This is a circuit of power supply that is produces a 5 VDC voltage. This circuit is rechargeable battery using solar panel. The solar panel charges the battery when sunlight is bright enough to produce a voltage above 1.9v. A diode is required between the panel and the battery as it leaks about 1mA from the battery when it is not illuminated. This is the figure of the circuit.
How is the power supply work? The regulator transistor is designed to limit the output voltage to 5v. This voltage will be maintained over the capability of the circuit, which is about 10mA. The oscillator transistor must be a high-current type as is turned on for a very short period of time to saturate the core of the transformer. This energy is then released as a high-voltage pulse. These pulses are then passed to the electrolytic and appear as a 5v supply with a capability of about 10mA. If the current is increased to 15mA, the voltage drops to about 4V. The circuit operates at approx 50 KHz and the pulses quickly charge the electrolytic.
The 15k resistor has a 3k3 "trimmer" resistor to enable you to adjust the output to exactly 5v or slightly above 5v. Microcontrollers will work up to 5.5v but some will freeze at 5.6v, so be careful. The output voltage is monitored at the join of the 15k resistor (and 3k3) and the 2k2 resistor. The voltage at this point is exactly 0.63v (630mV) and at this voltage the regulator transistor turns ON and robs the oscillator transistor with "turn-on" voltage.
How is the power supply work? The regulator transistor is designed to limit the output voltage to 5v. This voltage will be maintained over the capability of the circuit, which is about 10mA. The oscillator transistor must be a high-current type as is turned on for a very short period of time to saturate the core of the transformer. This energy is then released as a high-voltage pulse. These pulses are then passed to the electrolytic and appear as a 5v supply with a capability of about 10mA. If the current is increased to 15mA, the voltage drops to about 4V. The circuit operates at approx 50 KHz and the pulses quickly charge the electrolytic.
The 15k resistor has a 3k3 "trimmer" resistor to enable you to adjust the output to exactly 5v or slightly above 5v. Microcontrollers will work up to 5.5v but some will freeze at 5.6v, so be careful. The output voltage is monitored at the join of the 15k resistor (and 3k3) and the 2k2 resistor. The voltage at this point is exactly 0.63v (630mV) and at this voltage the regulator transistor turns ON and robs the oscillator transistor with "turn-on" voltage.
