A regulator that has gained prominence as the requirements for load current increased is the switching voltage regulator. Standard linear regulators only have conversion efficiencies of less than 50%. Switching regulators can have efficiencies of up to 85%. This results in lower power dissipation, much smaller size components for a given power output, and operation over a wide range of voltage and current. Figure 9-3 details a switching voltage regulator. One notes that there are similarities to a linear voltage regulator. There is the sampling of the output, the error amplifier, and the error voltage resulting from a comparison of a sample of the output voltage and the reference voltage.
Here are the differences between the two regulators:
1. The error amplifier output controls a switch whose ratio of open to closed is varied.
2. Since the control element is a switch rather than a linear element, there is considerable difference in the regulator action.
The Control Element1. The error amplifier output controls a switch whose ratio of open to closed is varied.
2. Since the control element is a switch rather than a linear element, there is considerable difference in the regulator action.
Instead of a series element operating in the linear mode, the control element is a switch that is in series with a temporary energy storage element, an inductor. The switch is opened and closed at a very rapid rate, and the ratio of the time it is closed to the time it is opened is varied to accomplish the regulation. There is no linear control element operation; it is all digital, either open or closed. When the switch is closed, it charges the inductor with energy by creating a field of magnetic flux around the inductor. When the switch is opened, the magnetic flux collapses across the inductor and returns the energy to the circuit. As the energy is returned, the inductor uses D1, shown in Figure 9-3, to complete the circuit and keep current, IL, through the load.
Continued..........
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