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The simplest charger case analysis

The simplest charger case analysis
In recent years, as the market for portable devices such as mobile phones, tablets, digital cameras, MP3 players and personal digital assistants (pdas) continues to grow rapidly, various battery chargers have also gained rapid development. There are many types of chargers, including constant voltage limited current chargers, constant voltage/constant current chargers, pulse chargers, fast chargers and trickle chargers, as well as multi-purpose chargers with lighting functions.
The charger shown in the figure only USES three components, so it is called the simplest charger. The circuit is a capacitor current limiting constant current charging circuit. The value of charging current is determined by the current limiting capacitor C. No matter one battery is charged separately or several or more batteries are charged in series, the value of charging current remains unchanged. D1 and D2 are rectifying diodes. Current limiting capacitors should be non-polar capacitors with the withstand voltage of over 400V. The maximum charging current should not exceed 100mA. If the battery is charged to 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 kind of dc power supply battery, nickel-cadmium battery can repeat more than 500 times charge and discharge, economic and durable. Its internal resistance is small, both internal resistance is very small, can be quickly charged, and can provide a large current for the load, and discharge voltage change is very small, is a very ideal dc power supply battery.
The simple nickel-cadmium battery charger not only has constant current charging characteristics, but also can prevent the battery from overcharging. The charger circuit is shown in the figure. The charger charges four nickel-cadmium batteries in series. 220V ac city by capacitor C1 buck, D1~D4 rectifier, R true, D. After voltage stabilization, LED1 and LED2 flow into nickel-cadmium battery to realize small current constant current charging. If the components are selected as shown, the charging current is approximately 60mA.
At the beginning of charging, the series voltage of the four nickel-cadmium batteries is less than 5. 4V, at this time the voltage regulator tube D; Deadline. As the charging continues, the terminal voltage of nicad battery gradually increases, when the voltage increases to 5. When 4V is above, D; By reverse breakdown, the voltage at both ends of D true is clamped at 7.5v, the ni-cd battery voltage will not rise continuously, if it continues to rise, LED1 and LED2 will be turned off by conduction, so as to prevent overcharging of the battery and protect the service life of the battery.
Nickel-cadmium battery can repeat more than 500 times charge and discharge, economic and durable. Its internal resistance is small, both internal resistance is very small, can be quickly charged, and can provide a large current for the load, and discharge voltage change is very small, is a very ideal dc power supply battery. Compared with other types of batteries, nickel-cadmium batteries can withstand over charge or over discharge.
The chargers shown in the figure are simple and practical, and adopt international standards to ensure safe and reliable use. It USES half - wave rectifier, divided into two ways to charge the battery, each way can charge two 5. Nickel cadmium battery. The charging current is 50mA. The charging time is 14 hours.
220V mains power is reduced to 9V voltage by transformer B. When D true end is positive half cycle, D: conduction, D: cut-off, electricity flows through D true rectifier, R. Charge the battery by limiting current. Similarly, when D: end is positive half cycle, D, cut-off, D: conduction, and electricity flows through D. Rectifier, R+ current limit to charge the other two batteries. LED: and LED2 are charging indicator lights, and R true and R: are protective resistances of LED.
Homemade no. 5 battery charger
As now multi-functional development trend of mobile phone, mobile phone power consumption gradually increase, this will increase the demand of the battery, but on the other hand, the battery with the handset volume shrinking becomes smaller and smaller, and battery technology has not improved, this will bring the standby time reduce problems, give out the use of mobile phones has brought a lot of trouble.
In order to solve this problem, this paper introduces a mobile phone emergency charger, which USES two no. 5 alkaline batteries or rechargeable batteries, charging the mobile phone directly after boosting the voltage through the circuit without affecting the normal use of the mobile phone.
The charger shown in the figure is simple, easy to make and practical. Its working principle is basically the same as the above example. Four batteries can be charged at the same time in the four positions of A, B, C and D.

220V ac voltage by double 6V transformer B step-down, full wave rectification. Charge each battery slowly. R:, R. , R true and R: are current-limiting resistances, and D5, D6, D7 and D8 leds are respectively charging indicators.
Nickel-cadmium battery multi-function constant current charger
The charging device can not only be a constant current charger, but also a current limiter and a variable power load. The circuit is shown in figure 4-7. The principle is as follows: when the electric current of the appliance is less than the set value, BG: works in the saturated state and the pressure drop at both ends of ce is very small. When it exceeds the set value, BG enters the constant current state and ACTS as a current limiting function. Since the current of BG: is adjustable, it can be used as a variable power load. It can be seen that load can be limited by connecting to A and B terminals. When only used as a charger, connect 2-4 sections of pool to AB, and adjust W1 to adjust the charging current.
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