Voltage stabilizer 8-16 volts 1 ampere on the K174UN7 chip. Encyclopedia of radio electronics and electrical engineering

Encyclopedia of radio electronics and electrical engineering / Surge Protectors

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Very popular just some 12-15 years ago, the K174UN7 chip (import analogue - TBA810S), which is an integrated audio frequency power amplifier, is currently almost never used in the construction of UMZCH, since by modern standards it provides low sound quality. But radio amateurs continue to "ruthlessly" exploit this microcircuit, creating various interesting devices on its basis [1,2].

In [3], an article was published about the original voltage regulator on K174UN4A. With a detailed analysis of the device circuit, it became clear that a similar stabilizer can also be built on a more powerful K174UN7 chip. However, an attempt to mirror the found circuit design from K174UN4A to K174UN7 did not lead to the expected result - the stability of the output voltage turned out to be low, so the circuit was redesigned, and in the end what you see in Figure 1 turned out.

Rice. 1. Schematic diagram of the voltage regulator (click to enlarge)

The compensation voltage regulator on the K174UN7 chip operates in the input voltage range of 8 ... 16 V (at U_O= 5 V) and provides a load current of up to 0,5 A. When the input voltage increases from 8 to 16 V, the output voltage changes by no more than 10 mV (at a load current of 0,3 A). The power dissipated by the microchip installed on the heat sink can reach 5 watts.

The output voltage of the device is determined by the operating voltage of the connected zener diode (VD1, VD2) plus 1 ... 1,5 V. Capacitor C4 prevents self-excitation of the microcircuit, resistor R3 ensures self-starting of the stabilizer when a low-resistance load is connected.

This stabilizer does not have an electronic overload or output short circuit protection system. To protect the microcircuit from damage, an inexpensive self-resetting fuse FU1 from the BOURNS company for 0,65 A of the MF-R065 type was used [4]. If desired, electronic protection can also be introduced, as described in [3].

The design can use resistors MLT, C1-4, C2-23 and others. Capacitor C4 - K73-17, K10-17, KM-5. The rest of the capacitors are oxide, K50-35, K50-16. Zener diodes VD1, VD2 are selected so as to obtain the desired output voltage. In place of VD1, you can try the zener diode KS126K, KS126L, KS175A, KS182A, KS482A. To obtain an output voltage of 5 V, VD2 is selected from KS126V, KS126G, KS139A, KS407A, KS407B. If, in addition to the voltages of 5 V and 9 V, one more output voltage is required, for example, 12 V, then you need to select a copy of the zener diode from the types D814V, D814G, KS210Zh, KS211Zh and set the SA1 switch to a larger number of positions. The circuit of the highest voltage zener diode should not open, otherwise, at the moment of switching SA1, a voltage surge may occur at the output, close in amplitude to the input voltage.

The HL1 LED, designed to indicate normal operation, can be taken of any type from AL102, AL307, KIPD35, KIPD40 and others.

The microcircuit must be installed on a ribbed duralumin heat sink. A standard ribbed or pin heat sink, which is usually equipped with K174UN7, K174UN9 microcircuits in UMZCH TVs and tape recorders, will not be enough to ensure the normal operating temperature of the IC at maximum input voltage and load current. Two such heatsinks can be used if each of them is attached to one of the heat sink flanges of the IC. For long-term reliable operation of the stabilizer, one should strive to ensure that the temperature of the microcircuit case does not exceed 50 ° C during the most severe operating mode.

The length of the FU1 fuse leads from the soldering point to the body must be at least 10 mm. So that when the load is connected, self-excitation of the microcircuit does not occur, the signal and power circuits of the common wire must be made separate and connected to each other at one point. The circuits for connecting capacitors C1, C5 to the microcircuit should be as short as possible. The output current of the stabilizer can be increased to 1 A, provided that the power dissipated by the microcircuit does not exceed 5 watts.

Literature

1. I. Alexandrov. Voltage polarity inverter. - Radio, 1993, N11, p.38.
2. I. Nechaev. Generator 34 on the K174UN7 chip. - Radio, 2002, N4, p.52.
3. I. Nechaev. Chip K174UN4A - DC voltage stabilizer. - Radio, 1993, N9, p.40.
4. BOURNS MULTIFUSE resettable fuses. - Radio, 2000, N11, S.49...51.

Author: A. Butov, village of Kurba, Yaroslavl region; Publication: cxem.net

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