A controller includes: first to third input terminals; connection terminals; an output terminal; a first rectifying element, connected between the first input terminal and the second input terminal with a direction from the second input terminal to the first input terminal as a forward direction; a second rectifying element, connected between a connection point between the first input terminal and the first rectifying element and the output terminal with a direction from the connection point to the output terminal as a forward direction; an FET circuit, including a first depletion type FET and at least one other FET; a resistor, connected to the second input terminal and the third input terminal; and a clamp circuit, clamping a voltage of the third input terminal to a predetermined voltage.

An integrated circuit for a power supply circuit including a transistor configured to control a current flowing through a coil. The integrated circuit is configured to drive the transistor. The integrated circuit includes: a determination circuit configured to determine whether a predetermined time period has elapsed since a power supply voltage of the integrated circuit rises to a first predetermined level; an oscillator circuit configured to output an oscillator signal, which has a first frequency before lapse of the predetermined period, and changes in a range at least from the first frequency to a second frequency higher than the first frequency after the lapse of the predetermined time period; and a driver circuit configured to switch the transistor responsive to the oscillator signal during and after the predetermined time period, the switching causing an on period of the transistor to gradually increase in the predetermined time period.

A system for extracting energy from an energy storage device configured to supply direct current (DC) energy at a nominal voltage rating comprises a first node dimensioned and arranged to receive direct current energy from the energy storage device. Embodiments include a self-oscillating circuit having primary and secondary windings wound around a ferrite core, wherein a positive terminal of the primary winding is tied to the negative terminal of the secondary winding at the first node, and wherein a positive terminal of the secondary winding is coupled to a second node, the second node being coupled to a load requiring power to be supplied at one of a voltage less than, equal to, or higher than the nominal voltage. Some embodiments further include a transistor having a base resistively coupled to a negative terminal of the primary winding and a collector coupled to the second node.

A resonant converter includes: a rectifier bridge; a first capacitor coupled across output terminals of the rectifier bridge; a diode with its anode coupled to a first terminal of the first capacitor; a second capacitor with a first terminal coupled to the cathode of the diode, and a second terminal coupled to a second terminal of the first capacitor; a first transistor having a first terminal coupled to the first terminal of the second capacitor; a second transistor having a first terminal coupled to a second terminal of the first transistor, and a second terminal coupled to the second terminal of the first capacitor; a resonant tank having a first input terminal coupled to the first terminal of the first capacitor, and a second input terminal coupled to the second terminal of the first transistor and the first terminal of the second transistor; and a rectifying and filtering circuit coupled across output terminals of the resonant tank, and configured to provide an output signal to a load.

A switching power supply circuit, which keeps an output voltage constant highly accurately by a buck-boost action, is provided. The switching power supply circuit comprises: a switching circuit formed by combining four switching elements with a coil in the shape of H; a coil current emulation circuit for generating an output voltage VC similar to a coil current; and a control circuit which, based on a feedback voltage representing an output voltage VO of the switching circuit, and the output voltage VC, performs on-off control of the switching circuit. The coil current emulation circuit has a CR integration circuit to generate the output voltage VC similar to the coil current. One of three voltages is applied to one terminal of the CR integration circuit, while a voltage proportional to the output voltage VO is applied to the other terminal of the CR integration circuit. The three voltages are a voltage proportional to an input voltage VIN, a ground voltage, and a voltage proportional to the sum of the input voltage VIN and the output voltage VO.

The invention provides a power converter comprising: an input for receiving input power with a variable nominal mains level, wherein said variable nominal mains level falls within at least 90V to 240V; a main power switch (Q1) driven by the input power, and a control circuit (Q2, Q3) for controlling a control current of the main power switch (Q1), wherein the control circuit in (Q2, Q3) is adapted to sense the level of the input power and draw current from a control terminal of the power switch (Q1) according to the level, and said control circuit is adapted to operate in linear region and increase the drawn current along with the increase of the level throughout the variable nominal mains level of the input power, wherein the control circuit comprises: a Darlington bridge with a first transistor (Q2) and a second transistor (Q3), the first transistor (Q2) with a base terminal connected to a circuit position indicative of the voltage amplitude of the input power, the second transistor (Q3) with a base terminal connected to an emitter terminal of the first transistor (Q2) and a collector terminal connected to the control terminal of the main power switch (Q1) and a collector terminal of the first transistor (Q2); and a resistor network (R3, R7) coupled to the emitter of the second transistor (Q3) for regulating the amplification of the second transistor (Q3) and keep the second transistor (Q3) working at linear region throughout the variable nominal mains level of the input power.

An LED driver, comprising: an inductive switch mode converter having an inductive component (16,22), an LED output (30) for an LED load and a main converter switch (18) for controlling a current flowing through the inductive component; a sensor (32) for generating a sensor signal indicative of the output current or voltage provided to the LED output; a feedback element (34) which provides a feedback path for feeding back the sensor signal for control of the main converter switch (18); and a processing circuit (50) for processing the sensor signal which has been fed back, wherein the processing circuit is adapted to generate an output when there is no sensor signal so as to limit the current flowing through the main converter switch when no sensor signal is present.

A flyback converter includes a primary side circuit, a secondary side circuit and a controller. The primary side circuit includes a primary winding and a main switch electrically connected to the primary winding. The secondary side circuit includes a secondary winding and an output diode electrically connected to the secondary winding and having a parasitic electrical parameter. The controller generates a correcting parameter for counteracting an effect on an output voltage of the flyback converter from the parasitic electrical parameter, wherein the parasitic electrical parameter is an equivalent series-connection resistance R.sub.d of the output diode and the secondary side circuit, and the correcting parameter is calculated based on the formula $\frac{n_p}{n_s}{I}_{\mathrm{ini}}{R}_d,$
wherein n.sub.p denotes a turns number of the primary winding, n.sub.s denotes a turns number of the secondary winding, and I.sub.ini denotes an initial current value which is detected when the main switch is conducted.

A resonant converter includes: a rectifier bridge; a first capacitor coupled across output terminals of the rectifier bridge; a diode with its anode coupled to a first terminal of the first capacitor; a second capacitor with a first terminal coupled to the cathode of the diode, and a second terminal coupled to a second terminal of the first capacitor; a first transistor having a first terminal coupled to the first terminal of the second capacitor; a second transistor having a first terminal coupled to a second terminal of the first transistor, and a second terminal coupled to the second terminal of the first capacitor; a resonant tank having a first input terminal coupled to the first terminal of the first capacitor, and a second input terminal coupled to the second terminal of the first transistor and the first terminal of the second transistor; and a rectifying and filtering circuit coupled across output terminals of the resonant tank, and configured to provide an output signal to a load.

An LED driver, comprising: an inductive switch mode converter having an inductive component (16,22), an LED output (30) for an LED load and a main converter switch (18) for controlling a current flowing through the inductive component; a sensor (32) for generating a sensor signal indicative of the output current or voltage provided to the LED output; a feedback element (34) which provides a feedback path for feeding back the sensor signal for control of the main converter switch (18); and a processing circuit (50) for processing the sensor signal which has been fed back, wherein the processing circuit is adapted to generate an output when there is no sensor signal so as to limit the current flowing through the main converter switch when no sensor signal is present.