ANALOGUE AND DIGITAL ELECTRONICS

Analogue and Digital Electronics

Analogue and Digital Electronics

This paper explores the complete the design of the circuit with a rectifier, voltage multiplier and a voltage regulator, implement the system in LTSpice and show the effect of variation in input voltage from .5V to 1V. Show the output waveforms, discusses change in output voltage would result when the load current varies over its full range and design the circuit by selecting a value for RC so that all the fabricated circuits are guaranteed to be in active mode.

Basic Operating Principles

Most voltage multiplier circuits, regardless of their topology, consist chiefly of rectifiers and capacitors. Figure 1 shows three basic multiplier circuits (Bassett, 2003, 277-333). The operating principle of all three circuits is essentially the same. Capacitors connected in series are charged and discharged on alternate half-cycles of the supply voltage. Rectifiers and additional capacitors are used to force equal voltage increments across each of these series capacitors (Bassett, 2003, 277-333). The multiplier circuit's output voltage is simply the sum of these series capacitor voltages. A wide variety of alternating signal inputs are used with multiplier circuits (Campardo, 2005, 33-77). The most popular are sine and square wave inputs. For simplicity, this discussion will be limited to sine wave inputs; the calculations become somewhat more involved with asymmetrical signals.

Figure 1A. Basic Multiplier Circuits. Half-Wave Voltage Doubler

Figure 1B. Basic Multiplier Circuits. Half-Wave Voltage Doubler

Figure 1C. Basic Multiplier Circuits. Half-Wave Voltage Tripler

Voltage Doublers

Figure 1A. shows a half-wave voltage doubler circuit. It functions as follows. On the negative halfcycle of the input voltage, capacitor C1 charges, through rectifier CR1, to a voltage of Vm. On the positive half-cycle, the input voltage, in series with the voltage of C1 (VC1 = Vm), charges capacitor C2 through rectifier CR2 to the desired output voltage of 2 Vm. Capacitor C1, which aides in the charging of a capacitor C2, sees alternating current ("AC Cap") while C2 sees only direct current ("DC Cap"). In this circuit, the output voltage and the input signal have the same ripple frequency.

Figure 2. Reverse Recovery Time Characteristic and Test Circuit Diagram

Voltage Tripler

Higher output voltages are possible through the use of a half-wave voltage tripler circuit, shown in figure 1C (Kind, 2001, 201-266). This circuit operates as follows. On the negative half-cycle of the input voltage, capacitor C1 charges through rectifier CR1 to a voltage of Vm. On the positive half-cycle, the input voltage, in series with the stored voltage on C1 (VC1 =

Vm), charges capacitor C2 through rectifier CR2 to a voltage of 2 Vm. On the next negative half-cycle, the charge on C1 is replenished. At the same time, the input voltage, in series with the stored voltage on C2 (VC2 = 2 Vm), charges capacitor C3 through CR3 to a voltage of 2 Vm (VC3 = Vb - Va = (Vm

+ VC2) - VC1 = 2 Vm). VC1 and VC3, in series, provide the output voltage of 3 ...