Control circuit for protecting against spark discharge

A control circuit for protecting an electrostatic spray-coating apparatus having a high-voltage supply from spark discharge, wherein the control circuit comprises a disconnect device for automatically disconnecting the high-voltage supply and a device for detecting an abnormal operation of the high-voltage supply, wherein the device for detecting an abnormal operation of the high-voltage supply is designed to monitor at least one parameter which is characteristic of the operation of the high-voltage supply and to output a corresponding disconnect signal to the disconnect device when the at least one parameter characterizing the operation of the high-voltage supply exceeds or falls below a defined limit value;

• and
• wherein a closed loop system is further provided in order to operate the high-voltage supply in constant-current operation, wherein in the constant-current operation an operating current of the high-voltage supply or a spray current is kept constant and a high-voltage output of the high-voltage supply varies depending on load between a defined minimum and maximum value, and wherein the device for detecting abnormal operation of the high-voltage supply is designed to detect the high voltage output of the high-voltage supply and output a corresponding disconnect signal to the disconnect device if:
• a present value of the high voltage output of the high-voltage supply falls below a defined limit value;
• and/or
• a rate of change of the high voltage output of the high-voltage supply falls below a defined limit value.