How did the Tychonic system explain the phases of Venus?

The Tychonic system, proposed by the Danish astronomer Tycho Brahe, explained the observed variations in the phases of Venus by positioning the planet in an orbit around the Sun.1

While Tycho retained the Ptolemaic system's geocentric model—placing a stationary Earth at the center of the universe with the Sun and Moon revolving around it—he incorporated the Copernican concept that all other planets revolve around the Sun. By having Venus orbit the Sun, the Tychonic system provided a physical explanation for the planet's changing phases, a phenomenon that the traditional Ptolemaic system could not account for.12