JP4379236B2 - Light control device - Google Patents

Description

  The present invention relates to a light control device that adjusts the illuminance of a light source such as an incandescent bulb or LED.

  Conventionally, a phase control dimmer is often used as means for dimming an incandescent lamp. Phase control dimmers are generally connected in series between a commercial AC power supply and an incandescent lamp load, and control the phase angle (triggering phase angle) at which the triac, which is a switching element inside the dimmer, turns on. In this way, the effective value of the commercial AC voltage supplied to the incandescent lamp load is varied to control the dimming of the incandescent lamp load. FIG. 6 shows operation waveforms of the phase control dimmer. In an incandescent lamp load, since the power supply voltage and the load current are in phase, the load current can be turned off if it is turned off at the zero cross point of the power supply.

  As a lighting circuit for a low-voltage halogen bulb, an electronic transformer is well known as a means for converting a commercial AC voltage into a high frequency of several tens of KHz and further converting it into a high-frequency low voltage of 12 V using a step-down transformer. It is also a general technique to perform dimming control by combining an electronic transformer for a low-voltage halogen bulb with the above-described phase control type dimmer. FIG. 7 shows the circuit configuration when the phase control dimmer and the electronic transformer are used in combination. In the figure, 1 is an AC power source, 2 is a phase control dimmer, 3 is an electronic transformer, and 4 is a load. In this configuration, the filter capacitor C1 is connected in parallel to the series connection of the triac Q1 which is a bidirectional switch and the filter choke L1, and the noise prevention capacitor C2 on the electronic transformer side is further connected in series. When the flowing current is used at a commercial frequency, it may lead to the phase of the power supply voltage due to the influence of the capacitive element.

  The circuit operation will be described with reference to FIG. Here, as the phase control signal, a DC trigger method (also referred to as a solid trigger method) in which the gate voltage is continuously applied during the turn-on period is used instead of the pulse trigger method in which the gate voltage is applied only at the turn-on time. The triac Q1 is an element that turns off when the phase control signal is turned off and then becomes a current equal to or lower than the holding current. However, the current that already flows in the triac Q1 at the timing when the phase control signal is turned off due to the influence of the phase advance current described above. Is commutated across the zero cross point, and when the current exceeding the holding current flows at the moment when the phase control signal is turned off, the TRIAC Q1 cannot be turned off, so that the current becomes zero over the next half cycle of the AC power supply. Until that time, the triac Q1 remains on.

  Therefore, conventionally, in order to solve this problem, as shown in FIG. 9, time adjustment is performed so that the phase control signal is turned off before the current flowing in the triac crosses the zero cross point at the design stage. The problem of light operation was avoided. In the figure, the triac Q1 cannot be turned off even if the phase control signal is turned off at the timing t1, but the triac Q1 can be turned off by turning off the phase control signal at the timing t2.

Patent Document 1 discloses a circuit in which a resistance element is connected in parallel with a load in phase control dimming of an incandescent lamp. However, this resistance element is not a resistance element for countermeasures against a phase advance current.
Japanese Patent Laid-Open No. 10-284263

  If the time is set at the design stage so that the current flowing in the triac crosses the zero cross point before the triac phase control signal is turned off as in the conventional example shown in FIG. 9, for example, the same dimmer When a plurality of loads are to be dimmed, a plurality of noise prevention capacitors are connected in parallel, so that the capacitor current increases or decreases according to the number of connected loads as shown in FIG. For this reason, it is difficult to optimally set the timing tx for turning off the phase control signal. If the capacitor current is one load, even if the triac current is less than the holding current, if the capacitor currents of multiple loads are superimposed, as shown in X of FIG. The triac current exceeds the holding current, and if the number of connected devices exceeds a certain number, the triac cannot be controlled due to the influence of the phase advance current.

  For example, when a low wattage load such as an LED is connected to this phenomenon, the load current is small. In addition to the problem of the number of connected loads, it is necessary to set the timing for turning off the triac from the zero cross point of the power supply voltage to a time with some allowance at the design stage, considering the variation in the components of the light control device. Therefore, there arises a problem that the dimming lower limit control range in the voltage phase control is narrowed. This is an important issue with respect to dimming performance, especially when dimming low watt loads such as LED loads.

  The present invention eliminates the inconveniences as described above, and can avoid control problems near the lower limit of dimming without considering the type of load, the number of connected units, or variations in parts in advance, and an appropriate dimming control range. It is an issue to be able to secure.

In the present invention, in order to solve the above-mentioned problem, as shown in FIG. 1, a series circuit of a bidirectional switching element Q1 having a self-holding function and an inductive element L1 is connected to lighting loads 41 and 42 and AC. Connected in parallel with the series circuit of the power source 1 to form a closed circuit, detects the voltage phase of the AC power source 1, and makes the on-timing of the bidirectional switching element Q1 variable so that the effective power to the lighting loads 41 and 42 The phase control circuit 23 is a DC trigger type phase control circuit that continuously applies a drive voltage during the ON period of the bidirectional switching element Q1, and includes a lighting load 41, when the 42 and capacitive element is connected in parallel, as shown in FIG. 3, the switching element current becomes less holding current at turn-off of the bidirectional switching element Q1 The capacitive element resistance element flowing a current to cancel the phase advance current flowing in the Ra, R1 to, R2, and R3 connected in parallel with the lighting load 41, the lighting load 41, 42 connected in parallel with the resistive element Switch elements S1, S2, S3 are inserted in series with R1, R2, R3, and the circuit in which the resistance elements R1, R2, R3 and the switch elements S1, S2, S3 are connected in series is the lighting loads 41, 42. Are connected in parallel with each other.

  According to the present invention, it is possible to avoid a control failure near the dimming lower limit without considering in advance the type of load, the number of connected units, or variations in parts. In addition, since the timing for turning off the driving voltage of the bidirectional switching element can be determined without detecting the zero cross point of the switching current, the voltage phase of the AC power supply is detected without using a current detection means such as a current transformer. Dimming operation can be performed by phase control.

( Prerequisite configuration 1)
FIG. 1 shows a circuit diagram of Configuration 1 which is a premise of the present invention. The AC power supply 1 is connected in parallel with a noise preventing capacitor C1. One end of the capacitor C1 is connected to one end of the AC input terminal of the rectifier circuit 21, and the other end is connected to the other end of the AC input terminal of the rectifier circuit 21 via the fuse F1. A surge absorbing element ZNR is connected in parallel to both ends of the AC input terminal of the rectifier circuit 21, and a smoothing capacitor C3 is connected in parallel to both ends of the DC output terminal. The DC voltage of the capacitor C 3 is smoothed to a stable DC low voltage by the switching power supply 22 and supplied to the control circuit 23. The control circuit 23 includes a microcomputer and its peripheral circuits, and outputs a phase control signal as a drive signal for the phototriac Q4. Here, a DC trigger method (also referred to as a solid trigger method) is used as a phase control signal, not a pulse trigger method that applies a drive voltage only at turn-on, but a drive voltage that is continuously applied during the turn-on period. The control circuit 23 detects a zero cross point of the AC power supply 1 by a zero cross detection circuit (not shown), and can output a phase control signal synchronized with the power supply cycle of the AC power supply 1.

  In the triac Q1 as a bidirectional switching element for phase control, a phototriac Q4 and a resistance voltage dividing circuit are connected between main electrodes, and an output of the resistance voltage dividing circuit is applied to a gate electrode. A noise preventing capacitor is connected in parallel between the gate electrode and one of the main electrodes. One end of the filter choke L1 is connected to the other main electrode of the triac Q1, and the other end of the filter choke L1 is connected to one end of the AC power source 1 via a noise preventing capacitor C2. The other end of the AC power source 1 is connected to the one main electrode of the triac Q1, and the AC power source 1, the triac Q1, the filter choke L1, and the capacitor C2 constitute a series closed circuit. Both ends of the capacitor C2 serve as output ends of the phase control dimmer, and loads 41 and 42 are connected in parallel between the output ends. Here, each of the loads 41 and 42 is a load having a noise prevention capacitor at the input section. When a large number of the loads 41 and 42 are connected in parallel, a phase advance current naturally flows. Therefore, a phase advance countermeasure resistance element Ra for relaxing the phase advance current is connected in parallel with the capacitor C2. Thereby, the influence of the phase advance current resulting from the capacitive property of the load can be mitigated, and malfunction can be prevented.

  Next, circuit operation will be described. 2A and 2B are waveform diagrams for explaining the operation of the present invention. FIG. 2A shows an operation before the resistor element Ra is connected, and FIG. 2B shows an operation after the resistor element Ra is connected. Before the resistor element Ra is connected, the combined current of the load current and the leading current becomes a triac current. Therefore, if the leading current due to the capacitor C2 turns negative at the timing when the triac Q1 is turned off, the triac current is It will decrease accordingly. Therefore, if the number of connected loads 41, 42,... With capacitors connected to the input section increases and the phase advance current increases, the triac current will be negatively commutated when the triac Q1 is turned off. When this current exceeds the holding current of the element, the dimming operation is not performed normally, and the triac Q1 continues to be turned on over the next half cycle of the power supply cycle. When the resistor element Ra is connected in this manner, the current flowing through the triac Q1 is increased by the amount of current flowing through the resistor element Ra. Therefore, at the timing when the triac Q1 is turned off, the current that is negatively decreased by the phase advance current can be compensated. If a positive current is supplied, since the positive current still remains at the timing when the triac Q1 is turned off, the triac Q1 can be normally controlled to be turned off.

  In addition, even when the load having the phase advance element that can be connected to the light control device of the present invention is connected in the maximum number and the combined capacity of the capacitor becomes the maximum, the resistance element Ra only cancels the phase advance current due to the capacitor. It is necessary to set to the resistance value.

  This method detects the current of the triac Q1 and does not use a means for turning off the phase control signal before the zero cross point, but simply by connecting the resistor element Ra, the off point of the phase control is Since the voltage can be close to the zero cross point, the dimming range in which the dimming operation can be normally performed can be expanded in the dimming lower limit direction.

(Embodiment 1 )
A circuit diagram of Embodiment 1 of the present invention is shown in FIG. Since the main circuit and its peripheral circuits are the same as the precondition 1, description thereof is omitted. The difference is that a plurality of circuits in which switching elements and resistance elements are connected in series in parallel with the load are connected in parallel. S1, S2, and S3 are switch elements, and R1, R2, and R3 are resistance elements. Here, the resistance values of the built-in resistor element Ra and the external resistor elements R1, R2, and R3 may be the same, but the relationship of 1/2, 1/4, 1/8,. In the latter case, the resistance value can be made variable in multiple steps.

In the premise configuration 1, since it is necessary to set a resistance value for canceling the influence of the phase advance current of all loads that can be connected to the dimmer, it is very ineffective as power consumption. However, the loss of heat generation is also disadvantageous in terms of design, but it is possible to connect the switch elements S1, S2, S3,. If the user can arbitrarily switch the resistance value according to the number and type of loads to be applied, it is not necessary to waste more power than necessary. Further, it is advantageous from the viewpoint of thermal design of the light control device 2.

( Assumption 2 )
FIG. 4 shows a circuit diagram of Configuration 2 which is a premise of the present invention. Since the main circuit and its peripheral circuits are the same as the precondition 1, description thereof is omitted. The difference is that the variable resistance element VR is connected in parallel with the load.

In the premise configuration 1, since it is necessary to set a resistance value for canceling the influence of the phase advance current of all loads that can be connected to the dimmer, it is very ineffective as power consumption. However, it is disadvantageous in terms of design because the heat loss is also large, but by making the variable resistance element VR adjustable outside the dimmer as in this circuit, the number of connected loads If the user can arbitrarily set the resistance value according to the type, it is not necessary to waste more power than necessary. Further, it is advantageous from the viewpoint of thermal design of the light control device 2.

(Embodiment 2 )
The second embodiment of the present invention shown in FIG. Since the circuit configuration is the same as that of the first embodiment, description thereof is omitted. The difference is that, in the first embodiment, as the resistive elements R1, R2, and R3, resistive load light sources B1, B2, and B3 connected to the outside of the dimmer 2 are used, for example, incandescent bulbs and bean bulbs. It was a point. Since these are arranged outside the dimmer 2, the thermal design in the circuit is advantageously performed. In addition, an external light source can be used as an indicator for confirming the phase advance level or the dimming level. Specifically, when the current dimming level is known, the brightness of the incandescent bulb itself becomes an index indicating the dimming level. As for the phase advance level, if the degree of phase advance is large, it is necessary to increase the current of the triac Q1 by connecting many incandescent bulbs in parallel. Can be judged. Further, as described above, illumination as an indicator for determining the light control level and the phase advance level can also be used as a light source. For example, it may be used as an auxiliary light source in a dark machine room during the day. In this way, the electric power for phase advance measures can be effectively used for different purposes.

It is a circuit diagram of composition 1 which is a premise of the present invention. It is a wave form diagram for operation | movement description of the structure 1 used as the premise of this invention. It is a circuit diagram of Embodiment 1 of the present invention. It is a circuit diagram of the structure 2 used as the premise of this invention. It is a circuit diagram of Embodiment 2 of the present invention. It is a wave form diagram for the principle explanation of the conventional phase control type light control device. FIG. 6 is a circuit diagram of Conventional Example 1. It is a wave form diagram for demonstrating the problem of the prior art example 1. FIG. FIG. 10 is a waveform diagram for explaining the operation of Conventional Example 2. It is a wave form diagram for demonstrating the problem of the prior art example 2. FIG.

1 AC power supply Q1 Bidirectional switching element (Triac)
L1 Filter choke Ra Resistance element for phase advance current C2 Noise prevention capacitor

Claims (2)

A series circuit of a bidirectional switching element and an inductive element having a self-holding function is connected in parallel with a series circuit of a lighting load and an AC power supply to form a closed circuit, and the voltage phase of the AC power supply is detected to perform bidirectional switching. In a dimming device including a phase control circuit that makes the effective power to the illumination load variable by changing the ON timing of the element, the phase control circuit is a DC that continues to provide a drive voltage during the ON period of the bidirectional switching element. This is a trigger-type phase control circuit, and when a capacitive element is connected in parallel with the lighting load, the flow of the switching element current so that the switching element current becomes equal to or less than the holding current when the bidirectional switching element is turned off. connecting a resistor element to flow a current that cancels the phase current in parallel with the lighting load, the lighting load resistor connected in series with the switch element in parallel There is inserted, the resistive element and it features a dimming device is circuit connected to switching elements in series that is a plurality connected in parallel to the lighting load. Dimming device according to claim 1, wherein the incandescent load is connected instead of the resistor element.

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