JPH0632312B2 - High-voltage pulse generator for discharge lamp - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a discharge lamp high-voltage pulse generator that boosts an AC voltage output from an inverter and supplies the boosted AC voltage to a discharge lamp.

[Conventional technology]

As a device for lighting a discharge lamp using an inverter,
For example, there is one as shown in FIG. In the figure, 1 is a power supply unit for obtaining a stable DC voltage from an AC power supply or a DC power supply, 2 is a DC power supply output from the power supply unit 1 is turned on (O
N), an inverter that outputs an AC voltage by turning it OFF, 3 is a step-up transformer that boosts the AC voltage and supplies it to the discharge lamp 4, and 5 is a secondary side of the step-up transformer 3 and the discharge lamp 4.
It is a ballast resistor interposed between and.

In the device configured as described above, the DC voltage output from the power supply unit 1 is converted into an AC voltage by the inverter 2, and this AC voltage is boosted by the boosting transformer 3 and supplied to the discharge lamp 4. At this time, the inverter 2 generates a voltage with a frequency of several kHz to several tens of kHz, and the AC voltage is increased by the step-up transformer 3 to a voltage of about 400v to 1000v. The high-voltage AC voltage causes the discharge lamp 4
Is lit.

[Problems to be Solved by the Invention]

However, since the temperature of the lamp (tube) rises when the discharge lamp is turned on, it is necessary to supply a lighting voltage of several kv to several tens of kv when the discharge lamp is once turned off and then turned on again. In the high-voltage generator of No. 3, since only a voltage of about 1000 V can be obtained as described above, there is a problem that the discharge lamp cannot be re-lighted until it is cooled, and the circuit shown in FIG. However, when a high voltage of several tens of kv is generated, there is a problem that the loss in the ballast resistor is large and heat is generated.

The present invention has been made by paying attention to such a problem, and can reliably turn on the discharge lamp even when it is hot,
Further, the present invention provides a high-voltage pulse generator for a discharge lamp with reduced heat generation.

[Means for Solving the Problems]

In the high-voltage pulse generator for a discharge lamp of the present invention, a ballast coil is interposed between the secondary side of the step-up transformer and the discharge lamp, and a high-voltage generating coil having a smaller number of turns than the ballast coil is connected to the ballast coil. Then, a capacitor is connected to one end of the high-voltage generating coil, and a charging / discharging switching element of the capacitor is connected to the other end of the coil, and the switching element is switching-controlled according to the cycle of the step-up transformer. Is provided, the capacitor is charged and discharged by the switching control of the pulse synchronization circuit to superimpose a high voltage on the ballast coil, and a ballast transformer wound around the ballast coil is provided with a control coil capable of controlling current, in an insulated state, The inductance is varied by controlling the current flowing through the control coil.

[Action]

In the high-voltage pulse generator for a discharge lamp of the present invention, a coil is used for the ballast, and the high voltage obtained by charging / discharging the capacitor is superimposed on the ballast coil. Therefore, even if the temperature of the discharge lamp is high, it is sufficient. A voltage that can be turned on is obtained, and heat generation can be reduced.

Further, by controlling the current flowing through the control coil, the inductance of the ballast coil can be varied, and the ballast suitable for the discharge lamp can be obtained.

〔Example〕

FIG. 1 is a circuit configuration diagram showing an embodiment of the present invention.
The same reference numerals as those in FIG. 3 indicate the same components. In the figure, 1 is a power supply unit that outputs a stable DC voltage, 2 is an inverter that converts the DC voltage into AC voltage, 3 is a step-up transformer that steps up the AC voltage output from the inverter 2, and 4 is a load. An electric lamp, 6 is a ballast coil interposed between the secondary side of the step-up transformer 3 and the discharge lamp 4, and 7 is a high voltage generating coil connected to the ballast coil 6, and the number of turns N of the high voltage generating coil 7 is N. ₁ is smaller than the number of turns N ₂ of the ballast coil 6 (N ₁ <N ₂ ). Reference numeral 8 denotes a control coil (number of turns N ₃ ) which is provided in a state of being insulated from the ballast coil 6 and which can control current, and constitutes a ballast transformer 9 together with the ballast coil 6 and the high voltage generating coil 7.

C ₁ is a capacitor connected to one end of the high voltage generating coil 7, and a DC power source E is connected in parallel with the capacitor. Q ₁ is a transistor connected to the other end of the high voltage generating coil 7 via a current limiting resistor R ₁ and is provided as a charging / discharging switching element of the capacitor C ₁ . ZNR is a surge absorber provided to protect the transistor Q ₁ , 10 is a pulse synchronization circuit that controls switching of the transistor Q ₁ according to the cycle of the step-up transformer 3, D _{1 to} D ₄ are diodes, Q ₂ is a transistor, R ₂ and R ₃ are resistors.

Next, the operation will be described with reference to the waveform chart of FIG. FIG. 2 shows the applied voltage at the start of lighting of the discharge lamp 4 and the gate voltage of the transistor Q ₁ at that time.

Similar to the device of FIG. 3, a voltage obtained by boosting the output AC voltage of the inverter 2 to several hundreds of volts by the step-up transformer 3 is applied to the discharge lamp 4, but at the start of lighting, a high voltage is superimposed as shown in FIG. The generated voltage is applied to the discharge lamp 4. That is, when the power is turned on, the capacitor C ₁ is rapidly charged by the DC power supply E, and after t ₁ [sec] time (after the charging time of the capacitor C ₁ elapses), the pulse synchronization circuit has the timing shown in FIG. A signal is applied from 10 to the gate of the transistor Q ₁ . This gate signal turns on the transistor Q _1, and the electric charge of the capacitor C ₁ is discharged through the high-voltage generating coil 7, the resistor R ₁ , and the transistor Q ₁ . Then, the switching control of the pulse synchronization circuit 10 charges and discharges the capacitor C _1, and the high voltage is superimposed on the ballast coil 6.

At this time, the voltage V generated in the high voltage generating coil 7
₁ is (L ₁ : inductance of the high voltage generating coil 7). The voltage V ₂ generated in the ballast coil 6 is Then, by substituting equation (a) into equation (b), Becomes Therefore, by increasing the turns ratio of N ₂ / N _i , a high-voltage pulse of several tens kV to several tens kV can be generated, and this high-voltage pulse is generated by the voltage V from the step-up transformer 5.
_It is superimposed on _T and given to the discharge lamp 4. Therefore, the discharge lamp 4 can be reliably turned on even when it is hot immediately after being turned off, and since the coil 6 is used for the ballast, heat generation can be reduced.

Then, when the discharge lamp 4 is turned on by the high-voltage pulse, the pulse synchronization circuit 10 detects that a current flows through the discharge lamp 4, and stops the gate signal to the transistor Q ₁ . As a result, the generation of the high voltage pulse is stopped, and the applied voltage during normal lighting is restored.

Here, in order to increase the turn ratio N ₂ / N ₁ in order to generate a high-voltage pulse, many ballast coils 6 must be wound, but if this is done, the inductance L ₂ of the ballast coil 6 will increase. This inductance L
₂ indicates that the output frequency of the inverter 2 is f [Hz],
L ₂ = 2πfL, and if this is large, it becomes difficult for current to flow. Therefore, in the present embodiment, the control coil 8 is provided in the ballast transformer 9, and when the pulse synchronization circuit 10 detects that a current flows in the discharge lamp 4, the transistor Q ₂ is turned off and both ends of the control coil 8 are turned on. Make it short. As a result, the inductance L ₂ of the high-voltage generating coil 7 of the transformer 9 and the ballast coil 6 becomes small, current easily flows, and the circuit loss decreases. At that time, the inductances L ₁ and L ₂ of the high-voltage generating coil 7 and the ballast coil 6 can be varied by controlling the current flowing through the control coil 8, and a ballast suitable for the discharge lamp 4 can be obtained. .

In the above embodiment, the required high voltage pulse can be arbitrarily generated by changing the winding ratio N ₂ / N ₁ of the high voltage generating coil 7 and the ballast coil 6, but the charging time of the capacitor C ₁ is small. By doing so, the discharge lamp 4 can be instantly turned on.

〔The invention's effect〕

As described above, according to the present invention, since the coil is used for the ballast and the high voltage obtained by charging / discharging the capacitor is superimposed on the ballast coil, the ballast is sufficiently lit even if the temperature of the discharge lamp is hot immediately after the light is turned off. There is an effect that a possible voltage is obtained, the discharge lamp can be reliably turned on, and heat generation can be reduced.

Further, by controlling the current flowing through the control coil, it is possible to change the inductance of the ballast coil and obtain the effect that the ballast suitable for the discharge lamp can be obtained.

[Brief description of drawings]

FIG. 1 is a circuit configuration diagram showing an embodiment of the present invention, FIG. 2 is a waveform diagram showing the operation of the circuit of FIG. 1, and FIG. 3 is a block diagram showing a conventional device. 1 ...... the power supply unit 2 ...... inverter 3 ...... step-up transformer 4 ...... discharge lamp 6 ...... ballast coil 7 ...... high voltage generating coil 8 ...... control coil 9 ...... ballast transformer C 1 _...... capacitor Q ₁ ...... Transistor (switching element)

Claims (1)

[Claims] 1. A high-voltage pulse generator for boosting an AC voltage output from an inverter by a step-up transformer and supplying it to a discharge lamp, wherein a ballast coil is interposed between the secondary side of the step-up transformer and the discharge lamp. At the same time, a high voltage generating coil having a smaller number of turns than the ballast coil is connected to the ballast coil, a capacitor is connected to one end side of the high voltage generating coil, and a charging / discharging switching element of the capacitor is connected to the other end side. , A pulse synchronization circuit for switching control of this switching element in accordance with the cycle of the step-up transformer is provided, the capacitor is charged and discharged by the switching control of the pulse synchronization circuit to superimpose a high voltage on the ballast coil, and the ballast coil is wound. In the turned ballast transformer, a control coil capable of current control is installed in an insulated state, Discharge lamps high voltage pulse generating device which controls the current flowing in the control coil is characterized in that so as to vary the inductance.