This is a DC-to-DC Step-up Booster circuit (Input 3.5V-13V) to 12VDC / 1.5A Output
Step 1: Introduction
The schematic is from the www.elecfree.com
I encourage you to pay a visit as there are lots of useful schematics to use freely.
All I did was to draw the PCB layout and test the circuit which works perfectly well.
Lets get started.
A Step-up circuit receives a lower voltage and produces a higher Output to be used where that higher voltage is not available. Step-up boosters have lots of uses with most common on battery operated applications.
This is a DC-to-DC converter. The Input voltage can be as low as 3.5V – 13V DC and can provide 12VDC Output.
A Li Ion Battery of 3.7V nominal voltage can drive this circuit to provide an Output of 12V / 1.5A.
Step 2: Components
There are no critical components here except perhaps for the ferrite coil as a ready made choice which is easy to construct it by yourself as I did. The main component is the IC= MC34063 which simplify the whole circuit as it requires only a few extra components to operate.
The MC34063A Series is a monolithic control circuit containing the primary functions required for DC−to−DC converters. These devices consist of an internal temperature compensated reference, comparator, controlled duty cycle oscillator with an active current limit circuit, driver and high current output switch. This series was specifically designed to be incorporated in Step−Down and Step−Up and Voltage−Inverting applications with a minimum number of external components.
Advantages of MC34063A
• Operation from 3.0 V to 40 V Input
• Low Standby Current
• Current Limiting
• Output Switch Current to 1.5 A
• Output Voltage Adjustable
• Frequency Operation to 100 kHz
• Precision 2% Reference
All Resistors are 1/4W.
[T] TIP31 is a NPN power transistor. All Amperage Output passes through it.
[L1] 100μH ferrite coil. If there is a need to construct it by yourself purchase a toroidal ferrite of outer diameter = 20mm x inner diameter hole= 10mm x 10mm high and a wire of 1mm – 1.5mm width x 0.5miter long and make 5 tight turns in equal distances. Ferrite dimensions are not so critical. A difference of a few (1-3mm) on the above dimensions will be ok.
[D] A Schottky Barrier Diode must be used.
[TR] A multiturn PCB trimmer used here to fine tune the Output voltage as close to 12V.
[C] C1 & C3 are Polarity Capacitors so pay attention when placing them on PCB.
Step 3: Parts List
R1 = 0.22 Ohm x1
R2 = 180 Ohm x1
R3 = 1.5K x1
R4 = 12K x1
TR1 = 1K multiturn PCB trimmer x1.
T1 = TIP31A or TIP31C x1
L1 = 100μH Ferrite Coil x1. See text above for more info.
D1 = Schottky Barrier Diode. 1N5821 (21V - 3A) or 1N5822 (28V – 3A) or MBR340 (40V – 3A) x1.
C1 = 100μF / 25V X1.
C2 = 0.001μF (102 code) x1
C3 = 2200μF / 25V
[IC] INTERGRATED CIRCUIT:
IC1 = MC34063 8 PIN IC & 8 PIN DIP socket.
PCB board 55mm high x 41mm width x1.
Update: after @ClockworkPheonix suggestion i have re-draw the PCB (Vr:02) which now is 58mm high and 41mm width. Also the wire connection close to T1 have been removed. Υou may choose the PCB that suits you best.
2 PIN PCB Terminal Block x2.
A Solid Core wire of 1 – 1.5mm x 50mm.
If you notes excessive heat at the T1= TIP31 a small aluminum heat sink must be mounted otherwise the transistor may be damaged.
Step 4: Construction
I have included enough pictures to follow. If it is to use the Iron - Steam Iron method, print the PCB layout the way it is. Do NOT flip the image and do NOT use steam!
Not all of us know how to use a CAD application, so to make it easier there is a BMP lossless image of the PCB layout in files section to print preferably using a laser printer. The exact dimensions of the PCB are 55mm x 41mm. You can use the print preview of the Corel Photo Paint for example to dynamically re-size the PCB layout to meet the exact dimensions before printing.
This is by far not the best way to print a PCB layout but for traces at that size works just fine for any amateur enthusiast. So, go ahead and make it!