Uninterruptible Power Supply and DC-DC Converter

An uninterruptible power supply, comprising:

• a rectifier;
• an inverter;
• and
• a direct current-direct current (DC-DC) converter,
• wherein an input end of the rectifier is connected to a power grid and an output end thereof is connected to the inverter and the DC-DC converter,
• wherein the rectifier is configured to convert an alternating current provided by the power grid into a direct current and output the direct current to the inverter or the DC-DC converter,
• wherein an input end of the inverter is connected to the output end of the rectifier,
• wherein the inverter is configured to invert the direct current obtained by the rectifier to an alternating current,
• wherein an input end of the DC-DC converter is connected to the output end of the rectifier and an output end thereof is connected to a battery,
• wherein the DC-DC converter is configured to charge the battery using the power supply output by the rectifier,
• wherein the output end of the rectifier comprises a positive bus BUS+, a negative bus BUS−, and an N wire,
• wherein an output end of the battery is connected to the rectifier, and a voltage output by the battery, after being boosted by the rectifier, provides a direct current to the inverter,
• wherein the DC-DC converter comprises a first capacitor, a second capacitor, a third capacitor, a first switch tube, a second switch tube, a first inductor, a second inductor, a third switch tube, and a fourth switch tube,
• wherein the positive bus BUS+ is connected to a first node through the first switch tube,
• wherein the negative bus BUS− is connected to a second node through the second switch tube,
• wherein two ends of the first capacitor are respectively connected to the BUS+ and the N wire;
• two ends of the second capacitor are respectively connected to the BUS− and the N wire,
• wherein the third switch tube is connected between the first node and the N wire,
• wherein the fourth switch tube is connected between the second node and the N wire,
• wherein the first inductor, the battery, and the second inductor connected in series are connected in sequence between the first node and the second node, and
• wherein two ends of the third capacitor are respectively connected to the first node and the second node, or, the third capacitor is connected in parallel at two ends of the battery, or, one end of the third capacitor is connected to the first node and the other end thereof is connected to a common end of the battery and the second inductor, or, one end of the third capacitor is connected to the second node and the other end thereof is connected to a common end of the battery and the first inductor.