An exemplary voltage converter includes a pulse width modulation controller chip, a pull-up transistor, a pull-down transistor, and a low pass filter. The pulse width modulation controller chip includes a plurality of pins, a power management circuit, a gate control logic circuit, a first gate driver, a second gate driver, a current source, a first resistor, an inductor current sensor, a counter and current step generator, and an oscillator. The plurality of pins include a Vcc pin, a BOOT pin, a PHASE pin, a UGATE pin, a LGATE pin, and a GND pin. The PHASE pin serves as a multi-function pin in the pulse width modulation controller chip. The current source, the first resistor, the inductor current sensor, the counter and current step generator, the oscillator, and the pull-down transistor constitute a light-load efficiency improvement circuit.