JP2003047170A - Power supply circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power supply circuit, which prevents an excessive burden falling on a charging circuit before an auxiliary battery is mounted, and reduces consumption of the auxiliary battery inside a memory card. SOLUTION: The power supply circuit is provided with a main power supply part 1 which supplies electric power; a main circuit 8 which makes a desired process; an SRAM card 3 which involves a memory 31 to hold desired data and a battery 32 to hold the memory 31; an auxiliary power supply 5 which involves a battery B1; a connector CN2 to which the auxiliary power supply 5 is set; a regulator 6 to which power is supplied from the auxiliary power supply 5 and which supplies the SRAM card 3 with power; a charging circuit 4 which charges the auxiliary power supply 5; a detection part 10 which detects whether or not the auxiliary power supply is connected to the connector CN2; and a changeover part 20 which changes over connection of a power supply route between the auxiliary power supply 5 and the SRAM card 3 connection of the power supply route between the auxiliary power supply 5 and the charging circuit 4, and connection between the auxiliary power supply 5 and the main power supply part 1, according to the result of detection by the detection part 10.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply circuit for supplying power from a main power supply to a main circuit, for example, a power supply circuit for supplying power from an auxiliary power supply to the main circuit when the main power supply is off.

[0002]

2. Description of the Related Art Conventionally, for example, a power supply circuit that supplies power from a main power supply to a main circuit for performing desired processing, and supplies power to the main circuit from a removable and rechargeable auxiliary power supply when the main power supply is off. Are known.

In the above power supply circuit, when the main power supply is on,
A charging circuit that receives power from the main power supply and charges the auxiliary power supply is provided. In the above-mentioned charging circuit, generally, a weak current is supplied to the auxiliary power source to perform charging.

[0004]

In the above-mentioned conventional power supply circuit, for example, the main power supply and the main circuit are connected, the auxiliary power supply is connected to the main circuit, and the charging circuit is connected to the auxiliary power supply.

Therefore, in the above-described conventional power supply circuit, when the auxiliary power supply is not mounted, the charging circuit flows the charging current to the main circuit, the charging circuit flows more current than the allowable amount, and the charging circuit operates. There was a problem of possible damage.

In order to solve the above-mentioned problems, conventionally, a microcomputer (also referred to as a microcomputer) detects attachment of an auxiliary power source, outputs a control signal to a switching unit, and shuts off a charging circuit and a main circuit at the switching unit. I was letting it.

However, in the above-mentioned method, there is a time lag in switching the charging circuit and the main circuit from each other, and a charging current exceeding the allowable amount of the charging circuit flows from the charging circuit to the main circuit.
There is a problem that the charging circuit may be damaged.

By the way, there is known a power supply circuit having a removable memory card including a memory for recording data processed in a main circuit and an auxiliary battery for holding the data stored in the memory.

In the power supply circuit described above, power is normally supplied from the main power supply to the main circuit and the memory card. In addition, at the time of power failure, power is supplied from the auxiliary battery in the memory card to the memory and data is retained.

However, in the case of long-term operation, there is a problem that the auxiliary battery is exhausted, power may not be supplied to the memory, and data may not be retained. Therefore, the auxiliary battery in the memory card should be used as much as possible. There is a desire not to do it.

An object of the present invention is to provide a power supply device which does not burden the charging circuit even when the auxiliary power supply is not attached. Another object of the present invention is to provide a power supply circuit capable of extending the life of the auxiliary battery in the memory card even when the main power supply is off.

[0012]

In order to achieve the above object, the power supply circuit of the present invention comprises a main power supply unit for supplying electric power,
A main circuit that is connected to the main power supply unit and functions by receiving power supply, an auxiliary power supply including an auxiliary battery that supplies power to the main circuit when the main power supply unit is off, and the auxiliary power supply are connected. A power supply circuit having an auxiliary power supply set section and a charging circuit for charging the auxiliary battery supplied with electric power from the main power supply section, wherein whether or not the auxiliary power supply is set in the auxiliary power supply set section A detection unit for detecting and a switching unit for cutting off the power supply path between at least the charging circuit and the main circuit according to the detection result of the detection unit are included.

Preferably, the switching unit is the detection unit,
When it is detected that the auxiliary power source is set in the auxiliary power source setting unit, the charging circuit, the auxiliary power source, and the main circuit are connected, and the auxiliary power source is not set in the auxiliary power source setting unit. In this case, the power supply path between the charging circuit and the main circuit is cut off.

Further, preferably, the detection unit includes a node connected to the auxiliary power supply set unit, and the auxiliary power supply set unit, when the auxiliary power supply is set in the auxiliary power supply set unit, , Connecting the node to a reference potential.

Further, preferably, the detection unit detects whether or not the auxiliary power supply is connected to the auxiliary power supply setting unit based on the potential of the node.

Further, preferably, the auxiliary power source has a plurality of connection terminals connected to the auxiliary power source setting section, and at least one of the connection terminals is set when the auxiliary power source setting section is set. It is connected to the reference potential.

Further, preferably, the control circuit includes a control circuit for outputting a control signal to the detection section according to the potential of the node, and the detection section controls the control signal output from the control circuit and the potential of the node. In response to this, a second control signal is output to the switching unit, and the switching unit connects or disconnects the auxiliary power source and the power supply path of the main circuit according to the second control signal.

[0018] Preferably, the control circuit outputs a quick charge control signal when desired, and the switching unit performs the charge when the quick charge control signal is output from the control circuit. A circuit and the power supply path of the auxiliary power supply are cut off, and the auxiliary power supply and the main power supply unit are connected.

Preferably, the control circuit has a second circuit connected to the main power source section and the auxiliary power source and having a desired function, and the control circuit is predetermined when the main power source is off. A cutoff control signal is output after a predetermined time, and when the cutoff signal is output from the control circuit, the switching unit cuts off the power supply path between the auxiliary power supply and the main circuit, and the auxiliary power supply and the first circuit. Connect the two circuits.

Preferably, the switching section has a regulator for converting the electric power supplied from the auxiliary power source into a predetermined voltage and outputting the voltage to the second circuit, and the switching section is provided with the cutoff signal from the control circuit. Is output, the connection between the auxiliary power supply and the main circuit is cut off, and the auxiliary power supply and the regulator are connected.

Further, preferably, the second circuit has at least a memory for storing data processed by the main circuit and a second auxiliary power supply for holding the memory.

Further, it is preferable to have a converter for converting the voltage of the main power source section or the auxiliary power source into a predetermined voltage and outputting it to at least the main circuit.

According to the present invention having the above structure, for example, electric power is supplied from the main power supply unit to the converter, and electric power is supplied from the converter to the main circuit and the second circuit.

When the auxiliary power supply is set in the auxiliary power supply set section, the node connected to the auxiliary power supply set section is connected to the reference potential through the connection terminal of the auxiliary power supply.

Then, in the control circuit, a control signal is output to the detection unit according to the potential of the node and the state of the main power supply unit. Then, in the detection unit, the second control signal is output to the switching unit according to the potential of the node and the control signal.

Then, in the switching section, the connection of the charging circuit, the auxiliary power source, the main circuit, and the second circuit is switched according to the second control signal.

For example, when the auxiliary power source is connected to the auxiliary power source setting unit, the switching unit connects the auxiliary power source to the main circuit via the charging circuit, the auxiliary power source, and the converter.
When the auxiliary power source is not connected to the auxiliary power source setting unit, the switching unit shuts off the power supply paths of the charging circuit and the converter.

Further, in the control circuit, when the main power supply is off, a cutoff signal is output after a predetermined time. And
When the cutoff control signal is output, the switching unit cuts off the power supply path between the auxiliary power supply and the main circuit, and connects the auxiliary power supply to the second circuit via the regulator.

When the control circuit outputs the quick charge control signal, the switching section shuts off the power supply path between the charging circuit and the auxiliary power source and connects the auxiliary power source and the main power source section.

[0030]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of a power supply circuit of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing a power supply circuit according to an embodiment of the present invention.

As shown in FIG. 1, the power supply circuit 100 includes a main power supply unit 1, a DC-DC converter 2, an SRAM card 3, a charging circuit 4, an auxiliary power supply 5, a regulator 6, and a microcomputer as a control circuit. To tell)
7, main circuit 8, detection unit 10, switching unit 20, charging switching unit 3
0, a connector CN2 that is an auxiliary power supply setting unit, a resistor R1
.About.5, diodes D1 to 6, and capacitor C1.

The main power supply unit 1 is a supply source for supplying voltage and current to each device and has a predetermined voltage, for example, a DC voltage 1
Supply 5 volts.

The outline of the main power source section 1 is the charging circuit 4
Is connected inline. The outline of the main power supply unit 1 is connected to the anode of the diode D3, and the cathode of the diode D3 is connected to the in-line of the DC-DC converter 2. The outline of the main power supply unit 1 is connected to the anode of the diode D1, the cathode of the diode D1 is connected to one end of the resistor R3, and the other end of the resistor R3 is connected to the 12th terminal of the relay RLY2. The outline of the main power supply unit 1 is connected to one end of the resistor R1, the other end of the resistor R1 is connected to the 10th terminal of the microcomputer 7, the other end of the resistor R1 is connected to one end of the resistor R2, and the resistor R2. The other end of is grounded.

The DC-DC converter 2 has a function of converting a DC voltage supplied from the main power supply unit 1 into a predetermined DC voltage, for example, a DC voltage of 15V into a DC voltage of 5V. Further, the DC-DC converter 2 converts the DC voltage supplied from the auxiliary power supply 5 into a predetermined DC voltage, for example, 9.
It has the function of converting 6 volts to 5 volts DC.
Then, the DC-DC converter 2 converts the converted DC voltage power into the main circuit 8 and SR having a desired function.
Supply to the AM card 3.

The in-line of the DC-DC converter 2 is
Connected to the cathode of the diode D3,
Is connected to the outline of the main power supply unit 1. Further, the outline 1 of the DC-DC converter 2 is connected to a circuit (not shown) having a desired function. Also,
The outline 1 of the DC-DC converter 2 is connected to the anode of the diode D5, and the cathode of the diode D5 is connected to the SRAM card 3. Also, DC-
From the outline 2 of the DC converter 2, the power supply H-V
DD is output.

The SRAM card 3 includes, for example, the main circuit 8
It has a function of storing data input by. For example, the SRAM card 3 is a memory 3 that stores data.
1 and a battery 32 for backing up the memory 31 are formed in a removable card.

The memory 31 is, for example, a memory in which data can be written, rewritten, and read, and an SRAM (Stati) that stores data as long as power is supplied.
cRandom Access Memory). The backup battery 32 has, for example, a voltage of 3
It is a V primary battery.

Further, the SRAM card 3 has a function of holding the data in the memory 31 by using the supplied power when a predetermined voltage, for example, a voltage of 3 V or more is supplied from the outside.

The SRAM card 3 supplies power from the backup battery 32 when no power is supplied from the outside and when the supplied voltage is lower than a predetermined voltage, for example, 3V. It has a function of holding data in the memory 31.

The charging circuit 4 is a circuit for charging the auxiliary power supply 5, which is supplied with electric power of the DC voltage 15V of the main power supply unit 1 and boosts it to a DC voltage of about 18V to relay RLY.
2, and power is supplied to the auxiliary power supply 5 via the relay RLY1. For example, the charging circuit 4 is a circuit that performs trickle charging and supplies a minute current, for example, a current of several tens mA to the auxiliary power supply 5 to perform charging.

The in-line of the charging circuit 4 is connected to the outline of the main power source section 1. The outline of the charging circuit 4 is connected to the anode of the diode D2, the cathode of the diode D2 is connected to one end of the resistor R4,
The other end of the resistor R4 is connected to the tenth terminal of the relay RLY2.

Next, the auxiliary power source 5 will be described.

The auxiliary power source 5 holds data in the SRAM card 3 when the main power source unit 1 is off, for example.
It functions as an auxiliary power supply that supplies power to the SRAM card 3. Further, the auxiliary power supply 5 supplies power to the main circuit 8 for a desired time when the main power supply unit 1 is off.

For example, the auxiliary power source 5 is a removable battery pack containing a rechargeable secondary battery (also called an auxiliary battery) B1.

The auxiliary battery B1 has, for example, a DC voltage of 9.6.
Volt nickel-cadmium battery.

Further, the auxiliary power source 5 is connected to the connector CN2 which is an auxiliary power source setting section. The positive pole of the auxiliary battery B1 is connected to the first terminal of the connector CN2, and the negative pole is connected to the second and third terminals of the connector CN2.

The regulator 6 has a function of converting the voltage of the electric power supplied from the auxiliary power supply 5 into a desired voltage and supplying the electric power to the SRAM card 3 when the main power supply is off, for example. For example, the regulator 6 uses the auxiliary power source 5
When a DC voltage of 9.6V is supplied from the device, the voltage is converted into a predetermined voltage, for example, a DC voltage of 5V, and supplied to the SRAM card 3.

The in-line of the regulator 6 is a relay R
It is connected to the 11th terminal of LY1. The outline of the regulator 6 is connected to the anode of the diode D6, and the cathode of the diode D6 is connected to the SRAM card 3, one end of the resistor R5, the positive pole of the electric field capacitor C1, and the cathode of the diode D5. The other end of the resistor R5 is grounded, and the negative pole of the electric field capacitor C1 is grounded.

The microcomputer 7 is composed of, for example, a CPU, a RAM, a ROM, a communication interface, and the like (not shown), and is connected to the power supply circuit 100 via the connector CN1.

The microcomputer 7 is functionally
It has the functions of quick charge processing, power failure monitoring processing, battery presence / absence detection processing, and power shutdown processing.

Each function of the microcomputer 7 will be described.

The rapid battery charging process is performed, for example, by supplying electric power from the charging circuit 4 to the auxiliary power source 5 with a very small current when the main power source unit 1 is in the on state, but when the rapid charging is performed. Power is supplied from the main power supply unit 1 to the auxiliary power supply 5 for quick charging.

Specifically, the microcomputer 7 supplies a low-level voltage to the second terminal of the connector CN1 when the main power supply unit 1 is in the ON state, and will be described later connected to the second terminal of the connector CN1. The charging circuit 4 and the auxiliary power supply 5 are connected to the charging switching unit 30, and power is supplied from the charging circuit 4 to the auxiliary power supply 5 for charging.

When a switch (not shown) for quick charging is turned on, the microcomputer 7 detects that the connector CN1 has a 2
Supply a high level voltage to the terminal No.
Then, the supply source of the charging power source is switched from the charging circuit 4 to the main power source unit 1, and power is supplied from the main power source unit 1 to the auxiliary power source 5 for quick charging.

In the power failure monitoring process, the microcomputer 7 monitors the voltage input to the 10th terminal of the connector CN1. A voltage divided by the resistors R1 and R2 is supplied from the main power supply unit 1 to the 10th terminal of the connector CN1.

For example, when the main power supply unit 1 is functioning normally, a voltage higher than a predetermined voltage is supplied to the terminal 10, and when the main power supply unit 1 is in the off state, the connector CN1 No voltage is supplied to the 10th terminal.

For the battery presence / absence detection processing, the microcomputer 7 is used.
Is the auxiliary power supply 5 from the voltage of the 4th terminal of the connector CN1.
To see if is connected. For example, as will be described later, when the auxiliary power supply 5 is connected, the node a is grounded and the connector CN1 connected to the node a is connected.
The 4th terminal of becomes low level. When the auxiliary power supply 5 is not connected, the node a is held at a high level voltage, and the high level voltage is supplied to the 4th terminal of the connector CN1. In this way, the microcomputer 7 monitors the voltage of the fourth terminal of the connector CN1 to monitor the connection of the auxiliary power supply 5.

In the power-off processing, the microcomputer 7 outputs a signal for controlling the ON or OFF state of the relay RLY1 to the 6th terminal of the connector CN1 according to the state of the main power source section 1 and the connection state of the auxiliary power source 5. .

Specifically, the microcomputer 7 has a connector CN
When the voltage input to the 10th terminal of 1 is higher than a predetermined voltage, and when the 4th terminal of the connector CN1 is low level, that is, when the main power supply unit 1 is in the ON state and the auxiliary power supply 5 is connected. , A high level voltage is supplied to the sixth terminal of the connector CN1.

Further, when the microcomputer 7 detects that the main power supply unit 1 is in the off state in the above-mentioned power failure management process, the microcomputer 7 relays the relay R after a predetermined time.
A signal for turning off LY1 is output.

Specifically, for example, the microcomputer 7 sets the 6th terminal of the connector CN1 to the low level after a predetermined time when the 10th terminal of the connector CN1 is at the low level.

From the auxiliary power source 5 to the DC for the above-mentioned predetermined time.
-Main circuit 8 and SRAM via DC converter 2
It is a time for supplying power to the card 3 and causing the main circuit 8 to perform a desired shutdown process, for example, a process of storing process data in the SRAM card 3.

Then, the relay RLY1 is turned off, and power is supplied from the auxiliary power supply 5 to the SRAM card 3 via the regulator 6.

In other cases, the microcomputer 7 supplies a low level voltage to the 6th terminal of the connector CN1.

The above is the description of the microcomputer 7.

The main circuit 8 is supplied with power from the DC-DC converter 2 and the auxiliary power source 5 and performs desired processing.
Further, the main circuit 8 stores the processing result in the memory 31 of the SRAM card 3, for example.

A detachable auxiliary power source 5 is connected to the connector CN2, and each terminal of the detecting section 10 is connected to the connector CN2. As will be described later, when the auxiliary power supply 5 is connected to the connector CN2, the node a is connected to the reference potential (ground GND).

Next, the detector 10 will be described.

The detecting section 10 has a function of detecting connection of the auxiliary power supply 5. For example, the detection unit 10 includes NPN transistors Q1 and Q2, resistors R11 to R15, and a diode D1.

The collector of the transistor Q1 is the relay RL.
It is connected to the 16th terminal of Y1, the base is connected to one end of the resistor R12, and the other end of the resistor R12 is 6 of the connector CN1.
No. terminal. The base of the transistor Q1 is connected to the collector of the transistor Q2.
The emitter of the transistor Q1 is grounded.

The emitter of the transistor Q2 is grounded. The base of the transistor Q2 is connected to one end of the resistor R14, and the other end of the resistor R14 is connected to the emitter of the transistor Q2. The base of the transistor Q2 is connected to one end of the resistor R13, and the other end of the resistor R13 is connected to the second terminal of the connector CN2 via the node a.

The second terminal of the connector CN2 is connected to one end of the resistor R11 via the node a, and the other end of the resistor R11 is connected to the power supply H-VDD. Also, the connector CN
The second terminal of 2 is connected to the cathode of the diode D1 via the node a, and the anode of the diode D1 is grounded.

FIG. 2 shows the second terminal of the connector CN2, the sixth terminal of the connector CN1, and the transistor Q.
It is the figure which showed the state of 2 and Q1. Detection unit 1 described above
The operation of 0 will be described with reference to FIG.

In the detection unit 10, the auxiliary power source 5 has a connector CN.
2 is connected to the resistor R1 from the power supply H-VDD.
1, the electric charge flows to the ground GND through the second terminal and the third terminal of the connector CN2, and the node a is connected to the reference potential.

Then, the base-emitter voltage of the transistor Q2 becomes 0 volt, and the transistor Q2 is turned off.

Then, for example, when the voltage supplied from the 6th terminal of the microcomputer 7 is higher than a predetermined voltage, that is, when it is at a high level ((a) state), the charge is transferred from the base of the transistor Q1 to the emitter. Flow transistor Q
1 is turned on.

Since the power supply voltage H-VDD is applied between the collector and the emitter of the transistor Q1,
Charge flows from the collector to the emitter.

When the node a is grounded and the 6th terminal of the microcomputer 7 is lower than a predetermined voltage, that is, when it is at a low level (state (b)), the detecting unit 10 operates as described above. Since the transistor Q2 is in the off state and the 6th terminal of the microcomputer 7 is at a low level, the transistor Q1 is in the off state, and no charge flows from the collector to the emitter of the transistor Q1.

In addition, the detecting unit 10 detects the connector CN2 when the auxiliary power source 5 is not connected to the connector CN2.
Since the No. 2 terminal and the No. 3 terminal are not connected, the voltage of the node a is at a high level and the transistor Q2 is turned on.

Then, for example, when the 6th terminal of the microcomputer 7 is at high level ((c) state), electric charge flows from the collector of the transistor Q2 to the emitter. And
Since no electric charge flows into the base of the transistor Q1, the transistor Q1 is turned off. Therefore, no charge flows from the collector of the transistor Q1 to the emitter.

When the node a is at the high level and the 6th terminal of the microcomputer 7 is at the low level ((d) state), the detecting section 10 keeps the transistor Q2 in the on state and the transistor Q2 as described above. Since no electric charge flows into the base of Q1, the transistor Q1 is turned off. Therefore, similarly, no charge flows from the collector of the transistor Q1 to the emitter.

As described above, in the detecting section 10, the transistor Q2 is turned on only when the node a is the reference potential, that is, the auxiliary power source 5 is connected to the connector CN2, and the sixth terminal of the connector CN1 is at the high level. , The charge flows from the collector to the emitter. And a relay R which will be described later
Operate LY1. In other cases, the transistor Q2 is turned off and no charge flows from the collector to the emitter.

Next, the switching section 20 will be described.

The switching unit 20 has a function of switching between connecting the auxiliary power source 5 to the charging circuit 4 or the regulator 6 according to the output from the detecting unit 10. For example, the switching unit 20 includes the relay RLY1 and the diode D.
21 to D23.

The first terminal of the relay RLY1 has a power source HV.
It is connected to the cathodes of DD and diode D21. The 4th terminal of relay RLY1 is 1 of relay RLY1.
It is connected to the third terminal and the first terminal of the connector CN2. The eighth terminal of the relay RLY1 is connected to the anode of the diode D4, and the cathode of the diode D4 is DC-.
It is connected to the in-line of the DC converter 2. The terminal 9 of the relay RLY1 is connected to the terminal 7 of the relay RLY2. The inline of the regulator 6 is connected to the 11th terminal of the relay RLY1. Relay RL
The 13th terminal of Y1 is connected to the cathode of the diode D22, and the anode of the diode D22 is the diode D23.
Of the diode D23, and the cathode of the diode D23 is grounded. The anode of the diode D21 and the collector of the transistor Q1 are connected to the 16th terminal of the relay RLY1.

The operation of the switching unit 20 described above will be described.

The switching section 20 operates when the charge flows from the collector to the emitter of the transistor Q1 of the detecting section 10.
Power supply H-VDD to relay RLY1 terminal 1 and 1
Electric charges flow to the emitter of the transistor Q1 via the sixth terminal, and the relay RLY1 is turned on. When the relay RLY1 is in the ON state, the relay RLY1 4
The number 8 terminal and the number 8 terminal are connected, and the number 16 terminal and the number 9 terminal are connected.

Further, when the electric charge does not flow from the collector to the emitter of the transistor Q1 of the detection unit 10, the switching unit 20 does not flow electric charge from the 1st terminal to the 16th terminal of the relay RLY1 and the relay RLY1 is in the off state. become. When the relay RLY1 is off, the relay RL
The 4th terminal of Y1 is connected to the 6th terminal which is an open end, and the 13th terminal is connected to the 11th terminal.

The charge switching unit 30 switches between charging the auxiliary power source 5 rapidly and normal charging according to an instruction from the microcomputer 7.

Specifically, charge switching unit 30 has, for example, relay RLY2, diode D31, transistor Q3, and resistors R31 and R32.

The first terminal of the relay RLY2 is a power source HV.
It is connected to the cathodes of DD and diode D31. The sixth terminal of the relay RLY2 is connected to the anode of the diode D31 and the collector of the transistor Q3.

The terminal 7 of the relay RLY2 is the relay RL.
It is connected to the 9th terminal of Y1. Relay RLY2 1
The 0th terminal is connected to the outline of the charging circuit 4 via the resistor R4 and the diode D2. Relay RL
The 12th terminal of Y2 is connected to the outline of the main power supply unit 1 via the resistor R3 and the diode D1.

The emitter of the transistor Q3 is grounded. The base of the transistor Q3 is connected to one end of the resistor R32, and the other end of the resistor R32 is grounded. Also,
The base of the transistor Q3 is connected to one end of the resistor R31, and the other end of the resistor R31 is connected to the second terminal of the connector CN1.

The operation of the charge switching unit 30 having the above configuration will be described.

For example, the charge switching unit 30 has the connector C
When the second terminal of N1 is at low level, the base-emitter voltage of the transistor Q3 is almost 0, so that the transistor Q3 is turned off. When the transistor Q3 is in the off state, the relay RLY2 is in the off state, and the 7th terminal and the 10th terminal of the relay RLY2 are connected.

In addition, the charging switching unit 30 has a connector CN1.
When the 2nd terminal of is at high level, the transistor Q3
Charge flows from the base of the transistor to the collector,
Is turned on, charges flow from the first terminal to the sixth terminal of the relay RLY2, and the relay RLY2 is turned on.
When the relay RLY2 is turned on, the 7th terminal and the 12th terminal are connected.

The operation of the power supply circuit 100 having the above configuration will be described with reference to the flowchart of FIG. Further, here, a case where normal charging is performed, that is, a case where the second terminal of the connector CN1 of the microcomputer 7 is at a low level will be described.

First, when power is supplied to the main power source section 1 and the microcomputer 7 (ST1), the detecting section 10 detects whether or not the auxiliary power source 5 is connected (ST2). In step ST2, when the auxiliary power supply 5 is connected, the node a is connected to the reference potential. Then, in the microcomputer 7, the fourth terminal of the connector CN1 connected to the node a is monitored, and since the voltage of the node a is the reference potential, it is determined that the auxiliary power supply 5 is connected.

Then, in the microcomputer 7, the connector CN1
No. 10 terminal is monitored to determine whether the main power supply unit 1 is functioning normally (ST3).

In step ST3, the connector CN1
When the 10th terminal of No. 10 is at the high level, it is determined that the main power supply unit 1 is functioning normally, and the 6th terminal of the connector CN1 is set at the high level. Then, since the transistor Q2 is in the off state, charges flow to the base of the transistor Q1, the transistor Q1 is turned on, and the charges flow from the collector to the emitter.

Then, the relay RLY1 of the switching unit 20 is set to 1
The charge flows from the No. terminal to the No. 16 terminal, the relay RLY1 is turned on, the No. 4 terminal and the No. 8 terminal of the relay RLY1 are connected, the No. 16 terminal and the No. 9 terminal are connected, the charging circuit 4 and the auxiliary power supply. 5 is connected.

Power is supplied from the main power source unit 1 to the charging circuit 4, power is supplied from the charging circuit 4 to the first terminal of the connector CN2 via the relays RLY2 and RLY1, and power is supplied to the auxiliary power source 5. And trickle charged.

On the other hand, power is supplied from the main power source section 1 to the DC-DC converter 2, and the DC-DC converter 2 outputs S
Power is supplied to the RAM card 3 (ST4). Then, the process returns to step ST2.

In step ST2, when the auxiliary power supply 5 is not connected, the voltage of the node a between the resistor R11 and the diode D1 is maintained at the high level.
Then, charges flow from the power supply H-VDD through the resistors R11 and 13 to the emitter of the transistor Q2 and the transistor Q2 is turned on. Then, the transistor Q1 is turned off regardless of whether the 6th terminal of the connector CN1 of the microcomputer 7 is high level or low level.

In the relay RLY1 of the switching section 20, since no charge flows from the collector to the emitter of the transistor Q1, no charge flows from the 1st terminal to the 16th terminal of the relay RLY1 and the relay RLY1 is turned off. . Then, the fourth and sixth terminals of the relay RLY1 are connected, and the 16th and 11th terminals are connected. Then, the charging circuit 4 and the DC-DC converter 2 are shut off (ST5). Then, the process returns to step ST2.

In step ST3, when the main power supply unit 1 is in the off state or a power failure occurs, the microcomputer 7 performs a shutdown process.

The shutdown process will be described in detail below.

In the shutdown processing, the microcomputer 7 sets the 6th terminal of the connector CN1 to the low level after a predetermined time when the 10th terminal of the connector CN1 is at the low level.

First, power is supplied from the auxiliary power supply 5 to the main circuit 8 and the SRAM card 3 via the DC-DC converter 2 from the time when the main power supply 1 is turned off to a predetermined time. Then, in the main circuit 8, desired processing,
For example, processing such as storing data in the SRAM card 3 is performed.

Then, at a predetermined time, the connector CN
The 6th terminal of 1 is set to the low level.

Then, the transistor Q1 of the detector 10 is turned off because the base current does not flow. Then, the relay RLY1 of the switching unit 20 is turned off, the 4th terminal and the 6th terminal of the relay RLY1 are connected, and the 16th terminal and the 11th terminal are connected. Then, power is supplied from the auxiliary power supply 5 to the SRAM card 3 via the regulator 6. The SRAM card 3 holds the data in the memory 31 using the supplied power (ST6). The above is the shutdown processing.

Then, the process returns to step ST2.

As described above, according to this embodiment,
SRAM card 3 including a main power supply unit 1 for supplying electric power, a main circuit 8 for performing desired processing, a memory 31 for holding desired data, and a battery 32 for holding the memory 31.
An auxiliary power supply 5 including the battery B1, a connector CN2 to which the auxiliary power supply 5 is set, and a regulator 6 supplied with power from the auxiliary power supply 5 to supply power to the SRAM card 3.
A charging circuit 4 for charging the auxiliary power supply 5, a detection unit 10 for detecting whether or not the auxiliary power supply is connected to the connector CN2, and an auxiliary power supply 5 and an SRAM according to the detection result of the detection unit 10. Since the connection of the power supply path of the card 3, the connection of the power supply path between the auxiliary power supply 5 and the charging circuit 4, and the switching unit 20 for switching the connection between the auxiliary power supply 5 and the main power supply 1 are provided, the auxiliary power supply 5 is not connected. When installed, DC- from the charging circuit 4
It is possible to protect the charging circuit 4 without causing an excessive load to the charging circuit 4 due to the current flowing through the DC converter 2.

When the main power supply unit 1 is off, the auxiliary power supply 5 supplies power to the SRAM card 3, so that SR
It is possible to extend the life of the battery 32 without consuming the battery 32 inside the AM card 3.

The present invention is not limited to this embodiment, and various suitable modifications can be made. For example, each component is not limited to this embodiment as long as it has each function.

[0117]

As described above, according to the power supply circuit of the present invention, it is possible to protect the charging circuit without imposing an excessive load on the charging circuit when the auxiliary power supply is not mounted.

Further, when the main power supply section is off, power is supplied from the auxiliary power supply to the second circuit.
It is possible to extend the life of the second auxiliary power source without consuming the auxiliary power source.

[Brief description of drawings]

FIG. 1 is a block diagram showing an example of a power supply circuit according to an embodiment of the present invention.

FIG. 2 is a diagram showing states of main terminals and transistors of the electric circuit of FIG.

FIG. 3 is a flowchart showing an example of the operation of the power supply circuit of FIG.

[Explanation of symbols]

1 ... Main power supply 2 ... DC-DC converter 3 ... SRAM card 31 ... Memory 32 ... Battery 4 ... Charging circuit 5 ... Auxiliary power supply B1 ... Auxiliary battery 6 ... Regulator 7. Microcomputer 8 ... Main circuit 10 ... Detector 20 ... Switching unit 30 ... Charge switching unit 100 ... Power supply circuit CN1, CN2 ... Connector

Claims (11)

[Claims] 1. A main power supply unit for supplying electric power, a main circuit connected to the main power supply unit and functioning by receiving supply of electric power, and an auxiliary unit for supplying electric power to the main circuit when the main power supply unit is off. A power supply circuit having an auxiliary power supply including a battery, an auxiliary power supply set unit to which the auxiliary power supply is connected, and a charging circuit that is supplied with power from the main power supply unit to charge the auxiliary battery, wherein the auxiliary power supply A detection unit that detects whether or not is set in the auxiliary power supply setting unit, and a switching unit that shuts off at least the power supply path between the charging circuit and the main circuit according to the detection result of the detection unit. Including power supply circuit. 2. The switching unit connects the charging circuit, the auxiliary power supply, and the main circuit when the detection unit detects that the auxiliary power supply is set in the auxiliary power supply setting unit. The power supply circuit according to claim 1, wherein the power supply path between the charging circuit and the main circuit is shut off when the auxiliary power supply is not set in the auxiliary power supply setting unit. 3. The detection unit includes a node connected to the auxiliary power supply set unit, and the auxiliary power supply set unit connects the node when the auxiliary power supply is set to the auxiliary power supply set unit. The power supply circuit according to claim 1, wherein the power supply circuit is connected to a reference potential. 4. The power supply circuit according to claim 3, wherein the detection unit detects whether or not the auxiliary power supply is connected to the auxiliary power supply set unit based on the potential of the node. 5. The auxiliary power supply has a plurality of connection terminals connected to the auxiliary power supply setting section, and at least one of the connection terminals is connected to a reference potential when set in the auxiliary power supply setting section. Claim 1,
The power supply circuit according to any one of 2, 3, or 4. 6. A control circuit that outputs a control signal to the detection unit according to the potential of the node, wherein the detection unit is switched according to the control signal output from the control circuit and the potential of the node. A second control signal is output to a section, and the switching section connects or disconnects the auxiliary power source and the power supply path of the main circuit according to the second control signal. The power supply circuit according to any one. 7. The control circuit outputs a quick charge control signal when desired, and the switching unit outputs the quick charge control signal when the quick charge control signal is output from the control circuit. The power supply circuit according to any one of claims 1, 2, 3, 4, 5, or 6, wherein the power supply path of the power supply is cut off to connect the auxiliary power supply and the main power supply unit. 8. A second circuit connected to the main power source section and the auxiliary power source and having a desired function, wherein the control circuit, when the main power source is turned off, after a predetermined time. When a cutoff signal is output from the control circuit, the switching unit outputs a cutoff control signal, cuts off the power supply path between the auxiliary power supply and the main circuit, and disconnects the auxiliary power supply and the second circuit. The power supply circuit according to any one of claims 1, 2, 3, 4, 5, 6, or 7, which is connected. 9. A regulator for converting the electric power supplied from the auxiliary power source into a predetermined voltage and outputting the voltage to the second circuit, wherein the switching unit outputs the cutoff signal from the control circuit. 9. The power supply circuit according to claim 8, wherein the auxiliary power supply is disconnected from the main circuit, and the auxiliary power supply is connected to the regulator. 10. The second circuit has at least a memory for storing data processed by the main circuit, and a second auxiliary power supply for holding the memory.
Power supply circuit described in. 11. A converter for converting the voltage of the main power source section or the auxiliary power source into a predetermined voltage and outputting it to at least the main circuit.
The power supply circuit according to any one of 7, 8, 9, and 10.