In a switching power source of the RCC system in which excited energy, accumulated in a transformer during an on-period of a main switching element, is outputted to the secondary side during an off-period, and a ringing pulse, which appears in a control coil of the transformer upon completion of the output, is fed back to the gate of the main switching element through a capacitor used for cutting a dc so that the main switching element is on-driven, a bias resistor is interpolated between the capacitor and the gate, and during the stand-by state, a control transistor is turned on, with the connecting point between them being connected to a main power-source line in a low level through a series circuit consisting of a diode, Zener diode and a resistor. Thus, a higher charge is allowed to accumulate in the capacitor, and the ringing pulse is reversely biased by the charge so as not to cause the re-starting. It becomes possible to reduce the switching frequency during the stand-by state in light load, and consequently to improve the power-conversion efficiency by using a simple construction.
In relation to a starting circuit for supplying a DC supply voltage to the gate of a main switching device at a power-on to start a switching operation, a holding circuit for holding a starting voltage obtained in the starting circuit is provided. The potential at the gate of the main switching device is increased immediately from a turn-off to turn on the main switching device repeatedly, realizing a smooth transition to the steady oscillation state. This allows the switching power supply to readily start even under the condition of a low supply voltage and a heavy load. This makes it possible to improve the starting characteristic and to allow for lower power consumption.
An isolating type self-oscillating flyback converter is disclosed, which includes a coupled transformer, a FET, a transistor and an electro-optical coupled isolating feedback unit, wherein the input terminal of the circuit is connected to the source of the FET through a primary winding of the coupled transformer, the input terminal of the circuit is connected to the collector of the transistor through a resistor R1 and another resistor R2, the source of the FET is connected to the collector of the transistor, one branch of the drain of the FET is connected to the ground through a resistor, while the other branch is connected to the base of the transistor through the parallel connection body of a resistor and a capacitor, the base of the transistor is connected to the output terminal of a secondary output winding of the coupled transformer through the electro-optical coupled isolating feedback unit; the series connection joint between the said resistor R1 and the said resistor R2 is connected to the ground through a speedup capacitor and a secondary winding of the coupled transformer; a loop for implementing the soft start is connected between the said input terminal of the circuit and the series connection joint. Thus the start current of the invention is small and the converter can keep working normally when the input voltage is high.
A switching power supply unit comprises: a transformer, a main switching element, a rectifying smoothing circuit, a mode switching circuit and a delay circuit. The transformer has a primary winding, a secondary winding and a bias winding. The main switching element is connected to the primary winding and receives an output of the bias winding as a positive feedback so as to form a ringing choke converter operating in self-excitation oscillation. The rectifying smoothing circuit is connected to the bias winding. The mode switching circuit is turned on and off depending on whether or not the rectifying smoothing voltage of the rectifying smoothing circuit is a threshold voltage or higher. The delay circuit is coupled to the mode switching circuit and is connected between the main switching element and the bias winding and delays the output of the bias winding and applies the delayed output to the main switching element. The delay circuit lengthens a turn-on delay time when the mode switching circuit detects an output voltage of the rectifying smoothing circuit which is less than the threshold voltage.
Switching converter to convert an input direct current (U.sub.E) into at least one output direct current (U.sub.A), wherein an internal auxiliary voltage (U.sub.H1, U.sub.H2) is derived from at least one auxiliary winding (W.sub.H1, W.sub.H2) of a transformer (Tr), a controllable load element (BAL) is provided for the output voltage, and a stop signal (s.sub.s) can be fed to turn the output voltage of the switching converter ON/OFF, which is used to connect the load element (BAL) to the output direct current to such an extent that a short-circuit-like condition is produced, in which the output voltage (U.sub.a) is adequately close to null, but the at least one auxiliary voltage (U.sub.H1, U.sub.H2) is adequately high to supply the units associated therewith.
A fixed frequency external power source having an external coil is inductively coupled with an implanted coil of an implanted medical device. The implant device has an electronic impedance transformer as part of its load circuit. Such electronic impedance transformer sets a proper voltage and current ratio (impedance) so that the coil set, i.e., the external coil and the implanted coil, are loaded with an optimal load. Such optimal loading, in turn, significantly minimizes any mismatch loss from the inductive link between the external coil and the implant coil, and allows wide ranges in the voltage and load resistance and coil separation, while at the same time maintaining an optimal load condition. The impedance transformer is especially applicable to fully implantable cochlear stimulation systems wherein, during one mode of operation, a relatively large power level must be transferred for charging the implanted power storage element, e.g., a rechargeable battery, but wherein another mode of operation, the implant is operated and powered from an external unit and a relatively small power level is transferred to the implant device. The ratio of these power levels may be large, e.g., about 30 to 1, and unless the coil set, i.e., the external coil and implanted coil, are altered between these different load conditions, a huge mismatch loss may occur, which mismatch greatly reduces the power transfer efficiency. The impedance transformer of the invention minimizes such a mismatch loss.
