JPH0528826Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a high-frequency signal switching circuit that selectively and appropriately switches a plurality of high-frequency signals.

[Prior Art and Its Disadvantages] Generally, this type of high-frequency signal switching circuit is used in video equipment that has recently become popular, such as video tape recorders (VTRs), video disc players (VDPs), and television games. There is a high-frequency signal device that selectively switches the high-frequency output of a television signal along with a television signal received by an antenna, thereby making it possible to reproduce images on a general television receiver.

By the way, conventionally known high-frequency signal switching technologies include (1) a method using a mechanical contact switch, (2) a method using an electromagnetic mechanical contact switch, and (3) a method using a high-frequency diode such as a PIN diode. There are methods using diode switch circuits, etc., which are used as diodes.

However, all of the above methods have the following problems. That is, in the case of method (1), the switching contact mechanism becomes complicated in order to maintain high frequency signal switching performance, making it difficult to obtain something with high durability and reliability.

In the case of method (2), signals are switched using high-frequency relays, and although it has excellent electrical characteristics and durability, it is expensive and poses a problem in terms of price.

Method (3) has excellent features such as excellent electrical performance, economy, and durability, and the ability to switch contacts using electrical signals, but the number of switching contacts (diodes/switches) There has been a problem in that the current consumption, that is, the power consumption of the circuit increases as the number of circuits increases. This will be explained with reference to FIGS. 3 and 4.

FIG. 3 shows the basic circuit of a diode switch. In this circuit, when a positive polarity voltage is applied to the terminal P ₂ and the terminals P ₁ and P ₃ are brought to zero potential, a current flows in the direction shown by arrow A, and the diode D ₁ becomes conductive. terminal
The high frequency signal applied to Q ₁ is sent to terminal Q ₂ through diode D ₁ .

On the other hand, diode D ₂ is in a reverse bias state, so diode D ₂ becomes non-conducting.
It does not affect the high frequency signal path of terminal Q ₁ → connection point a → connection point b → terminal Q ₂ . That is,
The switch is in a state equivalent to being turned on. Next, when a positive polarity voltage V is applied to the terminal P ₃ and P ₁ and P ₂ are reduced to zero potential, the current flows in the direction shown by the broken arrow B, and the diode D ₂ becomes conductive, and the high frequency Point a is short-circuited to ground potential by bypass capacitor C _P. On the other hand, since the diode _D1 is reverse biased, there is no conduction between a and b, and transmission of the high frequency signal from the terminal _Q1 to _Q2 is blocked. In other words, the switch is in a state equivalent to being turned off. Resistors R ₁ and R ₂ limit the current flowing through diodes D ₁ and D ₂ , respectively.
If that current is I _D , the current value is I _D = (V
−V _F )/R.

Here, V _F is the forward voltage of the diodes D ₁ and D ₂ . Further, L ₁ and L ₂ are inductors for blocking high frequency signals, C ₁ and C ₂ are capacitors for blocking DC current, and _CP is a capacitor for bypassing high frequency current.

Considering the high frequency resistance when the diode is conductive, this can be reduced as the forward current increases due to the characteristics of the diode. That is, since the passing loss of the diode switch can be reduced, it is desirable to flow as large a forward current as possible, as long as the allowable loss of the diode, power consumption, etc. allow. Generally, this forward current is 15~
Set to about 20mA.

As explained above, in order to operate the diode switch circuit, it is necessary to constantly flow a current of about 15 to 20 mA regardless of whether it is on or off. Therefore, when a signal switching circuit is constructed by connecting multiple such diode switch circuits (N), the current consumption increases in proportion to the number of diode switch circuits, as shown in Figure 4. It can be seen that (total current consumption I=Id×N). Here, DS1, DS2, . . . indicate diode switch circuits, and Id indicates current consumption per diode switch circuit.

[Purpose of the invention] The present invention was made in view of the above-mentioned circumstances, and its purpose is to provide a high-frequency signal switching circuit that can be realized by combining multiple diode switches without significantly increasing current consumption. It is in.

[Key Points of the Invention] In order to selectively switch multiple high-frequency signals, the present invention connects multiple diode switch circuits with their respective outputs in common, so that only one selected signal is selectively output. In the high frequency signal switching circuit configured as above, the current path of the forward current of the switching diode flowing through each diode switch circuit is always connected in series between each diode switch circuit. It is something.

[Embodiment of the invention] An embodiment of the invention will be described below with reference to the drawings. The high frequency signal switching circuit shown in FIG. 1 is configured to selectively switch high frequency signals inputted from four input terminals IN ₁ , IN ₂ , IN ₃ and IN ₄ using a diode switch circuit. That is, each input terminal IN ₁ , IN ₂ , IN ₃ , IN ₄ is connected to a diode switch circuit 11 ₁ , 11 ₂ , 11 , respectively.
₃ , 11 ₄ are connected. The diode switch circuits 11 ₁ , 11 ₂ , 11 ₃ , 11 ₄ include parallel diode switches D ₁ , D ₂ , D ₃ , D ₄ and series diode switches D ₅ , D ₆ , D ₇ , D _{8 .} and current changeover switches S ₁ , S ₂ , S ₃ , and S ₄ .
The series diode switches D ₅ , D ₆ , D ₇ , D ₈ are
They are provided in series between the signal input terminals IN ₁ , IN ₂ , IN ₃ , IN ₄ and the signal output terminal OUT, and are selected by supplying current to pass high-frequency signals. Parallel diode switches D ₁ , D ₂ , D ₃ , D ₄ are provided in parallel with signal input terminals IN ₁ , IN ₂ , IN ₃ , IN ₄ ,
By supplying current, the high frequency signal is short-circuited to prevent the non-selected signal from being output to the signal output terminal OUT. The current changeover switches S ₁ , S ₂ , S ₃ , and S ₄ are switches having at least two or more interlocking contact circuits, for example, switches with two circuits and two contacts, and the contacts a ₁ and a ₂ of the switch S ₁ are b It is set on the side. Contacts a ₁ and a ₂ of the other switches S ₂ , S ₃ , and S ₄ are set on the c side. These switches S ₁ , S ₂ , S ₃ , and S ₄ are, for example, interlocking push button switches whose contacts are switched by pressing, and are of the double lock prohibition type in which only one switch can be locked. In addition,
L ₁ ~ _{L 8} are inductors for high frequency current blocking, C ₁ ~
C ₈ is a capacitor for blocking direct current, and C ₉ to _{C 13} are capacitors for bypassing high frequency current.

In such a configuration, the first section describes the operation when selecting and outputting the input from input terminal IN ₁ .
This will be explained using figures. When the contacts of switches S ₁ , S ₂ , S ₃ , and S ₄ are positioned as described above, current flows along the path shown by arrow A in the figure. That is, from power supply E, diode D ₄ → inductor
L ₄ →D ₃ →L ₃ →D ₂ →L ₂ →L ₅ →D ₅ →L ₁ to resistor R
flows along the route of As a result, diode _D5 becomes conductive and diode _D1 becomes non-conductive, resulting in the diode switch circuit ₁₁₁ being turned on. In the remaining diode switch circuits 11 ₂ , 11 ₃ , 11 ₄ , diodes D ₂ , D ₃ , D ₄ are conductive, and diodes D ₆ , D ₇ , D _{8 are} conductive.
becomes a reverse bias state and becomes non-conducting, so
All are turned off.

The current flowing through the diode is ultimately supplied to the resistor R and is dissipated as heat. As mentioned above, it is necessary to pass a current of 15 to 20 mA through the diode, so in this example, a current of 15 mA is passed, and Figure 2 shows the consumption for the conventional method and the method of the present invention. Compare power.
The figure compares it with the number of diode switch circuits.

In the figure, since the number of diodes through which current passes is four, the voltage drop at the point of resistor R is 4×(forward voltage of the diode).
For example, if the forward voltage of the diode is 0.7V, the voltage drop will be 2.8V. The power supply voltage E is required to be 10V or more in order to reduce the junction capacitance of the diode in reverse bias. In the case of this embodiment, the power supply voltage is 15V. The total power consumption of the diode switch circuit in this case is 15mA x 15V = 0.225W. Among them, the power consumed by resistor R is (15V - 2.8V) x 15mA
= 0.183W, the remaining 0.02W is the diodes D ₂ , D ₃ ,
This is the power consumption to make _D4 conductive.

On the other hand, in the case of the conventional method, the power consumed by one diode switch circuit is
Since 15mA x 15V = 0.225W, a four diode switch circuit will consume 0.9W of power.

That is, in the case of the conventional method, when the number of diode switch circuits is N, the power consumption thereof is N times the power consumption of one. In contrast, in the case of the present invention, the power consumption of approximately one diode switch circuit is sufficient.

Strictly speaking, there is a voltage drop due to the current flowing through the diode in the forward direction, so if the conditions are the same as in the conventional method, N x (forward voltage of the diode) x
(forward current of the diode), one diode switch circuit requires additional power consumption. In the case of this example, 4×0.7V×15mA=
An extra 0.042W of power is required. Therefore,
Added this 0.042W to the previously calculated 0.225W
The total power consumption in this example is 0.267W.

[Effects of the invention] As described above, the high-frequency signal switching circuit using the diode switch circuit of the invention has an extremely small increase in power consumption when the number of signal switches N increases compared to conventional methods. , power consumption can be significantly reduced. Therefore, it is extremely effective to employ it for devices including a signal selection circuit that is constantly energized, or for downsizing the device by reducing the power supply capacity.

[Brief explanation of the drawing]

Figure 1 is a block diagram of a high frequency signal switching circuit according to an embodiment of the present invention, Figure 2 is a diagram comparing the power consumption of the present invention and the conventional method, and Figure 3 is a conventional diode switch circuit. FIG. 4 is a diagram for explaining the current consumption state of the conventional circuit. 11 ₁ , 11 ₂ , 11 ₃ , 11 ₄ ...Diode
Switch circuit, IN ₁ , IN ₂ , IN ₃ , IN ₄ ... Input terminal, L ₁ to _{L 8} ... Inductor for high frequency current blocking,
C ₁ ~ C ₈ ... Capacitor for DC current blocking, C ₉ ~
C ₁₃ ... Capacitor for high frequency current bypass, E...
…power supply.

Claims (1)

[Claims for Utility Model Registration] In order to selectively switch multiple high frequency signals, multiple diode switch circuits are connected to each other in common so that only one selected signal is selectively output. In the high-frequency signal switching circuit configured as above, the diode switch circuit is a series diode switch that is connected in series between a signal input terminal and a signal output terminal, and is selected by current supply to pass the high-frequency signal. , a parallel diode switch that is provided in parallel with the signal input terminal and short-circuits the high frequency signal by supplying current to prevent non-selected signals from being output;
A current changeover switch equipped with at least two or more interlocking contact circuits for switching the current supplied to the switch and the parallel diode switch, and one contact circuit of the current changeover switch in each of the diode switch circuits is: The parallel diode switches of the unselected diode switch circuit are connected so that current flows in the forward direction and in series, and the other contact circuit of the current selector switch connects the parallel diode switches of the unselected diode switch circuit so that the current flows through the series diode switch when a signal is selected. The current path of the forward current of the series diode switch or the parallel diode switch in the diode switch circuit is connected so that each diode
A high-frequency signal switching circuit characterized in that it is always connected in series between switch circuits.