Voltage sense control circuit, voltage sense control method and isolated converter thereof

A primary control circuit configured for an isolated converter having a transformer including an auxiliary winding, a primary winding and a secondary winding, a power switch coupled to said primary winding, and a rectifier device coupled to said secondary winding, the primary control circuit comprising:

• a) a compensation signal generating circuit configured to generate a compensation signal in accordance with a current flowing through said power switch that is sampled when said power switch transitions from an on state to an off state;
• b) a voltage sampling and holding circuit being configured to generate a voltage feedback signal in accordance with an output voltage feedback signal representative of a voltage across said auxiliary winding and said compensation signal such that said voltage feedback signal is independent of a forward voltage drop of said rectifier device, wherein the timing of when said voltage feedback signal is generated is controlled in accordance with said current flowing through said power switch;
• and
• c) a control circuit configured to control states of said power switch in accordance with said voltage feedback signal and a reference voltage to maintain an output voltage of said isolated converter as substantially constant.

A primary control method configured for an isolated converter having a transformer including an auxiliary winding, a primary winding and a secondary winding, a power switch coupled to said primary winding, and a rectifier device coupled to said secondary winding, the method comprising:

• a) generating a compensation signal in accordance with a current flowing through said power switch that is sampled when said power switch transitions from an on state to an off state;
• b) sampling a voltage across said auxiliary winding to generate an output voltage feedback signal;
• c) generating a voltage feedback signal in accordance with said output voltage feedback signal and said compensation signal such that said voltage feedback signal is independent of a forward voltage drop of said rectifier device, wherein the timing of when said voltage feedback signal is generated is controlled in accordance with said current flowing through said power switch;
• and
• d) controlling states of said power switch in accordance with said voltage feedback signal and a reference voltage to maintain an output voltage of said isolated converter as substantially constant.