JPS59128458A - Level display apparatus - Google Patents

Abstract

PURPOSE:To simplify circuit constitution, by enabling the dynamic driving of a light emitting element without generation radio noise by controlling a signal change-over circuit, a latch circuit and a display circuit by predetermined operation timing. CONSTITUTION:A level display apparatus is equipped with a circuit 4 for changing over the level signal of each channel, a circuit 5 for detecting the level of the change-over output signal, display groups 6, 7 provided at every channel in order to display the level of a signal in response to detection output by the number of display operations and circuits 81-83 each for latching the output of the detection circuit 5. In this case, the operation timings of the change-over circuit 4 and the latch circuits 81-83 are controlled by clocks CL1, CL2 while the display circuits 6, 7 are subjected to driving control at every channel by using driving signals S1, S2 each having a drive wave form such as a sine wave or a triangular wave and the operation timings are synchronously set to the time when the signals S1, S2 rise from a zero level.

Description

[Detailed description of the invention]

The present invention relates to a level display device that displays the signal level of each channel in stereo. In such a level display device, multiple light emitting diodes are placed on the front panel of the stereo for each channel, and the signal level is displayed by activating the number of light emitting diodes corresponding to the signal level. There is something I did. By the way, when such a light emitting diode is dynamically driven with a drive signal having a waveform with a steep rise, such as a rectangular wave, so-called radio noise occurs. This radio noise has an undesirable effect on equipment such as tuners. To eliminate interference caused by radio noise, electromagnetic shielding is recommended, but manufacturing costs are high. It is also possible to use, for example, static drive instead of dynamic drive, but this would complicate the circuit configuration and increase the cost of integrating the circuit. SUMMARY OF THE INVENTION An object of the present invention is to provide a level display device that can sufficiently reduce the generation of radio noise when dynamically driving a light emitting element such as a light emitting diode, and that can be manufactured at low manufacturing cost, for example when integrating circuits. shall be. In order to achieve this object, the present invention provides a circuit that latches the signal level detection output, and controls the operation timing of the circuit that switches the signal of each channel and this circuit using a clock signal, A display having light emitting elements is driven and controlled for each channel by a drive signal having a waveform such as a sine wave or a triangular wave, and the operation timing is set in synchronization with when the drive signal rises from a zero level. Hereinafter, the present invention will be described in detail based on an embodiment shown in the drawings. FIG. 1 is an electrical circuit diagram of this embodiment. The level display device 1 of this embodiment will be explained by applying it to signal level display of left and right channels of a two-channel stereo. This level display device 1 includes a left channel and a right channel signal detection circuit 2.3. Both signal detection circuits 2 and 3 each have a signal switching circuit 4 that switches the signal of each channel.
connected to. The signal switching circuit 4 includes a signal radar that detects the level of the signal from the signal detection circuit 2.3 that is switched and output by the signal switching circuit 4.

[Connected to the loop detection circuit 5.] This level display device 1 also includes display circuits 6 and 7 for each channel. The image display circuits 6 and 7 each have a plurality of light emitting elements, for example, light emitting diodes 61, 62, 71, 72, . The image display circuits 6, 7 also include light emitting diodes 61, 62, . . . in a number corresponding to the output level of the signal level detection circuit 5.
, 71, 72, . . . are displayed. Between the signal level detection circuit 5 and the image display circuits 6, 7, latch circuits 81, 82, . . . for latching the output of the signal level detection circuit 5 are provided. This level display device 1 has such a configuration. Next, each circuit will be explained in detail. The signal detection circuits 2 and 3 each have an input terminal 21.31 into which a signal from a signal source (not shown) is input, an amplification detector 22.32 that amplifies this signal, and smoothing the output of the amplification detector 22.32. It has smoothing capacitors 23 and 33. The signal switching circuit 4 includes a movable terminal 41 and two individual contacts 42 .
43. One individual contact 42 is connected to the output section of the signal detection circuit 2 on the left channel side, and the other individual contact 4
3 are respectively connected to the output section of the signal detection circuit 3 on the right channel side. The pre-signal level detection circuit 5 includes a plurality of comparators 51, 52...
・Has. The negative phase side input terminals (→ are respectively commonly connected to the movable terminal 41 of the signal switching circuit 4. The positive phase side input terminals (G) of each comparator 51, 52... A bias is applied as a reference for comparison through each of these resistors.The display circuits 6.7 each have a light emitting diode 61.6.
2..., 71.72... The anodes of one of the light emitting diodes 61, 62, . . . are connected in common and also connected to the first drive signal input terminal 9. Each cathode of one of the diodes 61, 62, . . . is individually connected to the output section of the latch circuit 81, 82, . The anodes of the other diodes 71, 72, . The cathodes of the other diodes 71, 72, . . . are individually connected to the output portions of the latch circuits 81, 82, . In such a configuration, the signal switching circuit 4 receives a first clock signal CL having a waveform as shown in FIG.
processing is applied via the first clock signal input terminal 11. This signal switching circuit 4 is configured such that the 0T@ terminal 41 moves between the individual contacts 42 and 43 in response to the rise and fall of the first clock signal CL. A second clock signal CL2 having a waveform as shown in FIG. 2(b) is applied to the latch circuits 81, 82, . . . via the second clock signal input terminal 12. Each latch circuit 81
．． 82... outputs the latched signal in response to the second clock signal CL2. A first drive signal S0 having a triangular waveform as shown in FIG. 2 is applied to one display circuit 6 via a first drive signal input terminal 8. A second drive signal S2 having a triangular waveform as shown in FIG. 2(d) is applied to the other display circuit 7 via the second drive signal input terminal 10.This display The circuit 7 is driven by the second drive signal S2. Next, the operation will be explained. Now, between time 0 and time 1, when the signal switching circuit 4 is switching as shown in the figure, Latch circuit 51.5
2..., the output of the signal level detection circuit 5 corresponding to the signal of the signal detection circuit 2 on the left channel side is latched. At time L1, the signal switching circuit 4 is activated by the fall of the first clock signal CL1, and the latch circuit 81.
82... are operated by the second clock signal CL2. As a result, the movable terminal 41 of the signal switching circuit 4 is
At the same time, the latch output corresponding to the output of the signal level detection circuit 5 is applied to the display circuits 6 and 7 from the latch circuits 81 and 82°°. Between this time [1 and t2, the first drive signal S1 is not applied to the display circuit 6 on the right channel side, and the second drive signal S2 is applied to the display circuit 7 on the left channel side. However. Therefore, the display circuit 7 on the left channel side receives the second drive signal S.
2, and only the four light emitting diodes 71, 72, . . . corresponding to the latch output, are operated to emit light. In this case, since the light emitting diodes 71 and 72 are driven by the second drive signal S2 having a triangular waveform, the generation of radio noise can be greatly reduced. At time [2], the display circuit 6 on the right channel side is operated in the same manner as described above. Although a light emitting diode was provided as a light emitting element in the above embodiment, it is also possible to provide a fluorescent display tube by converting each drive signal into a voltage instead of a current. Further, in the above embodiment, the drive signal has a triangular waveform, but it may also have a sine waveform or other waveform containing a small proportion of K subcomponents. As described above, according to the present invention, (a circuit is provided that latches the 4 yellow outputs of level 4, and the operation timing of the circuit that switches the signal of each channel and this latch circuit is controlled by a clock signal, A display circuit for each channel having a light emitting element is driven and controlled by a drive signal having a waveform such as a sine wave or a triangular wave, and synchronization is set when the drive signal rises from a zero level, so that the light emitting element generates radio noise. It is possible to dynamically drive the device without any trouble, and since the structure is simple, manufacturing costs can be reduced.

[Brief explanation of the drawing]

The drawings show one embodiment of the present invention, and FIG. 1 is an electric circuit diagram;
Figure $2 is a signal waveform diagram used to explain the operation. ■... Level display device, 2, 3... Signal detection circuit,
4 Signal switching circuit, 5... Signal level detection circuit, 6.7
・Display circuit, 61, 62, 63, 71, 72.73・
・Light-emitting diode, 81, 82.83...Latch circuit,
9, 10... Drive signal input terminal, 11, 12 Clock signal input terminal, CL, +ct2°° clock number, S□ signal 2... Drive signal patent applicant ROHM Co., Ltd. agent Patent attorney Kazuhide Okada

Claims (1)

[Claims] (1) A level display device that displays signal levels of multiple channels, which includes a circuit that switches the level signal of each channel, a circuit that detects the level of the signal switched and output by the switching circuit, and the signal level detection circuit. The signal level is displayed by the number of display operations of the light emitting elements in response to the output of the display group provided for each channel, and the signal level provided between the signal level detection circuit and the display group. and a circuit that latches the output of the level detection circuit, the operation timing of the switching circuit and the latch circuit is controlled by a clock signal, and the display circuit is controlled for each channel by a drive signal having a drive waveform such as a sine wave or a triangular wave. 1. A level display device characterized in that drive control is performed and the operation timing is set in synchronization with when the drive signal rises from a zero level.