Switching power source device and control ic which are capable of performing constant power control

A control IC which is capable of performing constant power control comprising:

• a switching element connected to a primary winding of a transformer;
• a feedback input terminal configured to determine an on/off duty cycle and receive, as a feedback signal, a voltage signal which is based on an average value of current flowing through the switching element and a rectified-smoothed voltage signal from a rectifying-smoothing circuit configured to rectify and smooth an AC voltage of an AC power source;
• an error amplifier configured to amplify an error voltage between a reference voltage and the feedback signal from the feedback input terminal;
• and
• a PWM comparator configured to generate a pulse signal for turning the switching element on and off, by comparing a triangular-wave signal with an output of the error amplifier.

A control IC which is capable of performing constant power control comprising:

• a switching element connected to a primary winding of a transformer;
• an error amplifier configured to amplify an error voltage between a reference voltage and a voltage signal which is based on an average value of current flowing through the switching element;
• and
• a PWM comparator configured to generate a pulse signal for turning the switching element on and off, by comparing a triangular-wave signal with an added output obtained by adding an output of the error amplifier to a rectified-smoothed voltage signal from a rectifying-smoothing circuit configured to rectify and smooth an AC voltage of an AC power source.

A control IC which is capable of performing constant power control comprising:

• a switching element connected to a primary winding of a transformer;
• an error amplifier configured to amplify an error voltage between a reference voltage and a voltage signal which is based on an average value of current flowing through the switching element;
• and
• a PWM comparator configured to generate a pulse signal for turning the switching element on and off, by comparing a triangular-wave signal with an added output obtained by adding an output of the error amplifier to a voltage which is generated at an auxiliary winding of the transformer and proportional to a rectified-smoothed voltage signal obtained by rectification and smoothing of an AC voltage.