JPH06101774B2 - Telephone - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a telephone, and more particularly to a telephone having a built-in microcomputer, which can be used as a power source for the microcomputer by using a voltage placed on a public line.

[Prior art]

In the telephone of this type described as the prior art of Japanese Utility Model Laid-Open No. 58-123656, after the off-hook, it is detected that the power supply voltage becomes a constant voltage value higher than the operation guarantee voltage of the control circuit, and the The reset was released and the control operation was started.

[Problems to be Solved by the Invention]

However, if this conventional technology is applied to, for example, a public telephone, and a coin return prevention magnet is operated to put it in a coin storage standby state after off-hook, or if a sensor system is driven to perform a self-diagnosis operation, that is the only case. As a result of consuming a relatively large amount of power, there is a problem that the power supply voltage of the control circuit falls below the above-mentioned constant voltage value and is reset again during the control operation.

Therefore, a main object of the present invention is to provide a telephone which can effectively continue the control operation even when applied to the case where relatively large power is consumed.

[Means for Solving the Problems]

Briefly, the present invention is a full-wave rectification circuit, which is connected to a public line and receives the voltage placed on the telephone, in which a power source for a built-in microcomputer is obtained by using the voltage of the public line. A first switch connected to the output of the rectifier circuit and turned off in response to a first level of the dial pulse signal, an inductor connected in series with the first switch, and a branch connection between the first switch and the inductor A backflow prevention element that allows only current in the direction of the inductor, a capacitor that is branched and connected between the output side of the inductor and a predetermined potential, and is charged by the current flowing in the inductor, and a capacitor between the inductor and the capacitor. Is connected in parallel to the first switch and is turned off in response to the first level of the dial pulse signal so as to be synchronized with the first switch. A series circuit of a second switch and a resistor, the current flowing through the inductor charging the capacitor when the first and second switches are turned on, and the inductor when the first and second switches are turned off. ，
A telephone in which a closed loop of a capacitor, a backflow preventing element and an inductor forms a stored energy in the inductor to charge the capacitor, and a terminal voltage of the capacitor is supplied as a power source for a microcomputer.

[Action]

For example, when the hook switch is closed, the first switch is turned on, and a current flows through the capacitor via the full-wave rectifier circuit-first switch-inductor, and a predetermined charge is accumulated. When the dial pulse signal is output, the first
Switch and the second switch are turned off or turned on in response to the high level or the low level of the dial pulse signal, so that the capacitor repeats charging and discharging.

That is, when the dial pulse signal is at high level, the first
And the second switch are both turned off, and the inductor-
A closed loop is formed in the path of the capacitor-backflow prevention element-inductor. Then, the electromagnetic energy accumulated in the inductor is released to the capacitor, and the capacitor is further charged. On the other hand, when the dial pulse signal is at the low level, both the first and second switches are turned on, and the capacitor is charged so that the terminal voltage of the capacitor is kept above the operating voltage of the microcomputer. The terminal voltage of this capacitor is supplied to the power supply terminal of the microcomputer as a power supply, for example, through a constant voltage circuit.

〔The invention's effect〕

According to the present invention, since the terminal voltage of the capacitor does not fall below the operating voltage of the microcomputer, there is no fear of malfunction of the microcomputer due to power interruption, and its handling becomes easier.

The above-mentioned objects, other objects, features and advantages of the present invention will become more apparent from the following detailed description of the embodiments with reference to the drawings.

〔Example〕

FIG. 1 is a circuit diagram showing an embodiment of the present invention. In this embodiment, power supply circuit 10 is connected to public line terminals or rosette terminals 12a and 12b. A DC voltage placed on the public line is output to the rosette terminals 12a and 12b, and the DC voltage is output by the full-wave rectifier circuit 14 as a voltage of a predetermined polarity (positive polarity in the embodiment) regardless of the polarity. It is rectified and output.

The output of the full-wave rectifier circuit 14 is a PN that constitutes the first switch.
The emitter of the P transistor 16 is connected, and the base of the transistor 16 is connected to the collector of the NPN transistor 18. The base of the transistor 18 is also NP
N transistor 20 is connected. And transistor 1
A series circuit of a diode 22 and a resistor is connected between the collector of 6 and the connection point of the base of transistor 18 and the collector of transistor 20. The diode 22 has its anode connected to the collector of the transistor 16 and its cathode connected to the resistor described above. Also, the transistor 16
A hook switch 24, which is operated by a handset (not shown), is connected between the emitter and the connection point described above. The dial pulse signal DP from the microcomputer 26 is applied to the base of the transistor 20.

The output voltage of the transistor 16 is supplied as the power supply voltage of the audio circuit 28 as the voltage Vs, and the collector of the transistor 16 is connected to the inductor 30. The other end of the inductor 30 is connected to one end of a capacitor 34 through the anode-cathode of a diode 32, and the other end of the capacitor 34 is grounded. Further, a battery 36 is connected to the capacitor 34 through a diode 38 for blocking a reverse current. To the capacitor 34, a constant voltage circuit 48 such as a collector output type three-terminal regulator is connected in parallel in order to protect the semiconductor element and the like from being damaged by overvoltage. The voltage across the constant voltage circuit 48 is applied to the power supply terminal Vcc of the microcomputer 26 as the power supply voltage.

A diode 42 in the reverse direction is connected between the connection point of the diode 22 and the inductor 30 and the ground. That is, the cathode of the diode 42 is connected to the inductor 30, and the anode is grounded. This diode 42 is an inductor when the transistors 16 and 46 are off.
It is for allowing a closed loop to be formed for the discharge current from 30. In addition, a series circuit of a resistor 44 and an NPN transistor 46 forming a second switch is connected between the connection point of the inductor 30 and the diode 32 and the ground. Resistor 44 is chosen to have a relatively high resistance. Thus, by using a relatively high resistance element for the resistor 44, the resistor 44 has the function of limiting the current flowing through the inductor 30 to the transistor 46 and the inductor 30 when the transistor 46 is turned on, and It also has the function of allowing the capacitor 34 to be charged by the current even when is on. Then, at the base of the transistor 46, a dial section signal DP 'which is at a high level from the microcomputer 26 (a period from the start of the dial just before the start of the first digit dial pulse to the final pulse) is high. Given. However, when the dial pulse signal DP ′ is at a high level and the dial pulse signal DP is turned on, the transistor 46 is turned off, and conversely, when the dial pulse signal DP is turned off, the transistor 46 is turned on. Given. That is,
The transistor 46 is supplied with a signal (on / off) obtained by inverting the dial pulse signal DP by the diode 47 and the transistor 20.

In operation, when a handset (not shown) is lifted to make a call, the hook switch 24 is turned on as shown in FIG. 2 (A). Therefore, the output current of the full-wave rectifier circuit 14 flows through the hook switch 24 to the base of the transistor 18, and as shown in FIGS. 2 (D) and (E),
Transistors 18 and 16 are each turned on. here,
2A shows the voltage on the contact 24a side of the hook switch 24, and FIGS. 2B and 2B show the output voltage of the dial pulse signal DP and the dial section signal DP ', respectively.
2 (C) to (F) show the collector voltage of each transistor.

Therefore, lift the handset and
When is turned on, at that time, the current from the public line, that is, the output from the full-wave rectification circuit 14 flows into the capacitor 34 through the transistor 16-inductor 30-diode 32. In response to this, the capacitor 34 is charged, and as shown in FIG. 2 (G), the terminal voltage of the capacitor 34 starts to rise rapidly (time T0) and saturates at time T2. Capacitor
The terminal voltage of 34 is the operating voltage Vth of the microcomputer 26.
When the above is reached, the microcomputer 26 immediately rises and starts a predetermined operation (time point T1).

Thus, no signal is output from the microcomputer 26 at the time of picking up the handset, and no signal is output since the microcomputer has not even started up at this time. However, the microcomputer 26
After turning on the hook switch 24 (lifting the handset),
Since it starts up in a very short time, the user actually presses the numeric keypad immediately and operates as follows without any problem.

When a user who picks up the handset inputs a telephone number using a dial (or a ten-key pad) (not shown), the microcomputer 26 causes the microcomputer 26 shown in FIGS. 2 (B) and 2 (B ').
The dial pulse signal DP and the dial section signal DP 'are output as shown in FIG. Dial pulse signal DP
Is high level, the transistor 20 is turned on as shown in FIG. 2 (C), the transistor 18 is turned off as shown in FIG. 2 (D), and the transistor 16 is turned on as shown in FIG. 2 (E). Turn off. At this time, since the transistor 20 is turned on, the transistor 46 is turned off as shown in FIG. On the other hand, when the dial pulse signal DP is at low level, the transistor 20 turns off, the transistor 18 turns on, and the transistors 16 and 46 turn on. In this way, the transistors 16 and 46 are turned on / off in synchronization. Therefore, the dial pulse signal from the microcomputer 26
In response to turning on or off transistors 16 and 46 associated with the delivery of DP, the charging current into capacitor 34 is controlled. Therefore, the terminal voltage of the capacitor 34 changes as shown in FIG.
Is applied as a power source.

The operation of this embodiment will now be described in more detail with reference to FIG. 2 and FIG. 3, which is an equivalent circuit diagram.
In response to the low level dial pulse signal DP from the microcomputer 26 shown in FIG. 2 (B), as shown in FIG. 2 (E) and FIG.
When 16 and 46 are turned on at the same time, a current i ₀ expressed by the following equation (1) flows through the inductor 30.

i ₀ = {E / (R + r)} e ^{−L / (R + r) t} (1) where E is the output voltage of the full-wave rectifier circuit 14, r is the resistance value of the inductor 30, and L is the inductor. 30 inductance, R
Is the resistance value of the resistor 44.

Therefore, the electromagnetic energy represented by the following equation (2) is accumulated in the inductor 30.

ε = (1/2) Li ₀ ² (2) Even when the transistors 16 and 46 are turned on at the same time, a current flows to the capacitor 34 via the diode 32 for preventing backflow, so that the capacitor 34 34 is well charged, and the terminal voltage of the capacitor 34 is kept above the operating voltage Vth of the microcomputer 26, as shown in FIG.

Then, as shown in FIG. 2 (B), the dial pulse signal
When DP goes high, both transistors 16 and 46 are turned off, as shown in FIGS. 2 (E) and 2 (F). At this time, the electromagnetic energy stored in the inductor 30 is transferred to the inductor 30-diode 32-capacitor.
34-diode 42-emitted through the path of inductor 30. The capacitor 34 is charged by the emitted electromagnetic energy.

At this time, if all the stored energy of the inductor 30 is charged in the capacitor 34, the electromagnetic energy (1/2) Li ₀
² = electrostatic energy (1/2) CVc ² , and the voltage Vc represented by the following equation (3) is generated across the capacitor 34.

Therefore, even when the transistor 16 is off, the electromagnetic energy emitted from the inductor 30 causes the capacitor to
Since 34 is charged, the voltage across the capacitor 34 during that period can be further increased, as shown in FIG.

In this way, the power supply voltage of the built-in microcomputer 26 can be obtained by utilizing the DC voltage placed on the public line, and even if the public line voltage is low, the voltage Vc across the capacitor 34 is It does not fall below the operating voltage Vth of the computer 26, so that malfunction of the microcomputer 26 is effectively prevented.

In the above-described embodiment, since the dial pulse signal is not output in the case of reception, there is no charge / discharge of the capacitor 34 due to the turning on or off of the transistor 16, and therefore the voltage drop across the capacitor 34 is a problem. It never happens.

Furthermore, in the above-described embodiment, only the power supply voltage of the microcomputer 26 has been described, but it is possible to use the terminal voltage of the capacitor 34 as another semiconductor element such as an additional memory or other power supply voltage if necessary. There is no end.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention. FIG. 2 is a waveform chart of each part for explaining the operation of this embodiment. FIG. 3 is an equivalent circuit diagram for explaining the operation of this embodiment. In the figure, 10 is a power circuit, 12a and 12b are public line terminals (rosette terminals), 14 is a full-wave rectifier circuit, 16 is a PNP transistor, 18,20 and 46 are NPN transistors, 24 is a hook switch, and 26 is a microcomputer. , 30 is an inductor,
32 and 42 are diodes, 34 is a capacitor, 40 is a Zener diode, 44 is a resistor, and 48 is a constant voltage circuit.

Claims (3)

[Claims] 1. A power supply for a built-in microcomputer,
A telephone obtained by using the voltage of a public line, wherein the full-wave rectifier circuit is connected to the public line and receives a voltage placed on the public line, and the first level of a dial pulse signal is connected to an output of the full-wave rectifier circuit. A first switch that is turned off in response to the first switch, an inductor that is connected in series to the first switch, a branch connection between the first switch and the inductor, and allows only a current in the inductor direction. A backflow prevention element, a capacitor branched and connected between the output side of the inductor and a predetermined potential, and charged by a current flowing in the inductor, and connected in parallel to the capacitor between the inductor and the capacitor. And is turned off in response to the first level of the dial pulse signal so as to be synchronized with the first switch. A series circuit of two switches and a resistor, when the first and second switches are turned on, the current passing through the inductor charges the capacitor, and the first and second switches are turned off. A telephone which forms a closed loop of the inductor, the capacitor, the backflow prevention element, and the inductor to store energy in the inductor to charge the capacitor, and the terminal voltage of the capacitor is supplied as a power source of the microcomputer. 2. A telephone as claimed in claim 1, comprising means for turning on or off the first switch in response to a hook switch. 3. The telephone set according to claim 1, further comprising a constant voltage circuit that receives the output of the capacitor.