Step-Up DC-DC Converters

[Help]

stepping up battery voltage

Dear All,

Currently I’m doing for hobby testing. I plan to use the solar energy to charge my handphone.

I have few concerns:
1) I have done some testing with my old handphone charger, when the charger is changing the battery i measure the voltage is 3.8Volt when full charged. May i know what the voltage range 3.3 Volt or 5Volt to charge the handphone battery?

2) As we know the solar power is not constant supply. So, i plan to use MAX1724EZK33-T(Iout = 150mA) or MAX1674(Iout = 200mA) IC to charge my handphone battery. This 2 IC is it suitable for charger? Please advice..

3) I would like to take the challanging to add one data reading function in my charger. This function is measure the Voltage and Current and then stores the reading data in EEPROM. On the uC side I think i should use AT89S2051 because the operating range can be 2.7~5.5V, so use charger voltage to supply the board IC.
If i at those function in the charger, i guess the current consumption for the board will be high, not sure the Step-up Converters IC can handle the power.

Please anyone can give some advice?

Thank you,
Help

 

[Taner]

solar module dc/dc converter

Hi,
if you want to make a solar battery charger there have some
specific requirements like:
1. Measuring of the output voltage and current of the Solar Module (input voltage and current of the DC-DC converter) - for MPPT (maximum power poin tracking) algorithm.
2. Measuring of the output voltage and current of the DC-DC converter (voltage and current of the battery).
3. Measuring of the temperature of the battery and solar module.

When the battery is empty then PWM controller must maintain the constant input voltage (output voltage of solar module), because the current of the solar module depends on the solar irradiation level and you can maintain only a constant voltage.
When the battery is charged you can work in trickle charge mode with MPPT algorithm.
Battery voltage is controlled and when reached the charged level, PWM must stops or can continue to work in trickle charge mode.

Better choice for PWM controller is a some 8-bit MCU with minimum 3-4 ADC inputs and minimum one PWM output.

Best regards: Taner

 

[Help]

build solar constant voltage dc supply circuit

Dear Taner,

Thanks for sharing your idea.

..because the current of the solar module depends on the solar irradiation level and you can maintain only a constant voltage.
Ya, you are rite. The current is depends on the solar irradiation level and we can get voltage measure reading but the current reading is very low. In this case, it will take very long time to charge the battery.
But sometime the sun light is very low or may be the charger is use at indoor environment. So, the voltage might very low sometime, ~1V and the current might be <1mA. When the power is low how we going to maintain the supply enough for the circuit operation?
Is it we have to use step-up dc-dc converter to fix the voltage at 5V for the circuit operation?

I feel that is some other manufacture like MAXIM, DALLAS, LINEAR, ANALOG and so on..have design the IC for this kind of design. If we using traditional way like using Comparator, ADC convertor, driver and so on..So it will need more power to supply to those IC.

Please advice,..

Thank you,.

 

[cheegii]

I think you may use 7805 for solar panel and LX1995 dc dc step up converter for charger. If your solar cell have low watt, then connect it to directly to your battery. It won't over charge and explode. I made dc dc converter with LX1995. It is converting 3 volts to 50 volts. I used 9v output, adjusting resistors. Also max1896 is ok to use.

 

[PCBWING]

solar energy to charge cellphone,sounds like fine