JPH11262172A - Dc power supply unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To attain stable output of DC voltage, by detecting load current passing through a power tool, and switching output voltage according to the load current. SOLUTION: An output voltage setting means 30a which meets the rated voltage of a power tool is mounted inside a connector 14 fitted to one end of an output cable 12 and connectable to a DC power supply unit body 11. A load current detecting means 31 which detects load current passing through the power tool, and a control means 29 which transmits the signal of the output voltage setting means 30a in the connector 14, are provided inside the body 11. The signal of the output voltage setting means 30a is transmitted to an output voltage switching means 25 when large current does not pass through the power tool, and no noise is superimposed on the signal of the output voltage setting means 30a, thus it is possible to supply stable output voltage to the power tool.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a DC power supply which can be used for a cordless power tool (hereinafter referred to as a power tool).

[0002]

2. Description of the Related Art A conventional DC power supply is disclosed in
As described in Japanese Patent Application Publication No. 0080, an output voltage setting means is provided in an adapter plug detachably attached to one end of an output cable, and the output voltage is set by receiving a signal from the output voltage setting means. There was something.

[0003]

In the conventional DC power supply as described above, if the load current flowing through the power tool is large, noise is superimposed on the signal of the output voltage setting means and the output voltage becomes unstable. Therefore, a noise prevention circuit is required. If the output voltage setting means is provided in the adapter plug, a signal line for transmitting the signal of the output power setting means must be provided in a long output cable, and the number of lines in the output cable is three. Above
Heavy and expensive. An object of the present invention is to eliminate the above disadvantages,
An object of the present invention is to provide a DC power supply device that can output a stable DC voltage without providing a noise prevention circuit or the like.

[0004]

An object of the present invention is to provide output voltage setting means corresponding to the rated voltage of a power tool in a connector provided at the other end of an output cable and connectable to a DC power supply main body. And a control means for transmitting a signal from the output voltage setting means to the output voltage switching means in accordance with an output of the load current detection means.
In addition, an output voltage setting means corresponding to the rated voltage of the power tool is provided in a detachable adapter plug at one end of an output cable provided integrally with the DC power supply main body, and a load current flowing through the power tool is detected in the main body. This is achieved by providing a load current detecting means for performing the operation and a control means for transmitting a signal from the output voltage setting means to the output voltage switching means in accordance with the output of the load current detecting means.

[0005]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the DC power supply according to the present invention will be described with reference to FIGS. Reference numeral 11 denotes a DC power supply main body, which is connected to an AC power supply via an input cable 10 and a plug 18. 40 is a DC motor (not shown)
The power tool 1 has a terminal 1a as a voltage outlet, a latch 1b for preventing the power tool 40 from falling off, and is detachable from the battery insertion port 40a of the power tool 40. Storage battery.
Reference numeral 12 denotes an output cable for supplying a DC voltage from the DC power supply 11 to the electric tool 40, and reference numeral 13 denotes an output cable 12.
Is an adapter plug provided at one end. The adapter plug 13 has a terminal 13a which is a voltage outlet, and a latch 13b for preventing falling off from the power tool 40.
The fitting portion with the power tool 40 has the same shape as the fitting portion of the storage battery 1. A connector 14 is provided at the other end of the output cable 12 and connects the output cable 12 to the DC power supply 11.

When the plug 18 is connected to an AC power supply, the main body 11 converts the AC voltage supplied via the input cable 10 into a predetermined DC voltage and outputs the DC voltage from the terminal 13 a of the adapter plug 13 via the output cable 12. . If the adapter plug 13 is connected to the power tool 40, the power tool 40 can be used continuously.

FIG. 2 is a circuit diagram of the DC power supply device shown in FIG.
, An output voltage switching means 25, a constant voltage control circuit 26 connected to the output voltage switching means 25, and a constant voltage control via a photocoupler 27. Switching control means 2 for receiving a signal output from means 26 and outputting a control signal to switching means 22
8 and a single-chip microcomputer, etc., and are provided with arithmetic means (CPU), ROM, RAM, timer, input port, output port, A / D converter (not shown), and 5 V through a voltage dividing resistor 30b. A control unit 29 connected to a power supply and a load current detection unit 31 are provided. The output voltage switching means 25 includes a voltage dividing resistor 25a.
-25e and a transistor array 25f. The transistor array 25f receives a signal from the control means 29 and grounds one or more of the voltage dividing resistors 25b-25e. Also, as shown in FIG.
The output voltage setting means 30a is provided in the connector 14 provided at the other end of the connector. When the connector 14 is connected to the main body 11, the output voltage setting means 30a is connected to the control means 29 and the voltage dividing resistor 30b. You.

Next, a flow chart of FIG. 3 and FIGS.
The operation of the DC power supply of the present invention will be described with reference to FIG. When the plug 18 is connected to the outlet, the control means 29 starts operation (step 200) and reads the voltage obtained by dividing the voltage of the 5V power supply by the output voltage setting means 30a and the voltage dividing resistor 30b in the connector 14. This is A / D converted by an A / D converter (step 201), and is stored in a RAM as an output voltage command value Vcmd, and a signal selected by the A / D conversion value is output from a transistor array 25f of an output voltage switching means 25. (Step 202).
The transistor array 25f receives a signal from the control means 29 and selectively grounds any one of the voltage dividing resistors 25b to 25e. The output voltage switching means 25 converts a voltage obtained by dividing the output voltage by the selected voltage dividing ratio into a constant voltage. Output to control means 26.

Next, the process waits for 10 msec (step 20).
4), read the output of the load current detection means 30a, A / D convert the read output (step 205), and determine whether the output of the load current detection means 30a is 0 (step 20).
6). If the output of the load current detecting means 30a is not 0, the process proceeds to step 210, waits for 10 msec, and returns to step 205. In step 206, if the output of the load current detecting means 30a is 0, a voltage obtained by dividing the voltage of the 5V power supply by the voltage setting means 30a and the voltage dividing resistor 30b is read again and A / D converted (step 207). ,
Compare with the output voltage command value Vcmd (step 20)
8). If the A / D conversion value is the same as the output voltage command value Vcmd, the process proceeds to step 210, waits for 10 msec, and returns to step 205. In step 208, A /
If the D-converted value is different from the output voltage command value Vcmd, the connector 1 having different output voltage setting means 30a
It is determined that the power tool 4 is connected to the main body 11, that is, the power tool 40 having a different rated voltage is connected to the main body 11, and the process proceeds to step 209 to perform the same operation as steps 201 and 202 to set the output voltage.

As described above, the output voltage setting means 30a corresponding to the rated voltage of the power tool 40 is provided in the connector 14 provided at one end of the output cable 12 and connectable to the DC power supply main body 11, and the output voltage setting means 30a is provided in the main body 11. Power tool 40
Load current detecting means 31 for detecting a load current flowing through
The signal of the output voltage setting means 30a in the connector 14 is changed according to the output of the load current detecting means 31 to the output voltage switching means 2.
5, the control unit 29 transmits the signal of the output voltage setting unit 30a to the output voltage switching unit 25 when a large current does not flow through the power tool 40. A stable output voltage can be supplied to the power tool 40 without noise superimposed on the signal 30a. The output cable 12
Of the output voltage setting means 30a in the output cable 12 by providing an adapter plug 13 at one end and a connector 14 at the other end and an output voltage setting means 30a within the connector 14. Since it is not necessary to provide a signal line for transmitting the signal, the output cable 12 can be reduced in weight and inexpensive.

In the above embodiment, the output cable 12
The connector 14 having the adapter plug 13 at one end and the output voltage setting means 30a at the other end is provided integrally. However, the main body 11 and the output cable 12 are integrated, and the output cable 12 is provided with the output voltage setting means 30a. The configuration may be such that the adapter plug 13 can be attached and detached. In this case, the output voltage setting means 30 a
It is necessary to provide a signal line for transmitting the above signal, but since noise is not superimposed on the signal of the output voltage setting means 30a, a stable output voltage can be supplied to the power tool 40.

In the above embodiment, when the output value of the load current detecting means 31 is 0, the output voltage setting means 30a
Is transmitted to the output voltage switching means 25, but the signal may be transmitted when a relatively small current of 2A to 5A flows, such as during no-load rotation.

[0013]

According to the present invention, the output voltage setting means is provided in the connector provided at the other end of the output cable for connection to the main body or in the adapter plug detachably attached to the output cable provided integrally with the main body. And a load current detecting means for detecting a load current flowing through the power tool in the main body, and a control means for transmitting a signal of the output voltage setting means to the output voltage switching means according to the output of the load current detecting means. Therefore, it is possible to provide a DC power supply that supplies a stable output voltage to the power tool.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an embodiment of a DC power supply device of the present invention.

FIG. 2 is a block circuit diagram showing an embodiment of the DC power supply device of the present invention.

FIG. 3 is a flowchart illustrating an operation of the DC power supply device according to one embodiment of the present invention.

[Explanation of symbols]

11 is a DC power supply, 12 is an output cable, 13 is an adapter plug, 14 is a connector, 25 is output voltage switching means, 29 is a control circuit, 30a is output voltage setting means, 31
Is a load current detecting means, and 40 is a power tool.

Claims (3)

[Claims] An output cable having at one end an adapter plug having a fitting part having the same shape as a fitting part of a storage battery used in a cordless power tool, and at the other end a connector connectable to a DC power supply main body. A DC power supply device having output voltage switching means built-in, wherein output current setting means corresponding to a rated voltage of the power tool is provided in the connector, and load current detection for detecting a load current flowing through the power tool in the main body. And a control means for transmitting a signal of the output voltage setting means to the output voltage switching means in accordance with the output of the load current detection means. 2. A direct-current power supply having an output cable detachable with an adapter plug having at one end a fitting portion having the same shape as a fitting portion of a storage battery used in a cordless power tool, and output voltage switching means. An output voltage setting means corresponding to a rated voltage of the power tool is provided in the adapter plug, and a load current detection means for detecting a load current flowing to the power tool is provided in the main body, and an output of the load current detection means is provided. A DC power supply device provided with control means for transmitting a signal of the output voltage setting means to the output voltage switching means in response to the control signal. 3. The DC power supply device according to claim 1, wherein the output voltage setting means is a resistor.