JP7109864B2 - power supply - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply device that corrects a voltage drop that occurs between a power supply section and a load.

For example, an electric bed equipped with a motor that consumes a relatively large amount of power as a load is equipped with a power supply unit that converts commercial AC power from the outside into DC power. and other loads (see, for example, Patent Document 1).

When the power consumption in the load is large, the current value flowing through the load becomes large. Then, the amount of voltage drop in the transmission line supplying power to the load increases. Therefore, the voltage applied to the load will drop. In such a case, a booster circuit is provided immediately before the load to boost the amount of the voltage drop and apply it to the load as the original voltage (see, for example, Patent Document 2).

Japanese Patent Application Laid-Open No. 2001-46443 (Claim 1) JP 2003-303317 A (paragraph 0029)

In the booster circuit provided to compensate for the voltage drop in the transmission line as described above, the operation may not be stable unless the input voltage is lower than the output voltage. When the power consumption of the load is large, that is, when the current flowing through the transmission line is large and the voltage drop is large, no problem occurs because the voltage input to the booster circuit is lower than the output voltage. However, when the power consumption of the load is reduced, the amount of voltage drop is reduced, so that the voltage input to the booster circuit approaches the output voltage, resulting in unstable operation of the booster circuit. In such a case, it is conceivable to lower the input voltage of the booster circuit when the load is low by providing a voltage dividing resistor on the input side of the booster circuit. Since the amount of voltage drop under load increases further, it cannot be adopted.

Therefore, in view of the above problems, the present invention is capable of appropriately lowering the input voltage of a booster circuit even when the load is low, and prevents the amount of voltage drop from increasing unnecessarily when the load is high. An object of the present invention is to provide a power supply device that does not require a power supply.

In order to solve the above problems, a power supply device according to the present invention includes a power supply unit that outputs DC power of a predetermined voltage, and a load that is driven by the DC power output from the power supply unit. A power supply device having a booster circuit that boosts the voltage of the DC power that has dropped while being transmitted from the power supply unit to the predetermined voltage, and is located between and in the immediate vicinity of the load. A diode is connected in the forward direction to a position where the power is input to the booster circuit, and DC power that has been dropped by the forward voltage drop (Vf) due to the diode is input to the booster circuit. .

If only a resistor is provided, the voltage will drop in proportion to the value of the energized current. Therefore, the amount of voltage drop increases during high load. On the other hand, in the case of a diode, only the forward voltage drop drops in the forward direction regardless of the current value. Therefore, regardless of the magnitude of the load, it is possible to input a constant voltage to the booster circuit in a state of being lowered.

As is clear from the above description, according to the present invention, the input voltage of the booster circuit is lowered by the forward voltage drop of the diode, so that the input voltage of the booster circuit can be made lower than the output voltage even at low load. In addition, the effect of the voltage drop due to the provision of the diode can be reduced as much as possible when the load is high.

A diagram showing the configuration of an embodiment of the present invention.

Referring to FIG. 1, EB is an electric bed. The electric bed EB is provided with a power supply section 1, to which AC power of 100 volts is supplied from an external AC power supply PS. The power supply unit 1 rectifies the AC power of 100 volts and outputs DC power of a predetermined voltage. In this embodiment, it is assumed that 24 volt DC power is output.

This electric bed EB is provided with three motors 4 as loads. A power transmission line 11 is provided for transmitting drive power from the power supply unit 1 to these three motors 4 . However, when all the three motors 4 operate at the same time, the current value flowing through the transmission line 11 increases and the voltage drop in the transmission line 11 increases, so that each motor 4 cannot be supplied with 24 volt DC power. Therefore, the step-up circuit 2 is provided, and the dropped voltage is stepped up to 24 volts by the step-up circuit 2 and supplied to each motor 4 . A drive circuit 41 is connected to a remote controller (not shown) and controls the direction and speed of rotation of each motor 4 . Reference numeral 5 denotes a light load such as a communication circuit with the remote controller (not shown) and LED illumination.

The booster circuit 2 does not operate stably unless the input voltage is lower than the output voltage of 24 volts. In this embodiment, the input voltage must be at least 0.6 volts below 24 volts. However, when the power consumption of the motor 4 as a whole is small, such as when only one of the three motors 4 operates and its rotational speed is low, the current value of the transmission line 11 increases. As a result, the amount of voltage drop in the transmission line 11 becomes small, and the 24-volt power output from the power supply unit 1 may be input to the booster circuit 2 with almost no voltage drop. At this time, if the input voltage of the booster circuit 2 is close to 24 volts, the operation of the booster circuit 2 becomes unstable as described above.

Therefore, the diode 3 is attached in the forward direction immediately before the DC power is input from the transmission line 11 to the booster circuit 2 . A forward voltage drop (Vf) is generated in the diode 3 when a current flows in the forward direction, and the voltage of the DC power supplied from the transmission line 11 is dropped by this Vf amount. However, since the Vf in the diode 3 is constant regardless of the magnitude of the current value, the voltage can be input to the booster circuit 2 with a voltage dropped by a constant value, that is, Vf, regardless of the magnitude of the load. Generally, this Vf is about 0.6 volts, so even if there is almost no voltage drop in the transmission line 11 when the load is low, the input voltage of the booster circuit 2 can be kept below the specified voltage. Also, when the voltage drop in the transmission line 11 is large under high load, the voltage drop in the diode 3 is only Vf, so the voltage drop in the transmission line 11 is much larger than Vf. , the influence of the voltage drop due to the diode 3 can be reduced as much as possible. In addition, depending on the type of the diode 3, if the amount of voltage drop at low load is insufficient with Vf of one diode, a plurality of diodes may be connected in series.

It should be noted that the present invention is not limited to the embodiments described above, and various modifications may be made without departing from the gist of the present invention.

REFERENCE SIGNS LIST 1 power supply unit 2 booster circuit 3 diode 4 motor 11 transmission line

Claims (1)

A power supply unit that outputs DC power of a predetermined voltage, and a load that is driven by the DC power output by the power supply unit. In a power supply device having a booster circuit that boosts the voltage of DC power that has dropped in voltage during transmission to the predetermined voltage, a diode is placed in order at a position where the power transmitted from the power supply unit is input to the booster circuit. A power supply device characterized in that the voltage is dropped by a forward voltage drop (Vf) due to the diode and the DC power is input to the booster circuit.

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