Constant current switching power supply apparatus, method of driving it, light source driving apparatus, method of driving it, and image display apparatus

A method of driving a constant current switching power supply apparatus comprising:

• a switching element connected in series with a load, and configured to turn on and off a DC current supplied to the load;
• a current detecting element configured to detect a value of the current flowing to the load;
• and
• an analog-to-digital converter configured to convert the value of the current as detected by the current detecting element from an analog value to a digital value;
• said method comprising:
• an arithmetic processing step of performing feedback control over the current supplied to the load, based on a value obtained by multiplying a difference between a target value of the current flowing to the load and the value of the current detected by the current detecting element, by a proportional gain;
• wherein
• said arithmetic processing step sets the value of the gain to a predetermined value immediately after the switching element is turned on, and reduces the value of the gain with time after the turn on of the switching element.

A method of driving a light source driving apparatus comprising:

• a switching element connected in series with a light emitting element, and configured to turn on and off a DC current supplied to the light emitting element;
• a current detecting element configured to detect a value of the current flowing to the light emitting element;
• and
• an analog-to-digital converter configured to convert the value of the current as detected by the current detecting element from an analog value to a digital value;
• said method comprising:
• an arithmetic processing step of performing feed back control over the current supplied to the light emitting element, based on a value obtained by multiplying a deviation of the value of the current detected by the current detecting element from a target value of the current flowing to the load, by a proportional gain;
• wherein
• said arithmetic processing step sets the value of the gain to a predetermined value immediately after the switching element is turned on, and reduces the value of the gain with time after the turn on of the switching element.