Power supply circuit having low quiescent current for a bypass mode. One example power supply circuit generally includes a transistor; a switching node coupled to a source of the transistor; a power supply rail; a capacitor having a first terminal coupled to the power supply rail and having a second terminal coupled to the switching node; a gate driver having an output coupled to a gate of the transistor, having a first power input coupled to the power supply rail, and having a second power input coupled to the switching node; logic having a first input coupled to the first terminal of the capacitor, having a second input coupled to the second terminal of the capacitor, and having a first output; and a pullup circuit having a control input coupled to a second output of the logic and having an output coupled to the gate of the transistor.