Information from the China National Intellectual Property Administration shows that ABB Switzerland Ltd. has filed a patent titled “Pre-Charge Circuit for DC Bus Transient Voltage Protection,” with publication number CN121285915A, filed in September 2022.

The patent describes a pre-charge circuit designed for direct current (DC) bus systems, aiming to enhance transient voltage protection and improve operational stability during the charging process in power electronic systems.

According to the filing, the proposed circuit includes a varistor, a bypass circuit, a solid-state switch, and a voltage divider circuit. The bypass circuit is configured to receive current in response to DC bus charging conditions. The solid-state switch is connected in series with the varistor, with a common node electrically coupled between them to enable dynamic control of circuit operation.

When the bypass circuit detects charging current, the solid-state switch selectively connects the varistor to the DC bus. This allows the system to regulate and suppress voltage and current fluctuations during the charging phase. In addition, the voltage divider circuit is configured to distribute and monitor the DC bus voltage between the varistor and the solid-state switch.

By integrating adaptive circuit control during the pre-charging stage, the technology helps protect DC bus systems from transient voltage spikes, improving safety, reliability, and stability in high-power industrial and energy applications.