Multiple-sampling circuit for measuring reflected voltage and discharge time of a transformer

A multiple-sarmpling circuit applied in a switching controller for power supplies, connected to an auxiliary winding of a transformer, a PWM (pulse width modulation)-and-blanking unit, and an oscillating unit;

• said multiple-sampling circuit comprising:
• a time-delay unit, connected to said PWM-and-blanking unit for receiving a switching signal, said time-delay unit generating a delay-time signal as said switching signal is disabled, said time-delay unit also generating an inverse switching signal via an inverter, wherein said switching signal is used to switch said transformer via a power switch;
• a signal-generating unit, connected to said time-delay unit for receiving said delay-time signal and said inverse switching signal;
• said signal-generating unit also receiving a reflected voltage signal from said auxiliary winding of said transformer via a voltage divider;
• said signal-generating unit generating a discharge-time signal, a first sampling signal and a second sampling signal;
• and
• a sampling unit, connected to said voltage divider, said oscillating unit, and said PWM-and-blanking unit for receiving said first sampling signal, said second sampling signal, said reflected voltage signal, a pulse signal generated by said oscillating unit, and a clear signal generated by said PWM-and-blanking unit;
• said sampling unit being controlled by said first sampling signal and said second sampling signal to sample said reflected voltage signal for generating a voltage-feedback signal.