JPH08263181A - Auxiliary power unit - Google Patents

Abstract

PURPOSE: To make a connection with an optional position on the wire between a backup power circuit and an object to be backed up and increase the capacity of a backup power source by charging a terminal voltage when a switching means is closed and discharging it to between the terminals when the switching means is open. CONSTITUTION: When a main power source 1 is ON, electric power is supplied from a power source 1 to an equipment 4 through a diode D1 . Further, a backup capacity 3 is also charged through a diode D3 up to a voltage Vc. When the main power source 1 is turned OFF, the backup power circuit operates. While the charging voltage VC of the backup capacitor 3 is higher than tire voltage VB of a backup battery 2, electric charge accumulated in the capacitor 3 is discharged through a diode D4 , so the storage contents of an SRAM, etc., are held. During this period, a voltage detecting means 5 detects a voltage Vdd being backed up by the backup capacitor 3, so an FET 6 is turned with its output and the electric charge in the capacitor 7 is used to back up the equipment 4 through a diode D5 .

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an auxiliary power supply device for increasing the capacity of a backup power supply for a RAM or CPU backed up by a battery.

[0002]

2. Description of the Related Art JP-A-1-107626 discloses a backup power supply circuit that delays the consumption of a backup battery for holding the stored contents of a memory in a device when the main power is turned off and requires less battery replacement. Described below are those described in. FIG. 3 is a configuration diagram of a conventional backup power supply circuit. In the figure, reference numeral 4 is a device including an SRAM or the like that needs to back up power when the main power supply 1 is in an off state. The device 4 includes a main power source 1 having a voltage V _S and a backup battery 2 having a voltage V _B.
And a backup capacitor 3 for charging voltage V _C ,
They are connected in parallel via backflow blocking diodes D _{1 to} D ₄ , respectively. Here, the magnitudes of the three voltages are set so that V _S and V _C are substantially the same and V _C > V _B. For example, V _S and V _C are set to 5V and V _B is set to 3.6V.

When the main power supply 1 is on, is the power supply 1
From diode D₁ Power is supplied to the device 4 via the
The RAM and the like operate normally. The capacitor 3 is also a die
Aether D₃ Through the voltage V_C Is charged up. Eventually,
For backup when the operator turns off the main power supply 1.
Battery V voltage V_B The charging voltage V of the capacitor 3_C Is high
The charge stored in the backup capacitor 3 during
Is the diode D_Four Of discharging and backing through
Thus, the operating state of the SRAM and the like is retained. In addition,
However, the backup battery 2 does not have to be consumed. To discharge
More charging voltage V_CIs the battery voltage V_B When is below, next
Backup battery 2 to diode D ₂ Through the machine
Electric power is backed up in the container 4. Capacity of capacitor 3
In order to do the above, about 1 farad
Large capacity is required.

[0004]

By the way, when the capacity of the backup capacitor is increased in order to enhance the backup capability of the conventional backup power supply circuit, the only method is to connect the capacitor to point A in FIG. However, the absolute encoder used for the robot controlled by the CPU is in the drive section of the terminal, and when it is necessary to back up the memory section of such an absolute encoder with a battery, connect a backup capacitor to the midpoint B near the encoder. When trying
The capacitor becomes a load on the backup power supply due to its own leakage, and the original purpose cannot be achieved. In view of the above problems of the prior art, the object of the present invention is to
An object of the present invention is to provide an auxiliary power supply device that can be connected to an arbitrary position of a wiring between a backup power supply circuit and a backup target and can increase the capacity of the backup power supply.

[0005]

In order to solve the above problems, the present invention provides a backup power supply circuit composed of a backup battery and a capacitor which are respectively connected in parallel to a main power supply, and an arbitrary portion of wiring between a backup target and the backup power supply circuit. Voltage detecting means for detecting the voltage across its terminals, switching means for opening and closing according to the detection output of the voltage detecting means, and switching means charged in the voltage between the terminals when the switching means is closed and in a backup state. Is a secondary power source means for discharging between the terminals when opened. Also, 2
A capacitor and a secondary battery are used as the secondary power source means.

[0006]

The output voltage of the backup power supply circuit composed of the backup battery and the capacitor connected in parallel to the main power supply is detected by the voltage detection means, and the switching means is operated by the detection output. Only when the main power source is turned on and power is supplied to the device, the secondary power source means (capacitor or secondary battery) is charged through the switching means. Then, when the main power supply is turned off and in the backup state, the backup power supply can be reinforced by discharging the charge from the secondary power supply means. Since charging is not performed in the backup state, it does not become a load of the backup power supply.

[0007]

1 is a diagram showing an electric circuit of an embodiment of the present invention. In the figure, a device (for example, an absolute encoder) 4 having an SRAM or the like that needs to back up power when the main power supply 1 is in an off state has a main power supply 1 of voltage V _S and a backup battery 2 of voltage V _B. And backup capacitor 3 for charging voltage V _C
Are connected in parallel via backflow prevention diodes D _{1 to} D ₄ . The configuration so far is the same as that of FIG. 3 and its function. Reference numeral 5 is a voltage detecting means for judging whether or not it is in a backup state based on the magnitude relation of the above three voltages, and is a voltage detecting means connected in parallel at an arbitrary position from the backup power supply circuit. As the voltage detecting means, for example, the output becomes L when the main power supply 1 is in the operating state of 4.0 V or more, and the H output is generated when the main power supply 1 is in the backup state of 4.0 V or less by the battery (FIG. 2). Has S
-80740AH or the like is used. 6 is voltage detection means 5
It is an FET element that is turned on and off by the output of the above, and has a characteristic that leakage current is small. Reference numeral 7 is an auxiliary capacitor which is charged to a voltage V _A by the main power source when the FET 6 is turned on.
When the ET6 is off, the charged charge is the diode D ₅
Is discharged to the device 4 via the. Auxiliary capacitor 7
The charging voltage V _A is substantially the same as the charging voltage V _C of the backup capacitor 3 and is set to be higher than the output voltage V _B of the backup battery. For example, V _C , V _A
Is set to 5 V which is almost the same value as V _S, and V _B is set to 3.6 V.

Next, the operation of the embodiment will be described. When the main power supply 1 is on, the diode D ₁
Power is supplied to the device 4 via the
AM and the like operate normally. The backup capacitor 3 is also charged to the voltage V _C via the diode D ₃ . Further, since the voltage detecting means 5 detects that the terminal voltage V _dd is 5 V indicating that the main power source 1 is in the operating state, the FET 6 is turned on by the output, and the auxiliary capacitor 7 is charged to V _A. Eventually, when the operator turns off the main power supply 1, the backup power supply circuit operates. While the charging voltage V _C of the backup capacitor 3 is higher than the voltage V _B of the backup battery 2, the charge stored in the capacitor 3 is discharged through the diode D ₄ , so that the stored contents of the SRAM or the like are retained. During this period, the voltage detection means 5 detects that the voltage V _dd is 4 V or less, which indicates that the backup capacitor 3 is in the backup state. Therefore, the FET 6 is turned off by the output, and the charge of the capacitor 7 is transferred to the diode D ₅ . It is used for backup to the device 4 via. Two capacitors 3
Since the backup time becomes longer due to 7 and 7, the battery 2 is not consumed as much. When the charging voltages V _C and V _A of the capacitors 3 and 7 become equal to or lower than the voltage V _{B of the} battery due to discharging, the power is then backed up from the battery 2 to the device 4 via the diode D ₂ , and the stored contents are continued. It Since the auxiliary capacitor 7 is separated from the voltage V _dd by the FET 6, it does not affect the backup power supply circuit due to leakage or the like. The resistance between the capacitor 7 and the FET 6 is for preventing the inrush of a large current.

Needless to say, the secondary battery may be replaced in place of the auxiliary capacitor 7.

[0010]

As described above, according to the present invention, the auxiliary secondary power source means is connected via the switching means to an arbitrary position of the wiring between the backup power source circuit and the backup target to increase the capacity of the backup power source. By increasing the number, it is possible to strengthen the backup power supply circuit.

[Brief description of drawings]

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

FIG. 2 is an input / output characteristic diagram of the voltage detection means of the embodiment.

FIG. 3 is a diagram showing a conventional backup power supply circuit.

[Explanation of symbols]

 1 main power supply 2 backup battery 3 backup capacitor 4 target device to back up 5 voltage detection means 6 FET element 7 auxiliary capacitor

Claims (4)

[Claims] 1. A voltage detecting means for detecting a voltage between terminals,
Auxiliary power supply comprising: switching means that opens and closes according to the detection output of the voltage detecting means; and secondary power supply means that is charged with the voltage between the terminals when the switching means is closed and discharges between the terminals when the switching means is open. apparatus. 2. A voltage detecting means for detecting a terminal voltage at an arbitrary position of a wiring connecting a backup power supply circuit and a backup target, which are composed of a backup battery and a capacitor connected in parallel to a main power supply, and the voltage. An auxiliary power supply device comprising: switching means that opens and closes according to the detection output of the detection means; and secondary power supply means that is charged with the voltage between the terminals when the switching means is closed and discharges between the terminals when the switching means is opened. 3. The auxiliary power supply device according to claim 1, wherein the secondary power supply means is a capacitor. 4. The auxiliary power supply device according to claim 1, wherein the secondary power supply means is a secondary battery.