The figure below shows an actual LED driving circuit with capacitor step-down. Please note that most application circuits are not connected with varistors or transient voltage suppression transistors. It is recommended to connect them, because varistors or transient voltage suppression transistors can effectively discharge the sudden change current at the moment of voltage sudden change (such as lightning, starting of large power consuming equipment, etc.), so as to protect secondary switches and other transistors. Their response time is generally in the order of micro milliseconds.
Figure LED driving circuit diagram with capacitor step-down