The preferred voltage levels while working in most of the electronics project lie in between the value 5V to 6V. However, 3.6V-3.7V batteries are found abundantly in the market with the cheap price tag.
So, we presented an economic solution to generate commonly used operating voltages using these cheap and easily available 3.6V and 3.7V batteries. Using two-three batteries of 3.6V (3.6*2=7.2V) and 3.7V (3.7*2=7.4V) doesn’t provide the desired voltage level and thus this project was essential. This DC-to-DC converter project offer three different voltage levels; 6V, 5.3V and 5V at the output terminal. You are free to use these output voltages at the same time for different purposes or separately at a time. This project is a boon to all digital and analog audio experiments and equipments that comprises portable components; audio amplifiers and MP3 players.
Circuit Description of 3.7V to 5V, 5.3V and 6V Converter Circuit
The complete circuit diagram, of the voltage converter circuit is given in fig.1. This low-cost project uses one switching regulator MC34063A (IC1), two 1N5819 Schottky diodes (D1 and D4), two 1N4007 rectifier diodes (D2 and D3), two 5mm LEDs (LED1 and LED2) and some of the discrete components to develop the voltage converter circuit.
One terminal CON1 of the circuit is fed with the 3.7 DC voltage. The project operating voltage range lies in between the range of 3V to 40V. The input DC voltage reaches the IC1 and this regulator generates 6V DC output at the output terminal CON2. You can replace Schottky diodes 1N5819 with 1N5817, 1N5818 or 1N5819 series.
To produce the second output voltage from the converter circuit which is 5.3V, a single rectifier diode D3 is used as a step-down converter to generate 5.3V from 6V passed from IC1 and this voltage is available at the CON3 output terminal. Similarly, diode D4 takes output from D3 and steps down the voltage level to 5V and this voltage level can be used through output port CON4. In this way, combination of regulator and diodes are used to generate three different voltage values.
For the values of components used in this project, a total of 100mA current is generated at the output terminal. This value can be modified using different values of component in the project. Along with the desired voltage levels, the project also ejects a 15mV ripple voltage and to reduce its effects in the circuit, we have included capacitor C3 and LC/RC filters in the circuit.
You don’t need to make further corrections in the project for this particular output, however it is considered best to constantly monitor the input and output voltage levels along with the current and operating frequency level of IC1, induction current of L1 for precise measurement.
To test the circuit, you can feed a 3.7V input voltage from a Li-ion battery. Three 1.2V(3*1.2V=3.6V) NiCd or NiMH batteries can also be used. Instead of this, you can also feed a regulated 3.7V as input to the circuit for testing the circuit.
There are certain points to be considered before practically implementing this project. In absence of load in the circuit, the output voltage varies with the value of resistor R7 (270-470 ohms) used in the circuit. Similarly, to ensure normal functioning of the circuit, a load of the value larger than 10mA should be fixed at terminal CON4. The current sensitivity of the circuit is dependent on the value of resistor R1.
PARTS LIST OF 3.7V TO 5V, 5.3V AND 6V CONVERTER CIRCUIT
|Resistors (all ¼-watt, ± 5% Carbon)|
|R1 = 0.33 Ω /0.47 Ω
R2 = 180 Ω
R3 = 10 KΩ
R4 = 2.7 KΩ
R5, R6 = 3.3 KΩ
R7 = 470 Ω
|C1 = 470 µF, 16V (Electrolytic Capacitor)
C2, C4, C6, C8 = 100nF (Ceramic Disk)
C3 = 470pF (Ceramic Disk)
C5, C7, C9 = 100 µF, 16V (Electrolytic Capacitor)
|IC1 = MC34063A DC-to-DC converter control circuit
D1, D4 = 1N5819 Schottky diode
D2, D3 = 1N4007 Rectifier Diode
LED1, LED2 = 5mm LED
|CON1 – CON4 = 2-pin terminal connector
F1 = 1A Fuse with holder
L1 = 100µH, 1A inductor
3.7V Li-ion battery or 3×1.2V NiCd Batteries