JPS643410B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a circuit switching circuit that switches the circuit, for example from AM to FM or vice versa, by switching the power supply.

A conventional circuit of this type is shown in FIG. In the figure, 1 is an FM band changeover switch, and 2 is linked to FM band changeover switch 1.
This is an AM band switching switch, and both switches have a common fixed terminal Tc, and first and second switching fixed terminals Ts ₁ provided on both sides of the terminal Tc, respectively.
Ts ₂ and is always in contact with the common fixed terminal Tc,
It consists of a movable contact C that slides in response to a switching operation to short-circuit between the common fixed terminal Tc and the first or second switching fixed terminal Ts ₁ , Ts ₂ . The movable contacts C of the switches 1 and 2 are operated by the FM switching button 1a and the AM switching button 2a, respectively. Each switching button 1
a, 2a are locked in the pushed-in state by pressing the switch button, and the locked state is released by pressing the other switching button.

The common fixed terminals C of switches 1 and 2 are interconnected and connected to the +B power supply, the first switching fixed terminal Ts ₁ of switch 1 is connected to the FM receiver, and the first switching fixed terminal Ts ₁ of switch 2 is connected to the FM receiver. Each is connected to the AM receiving section. And the second of both switches 1 and 2
The switching fixed terminal Ts ₂ is not connected anywhere and is idle.

First switching fixed terminal Ts ₁ of the above switches 1 and 2
is connected to the trigger circuit 3 via an OR circuit consisting of diodes D ₁ and D ₂ . The trigger circuit 3 sends out a mute signal for suppressing pop noise in response to the fall of its input.

In the state shown in FIG. 1, the AM switching button 2a is in the locked state, +B power is supplied to the AM receiver via the common fixed terminal Tc, the movable contact C, and the first switching fixed terminal _Ts1 , and the trigger The input of circuit 3 is held at H level. When the FM switching button 1a is pressed in this state, the AM switching button 2a is released from its locked state and returns to its original position, and the movable contact C of the switch 2 is connected to the first switching fixed terminal. When moving away from Ts ₁ , the power supply to the AM receiver is cut off. Instead, the FM switching button 1a is locked, +B power is supplied to the FM receiver through the switch 1, and the input of the trigger circuit 3 is set to H level.

By the way, if non-shooting type switches are used for switches 1 and 2, before the power supply circuit to the FM receiver via switch 1 is formed, the power supply circuit to the AM receiver via switch 2 is connected to the AM receiver via switch 2. The operation timing can be set so that the power supply circuit of A trigger circuit 3 generates a trigger signal, and this signal can suppress pop noise when switching bands.

By the way, as mentioned above, there is no problem if the switches 1 and 2 are reliably interlocked so that the switching buttons 1a and 2a are locked alternately. However, in devices that perform such switching operations, if the pressing operation force is weak, even if the locked state of the switching button that was previously pressed is released, the newly pressed switching button will not be locked, and the pressing operation will be delayed. When the force is released, both switching buttons 1a and 2a become released, and FM, AM
A state is created in which power is not supplied to both receiving sections. At this time, the input of the trigger circuit 3 falls from the H level to the L level, and can generate a trigger signal in response to this, but when one of the switching buttons is subsequently pressed, the input of the trigger circuit 3 Since the signal only rises from L level to H level, no trigger signal is generated. For this reason, there was a drawback that pop noise could not be blocked.

In addition, in the circuit described above with reference to FIG. 1, due to the influence of the residual charge of the power supply capacitors in each circuit of the AM receiving section and the FM receiving section, the fluctuation of the supplied power to the L level is caused via the diodes _D1 and _D2 . It is difficult to sufficiently detect the falling edge and cause the trigger circuit 3 to generate a mute signal in a timely manner, which is a problem in suppressing pop noise when switching bands.

The present invention was made in order to eliminate the drawbacks of the conventional ones mentioned above, and is usually in the first state,
A plurality of changeover switches are provided, which are switched to a second state by operation and held in that state, and are released from the second state by operation of another switch, and the first switch of one of the plurality of switches is By supplying power to the first and second switched circuits according to the first and second states, and suppressing pop noise at the time of circuit switching by detecting the absence of power supply to both switched circuits. , even if all the transfer switches are in the emergency operation state, 1
The main purpose of this invention is to provide a circuit switching circuit that can suppress pop noise by operating one switch.

The present invention also provides a method in which the switch is further connected so that the power supply voltage rises in the first and second states of another one of the plurality of changeover switches, and the changeover switch is connected in either of the first and second states. We have developed a circuit switching circuit that suppresses pop noise during circuit switching even when it detects that the power supply voltage has not risen, making it unaffected by the residual charge of the power supply capacitor of the switched circuit. It also aims to provide.

Embodiments of the present invention will be described below with reference to FIG. 2, in which parts equivalent to those in FIG. 1 are given the same reference numerals.

In FIG. 2, the first switching fixed terminal Ts ₁ of the switch 1 is connected to the FM receiver and connected to the first trigger circuit 3-1 via the diode D _1-1 .
and an FM indicator circuit 4-1 having a light emitting diode LED ₁ , and the second switching fixed terminal Ts ₂ is connected to the AM receiver and also connected to the trigger circuit 3-1 via the diode D ₂ -1. and an AM indicator circuit 4-2 having a light emitting diode LED ₂ . The first and second switching fixed terminals Ts ₁ and Ts ₂ of switch 2 are diodes.
It is connected to the second trigger circuit 3-2 via D ₂ -2 and D ₂ -1, respectively. Trigger circuit 3-
1 and 3-2 have their outputs interconnected, and when an L level pulse is applied to their inputs, a mute signal is generated at their outputs.

With the above configuration, even when both switching buttons 1a and 2a are unlocked, +B power is supplied to the AM receiving section. Therefore, when the FM switching button 1a is pressed to switch from AM to FM, the movable contact C of the switch 1 connects both fixed terminals.
A state where there is no instantaneous contact is formed at Ts ₁ and Ts ₂ , and
A level pulse is applied to the trigger circuit 3. In response to the falling edge of this pulse, the trigger circuit 3 can generate a mute signal that eliminates pop noise generated at the time of band switching.

Also, during normal band switching operation, switch 2
The movable contact C is the first and second switching fixed contact Ts ₁
The anodes of diodes D _{2 -2} and D ₂ -1 are completely disconnected from the AM and FM receivers, so the power supply for the AM and FM receivers is disconnected. The trigger circuit 3- is not affected by the residual charge of the capacitor.
An L level pulse is now applied to 2.
Therefore, the trigger circuit 3-2 can generate a mute signal that eliminates pop noise generated when switching bands.

Note that in the above embodiments, AM and FM band switching circuits have been described, but the present invention is applicable to AM and FM band switching circuits.
FM, LW 3-band switching circuit, AM, FM,
In addition to the tape mode switching circuit, it can also be used as a transmission/reception circuit switching circuit, and can be configured as a general circuit switching circuit.

As described above, according to the present invention, the plurality of switches are normally in the first state, are operated to take the second state and are held in that state, and are released from the held state by operating another switch. a changeover switch, wherein power is supplied to the first and second switched circuits by the first and second states of one of the plurality of switches, and power is not supplied to both of the switched circuits. The system detects this and suppresses pop noise when switching circuits, so even if all the changeover switches are in the same state, if the power supply is switched by operating from that state, the power supply will be interrupted for a moment. Since a state in which no pop noise is generated is formed, pop noise can be suppressed reliably by detecting this state.

According to another aspect of the present invention, the wires are further connected so that the power supply voltage rises when the other one of the plurality of changeover switches is in the first and second states, and the changeover switch is connected in the first and second states. Since the pop noise at the time of circuit switching is suppressed by detecting that the power supply voltage has not risen, the pop noise is suppressed without being affected by the residual charge of the power supply capacitor of the switched circuit. can also be reliably suppressed.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing a conventional example, and FIG. 2 is a circuit diagram showing an embodiment of the present invention. 1, 2...changeover switch.

Claims (1)

[Scope of Claims] 1. A plurality of changeover switches which are normally in a first state, are switched to a second state by operation and held in that state, and are released from the held state by operation of another switch. , wherein power is supplied to the first and second switched circuits according to the first and second states of one of the plurality of switches, and power is not supplied to both of the switched circuits. A circuit switching circuit is characterized in that it detects this and suppresses pop noise during circuit switching. 2. A switch is provided with a plurality of changeover switches which are normally in a first state, are switched to a second state by operation, are held in that state, and are released from the holding state by the operation of another switch; The first and second states of one of the switches supply power to the first and second switched circuits, and the circuit detects that there is no power supply to both switched circuits. A circuit switching circuit configured to suppress pop noise during switching, further wired so that the power supply voltage rises in the first and second states of another one of the plurality of changeover switches, A circuit switching circuit characterized in that pop noise at the time of circuit switching is suppressed even by detecting that the switching switch is not in either the first or second state and the power supply voltage has not risen. .