JPS644288Y2 - - Google Patents

Description

[Detailed description of the invention] Industrial application field The present invention is applicable to electronic equipment that is driven by various power sources such as a commercial AC power supply, an external DC power supply, and a built-in battery, and has a display section that displays when the built-in battery is being charged. This relates to power supplies.

Conventional examples, configurations, and their problems The minimum conditions required when configuring a power supply device like the one described above are: (1) Regardless of whether a commercial AC power supply, an external DC power supply, or a built-in battery is used as the power supply, The charging indicator lamp does not light up.

(2) When using a built-in battery, the discharge loop must not include a diode or resistor that lowers the battery voltage.

(3) The built-in battery must not discharge when using a commercial AC power supply or external DC power supply.

In addition, the conditions for charging the built-in battery are: (4) Charging must be performed only with a commercial AC power source, and not with an external DC power source. (This is because the external DC power supply voltage is usually lower than the built-in battery voltage and cannot fully charge the built-in battery.)

On the other hand, due to the above-mentioned requirements, the charging indicator lamp naturally needs to be lit only when commercial AC power is supplied and the lamp is in a charging state. Furthermore, when the built-in battery is ready for charging,
One example of this is to prevent the built-in battery from discharging when the commercial AC power supply voltage drops or becomes zero.

Purpose of the invention The present invention provides a power supply circuit for electronic equipment that has all the above-mentioned requirements during normal operation and charging operation.

Structure of the invention In this invention, when an external DC power supply is connected, the load is driven by the external DC power supply instead of the AC power supply, and when charging the built-in battery with the AC power supply, the load is disconnected and the stabilized power supply is used. The circuit is configured to set a high output voltage, and in order to indicate when charging is in progress, a display light source is connected in parallel to the battery via a backflow prevention diode, and a resistor that is conductive during charging is connected to an output voltage detection resistor. The second diode, which is connected in parallel to set the output voltage of the stabilized power supply circuit to a high level, also has a current blocking function so that no current flows to the charge indicator lamp when the load is driven by an AC power source or a DC power source. It is characterized by

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to the accompanying drawings. In the figure, 1 is an AC power supply terminal, 2,
2' is an AC power input terminal for electronic equipment, 3 is a power transformer, 4 is a rectifier circuit, 5 is a smoothing capacitor,
6 is a series control transistor constituting a stabilized power supply circuit, 7 is an error amplification transistor, 8 is a Zener diode, 9 is an emitter resistor, 10, 11 and 12 are resistors and variable resistors for output voltage detection, 13 is a stabilization Start-up capacitor for power supply circuit,
14 is a built-in battery, 15 is a load, 16 is a charging indicator lamp connected in parallel to the battery 14, 17
18 is a current regulating resistor connected in series to the charge indicator lamp 16, and 18 is a first current direction regulating resistor inserted between one end of the resistor 17 and the negative electrode of the built-in battery 14 with its cathode facing the resistor 17. diode,
19 and 20 are second current direction regulating diodes and resistors connected in series with each other, and the variable resistor 12
The anode of the diode 19 is inserted between the connection point of the resistor 11 and the cathode of the diode 19, with the anode of the diode 19 facing the resistor 11. 21 is a first changeover switch inserted between one end of the resistor 11 and one end of the resistor 20; 22 is a switch that is switched off in conjunction with the insertion and removal of the AC power supply terminal 1 into and out of the AC power input terminals 2 and 2'; The second changeover switch switches between the first and second
Fixed contacts 22a, 22b and movable contact 22c
The first fixed contact 22a is connected to the rectifier circuit 4.
The second fixed contact 22b is connected to one side output terminal of
is connected to the negative electrode of the built-in battery 14.

Further, 23 is an external DC power supply input terminal, and as is well known, the first and second contacts 23a and 23b are in a short-circuited state when the external DC power supply is not connected.
and a third contact 23c, the second contact 23b is connected to the movable contact 22c of the second changeover switch 22, and the third contact 23c is connected to the + side output terminal of the rectifier circuit 4. . 24 is a third changeover switch that is linked to the first changeover switch 21, and has a movable contact connected to the emitter of the series control transistor 6, and an ON/OFF fixed contact connected to the first contact 23a of the external DC power input terminal 23. , is connected to one side output terminal of the rectifier circuit 4.

The operation of the above configuration will be explained next.
First, a case will be described in which the load 15 is driven by an AC power source. The AC power applied to the input terminals 2 and 2' is transformed by the power transformer 3 and rectified by the rectifier circuit 4. The + side rectified output of the rectifier circuit 4 is applied to the + side of the smoothing capacitor 5, and the - side rectified output is applied to the + side of the smoothing capacitor 5. It is applied to the first fixed contact 22a of the second changeover switch 22. In this second changeover switch 22, when the AC power supply terminal 1 is connected to the AC power input terminals 2, 2', the movable contact 22c and the first fixed contact 22a are short-circuited, contrary to the state shown in the figure. The - side rectified output is applied to the second contact 23b of the external DC power input terminal 23 through the second changeover switch 22.
At this time, since the first and second contacts 23a and 23b of the external DC power supply input terminal 23 are short-circuited as shown, the - side rectified output is applied to the third changeover switch 24. Since the third changeover switch 24 is connected to the ON contact when the load is operated by the AC power supply, the - side rectified output is transferred to the third changeover switch 24.
and reaches the negative side of the smoothing capacitor 5 through the capacitor 5.

At this time, a current flows from the starting capacitor 13 to the base of the series control transistor 6 for a predetermined time after the AC power is applied, so the series control transistor 6 is started and a voltage is generated at the output terminal of the stabilized power supply circuit. , a bias is applied to the emitter of the error amplification transistor 7. Thereafter, a stabilized DC output voltage is supplied by the steady operation of the well-known stabilized power supply circuit. At this time, since the first changeover switch 21 is connected to the ON contact, the stabilized output voltage is applied only to the load 15, and the charging indicator lamp 16 is activated because the diode 19 enters in the opposite direction to the polarity of the power supply. The light is off, and the built-in battery 14 is also affected by the movement of the diode 19 and the second fixed contact 22 of the second changeover switch 22.
Since b is open, it will not be charged. Further, even if the AC power supply voltage drops or becomes zero at this time, the built-in battery 14 will not be discharged due to the action of the diode 18.

Here, the first and third changeover switches 21 and 24
When the switch is switched to the OFF contact, the load 15 is disconnected from the stabilized power supply circuit, and the built-in battery 14 becomes the load of the stabilized power supply circuit. At this time, the first changeover switch 21 switches the diode 1 for the resistor 11.
9 and resistor 20 are connected in parallel, the voltage division ratio of the base voltage of the error amplification transistor 7 is changed, and the output voltage of the stabilized power supply circuit is set to be higher, so the output is optimal as a higher charging voltage than during normal operation. Voltage is applied to the built-in battery 14. On the other hand, this also causes the charging indicator lamp 16 to light up to indicate that charging is in progress. Of course, at this time as well, even if the AC power supply voltage drops or becomes zero, the battery 14 will not discharge due to the action of the diode 18, and the lamp 16 will not discharge.
It also doesn't light up.

Also, as mentioned above, when using AC power,
When an external DC power source is connected to the input terminal 23, the space between the first contact 23a and the second contact 23b is released,
A DC voltage is applied between the first contact 23a and the third contact 23c. Here, when the first and third changeover switches 21 and 24 are connected to the ON contact, power supply voltage is supplied to the load 15 from the external DC power supply instead of the AC power supply by the same operation as described above.

In addition, the first and third changeover switches 21 and 24 are
When switched to OFF contact, external DC power is not supplied to the stabilized power supply circuit. The load 15 is in a non-operating state, and the built-in battery 14 is also not charged.

Next, when the load 15 is driven by the built-in battery 14, since neither the AC power source nor the external DC power source is applied to the input terminals 2, 2', and 23, the negative electrode of the built-in battery 14 is connected to the first and third terminals. If the changeover switches 21 and 24 are connected to the ON contact, the second fixed contact 22b of the second changeover switch 22, the movable contact 22c, the second contact 23b of the external DC power input terminal 23, and the first It is connected to the load 15 via the contact 23a, the third changeover switch 24, the series control transistor 6, and the first changeover switch 21. At this time, the indicator lamp 16 does not light up because the diode 18 has a polarity opposite to that of the battery 14. In addition, the first and third
When the changeover switches 21 and 24 are connected to the OFF contact, the voltage of the battery 14 is not supplied to the load 15, and the load 15 does not operate.

Effects of the Invention As explained above, according to the present invention, it is possible to provide a power supply device that can satisfy all of the above-mentioned conditions. In other words, when driving a load using either an AC power supply, an external DC power supply, or a built-in battery, the indicator lamp will not be lit due to the action of the diodes 18 and 19 in either case, and when the built-in battery is used, the battery will not discharge. Since the transistor 6 is left in the loop and no other voltage-dropping elements such as diodes or resistors are included, voltage can be efficiently supplied to the load.

Further, when an AC power source or an external DC power source is used, the discharge loop of the built-in battery is cut off, so the battery will not be discharged at this time. Furthermore, it is possible to charge the battery only with an AC power supply, and at this time, the diode 19
Because the output voltage of the stabilized power supply circuit is set to be higher than during normal operation, the battery can be fully charged.

Furthermore, the charging indicator lamp can be turned on only during charging, and even if the AC power supply voltage drops or becomes zero during charging, the built-in battery will not be discharged due to the action of the diode 18.

[Brief explanation of drawings]

The figure is a circuit diagram of a power supply device according to an embodiment of the present invention. 1... AC power supply terminal, 2, 2'... AC power input terminal, 4... Rectifier circuit, 5... Smoothing capacitor, 6... Series control transistor, 7... Error amplification transistor, 10, 11, 12... Resistor group for output voltage detection, 14... Built-in battery, 15
...Load, 16...Charging indicator lamp, 18, 19
... Diode, 21, 22, 24 ... Selector switch, 23 ... External DC power supply input terminal.

Claims (1)

[Scope of utility model registration request] AC power input terminals 2, 2' and this input terminal 2,
a rectifier circuit 4 that rectifies and smoothes the AC power supply voltage applied to the AC power source 2'; a stabilizing power supply circuit that stabilizes the output voltage of the rectifier circuit 4 and supplies power to a load 15 connected to one of the output terminals; A charge display light emitting element 16 connected between the output terminals of the stabilized power supply circuit, a built-in battery 14 connected in parallel to the charge display light emitting element 16 via a discharge blocking diode 18, and the stabilized power supply A movable contact is connected to the other output terminal of the circuit, a first fixed contact is grounded, and a second fixed contact is connected to one end of the parallel circuit of the charging display light emitting element 16 and the built-in battery 14. a changeover switch 21, an output voltage detection resistor 10 constituting the stabilized power supply circuit,
The first changeover switch 21 is provided in a part of 11 and 12.
A series circuit of a second diode 19 and a resistor 20 connected in parallel via Changeover switch 22
A first fixed contact is connected to the external DC power input terminal 23 and the first contact 23a of the external DC power input terminal 23, and the first fixed contact 22a of the second changeover switch 22 and the rectifier circuit 4 are connected to each other. A second fixed contact is connected to one output terminal of the stabilized power supply circuit, a movable contact is connected to one input terminal of the stabilized power supply circuit, and a third changeover switch 24 is switched in conjunction with the first changeover switch 21. The external DC power input terminal 2 connects the first contact 23a and the second contact 23b, which are normally short-circuited, to the second changeover switch 2.
The second movable contact 22c is connected to the third movable contact 23c.
is connected to the other input terminal of the stabilized power supply circuit, and the second changeover switch 22 is connected to the second fixed contact 22b.
is connected to one electrode of the built-in battery 14,
The second diode 19 is inserted with the polarity opposite to that of the discharge blocking diode 18, and conducts when the built-in battery 14 is charged, so that the resistor 20 is connected to the output voltage in order to set the output voltage of the stabilized power supply circuit high. The first changeover switch 2 is connected in parallel to a portion of the detection resistors 10, 11, and 12.
1 movable contact and a first fixed contact are connected, a movable contact of a third changeover switch 24 interlocked with this first changeover switch 21 is connected to the first fixed contact, and a second changeover switch is connected. 22 first fixed contacts 2
2a and the movable contact 22c are connected in conjunction with the connection of the AC power supply terminal 1 to the AC power input terminals 2, 2', and the power that has passed through the rectifier circuit 4 and the stabilized power supply circuit is supplied to the external load 15. The movable contact of the first changeover switch 21 and the first fixed contact are connected, and the movable contact of the third changeover switch 24 interlocked with the first changeover switch 21 is connected. Then, connect an external DC power source to the external DC power input terminal 23, and connect the first contact 23a and the second
A second form of supplying power to the external load 15 from the external DC power supply via the stabilized power supply circuit by releasing the contact 23b between the first changeover switch 2 and the first changeover switch 2;
The first movable contact and the second fixed contact are connected, and the third
The movable contact and the second fixed contact of the changeover switch 24 are connected, and the first fixed contact 22a and the movable contact 22c of the second changeover switch 22 are connected to the AC power input terminal 2 of the AC power supply terminal 1, 2' and charges the built-in battery with the power that has passed through the rectifier circuit 4 and the stabilized power supply circuit; and the movable contact of the third changeover switch 24 and the first fixed contact, and in response to the fact that the AC power supply terminal 1 is not connected to the AC power input terminals 2, 2'. A fourth mode in which the second fixed contact 22b and the movable contact 22c of the second changeover switch 22 are connected to supply power from the built-in battery 14 to the external load 15 is freely selectable. power supply circuit.