JP3314399B2 - Discharge lamp 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 discharge lamp lighting device for lighting a discharge lamp.

[0002]

2. Description of the Related Art Heretofore, a discharge lamp lighting device for supplying power to a discharge lamp from an AC power supply via a current limiting inductor has been often used. When the discharge lamp is a high-pressure discharge lamp or the like, a high-voltage pulse voltage is applied to the discharge lamp for starting or restarting.

FIG. 6 shows an example of a discharge lamp lighting device having such a pulse generating means, which comprises an AC power supply 1, an inductor 2 for current limiting, and both ends of the AC power supply 1. A discharge lamp 3 connected via the current limiting inductor 2, an intermediate tap 5 provided at a predetermined position of the current limiting inductor 2, and both ends of the AC power supply 1 connected via the intermediate tap 5. It comprises a series circuit of a capacitor C1 and a switching element Q1, and a control circuit T1 for applying a drive signal to the switching element Q1 every half cycle of the AC power supply 1.

Here, the intermediate tap 5 is provided at an arbitrary position where the current limiting inductor 2 is divided into an inductor L1 and an inductor L2. Then, the pulse voltage generated at both ends of the inductor L1 is transmitted to both ends of the inductor L2 in accordance with the turns ratio, and the voltage generated at both ends of the inductors L1 and L2 is added to the AC voltage V1 of the AC power supply 1 and discharged. The voltage is applied to both ends of the lamp 3.

An operation state will be described below with reference to an operation explanatory diagram shown in FIG. First, when the AC power supply 1 is input, as shown in FIG. 7 (a), a drive signal (shown in FIG. 7 (b)) from the control circuit T1 is delayed by a predetermined phase angle θ1 from the zero voltage of the AC voltage V1. Occurs. This drive signal is input between the control terminals of the switching element Q1, and switches the switching element Q1 from the off state to the on state.

When the switching element Q 1 is turned on, the AC power supply 1 supplies the intermediate tap 5 of the current limiting inductor 2.
→ Capacitor C1 → ON-state switching element Q1 →
An oscillating current due to the inductor L1, the capacitor C1, and the like flows through a closed circuit reaching the AC power supply 1. Immediately thereafter, when the drive signal is not applied between the control terminals of the switching element Q1 and the current flowing through the switching element Q1 becomes equal to or less than the holding current, the switching Q1 shifts from the on state to the off state.

The on / off operation of the switching element Q1 is repeatedly performed every half cycle of the AC power supply 1, and the voltage across the capacitor C1 and the voltage across the switching element Q1 are respectively shown in FIGS. ).

An AC voltage V is applied to both ends of the discharge lamp 3.
A high-voltage pulse voltage for starting or restarting is generated as shown in FIG. 5E in which a high-voltage pulse voltage generated across both ends of the inductor L1 is superimposed on 1 and the discharge lamp 1 starts or restarts.

In the above operating state, there is a problem that the voltage between both ends of the capacitor C1 is high and the element becomes large. This will be described below.

When switching element Q1 is turned on, the voltage across capacitor C1 rises to voltage Va. Immediately thereafter, the switching element Q1 is turned off, the electric charge of the capacitor C1 is discharged to the resistor R11 connected in parallel as shown in FIG. 7C, and the voltage across the capacitor C1 drops to the voltage Vb. In general, in order to light the discharge lamp 3 more quickly and reliably, it is necessary to widen the pulse width of the high-voltage pulse voltage and increase the peak value, so that the voltage across the capacitor C1 rises to a high voltage Va. This causes a problem with the withstand voltage of the switching element as shown in FIG.

In order to reduce the breakdown voltage of the switching element Q1, it is effective to lower the voltage across the capacitor C1.

First, as one means for lowering the withstand voltage of the capacitor C1, it is conceivable to set the resistance value of the parallel resistor R11 low to lower the value of the voltage Vb. In this case, a new problem arises in that the power loss in the discharge lamp lighting device increases, the size of the resistor R11 increases, and the loss of the discharge lamp lighting device increases.

Next, as another means, the voltage VQ1 across the switching element Q1 = (AC voltage V1-capacitor C
Paying attention to the relationship of one voltage VC1), the switching element Q1
It is conceivable that the ignition phase at which the lamp is turned on is set to around zero V of the AC voltage V1, but in this case, generally, the ignition phase for reliably starting the discharge lamp 3 is about 60 ° or more. 9
It is considered that the vicinity of 0 ° is preferable, and the generation of the high-voltage pulse by the ignition phase near 0 ° may cause a problem in starting or restarting performance.

[0014]

The problems to be solved by the present invention are that if the starting or restarting performance is improved, the breakdown voltage of the capacitor and the switching element is increased. There is an inconvenience that the loss of the device is increased and that the starting or restarting performance at the same high-voltage pulse energy is deteriorated if the ignition phase is set near zero V of the AC voltage to solve the problem. Was. An object of the present invention is to provide a discharge lamp lighting device capable of reducing the withstand voltage of a switching element for starting and the like.

[0015]

The present invention comprises an AC power supply,
A discharge lamp connected to both ends of the AC power supply via a current limiting inductor, an intermediate tap provided at a predetermined position of the current limiting inductor, and connected to both ends of the AC power supply via the intermediate tap. A discharge lamp lighting device comprising: a series circuit of a capacitor and a switching element; and a control circuit that applies a drive signal to the switching element every half cycle of the AC power supply, wherein the control circuit includes:
A period longer than the period of generation of the oscillating current generated when the switching element changes from the off state to the always on state.
During this period, the driving signal is input to the switching element, so that the driving signal generation period is longer than the oscillating current generation period.

[0016]

According to the present invention, an oscillating current is generated during a period when a switching element is constantly turned on from an off state.
Input the drive signal to the switching element for a longer period
Thus, the generation period of the drive signal is configured to be longer than the generation period of the oscillating current, so that the starting of the discharge lamp can be improved and the number of components of the switching element can be increased without increasing the number of components. This has the effect of reducing the withstand voltage.

[0017]

FIG. 1 shows a first embodiment of the present invention. A configuration different from FIG. 6 showing the conventional example is that a capacitor C1 connected in parallel and having no resistance is connected to an AC power supply 1
The input terminal is connected to both ends of the switch, and the output terminal is
And a control circuit T connected to one control terminal. Note that the same components are denoted by the same reference numerals, and redundant description will be omitted.

Here, the control circuit T is set so that the generation period of the drive signal is longer than the generation period of the oscillating current generated when the switching element Q1 changes from the off state to the always on state. A timer circuit TM, a photocoupler Q2 for transmitting an output of the timer circuit TM as an optical signal, and a resistor R2 connected between an on / off output terminal of the photocoupler Q2 and a control terminal of the switching element Q1. ing.

The operation state will be described below with reference to the operation explanatory diagram shown in FIG. First, when the AC power supply 1 is input, as shown in FIG. 2 (a), a drive signal (shown in FIG. 2 (b)) from the control circuit T is delayed by a predetermined phase from the zero voltage of the AC voltage V1.
Occurs. This drive signal is input between the control terminals of the switching element Q1, and switches the switching element Q1 from the off state to the on state. The period during which this drive signal is input between the control terminals of the switching element Q1 is the period during which the oscillating current is generated when the switching element Q1 is turned on from the off state (Vb shown in FIG.
The generation period of the drive signal is set to be longer than the generation period of the higher voltage Va).

When the switching element Q1 is turned on, the inductor L1 and the capacitor C1 are connected to a closed circuit from the AC power supply 1 to the intermediate tap 5 of the current limiting inductor 2 → the capacitor C1 → the on-state switching element Q1 → the AC power supply 1. Oscillation current flows due to the above. During the period in which the oscillating current is generated, the drive signal is input to the switching element Q1, and the switching element Q1 is kept on.

After the lapse of a predetermined time of the timer circuit TM, the generation of the oscillating current stops, the drive signal is no longer applied between the control terminals of the switching element Q1, and the switching Q1 shifts from the on state to the off state. .

As described above, the period during which the drive signal is input between the control terminals of the switching element Q1 is the generation period of the oscillating current generated when the switching element Q1 changes from the off state to the always on state (FIG. 2), the drive signal generation period is set to be longer than the voltage Va generation period Vb shown in FIG. 2B), so that the voltage across the capacitor C1 shown in FIG. Voltage Vb
Decay in a short time.

Therefore, as shown in the conventional example, the capacitor C
1, a resistor is connected in parallel, so that it is not necessary to attenuate the voltage across the capacitor C1 from the voltage Va to the voltage Vb while consuming the resistance, and it is possible to prevent an increase in components such as a resistor and an increase in loss.

FIG. 3 shows a second embodiment of the present invention. The configuration different from the first embodiment is that a series circuit of a resistor R1 and a capacitor C2 connected to both ends of an AC power supply 1, a gate element D1 such as a diac connected to both ends of the capacitor C2, and a resistor R2 And switching element Q1
And a series circuit between the control terminals.

The same components are denoted by the same reference numerals, and redundant description will be omitted. Here, the control circuit T controls the capacitor C2 and the resistor R2 so that the generation period of the drive signal is longer than the generation period of the oscillating current generated when the switching element Q1 changes from the off state to the always on state.
And constants are set.

With this configuration, the same effects as those of the first embodiment can be obtained.

FIG. 4 shows a third embodiment of the present invention. The configuration different from the first embodiment is that an AC power supply 1 is connected to a step-up or step-down transformer 4 at both ends. Note that the same components are denoted by the same reference numerals, and redundant description will be omitted. With this configuration, the same effect as that of the first embodiment can be obtained.

FIG. 5 shows a fourth embodiment of the present invention. The configuration different from the third embodiment is that the transformer connected to both ends of the AC power supply 1 is a magnetic leakage transformer 4. Note that the same components are denoted by the same reference numerals, and redundant description will be omitted. With this configuration, the same effect as that of the first embodiment can be obtained.

The present invention provides an AC power supply, a discharge lamp connected to both ends of the AC power supply via current limiting inductors, an intermediate tap provided at a predetermined position of the current limiting inductor, A discharge lamp lighting device comprising: a series circuit of a capacitor and a switching element connected at both ends via the intermediate tap; and a control circuit for applying a drive signal to the switching element every half cycle of the AC power supply. Wherein the control circuit performs switching for a period longer than a generation period of an oscillating current generated when the switching element is constantly turned on from the off state.
Since the drive signal generation period is configured to be longer than the oscillation signal generation period by inputting the drive signal to the element, the start of the discharge lamp can be improved and the number of components increases. Without this, a remarkable effect that the withstand voltage of the switching element can be reduced can be obtained.

[Brief description of the drawings]

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

FIG. 2 is an explanatory diagram showing waveforms of respective parts for explaining a first embodiment of the present invention.

FIG. 3 is a circuit diagram showing a second embodiment of the present invention.

FIG. 4 is a circuit diagram showing a third embodiment of the present invention.

FIG. 5 is a circuit diagram showing a fourth embodiment of the present invention.

FIG. 6 is a circuit configuration diagram showing a conventional example of the present invention.

FIG. 7 is an explanatory diagram showing waveforms of respective parts for explaining a conventional example of the present invention.

[Explanation of symbols]

 Reference Signs List 1 AC power supply 2 Current limiting inductor 3 Discharge lamp 5 Middle tap C1 Capacitor Q1 Switching element T Control circuit

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-59-211992 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H05B 41/14 360

Claims (1)

(57) [Claims] 1. An AC power supply, a discharge lamp connected to both ends of the AC power supply via current limiting inductors, an intermediate tap provided at a predetermined position of the current limiting inductor, and two ends of the AC power supply. A discharge lamp lighting device comprising: a series circuit of a capacitor and a switching element connected via the intermediate tap; and a control circuit that applies a drive signal to the switching element every half cycle of the AC power supply. The control circuit drives the switching element for a period longer than the generation period of the oscillating current generated when the switching element is turned on from the off state to the always on state.
By inputting a signal ,
A discharge lamp lighting device characterized in that the drive signal is generated for a longer period.