JPH04140071A - Discharge lamp lighting device - Google Patents

Abstract

PURPOSE:To prevent intermittent oscillation by having an oscillation circuit, which controls the changeover of on/off of a transistor, and a changeover time control means, which controls the on/off changeover time by said oscillation circuit. CONSTITUTION:A power source 9 is provided between the base and the emitter of a transistor 7, and that power source 9 supplies the base of the transistor 7 with a current Ia, when an output signal is given from an oscillator 11. Moreover, a power source 10 is provided between the base and the emitter of a transistor 8, and it supplies the base of the transistor 8 with a current Ib, when an output signal is given from the oscillator 11. And, when both power sources 9 and 10 are alternately supplied with output signals from the oscillator 11, the transistor 7 and the transistor 8 turned on and turned off alternately, so DC voltage is converted into AC voltage. Moreover, an inverter 4 is provided with a changeover time controller 17, whereby the signal output time from the oscillator can be adjusted optionally.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a discharge lamp lighting device for lighting a discharge lamp using a high-frequency power source, and in particular, to a discharge lamp lighting device for lighting a discharge lamp using a high-frequency power source, and particularly for preventing intermittent oscillation of an inverter circuit. Regarding technology.

(Prior art) Currently, as a lighting circuit for lighting discharge lamps such as fluorescent lamps,
High frequency lighting circuits are often used.

Figure 4 shows a conventional example of a lighting circuit using a half-bridge inverter.
A voltage of 0 to 60 Hz supplied from a commercial power supply 1 is full-wave rectified by a rectifier 2, smoothed by a smoothing capacitor 3, and then supplied to an inverter 4.

The inverter 4 is configured by connecting in parallel two diodes 5 and 6 connected in series and two transistors 7.8 connected in series, and the midpoint between the diodes 5.6 and the transistor 7.8. Intermediate points are connected. This connection point is also connected to one end of a choke coil 12, and the other end of the choke coil 12 is connected to one end of a discharge lamp 14 connected in parallel to a starting capacitor 13.

The other end of the discharge lamp 14 is branched into two systems, one of which is connected to the positive side of the DC power source via a capacitor 15, and the other connected to the negative side of the DC power source via a capacitor 16.

Further, a current source 9 is disposed between the base and emitter of the transistor 7, and the current source 9 operates under the control of an oscillator 11 to supply current to the base of the transistor 7.

Similarly, a current source 10 is provided between the base and emitter of the transistor 80, and operates under the control of an oscillator 11 to supply current to the base of the transistor 8.

Therefore, when the output signal is given from the oscillator 11 to the current source 9 and the current 1a flows into the base of the transistor 7, the transistor 7 becomes conductive, so that from the positive side of the DC power supply, the transistor 7, the coil 12, the discharge lamp 14, and the capacitor are connected. Current flows through 16. Conversely, when the current 1b flows into the base of the transistor 8 and becomes conductive, the current flows through the capacitor 15, the discharge lamp 14, the coil 12, and the transistor 8.

Therefore, an alternating current voltage is applied to both ends of the discharge lamp 14, and thereby the discharge lamp 14 is lit.

FIG. 5 shows the currents Ia and Ib flowing into the transistor 7.8.
Conventionally, both the on time and off time of each current 1a and Ib are constant Δt.
It was set to generate alternating current voltage.

(Problems to be Solved by the Invention) However, in such a conventional discharge lamp lighting device, as shown in FIG. 5, the current 1a supplied to the base of the transistor 7 and the current 1b supplied to the base of the transistor 8 are Since the switching time Δt is always constant, the voltage waveform at the time of starting the inverter oscillates greatly in the direction in which it is first applied. For this reason, as shown in FIG. 6, for example, the output voltage waveform of the inverter 4 is no longer symmetrical on the positive and negative sides, and it takes a long time to stabilize, resulting in intermittent It had the disadvantage of causing oscillation.

The present invention was made in order to solve such conventional problems, and its purpose is to provide a discharge lamp lighting device that can prevent intermittent oscillation.

[Structure of the invention]

(Means for Solving the Problems) In order to achieve the above object, the present invention converts a DC voltage obtained by rectifying and smoothing a commercial power source into an AC voltage of a desired frequency using an inverter circuit having a pair of transistors. In a discharge lamp lighting device that converts and lights a discharge lamp at high frequency,
The device is characterized in that it includes an oscillation circuit that controls switching between on and off of each of the transistors, and switching time control means that controls the on/off switching time of the oscillation circuit.

Further, the switching time control means is characterized in that the switching time control means controls the on-time of the transistor that is turned on first when the inverter is started so as to be shorter than the on-time during normal operation.

(Function) With the configuration as described above, the on time and off time of the transistors constituting the inverter circuit can be adjusted as desired. Therefore, when the inverter is started, if the on-time of the transistor that is turned on first is made shorter than the normal on-time, the output waveform will not fluctuate greatly and will become a stable waveform in a short time. This makes it possible to prevent intermittent oscillation.

(Embodiment) FIG. 1 is a configuration diagram showing an embodiment of the present invention. In addition,
In this figure, the same parts as those in FIG. 4 described in the prior art are given the same reference numerals, and the explanation thereof will be omitted.

As shown in FIG. 1, a current source 9 is provided between the base and emitter of the transistor 7 constituting the inverter 4, and when an output signal is applied from the oscillator 11, the current source 9 is connected to the base of the transistor 7. A current 1a is supplied to.

Similarly, a current source 10 is installed between the base and emitter of the transistor 8, and when an output signal is given from the oscillator 11, a current 1b is supplied to the base of the transistor 8.

Then, when output signals are alternately supplied from the oscillator 11 to both current sources 9 and 10, the transistors 7 and 8
operates alternately on and off, so DC voltage is converted to AC voltage.

Furthermore, the inverter 4 is provided with a switching time control section 17, which allows the signal output time of the oscillator 11 to be adjusted as desired.

Therefore, the current I supplied to the base of transistor 7.8
The output times of a and Ib can be adjusted.

Now, for example, as shown in FIG. 2, the output time of the current Ia at the time of starting the inverter is set to half the other output time Δt (Δt/2). Then, inverter 4
As shown in Figure 3, the voltage waveform at It doesn't take much time.

In this manner, in this embodiment, the output time of the current Ia supplied to the base of the transistor 7 is set to half (Δt/2) of the normal output time Δt only when the inverter 4 is started.

Therefore, the waveform of the output voltage of the inverter 4 becomes substantially symmetrical on the plus side and the minus side, so that the voltage waveform becomes stable in a short time. Thereby, intermittent oscillation of the inverter 4 can be prevented.

In this embodiment, an example has been described in which only the output time of the current Ia at the time of starting the inverter is shortened, but the present invention is not limited to this, and various output time adjustments are possible.

〔Effect of the invention〕

As explained above, in the discharge lamp lighting device according to the present invention, since the inverter circuit is started by adjusting the on/off time of the transistors constituting the inverter circuit, intermittent oscillation can be prevented. Effects can be obtained.

[Brief explanation of the drawing]

Figure 1 is a configuration diagram showing an embodiment of the present invention, Figure 2 is a time chart of currents 1a and Ib in this embodiment, and Figure 3 is a waveform diagram of the inverter output voltage in this embodiment. Further, FIG. 4 is a configuration diagram showing a conventional example, and FIG. 5 shows a current Ia in the conventional example. The time chart of Ib, FIG. 6, is a waveform diagram of the inverter output voltage in a conventional example. 1... Commercial power supply 2... Rectifier 3... Smoothing capacitor 4... Inverter 7.8... Transistor 9.10... Current source 11... Oscillator 14... Discharge lamp 17.・Switching time control section

Claims (2)

[Claims] (1) The DC voltage obtained by rectifying and smoothing the commercial power supply is 1
In a discharge lamp lighting device that converts an AC voltage of a desired frequency into an AC voltage of a desired frequency using an inverter circuit having a pair of transistors and lights a discharge lamp at a high frequency, the discharge lamp lighting device includes an oscillation circuit that switches and controls the on/off of each transistor, and - A discharge lamp lighting device comprising: switching time control means for controlling off switching time; (2) The discharge lamp lighting device according to claim 1, wherein the switching time control means controls the on-time of the transistor that is turned on first when the inverter is started to be shorter than the on-time during normal operation.