JPH0549182A - Charger for battery set - Google Patents

Abstract

PURPOSE:To realize good charging operation through a charger from which a power supply capacitor is eliminated. CONSTITUTION:AC voltage of a commercial power supply 1 is stepped down through a transformer 5 and full-wave rectified through a rectifier 6. Thus rectified voltage is applied through an inductance 27, a circulation diode 26, and a switching element 30 onto a battery set 29 and the instantaneous voltage thereof is detected through a detecting circuit A. When the instantaneous value of the rectified voltage varies and the voltage at point (a) exceeds the internal reference voltage of an inverter 12, the rectified voltage exceeds the output voltage of the set battery 29 to cause turn ON of the element 30 thus feeding a charging current to the set battery 29. When the charging current increases the voltage across a shunt resistor 24 also increases and when it exceeds a reference voltage created by resistors 15, 16, output of a comparator 25 is activated to cause turn OFF of the element 30 thus interrupting charging current supply to the set battery 29. When the operation is repeated, a pulsating charge current flows into the set battery 29 and the pulse current is synchronized with the rectified voltage.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charging device for charging a battery pack, which is a plurality of storage batteries connected in series.

[0002]

2. Description of the Related Art To charge an assembled battery of this type, a charging device as shown in FIG. 8 is used. The commercial AC of the commercial power supply 1 is stepped down by the transformer 5, full-wave rectified by the rectifier 6, and then charged in the power supply capacitor 4. In addition to the capacitor 4, the inductance 27, the assembled battery 29, and the switching element 30 are connected in series to the output stage of the rectifier 6. In the figure, 2 is an oscillator, and the pulse output from the oscillator 2 is guided to the gate of the switching element 30 via the driver 3. That is, the switching element 30 is turned on / off by the pulse of the oscillator 2, a pulse current flows through the assembled battery 29, and the assembled battery 29 is charged.

[0003]

In the case of a switching power supply, increasing the switching frequency of the switching element allows the power supply capacitor to have a small capacity, which is advantageous in reducing the overall size. This is well known. However, in the case of the above charging device, if the switching frequency is made higher than the frequency of the output voltage (rectified voltage) of the rectifier 6 and the capacity of the capacitor 4 is made smaller, the output voltage of the capacitor 4 pulsates and the rectified voltage becomes one half wave. Then, the switching element 30 is turned on and off twice or more during a certain period, and the following problems occur in performing good charging.

For example, in the case shown in FIG. 9, the switching element 30 is turned on and off twice during the period when the rectified voltage is one half wave, and a pulse current for two pulses flows. Since the electric power charged in the capacitor 4 is sufficient during the period in which the pulse in the figure is output, the average current of the pulse is sufficiently large. However, during the period in which the pulse in the figure is output, a small amount of electric power remains in the capacitor 4 due to discharge, so the average current of the pulse of is considerably smaller than that of the pulse of. That is, if the switching frequency is increased and the capacitance of the capacitor 4 is decreased, a large charging current cannot be obtained, and as a result, the charging time becomes long.

The charging current is the sum of the output current from the rectifier circuit 6 and the output current from the capacitor 4. However, the former output current depends on the phase difference between the output frequency of the rectifier 6 and the switching frequency. Is not constant, and the charging current is not stable accordingly. In order to avoid this problem, there is no choice but to use a large-capacity capacitor 4, and in the end,
The current situation is that it is impossible to downsize the entire device.

The present invention was created under the above background, and an object of the present invention is to provide a battery pack charging device capable of performing good charging while omitting a capacitor for a power source. To provide.

[0007]

A battery charger for an assembled battery according to claim 1 of the present invention is a device for charging an assembled battery, which is a plurality of storage batteries connected in series, and comprises a transformer for stepping down commercial AC. , A rectifier circuit for full-wave or half-wave rectification of the secondary voltage of the transformer and outputting the rectified voltage to the assembled battery, a switch circuit connected between the rectifier circuit and the assembled battery, and an instantaneous value of the rectified voltage. In order to give a detection circuit for detecting and a pulse current synchronized with the rectified voltage to the assembled battery,
And a control unit for controlling on / off of the switch circuit based on the detection result of the detection circuit.

A battery charger for an assembled battery according to a second aspect of the present invention is a device for charging an assembled battery which is a plurality of storage batteries connected in series, and performs full-wave rectification or half-wave rectification of commercial alternating current and rectification. A rectifier circuit that outputs a voltage to the assembled battery, a switch circuit that is connected between the rectifier circuit and the assembled battery, a detection circuit that detects an instantaneous value of the rectified voltage, and a pulse current that is synchronized with the rectified voltage. In order to give to, a control unit for ON / OFF control of the switch circuit based on the detection result of the detection circuit, an inductance connected in series with the assembled battery, and a freewheeling diode connected in parallel with the assembled battery connected in series and the inductance. It is characterized by having.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a battery pack charging apparatus according to the present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram of the charging device.

First, the first embodiment will be described. In the figure, 1 is a commercial power supply, and the commercial AC of the commercial power supply 1 is stepped down by a transformer 5. A rectifier 6 (corresponding to a rectifier circuit) composed of a diode bridge or the like is connected to the secondary side of the transformer 5, and the secondary voltage of the transformer 5 is full-wave rectified by the rectifier 6. In addition to the detection circuit A being connected to the output terminal of the rectifier 6, the diode 23, the inductance 27, the assembled battery 29, the switching element 30 (corresponding to a switch circuit), and the shunt resistor 24 are connected in series. Furthermore, an inductance 27 and an assembled battery 29 connected in series
A free wheeling diode 26 is connected in parallel between and.
As the assembled battery 29, a battery in which a plurality of storage batteries such as NiCd batteries are connected in series is used. The diode 23 is an assembled battery.
It is provided so that the output current from 29 does not flow back to the detection circuit A side.

The detection circuit A is a circuit in which a resistor 7 and a resistor 8 are connected in series, and the instantaneous value of the rectified voltage output from the rectifier 6 is detected as a point a voltage in the figure and is output to the control circuit B. It has become.

Next, the control circuit B will be described. The point a voltage containing the information of the instantaneous value of the rectified voltage is led to the inverter 12, where it is compared with the internal reference voltage and output to the PR input terminal of the D-flip-flop 28. Also a
The point voltage is also led to a constant voltage circuit composed of a diode 9, a smoothing capacitor 10 and a Zener diode 11,
The voltage is made constant by the capacitor 10 and the Zener diode 11, is led to the CL input terminal of the D-flip-flop 28, and the comparator 25 is also connected via the voltage dividing circuit composed of the resistors 15 and 16.
Is led to the positive input of. One end of the shunt resistor 24 is connected to the negative input of the comparator 25. That is,
Reference voltage generated by resistors 15 and 16 and shunt resistor 24
The comparator 25 compares the voltage generated at both ends of the. The output of the comparator 25 is C of the D-flip-flop 28.
It is led to the P input terminal, and the output of the D-flip-flop 28 is led to the gate of the switching element 30. The diode 9 is provided to prevent the electric power charged in the smoothing capacitor 10 from flowing back to the detection circuit A side.

The operation of the charging device configured as described above will be described. Transformer 5 from commercial power supply 1 to commercial AC
When the voltage is applied to the primary side of the rectifier 6, the voltage stepped down by the transformer 5 is applied to the primary side of the rectifier 6, and a rectified voltage that is full-wave rectified by the rectifier 6 is generated. In FIG. 2, the rectified voltage is shown by a dotted line. The rectified voltage has a full-wave waveform as shown, and when this instantaneous value rises from the ground potential, the voltage at point a of the detection circuit A also rises accordingly.
When the voltage at the point a reaches or exceeds the reference voltage inside the inverter 12, the output of the inverter 12 changes from H to L, the D-flip-flop 28 is preset, and the output of the D-flip-flop 28 changes from L to H. Become. Rectified voltage is the detection circuit A
In addition, the switching element 30 is turned on under the condition that it is applied between the assembled battery 29 and the switching element 30 via the diode 23 and the inductance 27, and the rectified voltage is higher than the output voltage of the assembled battery 29. Then, the charging current flows through the assembled battery 29. When this charging current becomes large, the voltage generated across the shunt resistor 24 also becomes large. When this voltage exceeds the reference voltage generated by resistors 15 and 16, the output of comparator 25 becomes active, resulting in D
-The output of the flip-flop 28 returns from H to L, the switching element 30 is turned off, and the charging current stops flowing in the assembled battery 29.

After that, the above-described process is repeated, and as a result, the charging current flowing through the assembled battery 29 becomes a pulse current as shown in FIG. Since this pulse current is synchronized with the output voltage of the rectifier 6, that is, the rectified voltage, even if the output of the rectifier 6 does not have a capacitor for power supply as in the conventional case,
It will be very stable during the charging period. Further, although regulated by the rectifier 6 and the like, since the capacity of the commercial power supply 1 has no upper limit, a large pulse current can be taken out. In addition, inductance 27 and freewheeling diode
In addition to the fact that the pulse width is widened by 26, a very large charging current flows in the assembled battery 29, and the time required for charging can be shortened.

Although the same type of storage battery (NiCd battery in this embodiment) that constitutes the assembled battery is generally used, even if the same type of storage battery is used, the capacity, internal resistance and self-discharge will be used. There are slight variations in the characteristics such as. In the process of developing this device, it was found that when the battery pack is repeatedly charged using the conventional charging device, the following problems occur due to variations in the characteristics of the storage batteries. That is, when the battery pack is repeatedly charged, the shortage of the charge of a specific storage battery among the plurality of storage batteries becomes remarkable, and as a result, the balance of the charge amount with other storage batteries becomes large and the charge amount of the battery pack decreases. Not only that, the deterioration of the insufficiently charged storage battery is accelerated and the life of the assembled battery is shortened.

Conventionally, with a charging current of about 0.1 to 0.2 CA,
The frequency was charging with direct current or high frequency,
As in the first embodiment, the charging current is set to about 1 CA and 100
Charging at a frequency around Hz, in other words, when a large charging current is intermittently applied to the battery pack 29 to charge it,
Each storage battery that constitutes the assembled battery 29 is charged in a well-balanced manner,
It has been confirmed by experiments that even an assembled battery with advanced deterioration can be sufficiently charged, and it has been found that the above-mentioned problems can be avoided to some extent. Therefore, in addition to the above-mentioned merits, the battery pack 29 can be charged very well.

As a modified example of the first embodiment, a three-terminal regulator may be used to generate the reference voltage of the control circuit B, or it may be drawn from a separate power source, as shown in FIG. High frequency oscillator 31, AND gate
A configuration may be adopted in which 32 is added and intermittent high frequency switching is performed. A half-wave rectifier may be used as the rectifier 6.

Generally, the secondary battery is charged by supplying as much current as possible in the initial stage of charging to rapidly charge the secondary battery.
It is known that it is better to apply a small current at the end of charging to slowly charge the battery, and the same can be said when charging the assembled battery. FIG. 4 and FIG. 5 are graphs showing voltage-current waveforms at the beginning of charging and at the end of charging in the circuit of the first embodiment, respectively. At the beginning of charging shown in FIG. 4, since the difference between the peak of the rectified voltage and the output voltage of the battery pack 29 is large, the charging current rises quickly and the maximum current setting value is immediately exceeded, resulting in the waveform shown in the figure. .. On the other hand, in the final stage of charging shown in FIG. 5, the output voltage of the assembled battery 29 is high and the difference from the peak of the rectified voltage is small, so that the charging current rises slowly and it takes time to exceed the maximum current setting value. As a result, the waveform is as shown in the figure. In other words, the charging current is small at the beginning of charging, but the charging current is large at the end of charging, which is the opposite of the ideal. As a circuit that corrects this point, there is a circuit shown in FIG. 6 (referred to as a second embodiment).

The second embodiment is greatly different from the first embodiment in that, firstly, a transformer is not used, and the commercial AC of the commercial power source 1 is directly supplied to the primary side of the rectifier 6. In addition, an overvoltage protection circuit including a resistor 18, a Zener diode 19, a resistor 20, and a die auto 17 is newly provided, and thirdly, a high impedance inductance 33 is used. Explaining this overvoltage protection circuit, when the rectified voltage becomes higher than the Zener voltage of the Zener diode 19, a current flows through the Zener diode 19 and the voltage generated across the resistor 20 increases. This voltage is a D-flip flop
Since it is led to the CL input terminal of 28, the output of the D-flip-flop 28 changes from H to L, the switching element 30 is turned off, and the charging current is cut off. In addition, the voltage generated across the resistor 20 is the Zener diode.
Diode 17 to prevent voltage over 11
Is provided, and a resistor 18 is provided in order to prevent an overcurrent from flowing through the Zener diode 19.

In the case of the second embodiment described above, the commercial voltage is AC 100 V because of the transformerless configuration.
Then, the maximum value of the rectified voltage is about 140V. Most of the cases where a secondary battery is used as an assembled battery, the rating is 24 V or less, and the charging voltage of the assembled battery 29 of 12 V system is 12 V when the initial charging is low and about 16 V when the final charging is high. It is sufficiently smaller than the maximum voltage (see Fig. 7). Therefore, the rising of the charging current does not differ between the beginning and end of charging, and the magnitude of the charging current is constant,
Compared with the case of the first embodiment, it is closer to the ideal shape, which is more advantageous for good charging.

However, unlike the case of the first embodiment, since the pulse width of the charging current becomes too small, the high impedance inductance 33 and the free wheeling diode 26 are essential. Further, since the charging voltage of the assembled battery 29 may be 140 V at maximum, it is desirable to provide the overvoltage prevention circuit as in the second embodiment.

The battery charger for an assembled battery according to the present invention has a switching element as in the first and second embodiments.
A configuration may be adopted in which the timing at which the switching element 30 is turned off is not performed based on the detection result of the charging current, but is controlled by controlling the on time of the switching element 30.

[0023]

As described above, in the case of the battery pack charging apparatus according to claim 1 of the present invention, since the charging current is a pulse current and is synchronized with the rectified voltage, a capacitor is provided in the output stage of the rectifier circuit. Even without, the charging current is
It will be very stable. Moreover, since the capacity of the commercial power source is very large, a large charging current can be generated. Therefore, the time required to charge the assembled battery can be shortened and good charging can be performed. Moreover, since the capacitor can be omitted, the size, weight and cost of the device can be reduced.

In the case of the battery charger for the assembled battery according to the second aspect of the present invention, the rectified voltage is very high, a large charging current can be produced, and the same pulse current can be charged from the beginning of charging to the end of charging. Therefore, better charging can be performed as compared with the case according to claim 1. Moreover, since the transformer is not used, the size, weight and cost of the device can be reduced.

[Brief description of drawings]

FIG. 1 is a diagram for explaining a first embodiment of the present invention and is a circuit diagram of a battery pack charging device.

FIG. 2 is a graph showing a voltage / current waveform of the first embodiment.

FIG. 3 is a diagram corresponding to FIG. 1 showing a modification of the first embodiment.

FIG. 4 is a diagram corresponding to FIG. 2 in the initial stage of charging.

FIG. 5 is a diagram corresponding to FIG. 2 at the end of charging.

FIG. 6 is a diagram for explaining the second embodiment of the present invention and is a circuit diagram of a battery pack charging device.

FIG. 7 is a graph showing a voltage / current waveform of the second embodiment.

FIG. 8 is a diagram for explaining a conventional battery charger for an assembled battery, which is a diagram corresponding to FIG. 1;

FIG. 9 is a diagram corresponding to FIG. 2 for explaining a problem of the conventional device.

[Explanation of symbols]

 1 Commercial power supply 5 Transformer 6 Rectifier A Detection circuit B Control circuit 26 Freewheeling diode 27 Inductance 29 Battery pack 30 Switching element

Claims (2)

[Claims] 1. A device for charging an assembled battery, which is a plurality of storage batteries connected in series, comprising: a transformer for stepping down commercial AC; full-wave rectification or half-wave rectification of a secondary voltage of the transformer; A rectifying circuit for outputting to the assembled battery, a switch circuit connected between the rectifying circuit and the assembled battery, a detection circuit for detecting an instantaneous value of the rectified voltage, and a pulse current synchronized with the rectified voltage to the assembled battery. Therefore, a battery charger for an assembled battery, comprising: a control circuit that controls ON / OFF of a switch circuit based on a detection result of the detection circuit. 2. A device for charging an assembled battery, which is a plurality of storage batteries connected in series, wherein the rectifier circuit performs full-wave rectification or half-wave rectification of commercial alternating current and outputs a rectified voltage to the assembled battery. A switch circuit connected between the battery pack and the battery pack, a detection circuit for detecting the instantaneous value of the rectified voltage, and a pulse current synchronized with the rectified voltage to give to the battery pack.
The control circuit controls ON / OFF of the switch circuit based on the detection result of the detection circuit, an inductance connected in series with the assembled battery, and a free wheeling diode connected in parallel with the assembled battery and the inductance connected in series. An assembled battery charging device characterized by the above.