POWER SUPPLY ATX PC 200W

This power supply circuit uses chip TL494. Similar circuit is used in the most power supplies with output power about 200W.Device use push-pull transistor circuit with regulation of output voltage.

Line voltage goes through input filter circuit (C1, R1, T1, C4, T5) to the bridge rectifier. When voltage is switched from 230V to 115V, then rectifier works like a doubler. Varistors Z1 and Z2 have overvoltage protect function on the line input.
Thermistor NTCR1 limits input current until capacitors C5 and C6 are charged. R2 and R3 are only for discharge capacitors after disconnecting power supply. When power supply is connected to the line voltage, then at first are charged capacitors C5 and C6 together for about 300V.
Then take a run secondary power supply controlled by transistor Q12 and on his output will be voltage. Behind the voltage regulator IC3 will be voltage 5V, which goes in to the motherboard and it is necessary for turn-on logic and for "Wake on something" functions.
Next unstabilized voltage goes through diode D30 to the main control chip IC1 and control transistors Q3 and Q4. When main power supply is running, then this voltage goes from +12V output through diode D.

Stand-By mode

In stand-by mode is main power supply blocked by positive voltage on the PS-ON pin through resistor R23 from secondary power supply. Because of this voltage is opened transistor Q10, which opens Q1, which applies reference voltage +5V from pin 14 IO1 to pin 4 IO1. Switched circuit is totally blocked. Tranzistors Q3 and Q4 are both opened and short-circuit winding of auxiliary transformer T2.Due to short-circuit is no voltage on the power circuit. By voltage on pin 4 we can drive maximum pulse-width on the IO1 output. Zero voltage means the highest pulse-width. +5V means that pulse disappear.

Now we can explain function of running power supply.

Somebody pushes the power button on computer. Motheboard logic put to ground input pin PS-ON. Transistor Q10 closes and next Q1 closes. Capacitor C15 begins his charging through R15 and on the pin 4 IC1 begins decrease voltage to zero thanks to R17. Due to this voltage is maximum pulse-width continuosly increased and main power supply smoothly goes run.

In a normal operation is power supply controlled by IC1. When transistors Q1 and Q2 are closed, then Q3 and Q4 are opened. When we want to open one from power transistors (Q1, Q2), then we have to close his exciting transistor (Q3, Q4). Current goes via R46 and D14 and one winding T2. This current excite voltage on base of power transistor and due to positive feedback transistor goes quickly to saturation. When the impulse is finished, then both exciting transistors goes to open. Positive feedback dissapears and overshoot on the exciting winding quickly closes power transistor. After it is process repetead with second transistor. Transistors Q1 and Q2 alternately connects one end of primary winding to positive or negative voltage. Power branch goes from emitor of Q1 (collector Q2) through the third winding of exciting transformer T2. Next throug primary winding of main transformer T3 and capacitor C7 to the virtual center of supply voltage.

Output voltage stabilisation

Output voltages +5V and +12V are measured by R25 and R26 and their output goes to the IC1. Other voltages are not stabilised and they are justified by winding number and diode polarity. On the output is necessary reactance coil due to high frequency interference.
This voltage is rated from voltage before coil, pulse-width and duration cycle. On the output behind the rectifier diodes is a common coil for all voltages. When we keep direction of windings and winding number corresponding to output voltages, then coil works like a transformer and we have compensation for irregular load of individual voltages.
In a common practise are voltage deviations to 10% from rated value. From the internal 5-V reference regulator (pin 14 IC1) goes reference voltage through the voltage divider R24/R19 to inverting input(pin 2) of error amplifier. From the output of power supply comes voltage through divider R25,R26/R20,R21 to the non inverting input (pin 1). Feedback C1, R18 provides stability of regulator. Voltage from error amplifier is compared to the ramp voltage across capacitor C11.
When the output voltage is decreased, then voltage on the error amplifier is toodecreased. Exciting pulse is longer, power transistors Q1 and Q2 are longer opened, width of pulse before output coil is grater and output power is increased. The second error amplifier is blocked by voltage on the pin 15 IC1.

PowerGood

Mainboard needs "PowerGood" signal. When all output voltages goes to stable, then PowerGood signal goes to +5V (logical one). PowerGood signal is usually connected to the RESET signal.

+3.3V Voltage stabilisation

Look at circuit connected to output voltage +3.3V. This circuit makes additional voltage stabilisation due to loss of voltage on cables. There are one auxiliary wire from connector for measure 3.3V voltage on motherboard.

Overvoltage circuit

This circuit is composed from Q5, Q6 and many discrete components. Circuit guards all of output voltages and when the some limit is exceeded, power supply is stopped.
For example when I by mistake short-circuit -5V with +5V, then positive voltage goes across D10, R28, D9 to the base Q6. This transistor is now opened and opens Q5. +5V from pin 14 IC1 comes across diode D11 to the pin 4 IC1 and power supply is blocked. Beyond that goes voltage again to base Q6. Power supply is still blocked, until he is disconnected from power line input.

ATX Power Connector

Pin	Signal	Color 1	Color 2	Pin	Signal	Color 1	Color 2
1	3.3V	orange	violet	11	3.3V	orange	violet
2	3.3V	orange	violet	12	-12V	blue	blue
3	GND	black	black	13	GND	black	black
4	5V	red	red	14	PS_ON	green	grey
5	GND	black	black	15	GND	black	black
6	5V	red	red	16	GND	black	black
7	GND	black	black	17	GND	black	black
8	PW_OK	grey	orange	18	-5V	white	white
9	5V_SB	violet	brown	19	5V	red	red
10	12V	yellow	yellow	20	5V	red	red

Source :: http://www.pavouk.org/hw/en_atxps.html

power supply Regulator 12V 5A by LM2678-12

This is circuit Switching power supply 12V 5A.
Or circuit dc converterstep down voltage.
Use IC LM2678-12 SIMPLE SWITCHER High Efficiency
5A Step-Down Voltage Regulator.
Input DC Voltage 40Vmax and 16Vmin 5A.
Detail more see in image circuit.

MJ2955 Switching Power Supply 12V 10Amp

The switching power supply provides 12 volts, at 10 amps, maximum, using a discrete transistor regulator with an op-amp functioning as a comparator in the feedback circuit.

With reference to the schematic, the front panel power-on light is not shown. There is no adjustable current limiter in this unit, although R1, R2, R3, Q2, R8, R9, C5 and Q4 set the current limit to approximately 10 amps. As you can see, the design is very similar to that of a linear power supply, except that L1, and D1 have been added, and U1 operates in a switching mode as a comparator with a small amount of hystersis. The switching frequency of this unit varies with the output current drawn by the load. This is an undesireable feature, which is why PWM regulators are used today. With a PWM regulator, the switching frequency is constant and will produce spurs only at known discrete frequencies rather than spurs at all frequencies. The Darlington-connected pass transistor block in the schematic is there twice (in parallel) for robustness. R4 in an internal trim-pot that can set the output voltage anywhere between 5 to 15 volts.

Read More Source :
http://members.tripod.com/michaelgellis/power4.html
Thank You

LM2577 6V to 12V 1A simple step-up dc converter

This step-up converter is intended for use in a '67 Citroen 2CV. This car, and I use the word loosely, has a 6V battery and won't support a modern radio that needs 12V. The circuit described here converts 6V to 12V at 1A sustained load current.To implement this, I have used the LM2577T-ADJ from National Semiconductor. It operates conform the given discription and is connected like so:

Read More Source:
Source: www.xs4all.nl/~odu/
Thank you.

ICL7660 DC to DC Converter input 5V to output +/-5V

Simple Circuit

Voltage Inverter, +5 to +/-5V, Input Voltage 1.5-10V, or Voltage Doubler to 18.6V

ICL7660 Features

• Simple Conversion of +5V Logic Supply to +/-5V Supplies
• Simple Voltage Multiplication (V_OUT= (-) nV_IN)
• Typical Open Circuit Voltage Conversion Efficiency 99.9%
• Typical Power Efficiency 98%
• Wide Operating Voltage Range
  • ICL7660 1.5V to 10.0V
  • ICL7660A 1.5V to 12.0V
• ICL7660A 100% Tested at 3V
• Easy to Use - Requires Only 2 External Non-Critical Passive Components
• No External Diode Over Full Temp. and Voltage Range

Please Read More Datashee:
http://www.ortodoxism.ro/datasheets/intersil/fn3072.pdf......Thks

LM2577 5V to 12V DC Converter step up Voltage Regulator

LM2577 (3A)

DC to DC step up voltage regulator.

Wide input voltage 3.5Vdc to 40Vdc.

This is Circuit DC to DC Converter Step up Voltage Regulator From 5V To 12V 1A Regulated Output.

Component list

- 2.2k 1/4W resistor

- 0.1uF capacitor

- 0.33uF capacitor

- 680uF 50V electrolytic capacitor

- 1N5822 high speed schottky diode (3A)

- wire coil inductor, 100uH

- "for LM2577-adj IC" 20k multi-turn variable resistor, set to ratio to R2=2k, R1=18k for voltage output of 12Vdc before soldering

Part number:

- LM2577-12 (12Vdc output)

- LM2577-15 (15Vdc output)

- LM2577-ADJ (1.23Vdc to 37Vdc output)

13.8V 40A Switching Power Supply By LM3524,LM324

This article was originally published (in a slightly modified form) in the QST magazine, December 1998 and January 1999, and in the Radio Amateur's Handbook, 1999. Visit the American Radio Relay League for information on these publications, and a world of ham radio related things!

Design decisions

There are several different topologies for switchers in common use, and the first decision a designer must take is which of them to consider. Among the factors affecting the decision are the power level, the number of outputs needed, the range of input voltage to be accepted, the desired tradeoff between complexity, quality and cost, and many more. For this power supply I decided to use the half bridge forward converter design. This topology connects the power transformer to a bridge formed by two power transistors and two capacitors. It is reasonably simple, puts relatively low stress on the power transistors, and makes efficient use of the transformer's magnetic capabilities.The second basic decision is which switching frequency to use. The present trend is to use ever higher frequencies. But by doing so it becomes more difficult to filter out the RF noise inevitably generated by the switching. So I decided to stay at a low switching frequency of only 25 kHz for the full cycle, which due to the frequency doubling effect of the rectifiers results in 50 kHz on the output filter.

For the main switching elements, bipolar transistors or MOSFETs can be used. Bipolars have lower conduction losses, while MOSFETs switch faster. As in this design I wanted to keep the RF noise at an absolute minimum, very fast switching was not desired, so I used bipolar transistors. But these tend to become too slow if the driving is heavier than necessary. So, if the transistors have to switch at varying current levels, the drive to them must also be varied. This is called proportional driving, and is used in this project.

The half bridge converter is best controlled by pulse width modulation. There are several ICs available for this exact purpose. I chose the 3524, which is very simple to use and easy to find. Any 3524 will do the job. It can be an LM3524, SG3524, etc.

This basically ends the big decisions. From now on, designing the circuit is a matter of calculating proper values for everything.

Read More Source :
http://ludens.cl/Electron/PS40/PS40.html...............................Thank You.

Switching Power Supply by IC UC3843 + IRF740

This is a Somewhat Experimental Circuit and I Especially designed this circuit for those persons that want to Dabble in Switching Power Supply Designs.

This Circuit is based on a UC3843 Integrated Circuit. It does Not allow for Feedback control of the output voltage. The output voltage is totally determined by the �Turns Ratio in Transformer �T1. The Useable, Continuous Power Output is approximatey 25 watts or so. It could be used as a small Power Supply or a Battery Charger. In the proto I made, T1 has a Primary Inductance of about 1 mH. This requires 33 turns of 26 or 28 AWG Wire wound on the Bobbin First. (About One Layer if you use the 28 AWG, or a Bit over one layer if you use the 26 AWG) To get this 1 mH inductance using this core, also requires this ferrite to have a total gap of 0.005 inches. Or 0.0025 gap on each leg of the core. I can Pre-Gap this for you if you buy the core and bobbin from me. The Supply voltage is 117 Volts AC. When Rectified it produces a DC Supply of about 165 Volts. The Output Voltage is basically determined by the Turns ratio to the primary winding and to that 165 volts. To Get out 12 Volts, you will require about 2.4 Turns on the Secondary. I used 3 Turns, just to make it easier. This Winding is Wound Over top of the Primary, Using a Good Insulation layer between it and the Primary. This Insulation Material should be for 3,600 Volts for shock hazzard safety. 165 / 33 = 5 Volts per Turn Therefore 12 \ 5 = 2.4 turns. However you can also use as many turns as you want, to get Whatever Voltage you desire. As another Example, If you wanted 30 volts out 30 / 5 = 6 Turns on this Secondary. On the transformer I made, I used a Bifular wound output to give me Full wave rectification using just two diodes. NOTE: Bifular Winding is Two Wires wound Simutanously, side by side, Than joined properly phased to give a Center tapped output. Or you could just wind a Single Output and use a Bridge rectifier. OR just a Single Diode, for Half Wave Rectification. Or No Rectification for an 80 Khz Output. These are some of your Choices to make. In the transformer, there is a 3rd winding. The 56 K, 2 Watt Resistor only supplies a Start Up power for the UC3843. Once the circuit is running, the Uc3843 actually gets its power from this 3rd winding. I used 6 turns of 28 AWG. It gets wound over the Secondary winding with a thin layer of insulating material between it and the output winding. Resistor �IX is a 1 or 2 watt Current Limit Resistor to protect the IC. NOTE: Current to the IC MUST NOT EXCEED 30 Ma. In the circuit I built, a �100 ohm resistor was used. But if in Doubt, use a somewhat Higher Resistance and than reduce it till you get a Reliable Starting when the 117 volts is applied to the circuit. (If this resistor is Too High in value, the circuit will somewhat Oscillate, giving a Pulsing output.) Materials and Parts.

Please read more :: http://www3.telus.net/chemelec/Projects/Switching-Power-Supply/Switching-Supply.htm

Switching Power Supply Regulator with LM2596 (3A)

DC to DC step down voltage regulator 3A
Wide input voltage 8Vdc to 40Vdc.

Part number:

- LM2596-3.3 (3.3Vdc output)

- LM2596-5.0 (5Vdc output)

- LM2596-12 (12Vdc output)

- LM2596-ADJ (1.23Vdc to 37Vdc output)

Component list

- 680uF 50V electrolytic capacitor

- 1N5824 high speed schottky diode (5A)

- Output 100V electrolytic capacitor (higher voltage, lower ESR)

330uF (for LM2596-3.3, LM2596-5.0)

180uF (for LM2596-12)

- wire coil inductor,

33uH (for LM2596-3.3, LM2596-5.0)

68uH (for LM2596-12)

Switching Power Supply Regulator with LM2575 (1A)

DC to DC step down voltage regulator.

Wide input voltage 8Vdc to 40Vdc.

Part number:

- LM2575-3.3 (3.3Vdc output)

- LM2575-5.0 (5Vdc output)

- LM2575-12 (12Vdc output)

- LM2575-15 (15Vdc output)

- LM2575-ADJ (1.23Vdc to 37Vdc output)

Switching Power Supply Regulator with LM2576 (3A)

LM2576 (3A)

DC to DC step down voltage regulator.

Wide input voltage 8Vdc to 40Vdc.

Part number:

- LM2576-3.3 (3.3Vdc output)

- LM2576-5.0 (5Vdc output)

- LM2576-12 (12Vdc output)

- LM2576-15 (15Vdc output)

- LM2576-ADJ (1.23Vdc to 37Vdc output)

IC555 Timer 5 to 30 Minute

Circuit : Andy Collinson
Email: anc@mitedu.freeserve.co.uk

Descriptipn:
A switched timer for intervals of 5 to 30 minutes incremented in 5 minute steps.

Notes:
Simple to build, simple to make, nothing too complicated here. However you must use the CMOS type 555 timer designated the 7555, a normal 555 timer will not work here due to the resistor values. Also a low leakage type capacitor must be used for C1, and I would strongly suggest a Tantalum Bead type. Switch 3 adds an extra resistor in series to the timing chain with each rotation, the timing period us defined as :-

Timing = 1.1 C₁ x R₁

Note that R₁ has a value of 8.2M with S3 at position "a" and 49.2M at position "f". This equates to just short of 300 seconds for each position of S3. C₁ and R₁ through R₆ may be changed for different timing periods. The output current from Pin 3 of the timer, is amplified by Q1 and used to drive a relay.

Parts List:
Relay 9 volt coil with c/o contact (1)
S1: On/Off (1)
S2: Start (1)
S3: Range (1)
IC1: 7555 (1)
B1: 9V (1)
C1: 33uF CAP (1)
Q1: BC109C NPN (1)
D1: 1N4004 DIODE (1)
C2: 100n CAP (1)
R6,R5,R4,R3,R2,R1: 8.2M RESISTOR (6)
R8: 100k RESISTOR (1)
R7: 4.7k RESISTOR (1)

Source :: http://www.zen22142.zen.co.uk/Circuits/Timing/5_30timer.htm