Crowbar Overvoltage Protection with Passive Power Supply of Control Circuit

The importance of power semiconductor converters steadily increases and as the use of converters grows, the risk of overvoltage damage also increases. The overvoltage protections are very important parts of electrical equipment containing power converters, e.g. inverters, connected especially to the grid lines. The grid line can originate the transient voltage induced by atmospheric phenomena, etc., which can be transmitted to the power converter. The overvoltage protection based on a mechanical spark system is very robust and simple, but not very precise for set up the break-down voltage. The electronically controlled overvoltage, e.g. crowbar, can operate precisely, but the auxiliary power sources for its control circuit are usually required. This article describes the active crowbar with a passive power supply of its controlled circuits. These control circuits operate directly on the power converter low voltage side and do not require any auxiliary power supply.