Category Archive for: Power Supplies and Voltage Regulators

THREE-TERMINAL INTEGRATED-CIRCUIT REGULATORS

A three-terminal regulator is a compact, easy-to-use, fixed-voltage regulator packaged in a single integrated circuit. To use the regulator, it is necessary only to make external connections to the three terminals: Vin, Yo, and ground. These devices are widely used to provide local regulation in electronic systems that may require several different supply voltages. For example, a 5-V regulator…

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Shunt Regulators

Figure 17-36 is a functional block diagram of the shunt-type regulator. Each of the components shown in the figure performs the same function as its counterpart in the series regulator (Figure 17-28), but notice in this case that the control element is in parallel with the load. The control clement maintains a constant load voltage  by shunting…

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Current Limiting

Many general-purpose power supplies are equipped with short-circuit or overload protection. One form of protection is called current limiting, whereby specially designed circuitry linuts the current that can be drawn from the supply to a certain specific maxirnum, even if the output terminals are short-circuited. Figure 17-32 shows a popular current-limiting circuit incorporated into the operational-amplifier regulator. As load current…

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SERIES AND SHUNT VOLTAGE REGULATORS

A voltage regulator is a device, or combination of devices. designed to maintain the output voltage of a power supply as nearly constant as possible. It can be regarded as a closed-loop control system because it monitor, output voltage and generates feedback that automatically increases or decreases t he supply voltage, as necessary, to compensate for any tendency of…

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VOLTAGE REGULATION

An ideal power supply maintains a constant voltage at its output terminals, no matter what current is drawn from it. The output voltage of a practical power supply changes with load current, generally dropping as load current increases. Power-supply specifications include a full-load current (IFL) rating, which is the maximum current that can be drawn from the supply. The…

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VOLTAGE MULTIPLIERS

Diodes and capacitors can be connected in various configurations to produce filtered, rectified voltages that are integer multiples of the peak value of an input sine wave. The principle of operation of these circuits is similar to that of the clamping circuits discussed in Chapter 15. By using a transformer to change the amplitude of an ac voltage before…

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RC Filters

To obtain a greater reduction in the ripple bf a capacitor-filtered waveform, a lowpass RC filter section can be connected across the capacitor,.The capacitor-resistor-capacitor combination is often called an RC 1r (PI) filter. The figure shows that the low-pass RC section further attenuates the Components represented by the ripple and passes the de value, although there is some…

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Repetitive Surge Currents

We have already discussed the initial surge current that flows through rectifier diodes when power is first applied and the uncharged filter capacitor behaves like a momentary short circuit. Figure 17-15 shows that current also surges through the diodes during the short time intervals that they are forward biased in normal operation. When the capacitor voltage is below the…

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CAPACITOR FILTERS

The frequency of the fundamentaL component of a half-wave-rectified waveform is the same as the frequency of its original (unrectified) ac waveform. Since the ac power source used in most de supplies has frequency 60 Hz, a half-wave-rectified  waveform contains a 60-Hz fundamental, plus harmonic componentmultiples of 60 Hz, plus’ de, or average value, component. A ft.…

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Full-Wave Bridge Rectifiers

Figure 17-6 shows another circuit used to perform full-wave rectification. One advantage of this circuit is that it does not require a transformer (although a transformer is often used to isolate the ac power line from the rest of the power supply). The diodes are arranged in the form of a bridge, and the circuit is called a full-wave…

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