3.3.9. Power Source - SPS

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Of course, the energy source for computer networks is the town, but not in its original form, but transformed into direct current. Different conceptions DCS in a different way to solve casing problems of energy transformation. Simpler systems have a transformer, which reduces the line voltage to the required extent, and then corrects. But for larger forces such concepts requires large transformers with heavy iron cores. Therefore applies a different way of transformation. AC line voltage is rectified directly into DC and the rectified voltage passed through the transformer turns back into AC, but much higher frequencies (above 15'000 Hz), and that the cross-section of the iron core transformer is inversely proportional to frequency, bulky transformer reduces the size of the slightly larger than a box of matches. Then decreased again transformed AC voltage corrects for work purposes assemblies. These adapters are called IMPULSE RECTIFIERS (SPS - Switching Power Supply). They are often called PSU (Power Supply Unit) because they tend to be designed as a separate unit, almost standardized sizes, which features depend on the needs.

Example XIV

Basic wiring diagram and an example of the power unit design circuits PC computer system.

 Electrical scheme of SPS
Figure** 3.3.38 Basic electric scheme of the SPS / Construction. ( +/- )

Basic wiring diagram is shown in Figure 3.3.38a shows that the adapter is designed. AC line voltage, available via 'RM0' port after filter 'F' diode bridge rectifies 'D' and filtered steam condenser 'C'. Rectified voltage across the resistor 'R' initial powered electronics to the controller, which over the transformer 'TR1' generates a basic control voltage +5 V SB (Stand-by) for the other controller and devices that allow the computer (button 'B', network card, keyboard, mouse and the like), as well as additional power (Up) for the control and excitation circuits. Excitation circuits via the signal from the high frequency clock generator, from tens of kHz, make it possible through switching electronic components 'T1-D1' and 'T2-D2' excited with 'T3' and 'T4' through transformers 'TR2', performed alternately monitored leakage current caused by the discharge pair of condensers 'C' through the primary coil 'P' of transformer 'TR3' very great frequency. In secondary 'S' of transformer 'TR3' induces alternating currents of very high frequency, which allows small dimensions of the rectifier and 'LC' filter elements for each required DC voltage. Due to very high operating frequency, ferrite core transformers are very small cross-section, and requires a very small number of windings of copper wire in the primary and secondary winding about transforming power. Cheaper versions pulse rectifier use electronics with which to 'TR3' performs high-frequency leakage current through the primary coil 'P' using one electrolytic capacitors 'C' and one interrupted transistors, unlike the version shown in Figure 3.3.38b.

Combining the power of microprocessors, graphic cards, disk and optical devices, working memory cooling fan and other devices and possibly inserted card, one has to provide power from 200 W to over 1000 W. So, for the demanding computing system to ensure quality source of energy, with enough terminal connector. In most cases, the manufacturers offer casing for the computer and power supply are integrated. However, the quality of supply are usually a separate product. So it's good to find enough hard and ventilated computer case with sufficiently 5.25" and 3.5" external and internal slots for disk devices, optical devices, and other accessories, and has the option of ventilation for at least the front and rear, and for it to incorporate quality fans. Power must provide power to all devices that serve them depends on how much he should be declared force. On the Internet, there are seats that allow fast calculation of required power supply or software support designed specifically for this purpose (PSU Wattage Calculator). The best choose of a power source is on the basis of tests in magazines and checking possible choice for users who already use. The power source indicates that the body only, and the power source must have a well-resolved cooling.

But until now, it was stated description of the home or office computer user (PC). But the casing and power supplies for servers are quite something else. One well casing will weigh more than 30 kg, will have a motherboard that supports multiprocessing, the possibility of changes in the work of 5-10 discs (hotplug), 10-15 fans that are easily interchanged and plastic guides for channeling air flow through the casing and in case of a sudden rise in temperature will trigger a special turbines that will generate a powerful airflow. Graphics support is basically weak (a server is not needed). Power is typically duplicated in case of cancellation of the one system stops working. Drives are in a RAID system supported hardware device, which is a great guarantee to preserve data. Of course, in such a computer is built into the DAT system for 'backup' data. Once on the server is basically no longer excluded.

Example XV

Connection assignment of the connectors for power supply circuits PC computer system type AT and ATX-2 (ATX12V) version 2.2.

For PC systems parameters rectifiers are standardized, i.e., the number and arrangement of contacts (pinout), and even the color output guides. AC adapter included with the computer chassis, power ranging from 150-1000 W, and a four or five-way output voltages such as the AC adapter to the AT or ATX (ATX-2) MPC (Main Power Connector) connector to the motherboard to shown in the following tables:

AT - MPC Connector
  Pin Purpose Color
P8 1 PW-OK orange
2 +5 V DC red
3 +12 V DC yellow
4 -12 V DC blue
5 GND black
6 GND black
P9 1 GND black
2 GND black
3 -5 V DC white
4 +5 V DC red
5 +5 V DC red
6 +5 V DC red
ATX (ATX-2*) - MPC Connector
Pin Purpose Color Pin Purpose Color
1 +3.3 V DC orange 13 +3.3 V DC orange
2 +3.3 V DC orange 14 -12 V DC brown
3 GND black 15 GND black
4 +5 V DC red 16 PS-ON green
5 GND black 17 GND black
6 +5 V DC red 18 GND black
7 GND black 19 GND black
8 PW-OK gray 20 -5 V DC blue
9 SB purple 21 +5 V DC red
10 +12 V DC yellow 22 +5 V DC red
11 +12 V DC* yellow 23 +5 V DC* red
12 ATX-2*detect white 24 GND* black

Guide labeled PW-OK is used as a surveillance source and if all the output voltages are stabilized in order to +5 V DC motherboard provides information that the system can run. PS-ON is used to control turning on and turning off the computer, and the SB is available for stand-by mode the computer. All these controls are initiated by a voltage of +5 V DC. ATX connector can be plugged into the slot for ATX-2 connector to not use pins 11, 12, 23 and 24. If PC-ON connector (green colored) connected to any port density (GND) excludes the mutual control motherboard - power supply, and power supply can be used independently as a separate source for another purpose, such as a power supply in the chassis which is incorporated into more devices than usual, as a source for additional disk and optical devices, of course, without the use of MPC connectors. Instead of bridging connections is better to use for this purpose is made MPC splitter that allows properly connect two power supplies in the system.

All output voltages are stabilized and rectifier has electronics that ga in case of a short circuit at the output terminals off. Rectifier output either the declared value with changes in input voltage range of 200-260 V (Europe). At the rectifier cabinet is mounted main switch computers, voltage to 220 V to power the monitor and switch to switch the input voltage of 110 V / 220 V. Before the first turn on the computer to check the position of this switch.

For systems with 'Pentium 4' CPU and graphics cards more spending, along with the existing ATX connector adds another connection forms as AT-P8, AUX connector (+5 V and +3.3 V). The newer concept of stable power processors through separate power stabilizer on the motherboard requires only a source of +12 V to be secured from the square connector rather smaller ATX 2×2 Additional connector of the same form is used to power the graphics card. In this way relieves the power contacts in the slots (slot s) motherboard from excessive loads. The concept of CPU power connector ATX 2×2 (P4) displacing the AUX concept.

AUX Connector
Pin Purpose Color
1 GND black
2 GND black
3 GND black
4 +3.3 V DC orange
5 +3.3 V DC orange
6 +5 V DC red
ATX P4 2×2 Connector
Pin Purpose Color Pin Purpose Color
1 GND black 3 +12 V DC yellow
2 GND black 4 +12 V DC yellow

Typical consumption is one ATX12V source 'MS 400W ATXP4' shown in the following table:

+3.3 V + 5 V +12 V -12 V - 5 V +5 V SB COM P-ON P-Good
28 A 30 A 16 A 0.8 A 0.5 A 2 A > 0.5 A > 0.5 A > 0.5 A

With these connectors, wires coming from the rectifier with one or two small FDPC (Floppy Drive Power Connector) connectors for floppy disk devices, and more PPC (Peripheral Power Connector) connectors for peripheral devices like the HDD (hard disk drive), CD-DVD (optical devices ). If there is not enough PPC connectors for devices very well could serve splitters. Connectors (pinout) devices are shown in the following tables.

FDPC Connector
Pin Purpose Color
1 +5 V DC red
2 GND black
3 GND black
4 +12 V DC yellow
PPC Connector
Pin Purpose Color
1 +12 V DC yellow
2 GND black
3 GND black
4 +5 V DC red

The newer and more demanding with regard to consumer PC systems have stronger power than previously described, the larger extra connector on the motherboard to the CPU power, and additional connectors for the graphics card, as specified by the ATX12V version 2.3. Typically, these are the connectors with 6 (PCI-E 2×3) or 8 (EPS 2×4) PINs, which ensures supply of +12 V DC, with GND line for each power line, according to the following tables.

PCI-E 2×3 Connector
Pin Purpose Color Pin Purpose Color
1 +12 V DC yellow 4 GND black
2 +12 V DC yellow 5 GND black
3 +12 V DC yellow 6 GND black
EPS12V 2×4 Connector
Pin Purpose Color Pin Purpose Color
1 GND black 5 +12 V DC yellow
2 GND black 6 +12 V DC yellow
3 GND black 7 +12 V DC yellow
4 GND black 8 +12 V DC yellow

Sometimes 6 pin connector have addition of another two-pin for GND (6+2). How randomly to avoid confusion when connecting individual connectors for devices, some bearing pin connectors are trapezoidal in shape. So neither one connector can not be unassigned his cradle squeeze 'force'. EPS connector can be created and doubled as the P4 connector.

All pins on connectors are normalized to the operating current of 6 A, and hence a large number of pins the same color for the same voltage for different types of connectors. Slightly smaller SATA power connectors that replace PPC connectors in newer hardware derivatives of these devices are connected to PPC connector via an adapter or power source has additional connectors just for SATA devices. Number of SATA connector pins is increased (15), and several of them for the same purpose for increased security with respect to 'delivery' energy device, and it is important that the standard applies to the disc width 2.5" and 3.5", and home and portable computers. Besides the aforementioned SATA standard provides for the fifth power source line for +3.3 V regarding future applications. Standardized operating current per pin SATA is 1.5 A.

SATA HDD / CD-DVD Connector
+3.3 V DC GND +5 V DC GND NA GND +12 V DC
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

When selecting rectifiers should be careful. The first step is to calculate the total consumption of the components inside the computer, a microprocessor, a graphics card, drives, cooling fans and more. Calculation should add 25% for possible upgrades. It is then necessary to choose products that can really offer rectifier with necessary requirements. Although the adapter can cancel the line voltage changes in certain proportions, you had better pay attention to the size and stability of the dc voltage. Most common problems are a source of +12 V DC, which is either unstable or when burdened falls below 11.5 V DC which automatically leads to unstable work computers. Zeroing change the line voltage in case of need to give up the source of uninterruptible power supplies (UPS).

Incidentally, these connectors are often called-MOLEX connectors, according to one of the most important manufacturer that worked. This term is often used for all of the connectors in the PC, although usually only applies to PPC connectors PATA devices group. Connector is often used to extend the existing HDD connectors (molex splitter - one male to two female connectors) for connecting additional devices or chassis fan.

 SPS power source
Figure* 3.3.39 PC adapter. ( +/- )

According to all of the above it can be concluded that, regardless of the individual standards (AT, ATX and ATX-2) has a plethora of ports that the power can go out and still using separator can increase their number. Regardless of the fact they have one thing in common, all the connectors are physically different profiled (Figure 3.3.39b) so that it can not happen to be one kind of connector plug into the connector of another origin and use for other purposes. It shall also take into account the type of motherboard because the MPC standards described each connector is designed specifically for different standards of motherboards.

An important part of the rectifier cooling fan, which allows components in the rectifier and the exchange of air in the computer case. In the event that there is a place in the computer case for an additional fan, and less expensive with an extra fan cooler is built on microprocessors and graphics cards that have a higher consumption. Better rectifiers have two fans, one for intake air from the enclosure and the other to the back of the computer to exhaust heated air, as shown in the example in Figure 3.3.39. The performances are quite varied. Be sure to watch the chosen adapter supports with all its feeder ports selected motherboard and other devices, especially newer types like SATA-II.

It is good if the SPS has built-in electronics for active power factor correction (Active PFC). It is the ability of energy sources (SPS) to control its load in order to obtain the best efficiency. In most applications, the active PFC (power factor correction) controls the current load in a way that the current waveform is proportional to the supply voltage waveforms (sine wave). The purpose of monitoring the power factor is that more apparent power sources closer to the actual force required to achieve and the voltage and current in phase and hence the reactive power is very small. Thus, PFC allow efficient delivery of electricity to your computer.


It is important to realize that over several contacts (as PW-OK) supervises state voltage source rectifier. This should mean that if the voltage is incorrect, set the motherboard logic signal electronic rectifiers, which should prevent the delivery of power and will not damage the motherboard. However, in practice this is not usually the case; defective rectifier typically has resulted in the suffering of some of the components of the computer including the motherboard. Motherboards are the most common victim of bad or faulty rectifier computer.

Pulse rectifier does not apply only to computer components, but is also used as an energy source for other types of devices, such as adapter shown in Figure 3.3.38c, which supplies ADSL modem. Outputs a 12 V DC voltage with a maximum current of 1.5 A. On the left side of the cabinet in the picture is the part that belongs to the line voltage is 220 V AC, see the heatsink below which is a pair of capacitors, rectifier diodes, switching transistor, and a small transformer. On the right side of the cabinet as low voltage rectifier elements, i.e. the part that relates to the output of 12 V DC; toroidal ferrite chokes, capacitors and transistors for voltage stabilization. This kind of rectifier is growing in popularity in gear.

So, notebooks have a separate power source in the form of a small plastic box that has a connection to the city's network, and its output is a DC voltage that is supplied with the laptop. The problem arises when such SPS universal adapter and works in the range of 110-220 V AC, or 'covers' U.S. and European markets. If it works on 220 V and in addition to the frequency 50 Hz, will inevitably be a very warm, especially because of less frequent city network (American standard voltage is 110 V AC / 60 Hz). If possible it is better to take a AC adapter designed specifically for the European market because it is much less heat, and thus the probability of failure is significantly lower.


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