Power supply system for memory unit of camera

An electronic instrument comprising;

• a microcomputer for controlling operation of each unit constituting the instrument,
• a main battery for supplying power,
• a backup battery for supplying power to the microcomputer and the display unit in place of the main battery,
• a first detecting means for outputting signals in response to the loading and unloading of the main battery,
• a backup voltage detecting means for detecting a voltage of the backup battery in accordance with the output signals of the first detecting means, and
• reset means for outputting a reset signal to initialize the microcomputer,
• wherein the reset means is adapted to output the reset signal when the voltage detected by the backup voltage detecting means is below a predetermined value.

An electronic instrument comprising;

• a microcomputer,
• a main battery for supplying power to the microcomputer,
• a backup battery available to supply power to the microcomputer,
• a first detecting means for outputting signals corresponding to presence and absence of the main battery,
• a second detecting means for outputting signals accoding to comparison of a voltage of the main battery with a predetermined value, and
• a peripheral circuit operable under control by the microcomputer,
• wherein the microcomputer is adapted to provide a stop operation instruction to the peripheral circuit when the first detecting means outputs a signal indicating that the main battery is absent from the instrument or when the second detecting means outputs a signal indicating that the voltage of the main battery is insufficient.

A power supply circuit comprising;

• a small-load circuit,
• a great-load circuit,
• a main battery for supply power directly to the great-load circuit,
• a stepdown circuit mounted between the small-load circuit and the main battery for supplying power to the small-load circuit after reducing a supply voltage received from the main battery to a predetermined value,
• backup means for supplying power to the small-load circuit through the stepdown circuit, and
• a rectifying element mounted between the backup means and the great-load circuit for forbidding power supply from the backup means to the main battery and the great-load circuit.

A power supply circuit comprising;

• a small-load circuit,
• a great-load circuit,
• a main battery for supply power directly to the great-load circuit,
• a stepdown circuit for supplying power to the small-load circuit after reducing a supply voltage received from the main battery to a predetermined value,
• a bypass circuit for connecting the main battery directly to the small-load circuit, and
• power supply switching means for switching a power supply route to the small-load circuit,
• wherein the power supply switching means is adapted to switch the power supply route to permit the small-load circuit to receive power from the main battery through the bypass circuit when the great-load circuit is in operation.

An electronic instrument for a camera comprising;

• data storing means for storing photographic data such as a frame count of a film,
• data imprinting means for imprinting data such as dates on the film,
• a main battery for supplying power to the data storing means,
• a data imprinting battery for supplying power to the data imprinting means,
• power supply switching means for switching a power supply route to the data storing means, and
• means for detecting removal of the main battery,
• wherein the power supply switching means is adapted to switch the power supply route so that the data storing means receives power from the data imprinting battery when the main battery is removed or when a voltage of the main battery has reduced.

An electronic instrument comprisng;

• an operating unit,
• memory means for storing operating information of the operating unit,
• a main battery and a backup battery for supplying power to the operating unit and the memory means,
• switch means for permitting power supply from the backup battery to the memory means when turned on,
• detecting means for outputting a signal in response to the loading of the main battery, and
• power supply starting means operable in response to the signal from the detecting means to turn on the switch means and maintain the switch means turned on.

An electronic instrument comprising;

• an operating unit,
• a main battery and a backup battery for supplying power to the operating unit,
• a first detecting means for outputting signals corresponding presence and absence of the main battery,
• a second detecting means for outputting signals according to comparison of a voltage of the backup battery with a predetermined value, and
• a restriction means for outputting a signal to the operating means for forbidding the operation thereof in response to the signals received from the first detecting means and the second detecting means,
• wherein the restriction means is adapted to output the forbidding signal when the first detecting means outputs a signal representing that the main battery is absent from the instrument or when the second detecting means outputs a signal representing that the voltage of the backup battery is insufficient.