A self-oscillation-resonance type power supply circuit having a stabilizer for output voltages or output currents. A transformer and two transistors (a first transistor and a second transistor) are used to form a push-pull type self-oscillation-resonance type power supply circuit. Feedback signals that change according to resonant voltages are inputted to individual gates of the first transistor and the second transistor, a controller for generating error signals corresponding to the difference between a voltage signal and a reference signal is included in the circuit, and the error signals are fed to the individual gates of the first transistor and the second transistor, whereby conduction timing of the individual transistors is changed to vary the self-oscillation frequency. When the self-oscillation frequency changes,, the amount of energy to be transferred form a resonant circuit formed by a resonance capacitor circuit and a first finding of the transformer to a second winding of the transformer so as to control output voltages.
In prior art, the operation of the switching transistors Q1 and Q2 is within a range of class-AB to class-B and they are not good at efficiency since it is difficult to change the operating point thereof. There is disclosed an innovative switching power circuit which is self-oscillated by a tertiary winding N3 so that each of the pair of switching elements Q1 and Q2 may be conducted alternately and thereby a current flowing from the centertap is switched so as to selectively flow alternately to one side of the primary winding N1 or to other side thereof to generate an AC voltage on a secondary winding N2, said switching power circuit characterized by that an operating point of the switching elements Q1, Q2 is changed from that in starting by using a DC voltage generated by a switching operation of the switching elements Q1, Q2 as an inverse bias power source for the switching elements Q1, Q2.
The invention discloses a half-bridge LLC resonant converter with a synchronous rectification function that includes a first switch; a second switch; a first transformer; a first synchronous rectifier; a second synchronous rectifier; a controller; and a second transformer. The controller of the half-bridge LLC resonant converter with a synchronous rectification function can control the first synchronous rectifier and the second synchronous rectifier directly and the connected second transformer also can control the first switch and the second switch directly. The first synchronous rectifier and second synchronous rectifier having a low conducting resistance substitute the rectifier and greatly lower the power consumption. The controller outputs a control signal to drive a transformer to output a signal to the primary winding, and its signal delay is formed by a delay of an electronic circuit and a power MOS switch of the first switch and second switch.
Universal switched power converter having a transformer that comprises a first winding (11-3) divided into two parts and having an intermediate tap (11-3-1), and a second winding (11-9) connected in cascade with rectifier means (12) and filter means (13), so that a first current flows through the part of said first winding (11-3) comprised between the end of the primary winding (11-3) connected to a first input terminal (11-1) and the intermediate tap (11-3-1) and through a second switching element (11-6) connected to the intermediate tap (11-3-1) and to a second input terminal (11-2), when the input voltage applied across the input terminals (11-1, 11-2) is close to a first predetermined voltage value and the second switching element (11-6) is in a conducting state.
