Power supply device and method of controlling power supply device

A power supply device, comprising:

• an output circuit configured to be supplied with electric power from a power supply, and to output a current;
• a driving circuit configured to control an output operation of the output circuit for outputting the current;
• an overcurrent detection circuit configured to output a detection signal to a first node when detecting an overcurrent in the output circuit;
• an off-state fixing circuit configured to output, based on the detection signal inputted to the first node, an off-state fixing signal for performing a forcible suspension of the output operation of the output circuit from an output node to the driving circuit, regardless of whether a control signal is outputted;
• and
• a control unit configured to receive the detection signal, and to output the control signal for controlling the output operation of the output circuit to the driving circuit for controlling the output operation of the output circuit by means of the driving circuit,
• wherein, in response to the off-state fixing signal, the driving circuit performs the forcible suspension of the output operation of the output circuit regardless of whether the control signal is outputted,
• wherein the control unit outputs a cancellation signal for cancelling the forcible suspension of the output operation of the output circuit to the off-state fixing circuit after an off period passes from time when the detection signal is inputted,
• wherein, in response to the cancellation signal, the off-state fixing circuit stops outputting the off-state fixing signal to cause the driving circuit to return to a normal operation for controlling the output operation of the output circuit based on the control signal,
• wherein the off-state fixing circuit:
• outputs the detection signal inputted to the first node to the driving circuit as the off-state fixing signal, and
• thereafter, controls a potential at the first node to stop outputting the off-state fixing signal response to the cancellation signal inputted,
• wherein the overcurrent detection circuit does not output the detection signal to the first node when no overcurrent caused by the output operation of the output circuit is detected,
• wherein the control unit outputs the control signal for controlling the output operation of the output circuit to the driving circuit in order to control the output operation of the output circuit by means of the driving circuit when the detection signal is not inputted after the cancellation signal is outputted,
• wherein the off-state fixing circuit includes:
• a first control resistor having an end that is connected to the power supply, and another end that is connected to the output node,
• a second control resistor having an end that is connected to the power supply,
• a third control resistor having an end that is connected to another end of the second control resistor, and another end that is connected to the first node,
• a first capacitor having an end that is connected to the other end of the first control resistor, and another end that is connected to a fixed potential,
• a second capacitor having an end that is connected to the end of the second control resistor, and another end that is connected to the fixed potential,
• a third capacitor having an end that is connected to the other end of the second control resistor, and another end that is connected to the fixed potential,
• a fourth control resistor having an end that is connected to the other end of the second control resistor,
• an NPN-type bipolar transistor having a collector that is connected to the other end of the second capacitor, an emitter that is connected to the fixed potential, and a base to which the cancellation signal from the control unit is inputted, and
• a reset circuit having an end that is connected to the other end of the first control resistor, and another end that is connected to the fixed potential, the reset circuit being configured to electrically connect the end and the other end of the first capacitor to discharge the first capacitor when a potential at the other end of the second control resistor is less than a reset threshold value that is predefined, and to electrically disconnect the end and the other end of the first capacitor when the potential at the other end of the second control resistor is equal to or greater than the reset threshold value, and
• wherein the off-state fixing circuit outputs a signal that is based on the potential at the fiat node to the driving circuit as the off-state fixing signal in response to the detection signal outputted from the overcurrent detection circuit, and stops outputting the off-state fixing signal to the driving circuit in response to the cancellation signal outputted from the control unit.

A method of controlling a power supply device including:

• an output circuit configured to be supplied with electric power from a power supply, and to output a current;
• a driving circuit configured to control an output operation of the output circuit for outputting the current;
• an overcurrent detection circuit configured to output a detection signal to a first node when detecting an overcurrent in the output circuit;
• an off-state fixing circuit configured to output, based on the detection signal inputted to the first node, an off-state fixing signal for performing a forcible suspension of the output operation of the output circuit from an output node to the driving circuit, regardless of whether a control signal is outputted;
• and a control unit configured to receive the detection signal, and to output the control signal for controlling the output operation of the output circuit to the driving circuit for controlling the output operation of the output circuit by means of the driving circuit,
• the method comprising the steps of:
• performing a forcible suspension of the output operation of the output circuit in response to the off-state fixing signal by means of the driving circuit, regardless of whether the control signal is outputted;
• outputting, from the control unit, a cancellation signal for cancelling the forcible suspension of the output operation of the output circuit to the off-state fixing circuit after an off period passes from time when the detection signal is inputted;
• and
• in response to the cancellation signal, stopping, by the off-state fixing circuit, outputting the off-state fixing signal to cause the driving circuit to return to a normal operation for controlling the output operation of the output circuit based on the control signal,
• wherein the off state fixing circuit:
• outputs the detection signal inputted to the first node to the driving circuit as the off-state fixing signal;
• and
• thereafter, controls a potential at the first node to stop outputting the off-state fixing signal in response to the cancellation signal inputted,
• wherein the overcurrent detection circuit does not output the detection signal to the first node when no overcurrent caused by the output operation of the output circuit is detected,
• wherein the control unit outputs the control signal for controlling the output operation of the output circuit to the driving circuit in order to control the output operation of the output circuit by means of the driving circuit when the detection signal is not inputted after the cancellation signal is outputted,
• wherein the output node is connected to the first node,
• wherein the off-state fixing circuit includes:
• a first control resistor having an end that is connected to the power supply, and another end that is connected to the first node,
• a second control resistor having an end that is connected to the power supply,
• a capacitor having an end that is connected to the first node, and another end that is connected to a fixed potential,
• a PNP-type bipolar transistor having an emitter that is connected to the first node, another end that is connected to the fixed potential, and a base that is connected to another end of the second control resistor, and
• an NPN-type bipolar transistor having a collector that is connected to the other end of the second control resistor, an emitter that is connected to the fixed potential, and a base to which the cancellation signal from the control unit is inputted, and
• wherein the off-state fixing circuit outputs a signal that is based on the potential at the first node to the driving circuit as the off-state fixing signal, in response to the detection signal outputted from the overcurrent detection circuit and stops outputting the off-state fixing signal to the driving circuit in response to the cancellation signal outputted from the control unit.