JP2818000B2 - Electron gun filament heating device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a filament heating device for an electron gun which can supply a stable and desired current to a filament.

(Prior Art) FIG. 2 shows a filament heating apparatus for supplying a current to a filament of an electron gun and heating the filament.

In the figure, 1 is a reference signal source, 2 is a first differential amplifier, 3 is a DC voltage power supply, 4 is a first transistor, 5 is an isolation transformer, 6 is a rectifier / smoothing device, 7 is a second transistor, and 9 is a low potential. Filament heating current setting device arranged on the side, 10 is an electro-optic converter, 11 is an optical fiber, 12 is a photoelectric converter, 13
Is a second reference signal source, 14 is a second differential amplifier, 15 is a filament, 16 is an extraction electrode, 17 is an acceleration electrode, S is a switching transistor that is turned on / off by a periodic signal, and D is the transformer. A current detector 8 for detecting a current flowing through the primary winding 5 and a rectifying / smoothing device 8 for rectifying and smoothing a detection current from the detector.

In such a filament heating device, since the switching transistor S is turned on and off by a periodic signal, a pulsating flow flows through the primary winding of the tunnel 5 based on the voltage of the DC voltage power supply 3. The current I _C of the pulsating flow is controlled by the base current I _B1 of the first transistor 4 being controlled by a first differential amplifier 2. The current flowing through the primary winding of the transformer 5 is detected by a current detector D, and this detected current is converted into a direct current by a rectifier / smoothing device 8 and sent to the first differential amplifier 2. The first differential amplifier 2
Accordingly, the negative feedback control is performed so that the detection current has a predetermined value corresponding to the output signal of the first reference signal source 1.

By the way, the filament heating current setting device 9 is for setting a current flowing through the filament 15. The filament heating current setting signal from the filament heating current setting device 9 is sent to the second reference signal source 13 via the electro-optical converter 10, the optical fiber 11, and the photoelectric converter 12.
The reference signal generation source 13 generates a voltage signal corresponding to the electric signal from the photoelectric converter 12, and this voltage signal is sent to the second differential amplifier 14. The current from the rectifying / smoothing device 6 is controlled by the second transistor 7 and supplied to the filament 15. At this time, the output current of the second differential amplifier 14 is the base current _IB2 of the second transistor 7, and the current flowing through the filament 15 is a predetermined current corresponding to the signal from the second reference signal source 13. The second differential amplifier 14
Is controlled by negative feedback.

(Problems to be Solved by the Invention) When controlling the current flowing through the filament 15 by the second transistor 7, a portion of the power supplied from the secondary winding of the transformer that is not supplied to the filament is: The second transistor 7 consumes heat. If a large portion is consumed as heat, the temperature rise of the transistor becomes large, and the characteristics of the transistor 7 largely deviate from those expected. As a result, it becomes impossible to accurately supply a desired current to the filament 15.

The present invention is intended to solve such a problem.

(Means for Solving the Problems) For this purpose, the present invention provides a circuit for supplying a current to a primary winding of a transformer, and a current supplied from the circuit to the primary winding to detect the current. A first control circuit for controlling the current to be a predetermined value corresponding to the first reference signal; a filament connected to a secondary winding of a transformer maintained at a high potential; A second control circuit for detecting a current and controlling the detected current to be a predetermined value corresponding to a second reference signal; and a heating current setting for adjusting the value of the second reference signal from a low potential side. A heating device for a filament of an electron gun having a section, wherein a means for changing the value of the first reference signal in conjunction with a signal from the heating current setting section is provided.

(Embodiment) FIG. 1 shows a filament heating apparatus for an electron gun according to an embodiment of the present invention. In the figure, components denoted by the same reference numerals as those in FIG. 2 are the same components.

As shown in FIG. 1, a reference signal generation source 18 is provided instead of the reference signal generation source 1 shown in FIG. The reference signal generation source 18 generates a reference voltage signal based on a signal generated by the filament heating current setting device 9 in conjunction with an output signal of the heating current setting device 9 so that heat consumption in the transistor 7 is always reduced. .

With such a configuration, when the heating current supplied to the filament 15 by the heating current setting device 9 is set to a value smaller than the heating current up to that time, the reference signal generated from the reference signal generation source 18 is also changed to a smaller value. Is done. Therefore, the current supplied to the primary winding of the transformer 5 by the first transistor 4 is further reduced, so that the power transmitted to the transistor 7 via the secondary winding of the transformer 5 is reduced. Therefore, the second transistor 7 operates so as to transmit most of the power transmitted from the rectifier / smoothing device 6 to the filament 15, and the power consumed as heat in the transistor 7 does not increase.

As a result, since the second transistor 7 is not heated as in the conventional case, the transistor 7 operates with predetermined characteristics, and a desired current flows accurately through the filament 15.

(Effect) In the present invention, means for changing the value of the first reference signal in conjunction with the signal from the heating current setting section is provided, and the secondary side is connected to the transformer in accordance with the supply current to the filament. Since power is supplied to the windings, heat generation in the second transistor can always be kept small. As a result, since the second transistor can be used with desired characteristics, a desired current can always be supplied accurately to the filament.

[Brief description of the drawings]

FIG. 1 shows a filament heating circuit of an electron gun showing one embodiment of the present invention, and FIG. 2 shows a filament heating circuit of a conventional electron gun. 1... Reference signal source, 2... First differential amplifier, 3.
DC voltage power supply, 4 ... first transistor, 5 ... insulating transformer, 6,8 ... rectifier / smoother, 7 ... second transistor, 9 ... filament heating current setting device, 10 ... light-to-light converter, 11 …… Optical fiber, 12 …… Photoelectric converter, 13
... Second reference signal generation source, 14: second differential amplifier, 15
... filament, 16 ... extraction electrode, 17 ... acceleration electrode,
18 …… Voltage generator, D: Current detector, S: Switching transistor.

Claims (1)

(57) [Claims] 1. A circuit for supplying a current to a primary winding of a transformer, and detecting a current supplied from the circuit to the primary winding, and detecting the detected current according to a first reference signal. , A filament connected to the secondary winding of the transformer maintained at a high potential, and a current flowing through the filament, and the detected current is detected as a second current. A heating device for a filament of an electron gun, comprising: a second control circuit for controlling a predetermined value according to a reference signal; and a heating current setting unit for adjusting the value of the second reference signal from a low potential side. 2. The filament heating device for an electron gun according to claim 1, further comprising means for changing a value of the first reference signal in conjunction with a signal from the heating current setting unit.