Power filter for HDD. Encyclopedia of radio electronics and electrical engineering

Encyclopedia of radio electronics and electrical engineering / Computers

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The information capacity of modern HDDs is growing rapidly, which requires from their manufacturers the highest precision and quality in the manufacture of mechanical components and the improvement of the electronic components of HDDs. Today, HDDs have become very sensitive to the quality of the voltage supplying them. At the same time, the amplitude of periodic or random pulsations, for example, in the +12 V circuit of a computer, for a number of reasons, can reach hundreds of millivolts and even units of volts. This can most likely lead not only to errors in writing and reading information, but also to damage to electronic components. Although hard drives are relatively inexpensive, their failure can lead to the loss of not only time, but also valuable information, which for some reason does not have a backup copy.

If, according to the simple scheme shown in Fig. 1, make a hard drive power filter, then the probability of complete or partial damage to the drive connected through this filter to the computer's power supply is significantly reduced.

Rice. 1. HDD power filter circuit

The +5 V voltage from the PSU output is supplied to the XS1 connector connected to the HDD through the LC filter C1L1C4C7. Voltage + 12 V is supplied to the same connector through the LC filter C2L2C5C8C9. The HL1 LED glows red when there is a voltage of +5 V at the filter input, and HL2 glows yellow when there is a voltage of +12 V. The colors of the LEDs are not chosen by chance, they correspond to the standard colors of the connecting wires through which +5 V voltage is supplied to various components of the computer and +12 V from the PSU. Powerful zener diodes VD2 and VD4 limit the voltage at the filter output in the event of a power supply failure, which reduces the likelihood of damage to the HDD.

Although many modern computer motherboards can independently control the speed of the fans connected to them, depending on the ambient temperature and the load on the processor and video card, there may not be enough connectors on the motherboard necessary to connect all the fans installed in the computer. Therefore, together with the filters, the proposed device has an additional fan control unit.

At the moment the power is turned on, the capacitor C3 is discharged, therefore, a voltage of about 1 ... 2 V is set at the output of the voltage follower assembled on transistors VT11,2 and VT11,5. The fan connected to this output starts to work almost at full power. As the capacitor C3 is charging, the voltage at the follower output is gradually reduced to approximately 7,5 V. The fan speed and the acoustic noise generated by it are reduced.

The steady value of the voltage supplied to the fan depends on the ratio of the resistance of the thermistor RK1 (with negative TCR) and the resistance of the resistor R3. With an increase in the temperature of the environment in which the thermistor RK1 is located, the supply voltage of the fan and its rotational speed increase. The power supply of the fan at the time of switching on with a voltage increased relative to the reduced operating voltage ensures its more confident start.

Diode VD1 provides fast discharge of capacitor C3 after power off. Resistor R5 takes on a significant part of the load current, which would otherwise flow through transistor VT2, which facilitates the operation of this transistor.

All parts of the device (except LEDs) are installed on the circuit board shown in fig. 2. Wired from the back side. The board is placed in a polystyrene case from a car alarm. You can also use a rectangular case from a surface-mounted RJ11 telephone socket.

Rice. 2. Device circuit board

Inductors L1 and L2 are wound on rings of size 16x10x5 made of ferrite 2000NM. Their windings contain 21 turns of insulated stranded installation wire with a copper cross section of 0,85 mm². You can also use other chokes with an inductance of 100 ... 1000 μH with a winding resistance of not more than 0,03 Ohm, designed for a direct current of at least 2 A. For example, ring chokes from car radio power filters are suitable. Chokes are glued to the circuit board with hot glue.

Fixed resistors - small-sized any type. The author found a NTC thermistor in the power supply of a faulty LCD TV. Another small one with a resistance of 8 ... 12 kOhm at room temperature is also suitable.

The device was tested with computer fans with an operating voltage of 12 V and a current consumed at this voltage of 0,09 ... 0,6 A. If a fan cooling the HDD is connected to it, then the RK1 thermistor can be attached to the aluminum case through an insulating gasket HDD, when the temperature of which rises, the fan will increase the supply of cooling air. When fixing the thermistor, try not to put pressure on the top cover of the HDD case and do not accidentally glue the hole of the air filter filter on it.

Capacitors C1, C2, C7 - ceramic, C3 - C6 - oxide aluminum or tantalum, C8 and C9 - oxide tantalum for surface mounting.

Instead of a protective zener diode P6KE12A, you can use 1SMA12AT3, 1SMA13AT3, P6KE13A or domestic D815D. Diode VD3 is designed to increase the total operating voltage of the protective circuit up to 13...13,5 V at a current of 1...10 mA. Instead of the 1N4001 diode, you can install any of the 1N4001 - 1 N4007, UF4001 - UF4007, 1 N5401 - 1 N5408, KD243, KD247, KD226 series. With protective zener diodes for voltage 13 V, this diode is not required.

Zener diode 1SMA5.0AT3 is replaced by 1N5339 or domestic D815A. The voltage drop across the zener diode VD2 at a current of 1 ... 20 mA should be 5,4 ... 5,8 V. If necessary, it can be increased by 0,4 ... 0,6 V by connecting a rectifier diode in series with this zener diode , as it is done in the +12 V circuit.

Diode 1N4148 can be replaced by any of the KD510, KD521, KD522, 1N914, 1SS244 series. LEDs are suitable for any type, preferably the same glow colors as indicated in the diagram.

The KT816B transistor is replaced by any of the KT816, KT9170, 2SA928, 2SA931 series. Instead of KT3102E, a transistor from the KT3102, KT342, KT6111, KT6113, KT645, BC547, SS9014, 2SC1815 series is suitable. It is desirable to select transistors with the largest possible value of the base current transfer coefficient.

The MOLEX-8981 (XP1) connector for connecting the filter to a computer PSU was removed from the MOLEX-SATA adapter. Connecting wires with a copper section of 0,75 mm are soldered to the contacts of this connector.². Adapters for powering HDD with aluminum stranded wires should not be used [1]. If several hard drives are installed in the computer, then it is advisable to make a separate filter for each of them, and not use splitters.

Additional HDD power filtering is just one of the measures to improve the reliability and stability of the computer. It may be advisable to install filters similar to the one described in the +12 V circuit of the additional power supply of the video card, in the +12 V circuit of the switching voltage regulators of the processor supply. It is also useful to install additional smoothing capacitors in parallel with the PSU outputs +3,3 V, +5 V and +12 V (orange, red and yellow wires) or replace the capacitors already installed in these circuits with a larger capacitance.

All oxide capacitors with the slightest sign of swelling of the top cover or with heating noticeable to the touch [2] must be replaced without fail.

Literature

1. Butov A. Completion of connectors for computer power supplies. - Radio, 2009, No. 8, p. 24.
2. Grishin A. Reducing heating of filter parts in processor power circuits. - Radio, 2004, No. 1, p. 23, 24.

Author: A. Butov

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