JPS5854379A - Braun tube driving circuit - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a switching type cathode ray tube (hereinafter referred to as CRT) drive circuit that enables display of several intermediate tones.

FIG. 1 shows a conventional switching type CRT drive circuit capable of displaying halftones. In FIG. 1, 1 is a load resistance of the CRT drive circuit, 2 is a drive transistor, 3 is a black and white binary signal generation source, 4 is a halftone control signal generation source, 5 is a CRT cathode, 6 is a CRT control grid, 7 is CRT
shows.

In the conventional circuit having the above configuration, the drive transistor 2 is designed to function as a common base circuit. This is often used in broadband amplifier circuits that place emphasis on high-frequency characteristics because it can reduce the effects of the Miller effect when considering the characteristics of the transistor. When displaying characters, figures, etc. with constant brightness, the signal source should be black and white 2#! [
Only signal source 3 is sufficient, but if you also want to display intermediate tones,
2, a black and white binary signal generation source 3 and a halftone control signal generation source 4
Two signal sources are required. Further, when displaying halftones using these two signal generation sources, the drive transistor 2 must have a function that can realize an intermediate conduction state in addition to being on and off. That is, the drive transistor 2 must have the function of performing analog operation.

When displaying halftones with such a circuit, for example, assuming that the output level of the drive transistor 2 is exactly half, the collector voltage vo of the drive transistor is vo=)(vcc-Eb)...・・・・・・・・・
Takes the value of (1). Here, vcc is the power supply voltage, and Eb is the pace voltage of the drive transistor 2.

The collector loss of the drive transistor 2 is maximum when the value is expressed by the above formula.Now, the relationship between the emitter resistance RE and the load resistance 1 (resistance value is RI) is RL.
> If RE is the collector loss and Pe is the collector loss, then the collector loss pcFi Pc=+・(vco-Eb)2/RL・・・・・・・・・
... is expressed as (2). This is equal to the maximum collector loss when the transistor is operated as an analog amplifier.

Therefore, in the conventional CRT driving circuit capable of displaying the above-mentioned halftones, the switching method adopted to reduce the collector loss of the transistor is used.
The advantage of the drive circuit is completely lost, and sufficient heat dissipation design for collector loss is required.

Furthermore, problems such as deterioration of high frequency characteristics due to the large heat radiator and unnecessary radio wave radiation occur, which poses a drawback in that it becomes a major hindrance to widening the band of the circuit.

SUMMARY OF THE INVENTION An object of the present invention is to provide a CRT drive circuit which eliminates the above-mentioned drawbacks of the prior art, suppresses the collector loss of the drive transistor, and easily achieves a wide band.

The present invention provides an output terminal, a first drive circuit connected to a cathode of a cathode ray tube, and an input terminal connected to one of a black and white binary signal generation source and a halftone control signal generation source, and an output terminal. is connected to the control grid of the cathode ray tube, and has an input terminal connected to the other of the black and white binary signal generation source and the halftone control signal generation source, the first and second drive circuits The feature is that the above object is achieved by performing a switching operation.

An embodiment of the present invention is shown in FIG. In FIG. 2, the same parts as in FIG. 1 are given the same reference numerals. 8 is a drive transistor, and 9 is a load resistance of the drive transistor 8. As is clear from the figure, the black and white binary signal generation source 3 is connected to the input terminal of the drive transistor 2.
The output end is connected to the CRT cathode 5. Further, the input terminal of the drive transistor 8 is connected to the halftone control signal generation source 4.
According to this embodiment, as will be clear from the description below, the drive transistors 2 and 8 have two states, a saturated state and a cutoff state. You can also display intermediate tones just by defeating the
A switching transistor can be used as the drive transistor 2.8.

The operation of this embodiment will be explained below using FIG. 2.

When displaying black and white binary information such as text and figures,
The driving transistor 2.8 is turned on and off as follows. First, when displaying white, the drive transistor 2 is turned on by the black and white binary signal generation source 3, and the drive transistor 8 is turned on by the halftone control signal generation source 4. Then, the potential difference between the CRT cathode and the control grid becomes zero, and white is displayed on the CRT image plane. On the other hand, when displaying black, control is performed so that the drive transistor 2 is turned off and the drive transistor 8 is turned off. Then, the potential difference between the cathode and the control grid will be approximately Vcc+VEE (however, VEE
is the power supply voltage of the drive transistor 8), the electrons emitted from the cathode cannot pass through the control grid, and black is displayed on the CRT screen.

On the other hand, when displaying halftones, the driving transistors 2 and 8 are turned on and off as follows. First, when the drive transistor 2 is turned on and the drive transistor 8 is turned off, the potential difference between the cathode and the cositrol grid is approximately V.
EE, and a halftone of -1 is displayed. Furthermore, when the drive transistor 2 is controlled to be turned off and the drive transistor 8 is turned on, the potential difference between the cathode and the control grid becomes approximately vcc, and when vEE and vcc are set to different values, a second halftone is obtained. These are summarized in Table 1.

In Table 1, ON means the Tr saturation state, OFF means the FiTr cutoff state, and Ebt l Eb2 means the drive transistor 2.8, respectively.
Connected to Kyudenryo voltage.

As described above, in this embodiment, the drive transistor 2 only needs to handle black and white binary signals, and the drive transistor 8 only needs to handle halftone control signals, so a switching transistor can be used as the drive transistor 2.8. Therefore, the transistor can be operated in its original low collector loss state.

Note that in this embodiment, the drive transistors 2 and 8 are each N
Although the driving transistor 8 is constructed of PN and PNP type transistors, and the collector loss and the power consumption of the power supplies VCC and VEE are minimized at the black level, the drive transistor 8 can also be constructed of an NPN type transistor. However, at this time, the polarity of the halftone control signal generation source 4 and the polarity of VEE are reversed. Further, at the black level, the transistor 2 is turned off and the transistor 8 is turned on, resulting in a disadvantage that the power consumption of the load resistor 9 increases.

Furthermore, it is also possible to replace the black and white binary signal generation source 3 and the halftone control signal generation source 4 in the above embodiment, paying attention to the polarity.

Further, although the above embodiment is shown with a grounded base, it goes without saying that the same effect as the above embodiment can be obtained even if the emitter is grounded.As described above, according to the present invention, when displaying halftones, Also, the driving transistor can perform a switching operation, and a heat sink is not required or can be made smaller, which facilitates the heat dissipation design of the transistor. Accordingly, the high frequency deterioration caused by the heat sink and the negative effects of unnecessary radiation are reduced. Furthermore, since heat dissipation measures are simplified, manufacturing costs can also be expected to be reduced.

Furthermore, since the two drive transistors in the present invention (for example, transistors 2 and 8 in FIG. 2) have a type of differential amplifier configuration, the capacitance between the CRT cathode and the control grid is equal and frugal for each transistor. 1/2, which also has the effect of increasing the bandwidth of the circuit.

[Brief explanation of the drawing]

FIG. 1 shows a circuit diagram of a conventional CRT driving circuit, and FIG. 2 shows a circuit diagram of an embodiment of the present invention. 2.8...Drive transistor, 3...Black and white binary signal generation source, 4.Half tone control signal generation source, 5...CRT cathode, 6...CRT control group 1) Rad, 7.C
RT Representative Patent Attorney Michihito Hiraki

Claims (1)

[Claims] (a cathode ray tube; an output terminal connected to the cathode of the cathode ray tube; an input terminal connected to either one of a polar bear binary signal generation source and a halftone control signal generation source; an output terminal connected to the cathode of the cathode ray tube; A drive circuit #f2 is connected to the control grid of the controller, and has an input terminal connected to the other of the black and white binary signal generation source and the halftone control signal generation source, and the first and second drive circuits are A cathode ray tube drive circuit characterized by a switching operation.