Multichannel voltage stabilizer on the BA4911 chip. Scheme, description

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Multichannel voltage stabilizer on the BA4911 chip. Encyclopedia of radio electronics and electrical engineering

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Encyclopedia of radio electronics and electrical engineering / Surge Protectors

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The world of linear integrated voltage regulators is not limited to such popular series of microcircuits as KR142ENxx, x78xx, x79xx, their numerous "relatives" and "clones". In their shadow, there are many other, "untwisted" series of integral stabilizers, often with advanced service capabilities or unique parameters.

For example, Rohm produces a wide range of linear stabilizers (circuits of the Вхххх series), among which you can find both analogues of the 78th series (BA178xxT / FP) and similar stabilizer microcircuits with a low voltage drop (BAxxBCOFPrr, BAxxBCOWFP / T series), Low Dropout (BHxxFBIWxx) and High Speed, Multichannel, Special Purpose CMOS Regulators.

The main characteristics of some series of linear stabilizers from Rohm are presented in tables 1-3.

(click to enlarge)

Rohm's range of voltage stabilizer ICs includes multi-channel switching regulators designed for automotive audio applications.

For example, the BA4911 microcircuit, produced in the S1P-M12 package (Fig. 1).

Multichannel voltage stabilizer on the BA4911 chip

This microcircuit is a 5-channel voltage stabilizer, 4 of which are controlled, with a small voltage drop between input and output. The microcircuit also has two controlled switches for switching the supply voltage.

The maximum power dissipated by this chip can be up to 3W (with heatsink). Of course, this is not so much compared to some other linear regulators, but it is quite enough, for example, to power homemade watch radios, computer peripherals, analog and digital measuring instruments, for use in chargers or in children's toys.

Scheme of a 5-channel voltage regulator on a microcircuit. BA4911 is shown in Fig.2.

Multichannel voltage stabilizer on the BA4911 chip

In order to unify the design, the stabilization unit on the microcircuit. VA4911 is connected to a voltage rectifier. The mains voltage (220 V) through the closed contacts of the switch SA1 and the fuse FU1 is supplied to the primary winding of the step-down transformer T1. The open-circuit voltage on its secondary winding is about 15 V. Through the self-healing fuse FU2, the alternating voltage is supplied to the Schottky bridge rectifier VD1 ... VD4. The use of such diodes reduces the power losses in the rectifier. Varistor RU1 protects the transformer windings and diodes from breakdown during high-voltage impulse noise in the network, the amplitude of which can reach 5...20 kV. The FU2 polymer resettable fuse protects the transformer from overload. The ripple of the rectified voltage is smoothed out by the capacitor. Sat.

The supply voltage is supplied to pin 7 of DA1. The microcircuit has two channels of group control of output voltages. The node consisting of R1, VD5, C7, R2 is turned on so that when the input supply voltage is less than 9,5 V, there is no voltage at the controlled outputs DA1.

This mode of operation of the stabilizer allows you to prevent deep discharge of batteries if DA1 is powered by a 12-volt battery.

Capacitor C7 delays the appearance of output voltages (by about 200 ms). which can be useful for the correct start of microprocessor devices. A high level on pin 10 0A1 allows the output voltages to appear on pins 2, 3 and 6.

Since the control input (pin 11) is connected to the output (pin 2) of the controlled power switch, when voltage appears at pin 2, voltages appear at pins 5, 4 and 12.

LED HL1 glows when the supply voltage DA1. greater than 9.5 V. In the off state, the microcircuit consumes a current of no more than 150 μA.

Transformer T1 can be replaced with TVK110-LM, TP112-6, TP114-5 or another similar one with an overall power of at least 10 W and an open-circuit voltage on the secondary winding of 12 ... 15 V.

If there are several transformers, you should choose the most powerful one, but with a lower voltage on the secondary winding. This will reduce the power dissipated by the microcircuit, which will positively affect its reliability.

Varistor MYG10-471 can be replaced by FNR-10K471, FNR-14K471. Schottky diodes SR360 can be replaced by MBRD360, MBR350, MBR360, 1N5822, MBR150, 1N5819 Instead of the Zener diode BZV55C-6V2, 1N4735A, TZMC-6V2 is suitable. If you want the BA4911 chip to turn on at a lower input voltage, you need to set the zener diode to a lower voltage, for example, BZV55C-4V3, with which DA1 will turn on at an input voltage of about 7,6 V. The HL1 LED can be any general purpose.

Oxide capacitors - K50-35, K50-68 or imported analogues. Non-polar capacitors - K10-17, K10-50.

By the way, for experiments it is not necessary to purchase a new copy of the microcircuit, since it is often found in car radios and often fails due to overheating or power reversal. You can use the faulty microcircuits remaining after replacement, since usually one or two output voltage channels fail, while the remaining ones continue to function.

It should also be noted that among the new microcircuits. BA4911 may come across faulty ones in which one of the output voltages is missing (most often +5 V).

If one or more output voltages DA1 are not used, then the corresponding blocking capacitors and terminating resistors can be omitted.

To power the BA4911 output, you can use emitter followers on powerful bipolar transistors, for example, on KT819.

In this case, the output voltage of the boosted channel of the stabilizer will be lower by 0,6 ... 1 V.

Author: A.Butov

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