Electronics_For_You_July_2017

Do-it-yourself

124 July 2017 | ElEctronics For you http://www.EFymag.com

Low-Cost 3.7V To 5V-6V

DC-To-DC ConverTer

Petre tzv. Petrov

S.C.^

Dwive

Di

T

his article presents a simple,

low-cost DC-to-DC converter

that converts 3.6V-3.7V bat-

tery input into three outputs of 6V,

5.3V and 5V. These voltage outputs

can be used simultaneously or

separately. The converter is use-

ful for digital and analogue audio

equipment including portable audio

amplifiers and MP3 players, and for

experiments with digital and ana-

logue electronics.

3.7V and 3.6V (3x1.2V) recharge-

able batteries are widely available at

low cost. But most equipment oper-

ate off 5V or 6V. So you cannot use

3.7V and 3.6V batteries even if you

use two 3.7V batteries (3.7x2=7.4V)

or four 1.2V batteries (1.2x4=4.8V).

Hence you need a small DC-to-DC

converter to get 5V, 6V or both of

these, depending on the intended

application. The converter described

here provides a simple solution using

an MC34063A IC.

Advantages of MC34063

MC34063A is ideal for small projects

like DC-to-DC converters as it offers

the following advantages:

1. Low cost


2. Easy-to-use DIP8 package


3. Operating input voltage of 3V-
   40V DC from NiCd, NiMH or Li-ion
   rechargeable batteries


4. Low quiescent current


5. Current limiting feature for the
   input voltage


6. Output adjustable with the
   help of a simple resistor divider net-
   work or trimmer potentiometer


7. Typical operation frequency
   of around 45kHz, which can be
   increased to around 100kHz


8. Built-in reference voltage of
   1.25V


9. Internal output transistor ca-
   pable of switching up to 1.5A

Circuit and working

Fig. 1 shows circuit of the 3.7V

to 5V-6V DC-to-DC converter. It

is built around switching regula-

tor MC34063A (IC1), two 1N5819

Schottky diodes (D1 and D4), two

1N4007 rectifier diodes (D2 and

Fig. 1: Circuit diagram of low-cost 3.7V to 5V-6V DC-to-DC converter

Parts List

Semiconductors:

IC1 - MC34063A DC-to-DC

converter control circuit

D1, D4 - 1N5819 Schottky diode

D2, D3 - 1N4007 rectifier diode

LED1, LED2 - 5mm LED

Resistors (all 1/4-watt, ±5% carbon):

R1 - 0.33-ohm/0.47-ohm

R2 - 180-ohm

R3 - 10-kilo-ohm

R4 - 2.7-kilo-ohm

R5, R6 - 3.3-kilo-ohm

R7 - 470-ohm

Capacitors:

C1 - 470μF, 16V electrolytic

C2, C4, C6, C8 - 100nF ceramic disk

C3 - 470pF ceramic disk

C5, C7, C9 - 100μF, 16V electrolytic

Miscellaneous:

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

L1

100u, 1A

CON1

3.7V

BATTERY

SC^1

SE^2

TC^3

(^5) FB GND 4
(^7) IPK
(^8) DRI
(^6) Vcc
IC1
MC34063A
D1
1N5819
R2
180E
R1
0.33E /
0.47E
F1
1A FUSE
C1
470u
C2
100n
16V
C3*
470p
GND
R4
2.7K
R3
10K
C4
100n
C5
100u
16V D2
1N4007
R5
3.3K CON2
VOUT1 = 6V
LED1
LED2
D3
1N4007
C6
100n
C7
100u
16V
CON3
VOUT2 = 5.3V
C8
100n
C9
100u CON4
VOUT3 = 5V
16V
D4
1N5819
R6
3.3K
FOR 6V
FOR 5.3V
470ER7 FOR 5V