JPS6316752B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a lighting voltage control device for an electric display panel that lights up a large number of incandescent lamps arranged vertically and horizontally in a pattern.

It is desirable to supply incandescent lamps with a rated voltage, and conventional road display boards and the like have been able to adjust the supply voltage by switching taps on a power transformer. However, in areas where the power supply voltage fluctuates relatively widely, it is not possible to switch the taps frequently, and voltages that exceed the lamp's rating are often applied, which has a significant effect on the lamp's lifespan. Incidentally, if LO is the life when the applied voltage is VO and L1 is the life when the applied voltage is V1, then in the case of an incandescent lamp, the relationship is L1/Lo=(V1/Vo) ^-13.5 (1) For example, with a 5% voltage increase, the life will be approximately halved, as L1/Lo=1.05 ^-13.5 ≒0.5 (2).

The present invention aims to solve the above problems, and instead of adjusting the power supply voltage, it utilizes three-terminal switching elements such as triacs and SCRs to control the lighting of each incandescent lamp on the electronic display panel. By changing the ignition phase, the lamp life is prevented from being shortened due to voltage fluctuations.

The present invention will be explained in detail below with reference to embodiment figures. 1st
In the illustrated embodiment, 1 is a power transformer, 2 is an incandescent lamp constituting an electronic display panel, and 3 is a three-terminal switching element connected to each incandescent lamp 2 in series. The control terminals of each three-terminal switching element 3 are individually controlled by the ignition pulse generation circuit 4 in accordance with lighting pattern data transmitted from the main control circuit 11. In other words, characters and graphics are displayed on the electronic display panel by means of incandescent lamps connected in series with these ignited switching elements. The present invention changes the ignition phase of the three-terminal switching element 3 that controls on/off of the incandescent lamp 2 in accordance with voltage fluctuations, and its main part is a measuring element having the same resistance as the lamp 2. A series connection of a resistor 10 and a three-terminal switching element 3 is provided in parallel with the circuit of the other lamp 2, and the three-terminal switching element 3 in series with the resistor 10 is connected to the other three terminals in series for each half cycle of the power supply. The ignition pulse is applied in the same phase as the switching element 3, the voltage across the resistor is measured by the voltage measuring circuit 5, and the comparison circuit 6 compares this voltage with a set value, and the control is performed by the output of the comparison circuit 6. ignition phase control circuit 7. The output of the comparison circuit 6 is proportional to the difference between the voltage value measured by the voltage measurement circuit 5 and the reference value preset in the setting section 8, that is, the error voltage. Using the fall of the output pulse of the zero cross detection circuit 9, which generates a pulse when the instantaneous value becomes 0, as the starting point of time, the output of the comparison circuit 6 fires the switching element 3 so that the error voltage becomes 0. The starting point is determined and the pulse generation point of the ignition pulse generating circuit 4 is controlled. Resistor 10 is lamp 2
Since it has the same resistance value, if we consider resistor 10 as a lamp, it is equivalent to a lamp that is always on (the other lamps are blinking based on pattern data by commands from the main control circuit), and this resistance 10 is detected by the voltage measuring circuit 5 and compared with the reference value set in the setting section 8 by the comparing circuit 6, and the difference between the two is 0.
A feedback system is configured to control the ignition phase control circuit 7 so that the ignition phase control circuit 7 achieves the following. According to this configuration, the voltage across the resistor equivalent to the lamp is always controlled to be the correct reference voltage, and therefore the voltage across the lamp 2 is also set to the reference value, and the output of the comparator circuit 6, that is, the error and the ignition There is no need to give complicated consideration to the functional form between the phase shift value and the voltage control.

The ignition pulse generation circuit 4 is a two-input AND gate corresponding to each three-terminal switching element 3. A pattern data signal from the main control circuit 11 is applied to one input terminal, and each AND gate is applied to the other input terminal. The ignition pulses emitted from the ignition phase control circuit 7 are applied all at once.

FIG. 2 shows the operation of the above-mentioned embodiment device under two power supply voltages, and the solid line waveforms at power supply voltages VO and V1 are the actual voltage waveforms applied to the lamp, and their effective values are It has reached the predetermined value. The reference value is set in the setting section 8 as follows.
If you turn on any lamp in the operating state of the entire circuit and measure the voltage between A and B using an AC voltmeter (indicating the effective value) and change the setting value of the setting section 8, the voltage measurement circuit The difference between the output of No. 5 (which is constant in the short term) and the output of the setting section changes, the lighting phase of the lamp changes accordingly, and the voltage between AB changes. Therefore, if the setting value of the setting unit 8 is fixed when the AB voltage reaches a predetermined value, this becomes the reference value. The voltage measurement circuit 5, the comparison circuit 6, the setting section 8, and the ignition phase control circuit 7 may be of an analog type or a digital type.

The present invention is constructed as described above, and utilizes a power three-terminal switching element for pattern-lighting incandescent lamps, which are usually used in the thousands in electric display panels, and shifts the ignition phase of the incandescent lamps. As a result, the effective value of the voltage applied to the lamp is corrected in response to fluctuations in the power supply voltage, so that the lamp life can be greatly improved by simply adding a relatively inexpensive electronic circuit.

[Brief explanation of the drawing]

FIG. 1 is a block circuit diagram showing one embodiment of the present invention, and FIG. 2 is a voltage waveform diagram for explaining the operation of the same. 1...Power transformer, 2...Incandescent lamp, 3...
...Three-terminal switching element, 4...Ignition pulse generation circuit, 5...Voltage measurement circuit, 6...Comparison circuit,
7... Ignition phase control circuit, 8... Setting section, 9...
Zero cross detection circuit, 10... Lamp equivalent resistance.

Claims (1)

[Claims] 1. In an electronic display panel in which switching elements are connected in series to a plurality of incandescent lamps arranged vertically and horizontally, and any switching element is made conductive based on pattern information transmitted from the main control panel to display characters and figures. , a series connection of the same switching element as the above switching element and a resistor having the same resistance value as the above lamp is connected to a power supply in parallel with the series connection group of the above lamp and the switching element, and the voltage across the above resistance is measured. A measurement circuit and a comparison circuit that compares this power supply voltage with a set value are provided, and the conduction phase angle of all the switching elements is shifted by the output of the comparison circuit so that the difference between the voltage across the resistor and the set value becomes 0. 1. A lighting voltage control device for an electronic display panel, comprising an ignition phase control circuit for controlling the ignition phase.