JPH089779Y2 - Phase control device - Google Patents

Description

TECHNICAL FIELD The present invention relates to a phase control device used in, for example, a dimmer.

[Background technology]

Conventionally, a generally used phase control device has a power switch 2 at both ends of an AC power supply 1 as shown in FIG.
It is configured by connecting a series circuit of a phase control unit 3 and an incandescent lamp 4 which is a load via a phase control unit 3 which is connected in parallel to a noise prevention LC filter 5, a phase control element TRIAC 6 and a TRIAC 6. The relaxation oscillation circuit 10 is formed by including a variable resistor 7 and a capacitor 8 which are provided between the capacitor 8 and the triac 6 and inserting a voltage response element 9 such as SBS between them. Such a device has a variable resistor 7 and a capacitor 8 when the power switch 2 is turned on.
The triac 6 is turned on at a desired phase according to the time constant of the series circuit, and the incandescent lamp 4 can be turned on in a desired output state by adjusting the variable resistor 7.
As soon as the power switch 2 is turned on, a voltage sufficient to obtain a desired output is applied to the device, so that a large inrush current may flow and an accident such as a lamp disconnection may occur.

On the other hand, there is one in which a soft start circuit 11 is provided in the phase controller 3 as shown in FIG. The soft start circuit 11 is formed by a parallel circuit of a diode bridge 12 connected to both ends of the trigger capacitor 8 of the relaxation oscillator circuit 10, a capacitor 13 connected to the DC side of the diode bridge 12, and a discharge resistor 14. After the power switch 2 is turned on, the capacitor 13 is connected in parallel with the capacitor 8 for a predetermined time to increase the time constant of the relaxation oscillator circuit 10, and the ON phase of the triac 6 is advanced as the capacitor 13 is charged. By finally reaching the desired phase, immediately after the switch 2 is turned on, the section of the triac 6, that is, the output of the incandescent lamp 4 is sufficiently narrowed down so that the output gradually increases over a predetermined time. In addition, the inrush current to the incandescent lamp 4 is eliminated, so that the lamp life is extended.

The conventional phase control device is configured as described above, for example, but if a short circuit failure occurs in the incandescent lamp 4 that is a load, a large current may flow into the triac 6 and be destroyed. Even if the soft start circuit 11 is provided as shown in FIG. 5, a large current still flows.

[Purpose of device]

The present invention has been made in view of the above-mentioned drawbacks, and provides a phase control device capable of reliably performing protection of a phase control element when a load is short-circuited with a simple configuration.

[Disclosure of device]

The present invention achieves the above object by providing a current detection circuit in series with the phase control element and resetting the soft start circuit when the current detection circuit detects a predetermined current. The present invention will be described based on the following.

FIG. 1 shows an embodiment of the present invention, in which a current detection circuit 15 for detecting the current flowing through the triac 6 is provided. The current detection circuit 15 resets the current detection current transformer 16 inserted in series with the triac 6 and the reset switch 18 for resetting the soft start circuit 11 when the current transformer 16 detects a current more than a predetermined value. And a control circuit 17 for controlling it. The reset switch 18 is connected in parallel with the capacitor 13 of the soft start circuit 11.

The operation of this embodiment is as shown in the flowchart of FIG. That is, in the normal case, when the power switch 2 is turned on, the capacitors 8 and 13 are charged through the variable resistor 7, and immediately after the switch is turned on, the on-phase of the triac 6 is delayed, but the capacitor 13 is gradually charged. As a result, the voltage across the capacitor 8 reaches the breakover voltage of the voltage response element 9 in the early phase of every half cycle, and the ON phase of the triac 6 advances, so that the incandescent lamp 4
The output light of is dark immediately after the power is turned on, and then gradually becomes brighter to a desired output. However, when the load is short-circuited, the current has already increased during the soft start, so the current transformer 16 detects this current and turns on the reset switch 18, which causes the capacitor 13 to discharge and the device to turn on again. Since the state immediately after that is reset and the above soft start operation is repeated thereafter, the current flowing through the triac 6 does not become so large and the triac 6 and the like are not destroyed.

Since the soft start circuit 11 is reset by detecting the current in this way, it is possible to reliably and quickly detect the gradually increasing current until it reaches a value that causes trouble, and prevent it from increasing further. , Circuit protection can be achieved sufficiently.

FIG. 3 shows a concrete embodiment of the present invention, in which the current detection circuit 15 is composed of a current transformer 16 and a diode bridge 1.
9, a resistor 20 connected to both ends of the DC side, and a voltage responsive element 21 such as SBS that is turned on when the voltage across the resistor 20 reaches a predetermined value.
Is a transistor to which a base current is supplied via the voltage responsive element 21. In the present embodiment, if the breakover voltage of the voltage responsive element 21 is set to be larger than the voltage across the resistor 20 when the load is normal and the maximum output is under output, only when an abnormality such as a load short circuit occurs. It can be detected and can protect the triac 6 and the like from destruction or deterioration.

In the above embodiment, the dimming of the incandescent lamp is described as an example, but any type may be used as long as it controls the load and the phase of the load, and the trigger circuit and the soft start circuit of the phase control element, and Needless to say, the configuration of the current detection circuit is not limited to the above embodiment.

(Effect of the Invention) As described above, in the present invention, since the soft start circuit of the phase control element is reset by detecting the abnormal current, a relatively small current until the phase control element is destroyed or significantly deteriorated. An abnormality such as a load short circuit could be detected at the time of, and a reliable and quick protection operation could be obtained with a simple configuration.

[Brief description of drawings]

1 is a circuit diagram of an embodiment of the present invention, FIG. 2 is a flow chart for explaining the operation of the same, FIG. 3 is a concrete circuit diagram of the same,
4 and 5 are circuit diagrams showing different conventional examples. 4 ... Incandescent lamp, 6 ... TRIAC, 11 ... Soft start circuit, 15 ... Current detection circuit, 18 ... Reset switch.

Claims (1)

[Scope of utility model registration request] 1. A phase control device in which a phase control element and an incandescent lamp load are connected in series at both ends of an AC power supply for gradually advancing the ON phase of the phase control element with time immediately after the power is turned on. A soft start circuit consisting of a relaxation oscillation circuit and a semiconductor switching element such as a triac whose conduction phase angle is controlled by this is provided, and a current detection circuit that detects and outputs a predetermined current or more in series with the phase control element is inserted. A phase control device, wherein the relaxation oscillation circuit is returned to an initial state by the output of the current detection circuit and the soft start circuit is reset.