Constantvoltage

Constant voltage refers to a mode of operation in which the output voltage is held at a predetermined level regardless of varying load within specified limits. It is a fundamental regulation mode used in electronic power supplies and battery chargers. In most designs a voltage reference, an error amplifier, and a regulating element (transistor) form a feedback loop that compares the actual output against the reference and adjusts the pass element to keep the output constant. The load current can vary; the regulator supplies whatever current is required up to its maximum rating. Beyond that limit, the regulator may enter current-limit or foldback mode, causing the output voltage to sag.

In switching and linear regulators, the CV mode is often accompanied by specifications such as line regulation and load regulation, ripple, and transient response. Some supplies are designed to operate only in CV mode, while other supplies use a constant-current stage and transition to constant-voltage regulation as the load approaches the rated voltage.

In charging applications, constant-voltage charging is used after a constant-current phase. The charger applies a fixed voltage and allows current to diminish as a battery approaches full charge; for lithium-ion cells, the typical final charging voltage is around 4.2 V per cell, and charging is terminated or current-limited to prevent overcharge.

Common examples include bench power supplies, lab instruments, and battery chargers. Safety features such as short-circuit protection, overvoltage protection, and proper heat dissipation are important because maintaining a fixed voltage under high load can generate heat and stress components.