A boost converter is a type of DC-DC converter that increases the output voltage from a lower input voltage. It consists of a power switch (usually a transistor), an inductor, a diode, and a capacitor. The operation of a boost converter relies on the principle of energy storage and transfer.
The output voltage of a boost converter is limited by the duty cycle of the power switch. The duty cycle is the ratio of time the switch is ON to the total switching period. Here's a step-by-step explanation of how a boost converter limits its output voltage:
Switch ON: During the ON period, the power switch (transistor) is closed, allowing current to flow from the input source (usually a battery or power supply) through the inductor and into the output capacitor. The inductor stores energy in the form of a magnetic field, and the capacitor charges up.
Switch OFF: After a certain period (determined by the control circuitry), the power switch is opened (OFF period). When the switch is OFF, the current in the inductor cannot immediately change, so the energy stored in the inductor must be transferred to the output circuit.
Voltage transfer: The inductor discharges its stored energy into the output circuit, which causes the output voltage to rise. The diode, placed in parallel with the power switch, allows the current to flow only in one direction, preventing the discharge of energy from the output capacitor back to the input source.
Duty cycle control: The output voltage is dependent on the duty cycle of the power switch. The duty cycle determines the amount of time the switch remains ON during each switching period. By adjusting the duty cycle, the boost converter can regulate the output voltage.
To increase the output voltage, the duty cycle needs to be increased. Conversely, reducing the duty cycle decreases the output voltage. The control circuitry in a boost converter monitors the output voltage and adjusts the duty cycle accordingly to maintain the desired output voltage level.
It's important to note that the output voltage in a boost converter cannot exceed the input voltage multiplied by the duty cycle. Therefore, the boost converter has inherent limitations on the output voltage, based on the input voltage and the duty cycle set by the control circuitry.