JPH0336128Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a power supply circuit that can be suitably implemented in a wireless communication device or the like.

BACKGROUND ART In wireless communication devices, it is desirable to smoothly and quickly switch from reception to transmission. In such a wireless communication device, the receiver and the transmitter are switched and energized with power, and it is necessary to perform this power energization switching operation quickly.

Problems to be Solved by the Invention The purpose of the invention is to provide a power supply circuit that can quickly switch between two outputs.

Means for Solving the Problems The present invention is a power supply circuit that selectively supplies power to one of a first electronic device and a second electronic device, the power supply circuit supplying power to either the first electronic device or the second electronic device. a changeover switch that selectively connects; and a changeover switch that controls the changeover switch so that the first electronic device and the power source are connected when the control voltage reaches a predetermined first discrimination level or higher; a first level discrimination circuit that controls the changeover switch to disconnect the first electronic device and the second electronic device of the power source when the voltage drops below a level below the first level discrimination circuit; and controls the changeover switch so that the second electronic device and the power source are connected when the voltage of the power supply line on the first electronic device side of the changeover switch drops below a predetermined second discrimination level. A two-level discrimination circuit, and a diode connected between a connection point of the second level discrimination circuit of the first electronic device side power supply line and the first electronic device so that the connection point side serves as an anode. This is a power supply circuit.

Effect According to the present invention, if the power supply to the power line on the first electronic device side is cut off, even if the voltage drop due to the equivalent capacitance of the first electronic device is slow,
Due to the action of the diode, the voltage at the connection point of the second discrimination level discriminator circuit quickly drops, and interruption of the power supply to the power line can be quickly detected. Therefore, switching from the first electronic device to the second electronic device can be performed quickly. Therefore, it becomes possible to quickly operate the load powered by the second output.

Embodiment FIG. 1 is a block diagram of one embodiment of the present invention. This wireless communication device basically consists of a receiver 1.
, a transmitter 2 , and a power supply circuit 3 . The antenna 4 is selectively connected to the receiver 1 or the transmitter 2 by a changeover switch 5. A high frequency signal from the antenna 4 via the switch 5 is amplified by the high frequency amplification circuit 6 in the receiver 1.
The first mixing circuit 7 mixes the signal with the local oscillation signal from the first local oscillation circuit 8 . The intermediate frequency signal from the first mixing circuit 7 is amplified in the intermediate frequency amplifying circuit 9 and provided to the second mixing circuit 10. A local oscillation signal from a second local oscillation circuit 11 is applied to the second mixing circuit 10 . The output from this second mixing circuit 10 is amplified in a second intermediate frequency amplification circuit 12. In this way, reception is performed using the double superheterodyne system. The output from the second intermediate frequency amplification circuit 12 is applied to a frequency discrimination circuit 14 via a limiter 13, where it is demodulated. From the frequency discrimination circuit 14, the received acoustic signal is led out to a line 15. The signal from this line 15 is amplified in a low frequency amplification circuit 16, and a speaker 17 is driven.

In this receiver 1, a squelch circuit 18 is provided. This squelch circuit 18
Noise amplification circuit 1 that amplifies only signals in a relatively high range of about 25kHz to 30kHz among the signals from
9, rectifying diodes 20, 21, and a smoothing capacitor 22 for smoothing the signal rectified by the rectifying diodes 20, 21, and the output voltage of the smoothing capacitor 22 is transmitted from a line 23 to a noise control circuit 24. Given. When the voltage on line 23 is below a predetermined discrimination level l, noise control circuit 24 activates low frequency amplification circuit 16;
As a result, the speaker 17 is given an audio signal. When the voltage on the line 23 is above the discrimination level I, the noise control circuit 24 disables the low frequency amplification circuit 16 and stops the low frequency amplification function.

In the transmitter 2, the audio signal from the microphone 25 is amplified by the amplification circuit 26, and the audio signal is amplified by the modulation circuit 2.
7 is given. The modulation circuit 27 includes an oscillation circuit 28
A high frequency signal is given from The modulation circuit 27 frequency-modulates the high-frequency signal using the audio signal from the amplifier circuit 26, and supplies it to the multiplier circuit 29 to be multiplied. The output from the multiplier circuit 29 is amplified by a power amplification circuit 30 and is applied to the antenna 4 from the changeover switch 5.

In the power supply circuit 3, a power supply 31 such as a battery
The output voltage is stabilized by a stabilizing circuit 32 and is applied to a protection circuit 34 from a line 33. The protection circuit 34 includes a changeover switch 35
has. The changeover switch 35 has a common contact 36 connected to the line 33 and individual contacts 37 and 38.
has. A control signal from line 39 is provided to a first level discrimination circuit 40. This first discrimination circuit 40 conducts the common contact 36 of the changeover switch 35 to the individual contact 37 when the control signal on the line 39 is higher than the first discrimination level l1, and when the control signal 39 is lower than the discrimination level l1. At this time, the common contact 36 is cut off from the individual contacts 37 and 38. Second
The level discrimination circuit 41 operates when the voltage of the individual contact 37 decreases and becomes less than the second discrimination level l2.
The common contact 36 is switched to the individual contact 38 for conduction. A control signal from line 39 is also provided to third level discrimination circuit 42. The third level discrimination circuit 42 disconnects the common contact 36 from the individual contacts 38 and 37 when the control signal on the line 39 exceeds the third discrimination level l3, and disconnects the common contact 36 from the individual contacts 38 and 37 when the control signal 39 is less than the discrimination level l3. 36 remains electrically connected to the individual contact 38. In the fourth level discrimination circuit 43, the voltage of the individual contact 38 is at the fourth discrimination level l.
When the number becomes less than 4, the common contact 36 is changed to the individual contact 3.
7 to conduct.

Individual contact 37 connects line 44 to diode 4
5 to the receiver 1, thereby energizing the receiver 1. The equivalent capacitance on the input side of the receiver 1 as seen from the diode 45 side is indicated by reference numeral 46. The individual contacts 38 are connected to the transmitter 2 via a line 47.

Line 39 connects to press talk switch 48,
It is connected to a connection point 50 with the resistor 49. The press talk switch 48 is not pressed during reception;
Therefore, line 3 is blocked.
The control signal 9 is at high level. When transmitting, the press talk switch 48 is pressed, thereby causing the control signal on the line 39 to go low. The changeover switch 5 performs a switching operation by operating the pre-talk switch 48 so that the signal from the antenna 4 is applied to the receiver 1 during reception, and the signal from the transmitter 2 is applied to the antenna 4 during transmission.

Line 47 connects line 51 to diode 52
is connected to line 23 via.

During reception, the pre-talk switch 48 is not pressed, so the pre-talk switch 48 is cut off. The control signal on line 39 is as shown in FIG. 2 and remains high before time t1. Therefore, by the action of the first level discrimination circuit 40, the common contact 36 of the changeover switch 35 is electrically connected to the individual contact 37, and the receiver 1 is energized to perform reception.

When switching from reception to transmission and performing transmission using the simplex system, the pre-talk switch 48 is pressed at time t1 to make it conductive. As a result, the control signal on line 39 becomes less than the first discrimination level l1 at time t2. Therefore, the common contact 36 of the changeover switch 35 separates from the individual contact 37 after time t2. The change in voltage on the line 53 on the cathode side of the diode 45 decreases over time after time t2 due to the action of the equivalent capacitance 46, as shown in FIG. 2. The voltage of the individual contacts 37 and therefore of the line 44 drops sharply after time t2, as shown in FIG. At time t3 when the voltage of this line 44 becomes less than the second discrimination level l2, the second level discrimination circuit 41 connects the common contact 36 of the changeover switch 35 to the individual contact 38. Therefore, after time t3, the voltage shown in FIG. 2 and 4 is applied to line 47 in an increased manner. After time t4, normal voltage is applied to the transmitting circuit 2 and transmission becomes possible. In this way, the time W1 from time t1 to t4 is
It is shortened by the function of 5, and in reality, for example, 2
~5mmsec. Therefore, the switching operation from reception to transmission can be performed quickly, and communication can be performed smoothly.

When switching from transmission to reception, time t
At step 5, release the press talk switch 48 to shut it off. As a result, the control signal on line 39 increases after time t5. When the control signal becomes equal to or higher than the third discrimination level l3 at time t5a, the third level discrimination circuit 42 disconnects the common contact 36 of the changeover switch 35 from the individual contacts 38. Therefore, the voltage on line 47 decreases.
When the voltage on the line 47 decreases and reaches the fourth discrimination level l4 at time t6 and becomes less than it, the fourth level discrimination circuit 43 makes the common contact 36 conductive to the individual contact 37 at time t6. This connects line 53 via line 44 and diode 45.
Power is supplied to the receiver 1 from. The functions of the second level discrimination circuit 41 and the fourth level discrimination circuit 43 reliably prevent the receiver 1 and the transmitter 2 from being energized at the same time.

If diode 45 is omitted and lines 44 and 53 are connected directly,
As shown in FIG. 4, from time t2 onwards when the control signal on line 39 becomes less than the first discrimination level l1 as shown in FIG. The time W1a at the time t3 when the discrimination level decreases and becomes less than the discrimination level l2 becomes extremely long. Figure 4 2 is line 4
4.3 shows the voltage waveform of line 4.
7 is shown. When the diode 45 is omitted, the time W1a is long, and the time W2 required for switching from reception to transmission is correspondingly long. This time W2 is, for example, about 50 mmsec, and communication cannot be performed smoothly. In addition,
It is also possible to directly switch the power supply using a pre-talk switch, but in this case, the capacitance of the receiver and transmitter will keep the power supply voltage in each circuit at the operating voltage for a while after the power is turned off, so the receiver and transmitter There is a problem that there is a time when both devices operate, and noise is generated from the receiver side when switching. For this reason, it is common to have a configuration in which the voltages of the power lines of the receiver and transmitter as described above are monitored and the power supply is switched. Generally, the power supply circuit 3 is an integrated circuit, and as shown in FIG. 1, the pre-talk switch 48 is connected and used, which causes the above-mentioned problem that switching takes a long time. Diode 45 helps solve this problem.

In order to explain the operation of the squelch circuit 18, the third
Referring to the figure, the press talk switch 48 is pressed at time t11 as shown in FIG. 31. This causes a switching operation from reception to transmission. Due to the pressing operation of the press talk switch 48, the voltage of the line 53 decreases after time t11, as shown in FIG. 3. The low frequency amplification circuit 16 of this receiver 1 achieves a low frequency amplification function when the voltage on the line 53 is equal to or greater than the value l11, and cannot perform the low frequency amplification function when the voltage on the line 53 is less than the value l11. Time t12 before the voltage on line 53 drops to value l11
, the voltage on line 47 increases. When the voltage on the line 53 is equal to or higher than the value l11, the receiver 1 can perform the receiving operation as shown in FIG. Transmission operation becomes possible after t14.

As shown in FIG. 3, the voltage of the line 23 decreases after time t11, and
2, the smoothing capacitor 22 is charged by the voltage from the line 51 via the diode 52 after time t12 when the common contact 36 of the changeover switch 35 becomes conductive to the individual contact 38. In this way, the voltage V1 on line 23 of smoothing capacitor 22 is greater than or equal to a value that allows noise control circuit 24 to keep low frequency amplifier circuit 16 disabled. Therefore, no noise is generated from the low frequency amplifier circuit 16 to the speaker 17 as shown in FIG. 36.

If line 51 and diode 52 are omitted, press talk switch 48
is pressed at time t11 as shown in FIG. 51, the voltage of line 23 decreases as shown in FIG. 53, and the voltage of line 47 decreases as shown in FIG. 54 at time t12. It increases thereafter. As shown in FIG. 5, the voltage on the line 23 immediately drops after time t11, and therefore, before time t13 when the low frequency amplification circuit 16 can achieve the low frequency amplification function, the noise control circuit 24 The operation of the low frequency amplifier circuit 16 is allowed. Therefore, as shown in FIG.
Noise will be generated. Figure 5 2
The operating states of receiver 1 and transmitter 2 are shown in FIG. When line 51 and diode 52 are omitted in this manner, noise will be generated when switching from receiving to transmitting due to operation of pre-talk switch 48. The present invention solves this problem.

By connecting a capacitor 54 in parallel to the line 44, the time t2 to t shown in FIG.
3 times can be changed.

Effects As described above, according to the present invention, if the power supply to the power line on the first electronic device side is cut off, even if the voltage drop due to the equivalent capacitance of the first electronic device is slow, the diode will not work. As a result, the voltage at the connection point of the second discrimination level discrimination circuit quickly drops, and interruption of power supply to the power line can be quickly detected. Therefore, switching from the first electronic device to the second electronic device can be performed quickly.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of an embodiment of the present invention;
The figure is a waveform diagram for explaining the operation of the power supply circuit 3.
3 is a waveform diagram for explaining the operation of the squelch circuit 18, FIG. 4 is a waveform diagram for explaining the operation when the diode 45 is not provided in the power supply circuit 3, and FIG. 5 is a waveform diagram for explaining the operation of the squelch circuit 18. FIG. 4 is a waveform diagram for explaining the operation when the line 51 and the diode 52 are not provided. 1... Receiver, 2... Transmitter, 3... Power supply circuit, 5... Changeover switch, 14... Frequency discrimination circuit, 16... Low frequency amplification circuit, 17... Speaker, 19... Noise amplification circuit , 20, 21, 52
... Diode, 22 ... Smoothing capacitor, 24
... Noise control circuit, 32 ... Stability circuit, 34 ...
...switch circuit, 35...changeover switch.

Claims (1)

[Claims for Utility Model Registration] A power supply circuit that selectively supplies power to one of a first electronic device and a second electronic device, the power source being selectively connected to the first electronic device and the second electronic device. a changeover switch that controls the changeover switch so that the first electronic device and the power source are connected when the control voltage reaches a predetermined first discrimination level or higher, and the control voltage becomes lower than the predetermined first discrimination level; a first level discrimination circuit that controls the changeover switch to disconnect the first electronic device and the second electronic device of the power source when the first electronic device is connected to the first electronic device side of the changeover switch; , a second level discrimination circuit that controls the changeover switch so that the second electronic device and the power source are connected when the voltage of the first electronic device side power line of the changeover switch drops below a predetermined second discrimination level; and a power supply circuit comprising a diode connected between a connection point of the second level discrimination circuit of the first electronic device side power line and the first electronic device so that the connection point side serves as an anode. .