JPH0635638Y2 - Power supply - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field of the Present Invention> The present invention relates to a power supply device for supplying power to, for example, a telephone device.

<Prior Art> In recent years, automobiles, buses, or trains equipped with a telephone device have been put into practical use, but the power source of the telephone device is usually supplied from a battery provided in these moving bodies (buses or trains). There is.

However, in these mobile units, the power supply voltage drops sharply due to disconnection between the battery and the telephone device due to vibration or improper maintenance, or temporary interruption of power supply due to aging of the battery itself. Sometimes. At this time, if the user is on a call, prepaid charges (coins, etc.) may not be returned even though the call is blocked, or the telephone card, etc. may remain inside the device and not return. It is necessary to protect the user's disadvantage. For this reason, in preparation for such temporary power interruption, it is necessary to perform the minimum processing at that time, for example, to return the previously sucked coins or return the telephone card. A charge / discharge circuit for backup is provided.

Conventionally, such a charging / discharging circuit changes from a battery to a large-capacity capacitor via a fuse, a diode, and a current limiting resistor each time the Fuchs switch of the telephone device is turned on (the handset is removed). Charging is performed rapidly, and when the power is cut off, the electric charge charged in the capacitor is discharged to the telephone device so that the operation of the telephone device is maintained for a predetermined time (for example, one call).

Note that the current limiting resistor limits the maximum value of the charging current from the battery to the capacitor that is momentarily short-circuited at the start of charging so that a current greater than the battery capacity does not flow into the capacitor. The fuse is a fixed resistor and protects the battery against a short circuit of the charge / discharge circuit for a predetermined time or longer (for example, a defective capacitor).

<Problems to be solved by the present invention> However, the power capacity of the current limiting resistor is
If the power supply voltage of the battery is, for example, 24 V, and the maximum current that flows is 2 A, a battery having a power supply device of 50 W is required, and the shape of the resistor becomes very large, resulting in a large power supply device. In addition, the self-heating of the resistor causes the ambient temperature to become very high, which adversely affects the peripheral circuits, so it cannot be housed in a miniaturized telephone device. To set up
Alternatively, a forced cooling device such as a fan must be installed together.

Therefore, the overall shape of the telephone device becomes large and complicated accordingly, and it is a big obstacle particularly in the case where the installation space of the telephone device is limited such as a car such as a bus or a train.

Also, if the capacitor for charging becomes defective and the short-circuited state continues, this short-circuit current always flows through the resistor,
There is a possibility that a secondary accident such as a burnout of a resistor or an over-discharge of a battery may be caused, and passengers such as a bus or train, or people around the device may be extremely disturbed.

In addition, since the voltage discharged from the charge / discharge circuit has low stability, it is necessary to further increase the capacity of the capacitor when the device that is vulnerable to fluctuations in power supply is a load. There was a problem of becoming.

Further, even if it is detected that the power supply is cut off by on-hook as described above, when the battery power supply is cut off or short-circuited during off-hook, the conventional power supply device cannot detect this, which is a big problem for the user. It could cause damage.

An object of the present invention is to provide a power supply device that solves such problems.

<Means for Solving the Problems> In order to solve the problems, a power supply device of the present invention is a DC power supply such as a battery, and a load device that converts a voltage from the DC power supply into a predetermined voltage. The DC / DC converter is supplied to the DC power supply and the semiconductor resistance element whose resistance value suddenly changes from a low resistance to a high resistance when the temperature rises above a predetermined temperature. When the DC power is cut off or the voltage drops, the DC
A charge / discharge circuit that discharges to the / DC converter and maintains the operation of the load device for a predetermined time, the input voltage of the DC / DC converter, the rated voltage of the DC power supply and the DC / DC converter to the load device. And a voltage detection circuit for detecting whether or not the voltage is lower than a predetermined voltage between the minimum voltage required to supply the predetermined voltage.

<Operation> Therefore, in the power supply device of the present invention, in the charging / discharging circuit, the semiconductor resistance element rapidly charges the capacitor from the DC power supply with a low resistance value at the initial stage of charging, and the large current causes the semiconductor resistance element to be charged. When the temperature exceeds a predetermined temperature, the resistance suddenly changes to a high resistance, and the charging current becomes extremely small. When the DC power supply is cut off or short-circuited, the charge / discharge circuit discharges the DC / DC converter.
The predetermined voltage is supplied to the load device while the discharge voltage decreases to the predetermined voltage.

Further, the voltage detection circuit detects that the input voltage of the DC / DC converter has dropped to a predetermined voltage.

<Embodiment of the Invention> (FIGS. 1 to 4) Hereinafter, one embodiment of the invention will be described with reference to the drawings. FIG. 1 is a block diagram of a telephone device equipped with a power supply device to which the present invention is applied.

This telephone device is a telephone device installed on a train and configured exclusively for a time card. In the figure, reference numeral 1 indicates information read from an accepted magnetic card, and this read signal is used by a control device 2
Is a card reader / writer which receives the write signal from the control device 2 and writes new information to the magnetic card to carry it out.

A telephone 3 is composed of a handset, a dial key, a call circuit (both not shown), and the like.

Reference numeral 4 designates dial data or voice signal from the telephone 3,
A wireless device for transmitting to a base station (not shown) via the antenna 4a and connecting to a telephone line.

Note that the card reader / writer 1, the telephone 3, and the wireless device 4 are subjected to various controls necessary for a call by the control device 2. For example, a charging signal from the station side is transmitted to the wireless device 4
When the call is received, the balance of the magnetic card is calculated and written to the magnetic card at the end of the call.

Each of these blocks has, for example, a 12V battery power source 5
From the power supply device 6.

FIG. 2 shows a main part of the power supply device 6.

In FIG. 2, 11 is a charging / discharging circuit, and a power supply line 13
The power source voltage of 12V is supplied from the battery power source 5 at the same time when the handset of the telephone 3 is picked up and its hook switch (not shown) is turned on.

The power line 13 has two diodes 14A, 1 for preventing backflow.
The anode side of 4B is connected and this diode 14A, 1
The cathode side of 4B is connected to the (+) side input line 17 of the DC / DC converter 19. The input line 17 is connected to the two semiconductor resistance elements 15A and 15B and the cathode side of the diodes 16A and 16B for discharging from the capacitor, and the other ends of the semiconductor resistance elements 15A and 15B and the diode.
Both anode sides of 16A and 16B are connected to one end side of a large-capacity (tens of thousands μF) capacitor 12 through a line 20. The other end of the capacitor 12 is connected to the DC / DC converter 1
It is connected to the input line 18 on the (-) side of 9. In addition,
These semiconductor resistance elements 15A and 15B are small resistance elements made of a semiconductor having a positive temperature coefficient. As shown in FIG. 3, the ambient temperature (including self-heating) exceeds a predetermined value due to self-heating or the like. Then, the resistance value increases sharply (known by the product names such as posistor and ceramics).

The DC / DC converter 19 is a circuit for converting the power supply voltage (approximately 12 V) from the battery power supply 5 input to the input lines 17 and 18 into 24 V, and the capacitor 23 is provided between the output lines 21 and 22.
Is connected and the output voltage 24V is sent to the control device 2, the card reader / line 1 and the like. The control device 2 is further supplied with power converted to, for example, 5V by a constant voltage circuit (not shown) or the like.

On the other hand, in the figure, reference numeral 25 is a voltage detection circuit, which is a circuit for detecting the voltage of the input line 17 and outputting a detection signal notifying the controller 2 of the voltage drop when the voltage becomes a predetermined value or less. is there.

That is, a choke coil for removing noise from the input line 17
Via 28, the voltage divided by resistors 29, 30 is detected by a voltage detector 31.

The voltage detector 31 sends a detection signal of H level to the control device 2 through the output line 33 when the voltage of the input line 32 is a predetermined voltage, for example, 5 V or more, and when it becomes 5 V or less. .

When the control device 2 receives the H-level detection signal, it performs normal call control, and when it receives the L-level detection signal, for example, bills and ends the call such as returning the card. Control for.

A diode 35 is connected between the power supply line 13 and the output line 33. This diode 35 is provided in the battery power supply 5 for forcibly setting the potential of the output line 33 of the voltage detector 31 to the L level and notifying the control device 2 of the abnormality when the power supply line 13 is short-circuited. There is.

When the voltage of the input line 32 of the voltage detector 31 fluctuates around 5V or when pulsating noise is included, the capacitor 36 delays the output response and changes its output from H level to L level. It is a capacitor that is inserted so as to prevent the control device 2 from malfunctioning while preventing a drastic change in the interval.

In addition, the resistor 37 is connected to the battery line 5 for the power line 13.
When the power supply from the unit is cut off (disconnected), the diode
A current is supplied from the output line 33 via 35 to quickly discharge the electric charge of the capacitor 36 and to speed up the output response of the detection signal.

<Operation of the Embodiment> (FIG. 4) Next, the operation of the embodiment will be described.

First, when the user picks up the handset of the telephone 3 to make a call, the hook switch is turned on, the power supply voltage 12V from the battery power supply 5 is supplied to the power supply line 13, and the diodes 14A, 14B and Semiconductor resistance element 15
A charging current flows through the capacitor 12 via A and 15B. As shown in FIG. 4, this charging is performed with a large current for a predetermined time,
Due to the rapid increase in the resistance value due to the heat generation of the semiconductor resistance element, the charging current decreases and the required charging is completed.

At this time, for example, assuming that the resistance values of the semiconductor resistance elements 15A and 15B at low temperatures are 12Ω, the charging current for the capacitor 12 is about 2 A, and this charging is completed in about several seconds.

At this time, the voltage (approximately 12V) input to the DC / DC converter 19 is converted into a voltage of 24V, and the output line 21,
Control device 3 and card reader / writer 1 via 22
Etc.

In this way, after the receiver is picked up, the input voltage to the input line 32 of the voltage detector 31 is usually 5 V or higher, and the H level detection signal is output from the output line 33 to the control device 2. Then, the control device 2 controls the call for each block.

Here, the user inserts the magnetic card into the card reader / writer 1
Then, the magnetic information read from this card is sent to the control device 2 for processing such as identification and balance storage, and the telephone 3 can be used. When the user operates a dial key (not shown), this dial data is sent to the wireless device 4, sent from the train to the base station via the antenna 4a, connected to the telephone line, and called by the other party. Is performed.

When the other party responds, the charging signal from the station side is transmitted to the wireless device 4
Is input to the telephone 3 via the, and the control device 2 detects this and subtracts the card balance or only once.

While the call continues, the control device 2 calculates the balance each time the billing signal is input.

Here, when the call ends and the user hangs up the handset on the telephone 3, the hook switch (not shown) is turned off, so that the charge charged in the capacitor 12 of the charging device 11 becomes the diode 16A. , 16B to the DC / DC converter 19.

Therefore, the power supply to the card reader / writer 1 and the control device 2 is maintained, and the control device 2 which receives the call end signal from the telephone 3 during this time controls the card reader / writer 1 to eject the card, Write on a magnetic card.

As a result, the normal call operation ends, the electric charge charged in the capacitor 12 also decreases, and the power supply to the card reader / writer 1 and the control device 2 is stopped.

For example, if the battery power supply 5 or the power supply line 13 is short-circuited while the other party is calling or talking,
Discharging from the capacitor 12 of the charging / discharging circuit 11 is started, and power is supplied to the card reader / writer 1 and the control device 2 for a predetermined time (a few minutes) as described above. Is instantaneously brought to the L level by the diode 35.

Therefore, the control device 2 controls the card reader / writer 1 so as to return the magnetic card as it is when the other party is calling, and protects the user's disadvantages during the call. , The balance calculation result is controlled to be written in the magnetic card and carried out.

Further, when the power supply from the battery power source 5 to the power line 13 is cut off during a call due to train vibration, poor maintenance, or the like, discharge from 12 is started as described above, and therefore detection is performed during this discharge time. The signal is held at H level,
You can talk for a few minutes. When the discharge from the capacitor 12 is reduced to some extent, the voltage of the input line 17 is lowered, the input voltage of the voltage detector 31 becomes 5 V or less, and the detection signal becomes L level.

Since the resistor 37 is connected to the output line 33 via the diode 35, the time constant of the output line 33 (almost determined by the capacitor 36 of the resistor 37) becomes small, and the output line 33 quickly becomes L level.

At this time, the power supply to the card reader / liner 1 and the control device 2 is continued.

Therefore, like the above, the control device 2 causes the magnetic card to write the balance so as not to be a disadvantage to the user, and causes the card to be carried out.

In addition, when the power supply to the power supply line 13 becomes unstable due to poor connection or the battery power supply 5 ages and the input line 32 of the voltage detector 31 fluctuates around 5V, the output of the voltage detector 31 becomes H level. Between the L level and the L level, the fluctuation is stabilized by the capacitor 36, so that the control device 2 maintains the communication state.

Even if the capacitor 12 of the charging / discharging circuit 11 is defective and short-circuiting continues, the resistance values of the semiconductor resistance elements 15A and 15B become large due to self-heating, so that the short-circuit current is small. The load on the battery power source 5 is also reduced.

<Other embodiments of the present invention> In the above embodiment, two semiconductor resistance elements 15A and 15B were used in parallel, but one or more may be used depending on the charging current or the like. Good.

Further, the charging period and the like can be freely set by using a semiconductor resistance element having a temperature change characteristic according to the device used.

Further, the power supply device of the present invention can be applied not only to a telephone device installed in a moving body such as a train, an automobile, or a ship, which has a battery as a power source, but also to various devices having severe power supply conditions.

<Effects of the Present Invention> As described above, the power supply device of the present invention uses a small semiconductor resistance element that rapidly changes from low resistance to high resistance at a predetermined temperature to rapidly charge a capacitor from a DC power supply When the power supply is cut off, the charged electric charge is discharged to the DC / DC converter, a predetermined voltage is supplied to the load device for a predetermined time, and the input voltage of this DC / DC converter drops to the predetermined voltage. Detected by.

For this reason, it is not necessary to use a large fixed resistor for charging as in the conventional case, the power supply device can be formed in an extremely small size, and it can be housed in a small device. It can be installed easily.

Also, even if there is a short circuit accident of the capacitor of the charge and discharge circuit,
Short-circuit current can be reduced by self-heating of the semiconductor resistance element, resulting in burnout, battery over-discharge, power source breakdown, etc.
This has the effect of preventing subsequent accidents and allowing passengers to avoid feeling uneasy to users. Further, for the same reason, there is an advantage that a fuse for preventing overcurrent is unnecessary.

In addition, even if the output voltage from the charge / discharge circuit is somewhat unstable, the load device is supplied with the power converted to a predetermined voltage by the DC / DC converter, so even if the load device is vulnerable to power fluctuations, the capacitor It is possible to stably operate for a predetermined time without increasing the capacity of the.

In addition, even if the DC power supply line such as the battery is cut off or short-circuited regardless of the operation of the equipment, the voltage drop is detected within the voltage range in which the load device can move.
By using this detection signal, it is possible to prevent the user from being damaged.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment used for a telephone device in a train of the present invention, FIG. 2 is a circuit diagram showing a main part of a power supply device 2, and FIG. 3 is a resistance value of semiconductor resistance elements 15A and 15B. FIG. 4 is a diagram showing the temperature dependence characteristic of FIG. 4, and FIG. 1 ... Card reader / writer, 2 ... Control device, 3 ...
Telephone, 4 ... Wireless device, 5 ... Battery power, 6 ...
Power supply, 11 ... Charging / discharging circuit, 12 ... Capacitor, 14A,
14B ... Diode, 15A, 15B ... Semiconductor resistance element, 16A,
16B ... Diode, 19 ... DC / DC converter, 23 ... Capacitor, 25 ... Voltage detection circuit, 31 ... Voltage detector, 35
……diode.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Kenichi Kimura 1-1-6 Uchisaiwaicho, Chiyoda-ku, Tokyo Nihon Telegraph and Telephone Corporation (72) Koichi Yajima 1-1-6 Uchisaiwaicho, Chiyoda-ku, Tokyo Nihon Telegraph and Telephone Co., Ltd. (56) Bibliography Showa 58-193738 (JP, U) Showa 48-57620 (JP, U)

Claims (1)

[Scope of utility model registration request] 1. A DC power supply such as a battery, a DC / DC converter that converts the DC voltage into a predetermined voltage and supplies the load device, and a resistance value suddenly changes from a low resistance to a high resistance when the temperature exceeds a predetermined temperature. Via the semiconductor resistor element, the DC power source is rapidly charged into a large-capacity capacitor, and the charge stored in the capacitor is applied to the DC when the DC power source is cut off or the voltage drops.
A charge / discharge circuit that discharges to the / DC converter and maintains the operation of the load device for a predetermined time, the input voltage of the DC / DC converter, the rated voltage of the DC power supply and the DC / DC converter to the load device. A power supply device, comprising: a voltage detection circuit for detecting whether or not the voltage has dropped below a predetermined voltage between the minimum voltage required to supply the predetermined voltage.