This proposed powerbank circuit was built by me around the popular converter topology known as BOOST CONVERTER. Its best understood by observing the oscillator stage which could be any type of Oscillator(alth
ough i used AMV in my test period) like phase shift, colpit, etc. Just calculate the frequency to be 100khz, duty cycle should be 0.5(50%) and it should be capable of operating within 1v to 6v. 555 timer should not be used as it will shut down at voltages less than 4.5v. I recommend a transistorised Astable MultiVibrator for the oscillator stage.
The second stage is the booster stage built around an inductor, two BJTs a zener diode and a schotkky diode with a filter capacitor. The inductor as we all know opposes the flow of electron(current) and the opposed electron flow yields a cumulative EMF within the inductor's magnetic field and the magnitude of the EMF is a function of the number of turns of the inductor coil. But not to worry, the criticallity of the inductor's number of turns has been reduced through the introduction of a voltage monitor circuit(feedback network) built around Q2, zener, and the associated resistor. When powered with any battery within the alowable range, current flowws into the inductor and oscillator network simultaneosly, the oscillator circuit is automatically triggered and in turn drives the base of Q1 through the 22R base resistor, this drives Q1 into a "Make & Break" condition known as switching! This effect grounds the inductor during the "make" period causing a current ramp (dv/dt) this current ramp which collapses during the "break" period. The collapsed current is sent to the output capacitor rated at 100uF. Althogh 470uF is recommended, but I used 100uF for portability reason.
ough i used AMV in my test period) like phase shift, colpit, etc. Just calculate the frequency to be 100khz, duty cycle should be 0.5(50%) and it should be capable of operating within 1v to 6v. 555 timer should not be used as it will shut down at voltages less than 4.5v. I recommend a transistorised Astable MultiVibrator for the oscillator stage.
The second stage is the booster stage built around an inductor, two BJTs a zener diode and a schotkky diode with a filter capacitor. The inductor as we all know opposes the flow of electron(current) and the opposed electron flow yields a cumulative EMF within the inductor's magnetic field and the magnitude of the EMF is a function of the number of turns of the inductor coil. But not to worry, the criticallity of the inductor's number of turns has been reduced through the introduction of a voltage monitor circuit(feedback network) built around Q2, zener, and the associated resistor. When powered with any battery within the alowable range, current flowws into the inductor and oscillator network simultaneosly, the oscillator circuit is automatically triggered and in turn drives the base of Q1 through the 22R base resistor, this drives Q1 into a "Make & Break" condition known as switching! This effect grounds the inductor during the "make" period causing a current ramp (dv/dt) this current ramp which collapses during the "break" period. The collapsed current is sent to the output capacitor rated at 100uF. Althogh 470uF is recommended, but I used 100uF for portability reason.
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