Position detector

A position detector for detecting a position of a detection body based on a magnetic field generated from a magnetic field generation element equipped to the detection body, the position detector comprising:

• a magnetic field detection element outputting a signal according to the magnetic field of the magnetic field generation member;
• a signal processing circuit processing the signal outputted from the magnetic field detection element;
• a first storage circuit storing a signal processed by the signal processing circuit;
• an output circuit outputting a signal outputted from the first storage circuit to an external device in a normal operation mode;
• a second storage circuit storing an output value of the first storage circuit in the normal operation mode;
• a first power supply circuit supplying electric power to the signal processing circuit and the first storage circuit;
• a malfunction determination circuit determining an instantaneous power interruption mode when electric power supply of the first power supply circuit is instantaneously interrupted;
• a second power supply circuit supplying electric power to the second storage circuit and the malfunction determination circuit;
• a signal route changing circuit preventing a signal transmission between the first storage circuit and the second storage circuit and a signal transmission between the first storage circuit and the output circuit, preventing the second storage circuit from updating data for a certain period of time, and permitting the second storage circuit, in which updating of the data is prevented, to output a signal to the output circuit, when the malfunction determination circuit determines the instantaneous power interruption mode;
• a delay circuit connected to the first power supply circuit;
• a first comparator circuit comparing a voltage supplied from the first power supply circuit to the signal processing circuit and the first storage circuit to a reference voltage that is set equal to or higher than a voltage enabling operation of the signal processing circuit and the first storage circuit;
• and
• a second comparator circuit comparing a voltage supplied from the first power supply circuit via the delay circuit to the reference voltage, wherein:
• the malfunction determination circuit determines the instantaneous power interruption mode when the first comparator circuit detects that the voltage supplied from the first power supply circuit is lower than the reference voltage and the second comparator circuit detects that the voltage supplied from the first power supply circuit via the delay circuit is higher than the reference voltage;
• the malfunction determination circuit determines a prolonged time power drop mode when the first comparator circuit detects that the voltage supplied from the first power supply circuit is lower than the reference voltage and the second comparator circuit detects that the voltage supplied from the first power supply circuit via the delay circuit is lower than the reference voltage;
• when the malfunction determination circuit determines the prolonged time power drop mode, the signal route changing circuit prevents the signal transmission between the first storage circuit and the second storage circuit, the signal transmission between the first storage circuit and the output circuit, and a signal transmission between the signal processing circuit and the second storage circuit, fixes the signal outputted from the second storage circuit to one of a high level and a low level, permits a signal transmission between the second storage circuit and the output circuit such that a fixed signal of the second storage circuit is outputted to the output circuit;
• the second power supply circuit includes a Zener diode connected to the first power supply circuit and a capacitor connected between the Zener diode and a ground;
• and
• a voltage of the capacitor is used as a power source of the electric power supplied to the second storage circuit in the instantaneous power interruption mode and at a beginning time of the prolonged time power drop mode.