A smart junction box for a photovoltaic solar power module, and related method of operation. The junction box includes a plurality of active bypass circuits for protecting the solar cells from reverse bias, a novel power supply circuit in several embodiments that can operate with input voltages of either positive or negative polarity, a capacitor for storing and supplying energy, and a master control circuit. The master control circuit is able to enable/disable the power supply, force the bypass switches to open, and modulate the on-resistance of the bypass switches. The master control circuit performs these functions in a coordinated way to maintain the voltage across the capacitor within predetermined limits, thereby ensuring the internal circuitry is powered under all operating conditions including: full sunlight, partial shading, full shading, and safe mode for reducing the risk of electrical shock to firefighters.