JP2007287635A - Phase control circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a phase control circuit having an excellent property of eliminating high-frequency noises and inexpensive, simple circuit construction. <P>SOLUTION: The circuit comprises: triacs TR1 and TR2 for phase-controlling an alternating-current supply voltage; and inductors L1 and L2 serially connected to these triacs TR1 and TR2, respectively, with L1>L2, in which at first the triac TR1 is brought into conduction at the start time of energization by the phase control. Immediately after that, the triac TR2 is also brought into conduction, so as to suppress heat generation possibly caused by the inductors by eliminating high-frequency noises using the inductor L1 at the start time of conduction and subsequently flowing much of current into the inductor L2. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a phase control circuit used for a dimmer or the like.

  A phase control circuit used for a dimmer or the like performs phase control of a current (AC) supplied to a load by connecting a phase control element in series with a load and further connecting an inductor (choke) in series. . The inductor has a function of removing high frequency noise (harmonic component) generated at the start of conduction by the phase control element, and it is necessary to use a relatively large inductor in order to remove sufficient high frequency noise. However, in the configuration in which a large inductor is connected to the load, high-frequency noise can be removed, but an increase in size cannot be avoided, and measures against temperature rise are required.

In order to solve this problem, for example, as disclosed in Patent Document 1, there is one in which the slope control is performed so that the slope of the load supply current at the start of energization by the phase control element becomes gentle. Since high-frequency noise is generated in a large amount and at a high level when the load current changes suddenly, the load current at the start of energization by the phase control element is controlled so that the load current changes slowly. Can be reduced.
Japanese Patent Laid-Open No. 10-284263

  However, the device disclosed in Patent Document 1 requires a special circuit configuration for tilt control, and thus it is inevitable to increase the cost. In addition, the tilt section is set before the energization start timing by phase control. Therefore, there is a problem that phase control cannot be performed accurately. Furthermore, since the inductor is not connected in series with the load, there is a possibility that a steep current change is directly applied to the phase control element at the start of energization or when the load is disconnected, leading to the destruction of the element.

  An object of the present invention is to provide a phase control circuit that is excellent in high-frequency noise removal characteristics and has a low-cost and simple circuit configuration.

  The phase control circuit according to the present invention includes an inductor and a phase control element connected in series with a load, and the inductor is the first in the phase control circuit that suppresses high-frequency noise generated more frequently when the energization is started by the phase control element. The first inductor L1 and the second inductor L2 are connected in parallel. The first inductor L1 has a large inductance value, and the second inductor L2 has a small inductance value.

The phase control element includes a first phase control element connected to the first inductor L1 and a second phase control element connected to the second inductor L2.
At the start of energization by phase control, the first phase control element is first turned on, and immediately after that, the second phase control element is turned on.

  With the configuration described above, the generation of high-frequency noise is suppressed by energizing the first inductor L1 having a large L at the start of energization of the phase control (at the rise of the current). By energizing the second inductor L2 having a small L, most of the current flows through the second inductor L2. Since the resistance value R1 of the first inductor L1 is larger than the resistance value R2 of the second inductor L2, after the second inductor L2 is energized, the magnitude of I ^ 2 * R (the amount of generated heat) is also so much. Don't get big.

  Therefore, it is possible to suppress high-frequency noise that is most likely to occur at the start of energization (at the rise of current), and to suppress an increase in temperature because the amount of heat generated by a steady current does not increase. The first inductor L1 does not need to be large because a large current flows only at the start of energization and only a small current flows thereafter.

  According to the present invention, high-frequency noise can be effectively suppressed and a temperature rise can be suppressed, so that a heat dissipation countermeasure component is unnecessary, and the first inductor L1 does not need to be increased in size, thereby reducing the size of the entire circuit. And cost reduction.

  FIG. 1 is a circuit diagram of a phase control circuit according to an embodiment of the present invention.

  In FIG. 1, a load LD such as an incandescent lamp is connected to an input terminal of a commercial power supply AC of 50 Hz or 60 Hz. Further, a triac TR1 as a first phase control element and a second phase control element are connected to the load LD. The triac TR2 is connected, the triac TR1 is connected to the inductor L1 as the first inductor, and the triac TR2 is connected to the inductor L2 as the second inductor. The series circuit of the triac TR1 and the inductor L1 is connected in parallel to the series circuit of the triac TR2 and the inductor L2. Further, one end of the inductor L1 and the inductor L2 are connected in common, and a capacitor C is connected between the one end and the load LD.

  The control unit CT outputs a trigger signal to the gate terminals of the triacs TR1 and TR2, and controls the start of energization thereof.

  The inductance value L of the inductor L1 is larger than the inductance value L of the inductor L2 (L1> L2). In this example, L1 = 353 μH and L2 = 8.8 μH are set. At the start of energization, the controller CT first outputs a trigger signal to the inductor L1, and immediately thereafter outputs a trigger signal to the inductor L2. The delay time is about 10 μS. FIG. 2 shows a delay in energization start timing of the triacs TR1 and TR2. Time t1 is the energization start timing, the triac TR1 is turned on at this time t1, and the triac TR2 is turned on at time t1 + Δt delayed by the delay time Δt. The triacs TR1 and TR2 remain on until the time T (the time from when Δt has elapsed until the current zero crosses) has elapsed. Therefore, when the current rises at time t1, the current flows only in the inductor L1, and the high frequency noise generated at that time is sufficiently absorbed by the inductor L1 having a large L. Further, after the delay time Δt has elapsed, the triac TR2 is also turned on. The inductor L2 has a smaller R (resistance value) than the inductor L1, since L is smaller. Therefore, when the triac TR2 is turned on, most of the current flows through the triac TR2 and the small inductor L2 until the latter half cycle elapses (until the current crosses zero). Therefore, heat generation is small and heat generation by the entire inductor can be suppressed. The inductor L2 connected to the triac TR2 removes some high-frequency noise generated in the period T, and prevents a sharp current change from being applied to the triac TR2 at the start of energization or when the load is disconnected. Therefore, it is possible to prevent the triac TR2 from being destroyed due to a steep current change.

  In the above embodiment, L1 = 353 μH and L2 = 8.8 μH are set. However, in order to sufficiently realize the functions of the inductors L1 and L2, it is desirable that L1 is 10 times or more of L2. In the above embodiment, the delay time Δt is about 10 μS, but it is desirable to set it to an appropriate value by experiment.

1 is a circuit diagram of a phase control circuit according to an embodiment of the present invention. It is an operation | movement waveform diagram of a phase control circuit.

Claims (1)

In a phase control circuit that includes a phase control element that performs phase control of an AC power supply voltage, and an inductor that is connected in series to the phase control element, and supplies an AC power supply voltage phase-controlled by the phase control element to a load.
The inductor includes a first inductor L1 and a second inductor L2 (L1> L2) having one end connected in common,
The phase control element includes a first phase control element connected to the first inductor L1 and a second phase control element connected to the second inductor L2.
A phase control circuit characterized in that at the start of energization by phase control, the first phase control element is first turned on, and immediately after that, the second phase control element is turned on.

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