JPH0522358B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a dimming control device that suppresses inrush current when power is applied to a lamp load.

Configuration of conventional example and its problems A conventional dimming control device has a dimming control circuit that generates a pulse in each half cycle of AC power, and AC power is supplied through a branch line that is separate from this dimming control circuit. The lamp circuit has a lamp that is turned on by a semiconductor switch means that is ignited by the pulse, and is used in supermarkets and various stores to save power. In such a dimming control device, even if a soft start circuit is built into the dimming control circuit, if AC power is turned on to the dimming control circuit first, the soft start function will have already ended. If AC power is later applied to the lamp circuit from a branch line of another system, the in-rush current may shorten the life of the lamp or semiconductor switch means, especially if the dimming control circuit is functioning in almost all phases. There have been problems such as shortening or disconnection of the circuit breaker which is usually installed in the lamp circuit.

OBJECTS OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems and maintain the soft start function of suppressing the lamp inrush current even when the power is turned on.

Structure of the Invention In order to achieve the above-mentioned object, the present invention is based on the above-described structure, and provides a detection circuit that detects that AC power is applied to the lamp circuit, and when the detection circuit operates, a soft start circuit is activated. and switching means for maintaining the function of the soft start circuit in the dimming control circuit.

DESCRIPTION OF EMBODIMENTS Next, embodiments of the present invention will be described with reference to the drawings.

Reference numeral 1 denotes a main line of an AC power source 2, from which the AC power source 2 is supplied to a regulated DC power source DC via a branch line 3. 4 is a dimming control circuit, which controls the DC power supply DC.
Pulse generation circuit with almost arbitrary phase given variable DC voltage of 0 to 10V generated at VDC terminal
Semiconductor switch means T consisting of a triax that generates a pulse in PG and passes it through a pulse transformer PT.
ignite. The lamp circuit 5 has the semiconductor switch means T and a lamp L lit by the semiconductor switch means T, and is supplied with AC power 2 through a branch line 6 which is separate from the dimming control circuit 4. 7 is a detection circuit for detecting that the AC power source 2 is applied to the branch line 6, that is, the lamp circuit 5, and the light emitting element _P1 made of a light emitting diode is made of a light receiving element made of a phototransistor at the input of the dimming control circuit 4. It is optically coupled to the switch means _P2 , and upon activation of the detection circuit 7, a soft start circuit, which will be described later, in the dimming control circuit 4 is activated.
SDC of the DC power supply DC is a fixed voltage terminal that supplies power pressure to the dimming control circuit 4, and SYC
is a synchronization terminal for synchronizing the pulse generation of the dimming control circuit 4 with the AC power supply 2. BR ₁ , BR ₂ ,
BR ₃ are each breakers.

Next, the operation will be explained while explaining the details of the circuit.

To explain the steady operation assuming that power is already applied to the entire circuit, a certain voltage is output at the VDC terminal, and switch means _P2 is turned on, so that the transistor is connected through resistor _R3 .
_Q1 is on. A certain voltage is generated in resistor _R5 , and at the same time, capacitors _C4 and _C5 are charged through resistor _R7 . When the charging voltage of capacitor C ₅ reaches the sum of the terminal voltage of resistor R ₅ and the on-voltage of diode D ₂ , charging of capacitor C ₅ stops, and the current path changes to diode D ₂ and resistor R ₅ , and capacitor C Only ₄ will be charged. Then the capacitor
When the total voltage of C ₄ , diode D ₂ and resistor R ₅ reaches a predetermined value, the pulse generation circuit PG is activated and a pulse is output to the pulse transformer PT, and the semiconductor switch means T is ignited in a certain phase, and the lamp L is turned on. lights up. The lamp L is thus turned on at a certain phase during each half cycle of the AC power supply 2, and dimming is possible; to change the phase it is only necessary to control the voltage of VDC, and when the voltage is high As the temperature increases, the ignition phase advances and the lamp L becomes brighter. The pulse generation circuit PG may be a known circuit using PUT, UJT, SBS, or the like. Transistor _Q2 is for synchronizing pulse generation with the phase of AC power supply 2,
SYC is the change of each half cycle of AC power supply 2,
In other words, a predetermined pulse is output at the zero cross point, and the transistor Q ₂ is output via the resistor R ₉ .
is turned on, and the residual charges in capacitors _C4 and _C5 are discharged at the zero cross point by resistor _R8 and transistor _Q2 , thereby initializing the voltages of capacitors _C4 and _C5 . The reason why capacitors C ₄ and C ₅ are simultaneously charged at the beginning of charging is that if they are connected in series, the combined capacitance will be reduced and charging will be faster. This is because consideration has been made to ensure conduction of the semiconductor switch means T in almost all phases. Diode _D3 prevents reverse charging of capacitor _C5 .

Next, when the AC power supply 2 is first turned on to the lamp circuit 5 and the breaker BR ₃ is turned on later and the dimming control circuit 4 starts operating, the operation is as follows:
The voltage at the terminals of resistor R 5 still turns on transistor Q ₁ via the switch means P ₂ , but the voltage at the terminals of resistor R ₅ suddenly increases due to the large capacitor C ₃ in parallel with resistor R ₅ . As a result, the pulse generation phase of the pulse generation circuit PG is delayed, and as capacitor _C3 is gradually charged, the pulse generation phase becomes faster every half cycle, resulting in a so-called soft start.
This protects the lamp L and the semiconductor switch means T, and also prevents the breakers BR ₁ and BR ₂ from being disconnected. Resistor R ₆ is inserted to achieve an appropriate soft start effect, and a small amount of the charge in capacitor C ₃ is discharged by transistor Q ₂ at the zero cross point of AC power supply 2 through resistors R ₄ , R ₆ , and R ₈ . .
Note that a very short time is sufficient for the soft start.

Next, the operation will be explained based on the power-on order in which the effects of the present invention appear. In this case, the breaker BR ₃ is turned on first and the dimming control circuit 4 is already in steady operation. In this case, considering the conventional example in which there is no switch means P ₂ and VDC is directly connected to resistor R ₃ , capacitor C ₃ has already been charged and the soft start function has already ended. It is. Therefore, the inrush current of the lamp L may shorten the life of the lamp L and the semiconductor switch means T, and may cause the breaker BR ₁
or BR ₂ will be disconnected. However, according to the present invention, even if the AC power source 2 is later turned on to the lamp circuit 5 by turning on the breakers BR ₁ and BR ₂ , the detection circuit 7 detects that the AC power source 2 is turned on later to the lamp circuit 5. There is. This detection circuit 7 detects the line voltage of the branch line 6 through a diode bridge DB.
The light emitting element _P1 emits light via the resistor _R1 , and the switch means _P2 is turned on only by the light emission. Therefore, since capacitor _C3 starts charging only at that point, the soft start effect is maintained. Therefore, even in such a case, the life of the lamp L and the semiconductor switch means T will not be shortened, and the breakers BR ₁ and BR ₂ will not be disconnected. The resistor _R2 divides an appropriate voltage to the light emitting element _P1 , the capacitor _C1 provides a slight time constant, and the diode _D1 prevents the application of a reverse voltage to the light emitting element _P1 . The detection circuit 7 is not limited to such a circuit. Chiyoke coil in lamp circuit 5
CH contributes to protecting the semiconductor switch means T and optimizing the lamp current waveform. Note that the dimming control circuit 4 may be of any type as long as it generates a pulse during each half cycle of the AC power source 2, and there is no reason why the soft start circuit is limited to the example circuit.
Furthermore, although the switch means _P2 is provided at the input of the dimming control circuit 4, the point is that any switch means may be used to start the operation of the soft start circuit. Furthermore, although the dimming control circuit 4 has been shown to variably control the pulse phase using a variable DC voltage from the outside, it may also be possible to use a variable charging time constant method in which the resistor _R7 is made variable, or by digital signal processing. Of course, a variable pulse phase method may also be used.

Effects of the Invention As is clear from the description of the embodiments above, according to the present invention, even when AC power is turned on to the lamp circuit after the dimming control circuit, a detection circuit is provided to detect this power-on. Since a switch means is provided for starting the soft start circuit when the detection circuit is activated, the function of the soft start circuit is maintained and the life of the lamp and the semiconductor switch means for lighting the lamp is not shortened due to in-rush current. It is possible to prevent the breaker from disconnecting without any trouble, and it is possible to use the present invention advantageously in a wiring state where the AC power supply line is separated into a lamp circuit and a dimming control circuit.

[Brief explanation of the drawing]

The drawing is a circuit diagram of an embodiment of the dimming control device of the present invention. 2...AC power supply, 4...Dimmer control circuit, 5...
Lamp circuit, 6... Branch line, 7... Detection circuit, T... Semiconductor switch means, L... Lamp,
_P2 ...Switch means, _BR1 , _BR2 , _BR3 ...Breaker, capacitor _C3 is involved in the soft start circuit.

Claims (1)

[Claims] 1 A dimming control circuit that is supplied with AC power through a breaker and generates a pulse in each half cycle of the AC power; a lamp circuit having a lamp lit by a semiconductor switch means ignited by a pulse, the dimming control circuit having a soft start circuit, and a detection circuit detecting that AC power is applied to the lamp circuit. and a switch means for starting the soft start circuit in response to the operation of the detection circuit.