Circuit device, electronic apparatus, and IC card
A circuit device includes: a first storage control unit which receives power from a power receiving unit which receives power by electromagnetic induction, to perform control of storing charge in a first charge storage unit; a second storage control unit which performs control of storing charge in a second charge storage unit; and a power source supply unit which supplies power source to a system device based on charges stored in the first charge storage unit and the second charge storage unit. The second charge storage unit is a charge storage unit whose charge storage capacitance is smaller than that of the first charge storage unit. The power source supply unit supplies, at the time of system start-up after the start of power reception, power source based on the stored charge of the second charge storage unit to the system device.
1. An electronic apparatus comprising:
a system device that performs a display control process of a display unit which displays an image; and
a circuit device including:
a first storage control unit which receives power from a power receiving unit which receives power by electromagnetic induction, to perform control of storing charge in a first charge storage unit;
a second storage control unit which receives power from the power receiving unit to perform control of storing charge in a second charge storage unit; and
a power source supply unit which supplies power source to the system device based on charges stored in the first charge storage unit and the second charge storage unit,
wherein
the second charge storage unit is a system-start-up charge storage unit whose charge storage capacitance is smaller than that of the first charge storage unit,
during a power reception period, the first storage control unit performs control of storing an amount of charge sufficient to perform at least one display rewriting process of the display unit,
the power source supply unit supplies, at the time of system start-up after the start of power reception by the power receiving unit, power source based on the stored charge of the second charge storage unit to the system device,
during a display rewriting period following the power reception period, at the time of the system start-up, the system device is supplied with the power source based on the amount of charge stored in the first charge storage unit during the power reception period to perform a display rewriting process of the display unit, and
when the length of the power reception period is defined as T 1 and the length of the display rewriting period is defined as T 2 , the relationship of T 2 >T 1 is satisfied.
2. The circuit device according to claim 1 , wherein
the at least one display rewriting process of the display unit comprises at least one process of rewriting the entire image displayed by the display unit.
3. The circuit device according to claim 1 , wherein
the power source supply unit supplies power source to the system device after a power supply voltage obtained by the stored charge of the second charge storage unit exceeds a minimum operating voltage of the system device.
4. The circuit device according to claim 1 , wherein
the power source supply unit includes
a first diode which is disposed between a first storage node of the first charge storage unit and a connection node and whose forward direction is a direction from the first storage node toward the connection node and
a second diode which is disposed between a second storage node of the second charge storage unit and the connection node and whose forward direction is a direction from the second storage node toward the connection node, and
the power source supply unit supplies power source to the system device based on a voltage at the connection node.
5. The circuit device according to claim 4 , wherein
the power source supply unit includes
a switch circuit which is disposed between the connection node and an output node of the power source supply unit and
a voltage detection circuit which detects a voltage at the connection node, and
the switch circuit is brought into ON state, when the voltage detection circuit detects that the voltage at the connection node exceeds a given threshold voltage, to supply power source to the system device.
6. The electronic apparatus according to claim 1 , wherein the display unit is an electrophoretic display unit.
7. The electronic apparatus according to claim 1 , wherein
the system device performs the display rewriting process of the display unit based on data received during the power reception period.
8. The circuit device according to claim 1 , wherein
prior to the end of power reception by the power receiving unit, data reception is completed and the display rewriting process is started.
9. The circuit device according to claim 8 , wherein the display rewriting process is completed after the end of power reception by the power receiving unit.
10. The circuit device according to claim 1 , wherein
the first charge storage unit is electrically connected between the first storage control unit and the power source supply unit,
the second charge storage unit is electrically connected between the second storage control unit and the power source supply unit.
11. The circuit device according to claim 1 , wherein
the first storage control unit performs control of storing charge necessary for only one display rewriting of the display unit in the first charge storage unit.
12. An IC card comprising:
a power receiving unit which receives power by electromagnetic induction;
a display unit which displays an image;
a system device which performs a display control process of the display unit; and
a power source management unit which receives power from the power receiving unit to supply power source to the system device, the power source management unit including:
a first storage control unit which receives power from the power receiving unit to perform control of storing charge in a first charge storage unit, and
a second storage control unit which receives power from the power receiving unit to perform control of storing charge in a second charge storage unit,
wherein
during a power reception period, the first storage control unit performs control of storing an amount of charge sufficient to perform at least one display rewriting process of the display unit,
at the time of system start-up after the start of power reception by the power receiving unit, the system device is supplied with power source based on the stored charge of the second charge storage unit,
during a display rewriting period following the power reception period, at the time of the system start-up, the system device is supplied with the power source based on the amount of charge stored in the first charge storage unit during the power reception period, to perform a display rewriting process of the display unit, and
when the length of the power reception period is defined as T 1 and the length of the display rewriting period is defined as T 2 , the relationship of T 2 >T 1 is satisfied.
13. The IC card according to claim 12 , wherein
the power source management unit includes
a power source supply unit which supplies the power source to the system device based on the charges stored in the first charge storage unit and the second charge storage unit,
the second charge storage unit is a system-start-up charge storage unit whose charge storage capacitance is smaller than that of the first charge storage unit.