Power supply

A regulated switching power supply having an output voltage, which comprises:

• means for coupling the power supply to a source of alternating current,
• means for rectifying and filtering the alternating current;
• means for feeding the filtered and rectified alternating current to a transformer having a primary and a secondary;
• output means for rectifying and filtering the current at the transformer secondary;
• means for sensing the output voltage;
• means connecting said output voltage sensing means to the output of said output rectifying and filtering means;
• a pulse width modulator having an input coupled to said output voltage sensing means;
• switching means coupled to the output of said pulse width modulator for providing a variable duty cycle waveform to said transformer primary in response to said output voltage sensing means;
• an error amplifier for providing a first error signal and a second error signal responsive to the output voltage;
• means for sensing the current level;
• means for providing a first current level set point for said current level sensing means in response to the first error signal and for providing a second current level set point for said current level sensing means in response to the second error signal;
• and
• means for providing an output signal in response to sensed current level.

A regulated power supply having an output voltage, which comprises:

• means for coupling the power supply to a source of alternating current;
• means for rectifying and filtering the alternating current;
• means for sensing the output voltage;
• an error amplifier for providing a first error signal and a second error signal responsive to the output voltage;
• means for sensing the current level;
• means for providing a first current level set point for said current level sensing means in response to the first error signal and for providing a second current level set point for said current level sensing means in response to the second error signal;
• means for providing an output signal is response to sensed ccurrent level;
• said first error signal being provided when the current is not yet in a regulated condition and the second error signal being provided when the current is in a regulated condition;
• said current set point providing means comprising a first comparator and a second comparator;
• means coupling the output of said second comparator to an input of said first comparator;
• means for providing a first input signal for said first comparator during said first error signal;
• means for providing a second different input signal for said first comparator during said second error signal;
• said second input signal provided by decreasing said input signal to said first comparator by providing an output signal from said second comparator in response to said second error signal from said error amplifier;
• means coupling the output of said error amplifier to an input of said second comparator;
• said first current level set point comprising a high point of line frequency noise and said second current level set point comprising peak current of the regulated current waveform.