Power controller

1. A power controller comprising:

a drive circuit connected to a DC power supply to apply a first voltage to the drive circuit and configured to supply power to an external load;

a current detection circuit configured to detect a current flowing in the drive circuit by converting the current into a second voltage corresponding to the current; and

a current-voltage control unit configured to generate a reference voltage based on the first voltage corresponding to a limit value of the current flowing in the drive circuit when the first voltage is applied to the drive circuit, and configured to control the drive circuit to operate in a desired current according to the first voltage, based on a comparison result of the reference voltage and the second voltage,

wherein the current-voltage control unit includes:

a reference voltage generating unit configured to generate and output the reference voltage;

a comparator configured to output a stop signal when the second voltage is greater than the reference voltage; and

a drive circuit control unit configured to control the drive circuit to stop the supply of power to the external load by the drive circuit when the stop signal is inputted.

2. The power controller according to claim 1 ,

wherein the reference voltage generating unit includes:

an A/D converter configured to convert the first voltage, which is an analog signal, into a first digital value;

a reference voltage setting unit configured to convert the first digital value into a second digital value corresponding to the reference voltage; and

a D/A converter configured to convert the second digital value into an analog signal which is the reference voltage.

3. The power controller according to claim 2 ,

wherein the reference voltage generating unit further includes:

a storage unit storing a conversion table which represents a corresponding relationship between the first voltage and the reference voltage, and

wherein the reference voltage setting unit is configured to convert the first digital value into the second digital value corresponding to the reference voltage, based on the conversion table.

4. The power controller according to claim 3 ,

wherein the storage unit stores a plurality of conversion tables different from each other, and each representing a corresponding relationship between the first voltage and the reference voltage,

wherein the reference voltage setting unit is configured to convert the first digital value into the second digital value corresponding to the reference voltage, based on one of the conversion tables which is selected according to a mode of operation.

5. The power controller according to claim 2 ,

wherein the reference voltage generating unit further includes:

a calculating unit configured to calculate the reference voltage from the first voltage by a conversion formula; and

wherein the reference voltage setting unit is configured to convert the first digital value into the second digital value corresponding to the reference voltage based on a calculation result of the calculating unit.

6. The power controller according to claim 1 ,

wherein the drive circuit is an inverter circuit, and

wherein the drive circuit control unit includes:

a PWM generating unit configured to generate a PWM signal;

a drive control unit configured to output a drive control signal to the inverter circuit according to a duty of the PWM signal; and

a switch unit configured to shut off an output of the PWM signal to the drive control unit when the stop signal is inputted from the comparator.