In recent years, with the continued rapid development of mobile devices such as mobile phones, tablet computers, digital cameras, MP3 players and personal digital assistants (PDAs), various battery chargers have also developed rapidly. There are many types of chargers, including constant-voltage current-limiting chargers, constant-voltage / constant-current chargers, pulse chargers, fast chargers, and trickle chargers, and multi-purpose chargers with lighting and other functions .
The charger shown in the figure uses only three components, so it is called the simplest charger. This circuit is a capacitor current-limiting constant-current charging circuit. The magnitude of the charging current is determined by the current-limiting capacitor C. Whether charging a battery alone or charging several or dozens of batteries in series, the charging current does not change. D1 and D2 are rectifier diodes. Current-limiting capacitors should be non-polar capacitors with a withstand voltage greater than 400V. The maximum charging current should not exceed 100mA. If it is used to charge a No. 5 nickel-cadmium battery with a capacity of 500mAh, the charging time is about 6 hours.
Simple nickel-cadmium battery charger Nickel-cadmium battery is a DC-powered battery. The nickel-cadmium battery can be charged and discharged more than 500 times, which is economical and durable. Its internal resistance is small, both the internal resistance is small, it can be quickly charged, and it can provide a large current to the load, and the voltage change during discharge is small, it is a very ideal DC-powered battery.
The simple nickel-cadmium battery charger has the characteristics of constant current charging and can prevent the battery from being overcharged. The charger circuit is shown in the figure. The charger charges four Ni-Cd batteries in series. The 220V AC city is stepped down by capacitor C1, D1 ~ D4 are rectified, and R is true and D is. After the voltage is stabilized, it flows into the nickel-cadmium battery through LED1 and LED2 to realize small current and constant current charging. If the component is selected according to the parameters shown in the figure, its charging current is approximately 60mA.
At the beginning of charging, the voltage value of the four nickel-cadmium batteries in series was less than 5.4V. At this time, the voltage regulator D was cut off. As the charging continues, the terminal voltage of the nickel-cadmium battery gradually increases. When the voltage rises to above 5.4V, D; is reverse breakdown, the voltage across the true end of D is clamped at 7.5V. The voltage will not continuously increase. If it continues to increase, LED1 and LED2 will turn from on to off, thereby preventing the battery from overcharging and protecting the battery life.
Nickel-cadmium batteries can be charged and discharged more than 500 times, which is economical and durable. Its internal resistance is small, both the internal resistance is small, it can be quickly charged, and it can provide a large current to the load, and the voltage change during discharge is small, it is a very ideal DC-powered battery. Compared with other types of batteries, nickel-cadmium batteries are resistant to overcharge or overdischarge.
The charger shown in the figure is simple and practical, and adopts international standards to ensure safe and reliable use. It uses half-wave rectification to charge the battery in two ways, each of which can charge two 5. Nickel-cadmium battery. The charging current is 50mA. The charging time is 14 hours.
The 220V mains voltage is reduced to 9V by the transformer B. When the true end of D is a positive half cycle, D: is on, D: is off, the current is rectified by D, R. The current limit charges the battery. Similarly, when D: terminal is a positive half cycle, D is off, D: is on, and current passes through D. Rectify and charge the other two batteries after R + current limit. LED :, LED2 are charging indicators, R true, R: is the protection resistance of light-emitting diodes.
Self-made No. 5 battery charger With the current multi-functional development trend of mobile phones, the power consumption of mobile phones has gradually increased, which has increased the requirements for batteries. It is getting smaller and smaller, but the battery-powered technology has not been improved, which brings the problem of reduced standby time and brings a lot of trouble for people who often go out to use mobile phones.
In order to solve this problem, this article introduces a mobile phone emergency charger, which uses two AA alkaline batteries or rechargeable batteries. After the circuit is boosted, the mobile phone is charged by direct charging. It does not affect the normal use of the mobile phone when charging. .
The charger shown in the figure is simple, easy to make, and practical. Its working principle is roughly the same as the previous example. Four batteries can be charged at the same time in the four positions A, B, C, and D. Of course, it can also be charged at any position One battery is charged, which overcomes the shortcoming of the above example that the western battery must be charged at the same time.
220V AC is stepped down by double 6V transformer B, after full wave rectification. Slowly charge each battery. R :, R. , R true, R: current-limiting resistors, D5, D6, D7, D8 light-emitting diodes are charging indicators.
Multifunctional constant current charger for nickel-cadmium battery
In addition to being a constant current charger, the charging device can also be used as a current limiter and variable power load. The circuit is shown in Figure 4-7. The principle is: when the electrical current of the consumer is less than the set value, BG: works in a saturated state, and the voltage drop across ce is small. When it exceeds the set value, BG enters the constant current state and functions as a current limit. Because the current of BG: is adjustable, it can be used as a variable power load. It can be seen that connecting the load to the A and B ends can limit the current. When only used as a charger, connect 2-4 sections of the pool to AB, and adjust W1 to adjust the charging current.
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