JPH089566A - Battery charger mounted on electric automobile - Google Patents

Abstract

PURPOSE:To make effective use of electric energy by preventing a battery from being discharged through a resistor for voltage detection after the completion of charging. CONSTITUTION:This battery charger 10 is provided with an AC-AC converting part 86 which charges a battery 84 by converting AC voltage of an AC power source into DC voltage of a DC power source, a main switch 88 which starts the operation of the AC-DC converting part 86, a resistor 90 for voltage detection which is parallel-connected to the battery 84, and a charging control part 12 which stops the operation of the AC-DC converting part 86 on the basis of battery voltage detected by the resistor 90 for voltage detection. A sub switch 14 which closes along with the starting operation of the DC-AC converting part 86 and opens with the stopping operation of the DC-AC converting part 86 is also provided between the resistor 90 for voltage detection and the battery 84.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a battery charger installed in the interior of an electric vehicle, and more particularly, to a battery charger used when charging an electric vehicle battery (power cell) from an AC power source outside the vehicle. It is about.

[0002]

2. Description of the Related Art FIG. 5 is a block diagram of a conventional battery charger of this type. Hereinafter, description will be given with reference to this drawing.

The battery charger 80 includes an AC-DC converter 86 for converting the AC voltage of the AC power supply 82 into a DC voltage to charge the battery 84, and a main switch 88 for starting the operation of the AC-DC converter 86. , A voltage detection resistor 90 connected in parallel to the battery 84, and a charging control unit 92 that stops the operation of the AC-DC conversion unit 86 when the battery voltage detected by the voltage detection resistor 90 becomes a constant value. Be prepared.

When the main switch 88 is turned on, the AC voltage of the AC power supply 82 is supplied to the AC-DC converter 86. Then, the AC-DC converter 86 starts converting the AC voltage into the DC voltage. The DC voltage converted by the AC-DC converter 86 is applied to the battery 84. This allows
A charging current flows from the AC / DC converter 86 to the battery 84.

When charging of the battery 84 progresses and the battery voltage becomes a constant value, the charging control unit 92 stops the operation of the AC-DC conversion unit 86. In this way, charging is completed.

[0006]

However, since the battery charger 80 is mounted on the vehicle, it remains connected to the battery 84 even after charging is completed. Therefore, there is a problem that the discharge current i _D gradually flows from the battery 84 via the voltage detection resistor 90. That is, a part of the electric energy stored in the battery 84 was wasted.

[0007]

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a battery charging device which prevents discharge of a battery via a voltage detecting resistor after completion of charging and effectively utilizes electric energy. .

[0008]

The present invention has been made to achieve the above object, and an AC-DC converter for converting an AC voltage of an AC power supply into a DC voltage to charge a battery, and Main switch for starting the operation of the AC-DC converter, the voltage detection resistor connected in parallel to the battery, and the operation of the AC-DC converter based on the battery voltage detected by the voltage detection resistor It is an improvement of the battery charging device including a charging control unit for stopping the battery charging.

That is, a sub-switch that is closed when the operation of the AC-DC converter is started and opened when the operation of the AC-DC converter is stopped is inserted between the voltage detecting resistor and the battery. It is characterized by being done.

[0010]

When the main switch starts the operation of the AC-DC converter, the AC-DC converter converts the AC voltage into the DC voltage, and the sub-switch is closed, so that the voltage detecting resistor is connected in parallel with the battery. Connected. Then, the DC voltage converted by the AC-DC converter is applied to the battery to charge the battery. Further, the battery voltage is detected from the voltage detection resistor, and the charging control unit detects the AC voltage based on the battery voltage.
The voltage detecting resistor is removed from the battery by stopping the operation of the DC converter and opening the sub switch.

[0011]

1 is a block diagram showing an embodiment of a battery charger according to the present invention. Hereinafter, description will be given with reference to this drawing. However, the same parts as those in FIG.

The battery charging device 10 according to the present invention converts the AC voltage of the AC power source 82 into a DC voltage to convert the battery 8
The AC-DC converter 86 that charges the battery 4, the main switch 88 that starts the operation of the AC-DC converter 86, the voltage detection resistor 90 that is connected in parallel to the battery 84, and the voltage detection resistor 90. Charging control unit 1 that stops the operation of the AC-DC conversion unit 86 based on the detected battery voltage
2 is provided. The sub-switch 14 that closes when the operation of the AC-DC converter 86 starts and opens when the operation of the AC-DC converter 86 stops is inserted between the voltage detection resistor 90 and the battery 84. There is. The AC power supply 82 is, for example, a 100 [V] commercial power supply.

FIG. 2 is a circuit diagram more specifically showing the present embodiment. Hereinafter, description will be given with reference to FIGS. 1 and 2. However, the same parts as those in FIG.

The battery charger 10 includes a DC constant voltage output section 16 for outputting a DC constant voltage for control and an AC power supply 82.
An AC power supply plug 18 connected to the battery, a battery plug 20 connected to the battery 84, and the like are additionally provided.

The AC-DC converter 86 transforms the AC voltage of the AC power supply 82, a bidirectional three-terminal thyristor 86b that applies the AC voltage of the AC power supply 82 to the transformer 86a, and a bidirectional three-terminal thyristor 86b. 86c for surge absorption connected between the main electrode terminals of
And a resistor 86d, a bidirectional optical thyristor 86e connected between the main electrode terminal and the trigger electrode terminal of the bidirectional three-terminal thyristor 86b, and a current limiting resistor 86f connected to the bidirectional optical thyristor 86e. , 86g, a rectifying diode 86h for rectifying and smoothing the AC voltage transformed by the transformer 86a and a smoothing capacitor 86i, a backflow preventing diode 86j as a countermeasure against the reverse inflow of current from the battery 84, and a bidirectional optical thyristor. 86e, a light emitting diode 86k forming a photo coupler, a transistor 86m for driving the light emitting diode 86k, a current limiting resistor 86n connected to the light emitting diode 86k,
Resistor 86 for setting base voltage of transistor 86m
p, 86q.

The voltage detecting resistor 90 is composed of voltage dividing resistors 90a and 90b connected in series. Then, the battery detection voltage Vb across the resistor 90a, which is proportional to the actual battery voltage Vb ', is the charging control unit 1
2 is output.

The charging control unit 12 controls the battery detection voltage Vb.
When the battery voltage reaches the timer operating voltage Vt, the timer operating signal St is output and the battery detection voltage Vb becomes abnormal voltage Ve.
Voltage detection circuit 1 that outputs a charge stop signal Ss when the voltage reaches
2a, a timer circuit 12b that starts to operate with a timer operation signal St and outputs a charge stop signal Ss after a lapse of a fixed time ts, a transistor 12c that is turned on by the charge stop signal Ss, and a base voltage setting resistor of the transistor 12c 12d and 12e and the transistor 12
Comparator 12f in which the collector of c is connected to the + input terminal
And resistors 12g and 12h for setting constant voltage connected to the + input terminal of the comparator 12f, and resistors 12i and 12 for setting reference voltage connected to the-input terminal of the comparator 12f.
j, a positive feedback resistor 12k connected between the + input terminal and the output terminal of the comparator 12f, an inverter 12m connected to the output terminal of the comparator 12f, and an antiparallel resistor 90a. It is composed of the connected diode 12n.

The DC constant voltage output section 16 transforms the AC voltage of the AC power supply 82 and a transformer 16a.
The rectifying diode 16b and the smoothing capacitor 16c for rectifying and smoothing the AC voltage transformed by, the backflow prevention diode 16d, and the smoothed voltage (hereinafter referred to as "smooth voltage V
s ". ) To input a DC constant voltage Vout (= Vcc)
And a DC constant voltage power supply circuit 16e for outputting Although not shown, the DC constant voltage power supply circuit 16e is composed of a three-terminal regulator IC and its external parts.

The sub switch 14 is composed of an electromagnetic relay, and is provided on the smoothed voltage Vs side of the DC constant voltage output section 16 and the inverter 1.
The coil 14c is connected to the 2m output side, and the normally open contact 14a is connected between the voltage detecting resistor 90 and the battery 84.

FIG. 3 shows the voltage detection circuit 12a shown in FIG.
FIG. 6 is a circuit diagram showing more specifically the timer circuit 12b. Hereinafter, description will be given with reference to FIGS. 1 to 3. However,
The same parts as those in FIG. 1 and FIG.

In FIG. 3, when the temperature T of the transformer 86a exceeds the maximum value Tmax, an abnormal temperature detecting circuit 26 for outputting a charge stop signal Ss is additionally provided.

The voltage detection circuit 12a has a timer operating voltage V
comparator 22a for detecting t, comparator 22b for detecting abnormal voltage Ve, and resistor 22 for setting timer operating voltage Vt
c, 22d and resistors 22e, 2 for setting the abnormal voltage Ve
2f. The timer circuit 12b is composed of a timer IC 24a and an OR gate 24b. The abnormal temperature detection circuit 26 includes a comparator 26a for detecting the maximum value Tmax and a maximum voltage Vma corresponding to the maximum value Tmax.
The resistors 26b and 26c for setting x, the positive temperature coefficient thermistor 26d thermally coupled to the transformer 86a, and the resistor 26e for voltage division.

FIG. 4 is a flow chart showing the operation of the battery charger 10. Hereinafter, description will be given with reference to FIGS. 1 to 4.

Since the battery charger 10 is mounted on a vehicle, it is already connected to the battery 84. So first,
The battery charger 10 is connected to the AC power source 82 (step 101). Then, the main switch 88 is turned on (step 102). Then, the DC constant voltage output unit 1
An AC voltage is supplied to 6 to generate a DC constant voltage Vcc for control. The charging control unit 12 starts operating with the constant DC voltage Vcc. Before charging, since the normally open contact 14a is open, the battery detection voltage Vb becomes
It is almost at ground potential through n. That is, the battery detection voltage Vb is the timer operating voltage Vt and the abnormal voltage V
Since it is lower than e, the charging stop signal Ss is not output.
Therefore, the base voltage of the transistor 12c is "L (low potential)", and the transistor 12c is off. As a result, the voltage of the + input terminal becomes higher than the voltage of the − input terminal of the comparator 12f, the output of the comparator 12f becomes “H (high potential)”, and the output of the inverter 12m becomes “L”. On the other hand, the coil 14c of the sub-switch 14 is connected between the smoothed voltage Vs side of the DC constant voltage output unit 16 and the output side of the inverter 12m. 14c is energized (step 10)
3). Then, the normally open contact 14a is closed (step 104), the voltage detection resistor 90 is connected in parallel to the battery 84, and the battery detection voltage Vb is obtained (step 105).

When the output of the comparator 12f becomes "H", the transistor 86m is turned on and the light emitting diode 86k is energized. As a result, the light emitting diode 86k emits light and the bidirectional optical thyristor 86e is turned on. When the bidirectional optical thyristor 86e is turned on, a trigger current flows in the bidirectional three-terminal thyristor 86b, the bidirectional three-terminal thyristor 86b is also turned on, and the AC voltage of the AC power supply 82 is applied to the transformer 86a. In this way, charging is advanced (step 106).

While charging is in progress, the temperature T of the transformer 86a is increased.
Is higher than the maximum value Tmax (step 107), and it is determined whether the battery detection voltage Vb is higher than the timer operating voltage Vt (step 10).
8). If T <Tmax and Vb <Vt, step 1
Return to 06. If T ≧ Tmax, the temperature of the transformer 86a has risen abnormally, so charging is stopped and the normally open contact 14a is opened (step 109). Also, Vb ≧ V
If t, it is determined whether the battery detection voltage Vb is higher than the abnormal voltage Ve (step 110). Vb <
If it is Ve, after a certain time ts has passed (step 11
1) Stop charging and open the normally open contact 14a (step 109). If Vb ≧ Ve, the charging is immediately stopped and the normally open contact 14a is opened (step 109).

Here, the operation of step 109 will be described in detail. When the charge stop signal Ss is output, the base voltage of the transistor 12c becomes "H" and the transistor 12c is turned on. As a result, the comparator 12f
The voltage of the + input terminal becomes lower than the voltage of the-input terminal of, the output of the comparator 12f becomes "L", and the output of the inverter 12m becomes "H". Therefore, since the potential difference between the smoothed voltage Vs side of the DC constant voltage output unit 16 and the output side of the inverter 12m disappears, the coil 14c is de-energized and the normally open contact 14a is opened. In this way, the voltage detection resistor 90 is removed from the battery 84. Further, since the output of the comparator 12f becomes "L", the transistor 86m is turned off, the light emitting diode 86k does not emit light, and the bidirectional optical thyristor 86e is turned off. As a result, the bidirectional three-terminal thyristor 86b is also turned off and charging is stopped.

In this way, by the sub switch 14,
The voltage detecting resistor 90 is connected to the battery 84 only during charging, and the voltage detecting resistor 90 is removed from the battery 84 when charging is stopped. Therefore, the battery 84 is not discharged through the voltage detection resistor 90 when the charging is stopped.

Although the sub switch 14 is composed of the coil 14c and the normally open contact 14a in the present embodiment, the sub switch 14 is not limited to this, and may be a so-called semiconductor relay using a transistor, a thyristor or the like. May be.

Conventionally, a large transformer has been used with a margin to prevent burnout. On the other hand, in the present embodiment, since the abnormal temperature detection circuit 26 is attached, the transformer 86a can be used up to the limit of burnout.
Minimization can be achieved as a result of minimizing the size margin.

[0031]

According to the battery charger of the present invention, the voltage detecting resistor is connected to the battery by the sub-switch only while the AC-DC converter is operating. Therefore, it is possible to prevent the battery from being discharged through the voltage detecting resistor when charging is stopped, so that the electric energy stored in the battery can be effectively used without waste.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of the present invention.

FIG. 2 is an overall circuit diagram more specifically showing the embodiment of FIG.

FIG. 3 is a partial circuit diagram more specifically showing a part of FIG.

FIG. 4 is a flowchart showing the operation of the embodiment of the present invention.

FIG. 5 is a configuration diagram showing a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Battery charger 12 Charge control unit 14 Sub switch 14a Sub switch normally open contact 14c Sub switch coil 82 AC power supply 84 Battery 86 AC-DC converter 88 Main switch 90 Voltage detection resistor

Claims (1)

[Claims] 1. An AC-DC converter for converting an AC voltage of an AC power supply into a DC voltage to charge a battery, and an AC-DC converter.
A main switch for starting the operation of the DC converter, a voltage detection resistor connected in parallel to the battery, and the operation of the AC-DC converter based on the battery voltage detected by the voltage detection resistor. In a battery charger for a vehicle mounted on an electric vehicle, the sub-switch being closed when the operation of the AC-DC converter is started and opened when the operation of the AC-DC converter is stopped. A battery charging device mounted on an electric vehicle, which is inserted between a detection resistor and the battery.