JPH0326024B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a charger. The charger used for cycle service uses a leakage transformer to increase the initial charging current value and reduce the final charging current, and a charger that uses a thyristor to control the phase to obtain constant voltage and constant current characteristics. is generally adopted.

However, the former has the disadvantage that the structure of the transformer is complicated and its volume is large. Furthermore, the latter has the disadvantage that the commutation overlap angle generated by the thyristor adversely affects the power supply side.

The present invention aims to eliminate the above-mentioned drawbacks. In other words, the charging current that passed within a certain sampling time is integrated, and when a certain value is reached, charging is turned off, and the charging current that is passed during the next sampling time is integrated again, and when a certain value is reached, charging is turned off. The present invention provides a charger that repeatedly turns off and charges a storage battery with a constant current.

An embodiment of the present invention will be described. In FIG. 1, a storage battery 5 is charged by an AC power supply 1 via a thyristor zero cross switch 2, a transformer 3, and a rectifier 4. The charging current is detected as the potential of the shunt 6,
input to the first oscillator 7. The oscillator 7 is composed of an amplifier 8 and a VF converter 9. That is, the first oscillator 7 outputs a pulse with an oscillation frequency proportional to the potential of the shunt 6, that is, the magnitude of the charging current. The output of the counter 10 is stopped when the count value of the pulses of the first oscillator 7 reaches a predetermined value within a certain period of pulse width which is the sampling time of the second oscillator 11.

In FIG. 2a, when a charging current I _B flows due to the rectified output with respect to the storage battery voltage E _B , the first oscillator 7 generates a pulse such as VF for I _B. This pulse is counted by a counter 10, and when it reaches a certain value, the output G is stopped. The output G of this counter 10 becomes zero and the thyristor zero cross switch 2 stops. This zero cross switch 2 always turns on and off at the zero point of the input power supply 1 in response to the signal from the counter 10, and generates very little switching noise with respect to the power supply 1. Note that even if the output G of the counter 10 becomes zero, the thyristor zero cross switch 2 continues to conduct electricity until the power supply 1 reaches the zero point. As charging progresses and the storage battery voltage increases, the charging current I _B also decreases and the output frequency of the first oscillator 7 also decreases, so the output G of the counter 10 within the sampling time is compared to the case in Figure 2a. However, it becomes long as shown in Fig. 2b. The charging characteristics of the charger configured in this way are the third
As shown in the figure, the current is constant at the beginning of charging, and if the constant current is no longer obtained within the sampling time, the charging current decreases. By charging within a constant current, the storage battery 5 can be protected, and although the charging current drops due to circuit regulation, sufficient charging can be achieved by using a timer etc. be. Incidentally, since the thyristor zero cross switch 2 is used, a power supply error within a half cycle of the power supply 1 occurs, but this hardly causes a problem during charging. Furthermore, by changing the count value of the counter 10 during charging, it is also possible to perform staged charging.

As mentioned above, since constant current control is performed using the thyristor zero cross switch, there is extremely little noise generated in the power supply. Furthermore, by shortening the sampling time, the power supply does not need to have an excessive power supply capacity. On the other hand, there is no need for a transformer with a special structure like a transformer having a leakage piece, and the industrial value is extremely great.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram of a charger showing an embodiment of the present invention, Fig. 2 is a time chart of the charger in this embodiment, and Fig. 3 is a charging current characteristic curve diagram of the charger in this embodiment. . 2 is a thyristor zero cross switch, 5 is a storage battery, 6 is a shunt, 7 is a first oscillator, 10 is a counter, and 11 is a second oscillator.

Claims (1)

[Claims] 1. A first oscillator that generates pulses with a frequency proportional to the magnitude of the charging current, a counter that counts the pulses, a second oscillator that resets the counter at fixed intervals longer than the power supply cycle, and a counter that counts the pulses. A charger characterized in that the thyristor switch controls the AC power source on and off by output, and the thyristor switch is turned off when the integrated value of the charging current reaches a certain value within the oscillation cycle of the second oscillator.