JPH0339956Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to an AM/FM band selection device that can select the AM/FM band using an electronic switch in a variable capacitor tuning tuner.
Impact noise (pop noise) that occurs especially when the power is turned off or when selecting the AM/FM band.
Equipped with an electronic mutating function that allows the removal of
This invention relates to an AM/FM band selection device.

(Prior Art) Conventionally, the output signals of the AM receiving section 31 and the FM receiving section 32 shown in FIG. It was outputting. That is, A.M.
In order to selectively supply power to either the receiving section 31 or the FM receiving section 32, switches SW ₁ and SW are connected to the two input terminals of a flip-flop 37 configured by NAND gates G ₁ and G ₂ , respectively. You can now select by ₂ . Therefore, the power supply
Upon initial application of B ⁺ , capacitor _C1 gradually powers up
B ⁺ voltage is charged, but before the charging voltage reaches the operating voltage V _TH of the inverter I ₁ during the charging process, the outputs of the two inverters I ₁ and I ₂ are each “HIGH”. ” and “LOW”. Therefore, one NAND gate _G2 in the flip-flop 37 has a “low” state.
However, "high" is input to the other NAND gate _G1 . For this reason, NAND gate G ₁ ,
The outputs of G ₂ will be "low" and "high" respectively. Its "high" makes transistor _Q5 conductive. This makes the Zener diode ZD ₂
and transistor _Q6 is turned off. Furthermore, the transistor _Q3 is turned off due to the above-mentioned "low" state.
This causes the Zener diode ZD ₁ and the transistor Q ₄ to conduct. This makes the power supply B ⁺
Connect to the FM receiving section 32. In this way, the FM receiving section 32 is selected when the initial power is applied. At the same time, since the output of NAND gate G ₂ is "high", transistor Q ₂ is turned on. This lights up the light emitting diode LD ₂ .
Displays that the FM receiving section 32 is in operation.

Also, the high potential signal from the inverter I ₁ is applied through the diode D ₅ , so the transistor
Q ₉ and Q ₁₀ conduct. As a result, the analog switches 33 to 36 are turned off, and the shock voltage is applied to the AM receiver 31 and the FM receiver at the initial stage of the power supply B ⁺ input.
The impact noise is prevented from being applied to the receiving section 32, and the impact noise is removed.

After such initial operation, charging of capacitor C ₁ is completed. As a result, the outputs of inverters I ₁ and I ₂ become "low" and "high", respectively. This causes the input of NAND gate _G2 to become "high". And the input of NAND gate _G1 is also “high”
Therefore, the outputs of NAND gates G ₁ and G ₂ will maintain their previous states. and,
Since the output of the inverter _I1 has become "low", the "low" is applied to the bases of the transistors _Q7 and _Q10 through the diode _D5 . This turns off both transistors Q ₇ and Q ₁₀ . Since the output of the NAND gate _G2 is at a high potential, the output of the FM receiver 32 is outputted through the analog switches 35 and 36 after being delayed by the charging time of the capacitor _C1 .

In this state, when switch SW ₁ is pressed to switch the AM/FM band, the output state of the flip-flop 37 is inverted. That is, NAND
The outputs of gates G ₁ and G ₂ are "high" and "low", respectively. Its "high" makes transistor Q ₃ conductive at the moment of state change, turning off transistor Q ₄ and the FM receiver 32 . Furthermore, since the transistor _Q7 is turned on by the above-mentioned "high", the output of the inverter _I3 becomes "high". The "high" level of inverter _I3 causes transistors _Q9 and _Q10 to conduct. Due to this conduction, the voltage applied to the control terminals of analog switches 33-36 becomes low, turning off those switches 33-36. By turning it off, impact noise at the time of band switching is removed. Furthermore, when the power is cut off, the charging voltage of the capacitor _C1 is discharged. Then, when the voltage of the capacitor C ₁ is discharged to below the operating voltage V _th , the outputs of the inverters I ₁ and I ₂ become “high” and “low”, respectively. Due to its “low”
Both NAND gate G ₁ and G ₂ outputs become “low”. The "high" outputs of these gates G ₁ and G ₂ turn off the analog switch in the same way as described above. This eliminates impact noise.

(Problems to be Solved by the Invention) Such conventional devices are each provided with switches SW ₁ and SW ₂ for selecting AM or FM. In other words, two switches for the required band must be provided. Therefore, not only does it take up space, but when the band switches SW ₁ and SW ₂ are pressed at the same time, the outputs of the NAND gates G ₁ and G ₂ both go to the "high" state, and the AM and FM bands are selected at the same time. The constant voltage supply section that is not selected will continue to consume power, and by using the output end of the PosiTep side detector as an inverter, power B ⁺ is continuously supplied to the inverter. There are various disadvantages such as unnecessary power consumption and, in particular, the need to drive the AM and FM selection display sections with separate drive circuits.

The present invention was made to solve these conventional drawbacks, and allows AM, AM, and
AM/FM band selection that allows you to select the FM band, eliminates noise that occurs when power supply is cut off and selects the AM/FM band, and minimizes unnecessary power consumption. The purpose is to provide equipment.

An embodiment of the present invention will be described with reference to FIG.
In the device of the embodiment, AM receiving section 1 and
The respective output signals of the FM receiver 2 are sent to _{the output terminals L, G 2 and} G ₃ , G ₄ through analog switches
I am trying to output it to R. Additionally, power supply B ⁺
, Zener diode ZD ₁ and transistor Q ₁
The transistors Q ₂ ,
The signal is supplied to the transistors Q _{2 and} Q ₃ of the switching section 8 having Q ₃ and Zener diodes ZD 2 and ZD ₃ . The two output terminals of the switching section 8 are connected to AM through the two display sections 4 and 5 having light emitting diodes LD ₁ and LD ₂ , respectively.
It is connected to the power terminals of the receiving section 1 and the FM receiving section 2, respectively. Furthermore, the bases of the two transistors Q ₂ and Q ₃ of the switching section 8 are connected to 2
_{The two} output terminals Q,
are connected to each. The two output terminals Q, of the flip-flop 7 are connected to the control terminals of the analog switches G ₃ , G ₄ and G ₁ , G ₂ respectively, and the transistors Q ₄ , Q ₅ , the diodes D ₁ ,
It is connected through capacitors C _{3 and} C ₄ to the respective bases of the transistors Q ₄ and Q ₅ of the pulse positive polarity component detection section 6 having D 2 and capacitors C ₃ and C ₄ . The two output terminals of the pulse positive polarity component detection section 6 are connected to the positive terminal of a grounded capacitor _C5 , and are also connected to the bases of grounded emitter transistors _Q6 and _Q7 through an inverter _I1 . The collectors of these transistors Q ₆ and Q ₇ are connected to the two output terminals Q of the flip-flop 7, respectively. The clock input terminal CK of the flip-flop 7 is connected to the mover contact c of the switch SW ₁ , the fixed contact a is grounded, and the fixed contact b is connected to the input terminal T of the flip-flop 7.

Next, the operation and effects of the above device will be explained with reference to FIGS. When the power source B ⁺ is supplied at an arbitrary time t ₁ as shown in Fig. 2,
Power supply B ⁺ is supplied to the reset terminal of flip-flop 7 through resistor _R1 . Also, through the resistor R ₂ , the capacitor
It is applied to the input terminal T and preset input terminal P of the flip-flop 7 while being gradually charged by _C1 . Furthermore, capacitor C ₅ is gradually charged through resistor R ₁₀ as shown in Figure 2.
Applied to the input side of inverter _I1 . Therefore, during the period _t1 to _t3 when the charging voltage of the capacitor _C1 is lower than the operating voltage _VTH , the flip-flop 7 is connected to the input terminal T because the preset is at a low potential, as shown in FIG. Regardless of the input signal to the clock terminal CK and the input signal to the clock terminal CK, as shown in Figure 2,
The output terminal Q of the flip-flop 7 is in an H level state (high potential state), and the output terminal maintains an L level state (low potential state). This allows the power
When B ⁺ is applied, analog switches G ₃ and G ₄
The FM band is selected by turning on. Then, a high potential signal is output as shown in FIG. 2 for a certain period of time t ₁ to _{t 4} during which the voltage charged in the capacitor C ₅ is lower than the operating voltage V _TH of the inverter I ₁ . In this case, the delay time of the flip-flop 7 is ignored as shown in FIG. 2 because it is extremely small compared to the time constant due to the resistor and capacitor. The high potential signal from the inverter I ₁ passes through the diode D ₃ and through the resistors R ₁₁ and R ₁₂ to conduct the transistors Q ₆ and Q ₇ , respectively. This allows analog switches G ₁ to _{G 4}
A low potential signal is supplied to control input terminals g ₁ to g ₄ of. This turns off all analog switches G ₁ to _{G 4} and removes the output noise when the power supply B ⁺ is initially applied. In addition, since the output terminal Q of the flip-flop 7 is in a high potential state, the transistor _Q5 of the pulse positive polarity component detection section 6 has its operating voltage V _TH as shown in FIG.
It is on for a certain period of time t ₁ to _{t 2} . As a result, the collector, which is the output of the transistor _Q5 , is in a low potential state for a certain period of time _t1 to _t2 . Then, when the initial power is applied, the capacitor _C5 is charged and discharged at the same time, and from time _t2 , it is further charged according to the time constant _R10・_C7 , and as mentioned above, the impact noise is removed. do.

Here, the time constant of resistor R ₂ and capacitor C ₁ was set shorter than the time constant of resistor R ₁₆ and capacitor C ₅ . The high potential signal at the output terminal Q of the flip-flop 7 (see Fig. 2) is connected to a Zener diode.
Applied to ZD ₂ to turn off transistor Q ₂ , and further applied to control terminals g ₃ and g ₄ of analog switches G ₃ and G ₄ through resistor R ₁₃ to turn on analog switches G ₃ and G ₄ . . Furthermore, the output terminal of the flip-flop 7 is at a low potential as in FIG. 2, thereby turning on the transistor _Q3 of the switching section 8. Thereby, the constant voltage of the low voltage supply section ₃ is directly transmitted to the collector which is the output of the transistor Q3, and the power source B ⁺ is supplied to the FM display section 5 and the FM reception section 2. As a result, the FM display section 5 and the FM reception section 2 are driven,
Correctly transmit the FM output signal to output terminals L and R.

Here, from any time t ₅ , change the band from FM to AM.
If the input terminal CK of the flip-flop 7, which is grounded by the switch SW ₁ , is connected to the input terminal T in order to switch to the (toggle) occurs, and the output terminal Q maintains a low potential state, and the output terminal maintains a high potential state (see Fig. 2). Then, the high potential signal at the output terminal turns off the transistor Q ₃ of the switching circuit section 8 to cut off the power supply to the FM receiving section 2, and at the same time is applied to the base of the transistor Q ₄ of the pulse positive polarity component detection section 6. , similarly to that shown in FIG. 2, the transistor Q ₄ is made conductive for a certain period of time t ₅ to t ₆ above the operating voltage of the transistor V _TH . As a result, the output of transistor _Q4 is brought to a low potential state. Thereby,
The voltage charged in capacitor _C5 is momentarily discharged in the same way as shown in Figure 2. Then, charging occurs in the capacitor _C5 from time _t6 onwards. At this time, the input of the inverter _I1 is lower than the operating voltage _Vth from time _t5 to time _t7 . Therefore,
The output of the inverter _I1 turns on the transistors _Q6 and _Q7 and turns off the analog switches _G1 to _G4 , as described above in Figure 2, thereby eliminating impact noise during channel conversion. be done. Also,
The low potential signal of the output terminal Q is sent to the switching circuit section 8.
turns on transistor _Q2 . Therefore,
A power source B ⁺ is outputted to the collector, which is the output terminal of the transistor Q ₂ , and supplies power to the AM display section 4 and the AM receiving section 1 . As a result, both the AM display section 4 and the AM reception section 1 become operational. Note that the high potential signal at the output terminal of flip-flop 7 is passed through resistor _R14 to analog switches _G1 , _G2.
is applied to the control terminals g ₁ and g ₂ of the analog switches G ₁ and G 2 to turn on their analog switches G 1 and G ₂ . This allows you to receive AM signals normally.

In this state, if the switch SW ₁ is turned on/off from an arbitrary time _t8 , the same operation will be performed when the FM band is selected as described above. Furthermore, when the power is turned off at an arbitrary time _t1 , the output terminal Q of the flip-flop 7 becomes a low potential signal, as shown in FIG. As a result, analog switches G ₁ , G ₂ ,
Since the inputs to the control terminals _{g 1 ,} g ₂ , g ₃ , and g ₄ of G 3 and G ₄ are at a low potential, the analog switches G ₁ to _{G 4} are turned off. Therefore, when the power supply B ⁺ is off, the impulsive noise is eliminated.

(Effects of the invention) As explained above, according to the invention, it is possible to select the AM or FM band with a single switch SW ₁ , eliminating parts that consume unnecessary power, and minimizing power wastage. At the same time, it is possible to eliminate noise generated when selecting a band and switching the power on/off.

[Brief explanation of drawings]

Figure 1 is a circuit diagram of an embodiment of the present invention, and Figure 2 is a circuit diagram of an embodiment of the present invention.
1 is a waveform diagram showing signals at each point in the circuit of FIG. 1, and FIG. 3 is a circuit diagram of a conventional AM/FM band selection device. 1...AM receiving section, 2...FM receiving section, 3...
Constant voltage section, 4, 5...Display section, 6...Pulse positive polarity component detection section, 7...Flip-flop, 8...
Switching part.

Claims (1)

[Scope of utility model registration request] In an AM/FM band selection device that outputs the output signals from the AM reception section and the FM reception section to the output terminal through an analog switch, the power supply B ⁺
, Zener diode ZD ₁ , and transistor
Through the constant voltage section 3 with Q ₁ , the transistor
Q ₂ , Q ₃ and the transistors Q ₂ , Q ₃ of the switching section 8 having the Zener diodes ZD ₂ , ZD ₃ are connected, and the two output terminals of the switching section 8 are connected to the display section having the light emitting diodes LD ₁ , LD ₂ . 4 and 5 to the respective power supply terminals of the AM receiving section 1 and the FM receiving section 2, and the bases of the transistors Q ₂ and Q ₃ of the switching section 8 are connected to Zener diodes.
Connected to the output terminal Q of flip-flop 7 through ZD ₂ and ZD ₃ , respectively, and
output terminal Q, of analog switch G ₃ , G ₄
Transistors Q 4 , Q of the pulse positive polarity component detection section 6 are connected to the control terminals of G ₁ , G ₂ and G ₁ , G ₂ respectively, and have transistors Q ₄ , Q ₅ , diodes D 1 , D ₂ , and capacitors G ₃ , G ₄ . ₅ through capacitors C ₃ and C ₄ , and connect the output terminal of the pulse positive polarity component detector 6 to the grounded capacitor C ₅ and the emitter-grounded transistor Q ₆ through the inverter I ₁ .
The collectors of transistors _{Q 6 and} Q ₉ are connected to the output terminal of flip-flop 7, Q. The clock input terminal of flip-flop 7 is connected to the mover contact c of switch SW 1, and the fixed contact a is connected to the base of switch SW ₁ . is grounded, and the fixed contact b is connected to the input terminal T of the flip-flop 7.
AM/FM band selection device.