A circuit adapted to detect applied voltage and/or voltage based conditions. The circuit comprises a zero-cross detection circuit and a controller. The zero-cross detection circuit is adapted to output a zero-cross signal comprising zero-cross events based on an applied alternating current power signal. The controller is adapted to store a relationship between a pulse width delta, frequency, and voltage. The controller is adapted to sense the zero-cross signal from the zero-cross detection circuit to determine its frequency and pulse width delta by calculating a difference between a high-time and a low-time of the zero-cross signal, and determine the applied voltage based on the stored relationship. The controller can adjust at least one setting of the circuit based on the determined applied voltage, such as the timing of a dimming circuit. In another embodiment, the controller may directly detect voltage based conditions, such as zero-cross delays a dimmer circuit. The controller is adapted store a relationship between a pulse width delta and zero-cross signal delay. The controller is adapted to receive the zero-cross signal from the zero-cross detection circuit, determine a pulse width delta, and determine a zero-cross delay based on the determined pulse width delta and the stored relationship.