Agilent Technologies AGILENT MODELS 6023A and 6028A Autoranging Power, Block Diagram Overview

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Principles of Operation

Autoranging Power

Autoranging allows the unit to be compact and light weight and yet to deliver a range of output voltage current combinations which otherwise would require the use of more than one supply or a higher rated-power supply. Autoranging is a name for circuitry which automatically makes full power available at all but low rated output voltages and currents. By comparison, a conventional constant-voltage/constant-current (CV/CC) power supply can provide full output power only at maximum rated output voltage and current. For example the power available from a 200 watt, 20V, 10A CV/CC supply adjusted to deliver 10V is only 100 watts.

The power available from the unit when adjusted to 10V is more than 200 watts. The permitted maximum voltage and current of the unit change as current and voltage are adjusted by the user. Thus the unit can be a 20V, 10A supply; a 10V, 20A supply; a 6.7V 30A supply, or any other supply in the range shown graphically in Figure 4-1.

Figure 4-1. Output Characteristics: Typical CV/CC and Autoranging Power Supplies

Block Diagram Overview

This section is an overview. Using the block diagram, Figure 4-2, it explains how the unit works, how major circuits are interconnected and what signals are called. The next section, explains more thoroughly how major circuits operate and uses the simplified schematic, Figure 4-3. Power flows from the ac mains at the left of the block diagram through circuit blocks connected by heavy lines to the load on the output terminals at the right. The Down Programmer lowers the output voltage when required by the CV Circuit. Overvoltage Protection senses the output and shuts down the unit by inhibiting the Pulse Width Modulator (PWM) through the MASTER ENABLE input when an overvoltage is detected. Other protection circuits (not shown) can also inhibit the PWM through the Inhibit Gate.

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