and the output of the comparator Q2 becomes high level. When the transistor Tr is on (Vref <Vr), the gate voltage of the switching element Q1 becomes the ground level (that is, 0). As a result, the switching element Q1 is turned off, the current path is closed, and the compensation current Ir does not flow. On the other hand, when the transistor Tr is off (Vref ≧ Vr), a voltage is applied to the gate of the switching element Q1 to turn on the switching element Q1. As a result, a current path is opened to allow the compensation current Ir to flow.

  By setting the reference voltage Vref input to the non-inverting input terminal of the comparator Q2 to a voltage larger than the voltage VR2 (min) corresponding to the holding current (power supply current Iac = holding current) of the triac 103, the power supply current Iac By flowing the compensation current Ir to the auxiliary circuit 109 when the corresponding voltage VR2 becomes smaller than the reference voltage Vref, it is possible to prevent the current flowing through the triac from becoming smaller than the holding current.

  When the power supply current Iac supplied to the LED lighting device 101 is large, the current path is closed, so that the compensation current Ir does not flow, and wasteful power consumption can be suppressed.

If the compensation current Ir is larger than the holding current, the operation of the triac 103 can be stabilized. However, if the compensation current Ir is too large, power consumption increases. Further, if the compensation current Ir changes when approaching the same value as the holding current, the operation of the triac 103 may become unstable when the compensation current Ir fluctuates. Therefore, in the power supply circuit shown in FIG. 1, when the magnitude of the compensation current Ir is set to twice the holding current in consideration of power consumption and current fluctuation, the triac 103 can be stably operated, and Power consumption could also be suppressed.
Similarly, from the viewpoint of stable operation of the triac 103 and power consumption suppression, the reference voltage Vref is assumed to be about twice as large as the voltage VR2 (min) corresponding to the holding current of the triac 103.
Of course, the margin between Vref and VR2 (min) can be appropriately set according to the application and purpose of the LED lighting device.

  FIG. 2 is a timing chart showing the operation of the element shown in FIG. When the triac 103 is turned on, the power supply current Iac increases in order to charge the capacitor C. When the charging of the capacitor C is completed, the power supply current Iac decreases once. However, since the current supply from the capacitor C to the DC-DC converter 107 starts, the power supply current Iac starts to increase. Similarly, the detection voltage Vr indicating the value of the power supply current Iac increases when the triac 103 is turned on, decreases once, and then increases. Thus, immediately after switching the triac 103 from off to on, the power supply current, that is, the current flowing through the triac 103 oscillates and becomes unstable.

  When the detection voltage Vr falls below the reference voltage Vref, the transistor Tr at the output of the comparator Q2 is turned off, and the switching element Q1 is turned on. When the switching element Q1 is turned on, the current path is opened, the compensation current Ir is supplied to the triac 103, and the triac 103 is kept on. On the other hand, when the detection voltage Vr exceeds the reference voltage Vref, the transistor Tr at the output of the comparator Q2 is turned on, and the switching element Q1 is turned off. The switching element Q1 is turned off, and the energization of the compensation current Ir is stopped.

  According to the above embodiment, on / off of the current path in the auxiliary circuit 109 is controlled based on the value of the power supply current Iac flowing from the triac 103 to the diode bridge 105. Therefore, before the power supply current Iac becomes equal to or lower than the holding current of the triac 103, that is, when the power supply current Iac becomes equal to or lower than a threshold value larger than the holding current, a compensation current Ir larger than the holding current is caused to flow to the current path. It is possible to prevent the triac 103 in a state where it should be kept from being turned off unexpectedly. Then, when the power supply current Iac exceeds the threshold value, the possibility that the triac 103 is unexpectedly turned off becomes extremely small, and therefore the flow of the compensation current Ir to the current path is stopped. Thereby, useless power consumption can be suppressed.

  FIG. 3 is a diagram showing an LED lighting device according to another embodiment of the present invention, and FIG. 4 is a timing chart showing the operation of the element shown in FIG. In FIG. 3, the same parts as those of the embodiment shown in FIG. The difference from FIG. 1 is that the auxiliary circuit 209 has a current path through which a compensation current Ir exceeding the holding current flows from the triac 103 for a predetermined time immediately after the triac 103 is turned on. In the figure, R1 is a resistor for determining the magnitude of the compensation current Ir, Q1 is a switching element for controlling the current flowing in the current path, Q2 is a switching element for controlling on / off of Q1, and R2 and C1 are switching elements Q2. A delay circuit for controlling on / off of the circuit is configured. R4 is the base resistance of the switching element Q2, R3 and R6 are the gate resistance of the switching element Q1, R5 is the gate pull-down resistance of the switching element Q2, and ZD1 is a Zener diode that blocks noise to the switching element Q2.

Immediately after the triac 103 is turned on, since the base current of the switching element Q2 is delayed by the resistor R2 and the capacitor C1, the switching element Q2 remains off.
As a result, since the voltage from the control circuit 107 is applied to the gate of the switching element Q1, the switching element Q1 is kept on, and the compensation current Ir flows through the diode D1 or D2. The magnitude of the compensation current Ir is defined by the impedance of the resistor R1.
Immediately after the triac 103 is turned on, a charging current also flows through the capacitor C. Therefore, the total of the power source current Iac and the compensation current Ir is applied to the triac 103.
When charging of the capacitor C is completed, the power supply current Iac once decreases, but the compensation current Ir is still supplied to the triac 103.

When the charging of the capacitor C is completed, the current supply to the DC-DC converter 107 starts, so that a current exceeding the holding current flows through the triac 103 stably. In this state, the compensation current Ir becomes unnecessary. After the triac 103 is turned on, a time T1 from when the charging of the capacitor C is completed until a stable current starts to flow to the DC-DC converter 107 is predicted in advance. After that time, the switching element Q1 is turned off and the compensation current Ir Cut off the current path. In order to turn off the switching element Q1, the switching element Q2 is turned on and the gate voltage of the switching element Q1 is set to the ground level, that is, zero.
When the triac 103 is turned on and becomes a voltage exceeding the threshold voltage of the Zener diode ZD1, alternating current is applied to a delay circuit composed of the resistor R2 and the capacitor C1, and after a time corresponding to the time constant, the switching element Q2 The gate voltage goes high. As a result, the switching element Q2 is turned on, so that the gate voltage of the switching element Q1 is at a low level, that is, the switching element Q1 is turned off. By making the time constant of the delay circuit coincide with the time T1 until the stable current starts to flow, the energization time of the compensation current Ir can be minimized.

  If the compensation current Ir is larger than the holding current, the operation of the triac 103 can be stabilized. However, if the compensation current Ir is too large, power consumption increases. Further, if the compensation current Ir changes when approaching the same value as the holding current, the operation of the triac 103 may become unstable when the compensation current Ir fluctuates. Therefore, in the power supply circuit shown in FIG. 3, when the magnitude of the compensation current Ir is set to twice the holding current in consideration of power consumption and current fluctuation, the triac 103 can operate stably, and Power consumption could also be suppressed.

  In the present embodiment, the current source of the resistor R1 is obtained from the AC side of the diode bridge 105. This is because, if acquired from the DC side of the diode bridge 105, after the charging of the capacitor C is completed, the DC side voltage becomes higher than the AC side voltage, the diode bridge 105 is turned off, and no current is supplied to the resistor R1.

  According to the above embodiment, the compensation current Ir exceeding the holding current flows from the triac 103 through the current path for a predetermined time immediately after the triac 103 is switched on. Immediately after the triac 103 is switched on, the power supply current Iac becomes unstable (vibrates), and there is a possibility that the value becomes equal to or less than the holding current of the triac 103. However, by supplying the compensation current Ir to the current path of the auxiliary circuit 209 while the power supply current Iac is unstable, it is possible to prevent the triac 103 that should be kept on from being turned off unexpectedly. After the power supply current Iac is stabilized after a certain period of time, the flow of the compensation current Ir to the current path is stopped. Thereby, useless power consumption can be suppressed.

  The present invention is not limited to the description of the embodiments and examples of the invention described above. Various modifications may be included in the present invention as long as those skilled in the art can easily conceive without departing from the description of the scope of claims.

101 LED Lighting Device 103 Triac 105 Diode Bridge 107 DC-DC Converter 109, 209 Auxiliary Circuit

Claims (3)

A power supply circuit for an LED lighting device including a triac, a rectifier circuit, and a voltage adjustment circuit,
The rectifier circuit and the auxiliary circuit are connected in parallel to the triac,
The auxiliary circuit includes a current path for passing a current exceeding the holding current from the TRIAC, a detection unit for detecting a power supply current flowing through the rectifier circuit, and the power supply current when the power supply current falls below a threshold value greater than the holding current of the TRIAC. And a control unit that opens the current path and closes the current path when the power supply current exceeds the threshold value. A power supply circuit for an LED lighting device including a triac, a rectifier circuit, and a voltage adjustment circuit,
The rectifier circuit and the auxiliary circuit are connected in parallel to the triac,
The power supply circuit for an LED lighting device, wherein the auxiliary circuit includes a current path through which a current exceeding the holding current flows from the triac for a predetermined time immediately after the triac is turned on.   An LED lighting device equipped with the power supply circuit for the LED lighting device according to claim 1.

Images