JPH021940Y2 - - Google Patents

Description

[Detailed Description of the Invention] Technical Field of the Invention The present invention relates to an integrated circuit for multiple power supplies that can be switched alternately, and attempts to output a signal when the power supply is switched so that the signal can be used to easily prevent popping noises, etc. It is something to do.

Prior Art and Problems When switching from AM to FM in an AM/FM radio or vice versa, and when switching between transmitting and receiving in a transceiver, the power supply is also switched, but this switching is performed using transistors rather than relays with mechanical contacts. This is being done using electronic circuits using . The present inventor developed and proposed this type of switching circuit as an integrated circuit (Japanese Utility Model Publication No. 163639/1983).

By the way, when the power is turned on and off, there is a tendency for a popping noise to come from the speakers.
To prevent this, measures can be taken such as turning on the transistor connected between the signal circuit and ground when disconnecting to drop the signal to ground, or activating the amplifier's gain adjustment circuit to reduce the gain. There is. It has been found that this mute signal can be easily derived from the switching circuit devised by the present inventor.

Purpose of the invention The present invention focuses on this point, and uses a simple method of adding a few circuit elements to the switching integrated circuit described above to prevent abnormal noises that occur when switching the power supply. The aim is to make it possible to output signals that can be provided.

Structure of the invention The present invention includes a first amplifier that receives a reference voltage and a negative feedback voltage and generates a first power supply voltage, and a first amplifier that receives a reference voltage and a negative feedback voltage and generates a second power supply voltage. 2 amplifiers, a reference voltage applied to these amplifiers, a transistor to be grounded, and a control signal for starting up the power supply, and when the voltage of the other power supply is below a predetermined value, the transistor is turned off and the reference voltage is lowered. In a multi-power integrated circuit that includes a logic gate that inputs the reference voltage to an amplifier, when a transistor that charges a capacitor and a transistor that drops the reference voltage to ground are both on, the charging transistor is turned on and the charging is performed. The capacitor is characterized by having a gate and outputting the voltage of the capacitor to the outside, which will be described in detail below with reference to embodiments.

Embodiment of the invention Figure 1 shows the main parts of a multi-power supply integrated circuit,
The circuit above the chain line is the already proposed circuit. The details of this circuit and its modifications are explained in the above-mentioned publication, but to give an overview, the terminals T ₁ and T ₂ are output terminals, and the voltages V ₀₁ and V ₀₂ outputted from these are the above-mentioned AM /Powers the AM and FM sections of an FM radio or the transmitter and receiver of a transceiver. Of course, the outputs V ₀₁ and V ₀₂ may be used as switch control signals for such a power supply so as to be able to handle large amounts of power. Here, V ₀₁ and V ₀₂ are the first and second
It is used as a power source. A ₁ and A ₃ are amplifiers that output voltages V ₀₁ and V ₀₂ , and the voltages V 01 and V ₀₂ are proportional to the reference voltage _VR .
Produces V ₀₂ . The control of this part, that is, the mode of constant voltage control, is well known. For example, the reference voltage V _R is applied as is or after being divided and applied to the positive input terminal of the differential amplifier A ₁ , and the output voltage V ₀₂ is applied as is or as a divided voltage. The voltage is divided and applied to the negative input terminal of the differential amplifier _A1 , and the output voltage _V02 is maintained at a constant value proportional to the reference voltage _VR by negative feedback control. The proportionality coefficient is determined by the ratio of the above partial pressures. In this circuit, this can be easily done by using the resistor R ₁
It is expressed as The same applies to the output voltage V ₀₁ , and the resistance R ₂ represents its proportional coefficient.

Terminal _T3 is a terminal to which switching control voltage Vc is input. When the control voltage Vc is set to H (high) level and the output of amplifier _A4 is also at H level, the output of NAND gate _G1 is set to L (low) level,
Transistor T ₃ is off, so the reference voltage V _R is input to amplifier A ₁ producing the aforementioned output voltage V ₀₂ .
At this time, the output of the inverter _G4 is at the L level, and therefore the output of the NAND gate _G2 is at the H level, and the transistor _TR4 is turned on.Therefore, the reference voltage input terminal of the amplifier _A3 is grounded by the transistor TR4, and the output of the NAND gate _G2 is at the H level. The output voltage V ₀₁ of amplifier A ₃ is 0 volts. If this voltage V ₀₁ entering the negative input terminal is 0, the amplifier A ₄ produces an H level output due to the threshold voltage V _TH received at the positive input terminal, which is applied to the input of the NAND gate G ₁ . That is, the above A ₄ output H, G ₁ output L
conditions will be maintained. That is, when Vc=H, this circuit produces an output voltage V ₀₂ and V ₀₁ is set to 0.

When the control voltage Vc is set to L, the output of NAND gate _G1 is H, transistor _TR3 is on, and amplifier _A1
The output V ₀₂ becomes 0. However, a power supply circuit generally includes a capacitor, and even if power supply is stopped, the voltage does not become zero until the capacitor finishes discharging. If the voltage V ₀₂ is a normal value, it is higher than the threshold voltage V _TH (V _TH is defined as such), so the output of the amplifier A ₂ is at L level, and at this point also the NAND gate
The output of _G2 was at H level, but Vc=L, so when the output of _G4 becomes H, one of the conditions for _G2 to set its output to L level is satisfied. However, unless the supply voltage V ₀₂ falls below the threshold voltage V _TH, the amplifier
Since the output of _A2 is L level, the NAND gate
The output of _G2 remains high and transistor _TR4 is on. Therefore, the reference voltage input terminal of the amplifier _A3 remains grounded, and the output _V01 remains at zero.

When the discharge of the capacitor progresses and V ₀₂ becomes less than V _TH , the output of amplifier A ₂ becomes H, and the output of G ₄ also becomes H.
Therefore, the output of NAND gate _G2 becomes L level, turning off transistor _TR4 . As a result, the reference voltage V _R is input to the amplifier A ₃ , and the amplifier A ₃ outputs the aforementioned voltage V ₀₁ . Thus the power supply is V ₀₂
to V ₀₁ . To further switch the power supply from V ₀₁ to V ₀₂ , all you have to do is return the control voltage Vc to the H level.
In this case as well, switching takes place only when the voltage V ₀₁ becomes lower than the threshold voltage V _TH .

FIG. 2 illustrates and explains this. When the control voltage Vc rises (becomes H) at time t1, the output of the amplifier _A3 is not at 0, and the voltage _V01 falls as the capacitor discharges. When V ₀₁ V _TH is reached at time t2, the output of amplifier _A4 becomes H level, and the NAND gate
The output of _G1 is L, the transistor _TR3 is turned off, and the amplifier _A1 outputs a voltage _V02 .

The above-mentioned control, in which the power supply is not switched immediately and the next power supply is turned on only after the voltage of the currently operating power supply has dropped sufficiently, is the subject of previously proposed circuits, and this allows both systems to operate simultaneously, e.g. A transceiver eliminates the problem of noise being generated by receiving the end of its own transmitted signal. If electronic switching is performed instead of switching using relay contacts, the above-mentioned problem is likely to occur because the switching operation is quick, and this circuit is effective in preventing this problem.

By the way, as explained above, from V ₀₂
When switching to V ₀₁ , there is a period in which transistors TR ₃ and TR ₄ are both on. In FIG. 2, this period is from time t1 to time t2. Power supply V ₀₁
The same applies when switching from V 02 to V ₀₂ . As is well known, when switching the power source, in other words, when connecting or disconnecting the power source, a popping sound is generated, and muting circuits have been developed to prevent this. To suppress pop noise, it is effective to ground the signal circuit or lower the gain of the amplifier when the power is disconnected.To completely suppress the pop noise, disconnect the circuit that performs such control when the power is connected or disconnected. What is necessary is to operate it during a predetermined period spanning before and after. Although such a control circuit is simple and can be constructed simply from one transistor, it is troublesome to create a control signal for the transistor because it requires special additional means. However, in this circuit, as mentioned above, the transistors TR ₃ and TR ₄ are switched off during the period t1 to t2.
There is a phenomenon where both are turned on. The present invention attempts to utilize this to easily generate the control signal.

The circuit below the chain line in FIG. 1 shows an embodiment of the present invention. _G3 is a NOR gate, and its two input terminals are connected to the collectors of transistors _TR3 and _TR4 , and its output terminal is connected to the base of transistor _TR5 .
The collector of the transistor TR ₅ is connected to the power supply Vcc of this integrated circuit, and the emitter is connected to the output terminal T ₄ . A load resistor R and a capacitor C are connected between the output terminal _T4 and the ground. These R,
Although up to C may be included in the integrated circuit, these may also be externally attached.

The operation of this circuit will be clear from the above explanation, but when both transistors TR ₃ and TR ₄ are on, and their collectors are at L level, the NOR gate is activated.
The output of _G3 becomes H level, and the transistor _TR5
turns on. Capacitor C is therefore charged. The period (t2-t1) during which both transistors TR ₃ and TR ₄ are on is a short time of about 1 μS, and after this period, the output of NOR gate G ₃ returns to L level and transistor TR ₅ is turned off. However, since the capacitor C has been charged, the output voltage V ₀₃ will not become 0 until it is discharged. i.e. voltage
V ₀₃ gradually decreases with an RC discharge curve as shown in FIG. 2, and if the miute circuit or the like is enabled up to the threshold value Vth, the circuit can be operated during this period (t3-t1). This capacitor C outputs
The pulse width of V ₀₃ can be expanded as appropriate. The generation timing of the output V ₀₃ is approximately equal to the H/L switching timing of the control voltage Vc.

Effects of the Invention As explained above, according to the present invention, it is possible to easily generate a signal to prevent an abnormality that occurs when switching power sources by using a part of the multi-power switching circuit, and it is extremely effective.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, and FIG. 2 is a waveform diagram for explaining the operation. In the drawing, V _R is the reference voltage, V ₀₁ and V ₀₂ are the first and second
A ₁ and A ₂ are amplifiers that generate the power supply voltage, TR ₃ and TR ₄ are transistors that connect the reference voltage to the ground, Vc is a control voltage, and G1 and G2 are
is a logic gate, C is a capacitor, TR ₅ is a charging transistor, and G ₃ is a logic gate for controlling TR ₅ .

Claims (1)

[Claims for Utility Model Registration] A first amplifier that receives a reference voltage and a negative feedback voltage and generates a first power supply voltage; and a first amplifier that receives a reference voltage and a negative feedback voltage and generates a second power supply voltage. A second amplifier, a transistor that lowers the reference voltage applied to these amplifiers to the ground, and a control signal for turning on the power supply is input, and when the voltage of the other power supply is below a predetermined value, the transistor is turned off and the reference voltage is grounded. In a multi-power supply integrated circuit equipped with a logic gate that inputs a voltage to an amplifier, when a transistor that charges a capacitor and a transistor that drops the reference voltage to ground are both on, the charging transistor is turned on to perform the charging. A multi-power supply integrated circuit comprising a logic gate and outputting the voltage of the capacitor to the outside.