| 摘要 |
A CPU outputs a high level ENB signal to a USB-IC via an ENB line and monitors, after outputting the ENB signal, whether or not there is an overcurrent in the USB-IC on the basis of the voltage level of the ENB line. The USB-IC outputs, when it receives the ENB signal, a 5 V voltage to a VBUS line and stops, when an overcurrent occurs, output of the 5 V voltage to the VBUS line. A connector changes the voltage level of the ENB line to a high voltage level using the 5 V voltage of the VBUS line and changes, when output of the 5 V voltage is stopped, the voltage level of the ENB line to a low level. Thus, the ENB line may be shared for outputting the ENB signal from the CPU and for providing notification of an overcurrent from the USB-IC. |
| 主权项 |
1. An electronic device comprising:
a main control unit; and a sub-control unit that is connected to the main control unit via a connection circuit including a predetermined signal line and that performs control of an external device, wherein the main control unit outputs as an enable signal that enables driving of the sub-control unit a signal which represents a high voltage level to the sub-control unit via the predetermined signal line and detects, after output of the enable signal is completed, a defect in the sub-control unit on the basis of whether or not a voltage level of the predetermined signal line is the high voltage level, the sub-control unit outputs, when the enable signal is inputted thereto from the main control unit, a predetermined voltage to a power line that is capable of supplying power to the external device and stops, when a defect related to power supply occurs, output of the predetermined voltage to the power line, the connection circuit is configured so that, when the predetermined voltage is outputted to the power line, the voltage level of the predetermined signal line is changed to the high voltage level by the predetermined voltage and, when output of the predetermined voltage to the power line is stopped, the voltage level of the predetermined signal line is changed to a low voltage level, wherein the connection circuit is connected to the power line and is grounded via a first resistor and a second resistor, and further includes a first line connected to the predetermined signal line at a point between the first resistor and the second resistor, wherein the connection circuit further includes a second line connected to the predetermined signal line at a point closer to the main control unit than a connection point of the predetermined signal line and the first line, and
the main control unit includes
an enable signal terminal connected to the predetermined signal line, anda monitor terminal connected to the second line, andthe main control unit is configured to change, when the enable signal is outputted, a voltage level of the enable signal terminal to the high voltage level, determine, when the enable signal has continued to be in a high voltage level state for a predetermined time, that output of the enable signal is completed, put the enable signal terminal into a high-impedance state, start monitoring the voltage level that is to be inputted to the monitor terminal, and thereby detect a defect in the sub-control unit. |
