subject: MCU controls the charger to indicate the working status [print this page] MCU controls the charger to indicate the working status
The design is based on Philips P89LPC916 MCU core, the general conception is that by first using constant current charge, then use the constant voltage charging to reach the load as soon as possible. MCU also controls the charger to indicate the working status LED.
Precision VDD power requires the use of the precision voltage source, Hp laptop battery because this voltage is used as a reference DA-DA voltage converter. Low Dropout (LDO) voltage regulator for the best selection and design of a 3-side LDO LM1117 provide accurate 3.31 V power supply VDD.
Output Solutions Timer0 (Timer 0) control channel buck converter is used to generate the PWM signal switch. As LPC916 with his own chip RC oscillator, to support more stable and more effective especially in the setting mode voltage.HP CGR-B1870AE Battery,HP Pavilion ZD7000 Battery PWM frequency 14kHz only necessary and could be well controlled in the range of frequency oscillator on chip. Buck converter by changing the "open" time to adjust the PWM duty cycle.
System Design
A switch PWM charge control, and its duty cycle as required charging voltage and current feedback to adjust. LPC916 8-bit on-chip high-speed A / D converter provides high accuracy required for monitoring charging voltage. Li-ion applications to avoid the overhead are very important because the load is at its maximum value in the life of the battery. Table 1 for the circuit input / output parameter specifications. Dell Inspiron 1501 battery Dell Inspiron 1525 battery
The next step is to calculate the inductance value, we must first emphasize that the formula gives a duty cycle, output current, the PWM cycle and the relationship between other variables. Inductance value can be assumed that Vi = 5.1V, output voltage Vsat = 0.5V required (at Io = 350mA on, HP Pavilion ZD7000 Battery, Vo = 4.25V, the necessary output current Io = 350mA, 1 / T = 14.7kHz and the duty ratio of 50% calculated). The application of the above values, the only formula used to calculate the inductance of a value at least 10H. In this design, the recommended value of 33-10H inductor. Although you can use more than 5.1 V input voltage, the higher the input voltage requires a higher frequency of PWM or larger inductor, while the cost of the device.
Li-ion batteries should be supporting three distinct stages. If the battery voltage falls below 3V, the need for pre-load and load current must be maintained at 65mA. Once the battery voltage reaches 3V + -1%, which entered the stage of rapid charging, and using a constant current load 350mA. By adjusting the control pulse can maintain a constant current charge. When the battery voltage reaches 4V + -1%, which starts at a constant voltage phase. At this point of tension is maintained at 4.23V, the charge current monitoring. Dell Inspiron 1526 battery Dell Inspiron 1720 battery
In a constant voltage phase, the battery is charging an extra 50 minutes while maintaining the load current is less than 30 mA. The charging time can be used to control a timer, but watch the end of the load in three ways: the detection of load current, use the timer, and temperature monitoring (optional).
From one stage to another stage in the exact brand as follows: pre-load (if necessary): If Vbat 3.0 (1%, while setting Iout = 10%; Ireg = 65mA; phase Fast Charge (charge current): When Vbat
