Power Supply Regulation
Power Supply Regulation
DC-DC voltage converters are often used to provide a regulated voltage supply from an unregulated voltage source. Unregulated voltage sources can be rectified line voltages that exhibit fluctuations due to changes in magnitude. Regulated voltage supplies provide an average DC output voltage at a desired level (3.3 V, 2.5 V, etc.), despite fluctuating input voltage sources and variable output loads. Factors to consider when deciding on a regulated voltage supply solution include: * Available source input voltages * Desired supply output voltage magnitudes * Ability to step-down or step-up output voltages, or both * DC-DC converter efficiency (POUT / PIN) * Output voltage ripple * Output load transient response * Solution complexity (one IC solution, # of passive components, controller and external FETs) * Switching frequency (for switch-mode regulators)
The following sections describe several different voltage regulators.
Linear Regulators
Linear voltage regulators are commonly used for both step-up (output supply voltage is greater than input source voltage) and step-down (output supply voltage is lower than input source voltage) applications. Linear regulators are also available with either a fixed output voltage or a variable output voltage when using external biasing resistors.
The advantage of linear regulators is simple implementation and minimal parts (just the IC in the case of fixed output) and low output ripple. The major disadvantage of linear regulators is low efficiency. Significant power is dissipated within the linear regulator IC, as the converter is constantly on and conducting current. Linear regulators should be used when the difference between input source voltage and output supply voltage is minimal, and converter efficiency is not a concern.
Switching Regulators
Switching voltage regulators are commonly used for both step-up and step-down applications, and differ from linear
DC-DC voltage converters are often used to provide a regulated voltage supply from an unregulated voltage source. Unregulated voltage sources can be rectified line voltages that exhibit fluctuations due to changes in magnitude. Regulated voltage supplies provide an average DC output voltage at a desired level (3.3 V, 2.5 V, etc.), despite fluctuating input voltage sources and variable output loads. Factors to consider when deciding on a regulated voltage supply solution include: * Available source input voltages * Desired supply output voltage magnitudes * Ability to step-down or step-up output voltages, or both * DC-DC converter efficiency (POUT / PIN) * Output voltage ripple * Output load transient response * Solution complexity (one IC solution, # of passive components, controller and external FETs) * Switching frequency (for switch-mode regulators)
The following sections describe several different voltage regulators.
Linear Regulators
Linear voltage regulators are commonly used for both step-up (output supply voltage is greater than input source voltage) and step-down (output supply voltage is lower than input source voltage) applications. Linear regulators are also available with either a fixed output voltage or a variable output voltage when using external biasing resistors.
The advantage of linear regulators is simple implementation and minimal parts (just the IC in the case of fixed output) and low output ripple. The major disadvantage of linear regulators is low efficiency. Significant power is dissipated within the linear regulator IC, as the converter is constantly on and conducting current. Linear regulators should be used when the difference between input source voltage and output supply voltage is minimal, and converter efficiency is not a concern.
Switching Regulators
Switching voltage regulators are commonly used for both step-up and step-down applications, and differ from linear