JPH0546240Y2 - - Google Patents

Description

[Detailed Description of the Invention] (a) Field of Industrial Application This invention relates to a lamp lighting control circuit that softly turns on the lamp by gradually increasing the power supplied to the lamp as a load when the power is switched on.

(b) Prior Art In general, a soft-start control circuit that takes into account the human eye's adaptation to light and dark, gradually increases the amount of illumination light by gradually increasing the power supplied to the lamp when the power source of the lighting equipment is turned on. It is used. Similar soft start control circuits are also used to limit the inrush current that flows when power is turned on for relatively high power lamps.

A conventional general soft-start control circuit consists of a charging circuit consisting of a capacitor and a resistor, and a phase control circuit that controls the conduction angle of a triass or thyristor based on the charging voltage of the capacitor. That is, when the charging voltage of the capacitor is low immediately after the power switch is turned on, the phase control circuit controls the conduction angle of the switch element to approximately 0°, and increases the conduction angle of the switch element as the charging voltage of the capacitor increases.

(c) Problems to be solved by the invention However, in conventional soft-start control circuits, the time constant of the charging circuit consisting of a capacitor and a resistor is relatively large. If the power switch is turned off and then turned on again within a short period of time, the capacitor's charge will remain, so it will not start lighting from approximately 0%, but will respond to the capacitor's charging voltage. Lighting will start from this state.

Of course, in the conventional soft start control circuit,
A discharge resistor is provided to discharge the charge in the capacitor when the power switch is turned off, but due to the need to minimize the minimum conduction angle of the switch element, the value of the discharge resistor cannot be made very small, and the discharge time constant It was big. For this reason, for example, even if the power switch was turned off and then turned on again after one minute had elapsed, there were cases in which lighting could not be started from 0%.

The purpose of this invention is to provide a lamp lighting control circuit that can always soft-start the lamp even if the power switch is turned on again in a short period of time.

(d) Means for Solving the Problems The lamp lighting control circuit of this invention includes a first charging circuit including a capacitor and a resistor, and a phase control circuit that controls the conduction angle of the switch element by the charging voltage of this capacitor. a second charging circuit that includes a capacitor and a resistor and is charged when the power is switched on; and a second charging circuit that is charged when the power is switched off;
The present invention is characterized by providing a timer circuit that is turned on by the charging voltage of the capacitor of the charging circuit, and a discharging circuit that forcibly discharges the charge of the capacitor of the first charging circuit when the timer circuit is turned on.

(e) Function Figure 1 shows an example of the configuration of this device. In the figure, 7 is a soft start control circuit, and 6 is a lamp, and this lamp 6 is connected to a commercial power source AC via the soft start control circuit 7 and a power switch SW. In the soft start control circuit 7, Q1 is a switch element, and DB is a diode bridge. The rectified output of this diode bridge DB includes a first circuit including a resistor Ra and a capacitor C4.
A charging circuit 1 is connected thereto. In addition, the switch element Q is connected at a conduction angle according to the output of the first charging circuit 1.
A phase control circuit 3 is connected thereto.

In the circuit section shown above, the power switch
When SW is turned on, the phase control circuit 3 turns on the switch element Q1 when the rectified output of the diode bridge DB reaches a predetermined phase, but this conduction angle changes as the charging voltage of the capacitor C4 increases. It gradually increases from approximately 0° to approximately 180°. This performs soft start control.

Now, as shown in Fig. 1, the rectified output of the diode bridge DB is further connected to a second charging circuit 2 consisting of a resistor Rb and a capacitor C6, and a second charging circuit 2 consisting of a resistor Rb and a capacitor C6.
Timer circuit 4 that turns on by the charging voltage of 6
is connected. Further, a discharge circuit 5 is connected in parallel to the capacitor C4, and the charge in the capacitor C4 is forcibly discharged when the timer circuit 4 is turned on. Since such a circuit is added to the soft start control circuit 7, the power switch
Once the SW is turned off, the timer 4 is turned on after a certain period of time (for example, after several hundred milliseconds) by the charge stored in the capacitor C6, activates the discharge circuit 5, and forcibly discharges the charge in the capacitor C4. let Therefore, even if the power switch SW is once turned off and then turned on after a short period of time, the charging voltage of the capacitor C4 rises from approximately 0, so that the lamp 6 is normally soft-start controlled.

(f) Embodiment FIG. 2 shows a lamp lighting control circuit which is an embodiment of this invention. In the figure, 6 is a lamp, Q1 is a switch element, and lamp 6 is a switch element Q.
The power is controlled by the switching control of No. 1.
Incidentally, the choke coil L and the capacitor C1 constitute a filter circuit for reducing noise caused by switching of Q1. In addition, DB in the figure is a diode bridge, and resistors R1,
The commercial power input via R2, R3 and the chiyoke coil L is rectified. When current flows through the diode bridge DB, a voltage drop occurs across the resistor R3, and when the voltage drop exceeds a certain value, a trigger current flows through the gate of Q1, turning Q1 on. The phase of Q1 is controlled by the circuit current of a circuit connected to the output of DB, which will be described later.

The rectified output of the diode bridge DB has a resistor R.
4 and R5, and a resistor R
7, R8 and a capacitor C3 is provided, and the base and emitter of a transistor Q4 are connected to points a and b shown in the figure, respectively. Also, diode bridge
A transistor Q5 is connected between the rectified output of DB, and a resistor R6 is connected between the base and emitter of Q5.
are connected, and the base of Q5 and the collector of Q4 are connected. In addition, the diode bridge
A resistor R7 and a diode D are connected between the rectified output of DB.
2, the first consisting of capacitor C4 and resistor R9
A charging circuit 1 is connected thereto.

The circuit operation of the portion shown above is as follows.

First, when the power switch SW is turned on, a full-wave rectified waveform voltage divided by R1, R2, R3, R4, R5, etc. is generated at point a. On the other hand, a divided voltage substantially determined by R1, R2, R3, R7, and R9 is applied to the capacitor C4, and its charging voltage gradually increases. Further, the potential at point b generates a sawtooth waveform voltage with a time constant approximately determined by R7, R8, C3, and C4. (R1, R2,
The value of R3 is smaller than R7 and R8. ) Therefore, when the potential at point b exceeds the potential at point a by about 0.7 volts, Q4 turns on, which turns on Q5. At this time, the voltage drop across R3 increases and Q1 turns on. As C4 charges, the sawtooth waveform voltage at point b equivalently decreases the time constant of CR circuit 9 and reaches the condition b>a+0.7 at an early phase angle, so the conduction angle of Q1 increases. become.
Soft start control is performed in this way.

Now, as shown in FIG. 2, the rectified output via the diode D1 is further connected to resistors R13 and R16.
and a second charging circuit 2 consisting of a capacitor C6
is provided. Also, R13, R14, C5
A charging circuit is also configured by the above, and the output point d of C6 and the output point c of C5 are connected to the anode and gate of an N-gate thyristor (PUT) Q2, respectively. Note that discharge resistors R15 and R17 are connected to capacitors C5 and C6, respectively. Resistors R12 and R11 are connected to the cathode of the N-gate thyristor Q2, and R12 and R1
The base of the transistor Q3 is connected to the connection point of the transistor Q3. Furthermore, there is a resistor R across the capacitor C4.
Transistor Q3 is connected via 10.

The operation of the additional circuit shown above is as follows.

First, when the power switch SW is turned on, C5
through R13 and R14, and through R1 to C6.
3, and charging is performed via R16, respectively. At this time, the resistance voltage division ratio is determined so that the potential at point c is higher than the potential at point d. After that, once the power switch SW is turned off, the charging charge of C5 is changed by R15, and the charging charge of C6 is changed by R15.
17, respectively. At this time, C
The CR constant is determined such that the discharge time constant made up of C6 and R15 is smaller than the discharge time constant made up of C6 and R17. Therefore, after that, the potential at point c becomes lower than the potential at point d, and Q2 turns on at that time. At this time, the charging charge of C6 is Q2, R1
2, discharged to the base of R11 and Q3 and Q3
turns on. As a result, the charging charge of C4 becomes R10
It is quickly discharged through Q3. This C
4, R10, and Q3 is set as small as possible without exceeding the maximum rating of Q3. Therefore, when the power switch SW is turned on after that, charging of C4 starts from approximately 0V,
Normal soft start control is performed. On the other hand, C
Since the charge at point 6 is almost completely discharged, the condition that the potential at point c>the potential at point d is satisfied immediately after the power switch SW is turned on, so there is no malfunction such as transient turning on of Q3.

(g) Effects of the invention As described above, according to this invention, even if the power switch is turned off and then turned on again within a short period of time, normal lamp soft start control is performed, making it difficult for the human eye to see. It is possible to constantly and reliably perform lamp lighting control suitable for adaptation to light and darkness, or to suppress inrush current when the power is switched on.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an example of the configuration of this invention. FIG. 2 is a diagram showing a lamp lighting control circuit which is an embodiment of this invention. DESCRIPTION OF SYMBOLS 1... First charging circuit, 2... Second charging circuit, 3... Phase control circuit, 4... Timer circuit, 5
...Discharge circuit, 6...Lamp, 7...Soft start control circuit.

Claims (1)

[Claims for Utility Model Registration] A first charging circuit including a capacitor and a resistor, a phase control circuit that controls the conduction angle of a switch element according to the charging voltage of the capacitor, and a phase control circuit including a capacitor and a resistor, a second charging circuit that is charged; and a second charging circuit that is charged after a certain period of time from the power switch off.
A lamp lighting control circuit comprising: a timer circuit that is turned on by a charging voltage of a capacitor of a charging circuit; and a discharge circuit that forcibly discharges the charge of a capacitor of a first charging circuit when the timer circuit is turned on.