JPH04351895A - Discharge lamp lighting device - Google Patents

Abstract

PURPOSE:To prevent an instantaneous flashing of a discharge lamp when a power supply is turned on for a discharge lamp lighting device having a precedingly preheating timer circuit for start lighting the discharge lamp after preheating a filament for a predetermined period in turning on the power supply. CONSTITUTION:An action starting timing for a precedingly preheating timer circuit 4 is set to be earlier than an action starting timing for a drive circuit 3. When an om-signal of a predetermined time width is given to a switching transistor Q3 by the drive circuit 3, the precedingly preheating timer circuit 4 is already operating, and a normal lighting action is started only after a precedingly preheating action for a predetermined time. Instantaneous light emission of a discharge lamp La just after turning on a power supply can thus be eliminated, thereby deterioration of a life of filaments f1, f2 of the discharge lamp La can be prevented.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inverter-type discharge lamp lighting device for lighting a discharge lamp at high frequency.

0002

2. Description of the Related Art FIG. 3 is a circuit diagram of a conventional inverter type discharge lamp lighting device. The circuit configuration and operation thereof will be explained below. When the power switch SW is turned on, the AC power source AC is full-wave rectified by the diode bridge DB and smoothed by the electrolytic capacitor C1. The DC power obtained from the electrolytic capacitor C1 becomes the power source for the inverter lighting circuit.

The starting circuit of the inverter lighting circuit consists of a resistor R.
1, capacitor C2, bidirectional trigger element Q1
When the power is turned on, the electrolytic capacitor C1
capacitor C2 via resistor R1 due to the charging voltage of
and the charging voltage is the bidirectional trigger element Q1.
When the breakover voltage of C2 is reached, capacitor C2
Since the charged charge is discharged between the base and emitter of the transistor Q3, a current flows to the base of the transistor Q3 and activates the transistor Q3.

When the transistor Q3 is turned on, a DC power supply consisting of an electrolytic capacitor C1 is connected to a parallel circuit of a coupling capacitor C3, a resonance capacitor C4, a preheating capacitor C5 for the discharge lamp La and its filaments f1 and f2, and a resonance transformer. A resonant current flows through the primary winding n1 of T1 and the transistor Q3. The on time of this transistor Q3 is determined by the drive circuit 3. In this drive circuit 3, resistors R2, R
3 detects the fall of the voltage at the connection point of transistors Q2 and Q3, turns on transistor Q4 for a certain period of time determined by the time constant of resistor R7 and capacitor C9 from the time of the fall, and turns on transistor Q5.
Monostable multivibrator IC to turn off
1 works. At this time, a base current flows to the base of the transistor Q3 via the resistor R5, and the transistor Q3 is turned on. After the predetermined time has elapsed, the transistor Q4 is turned off and the transistor Q5 is turned on. This turns off transistor Q3.

When transistor Q3 suddenly turns off,
The resonant current flows through the diode D1 due to the excitation of the primary winding n1 of the transformer T1, but eventually an induced voltage that drives the transistor Q2 is generated in the secondary winding n2 of the transformer T1, turning on the transistor Q2. When transistor Q2 is turned on, the charge stored in coupling capacitor C3 is transferred to transistor Q2.
, the primary winding n1 of the transformer T1, a parallel circuit of the discharge lamp La and the capacitors C4 and C5, and a resonant current flows in the opposite direction. At this time, an induced voltage is generated in the secondary winding n2 of the transformer T1 in the direction of turning on the transistor Q2, but as the resonant current decreases, the induced voltage in the secondary winding n2 of the transformer T1 suddenly reverses. Then, a self-excitation operation is performed to turn off transistor Q2. Since the transistor Q2 turns off suddenly, the resonant current flows through the capacitor C1 and the diode D2 to the primary winding n1 of the transformer T1. then,
Since the voltage at the connection point between transistors Q2 and Q3 decreases, the fall of this voltage is detected by resistors R2 and R3, and as explained earlier, transistor Q3
Perform the action to turn on. Thereafter, the above operation is repeated, and the inverter lighting circuit 1 performs a high frequency oscillation operation. Note that resistors R4 and R5 are transistor Q2
, Q3 is a base resistor that limits the base current of Q3.

Next, the advance preheating timer circuit 4 will be explained. This circuit consists of comparator CP and diode D
3. It is composed of resistors R8, R9, R10, R11 and capacitor C7. When capacitor C7 is charged with the charging current determined by resistor R9 and the charging voltage becomes higher than the reference voltage determined by resistors R10 and R11, the comparator CP The output voltage V1 changes from High level to Low level. In other words, when the power is turned on and charging of capacitor C7 starts, output voltage V1 of comparator CP is at a high level, and at this time, the connection point between resistor R7 of drive circuit 3 and capacitor C9, which determines the on period of transistor Q3. To,
By flowing a current based on the output voltage V1 of the comparator CP through the diode D3 and the resistor R8, the charging time constant of the capacitor C9 is reduced. Therefore, the output pulse width of monostable multivibrator IC1 is shortened, and the on-time width of transistor Q3 is narrowed.
The output of the inverter lighting circuit 1 is reduced. As a result, a preliminary preheating current is passed through the filaments f1 and f2 of the discharge lamp La with an output that does not reach the starting voltage of the discharge lamp La, and the filaments f1 and f2 are sufficiently preheated.
do. Thereafter, as the output of the comparator CP becomes Low level, the output pulse width of the drive circuit 3 is changed by the resistor R7.
The on-time width of the transistor Q3 is widened. As a result, the output of the inverter lighting circuit 1 is changed to the discharge lamp La.
The voltage is sufficient to start and light the discharge lamp La, thereby causing the discharge lamp La to start and light.

In this way, in the inverter-type discharge lamp lighting device, instead of immediately applying a high voltage to the discharge lamp La to start lighting when the power is turned on, the advance preheating timer circuit 4 is activated when the power is turned on. By preheating the filaments f1 and f2 for a certain period of time, the discharge lamp La
The filament life of the filament can be extended.

[0008]

[Problems to be Solved by the Invention] In the conventional example described above, the drive circuit 3 and advance preheating timer circuit 4 that constitute the control circuit 2 of the inverter lighting circuit 1 rectify the AC power supply AC using the diode bridge DB and the capacitor C1. It is operated by a control power source E1 whose capacitor C8 is charged from a smoothed voltage via a resistor R6. By the way, immediately after the power is turned on when the power switch SW is turned on, the control power source E1 is gradually charged with a time constant determined by the resistor R6 and the capacitor C8. Now, drive circuit 3
The operation start voltage of the monostable multivibrator IC1 used in the circuit is Vth1, and the operation start voltage of the comparator CP used in the advance preheating timer circuit 4 is Vth.
2, there are naturally variations in these voltages Vth1 and Vth2. Therefore, for example, as shown in FIG. 4, when Vth2 > Vth1, as shown in FIG.
As shown in (A), the control power source E1 gradually increases,
At time t1, the monostable multivibrator IC1 starts operating, and as shown in FIG. 4(B), an on signal with a wide time width Tb appears at a predetermined period Ta, and the transistor Q3
Try to turn it on. Thereafter, at time t2, the advance preheating timer circuit 4 starts operating, so the output voltage V1 of the comparator CP becomes as shown in FIG. 4(C).
Changes from Low level to High level. After the advance preheating timer circuit 4 starts operating, as shown in FIG. 4(B), an on signal with a narrow time width Tc appears, which shortens the on time width of the transistor Q3, and performs the above-mentioned advance preheating operation. It is something.

Therefore, during the period (t2-t1) after the monostable multivibrator IC1 of the drive circuit 3 starts operating until the comparator CP of the advance preheating timer circuit 4 starts operating, the advance preheating operation is not performed. In order to perform normal lighting operation, the output of the inverter lighting circuit 1 becomes normal for a very short period of time, and the starting lighting voltage is momentarily applied to the discharge lamp La, so that the discharge lamp La is momentarily turned off. After it lights up, it will go into advance preheating operation. In this way, the monostable multivibrator IC1 of the drive circuit 3 and the comparator C of the advance preheating timer circuit 4
Due to variations in the operation start voltage of P, immediately after turning on the power,
The discharge lamp La goes into a momentary flash mode where it lights up for a moment, and the filaments f1 and f2 of the discharge lamp La
There was a problem of shortening the lifespan of. Additionally, the momentary flash mode looks like a glow starter when a copper-iron type ballast is used, and there is also the problem that the effect of using an inverter lighting device is somewhat reduced.

The present invention has been made in view of these points, and its object is to provide a preheating timer circuit that starts and lights a discharge lamp after preheating a filament for a certain period of time when the power is turned on. An object of the present invention is to prevent the discharge lamp from momentarily flashing when the power is turned on in a discharge lamp lighting device having the above.

[0011]

[Means for Solving the Problems] In order to solve the above-mentioned problems, the present invention, as shown in FIG.
. In a discharge lamp lighting device having an advance preheat timer circuit 4 that suppresses the output of the inverter lighting circuit 1 by changing the on-time width for a certain period of time from the time of turning on, the operation start timing of the advance preheat timer circuit 4 is driven. This is characterized in that the timing is set earlier than the timing at which the circuit 3 starts operating.

0012

[Operation] In the present invention, as described above, the operation start time of the advance preheating timer circuit 4 is set earlier than the operation start time of the drive circuit 3, so that the drive circuit 3 sends an ON signal of a predetermined time width to the switching transistor Q3. When the preheating timer circuit 4 is given, the advance preheating timer circuit 4 has already started its operation, and the advance preheating operation always proceeds to the normal lighting operation after a predetermined period of time. Therefore, the phenomenon in which the discharge lamp La momentarily emits light immediately after power is turned on does not occur, unlike in the conventional case, and it is possible to prevent the life of the filaments f1 and f2 of the discharge lamp La from being impaired.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a circuit diagram of an embodiment of the present invention. The circuit configuration will be explained below. The alternating current power source AC is connected to the alternating current input terminal of the diode bridge DB via a power switch SW. An electrolytic capacitor C1 is connected to the DC output terminal of the diode bridge DB. The DC voltage obtained across the electrolytic capacitor C1 is applied to a series circuit of transistors Q2 and Q3. Diodes D1 and D2 are connected in antiparallel between the collector and emitter of each transistor Q2 and Q3, respectively. A coupling capacitor C3, a resonance capacitor C4, and a transformer T1 for resonance and current feedback are connected to both ends of the transistor Q2.
The series circuit of the next winding is connected, and the capacitor C4
The power supply side terminals of filaments f1 and f2 of a hot cathode discharge lamp La such as a fluorescent lamp are connected to both ends of the filament. A capacitor C5 for supplying a preheating current is connected in parallel between the non-power supply side terminals of the filaments f1 and f2. The secondary winding of the transformer T1 is connected between the base and emitter of the transistor Q2 via a base resistor R4. Furthermore, an output signal from the drive circuit 3 is input between the base and emitter of the transistor Q3 via a base resistor R5. The voltage between the collector and emitter of the transistor Q3 is divided by a series circuit of resistors R2 and R3 and input to the drive circuit 3. In addition, in order to start the inverter lighting circuit 1, the resistor R1 is
charges capacitor C2 through capacitor C2
When the charging voltage of the bidirectional trigger element Q1 exceeds the breakover voltage of the bidirectional trigger element Q1, the bidirectional trigger element Q1
1 becomes conductive, and the charge of the capacitor C2 is supplied to the base of the transistor Q3. After the inverter lighting circuit 1 starts up, the transistor Q3
Each time the capacitor C2 is turned on, the charge stored in the capacitor C2 is discarded via the diode D4, so that the startup circuit stops operating.

Next, the configuration of the control circuit 2 will be explained. This control circuit 2 includes an advance preheating timer circuit 4 and a drive circuit 3, and its control power source E1 is obtained by charging a capacitor C8 via a resistor R6 from a DC power source E2 obtained in an electrolytic capacitor C1. . In the advance preheating timer circuit 4, this control power source E1 is divided by resistors R10 and R11 and applied as a reference voltage to the non-inverting input terminal (+) of the comparator CP. In addition, the capacitor C is connected from the control power source E1 through the resistor R9.
7 is charged and the charged voltage is applied to the inverting input terminal (-) of the comparator CP and compared with the reference voltage. The output of comparator CP is connected to diode D3 and resistor R
8 through the resistor R7 of the drive circuit 3 and the capacitor C9.
connected to the connection point. This resistor R7 and capacitor C9 constitute a time constant circuit of the monostable multivibrator IC1. Monostable multivibrator IC
1 detects the fall of the voltage between the collector and emitter of the transistor Q3 with the resistors R2 and R3, and for a predetermined period of time from the falling point, turns on the transistor Q4 and turns off the transistor Q5. and provides an on-drive signal to transistor Q3. After the predetermined time has elapsed, the transistor Q4 is turned off, and the transistor Q5 is turned off.
This turns on the transistor Q3 and turns off the transistor Q3.

The difference between the circuit of this embodiment and the conventional circuit shown in FIG. The circuit is supplied through the impedance conversion element IC2 having a latching function, and the other circuit configuration is the same as that of the conventional example shown in FIG. Omitted.

In this circuit, the comparator CP of the advance preheating timer circuit 4 always starts operating before the drive circuit 3 starts operating.
The monostable multivibrator IC1 starts operating. Therefore, unlike the conventional example, when the power is turned on, the drive circuit 3 operates with a normal output first, and the problem of momentary flashing does not occur. This circuit operation is shown in FIG. FIG. 2(A) shows the rise of the voltage of the capacitor C8 when the power is turned on, and at time t2, the operation start voltage Vth2 of the advance preheating timer circuit 4 is reached, and as shown in FIG.
As shown in (B), the output voltage of the comparator CP of the advance preheating timer circuit 4 becomes High level. At this time, in response to the rise of the output voltage of the comparator CP, the output of the impedance conversion element IC2 also changes to the control power supply E.
1 and the drive circuit 3 also starts operating at the same time, so the output terminal Q of the monostable multivibrator IC1
The signal waveform of , as shown in FIG. 2(C), has a narrow on-width T
c, and the inverter lighting circuit 1 starts operating from the advance preheating mode.

Although an embodiment has been described in which a monostable multivibrator is used in the drive circuit and a comparator is used in the advance preheating timer circuit, the present invention is not particularly limited to this. Further, in this embodiment, the inverter lighting circuit 1 as illustrated in FIG. 1 is used, but the invention is not limited to this, and at least one switching element is
Any inverter lighting device can be used as long as it has a control circuit that has a drive circuit that outputs an ON width determined by the time constant of A circuit method may also be adopted.

[0018]

According to the present invention, as described above, in the inverter-type discharge lamp lighting device that starts and lights the discharge lamp after preheating the filament for a certain period of time when the power is turned on, at least A preliminary preheating timer circuit that suppresses the output of the inverter lighting circuit by changing the on-time width for a certain period of time from the time of power-on, rather than the operation start time of the drive circuit that determines the on-time width of one switching element. Since the operation start time is set early, it is possible to prevent the discharge lamp from flashing momentarily immediately after the power is turned on, which has the effect of preventing shortening of the filament life of the discharge lamp, and also enables smooth start-up and lighting. It has the effect of becoming

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of an embodiment of the present invention.

FIG. 2 is an operational waveform diagram of an embodiment of the present invention.

FIG. 3 is a circuit diagram of a conventional example.

FIG. 4 is an operational waveform diagram of a conventional example.

[Explanation of symbols]

1 Inverter lighting circuit 2 Control circuit 3 Drive circuit 4 Advance preheating timer circuit La discharge lamp Q2 Switching transistor Q3 Switching transistor E1 Control power supply E2 DC power supply

Claims (1)

[Claims] 1. A DC power source, an inverter lighting circuit that starts and lights a discharge lamp by converting the DC power source into high-frequency power by turning on and off a switching element, and an on-time width of at least one switching element of the inverter lighting circuit. In a discharge lamp lighting device, the discharge lamp lighting device includes a drive circuit that determines the output of the inverter lighting circuit, and an advance preheat timer circuit that suppresses the output of the inverter lighting circuit by changing the on-time width for a certain period of time after power is turned on. A discharge lamp lighting device characterized in that an operation start time is set earlier than an operation start time of a drive circuit.