JP2010268623A - Charger - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a charger that attain reduction in cost for a noise-eliminating member, a reduction in noise voltage level (electromagnetic interference wave terminal voltage level), reduction in switching loss of a power supply part, and reduction in cost for a radiator. <P>SOLUTION: The charger is used for charging a battery of a portable power tool. The charger includes: a single transformer, including a primary-side main winding inputted with a DC voltage generated, by rectifying and smoothing a commercial AC power supply; a secondary-side main winding for outputting charging power supplied to the battery; a primary-side auxiliary winding for outputting a power to a switching control circuit that controls the main power of the charger; a secondary-side auxiliary winding for outputting a power to a secondary-side control circuit that controls the operation of the charger; and a noise suppression circuit constituted by connecting at least one capacitor and at least one resistor in series. The noise suppression circuit is connected between the positive electrode side of the primary-side auxiliary winding and the negative electrode side of the secondary-side main winding. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a charging device for charging a lithium ion battery, a nickel hydride battery, a nickel cadmium battery (hereinafter referred to as a nickel cadmium battery) and the like for electric tools.

  Conventionally, there has been proposed a single power supply type charging apparatus that eliminates the auxiliary power supply circuit and supplements the power for charging and the power for the control system with only a single power supply circuit. In such a charging device, it is possible to configure the charging device at a low cost by eliminating the auxiliary power supply circuit. In order to suppress the output voltage of the auxiliary winding that supplies power to the constant voltage circuit for driving the control system to the minimum level necessary for the control system to drive during the standby period when charging is not being performed. The voltage of the charging line can be kept lower than the battery voltage, resulting in low consumption. In addition, this control method can eliminate the inrush current that occurs when the charging device and the battery are connected, and can greatly reduce the breakage rate of connection means such as a relay.

  Such a one-power-supply type charging apparatus has a two-power-supply method because the voltage output to the auxiliary winding for supplying power to the switching control circuit varies greatly between charging and standby. In comparison, the stability as a power source is slightly inferior. In particular, at the rated output when charging is performed, the voltage output to the auxiliary winding increases, and noise propagating from the power supply device to the feed line is likely to occur. Moreover, since it is easy for noise to occur when attempting to increase the rated output of the charging device, appropriate measures against noise are required.

  Generally, in a power supply device such as a charging device, it is required to suppress or prevent the propagation of noise (noise or electromagnetic interference wave) generated due to power switching.

  Noise generated from a power supply device propagates to a power supply line connected to the power supply device, and may interfere with other electrical or electronic devices such as radios and televisions connected to other power supply lines as electromagnetic interference. Are known. Therefore, a regulation value is set for this noise in CISPR Publication 14 (International Committee on Radio Interference), which is an international standard.

  In general, as a basic means for reducing noise propagating to the feed line, a common mode choke coil including a pair of choke coils and a capacitor are inserted into the feed line as a common mode filter as shown in FIG. In addition, there is a means for further adding a common mode filter having different characteristics to form a broadband filter.

  In addition, as a typical example of means for reducing noise, a CR absorber 13 configured by connecting a capacitor and a resistor in series as shown in FIG. 2 is connected between the power switching terminals of the switching element 9 (for example, the drain of the FET, There is a means for reducing noise by connecting between the sources) and suppressing a surge voltage generated when the switching element 9 is turned off.

  There are various causes for the occurrence of noise, but one example is the pulsation of the reference potential of the apparatus. For example, in general, a charging device for charging a battery of a portable power tool places importance on portability and is not provided with a grounding terminal. Therefore, the board ground of the charging device is not grounded. Therefore, the charging device is used in a state where the substrate ground is floated with respect to the ground potential. Generally, in a charging device in which the substrate ground is not grounded to the ground, a capacitor is provided between the primary reference potential point and the secondary reference potential point of the power transformer, and the potential difference between the charging device substrate and the ground is small. The stability of the operation of the charging device is ensured to some extent. However, since the secondary side reference potential seen from the primary side of the power transformer is in a DC floating state, the waveform is based on the frequency of the commercial AC power source and the switching frequency of the charging device, and the primary side reference potential It pulsates with reference to.

JP2008-178278

  The above-mentioned common mode choke coil is generally used as an electromagnetic interference wave countermeasure element, but at the same time as a noise removal function, it constitutes a part of a commercial power supply line. The structure is such that the winding is formed through a ferrite core on a hollow bobbin wound several tens to several hundreds of times. For example, a common mode choke coil requires an inductance of 5 mH or more to eliminate noise, and when the rated output of the charging device is 70 W or more, the required inductance value and rated current value are realized, and the coil In order to adapt the temperature rise to below the standard value, a hollow ferrite core with a size of about 4 mm x 20 mm x 15 mm and a hollow bobbin with a diameter of 15 mm and a width of 15 mm with a conductor cross-sectional area of 0.13 mm2 are required. The space occupied by the common mode choke coil on the printed circuit board is about 15 mm × 20 mm. However, depending on the noise level of the apparatus, it may be necessary to use a common mode choke coil that is larger than the above-mentioned size or to use an additional stage of the common mode choke coil.

  However, if the common mode choke coil is enlarged or multistaged, there is a problem that the apparatus becomes larger and the cost becomes higher.

  Further, the above-described CR absorber has a problem of increasing the switching loss of the switching element. Therefore, there is a problem that the heat generation of the switching element is increased, and accordingly, the size of the radiator attached to the switching element is increased, and the cost is increased.

  Therefore, the object of the present invention is to reduce the cost of the noise removing member, reduce the noise voltage level (electromagnetic interference terminal voltage level), reduce the switching loss of the power supply unit, and apply to the radiator. The object is to provide a charging device with reduced cost.

  The above-described object is a charging device for charging a battery of a portable power tool, and outputs a primary main winding to which a DC voltage obtained by rectifying and smoothing a commercial AC power supply is input, and charging power to the battery A secondary side main winding that performs power, a primary side auxiliary winding that outputs power to a switching control circuit that controls the main power of the charging device, and power to a secondary side control circuit that controls the operation of the charging device And a noise suppression circuit configured by connecting at least one capacitor and at least one resistor in series, and the noise suppression circuit. Can be solved by a charging device characterized in that is connected between the positive side of the primary auxiliary winding and the negative side of the secondary main winding.

  According to the present invention, it is possible to suppress the noise level without adding a common mode choke coil to a large size or multistage by simply adding a capacitor and a resistor as a noise removing member. That is, it is possible to provide a charging device that reduces the cost of the noise removing member and reduces the noise level.

  In addition, according to the present invention, since a sufficient noise reduction effect can be obtained without using a CR absorber, the CR absorber can be eliminated, the switching loss generated by the CR absorber is eliminated, and the heat radiation attached to the switching element. The vessel can be downsized or eliminated. That is, it is possible to provide a charging device in which the switching loss of the power supply unit is reduced and the cost for the radiator is reduced.

It is a circuit diagram which shows the power supply part of the charging device which concerns on one Embodiment of this invention. It is a circuit diagram which shows an example of the power supply part of the conventional charging device. It is a characteristic view which shows the frequency characteristic of the interference wave noise terminal voltage of the charging device which concerns on one Embodiment of this invention. It is a circuit diagram which shows the charging device and battery which concern on one Embodiment of this invention. It is a wave form diagram which shows the electric potential fluctuation | variation of the secondary side reference electric potential point G2 seen from the primary side reference electric potential point G1 in the charging device which concerns on one Embodiment of this invention. It is an enlarged view of the waveform which shows the potential fluctuation of the secondary side reference potential point G2 seen from the primary side reference potential point G1 in the charging device which concerns on one Embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to FIGS. 1 to 5. Note that components having the same function are denoted by the same reference symbols throughout the drawings for describing the embodiments, and the repetitive description thereof will be omitted.

  FIG. 1 is a circuit diagram showing a power supply unit of a charging apparatus according to an embodiment of the present invention. The power supply unit includes a transformer 2, a common mode filter 3, a rectifying / smoothing circuit 4, 5, 6, 7, a switching control circuit 8, a switching element 9, circuit stabilizing capacitors 10, 11, a noise suppressing circuit 12, and a constant voltage circuit. 14 and a noise-removing capacitor 31, 32.

  The transformer 2 outputs a primary side main winding 2a to which power supplied from the commercial power source 1 is input, a secondary side main winding 2b that outputs power for charging the battery, and outputs power to the switching control circuit. Primary side auxiliary winding 2c, and secondary side auxiliary winding 2d that outputs power to the secondary side control circuit.

  The common mode filter 3 includes a common mode choke coil and a capacitor, and reduces noise (electromagnetic interference wave) propagating from the power supply unit to the feed line.

  The rectifying / smoothing circuit 4 includes a diode bridge and a capacitor, and rectifies and smoothes an alternating voltage supplied from the commercial power source 1 into a direct current.

  The rectifying / smoothing circuit 5 includes a diode and a capacitor, rectifies and smoothes the voltage induced in the primary side auxiliary winding 2c into a direct current, and outputs a voltage for driving the switching control circuit 8.

  The rectifying / smoothing circuit 6 is composed of a diode and a capacitor, rectifies and smoothes the voltage induced in the secondary main winding 2b into a direct current, and outputs a voltage for charging the battery.

  The rectifying / smoothing circuit 7 is composed of a diode and a capacitor, and rectifies and smoothes a voltage induced in the secondary auxiliary winding 2d into a direct current to drive a secondary control circuit (not shown) that controls the operation of the apparatus. Voltage to output.

  The switching control circuit 8 outputs a PWM-controlled signal for driving the switching element 9 based on a feedback signal from a secondary side control circuit (not shown).

  The switching element 9 is driven based on the PWM signal from the switching control circuit 8, and switches the voltage applied to the primary side main winding 2a.

  The constant voltage circuit 14 converts the DC voltage output from the rectifying and smoothing circuit 7 into a predetermined voltage, and supplies power to the secondary side control circuit.

  The circuit stabilization capacitors 10 and 11 stabilize the secondary-side reference potential with respect to the primary-side reference potential and prevent malfunction of the control circuit.

  Noise removing capacitors 31 and 32 generally reduce noise in a frequency band of 30 MHz to 300 MHz.

  The noise suppression circuit 12 is configured by connecting capacitors 12a, 12b and a resistor 12c in series according to the present invention, and is connected between the positive side of the primary side auxiliary winding 2c and the secondary side reference potential point G2. This further stabilizes the secondary-side reference potential with respect to the primary-side reference potential, and reduces noise in the frequency band of 0.15 MHz to 30 MHz.

  As the types of the capacitors 12a and 12b, ceramic capacitors certified by international standards are selected. By making the combined capacity of the capacitors 10 and 11 and the combined capacity of the capacitors 12a and 12b closer to each other, a higher noise reduction effect can be obtained. However, if the capacity of the capacitor is made too large, the leakage current flowing from the power supply primary side to the secondary side through these capacitors increases according to the combined capacity of the capacitors 12a, 12b, 10, 11, 31, 32. A capacity is selected that does not exceed the leakage current limit specified by the international standard. For example, in order to obtain a sufficient noise reduction effect while satisfying the specified value of the international standard, the combined capacitance of the capacitors 12a, 12b, 10, 11, 31, and 32 may be selected to be about 3300 pF.

  The resistor 12c reduces noise near the resonance frequency formed by the primary side auxiliary winding 2c and the capacitors 12a and 12b. The resistance value of the resistor 12c may be selected experimentally in the range of several tens Ω to several hundreds Ω.

FIG. 4 is a circuit diagram showing a charging device and a battery according to an embodiment of the present invention.
The charging device 100 has the single switching power supply shown in FIG. 1 as a power supply unit, and a microcomputer (hereinafter referred to as a microcomputer) 18, a constant voltage feedback circuit 19, a constant current feedback circuit 20, as a control unit, 1 power supply charging device having charging current detection resistor 21, photocoupler 22, relay drive circuit 24, battery voltage detection circuit 25, battery temperature detection circuit 26, overcharge signal detection circuit 27, battery identification circuit 28 and voltage drop circuit 30 It is.

  When the battery pack 50 is attached to the charging device 100, the state is checked by the circuits 25 to 28 and the microcomputer 18, and then the battery pack 50 is connected to the power supply unit via the relay 23 and the backflow prevention diode 29 to be charged. It is comprised so that.

  In the charging device 100, during charging standby when the battery 50 is not being charged, the output voltage of the rectifying and smoothing circuit 7 is feedback controlled to suppress the power output to a level at which the control unit can operate at a minimum, In addition, the voltage drop circuit 30 is configured to hold the output voltage of the rectifying and smoothing circuit 6 at a voltage lower than the battery voltage.

  4, the noise suppression circuit 12 is connected between the positive side of the primary side auxiliary winding 2c and the secondary side reference potential point G2 as in FIG. 1, but the secondary side connection end of the noise suppression circuit 12 is also shown in FIG. May be connected from the reference potential point G2 to the potential point G3 via the charging current detection resistor 21. In this case, it is preferable to simultaneously connect the secondary side connection ends of the circuit stabilization capacitors 10 and 11 and the noise removal capacitors 31 and 32 to the potential point G3.

  FIG. 3 is a characteristic diagram showing frequency characteristics of a noise voltage level (electromagnetic interference terminal voltage level) of the charging apparatus according to the embodiment of the present invention. The characteristic curve 15 is a characteristic curve indicating the allowable limit value of the noise frequency band defined by the international standard, the characteristic curve 16 is a characteristic curve indicating the noise voltage level when the noise control circuit 12 is provided, and the characteristic curve 17 is It is a characteristic curve which shows the noise voltage level when the noise control circuit 12 is not provided. The noise suppression circuit 12 can reduce the noise voltage level (electromagnetic interference terminal voltage level) in the frequency band of 0.15 MHz to 30 MHz, and can be improved to a lower voltage level than the standard value of the international standard.

  FIG. 5 is a waveform diagram showing potential fluctuations at the secondary-side reference potential point G2 as viewed from the primary-side reference potential point G1 in the charging apparatus according to the embodiment of the present invention. A waveform (a) is a waveform when the noise suppression circuit 12 is not provided, and a waveform (b) is a waveform when the noise suppression circuit 12 is provided. All voltage waveforms vibrate based on the period of the commercial AC power supply frequency and the period of the switching frequency. Compared with the waveform (a) when the noise suppression circuit 12 is not provided, the waveform (b) when the noise suppression circuit 12 is provided has a smaller fluctuation width of the potential fluctuation. The reason for this will be described with reference to FIG.

FIG. 6 is an enlarged view of a waveform showing the potential fluctuation of the secondary side reference potential point G2 as viewed from the primary side reference potential point G1 in the charging apparatus according to the embodiment of the present invention. The waveform (c) is a waveform when the capacitors 10 and 11 are provided and the noise suppression circuit 12 is not provided, and the waveform (d) is a waveform and a waveform when the noise suppression circuit 12 is provided without the capacitors 10 and 11 ( e) is a waveform when any of the capacitors 10 and 11 and the noise suppression circuit 12 is provided.
By canceling the waveform (c) and the waveform (d) as in the waveform (e), the fluctuation width of the potential fluctuation can be reduced.

  This indicates that the reference potential on the secondary side relative to the primary side is further stabilized by the noise suppression circuit 12. As a result, the noise voltage level in the frequency band of 0.15 MHz to 30 MHz was improved to a lower voltage level.

  FIG. 2 is a circuit diagram showing an example of a power supply unit of a conventional charging device. In this circuit, a CR absorber 13 is connected between the power switching terminals of the switching element 9. Due to the effect of the CR absorber 13, the surge voltage generated when the switching element 9 is turned off is reduced, and the noise generated by the surge voltage is reduced. However, since the heat generation of the switching element 9 is increased due to the switching loss generated by the CR absorber 13, the size of the heat sink attached to the switching element 9 increases accordingly. On the other hand, according to the present invention, the noise suppression circuit 12 of FIG. 1 can obtain a sufficient noise reduction effect even without the CR absorber 13, so that the CR absorber 13 can be eliminated, thereby reducing the switching loss. The heat radiator can be reduced in size or eliminated.

  According to the present invention as described above, it is possible to suppress the noise level without adding a common mode choke coil to a large size or multistage by simply adding a capacitor and a resistor as a noise removing member. That is, it is possible to provide a charging device that reduces the cost of the noise removing member and reduces the noise level.

  In addition, according to the present invention, since a sufficient noise reduction effect can be obtained without a CR absorber, switching loss caused by the CR absorber can be eliminated, and the radiator mounted on the switching element can be downsized or It can be lost. That is, it is possible to provide a charging device in which the switching loss of the power supply unit is reduced and the cost for the radiator is reduced.

1: AC power supply 2: Transformer 3: Common mode filter 4, 5, 6, 7: Rectification smoothing circuit 8: Switching control circuit 9: Switching element 10, 11: Capacitor for circuit stabilization 12: Noise suppression circuit 13: CR absorber 14: Constant voltage circuit 18: Microcomputer 19: Constant voltage feedback circuit 20: Constant current feedback circuit 21: Charging current detection resistor 22: Photocoupler 23: Relay 24: Relay drive circuit 25: Battery voltage detection circuit 26: Battery temperature detection circuit 27: Overcharge signal detection circuit 28: Battery identification circuit 29: Backflow prevention diode 30: Voltage drop circuit 31, 32: Noise removal capacitor 50: Battery pack 50 100: Charging device

Claims (1)

A charging device for charging a battery of a portable electric tool,
To a switching main circuit for controlling a main power of the charging device, a primary main winding for inputting a DC voltage obtained by rectifying and smoothing a commercial AC power source, a secondary main winding for outputting charging power to the battery A single transformer composed of a primary side auxiliary winding that outputs power of the secondary side and a secondary side auxiliary winding that outputs power to the secondary side control circuit that controls the operation of the charging device, and at least one A noise suppression circuit configured by connecting at least one capacitor in series with at least one capacitor, and the noise suppression circuit includes a positive electrode side of the primary auxiliary winding and a negative electrode side of the secondary main winding. A charging device characterized by being connected between.