JPH0487531A - Power supply circuit - Google Patents

Abstract

PURPOSE:To realize starting of a motor by an arrangement wherein a large current is fed to the motor in place of steady current during an interval in which a battery is not yet charged and the voltage thereof is lower than a reference voltage. CONSTITUTION:When a motor 4 is driven by AC power, output current control terminal 5 goes High if a battery 2 is not yet charged and the voltage thereof is lower than a reference voltage VR. Consequently, a large current is fed from a power supply circuit 1 and the motor 4 is started. At that time, a part of the large current is fed to the battery 2 which thereby begins to be charged. Voltage of the battery 2 increases gradually and when it exceeds a reference voltage VR, the output current control terminal 5 goes Low and the output current I of the power supply circuit 1 is switched to a steady current thus driving the motor 4 stably.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a power supply circuit that supplies a load current to a parallel-connected rechargeable power supply battery and a motor for driving a load.

[Conventional technology]

FIG. 5 shows a conventional power supply circuit. In the conventional power supply circuit, a battery 2 and a motor 4 are connected in parallel to the output end of a power supply circuit 1 that generates a DC voltage V from an AC voltage V through a switch 3. The current I output from the power supply circuit 1 is
As shown in the figure, the value I is somewhat larger than the load current of the motor 4.
o, to prevent, for example, a large current from flowing into the fully charged battery 2, resulting in overcharging, or the voltage of the battery 2 from rising too much.

[Problem to be solved by the invention]

By the way, since the load is heavy when starting the motor 4, a starting current IMS that is several times (for example, about three times) larger than when rotating is required. Motor 4 due to the output current of power supply circuit 1
When starting the motor 4, if the battery 2 is fully charged, the current IB is supplemented from the battery 4 in addition to the output current ■o of the power supply circuit 1, so it is possible to start the motor 4. If the battery 4 is uncharged, the motor 4 cannot be started because the output current Io is smaller than the current IMS for starting the motor 4.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a power supply circuit that can start a motor by supplying a current higher than the starting current to the motor when the battery is in an uncharged state.

[Means to solve the problem]

In order to solve the above-mentioned problem, the present invention provides a constant current (■) to the battery and motor connected in parallel. In the power supply circuit configured to output a voltage, the power supply circuit includes a comparison means for comparing the battery voltage with a preset reference voltage, and a large current in place of the steady current ■o only during a period when the battery voltage is equal to or lower than the reference voltage. I
and output current switching means for outputting s.

Incidentally, it is preferable to protect the power supply circuit by forcibly switching to the steady current I0 after supplying the large current (1)8 for a predetermined period of time.

Further, the steady current Is may be intermittently supplied during a period when the power supply voltage is lower than the reference voltage.

[Effect]

In the power supply circuit configured as described above, during a period when the battery is in an uncharged state and its voltage is below the reference voltage, a large current Is is supplied to the motor instead of the steady current ■o, and the motor is ready to start. Become. On the other hand, a part of the large current Is is supplied to the battery, and when the battery voltage becomes higher than the reference voltage due to charging,
The output current of the power supply circuit is switched from the large current I5 to the steady current Io.

Further, in the invention of claim 2, time measurement is started at the same time as the large current Is is output from the power supply circuit, and when a preset predetermined time is measured, the output current is forcibly changed to the steady current Io. Can be switched.

Further, in the invention according to claim 3, during the period when the battery voltage is below the reference voltage, the steady current 5 and the large current Is are alternately outputted at predetermined intervals.

〔Example〕

A power supply circuit according to the present invention will be explained using FIG. 1 and FIG. 2. FIG. 1 is a circuit configuration diagram showing an embodiment of a power supply circuit according to the present invention. Further, FIG. 2 is a time chart of output current for explaining the operation of the power supply circuit.

As shown in FIG. 1, the power supply circuit according to the present invention includes a battery 2 as a DC drive power source for a motor 4 and a power switch 3 at the output end of a power supply circuit 1 that converts an AC voltage V into a DC voltage V and outputs the converted voltage. A motor 4 as a drive source that drives a load via
are connected in parallel. Furthermore, the voltage ■ at the output end of the power supply circuit 1 and the output voltage VR of the reference voltage generation circuit 6 are
The output of the comparator 7 is input to the output current control terminal 5 of the power supply circuit 1. The power supply circuit 1 is a steady current generator whose output current I is slightly larger than the motor load current required to maintain rotation of the motor 4 by an input signal to the output current control terminal 5. and the starting current IM required to start motor 4
A current Is that is somewhat thicker than s (hereinafter referred to as large current)
It has a control circuit for switching between. In this embodiment, the output current ■ is switched to a steady current Io when the output current control terminal 5 is in a low state, and is switched to a large current Is when the output current control terminal 5 is in a high state.

In the above configuration, when the AC human power V is supplied to the power supply circuit 1 and the power switch 3 is turned on to drive the motor 4 with AC, the voltage of the battery 2 is in an uncharged state and the voltage of the battery 2 is the reference voltage , the output of the comparator 7 is at a high level, that is, the output current control terminal 5 is at a high level. As a result, a large current Is is outputted from the power supply circuit 1 as shown in FIG. 2, and the motor 4 is started. At this time, a portion of the large current I5 flows into the battery 2, and charging of the battery 2 is started. Thereafter, the voltage of the battery 2 gradually increases as it is charged, and when it exceeds the reference voltage vR at time t□, the output of the comparator 7 is at a low level, that is, the output current control terminal 5
changes to low level. As a result, the output current (2) of the power supply circuit 1 is switched to the steady current (20), and the motor 4 is driven stably.

Note that if the battery 2 is fully charged when the motor 4 is started, the voltage of the battery 2 exceeds the reference voltage vR, and the output of the comparator 7 is at a low level, that is, the output current control terminal 5 is at a low level. level, so the steady current from power supply circuit 1■
0 is output. At this time, the output current ■. In addition to this, a current ■B is supplied from the battery 4, and the motor 4 can be started due to both types of current.

By the way, for some reason when motor 4 starts, motor 4
If the power supply circuit 1 does not start or is overloaded, the large current Is will continue to flow, resulting in an excessive amount of current, and there is a risk that the power supply circuit 1 will be destroyed. Therefore, in order to prevent this, the power supply circuit 1 may be protected by outputting the large current I5 for a predetermined period of time, and then forcibly switching the output current I to the steady current Io.

FIG. 3 is a circuit configuration diagram showing an embodiment of a power supply circuit equipped with the above protection circuit.

In this figure, an AND circuit 9 is interposed between the output terminal of the comparator 7 and the output current control terminal 5 of FIG. The output signal of the timer circuit 8 is input to the input terminal. The timer circuit 8 operates at the same time as the power is turned on, and after outputting a high level signal for a preset predetermined time T,
Outputs low 1 novel signal. As a result, timer circuit 8
Since the high level signal from the comparator 7 is input to the current control terminal 5 only during the period when a high level signal is being output from the Circuit 1 can be protected.

Further, in the embodiment described above, the large current I was outputted continuously, but the power supply circuit 1 can be protected even if the large current I is outputted intermittently.

FIG. 4 is a circuit configuration diagram showing another embodiment of a power supply circuit equipped with a protection circuit.

In this figure, an oscillation circuit 10 is provided in place of the timer circuit 8 of FIG. 3. The oscillation circuit 10 operates at the same time as the power is turned on, and outputs a high level and a low level at a predetermined period t. As a result, the high level signal from the comparator 7 is input to the output current control terminal 5 only during the period when the output signal of the oscillation circuit 10 is at a high level, and the large current ls and the steady current Io are input from the power supply circuit 1 at the predetermined period. It is output repeatedly at t.

Therefore, even in the case of overload, the output current I is limited and damage to the power supply circuit 1 is prevented.

〔Effect of the invention〕

As explained above, according to the present invention, a steady current ■ is applied to the batteries and the motor connected in parallel. In a power supply circuit configured to output
During the period when the battery voltage is below the reference voltage, a large current Is greater than the starting current of the motor is output, so that the motor can be reliably started regardless of the state of charge of the battery.

In addition, the large current Is for motor starting current movement is output only for a predetermined time when the motor is started, or is output intermittently, so the amount of current is limited even when a large current flows due to overload, etc. , destruction of the power supply circuit is prevented.

[Brief explanation of drawings]

FIG. 1 is a circuit configuration diagram showing an embodiment of the power supply circuit according to the present invention, FIG. 2 is a time chart of output current to explain the operation of the power supply circuit according to the present invention, and FIG. 3 is a diagram showing a protection circuit. 4 is a circuit configuration diagram showing another embodiment of a power supply circuit equipped with a protection circuit. FIG. 5 is a circuit configuration diagram of a conventional power supply circuit. FIG. 6 is a time chart of output current for explaining the operation of a conventional power supply circuit. ■...Power supply circuit, 2...Battery, 3...Power switch, 4...Motor, 5...Output current control terminal, 6...
...Reference voltage generation circuit, 7...Comparator, 8...Timer circuit, 9...AND circuit, 10...Oscillation circuit, I
o... Steady current, Is... Large current. Patent Applicant Matsushita Electric Works Co., Ltd. Representative Patent Attorney Etsushi Kotani Patent Attorney Chief 1) Masashi Patent Attorney Takao Ito Figure Figure Figure Figure

Claims (1)

[Scope of Claims] 1. In a power supply circuit configured to output a steady current I_o to a battery and a motor connected in parallel, a comparison means for comparing the battery voltage and a preset reference voltage;
A power supply circuit comprising: output current switching means for outputting a large current I_s instead of the steady current I_o only during a period when the battery voltage is below the reference voltage. 2. In the power supply circuit according to claim 1, the large current I_
a timer means for measuring the time when s is supplied; and after the timer means measures a predetermined time, the large current I_s is converted into a steady current I
A power supply circuit characterized by comprising a protection means for forcibly switching to _o. 3. The power supply circuit according to claim 1, further comprising output current intermittent switching means for intermittently outputting the steady current I_o during a period when the battery voltage is below the reference voltage.