JPH05267902A - Current circuit - Google Patents

Abstract

PURPOSE:To obtain the current circuit which can unify control of current polarity and a current value of a magnetic polarizer of vertical and horizontal polarized waves of a parabolic antenna for a satellite broadcast receiver. CONSTITUTION:A voltage of a current control voltage source 1 and an arbitrary control point within a current control range of a magnetic polarizer 5 are set as a reference voltage and compared by a current polarity switching voltage generator 20, a current polarity switching voltage whose logical value is inverted by setting this reference voltage as a boundary is generated, a current polarity switch 4 is switched by the current polarity switching voltage, polarity of a current for flowing to the magnetic polarizer 5 from a current source 3 is switched, and also, in accordance with the current polarity switching voltage, a control characteristic of the current control voltage source 1 is varied in a control characteristic converter 10, and the current for flowing to the magnetic polarizer 5 from the current source 3 is varied thereby. In such a way, the current control voltage source 1 is enough, and the constitution and the operation are simplified, and can be executed at a low cost.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a current circuit for controlling a magnetic polarizer for satellite broadcasting reception.

[0002]

2. Description of the Related Art FIG. 5 is a block diagram of a conventional current circuit for controlling a magnetic polarizer used in a satellite broadcast receiver. In FIG. 5, 1 is a voltage source for current control and 2 is a current source. A polarity switching voltage source, 3 is a current source, 4 is a current polarity switching device, and 5 is a winding of a magnetic polarizer (hereinafter referred to as a magnetic polarizer). 6 and 7 are explanatory views of FIG.

Next, the operation will be described. Propagation of radio waves of satellite broadcasting may take a form of vertical polarization and horizontal polarization alternately in order to reduce mutual interference between adjacent channels in a satellite receiver. In this case, it is necessary to switch the polarities of the current flowing through the magnetic polarizer 5 at the time of receiving the vertically polarized wave and the horizontally polarized wave, and the polarity is switched by the current polarity switcher 4.

The current polarity switching device 4 is composed of an electromagnetic relay and an electronic switch using a transistor, but the current polarity switching voltage source 2 is indispensable for controlling this.

Further, since the polarization angle between vertical and horizontal has a frequency characteristic and it is necessary to finely adjust between the channels, the current control voltage source 1 for controlling the value of the current flowing to the magnetic polarizer 5 is required. A current source 3 controlled by is provided. Also, a magnetic polarizer 5
Since it is attached to the parabolic antenna, the current source 3 is composed of a constant current source circuit so that weather conditions are severe and it is irrelevant to the temperature change of the polarizer winding impedance.

In FIG. 6, the vertical axis represents the voltage of the current control voltage source 1 when step S for controlling the current value is taken on the horizontal axis. FIG. 7 shows the current of the magnetic polarizer 5 when the logic values of the current polarity switching voltage source 2 are “H” and “L” for step S.

[0007]

A conventional current circuit for controlling a polarizer includes a current polarity switching voltage source 2 for switching the current polarity and a current controlling voltage source 1 for controlling the magnitude of the current value. Need to be supplied independently,
When operating this, there is a problem that the device is complicated, such that a polarity switching operation key and an operation key for changing the magnitude of the current value are required separately.

The present invention has been made in order to solve the above-mentioned problems, and by supplying only the current control voltage source, the required current polarity switching can be performed, and the current polarity switching dedicated operation key is provided. It is an object of the present invention to provide a current circuit that does not require.

[0009]

A current circuit according to the present invention sets a certain threshold within a voltage variable range of a current control voltage source for controlling a current value of a magnetic polarizer, and sets this threshold as a boundary. A current polarity switching voltage generator whose logical value can be inverted and taken out, and a current value control characteristic when the current control switches between positive and negative current polarities with the threshold as a boundary using the output of the current polarity switching voltage generator. And a control characteristic converter for changing the control characteristic so as to be appropriate.

[0010]

The current polarity switching voltage generator according to the present invention compares the voltage of the current control voltage source with the reference voltage, and generates the current polarity switching voltage whose logic value is inverted at the reference voltage.
The current polarity switching voltage switches the polarity of the current flowing through the magnetic polarizer, and the current polarity switching voltage causes the control characteristic converter to change the control characteristic of the current control voltage source, and the current flowing from the current source to the magnetic polarizer. Control the value.

[0011]

EXAMPLES Example 1. An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, reference numeral 20 is a current polarity switching voltage generator, and the current polarity switching voltage generator 20 is composed of a comparator 21, and a reference voltage V _REF is applied to a comparison reference voltage connection terminal 22 of the comparator 21. In addition, the voltage of the current control voltage source 1 is applied to the other input terminal, the comparator 21 compares the two, and a predetermined threshold value is set in the voltage variable range of the current control voltage source 1. Reference voltage V
_REF .

The output of the current polarity switching voltage generator 20 serves as the current polarity switching voltage source 2, and is supplied to the current polarity switching device 4 and the control characteristic converter 10. The control characteristic converter 10 is composed of an inverter 11 and a switch 12. The switch 12 switches the voltage of the current control voltage source 1 and the voltage of the current control voltage source 1 through the inverter 11 to switch the current source 3 to the current source 3. Voltage source 1 for controlling
3 is configured to be changed. The current polarity switch 4 switches the polarity of the current supplied to the magnetic polarizer 5.

Next, the operation will be described with reference to the operation explanatory view of FIG. In FIG. 2A, the vertical axis of the current control voltage source 1 is the voltage of the voltage source whose voltage changes linearly with respect to the control step S. Now, assuming that an arbitrary control point within the control range is S _o , the voltage of the current control voltage source 1 is V _o.
Becomes The current polarity switching voltage generator 20 is composed of a comparator 21, and the reference voltage connection terminal 22 has V _REF = V
_o Reference voltage is applied.

[0014] The comparator 21 the input voltage V _IN <When V _REF, the output is "H", V _IN> when the V _REF if those composed such that the output is "L", Figure 2
As shown in (b), it becomes possible to generate a voltage of the current polarity switching voltage source 2 which changes to H / L with the control point S _o as a boundary.

The inverter 11 operates so as to invert the voltage control characteristic of the current control voltage source 1 shown in FIG. 2A, and a characteristic having a negative slope with respect to the control step is obtained. Switch 12 by the voltage of the current polarity switching voltage source 2, and that through the inverter 11, which does not pass is switched, as indicated by the solid line in FIG. 2 (c), the control point S _o
An output with varying control characteristics can be obtained at the boundary of.

As a result, as shown in FIG. 2D, the current flowing through the magnetic polarizer 5 has its current polarity reversed at the boundary of the control point S _o, and the control characteristic (13) shown in FIG. The change of the current value can be obtained depending on the voltage).

Embodiment 2. Although the control characteristic converter 10 is composed of the inverter 11 and the switch 12 in the above embodiment, it may be composed of an adder as shown in FIG. 3 is the same as the control characteristic converter 10 shown in FIG. 1 except for the difference. FIG. 4 is an explanatory diagram of FIG. 3, but because the conversion characteristics of the control characteristic converter 10 of FIG. 1 and FIG. 3 are different, the voltage of the voltage source 13 of FIG.
The change characteristic of the current 50 of the magnetic polarizer 5 shown in (d) is different from that in FIG.

In FIG. 3, the control characteristic converter 10 is composed of an adder, and the output of the current polarity switching voltage generator 20 (the voltage of the current polarity switching voltage source 2) and the current control voltage source 1 are used.
4C, the current control characteristic changes like a sawtooth wave with the control point S _o as a boundary, and correspondingly, the voltage source 13 shown in FIG. A current change characteristic as shown by the current 50 of the tic polarizer 5 is obtained. The difference between FIG. 1 and FIG. 3 is that the slope of the change of the current value is opposite in the negative current region with respect to the direction of step S, and substantially the same effect is obtained.

[0019]

As described above, according to the present invention, the current polarity switching voltage generator compares the voltage of the current control voltage source with an arbitrary control point within the current control range of the magnetic polarizer as a reference voltage. Then, a current polarity switching voltage whose logic is inverted is generated, and the polarity switching device is switched by this current polarity switching voltage to switch the polarity of the current supplied from the current source to the magnetic polarizer. Since the control characteristic converter is used to change the control characteristic of the current control voltage source to control the current source, only the current control voltage source is prepared without preparing the switching voltage for switching the current polarity. Only the control signal generator, for example, the hardware and software of the microcomputer can be simplified, and the operation itself is also possible. Whole simply becomes device is obtained an effect that less expensive.

[Brief description of drawings]

FIG. 1 is a block diagram of a current circuit according to an embodiment of the present invention.

FIG. 2 is a diagram for explaining the operation of the above embodiment.

FIG. 3 is a block diagram of a current circuit according to another embodiment of the present invention.

FIG. 4 is an operation explanatory diagram of the embodiment of FIG.

FIG. 5 is a block diagram of a conventional current circuit.

6 is a characteristic diagram showing the relationship between the current value of the magnetic polarizer and the voltage of the voltage source for current control in order to explain the operation of the current circuit of FIG.

7 is a characteristic diagram showing the relationship between the currents of the magnetic polarizer at the logic values H and L of the current polarity switching voltage source for explaining the operation of the current circuit of FIG.

[Explanation of symbols]

 1 voltage source for current control 2 current polarity switching voltage source 3 current source 4 current polarity switching device 5 magnetic polarizer 10 control characteristic converter 11 inverter 12 switch 20 current polarity switching voltage generator 21 comparator

Claims (1)

[Claims] 1. A current source for supplying a current to a magnetic polarizer and a current for generating a current polarity switching voltage whose logic value is inverted at a boundary between an arbitrary control point within the control range of the current flowing through the magnetic polarizer. A polarity switching voltage generator, a current polarity switching device that switches the polarity of the current supplied from the current source to the magnetic polarizer by the current polarity switching voltage, and a control characteristic of the control voltage source by the current polarity switching voltage. And a control characteristic converter for changing the current value of the current source.