A voltage detector includes a first input terminal, a second input terminal, a first voltage detection circuit, a second voltage detection circuit, and a logic holder circuit. The first input terminal receives a first input voltage. The second input terminal receives a second input voltage. The first voltage detection circuit outputs a first detection signal that switches a logic state thereof when the first input voltage falls below a first detection voltage. The second voltage detection circuit outputs a second detection signal that switches a logic state thereof when the second input voltage falls below a second detection voltage. The logic holder circuit retains the logic state of the first detection signal when the second detection signal indicates that the second input voltage is below the second detection voltage.