JPH047979A - Part constant switching circuit - Google Patents

Abstract

PURPOSE:To obtain the compact and low-priced constant switching circuit by switching a circuit constant while controlling the ON/OFF of an FET element. CONSTITUTION:In a horizontal deflecting circuit, capacity as the circuit constant for S-shaped correction is switched corresponding to the kind of a video signal to a set by controlling the parallel connection/disconnection of a capacitor CS2 to a capacitor CS1 while turning on/off an FET 6. First of all, in turning on the FET 6, a transistor Q2 is turned off and a capacitor C2 is charged. By operating the deflecting circuit, a pulse voltage is loaded through the capacitor C2 to the gate of the FET 6 and a charging current, however, flows during a period, when the pulse voltage is not loaded, so as to charge the capacitor C2. Thus, the FET 6 continues the ON state. In turning off the FET 6, the transistor Q2 is turned on. Thus, the capacitor C2 is discharged, a gate voltage is turned to zero and the FET 6 is turned to the OFF state.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a component constant switching circuit for switching circuit constants in response to switching of functions of a device.

[Summary of the Invention] The present invention uses a FET element in place of a conventional relay as a switch means for switching component constants in a component constant switching circuit for switching circuit constants, and uses the FET element on the control side of the FET element due to its high input impedance. In addition, the influence on the switching state of the FET due to electrical coupling between the circuit constant side and the control side is eliminated by the charging voltage of the capacitor connected to the gate electrode. By doing this, the switch means can be realized in a small size and at low cost, and
This improves the degree of freedom in arrangement.

[Prior Art] Conventionally, in various devices, circuit constants have been switched in response to switching of functions. A conventional example of this will be explained using a horizontal deflection circuit of a multi-deflection monitor television receiver shown in FIG. In a multi-polarization monitor television receiver (hereinafter referred to as a set), the input source of the video signal is General Television, i! There are a wide variety of devices such as slave computers, navigation systems, and other devices, and each signal has a different horizontal deflection frequency, and in order to display those images on the same screen, it is necessary to make the horizontal deflection frequency variable. is needed. In the configuration of the horizontal deflection circuit shown in FIG.
l is a cathode ray tube (hereinafter referred to as CRT), 2 is a deflection yoke for horizontal deflection, 3 is a flyback transformer for high voltage generation, E is a DC power supply, C1 is a capacitor for resonance, Q
, is a transistor that performs switching to flow a sawtooth deflection current, D is a damper diode, 4 is an oscillator (O20) that drives the transistor Q and determines the horizontal deflection frequency according to the type of input video signal, Cs, Cst
is a capacitor for figure 8 correction, L+ is a variable inductance element for linearity correction, 5a is a relay contact for varying the constant of the capacitor for figure 8 correction, and 5 opens and closes the contact 5a depending on the type of input video signal. It is a relay circuit. The flyback transformer 3 has one end on the negative side connected to the power supply E0, and the other end connected to the transistor Q, and generates a high voltage on the secondary side from the switching 1 of the transistor Q, and the diode Dx.

A DC high voltage is applied to the CRT I through D3.

In the resonant circuit of the deflection circuit, one end of the deflection yoke 2 is connected to the ground through the resonance capacitor C1, and the other end is connected to the ground through the series-connected figure-8 correction capacitor CSR and the variable inductance element L1.
The capacitor Csx with respect to the capacitor Cs+ is controlled to be connected or disconnected in parallel by opening and closing a relay contact 5a. With this, for example, when the human input video signal is switched and the deflection frequency is switched high, the capacitor Cst
Switching is performed such as disconnecting the circuit and reducing the capacitance, which is a circuit constant for character-8 correction.

[Problems to be Solved by the Invention] However, in switching the circuit constants of the deflection circuit in the above-mentioned conventional technology, the relay control circuit side and the resonant circuit side of the deflection circuit are electrically isolated, so they do not affect each other. However, the relay is large in size, requires a large control power, has limited placement, and is expensive. Therefore, when considering the use of a semiconductor element, a problem arises in that a pulse voltage on the deflection circuit side is generated on the control side of the semiconductor element, making it impossible to perform normal switching.

The present invention was created to solve the above-mentioned drawbacks and problems, and provides a component constant switching circuit that is small, can be freely arranged, and can be constructed at low cost by using semiconductor elements without using relays. The purpose is to

[Unusual Means for Solving the Problems] The configuration of the component constant switching circuit of the present invention to achieve the above object is as follows: A field effect transistor element is inserted by connecting a drain electrode and a source electrode at the location where the component constants are to be switched. A capacitor is connected between either the drain electrode or the source electrode of the field effect transistor element and the gate electrode, and charging means and discharging means are connected to the capacitor to charge and discharge the field effect transistor. It is characterized by controlling the on/off of.

[Function] The present invention uses a field effect transistor element instead of a conventional relay contact as a means for switching component constants.
It is inserted at the switching point on the circuit constant side, and its high input impedance separates the control side of the field effect transistor from the circuit constant side, eliminating the influence of the circuit constant side from the control side, and allowing the field effect transistor to switch from the circuit constant side. By eliminating the influence on one switching state by the holding voltage by charging the capacitor connected to the gate electrode, and by discharging the capacitor to transition to the other switching state, the circuit constant can be reduced by the semiconductor element.
allows for replacement.

[Embodiment 1] Hereinafter, embodiments of the present invention will be described in detail based on the drawings.

FIG. 1 is a circuit diagram showing a first embodiment of the present invention. This embodiment is an example in which the constant of the S-shaped correction capacitor of the conventional horizontal deflection circuit shown in FIG. shall be. In the configuration of this embodiment, 1 is a cathode ray tube (hereinafter referred to as CRT), 2 is a deflection yoke for horizontal deflection, 3 is a flyback transformer for high voltage generation, Ea is a DC power supply, and C3 is a capacitor for resonance. ,
Q is a transistor that performs switching to flow a sawtooth deflection current, DI is a damper diode, 4 is an oscillator (O20) that drives the transistor Q and determines the horizontal deflection frequency according to the type of input video signal, Cs+, C
s2 is a capacitor for S-shape correction, a variable inductance element for Ll beam linearity correction, 6 is an FET for varying the constant of the capacitor for S-shape correction, and 7 is a FET 6 for changing the constant of the capacitor for S-shape correction. This is the FET drive circuit that controls the Flynoku Tsukutrance 3 is
-One end of the next side is power supply E. , and the other end is connected to transistor Q1, which generates a high voltage on the secondary side by switching of transistor Q, and diode D! , D3
A high DC voltage is applied to CI (T I) through 7. In the resonant circuit of the deflection circuit, one end of the deflection yoke 2 is connected to the ground through the resonance capacitor C1, and the other end is connected to the serially connected S-shaped correction capacitor C1. The capacitor Cs + of the capacitor Cs + is connected to the ground through the variable inductance element 5, and one end of the capacitor Cs t is connected to the terminal of the capacitor Cs + on the deflection yoke 2 side, and the other end of the capacitor Csv is connected to the terminal of the FET 6. The variable inductance of the capacitor Cs1 is connected through the FET 6 and the source electrode.A diode D4 may be connected in the reverse direction between the drain and source electrodes of the FET6.

Next, the configuration of the FET drive circuit 7 will be explained. Here, the FET 6 is assumed to be an n-channel type. In the drive circuit of this embodiment, a capacitor C2 is connected between the gate electrode and the source electrode of the FET 6, and a resistor R1 is connected in parallel with the capacitor C2.

This resistor R8 is a means for discharging the capacitor C7. DC power supply E resistance R6, transistor Q2. Diode D5
The circuit consisting of is a charging means for the capacitor C7.

In this charging means, the + side of the power source E is connected to the gate electrode side of the capacitor C1 through the forward diode D through the resistor R2, the collector of the transistor Q is connected to the anode side of the diode D5, and the collector of the transistor Q is connected to the anode side of the diode D5. , and an example of the power supply EI are connected to ground.

The operation and effects of the first embodiment configured as above will be described.

In this embodiment, by turning on/off FET6,
By controlling the parallel connection/disconnection of the capacitor Cst to the capacitor Cs, the capacitance, which is a circuit constant for S-shaped correction, is switched depending on the type of video signal input to the set. First, when controlling the FET 6 to turn on, the transistor Q is turned on, and the capacitor C is charged through the power supply E → resistor R7 → diode D5 → capacitor C2 → variable inductance L. Due to the operation of the deflection circuit, a pulse voltage is applied to the gate electrode of FET6 via resistor R+ and capacitor C7.
The charging current is a pulse voltage and flows for an unprecedented period to charge the capacitor C7. Capacitor C
When FET 7 is charged, the terminal voltage of capacitor C2 is held even during the period when the above-mentioned pulse voltage is applied, and the FET 6 can continue to be in the on state with this holding voltage. Next, when controlling FET6 to turn off, transistor Q
, turn on. As a result, the charging current stops flowing, and the capacitor C1 is discharged after a certain period of time by the resistor R, and the gate voltage becomes zero volts, and the capacitor C1 is turned off. The current that attempts to flow from the deflection circuit side to the PET drive circuit 7 side is blocked by the high input impedance of the gate electrode and the gate electrode D.
It will not be affected. This makes it possible to perform the same operation as switching component constants using a relay.

FIG. 2 is a circuit diagram showing a second embodiment of the invention.

This embodiment shows an example of switching six circuit constants in a screen distortion correction circuit of a deflection circuit of a multi-deflection monitor television receiver. Reference numeral 2 denotes a deflection yoke, and Ql is a transistor that performs switching to flow a deflection current having a deflection frequency corresponding to an input video signal to the set, as described above. The screen distortion correction circuit consists of diodes D, D? connected in series in the opposite direction between the collector of this transistor Q and the ground. , and capacitors C3 and C, which are also connected in series, are connected, and their midpoints are connected, and capacitor C6 is connected in parallel to capacitor C3 through FET6, and capacitor C6 is connected in parallel to capacitor C4 through FET8. It consists of FET
6 is constructed in the same way as the circuit constant switching means shown in the first embodiment, and a capacitor C is connected between the gate and source electrodes.
3 is connected, a discharging resistor R1 is connected in parallel to it, and a charging diode D is connected to the gate electrode.

are connected. The FET 8 is also used to switch circuit constants by turning it on and off, but since it is connected to the ground side, it is sufficient to simply apply a control voltage to its gate electrode.

The FET 6 in this second embodiment operates in exactly the same way as the first embodiment, except that the purpose is different, and the diode D
The charging voltage caused by the charging current from , is maintained and controlled to be on even during the period when the pulse voltage of the deflection circuit is applied to the gate electrode of the FET6, and the capacitor C6 is connected in parallel to the capacitor C8. Furthermore, by cutting off the charging current from the diode D, the charging voltage of the capacitor C7 is discharged and the gate voltage becomes zero volts, the FET 6 is controlled to be turned off, and the capacitor C6 is separated from the capacitor C3. Thereby, circuit constants for screen distortion correction can be switched.

FIG. 3 is a circuit diagram showing a third embodiment of the present invention.

This embodiment shows another embodiment of the FET drive circuit 7 of the first embodiment. FET 6 , capacitor C1, resistor R1, and variable inductance element Ll are the same as in the first embodiment, are connected in the same way, and function in the same way. In this embodiment, the charging means for the capacitor Ct that controls the ON state of the FET 6 is different. That is, the charging means of this embodiment controls a pn transistor Q whose emitter is connected to a DC power source E and whose collector is connected to the gate electrode of the FET 6 to flow a charging current. transistor Q,
is a npn) transistor Q whose base passes through a resistor R3.
is connected to ground through the collector emitter of ,
A resistor R6 is connected between the base and emitter. Transistor Q by controlling this transistor Q4 to turn on.

Charging current can be passed through the switch, and the charging current can be cut off by turning it off.

FIG. 4 is a circuit diagram showing a fourth embodiment of the present invention.

This embodiment shows yet another embodiment of the FET drive circuit 7 of the first embodiment. FET6 Capacitor C1 DC power supply E2. Resistance Rt.

Diode D6. Transistor Q2. The variable inductance element is the same as in the first embodiment, connected in the same way, and functions in the same way. This embodiment differs from the first embodiment in the discharging means for the capacitor C2 that controls the FET 6 to turn off. That is, the discharge means of this embodiment connects the emitter of the pnp transistor Q to the gate electrode side of one end of the capacitor C2, connects its collector to the other end of the capacitor C2, and connects its base to the transistor Q through the resistor R5. and the cathode of a diode D through a resistor R8. The structure of the charging means is the same as that of the first embodiment, and the transistor Q
, a charging current flows to capacitor C7 and transistor Q.

is turned off, and FET6 is controlled to be turned on. Furthermore, by turning on the transistor Q, the charging current is cut, and the transistor Q is also turned on, and the charging voltage of the capacitor C3 is discharged to zero volts, and F
ET6 is controlled to be off. In the above embodiment, an example was shown in which the capacitance (C) of the capacitor was changed as a component constant, but when changing the resistance value (R) or inductance (L), It goes without saying that the present invention can also be applied to the case where these composite elements (L, C, R) are switched. Furthermore, it goes without saying that the present invention can also be applied to other than deflection circuits. It is clear that a p-channel type can also be used as the FET element of the present invention. As described above, the present invention can be applied in various ways and can take various embodiments in accordance with its gist.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram showing a first embodiment of the invention, Fig. 2 is a circuit diagram showing a second embodiment of the invention, and Fig. 3 is a circuit diagram showing a third embodiment of the invention. , FIG. 4 is a circuit diagram showing a fourth embodiment of the present invention, and FIG. 5 is a circuit diagram showing a conventional example. 6...FET, 7...PET drive circuit, Cs+, Cs
. 8-character correction capacitor, C2, which constitutes the circuit constants
Capacitor, R1...resistance for discharging, D5...guioto for charging. [Effects of the Invention] As is clear from the above explanation, according to the component constant switching circuit of the present invention, circuit constants can be switched using FET elements instead of relays, so circuit constants can be switched in a small and inexpensive manner. This can be realized, and the degree of freedom in arranging components and FET elements can be increased. t2's actual scale j and Bo 1st grand drawing 2nd picture 54 shows the backside Kisii 9 bow 1
Figure A shows the ``logo (d)

Claims (1)

[Claims] (1) Insert a field effect transistor element by connecting the drain electrode and source electrode at the point where the component constants are changed, and place a capacitor between either the drain electrode or the source electrode of the field effect transistor element and the gate electrode. A component constant switching circuit characterized in that: a charging means and a discharging means are connected to the capacitor, and the on/off of the field effect transistor is controlled by charging and discharging the capacitor.