JP2012095458A - Power supply unit and power tool having the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power supply unit capable of notifying a worker of a drop in a battery voltage of a battery pack.SOLUTION: The power supply unit 1 includes a switching circuit 26 that converts DC power from a battery pack 4 into AC power for output; a voltage detection section 21 that detects a battery voltage of the battery pack 4; and a microcomputer 29 that presets an output effective value of the switching circuit 26 based on the detected voltage and controls so that electric power with the preset output effective value is output from the switching circuit 26.

Description

  The present invention relates to a power supply device including an inverter and a power tool including the power supply device.

  Conventionally, there has been known a power supply device that has a battery pack that stores power from an external power source and an inverter that converts DC power stored in the battery pack into AC power, and supplies power to an AC-driven electric tool. Yes. (For example, see Patent Document 1)

JP 2009-278832 A

  In the above power supply device, electric power having a constant output effective value can be supplied to the electric tool until it is determined that overdischarge occurs. However, in the case of overdischarge, the power supply is suddenly stopped, resulting in inconvenience in work.

  An object of this invention is to provide the power supply device and electric tool which can alert | report the fall of the battery voltage of a battery pack to an operator.

  In order to achieve the above object, a power supply device of the present invention includes an inverter unit that converts DC power from a battery pack into AC power and outputs the voltage, a voltage detection unit that detects a battery voltage of the battery pack, and the detection A setting unit that sets an output effective value of the inverter unit based on the voltage that has been set, and a control unit that performs control such that electric power having the set output effective value is output from the inverter unit. It is characterized by.

  According to such a configuration, since the effective output value of the inverter unit is set based on the detected voltage, the operator can recognize the battery voltage of the battery pack during work.

  Moreover, it is preferable that the said setting part reduces the said output effective value according to the fall of the said battery voltage.

  According to such a configuration, since the power of the power tool connected to the power supply device is also reduced by reducing the output effective value, the operator can easily recognize the reduction in the battery voltage of the battery pack. Become.

  A first switching element for converting DC power from the battery pack into AC power; a booster circuit unit for boosting the converted power; and DC power by rectifying and smoothing the boosted power And a rectifying / smoothing circuit unit that outputs to the inverter unit, and the control unit changes the switching duty of the first switching element so that the power having the set output effective value is It is preferable to perform control that is output from the inverter unit.

  The inverter unit includes a plurality of second switching elements for outputting the smoothed power as AC power, and the control unit changes a switching duty of the second switching element. Thus, it is preferable to perform control such that electric power having the set effective output value is output from the inverter unit.

  According to such a configuration, simply by controlling the switching element according to the battery voltage, the power of the electric tool connected to the power supply device is also reduced, and the operator easily recognizes the decrease in the battery voltage of the battery pack. It becomes possible.

  Moreover, it is preferable that the said control part stops supply of the electric power from the said battery pack to the said inverter part, when the voltage of the said battery pack detected by the said voltage detection part is smaller than predetermined value.

  Moreover, it is preferable that the said control part stops supply of the electric power from the said battery pack to the said inverter part, when an overdischarge detection signal is input from the said battery pack.

  According to such a configuration, it is possible to suppress the battery pack from being over-discharged, and it is possible to suppress a decrease in the life of the battery pack.

  ADVANTAGE OF THE INVENTION According to this invention, the power supply device which can alert | report a fall of the battery voltage of a battery pack to an operator can be provided.

The circuit diagram of the power supply device by this invention. Explanatory drawing of control of the output effective value by this invention. The flowchart about control of the output effective value by this invention.

  An embodiment of a power supply device (inverter device) 1 according to the present invention will be described with reference to FIGS. 1 to 3.

  FIG. 1 is a circuit diagram of the power supply device 1. In the present embodiment, the power supply device 1 includes an inverter 2 and an electric tool body 3. When the trigger switch 31 a of the electric tool body 3 is operated, the inverter 2 is supplied from the battery pack 4. The direct current power is converted into alternating current power by the inverter 2 and supplied to the brushless motor 32 via the rectification three-phase conversion circuit 31 of the electric power tool body 3. The inverter 2, the electric tool main body 3, and the battery pack 4 are detachable, but the following description will be made assuming that each is connected.

  The inverter 2 includes a battery voltage detection unit 21, a power supply unit 22, a booster circuit (boost circuit unit) 23, a rectification / smoothing circuit (rectification smoothing circuit unit) 24, a boost voltage detection unit 25, and a switching circuit (inverter). Unit) 26, a current detection resistor 27, a PWM signal output unit 28, and a microcomputer 29 serving as a control unit.

  The battery voltage detection unit 21 includes resistors 211 and 212 connected in series to each other, detects the voltage from the battery pack 4, and outputs the voltage to the microcomputer 29 as a divided voltage from the connection point between the resistors 211 and 212. . The battery pack 4 shown in FIG. 1 has four lithium battery cells of 3.6 V / cell connected in series and outputs a rated voltage of 14.4 V.

  The power supply unit 22 includes a power switch 221 and a constant voltage circuit 222 connected in series between the battery pack 4 and the microcomputer 29. The constant voltage circuit 222 includes a three-terminal regulator 222a and oscillation prevention capacitors 222b and 222c. When the power switch 221 is turned on by the user, the voltage from the battery pack 4 is set to a predetermined DC voltage (for example, 5V) and supplied as drive power to the microcomputer 29. When the power switch 221 is turned off, the driving power is not supplied to the microcomputer 29, so that the entire inverter 2 is turned off.

  The booster circuit 23 includes a transformer 231 and an FET 232 serving as a first switching element. The primary side of the transformer 231 is connected in series between the battery pack 4 and GND, and the FET 232 is disposed between the primary side of the transformer 231 and GND. The gate of the FET 232 is connected to the microcomputer 29, and the FET 232 is turned on / off by a first PWM signal from the microcomputer 29, which will be described later. As a result, the DC power supplied from the battery pack 4 to the primary side of the transformer 231 Is converted to AC power.

  On the secondary side of the transformer 231, a rectification / smoothing circuit 24, a boosted voltage detection unit 25, a switching circuit 26, and a current detection resistor 27 are connected.

  The rectifying / smoothing circuit 24 includes diodes 241 and 242 and a capacitor 243. With these, the AC power boosted by the transformer 231 is rectified and smoothed and output as DC power.

  The boosted voltage detection unit 25 includes resistors 251 and 252 connected in series with each other, detects a DC boosted voltage (for example, 140 V) output from the rectifying / smoothing circuit 24, and detects a connection point between the resistors. The divided voltage is output to the microcomputer 29.

  The switching circuit 26 is composed of four FETs 261-264 serving as second switching elements. The FETs 261 and 262 connected in series and the FETs 263 and 264 connected in series are connected to the rectifying / smoothing circuit 24. Connected in parallel to the output terminal. Specifically, the drain of the FET 261 is connected to the output terminal (plus side) of the rectifying / smoothing circuit 24, and the source of the FET 261 is connected to the drain of the FET 262. The drain of the FET 263 is connected to the output terminal (plus side) of the rectification / smoothing circuit 24, and the source of the FET 263 is connected to the drain of the FET 264.

  Furthermore, the source of the FET 261 and the drain of the FET 262, the source of the FET 263, and the drain of the FET 264 are connected to output terminals 265 and 266, respectively. The output terminals 265 and 266 are connected to the brushless motor 32 of the electric power tool body 3 via the rectification three-phase conversion circuit 31. The gate of the FET 261-264 is connected to the PWM signal output unit 28, and the FET 261-264 is turned on / off by a second PWM signal from the PWM signal output unit 28, which will be described later. The DC power output from 24 is converted into AC power and supplied to the electric power tool body 3 (motor 32).

  Note that a commutator motor may be used instead of the brushless motor 32. In this case, the trigger switch is connected in series between the motor and the output terminal 265 or 266.

  The current detection resistor 27 is connected in series between the source of the FET 262 and the source of the FET 264 and GND, and the terminal on the high voltage side of the current detection resistor 27 is connected to the microcomputer 29. With such a configuration, the current detection resistor 27 detects the current flowing through the AC motor 32 and outputs it to the microcomputer 29 as a voltage.

  The microcomputer 29 performs feedback control based on the boosted voltage detected by the boosted voltage detection unit 25. Specifically, a first PWM signal for outputting AC power having a target effective voltage from the secondary side of the transformer 231 is output to the gate of the FET 232, and the FET 232 is turned on / off. Further, the microcomputer 29 outputs a second PWM signal for supplying the set power to the AC motor 32 to the PWM signal output unit 28. The PWM signal output unit 28 outputs the second PWM signal output from the microcomputer 29 to the gate of the FET 261-264 to turn on / off the FET 261-264. Specifically, the microcomputer 29 performs a second operation for alternately turning on and off a set of FET 261 and FET 264 (hereinafter referred to as a first set) and a set of FET 262 and FET 263 (hereinafter referred to as a second set) at a duty of 100%. The PWM signal is output.

  Further, the microcomputer 29 of the present embodiment changes the target effective voltage value based on the voltage of the battery pack 4 detected by the battery voltage detection unit 21. The change of the effective voltage value will be described later.

  Further, the microcomputer 29 determines overdischarge of the battery pack 4 based on the battery voltage detected by the battery voltage detection unit 21. Specifically, when the battery voltage detected by the battery voltage detection unit 21 is equal to or lower than a predetermined value, it is determined that the battery pack 4 is over-discharged, and the second for turning off the FETs 232 and 261-264 1 PWM signal and 2nd PWM signal are output. Further, the battery pack 4 includes a protection IC and a microcomputer therein, and has a function of detecting overdischarge by itself and outputting an overdischarge signal to the microcomputer 29. The microcomputer 29 is overdischarged from the signal terminal LD. Even when the signal is received, the first PWM signal and the second PWM signal for turning off the FETs 232 and 261-264 are output. With such a configuration, it is possible to prevent the life of the battery pack 4 from being shortened.

  Next, the control of the effective output value by the microcomputer 29 according to the present embodiment will be described with reference to FIGS.

  3 is a flowchart when the power switch 221 is turned on while the battery pack 4 is attached to the inverter 2, or when the battery pack 4 is attached to the inverter 2 while the power switch 221 is turned on. Start. When the power switch 221 is turned on, a voltage is supplied from the voltage of the battery pack 4 to the constant voltage circuit 222, so that the driving voltage of the microcomputer 29 is generated and the microcomputer 29 operates.

  First, the microcomputer 28 outputs the first PWM signal to the FET 232 and operates the booster circuit 23 (S200). Based on the boosted voltage detected by the boosted voltage detector 25, the microcomputer 242 It is determined whether the boosted voltage (detected voltage) is larger than a target output effective value (for example, 140 V) (S201). When the detected voltage is larger than the target output effective value (S201: YES), the first PWM signal with a reduced duty ratio is output to the gate of the FET 232 (S203), and the detected voltage is lower than the target output effective value. (S201: NO), the first PWM signal with the increased duty ratio is output to the gate of the FET 232 (S202).

  As described above, first, after feedback control of the boosted voltage (the voltage of the capacitor 243), the battery voltage detection unit 21 detects the voltage of the battery pack 4 (S204), and based on the battery voltage, The target output effective value is changed (S205).

  Subsequently, it is determined whether or not the battery voltage detected by the battery voltage detector 21 is smaller than a predetermined overdischarge voltage (S206). If the voltage is smaller than the predetermined overdischarge voltage (S206: YES), it is determined that the battery pack 4 is in an overdischarge state, the first PWM signal and the second PWM signal are stopped, and the booster circuit 23 and the switching circuit are stopped. 26 is stopped (S207). Thereby, the supply of power from the battery pack 4 is stopped.

  On the other hand, if the battery voltage is equal to or higher than the predetermined overdischarge voltage (S206: NO), it is determined whether or not an overdischarge signal is input from the battery pack 4 via the LD terminal (S208). When the overdischarge signal is input (S208: YES), the operation of the booster circuit 23 and the switching circuit 26 is stopped in the same manner as when the battery voltage is smaller than the predetermined overdischarge voltage (S206: YES) ( S207). If no overdischarge signal has been input (S208: NO), the process returns to S200.

  In the conventional power supply device, since the target output effective value is not changed in S205, power having a constant output effective value is always supplied to the electric tool body 3 regardless of the change in the voltage of the battery pack 4. However, in the conventional power supply device, when it was determined that the overdischarge occurred in S206 and S208, the supply to the electric power tool body 3 was suddenly stopped, which caused inconvenience in work.

  However, in the power supply device 1 according to the present embodiment, the target output effective value is changed based on the battery voltage after performing feedback control of the boosted voltage of the booster circuit 23 (capacitor 243) in S201 to S203 (S205). That is, in S204, the voltage of the battery pack 4 is detected by the battery voltage detection unit 21, and the FET 232 or the FET 261-264 is subjected to switching control according to the detected battery voltage.

  The battery pack 4 has a rated voltage of 14.4 V, in which four lithium battery cells of 3.6 V / cell are connected, but the battery voltage rises to about 16 V when fully charged by charging. When the electric tool such as the lawn mower 3 is driven in this fully charged state, the FET 232 is controlled to be switched by the first PWM signal so that the voltage of the capacitor 243 becomes, for example, the target value 140V, and the inverter device 2 The switching of the FETs 261-264 is controlled with a duty of 100% by the second PWM signal so that the output of the (switching circuit 26) becomes 100 V AC.

  Thereafter, the electric power of the battery pack 4 is consumed by the motor 3 and the load such as the grass to be cut, and the battery voltage gradually decreases from 16 V when fully charged as shown in FIG. In the present embodiment, the FET 232 and the FETs 261 to 264 are subjected to switching control so that the output of the inverter 2 becomes 100 V AC until the battery voltage reaches 10 V.

  When the lawn mowing operation further proceeds and the battery voltage drops below 10 V, the microcomputer 29 changes the switching control of the FET 232 or FET 261-264 according to the battery voltage.

  Specifically, the FET 232 is subjected to switching control so that the voltage of the capacitor 243 becomes 140 V as in the case of full charge. On the other hand, as shown in FIG. 2, the four FETs of the switching circuit 26 are subjected to switching control so as to decrease the output of the inverter 2 from 100V to 60V in response to a decrease in battery voltage.

  In this embodiment, the output of the inverter circuit 26 is set according to the battery voltage in S205 (the FETs 261-264 are controlled), but not only the FETs 261-264 of the switching circuit 26, but also the duty of the FET 232, That is, the target value of the capacitor voltage may be lowered according to the battery voltage, or only the FET 232 may be changed.

  Therefore, if the electric power tool body 3 is continuously used, as shown in FIG. 2, the output from the inverter 2 also decreases (100 V to 60 V) in response to the battery voltage decrease (16 V to 8 V). The power of the electric power tool main body 3 will decrease. Then, the operator can recognize the decrease in the battery voltage of the battery pack 4 due to the decrease in the power of the electric power tool body 3, and can quickly determine whether to continue the operation.

  As shown in FIG. 2, when the battery voltage detection unit 21 detects that the battery voltage of the battery pack 4 has reached 8 V (2 V per cell), the booster circuit 23 and the inverter circuit 26 are stopped as described above. Thus, overdischarge of the battery pack 4 can be prevented, and a decrease in battery life can be suppressed.

  The power supply device of the present invention is not limited to the above-described embodiment, and various modifications and improvements can be made within the scope described in the claims.

  For example, in the above embodiment, the target output effective value of the inverter 2 is changed based on the battery voltage detected by the battery voltage detection unit 21, but is changed based on the boost voltage detected by the boost voltage detection unit 25. May be. In this case, by keeping the duty of the FET 232 constant, the boost voltage detection unit 25 detects that the boost voltage (the voltage of the capacitor 243) decreases according to the battery voltage, and according to the result, the inverter circuit 26 What is necessary is just to control FET.

  In the above embodiment, feedback control is performed so that power having a target output effective value is output from the inverter 2 by changing the first PWM signal. However, the second PWM signal is changed. It may be done by.

  Further, the output of the inverter 2 has been described as being from 100 V to 60 V, but the present invention is not limited to this, and the output range may be widened or narrowed as long as the operator can grasp the state of charge of the battery pack.

  Moreover, in the said embodiment, although the battery pack 4 connected to the inverter 2 was demonstrated as a 14.4V lithium battery pack, it consists of a different kind of battery pack, for example, a lithium battery, a nickel cadmium battery, or a nickel hydride battery. Any of the battery packs may be connectable, or a plurality of battery packs having different battery voltages may be connectable. In this case, the battery pack is provided with identification means (for example, a resistor) for identifying the battery voltage and type, and the microcomputer 29 determines the connected battery pack based on information from the resistor, and boosts the voltage according to the battery pack. If the boosting operation of the circuit unit 23 is controlled, various battery packs can be used and workability can be improved. Moreover, you may change the output range of the inverter 2 according to the connected battery pack.

  In the flowchart of FIG. 3, the overdischarge state is determined in S206 and S208. However, the determination may be made at any time.

  DESCRIPTION OF SYMBOLS 1: Power supply device, 2: Inverter, 3: Electric tool, 4: Battery pack, 21: Battery voltage detection part, 22: Microcomputer power supply part, 23: Boosting circuit, 24: Rectification / smoothing circuit, 25: Boosting voltage detection part , 26: switching circuit, 27: current detection resistor, 28: PWM signal output unit, 29: microcomputer

Claims (7)

An inverter unit that converts DC power from the battery pack into AC power and outputs it;
A voltage detector for detecting a battery voltage of the battery pack;
A setting unit for setting an effective output value of the inverter unit based on the detected voltage;
A control unit that performs control such that electric power having the set output effective value is output from the inverter unit;
A power supply device comprising:   The power supply apparatus according to claim 1, wherein the setting unit decreases the output effective value in accordance with a decrease in the battery voltage. A first switching element for converting DC power from the battery pack into AC power;
A booster circuit unit that boosts the converted power;
A rectifying / smoothing circuit unit that rectifies and smoothes the boosted power and outputs the DC power to the inverter unit;
Further comprising
The control unit performs control such that electric power having the set effective output value is output from the inverter unit by changing a switching duty of the first switching element. Item 3. The power supply device according to Item 1 or 2. The inverter unit includes a plurality of second switching elements for outputting the smoothed power as AC power,
The control unit performs control such that electric power having the set effective output value is output from the inverter unit by changing a switching duty of the second switching element. Item 4. The power supply device according to any one of Items 1 to 3.   The control unit, when the voltage of the battery pack detected by the voltage detection unit is smaller than a predetermined value, stops the supply of power from the battery pack to the inverter unit. 5. The power supply device according to any one of 4.   The said control part stops supply of the electric power from the said battery pack to the said inverter part, when an overdischarge detection signal is input from the said battery pack, The any one of Claim 1 thru | or 5 characterized by the above-mentioned. The power supply device according to item.   A motor and a trigger switch for instructing power supply from the battery pack to the motor are provided, and can be connected to the power supply device according to any one of claims 1 to 6. Electric tool.

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