Controlling and protecting power-supply paths from thermal overloads

1. A power supply controller connected to a power-supply path for supplying power from a power source to a load for controlling power supply from the power source to the load, and having a sleep mode in which current consumption is reduced, comprising:

a switch input detection circuit configured to generate a power-supply command signal commanding any one of start and stop of the power supply from the power source to the load;

a switch circuit connected between the power source and the power-supply path and configured to permit and inhibit the power supply from the power source to the load;

a power-supply path protection circuit configured to control switching operation of the switch circuit according to the power-supply command signal, to calculate a temperature of the power-supply path regardless of whether power is supplied to the load, not to calculate the temperature of the power-supply path in the sleep mode, to determine whether the calculated temperature of the power-supply path reaches an upper limit, and to inhibit power supply to the load by the switch circuit according to the calculated temperature reaching the upper limit to protect the power-supply path; and

a sleep mode setting circuit configured to determine whether the temperature of the power-supply path satisfies a temperature condition independent of the upper limit and to set the power supply controller to the sleep mode according to a result of the determination indicating the temperature of the power-supply path satisfying the temperature condition.

2. The power supply controller according to claim 1 , wherein the temperature condition is that the temperature of the power-supply path decreases to a threshold temperature after the power-supply path protection circuit receives the power-supply command signal commanding the stop of the power supply to the load.

3. The power supply controller according to claim 2 , wherein the threshold temperature is set by adding a predetermined temperature to the ambient temperature.

4. The power supply controller according to claim 1 , wherein the power-supply path protection circuit includes:

a current detector configured to detect a current flowing through the load;

a temperature detector configured to detect an ambient temperature;

a wire temperature calculation circuit configured to calculate an increase in temperature of the power-supply path from the ambient temperature based on a difference between heat generation in the power-supply path due to the current flowing through the power-supply path and heat dissipated from the power-supply path, and to calculate a temperature of the power-supply path by adding the increase in temperature of the power-supply path to the ambient temperature; and

a power supply determination control circuit configured to control turn-on and turn-off of the switch circuit according to the power-supply command signal, and to turn off the switch circuit according to the temperature of the power-supply path reaching the upper limit.

5. A method for controlling a power supply controller connected to a power-supply path for supplying power from a power source to a load for controlling power supply from the power source to the load, and having a switch circuit configured to permit and inhibit the power supply from the power source to the load and a sleep mode in which current consumption is reduced and, comprising:

calculating a temperature of the power-supply path regardless of whether the power is supplied to the load;

determining whether the calculated temperature of the power-supply path reaches an upper limit;

inhibiting the power supply to the load by the switch circuit according to the calculated temperature of the power-supply path reaching the upper limit;

determining whether the temperature of the power-supply path satisfies a temperature condition independent of the upper limit; and

setting the power supply controller to the sleep mode according to a result of the determination indicating the temperature of the power-supply path satisfying the temperature condition.

6. The method for controlling the power supply controller according to claim 5 , wherein the temperature condition is that the temperature of the power-supply path decreases to a threshold temperature after a power-supply command signal commanding the stop of the power supply to the load is received.

7. The method for controlling the power supply controller according to claim 6 , wherein the threshold temperature is set by adding a predetermined temperature to the ambient temperature.

8. The method for controlling the power supply controller according to claim 5 , further comprising:

generating a power-supply command signal commanding a start of the power supply to the load;

detecting a current flowing through the load and an ambient temperature according to the power-supply command signal

detecting heat generation in the power-supply path due to the current flowing through the power-supply path; and

detecting heat dissipation from the power-supply path, wherein

the calculating includes calculating:

a difference between the heat generation and the heat dissipation;

an increase in the temperature of the power-supply path from the ambient temperature based on the difference between the heat generation and the heat dissipation; and

a temperature of the power-supply path by adding the increase in temperature of the power-supply path to the ambient temperature.