JPS6237716A - Constant current control 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 [Field of Application of the Invention] The present invention relates to a constant current control circuit, and particularly to the configuration of a phase-controlled power supply suitable for use in heating a deposition source of a deposition apparatus.

[Background of the invention]

FIG. 3 is a circuit diagram showing an example of a conventional AC constant current power supply. In the figure, a phase controlled power source 1 is shown.

A power transformer 2 that inputs an AC power supply AC, converts it to a predetermined output voltage, and outputs it, a phase control element 3 that is connected in series to the primary winding of this power transformer 20 and controls the phase of the input voltage, and this phase control control cable. and a phase control circuit 4 which supplies a gate signal vG corresponding to a control input voltage v[good] to the child 3.

In such a configuration, a control input voltage vI as shown in FIGS. 4(a) and 4(b) is applied to the phase control circuit 4 from the outside.
When N is input, the firing phase θ is changed as shown in the same figure (C).
is converted into a gate signal VG with a changed value, and is supplied to the phase control element 3. Then, the output voltage whose phase has been controlled by the phase control element 3 is converted into a voltage by the power transformer 2, and an output voltage votr'r as shown in FIG. 3(d) is output. This output' voltage VOUT is, for example, a load 6 such as a heater for heating the vapor deposition source of the image pickup tube target vapor deposition apparatus main body 5.
was applied and was.

On the other hand, this load 6 is a screw 7A each time the vapor deposition work is performed.

It is connected to the vapor deposition apparatus main body 5 by screws 7B. Part 1.
Since the contact area of this threaded portion is small, the contact resistance fluctuates each time a vapor deposition operation is performed. As a result, in evaporation equipment that requires low voltage and large current output, fluctuations in contact resistance lead to fluctuations in output current, which in turn causes problems such as fluctuations in the heating time of the load 6 and insufficient heating. cause

In the initial stage after the output voltage vOUT is applied, the resistance value is small because the load 6 is cold, and an inrush current I'OUT flows as shown in FIG. For this reason.

The load 6 may be heated rapidly and the material of the vapor deposition source may be scattered.

Examples of one-phase control technology include the constant voltage DC power supply introduced on page 157 of the NEC Thyristor and Rectifier Handbook 1978, or the constant voltage piezo current power supply introduced on page 160 of the circular. However, these are based on nine systems that convert the output voltage to DC and perform feedback control, and there are no AC constant current types. In addition, this method of rectifying direct current requires a rectifying and smoothing circuit, which increases the size of the power supply and the power consumption, and requires a conversion circuit, which inevitably leads to low efficiency. The problem is that it becomes a problem.

[Purpose of the invention]

The present invention has been made in view of the above-mentioned problems, and its object is to provide a constant current control circuit which is inexpensive and made into a cylinder.

[Summary of the invention]

Normally, when a feedback control circuit is used as a phase control means, the voltage of the detection part is converted to DC or the DC voltage is detected, and the value is compared with a reference value for control. In the case of direct current, it can be controlled at any time, so
This can be done easily, but in the case of AC, the voltage waveform of the output voltage '10UT is cut off in the middle as shown in Figure 6(a), so
Inevitably, the first step is feedback control with a half-cycle delay. Furthermore, as shown in the figure (b), *Mflf, the voltage V, is integrated into DC to obtain the integrated voltage v2 as shown in the figure (c) IC, which stabilizes the specific output voltage Vs k.To detect the specific output voltage Vs k There is also a time delay of several cycles. These time delays adversely affect the response speed q9.

To prevent this time delay during integration, integrate one pulse at a time,
It is sufficient to obtain a hold voltage V4 that holds the value as shown in FIG. 2(d). This enables an AC constant current power supply with a fast response speed.

[Embodiments of the invention]

Next, embodiments of the present invention will be described in detail using the drawings.

FIG. 1 is a circuit diagram showing an embodiment of a constant current control circuit according to the present invention, and the same parts as those in the previous figure are given the same reference numerals. In the figure, 8 is a current detector connected in series to the secondary winding of the power transformer 20.

9 is an effective value conversion circuit, and 10 is a comparison circuit.

In FIG. 2, (a) to (e) show voltages and current waveforms at various parts of FIG. 1.

In such a configuration, if the resistance value of the load 6 of the vapor deposition apparatus main body 5 changes as shown in FIG. 2(a) at the initial stage of heating, the output current will be rov'r will decrease. In order to compensate for this, it is necessary to increase the firing phase θ of the output voltage VOUT.

Therefore, in this embodiment, the current detector 8 is used.

The output current roar (IE2 diagram (C)) is detected, and this output current l0UT f! r: The effective value conversion circuit 9 integrates and holds the DC voltage Viθ (Fig. 2 (dN), and this DC voltage Viθ and the constant current reference voltage Vii (Fig. 2 (d) )), the phase control voltage VIN (FIG. 2(e)) is corrected, and constant current control 4 is performed.

According to such a configuration, the effective value conversion circuit 9 can be configured using an effective value detection IC.

Since integral hold (effective value) is possible, an alternating current constant current circuit with one-phase control is possible.90 Also, since constant current control is possible, stable evaporation work of the image pickup tube target has become possible.

〔Effect of the invention〕

As explained above, according to the present invention, by providing a load current detector, an effective value conversion circuit, and a comparison circuit,
Since constant current control using AC is possible, compared to other power sources such as DC constant current power supplies, there are fewer components, the weight and volume are smaller, and the efficiency of the power supply can also be improved. Extremely excellent effects can be obtained.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing an embodiment of the constant current control circuit according to the present invention, Fig. 2 G) to (e) are time sequences of phase control of each part shown in Fig. 1, and Fig. 3 is a conventional phase control circuit. Circuit diagram of the control circuit, Figures 4(a) to (d) are time sequences of phase control of each part shown in Figure 3, Figure 5 is a diagram showing current changes of the constant voltage power supply, and Figure 6 is phase control. In the time sequence of fzle. 1... Phase control power supply, 2... Power transformer, 3
... Phase control element, 4... Phase control circuit, 5.
...Vapour-deposited monk body, 6...Load, 7A, 7B...
...screw, 8...' peeping current detector, 9... effective direct conversion circuit, 10... agent Masaru Ogawa, patent attorney
Male Figure 5 Time Opening (1) Figure 6

Claims (1)

[Claims] a power transformer that converts an alternating current voltage into a predetermined voltage; a phase control element that controls the phase of the input voltage of the power transformer; a load current detector that detects a load current of the power transformer; a comparator circuit that compares the DC voltage with a constant current reference voltage and outputs a phase control voltage, and controls a gate signal of the phase control element using the phase control voltage. A constant current control circuit comprising a phase control circuit.