This invention provides a pharmaceutically acceptable salt of 3-hydroxy-5-estrene-17-one 3-sulfate ester and a pharmaceutically acceptable salt of 3-hydroxy-5-estrene-17-one 3-sulfate ester, which are useful as an estrogens. The system comprises a control configured to control the at least one switch so that, if the power is switched on during a particular phase of the power, is the power is switched off during the opposite phase of the power, and if the power is switched off during a particular phase of the power, the power is switched on during the opposite phase of the power. The first voltage generating circuit is configured to generate a first voltage which increases or decreases according to a phase of a clock signal as time advances by the first current.