Power supply 220/0-30 volts 5 amps with digital indication of voltage and current. Encyclopedia of radio electronics and electrical engineering

Encyclopedia of radio electronics and electrical engineering / Power Supplies

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The described power supply is designed for use in an amateur radio laboratory. Despite the fact that many diagrams of such devices were printed in amateur radio literature, this power supply is not picky about specialized microcircuits and imported elements. At present, the issue of acquiring chips is still relevant, and in some regions it is problematic to get them. This power supply is an upgrade to the power supply described in ( II ). The power supply is assembled only from available parts.

Power supply specifications:
The output voltage is adjustable from 0 to 30 V.
Output current 5 A.
The voltage drop at a current of 1 A to 6 A is negligible and does not affect the output.

The power supply circuit is shown in fig. 1 below

Rice. 1 (click to enlarge)

This power supply contains three main nodes: an internal network power node VD 1-VD 4, C 1-C 7, DA 1, DA 2, an overload and short circuit protection node VS 1, R 1-R 4, VD 3 and the main node - adjustable voltage regulator VT 2- VT 7, VD 4- VD 5, R 4- R 14, C 8.

And also a digital panel is added to the power supply, i.e. display unit, which is shown in Fig. 5.

The internal network power supply unit is built according to the traditional scheme with a network transformer T1.

The protection node has no features. The current sensor was calculated for a current of 3A, but it can also be calculated for 5A. For a long time, the power supply was operated with a current of 5A. There were no failures in his work. Diode HL 1 indicates an overcurrent or short circuit in the load.

The main node is an adjustable voltage regulator of a compensation type. It contains an input differential stage on transistors VT 5, VT 7, two gain stages on transistors VT 3 and VT 2, and a control transistor VT 1. Elements VT 4, VT 6, VD 4, VD 5, R 5 - R 8, R 10 form current stabilizers. Capacitor C8 prevents self-excitation of the block. Because transistors VT 5 and VT 7 were not selected the same, then there is a certain "zero offset" of this cascade, which is the minimum voltage of the power supply. Within a small range, it is regulated using a tuning resistor R 7 and, in the author's version, it reached approximately 47 m V at the output of the power supply. The output voltage is regulated by the resistor R 13. The upper limit of the voltage is adjusted by the trimming resistor R 14.

Fig. 2

Construction and details. The power of the transformer T1 must be at least 100 - 160W, the winding current II - at least 4 - 6A. Winding current III - not less than 1 ... 2A. The RS 602 diode assembly can be replaced with an RS 603 assembly or diodes rated for 10A current. The VD 2 diode bridge can be replaced with any of the KTs402 - KTs405 series, which are glued from the side of the printed tracks, mirrored to the C1 capacitor and connected by flexible conductors to the VD 2 contact pads on the board. Transistor VT 1 should be installed on a heat sink with an area of ​​at least 1500 cm 2. The area of ​​the radiator is calculated by the formula S = 10 I n ( U in. - U out. ), where S is the surface area of ​​the radiator (cm 2 ); I n - maximum current consumed by the load; U in. - input voltage (V); U out. - output voltage (V).

Transistor KT825A - composite. It can be replaced by a pair of transistors, as shown in Figure 2.

These transistors are connected in a Darlington circuit. Resistor R 4 is selected experimentally, according to the protection operation current. Resistors R 7 and R 14 - multi-turn SP5-2. Resistor - R 13 any variable with a linear functional characteristic (A). In the author's version, a 3K - 2,2% variable resistor PPB-5A is used. Chips DA 1 and DA 2 can be replaced with similar domestic KR142EN5A and KR1162EN5A. Their power allows a stabilized voltage of ± 5 V to power external loads with a current consumption of up to 1A. This load is a digital panel, which is used for digital indication of voltage and current in power supplies. If you do not use the digital panel, then the DA 1 and DA 2 chips can be replaced with the 78 L 05 and 79 L 05 chips.

The printed circuit board of the power supply is shown in fig. 3 and fig. 4.

Fig. 3

Fig. 4

Establishment

Since the design is located on two printed circuit boards, the power supply is first set up, then the digital display unit.

Power unit. With serviceable parts and no errors in installation, the device starts working immediately after switching on. Its establishment consists in setting the necessary limits for changing the output voltage and the current of the protection operation. The sliders of the resistors R 7 and R 13 should be in the middle position. Resistor R 14 on a voltmeter achieves a reading of 15 volts. Then the engine of the resistor R 13 is moved to the minimum position and 7 volts is set by the voltmeter with the resistor R 0. Now the engine of the resistor R 13 is moved to the maximum position and the voltage of 14 volts is set by the resistor R 30 on the voltmeter. Resistor R 14 can be replaced by a constant one, for this, a place is provided on the board - resistor R 15. In the author's version, this is a 360 Ohm resistor. The size of the printed circuit board of the power supply is 110 x 75 mm. Diodes VD 3 - VD 5 can be replaced with KD522B diodes.

Digital panel consists of an input voltage and current divider, a KR572PV2A microcircuit and an indication of four seven-segment LED indicators shown in Figure 5. Resistor R 4 of the digital panel consists of two pieces of constantan wire ? =1mm and 50mm long. The difference in the value of the resistor should exceed 15 - 20%. Resistors R 2 and R 6 brand SP5-2 and SP5-16VA. Voltage and current indication mode switch type P2K. The KR572PV2A microcircuit is a 3,5 decimal digit converter operating on the principle of sequential counting with double integration, with automatic zero correction and input signal polarity detection.

For indication, imported LED seven-segment indicators KINGBRIGT DA 56 - 11 SRWA with a common anode were used. Capacitors C2 - C4, it is desirable to use film type K73-17. Instead of imported seven-segment LEDs, domestic ones with a common anode of the ALS324B type can be used.

Fig. 5

Digital voltage and current indication panel

After turning on the power and error-free installation, with serviceable parts, the display segments HG 1-HG 3 should light up. A voltage of 2 volt is set by the voltmeter with resistor R 36 on leg 572 of the KR2PV1 microcircuit. The power supply is connected to the legs (a) and (b). A voltage of 5 ... 15 volts is set at the output of the power supply and a resistor R 10 is selected (roughly), replacing it, for a while, with a variable. Using resistor R8, a more accurate voltage reading is set. After that, a variable resistor with a power of 10 ... 30 watts is connected to the output of the power supply, the current is set to 1A using the ammeter and the value on the indicator is set with resistor R 6. The reading should be 1,00. At a current of 500 mA - 0,50, at a current of 50 mA - 0,05. Thus, the indicator can indicate current from 10mA, i.e. 0,01. The maximum value of the current indication is 9,99A.

For a larger indication capacity, you can apply the circuit on KR572PV6. The size of the printed circuit board of the digital panel is 80 x 50 mm, fig. 6 and fig. 7. Contact pads U and I on the printed circuit board of the digital panel, using flexible conductors, are connected to the points of the corresponding indicators HG 2 and HG 1. The KR572PV2A microcircuit can be replaced with an imported ICL7107CPL microcircuit.

Fig. 6

Fig. 7

Literature

1. Stabilized current rectifier type TES 12 - 3 - NT. Gortse Delchev. Bulgaria. 1984
2. A. Patrin Laboratory power supply 0 ... 30 V. RADIO No. 10 2004, p.31.
3. Switching power supply based on PC. S. Mityurev. RADIO №10 2004 p.33.
4. Anufriev A. Network power supply for a home laboratory. - Radio, 1992, N 5, S.39-40.
5. Voltage stabilizer with double protection Yu. KURBAKOV, RADIO February 2004 p.39.
6. Biryukov S. Portable digital multimeter. - To help the radio amateur, vol. 100 - DOSAAF, 1988. p. 71-90.
7. Biryukov S. Digital devices based on MOS integrated circuits. - M.: Radio and communication, 1990:1996 (second edition).
8. Radio N 8 1998 p.61-65

Author: Digital Voltmeter; Publication: cxem.net

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