JPH04286895A - Discharge lamp lighting control device - Google Patents

Abstract

PURPOSE:To change pulse output wave form immediately, by an external input signal. CONSTITUTION:A comparator 4, a capacitor C1 and resistors R1 and R2, which inspect oscillation condition, are provided, to obtain an external input signal Vc. AND gates G1 and G2 which switch outputs from a starting pulse generator 2 and a pulse generation circuit 1 by means of the external input signal Vc are provided. As oscillation is not active at the time of starting, the external input signal Vc becomes H and the AND gate G1 opens. A starting pulse from the starting pulse generator 2 is inputted to the gate of a transistor Tr2, and a lighting circuit 5 starts oscillation. After starting, oscillation starts, voltage is detected, and the external input signal Vc become to L level, and the AND gate G2 opens. Therefore, a pulse width modulated signal from the pulse generation circuit 1 is input to the gate of the transistor Tr2.

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 control device for controlling a discharge lamp lighting circuit by controlling a discharge lamp lighting circuit using a pulse width modulated output pulse signal.

0002

[Prior Art] A pulse generation circuit that outputs a pulse width modulated output pulse signal to control a discharge lamp lighting circuit is
It is structured as follows. That is, there is a buffer circuit that latches the section setting data output from the CPU of the output pulse signal, a counter circuit that counts the section setting data and outputs a ripple carry signal, and a counter circuit that counts the next section setting data using the ripple carry signal. The pulse generation circuit is composed of a load circuit that generates a load signal to start, and a toggle flip-flop circuit that generates a single-phase output waveform based on the load signal.

[0003] A pulse-width modulated single-phase output waveform is obtained from the toggle flip-flop circuit, and the switching elements of the discharge lamp lighting circuit are controlled on and off to control the lighting of the discharge lamp. Conventional discharge lamp lighting control devices are controlled by a CPU with slow processing speed, so when changing section setting data using an external input signal, it takes several μ.
s command was required several times, and therefore it took a long time to change the section setting data and change the single-phase output waveform after receiving a signal from the outside.

0004

[Problems to be Solved by the Invention] However, in the conventional example described above, it is impossible to change the single-phase output waveform instantaneously by an external input signal, and therefore the resonant circuit of the discharge lamp lighting circuit changes. In the case of a circuit including a self-excited switching element whose output waveform must be changed by changing the output waveform, control is impossible.

The present invention has been proposed in view of the above-mentioned points, and it is an object of the present invention to provide a discharge lamp lighting control device that makes it possible to instantly change the output waveform by an external input signal. .

[0006]

[Means for Solving the Problems] The present invention provides a starting pulse generator that generates a starting pulse to control a second switching element when starting a discharge lamp, and a starting pulse generator that generates a starting pulse after a predetermined time after starting. A switching means is provided for switching the signal from the pulse generating circuit to the signal from the pulse generating circuit.

[0007]

[Function] At the time of starting, the switching means controls and starts the second switching element of the lighting circuit using the starting pulse from the starting pulse generator, and after a predetermined time after starting, the switching means starts the lighting circuit. The means switches the signal from the starting pulse generator to the signal from the pulse generating circuit.

[0008]

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings. Figure 1 shows a block circuit diagram. Pulse generation circuit 1
As described above, the single-phase output waveform is created and outputted based on the section setting data from the CPU. Also,
Separately from this pulse generating circuit 1, a starting pulse generator 2 is provided which generates a starting pulse at the time of starting.

The lighting circuit 5 for lighting the discharge lamp 3 is composed of a bipolar transistor Tr1 which performs switching by circuit resonance, a MOS transistor Tr2 which performs switching by the outputs of the pulse generating circuits 1 and 2, and the like. Note that this transistor Tr2 constitutes a second switching element. Furthermore, dividing resistors R1 and R2 are connected to the emitter of the transistor Tr1.
is connected, and the divided voltage is input to the comparator 4 from the dividing point, and the comparator 4 compares it with the reference voltage. The output of comparator 4 is smoothed by capacitor C1, and when there is no oscillation, it outputs H level, and when there is oscillation, it outputs L level.
Output the level. This signal is input to the logic circuit as an external input signal Vc.

The logic circuit includes AND gates G1 and G2
, OR gate G3, inverter gate G4, G5
It is composed of etc. The external input signal Vc via the inverter gates G4 and G5 and the pulse from the starting pulse generator 2 are input to the AND gate G1. Also, the AND gate G2 has an inverter gate G4.
The external input signal Vc inverted at
A pulse-width modulated signal is input.

The outputs of the AND gates G1 and G2 are input to the gate of the transistor Tr2 via an OR gate G3. These logic circuits constitute a switching means. FIG. 2 shows operating waveform diagrams, where (a) shows the output of the starting pulse generator 2, (b) shows the output of the pulse generating circuit 1, and (c) shows the output waveform of the OR gate G3.
(d) shows the external input signal Vc.

When the power is turned on now, since there is no oscillation, no voltage is detected at the resistor R2, the output of the comparator 4 becomes H level, and the external input signal Vc becomes as shown in FIG. 2(d).
), it becomes H level. Therefore, the AND gate G2 is closed, the AND gate G1 is opened, and the starting pulse from the starting pulse generator 2 is inputted to the gate of the transistor Tr2 via the OR gate G3, and the lighting circuit 5 starts oscillating.

After starting, oscillation starts and the voltage is detected by the resistor R2, and when it exceeds the reference voltage, the comparator 4
The output is inverted and outputs L level, and the capacitor C1
charge is discharged. Therefore, the external input signal Vc is L
level, AND gate G1 closes and AND gate G2 opens. Therefore, as shown in FIG. 2(c), when the external input signal Vc becomes L level, the pulse width modulated signal from the pulse generating circuit 1 is input to the gate of the transistor Tr2.

In this way, the starting pulse from the starting pulse generator 2 and the preheating pulse from the pulse generating circuit 1 are used as the external input signal Vc indicating the oscillation of the lighting circuit 5.
You can switch instantly. Therefore, it is possible to control a discharge lamp lighting circuit using a self-excited type.

[0015]

As described above, the present invention includes a starting pulse generator that generates a starting pulse to control the second switching element when starting a discharge lamp, and a starting pulse generator that generates a starting pulse to control the second switching element when starting a discharge lamp, and The switching means switches the signal from the pulse generator to the signal from the pulse generation circuit, so that at the time of starting, the switching means switches the second switching element of the lighting circuit using the starting pulse from the starting pulse generator. This has the effect that the starting pulse generator can be controlled to start, and after a predetermined period of time after starting, the switching means can switch the signal from the starting pulse generator to the signal from the pulse generating circuit.

[Brief explanation of the drawing]

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

FIG. 2 is an operational waveform diagram.

[Explanation of symbols]

1 Pulse generation circuit 2 Start pulse generator 3 Discharge lamp 5. Lighting circuit

Claims (1)

[Claims] 1. A lighting circuit having a second switching element that controls on/off of a first switching element of an oscillation circuit that lights a discharge lamp, and a pulse width modulation that can arbitrarily set the H level and L level sections. In the discharge lamp lighting control device, the discharge lamp lighting control device includes a pulse generating circuit that controls on/off the second switching element based on a signal generated by the discharge lamp, and a starting pulse that generates a starting pulse to control the second switching element when starting the discharge lamp. A discharge lamp lighting control device comprising a pulse generator and a switching means for switching a signal from the starting pulse generator to a signal from a pulse generating circuit after a predetermined time after starting.