Abstract: A control circuit for a flyback converter is configured to adjust a conduction time of an auxiliary switch of the flyback converter in accordance with a drain-source voltage of a main switch of the flyback converter when the main switch is turned on, in order to achieve zero-voltage switching of the main switch. The flyback converter can include: a main power stage having the main switch to control energy storage and transmission of a transformer; and a clamp circuit having an auxiliary switch to provide a release path for releasing energy of leakage inductance of the transformer.

Abstract: A switching control circuit for a flyback converter having a main switch coupled to a primary winding of a transformer and a rectifier switch coupled to a secondary winding of the transformer, can include: a first voltage generating circuit configured to generate a first voltage sampling signal representing information of an input voltage; a synchronous rectification control circuit configured to adjust an on-time of the rectifier switch according to the first voltage sampling signal in order to adjust an absolute value of a negative current flowing through the secondary winding; and where the negative current is configured to discharge a parasitic capacitor of the main switch in order to reduce a drain-source voltage of the main switch.

Abstract: An apparatus including: a switching converter having a main switch configured to provide power to a transformer, an auxiliary switch configured to provide a release path for leakage inductance energy of the transformer, and a clamp capacitor coupled in series with the auxiliary switch; and a control circuit configured to control the main switch to be off and the auxiliary switch to operate to discharge the clamp capacitor when in an over-voltage protection mode. A method of controlling the switching converter can include: controlling the main switch to be off; and controlling the auxiliary switch to operate to discharge the clamp capacitor when in an over-voltage protection mode.

Abstract: A method of controlling an isolated switching converter having an output voltage that is adjustable, can include: sampling an output voltage of the isolated switching converter; setting an overvoltage protection threshold corresponding to the output voltage of the isolated switching converter when the isolated switching converter enters a protection mode; and triggering the overvoltage protection by comparing an output voltage feedback signal representing the output voltage against the overvoltage protection threshold.

Abstract: A method of controlling an isolated switching converter having an output voltage that is adjustable, can include: generating an output voltage setting signal characterizing an expected output voltage of a load; increasing a time period when an output voltage reference signal changes from a current value to the output voltage setting signal; and making overvoltage protection not trigger due to a change of the output setting signal.

Abstract: A control circuit for driving a power switch in a switching power supply can include: a start-up transistor having a drain coupled to a drain of the power switch, and a source coupled to a drain voltage detecting circuit; a gate voltage detecting circuit configured to detect a gate voltage of the power switch, to compare the gate voltage against a first threshold voltage, and to change an on drive current and an off drive current in response thereto; and the drain voltage detecting circuit being configured to detect a drain voltage of the power switch, to compare the drain voltage against a second threshold voltage, and to change the on drive current and the off drive current in response thereto.

Abstract: A control circuit for a flyback converter is configured to adjust a conduction time of an auxiliary switch of the flyback converter in accordance with a drain-source voltage of a main switch of the flyback converter when the main switch is turned on, in order to achieve zero-voltage switching of the main switch. The flyback converter can include: a main power stage having the main switch to control energy storage and transmission of a transformer; and a clamp circuit having an auxiliary switch to provide a release path for releasing energy of leakage inductance of the transformer.

Abstract: A control circuit for a flyback converter is configured to adjust a conduction time of an auxiliary switch of the flyback converter in accordance with a drain-source voltage of a main switch of the flyback converter when the main switch is turned on, in order to achieve zero-voltage switching of the main switch. The flyback converter can include: a main power stage having the main switch to control energy storage and transmission of a transformer; and a clamp circuit having an auxiliary switch to provide a release path for releasing energy of leakage inductance of the transformer.

Abstract: A method of controlling an isolated converter can include: (i) sampling and holding an output voltage of the isolated converter during a present switching cycle to generate a reference voltage signal that is proportional to the output voltage; (ii) comparing, in a predetermined time interval before a next switching cycle, the output voltage against the reference voltage signal, and activating a wake-up signal when the output voltage is less than the reference voltage signal, in order to control a voltage at a secondary winding to represent a variation of the output voltage; (iii) detecting a voltage of the primary winding or the secondary winding, and generating a voltage detection signal; and (iv) controlling the power switch according to the voltage detection signal, in order to maintain the output voltage as an expected voltage.

Abstract: A switching control circuit for a flyback converter having a main switch coupled to a primary winding of a transformer and a rectifier switch coupled to a secondary winding of the transformer, can include: a first voltage generating circuit configured to generate a first voltage sampling signal representing information of an input voltage; a synchronous rectification control circuit configured to adjust an on-time of the rectifier switch according to the first voltage sampling signal in order to adjust an absolute value of a negative current flowing through the secondary winding; and where the negative current is configured to discharge a parasitic capacitor of the main switch in order to reduce a drain-source voltage of the main switch.

Abstract: A method of controlling a secondary-side rectifier switch of a flyback converter, can include: detecting a slope parameter of a secondary-side detection voltage along a predetermined direction, where the secondary-side detection voltage is configured to represent a voltage across a secondary winding of the flyback converter; and controlling the secondary-side rectifier switch to turn on when the slope parameter is greater than a slope parameter threshold, and a relationship between the secondary-side detection voltage and the ON threshold meets a predetermined requirement.

Abstract: An apparatus including: a switching converter having a main switch configured to provide power to a transformer, an auxiliary switch configured to provide a release path for leakage inductance energy of the transformer, and a clamp capacitor coupled in series with the auxiliary switch; and a control circuit configured to control the main switch to be off and the auxiliary switch to operate to discharge the clamp capacitor when in an over-voltage protection mode. A method of controlling the switching converter can include: controlling the main switch to be off; and controlling the auxiliary switch to operate to discharge the clamp capacitor when in an over-voltage protection mode.

Abstract: A method of controlling an isolated switching converter having an output voltage that is adjustable, can include: sampling an output voltage of the isolated switching converter; setting an overvoltage protection threshold corresponding to the output voltage of the isolated switching converter when the isolated switching converter enters a protection mode; and triggering the overvoltage protection by comparing an output voltage feedback signal representing the output voltage against the overvoltage protection threshold.

Abstract: A method of controlling an isolated switching converter having an output voltage that is adjustable, can include: generating an output voltage setting signal characterizing an expected output voltage of a load; increasing a time period when an output voltage reference signal changes from a current value to the output voltage setting signal; and making overvoltage protection not trigger due to a change of the output setting signal.

Abstract: A control circuit for a flyback converter is configured to adjust a conduction time of an auxiliary switch of the flyback converter in accordance with a drain-source voltage of a main switch of the flyback converter when the main switch is turned on, in order to achieve zero-voltage switching of the main switch. The flyback converter can include: a main power stage having the main switch to control energy storage and transmission of a transformer; and a clamp circuit having an auxiliary switch to provide a release path for releasing energy of leakage inductance of the transformer.

Abstract: A voltage sense control circuit configured for an isolated converter can include: a current sampling and holding circuit configured to sample a current through a power switch to obtain a voltage sense signal that represents current information of the power switch, where the voltage sense signal is in proportion to a forward voltage drop of a rectifier device; a compensation signal generating circuit configured to generate a first current signal according to the voltage sense signal, and to generate a compensation signal according to the first current signal to compensate an output voltage feedback signal of the isolated converter to obtain a voltage feedback signal; and a voltage sampling and holding circuit configured to sample and hold the voltage feedback signal to regulate an output voltage of the isolated converter to be stable.

Abstract: An active clamp control circuit for a flyback converter can be configured to: control turn-on states of a main switch and an auxiliary switch to make the auxiliary switch turn on for a first time period in at least one switching period, and to make the main switch turn on for a second time period in each switching period, where the first and second time periods are non-overlapping periods of the switching period; and compare a peak value of an inductor current flowing through the main switch against a first threshold to adjust the first time period of the auxiliary switch when the peak value of the inductor current is greater than or equal to the first threshold, such that the first time period is directly proportional to the peak value of the inductor current.

Abstract: A control circuit can include: a blanking time control circuit configured to generate a blanking control signal according to a peak current of a main switch of a power stage circuit of a flyback converter; a sampling time control circuit configured to generate a sampling time control signal according to the blanking control signal and a feedback voltage signal; and a voltage detection circuit configured to receive the feedback voltage signal and the sampling time control signal, and to determine the time of detecting the feedback voltage signal according to the sampling time control signal to obtain a detection signal for controlling the main switch, where the voltage detection circuit stops detecting the feedback voltage signal when the blanking control signal is active, and the period during which the blanking control signal is active is adjustable along with the peak current.

Abstract: An active clamp control circuit for a flyback converter can be configured to: control turn-on states of a main switch and an auxiliary switch to make the auxiliary switch turn on for a first time period in at least one switching period, and to make the main switch turn on for a second time period in each switching period, where the first and second time periods are non-overlapping periods of the switching period; and compare a peak value of an inductor current flowing through the main switch against a first threshold to adjust the first time period of the auxiliary switch when the peak value of the inductor current is greater than or equal to the first threshold, such that the first time period is directly proportional to the peak value of the inductor current.

Abstract: A method of controlling a secondary-side rectifier switch of a flyback converter, can include: detecting a slope parameter of a secondary-side detection voltage along a predetermined direction, where the secondary-side detection voltage is configured to represent a voltage across a secondary winding of the flyback converter; and controlling the secondary-side rectifier switch to turn on when the slope parameter is greater than a slope parameter threshold, and a relationship between the secondary-side detection voltage and the ON threshold meets a predetermined requirement.