JP2001069690A - Power circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent delays in increase in bias voltage, even when a capacitor with a large capacitance for stabilizing the bias voltage is provided and power is supplied from a battery. SOLUTION: Presence or absence of a commercial power supply is detected from the output voltage of a regulated power supply circuit 20, which converts power from a commercial power supply into direct-current voltage Va, through a power supply detecting circuit 80. When a CPU 60 decides based on the result of the detection that commercial power supply is not provided, an analog switch 100 is opened by a switch control circuit 90 according to an instruction from the CPU 60, only if a capacitor 70 is not charged. Thus, if a switch 40 is closed and power is supplied from a battery 30, a direct-current voltage Vb of the battery 30 is supplied immediately as a bias voltage to the CPU 60, peripheral circuits and the like without charging the capacitor 70.

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 stabilizing a voltage fluctuation of a power supply supplied by a battery used as a substitute for a commercial power supply or a power failure by a charging voltage of a capacitor.

2. Description of the Related Art FIG. 3 is a block diagram showing an example of the configuration of a conventional power supply circuit. In the power supply circuit of FIG. 1, a commercial power supply (not shown) is connected to a commercial power supply input terminal 10, and an AC voltage of, for example, 100 [V] supplied from the commercial power supply via the commercial power supply input terminal 10 is: The voltage is converted by the stabilized power supply circuit 20 into a DC voltage Va for biasing the electronic circuit. A diode 51 having a cathode terminal connected to the CPU 60 is connected to an output terminal of the stabilized power supply circuit 20. One terminal of a switch 40 is connected to the positive terminal of the battery 30 having a negative electrode for supplying the DC voltage Vb and grounded, and the other terminal of the switch 40 has a cathode terminal connected to the cathode terminal of the diode 51. The connected diode 52 is connected. This switch 40
Opens and closes a connection line connecting the battery 30 and the diode 52. One electrode of a large-capacity capacitor 70 is connected to a power supply line for supplying power to the CPU 60 from the contacts of the cathode terminals of the diodes 51 and 52.
The other electrode of the capacitor 70 is grounded.

[0002] This capacitor 70 allows a previously stored charge to be stored in an electronic device such as a CPU 60 or other peripheral circuits (not shown) even when the DC voltage Va or DC voltage Vb for the bias voltage becomes unstable. The circuit is supplied to a circuit to stabilize the fluctuation of the bias voltage to the electronic circuit.

In such a power supply circuit, when power is supplied from a commercial power supply, the switch 40 is opened, and the DC voltage Va output from the stabilized power supply circuit 20 is used as a bias voltage to control the CPU 60 and peripheral circuits. To the electronic circuit.

The current output from the stabilized power supply circuit 20 flows through the diode 51 to the CPU 60, peripheral circuits, and the like, and also to the capacitor 70. Since the stabilized power supply circuit 20 has a sufficient output current capacity to supply a current to the CPU 60 and peripheral circuits even when including the charging current flowing through the capacitor 70, the bias voltage immediately reaches Va. , CPU 60 and peripheral circuits.

On the other hand, when the power supply from the commercial power supply is stopped due to a power failure or the like, or when the commercial power supply is not used from the start of the power supply circuit, the switch 40 is closed.
CPU 6 uses DC voltage Vb of battery 30 as a bias voltage.
0 and peripheral circuits.

[0006]

However, when the capacitor 70 is not charged, the DC voltage V
When b is a bias voltage, since the output current capacity of the battery 30 is usually small, if the current from the battery 30 is shunted to the capacitor 70, the CPU 60, peripheral circuits, and the like,
It takes time to charge the capacitor 70. For this reason, the bias voltage supplied to the CPU 60 and the peripheral circuits gradually increases from 0 [V] to Vb.
Since the rising voltages of the PU 60 and the peripheral circuits are different from each other, there is a problem that the order of the rising of these electronic circuits is disturbed, and the CPU 60 and the peripheral circuits may not be started normally.

The present invention has been made in view of the above, and an object of the present invention is to provide a large-capacity capacitor for stabilizing a bias voltage, and to reduce the bias voltage even when power is supplied from a battery. An object of the present invention is to provide a power supply circuit in which a rise delay is prevented.

[0008]

In order to achieve the above object, the present invention according to claim 1 provides a power supply voltage which is obtained by charging a capacitor connected to a power supply line for supplying power from a commercial power supply or a substitute battery. In a power supply circuit for stabilizing fluctuations, a power supply detecting means for detecting whether or not a commercial power supply is supplied, a switch means for opening and closing a connection line connecting a capacitor and the power supply line, and a time during which the commercial power supply charges the capacitor. Time measuring means for measuring the time, and when the supply of commercial power is detected, the connection line is closed,
Switch control means for transmitting a control signal for opening the connection line to the switch means when the commercial power is not supplied and the time required to charge the capacitor has not elapsed. That is the gist.

In the present invention, when commercial power is not supplied while the capacitor is not charged, the connection line connecting the capacitor and the power supply line is opened to interrupt the charging current to the capacitor. By doing so, even when power is supplied from a battery having a small output current capacity, the DC voltage of the battery is immediately supplied to the electronic circuit as a bias voltage.

According to a second aspect of the present invention, there is provided a power supply circuit for stabilizing voltage fluctuation of a power supply by charging voltage of a capacitor connected to a power supply line for supplying power from a commercial power supply or a substitute battery. Switch means for opening and closing a connection line connecting the power supply, a time measuring means for measuring the time during which the commercial power supply or the battery is charging the capacitor, and a resistor connected in parallel with the switch means and connected in series with the capacitor. The connection line is opened when a commercial power supply or a battery is charging the capacitor via the resistor, and the connection line is closed when the time required to charge the capacitor has elapsed. And a switch control means for transmitting a control signal to the switch means.

According to the present invention, the capacitor is charged via the resistor to prevent the bias voltage from lowering, and the connection line connecting the capacitor and the power supply line is opened during charging of the capacitor. By temporarily stopping the compensation of voltage fluctuations as a state, even when power is supplied from the battery, the DC voltage of the battery is immediately supplied to the electronic circuit as a bias voltage, and the capacitor can be charged. After the charging is completed, the connection line is closed to stabilize the voltage fluctuation by the capacitor.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a configuration of the power supply circuit according to the first embodiment of the present invention. The power supply circuit shown in the figure includes an analog switch 100 that opens and closes a connection line that connects a power supply line that supplies power to the CPU 60 and the like from the contacts of the diodes 51 and 52 and the capacitor 70, and a CPU that opens and closes the analog switch 100.
Switch control circuit 90 for controlling according to an instruction from 60
And a power supply detection circuit 80 for detecting the presence or absence of supply of commercial power from the output voltage of the stabilized power supply circuit 20 and transmitting the detection result to the CPU 60. The switch control circuit 90 has a time measurement function and a DC voltage V
The time until the charging of the capacitor 70 is completed by a (hereinafter, referred to as “charging completion time”) is stored in the memory in advance. In addition, the same components as those in FIG. 3 are denoted by the same reference numerals.

When the power supply circuit is started, the CPU 60
Determines whether commercial power is supplied based on the detection result transmitted from the power detection circuit 80.

If it is determined that commercial power is being supplied, an instruction is issued to the switch control circuit 90 to close the analog switch 100. Switch control circuit 9
When the value is 0, the analog switch 100 is closed, and the time during which the analog switch 100 is closed is measured. When the analog switch 100 is closed, a current output from the stabilized power supply circuit 20 flows into the capacitor 70, and charging of the capacitor 70 is started.

Here, when a power failure or the like occurs and the voltage from the commercial power supply is no longer detected, the CPU 60 transmits the fact to the switch control circuit 90. In the switch control circuit 90, if the charging completion time stored in the memory before the lapse of the time, the analog switch 10
0 is set to the open state, and the path of the charging current to the capacitor 70 is cut off.

By operating the power supply circuit in this manner, the switch 40 is closed and the power supply is switched from the commercial power supply to the battery 30.
In this case, the DC voltage Vb of the battery 30 is immediately supplied to the CPU 60 and peripheral devices as a bias voltage without charging the capacitor 70.

Then, after the power failure is restored, the power supply is
When the switch is switched to the commercial power supply, the switch control circuit 90 closes the analog switch 100 in accordance with an instruction from the CPU 60 to restart charging of the capacitor 70, and holds the closed state of the analog switch 100 even after the charging is completed. Thus, the voltage fluctuation of the power supply is stabilized by the capacitor 70.

If the power failure or the like has occurred after the elapse of the charging completion time of the capacitor 70 with the DC voltage Va, the switch control circuit 90 sets the analog switch 10
0 is kept closed. This is because even when the power supply is switched from the commercial power supply to the battery 30 and the DC voltage Vb is supplied to the CPU
Since the charging of the analog switch 1 has already been completed, there is no delay in raising the bias voltage.
This is for maintaining the stable compensation of the power supply fluctuation by the capacitor 70 by setting 00 to the closed state.

On the other hand, when it is determined that commercial power is not being supplied at the time of starting the power supply circuit, the CPU 60
Instructs the switch control circuit 90 to open the analog switch 100. When power is supplied from the battery 30, the analog switch 100
Is in the open state, the battery 30
Is cut off, and the DC voltage Vb of the battery 30 becomes
Immediately, the bias voltage is supplied to the CPU 60 and peripheral circuits.

Thereafter, when commercial power is supplied after switching from the battery 30, the analog switch 100 is closed to charge the capacitor 70, and the capacitor 70 stabilizes the bias voltage.

Therefore, according to the present embodiment, if the supply of power from the commercial power supply is stopped before the charging of the capacitor 70 by the commercial power supply is completed, the analog switch 100 is opened and the battery is opened. 30 DC voltage Vb
Is supplied immediately to the CPU 60 or the like as a bias voltage without charging the capacitor 70, so that a delay in the rise of the bias voltage can be prevented even when power is supplied from the battery 30.

Next, a second embodiment of the present invention will be described. FIG. 2 is a block diagram showing a configuration of the power supply circuit according to the present embodiment. The power supply circuit shown in FIG. 1 includes an analog switch 100 that opens and closes a connection line that connects a power supply line for supplying power to the CPU 60 and the like from the contacts of the diodes 51 and 52 to the capacitor 70, and an analog switch 10
It has a switch control circuit 90 for controlling the opening and closing of 0 according to an instruction from the CPU 60, and a resistor 110 connected in parallel with the analog switch 100. Resistance 110
Is a resistance value such that the bias voltage hardly decreases due to the current flowing through the capacitor 70 when the battery 30 supplies power. The switch control circuit 90 has a time measurement function and a DC voltage V.
It is assumed that there is a memory for storing a charge completion time when the capacitor 70 is charged via the resistor 110 by b. In addition, the same components as those in FIG. 3 are denoted by the same reference numerals.

When the power supply circuit is started, the CPU 60
The switch control circuit 90 issues an instruction to open the analog switch 100 whether the power is supplied from the commercial power supply or the battery 30.
And the switch control circuit 90 keeps the analog switch 100 open until the charging completion time of the capacitor 70 stored in the memory elapses.

As described above, while the analog switch 100 is in the open state, the capacitor 70 does not exhibit the function of stabilizing the bias voltage.
The battery 3 is charged by the current flowing through the battery 3 and the bias voltage hardly decreases.
0, the DC voltage Vb is
Almost immediately, it is supplied to the CPU 60 and peripheral devices as a bias voltage.

The switch control circuit 90 includes a capacitor 70
After the charging completion time has elapsed, the analog switch 10
By setting 0 to the closed state, the bias voltage is stabilized by the capacitor 70 regardless of whether the power supply is the commercial power supply or the battery 30.

Further, regardless of whether the power source is switched from the commercial power source to the battery 30 or from the battery 30 to the commercial power source, the switch control circuit 90 determines whether the charging completion time stored in the memory is sufficient. The analog switch 100 is kept open until the time has elapsed, and the analog switch 100 is closed after the charging completion time has elapsed so that the capacitor 70 stabilizes the bias voltage.

Therefore, according to the present embodiment, when charging the capacitor 70, the capacitor 70 is charged via the resistor 110 so that the bias voltage does not decrease, and the analog switch 100 is opened to set the capacitor 70. Temporarily suspends the voltage fluctuation stability compensation due to the DC voltage of the battery as a bias voltage immediately after the CPU even when power is supplied from the battery 30.
Since the voltage is supplied to the control circuit 60 and peripheral circuits, it is possible to prevent a delay in the rise of the bias voltage, to charge the capacitor 70, and to stabilize the bias voltage.

Further, in the present embodiment, the switch control circuit 90 stores the charge completion time when the battery 30 charges the capacitor 70 via the resistor 110 in the memory. The charging completion time for charging the capacitor 70 via the resistor 110 is longer for the battery 3.
Since the charging completion time is shorter than 0, the charging completion time by the commercial power source is also stored in the memory.
When the power supply detection circuit as described in the first embodiment is provided, and the CPU 60 determines that the commercial power is supplied, the switch control circuit 90 sets the analog power supply after the completion time of the charge by the commercial power has elapsed. The switch 100 may be closed.

In such a case, it is possible to eliminate a useless waiting time for waiting for the start of the voltage fluctuation stabilization compensation until the charging completion time by the battery 30 elapses even though the commercial power is supplied. it can.

[0030]

As described above, according to the present invention, when no commercial power is supplied while the capacitor is not charged, the capacitor is connected to the power line. By opening the connection line and interrupting the charging current to the capacitor, even if power is supplied by a battery with a small output current capacity, the DC voltage of the battery is immediately supplied to the electronic circuit as a bias voltage. , It is possible to prevent the delay of the rise of the bias voltage, and thus the electronic circuit can be started normally.

According to the second aspect of the present invention, the capacitor is charged via the resistor to prevent the bias voltage from lowering, and the capacitor is connected to the power supply line during charging of the capacitor. By temporarily stopping the compensation for voltage fluctuations by leaving the connection line open, even if power is supplied by the battery, the DC voltage of the battery is immediately supplied to the electronic circuit as a bias voltage, so the bias voltage by the battery Can prevent the delay of the rise of
Thus, the electronic circuit can be started normally. Further, since the capacitor can be charged by the battery, the voltage fluctuation can be stabilized by the capacitor by closing the connection line after the charging is completed.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a power supply circuit according to a first embodiment of the present invention.

FIG. 2 is a block diagram illustrating a configuration of a power supply circuit according to a second embodiment of the present invention.

FIG. 3 is a block diagram showing a configuration of a conventional power supply circuit.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Commercial power supply input terminal 20 ... Stabilized power supply circuit 30 ... Battery 40 ... Switch 51, 52 ... Diode 60 ... CPU 70 ... Capacitor 80 ... Power supply detection circuit 90 ... Switch control circuit 100 ... Analog switch 110 ... Resistance

Claims (2)

[Claims] 1. A power supply detecting means for detecting whether commercial power is supplied or not in a power supply circuit for stabilizing voltage fluctuation of a power supply by a charging voltage of a capacitor connected to a power supply line for supplying power from a commercial power supply or a substitute battery. Switch means for opening and closing a connection line connecting a capacitor and the power supply line; time measurement means for measuring a time during which the commercial power supply is charging the capacitor; and When the connection line is closed, no commercial power is supplied, and the time required to charge the capacitor has not elapsed,
And a switch control means for transmitting a control signal for opening the connection line to the switch means. 2. A power supply circuit for stabilizing voltage fluctuation of a power supply by a charging voltage of a capacitor connected to a power supply line for supplying power from a commercial power supply or a substitute battery, wherein a connection line connecting a capacitor and the power supply line is provided. A switch means for opening and closing, a time measuring means for measuring a time when the commercial power supply or the battery is charging the capacitor, a resistor connected in parallel to the switch means and connected in series to the capacitor, and a commercial power supply or the battery. When the capacitor is charged via the resistor, the connection line is opened, and when the time required to charge the capacitor elapses, the control signal for closing the connection line is set to the switch. A power supply circuit, comprising: switch control means for transmitting to the means.