The invention presents a highly efficient, tightly regulated DC-to-DC converter which can be used in various applications, especially multiple output converters. The converter uses a buck converter to produce an intermediate bus voltage. A current-fed double ended circuit, such as bridge or push-pull circuit, couples to the buck converter to provide power to outputs. The double ended circuit operates at about 50% duty. The secondary output filter inductor is not required. With 50% duty cycle operation, the secondary rectifiers are easily controlled by either a self-driven or an external driven circuit. The secondary windings can also be stacked up to simplify the transformer design. In addition, bias voltages needed for control circuitry can also be obtained by adding extra windings to the power transformer and extra rectifier devices.
There is no period of time when any of switching elements and switching elements is turned on in a certain switching frequency, any one switching element is turned on in a period of time except for a dead time period for the zero voltage switching, the switching elements and the switching elements are turned on and off while shifting the phases by 180 degrees, and switching elements are turned on during a period of time when the currents in a positive direction and an inverse direction are flowing to the output, respectively, to be operated in a discontinuous current mode.
In a power converter, the duty cycle of a primary winding circuit causes near continuous flow of power through the primary and secondary winding circuits during normal operation. By providing no regulation during normal operation, a very efficient circuit is obtained with a synchronous rectifier in the secondary operating at all times. However, during certain conditions such as start up or a short-circuit, the duty cycle of the primary may be reduced to cause freewheeling periods. A normally non-regulating isolation stage may be followed by plural non-isolating regulation stages. To simplify the gate drive, the synchronous rectifiers may be allowed to turn off for a portion of the cycle when the duty cycle is reduced. A filter inductance of the secondary winding circuit is sufficient to minimize ripple during normal operation, but allows large ripple when the duty cycle is reduced. By accepting large ripple during other than normal operation, a smaller filter inductance can be used.
A power converter nearly losslessly delivers energy and recovers energy from capacitors associated with controlled rectifiers in a secondary winding circuit, each controlled rectifier having a parallel uncontrolled rectifier. First and second primary switches in series with first and second primary windings, respectively, are turned on for a fixed duty cycle, each for approximately one half of the switching cycle. Switched transition times are short relative to the on-state and off-state times of the controlled rectifiers. The control inputs to the controlled rectifiers are cross-coupled from opposite secondary transformer windings.
A power converter nearly losslessly delivers energy and recovers energy from capacitors associated with controlled rectifiers in a secondary winding circuit, each controlled rectifier having a parallel uncontrolled rectifier. First and second primary switches in series with first and second primary windings, respectively, are turned on for a fixed duty cycle, each for approximately one half of the switching cycle. Switched transition times are short relative to the on-state and off-state times of the controlled rectifiers. The control inputs to the controlled rectifiers are cross-coupled from opposite secondary transformer windings.
A method for controlling a device including a plurality of switching devices operated in accordance with a pulse width modulation technique includes receiving a reference voltage signal associated with a first pair of the switching devices. A switching signal is generated. The first pair of switching devices are controlled based on the reference voltage signal and the switching signal in accordance with the pulse width modulation technique. A frequency of the switching signal is varied based on the value of the reference voltage signal.
