JP2934166B2 - Lighting device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lighting device for rectifying an AC power supply voltage, converting the voltage to a high frequency, and lighting a lamp such as an incandescent lamp with the high frequency power.

[0002]

2. Description of the Related Art FIG. 3 is a circuit diagram of a conventional lighting device.

This lighting device comprises a lighting circuit 1 and a dimming circuit 2
It is composed of

The lighting circuit 1 includes a rectifier Re and a half-bridge type transistor inverter circuit. That is, a pair of transistors Q1 and Q2, which are switch elements, and each of the transistors Q1 and Q2 are connected between the output terminals of the rectifier Re.
A pair of resistors R1, R2 respectively connected to the
And a series circuit of a pair of capacitors C1 and C2 are connected in parallel. Reflux diodes D1 and D2 are connected in anti-parallel to the series circuit of the transistors Q1 and Q2 and the resistors R1 and R2, respectively. A step-down transformer T is connected between the connection point of the capacitors C1 and C2 and the connection point of the resistor R1 and the collector of the transistor Q2.
1 and a series circuit of the primary winding of the feedback transformer T2.

An incandescent lamp LP is connected to the secondary winding of the step-down transformer T1. Both ends of a pair of secondary windings of the feedback transformer T2 are connected to the base-emitter of each of the transistors Q1 and Q2 and the resistor R1. , R2. The two secondary windings of the feedback transformer T2 are connected to the transistors Q1 and Q2 so that the phases are opposite to each other. A noise filter including a capacitor C4 and a choke coil CH is provided at a stage preceding the rectifier Re.

The lighting circuit 1 is provided with a starting circuit S including a resistor R3, a capacitor C3, and a trigger element (SBS or the like) Q3. That is, the resistor R3 and the capacitor C
3 is connected between both ends of the series circuit of the capacitors C1 and C2, the voltage between both ends of the capacitors C1 and C2 becomes equal to or higher than a predetermined voltage, and the terminal of the capacitor C3 is connected to the trigger element Q3 via the resistor R3. When the battery is charged up to the breakover voltage, the trigger element Q3 is turned on to turn on the transistor Q2.

The diode D3 is connected to the transistor Q
2 is provided to prevent charging of the capacitor C3 during repeated ON and OFF, and when the oscillation operation is stopped, the capacitor C3 is recharged.

On the other hand, a dimming circuit 2 for controlling the phase of the commercial power supply AC is provided between the commercial power supply AC and the lighting circuit 1, and turns on the phase control element Q4 such as a triac and the phase control element Q4. And a trigger circuit for causing the resistors R4 to R6, the capacitor C5,
It is constituted by a trigger element Q5.

When the capacitor C5 is charged and the terminal voltage reaches the breakover voltage of the trigger element Q5, the trigger element Q5 is turned on and the phase control element Q4 is turned on. Note that the phase control element Q
The firing angle of 4 is adjusted by the resistor R5.

Next, the operation will be described.

When the phase control element Q4 of the dimming circuit 2 is turned on, the AC power supply voltage is full-wave rectified by the rectifier Re.
The capacitors C1, C2 and C3 are charged. With the capacitors C1 and C2 charged, the starter circuit S (by the charged voltage of the capacitor C3) causes the transistor Q
When 2 is started (turned on), the electric charge charged in the capacitor C2 is released through the path of the primary winding of the step-down transformer T1, the primary winding of the feedback transformer T2, and the transistor Q2.

At this time, a current flows in the secondary winding of the feedback transformer T2 so as to forward bias the transistor Q2 (therefore, the transistor Q1 is reverse-biased and turned off). Thereafter, the current flowing through the primary winding of the feedback transformer T2 is limited to a current corresponding to the equivalent resistance of the incandescent lamp LP, and no current flows through the secondary winding of the feedback transformer T2, and the transistor Q2 is turned off. I will head. Therefore, a current that reversely biases the transistor Q2 and forward biases the transistor Q1 flows through the secondary winding of the feedback transformer T2. As a result, the transistor Q1 is turned on and the electric charge stored in the capacitor C1 is turned on. From the transistor Q1 → the primary winding of the feedback transformer T2 → the step-down transformer T1.

This operation is repeated to perform an oscillation operation. That is, the pulsating current output from the rectifier Re is converted into a high frequency, and the high frequency power turns on the incandescent lamp LP.

[0014]

By the way, after the above-mentioned phase control element Q4 is turned on,
The starting circuit S turns on the transistor Q2 to start the high-frequency conversion operation, and then turns off when the lighting device input current (hereinafter referred to as “input current”), which is the current flowing through the device Q4, becomes zero. .

In addition, the operation of the element Q4 becomes unstable in the vicinity of the phase 0 ° (180 °) where the input current becomes small, and the input current is reduced by the influence of the leading currents of the capacitors C4, C1 and C2. As shown in FIG. 4, there is a case where the voltage quickly becomes zero (in this case, the lighting device input voltage (hereinafter, referred to as “input voltage”) also becomes zero). In such a case, the phase control element Q4 is turned off early, and this early turn-off causes flickering of the incandescent lamp LP.

Therefore, an object of the present invention is to light a lamp using an AC power supply as an input, and to delay a leading current caused by the capacitive load in a lighting device that acts as a capacitive load to the AC power supply. By doing so, it is possible to avoid a rapid turn-off of the phase control element that controls the phase of the AC power supply,
It is an object of the present invention to provide a lighting device capable of preventing a lamp from flickering.

[0017]

According to the present invention, there is provided a lighting device for lighting a lamp using an AC power supply as an input and serving as a capacitive load for the AC power supply. A charging / discharging circuit for discharging, wherein the charging / discharging circuit is configured to delay a leading current caused by a capacitive load by making a discharging time constant larger than a charging time constant. And

In a preferred embodiment, the charging / discharging circuit includes a small time constant circuit for charging the capacitor in a relatively short time, and a large time constant circuit for discharging the capacitor from the capacitor in a relatively long time. And a discharge circuit.
The small time constant circuit includes: the capacitor; a first resistor having a relatively small resistance connected in series to the capacitor;
A diode connected in series with the first resistor to prevent a discharge current from the capacitor from flowing into the first resistor, wherein the large time constant discharge circuit includes the capacitor and the capacitor; And a second resistor having a relatively large resistance value connected in series.

[0019]

According to the present invention, there is provided a charge / discharge circuit for charging / discharging each half-wave of an AC power supply.
By configuring the discharge time constant larger than the charge time constant to delay the phase advance current generated due to the capacitive load, by delaying the phase advance current generated due to the capacitive load, In addition, it is possible to avoid a rapid turn-off of the phase control element that controls the phase of the AC power supply.

[0020]

Embodiments of the present invention will be described below in detail with reference to the drawings. Note that the same components as those in the conventional example shown in FIG. 3 are denoted by the same reference numerals, and description thereof will be omitted.

FIG. 1 is a circuit diagram of a lighting device according to one embodiment of the present invention.

As shown in FIG. 1, the lighting device of the present embodiment comprises a rectifier Re and capacitors C1 and C2 connected to the output stage of the rectifier Re in parallel with a phase converter having the following configuration. The feature is that the correction circuit 3 is connected.

The phase correction circuit 3 reduces the power supply voltage (that is, the voltage applied from the commercial power supply to the dimming circuit 2) by delaying the phase advance current caused by the capacitor C4 and the capacitors C1 and C2. This is for correcting that the phase of the input current is advanced and becomes zero quickly. The phase correction circuit 3 includes a capacitor C6 and a resistor R having a relatively large resistance connected in series to the capacitor C6.
8 and a series circuit including a resistor R7 having a relatively small resistance value and a diode D4.

The diode D4 charges the capacitor C6 with a relatively small time constant.
The charging current to the capacitor C6 flows to the resistor R7 and the capacitor C6 through the diode D4, and the discharging current from the capacitor C6 corresponds to the resistor 7 and the diode. It flows only through the resistor 8 without passing through D4.

In other words, in the phase correction circuit 3, the capacitor C6, the resistor R7 and the diode D4 for preventing the discharge current from the capacitor C6 from flowing through the resistor R7 have a relatively small time constant. A charging circuit for charging is formed, and a discharging circuit for discharging the capacitor C6 with a relatively large time constant by the capacitor C6 and the resistor R8.

In the lighting device of this embodiment, the same circuit operation as in the above-described conventional device is performed. However, in this embodiment, when the phase control element Q4 is turned on, the charging current to the capacitor C6 flows into the capacitor C6 through the diode D4 and the resistor R7, and the capacitor C6 is charged with a relatively small time constant. .
Therefore, the charging time of the capacitor C6 may be relatively short.

On the other hand, the value of the power supply voltage decreases with the passage of time, and the charge of the capacitor C6 is discharged from the capacitor C6 through only the resistor R8 due to the rectification of the diode D4. Discharge is performed. Therefore, the discharging time of the capacitor C6 is relatively long.

As described above, the discharge time of the capacitor C6 can be set to a relatively long time. Therefore, as shown in FIG. 2, the time when the input current becomes zero is delayed as compared with the case shown in FIG. Can be substantially synchronized with the power supply voltage becoming zero. That is, by setting the discharging time of the capacitor C6 to a relatively long time, the phase of the input current is delayed, and the input current can be prevented from becoming zero at an early timing. Therefore, it is also possible to avoid a rapid turn-off of the phase control element Q4 when the current is unstable, control the turn-off of the phase control element reliably, prevent flickering of the incandescent lamp, and perform stable dimming control. It became.

It should be noted that the above description relates only to one embodiment of the present invention, and does not mean that the present invention is limited to only the above description. In this embodiment, the lighting device for lighting an incandescent lamp has been described. However, the present invention is also applicable to a lighting device for lighting a lamp other than the incandescent lamp.

[0030]

As described above, according to the present invention,
In a lighting device that turns on a lamp using an AC power supply as an input and acts as a capacitive load for the AC power supply, a phase control phase of the AC power supply is delayed by delaying a leading phase current caused by the capacitive load. It is possible to provide a lighting device capable of avoiding a rapid turn-off of a control element and preventing flickering of a lamp.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a lighting device according to an embodiment of the present invention.

FIG. 2 is a waveform diagram of an input current and an input voltage in the device of FIG.

FIG. 3 is a circuit diagram of a conventional lighting device.

FIG. 4 is a waveform diagram of an input current and an input voltage in the lighting device of FIG. 3;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Lighting circuit 2 Light control circuit 3 Phase correction circuit Q4 Phase control element Re Rectifier LP Incandescent lamp

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Tadashi Akashi 3-18-16 Negishi, Taito-ku, Tokyo Tokyo Trans Co., Ltd. (58) Field surveyed (Int. Cl. ⁶ , DB name) H05B 37/00 -39/10

Claims (2)

(57) [Claims] 1. A lighting device for lighting a lamp with an AC power supply as an input and serving as a capacitive load for the AC power supply, comprising a charging / discharging circuit for charging / discharging each half-wave of the AC power supply. A lighting device, wherein the charge / discharge circuit is configured to delay a leading current generated due to a capacitive load by making a discharge time constant larger than a charge time constant. 2. The lighting device according to claim 1, wherein the charging / discharging circuit includes a small time constant circuit for charging the capacitor in a relatively short time, and a circuit for discharging the capacitor from the capacitor in a relatively long time. A large time constant discharge circuit, wherein the small time constant circuit comprises: the capacitor; a first resistor having a relatively small resistance connected in series to the capacitor;
A diode connected in series with the first resistor to prevent a discharge current from the capacitor from flowing into the first resistor; the large time constant discharge circuit includes: a capacitor; A lighting device comprising: a second resistor having a relatively large resistance value connected in series.