Slow-Release Relay Circuit for Back-EMF-Free Return Timing

The patent introduces a diode as an intermediary component between the relay coil and the switching circuit. This diode provides a dedicated current path for the inductive load, allowing the relay coil current to decay smoothly without generating harmful counter electromotive voltage that would damage the switching circuit. The diode acts as a mediator that protects the switching circuit while enabling controlled relay return timing.

The patent segments the current path by creating a separate loop for the relay coil through the diode, independent from the main switching circuit path. This segmentation allows the relay coil to discharge its stored energy through the diode without interacting with the switching circuit components, thereby preventing voltage damage while maintaining timing control functionality.

The patent implements a timer circuit that monitors the discharge process and provides feedback control. The timer circuit detects when the relay coil current has decayed to a predetermined level and uses this information to control the switching circuit timing. This feedback mechanism compensates for variations in capacitor capacity and ensures consistent relay return timing despite electrolytic capacitor deterioration over time.

The patent changes the control parameter from direct capacitor discharge timing to timer-circuit-based timing. By using the timer circuit to monitor and control the discharge process based on current decay levels rather than fixed time intervals, the system maintains precise relay return timing even as capacitor characteristics change due to aging or manufacturing variations.