A highly efficient, tuned, switching power amplifier has components in a circuit configuration which minimizes switching losses and stored energy within the circuit. The circuit includes a pair of switches operating at the carrier frequency at substantially 50% duty. The switches are coupled through a transformer to a load, with the circuit being tuned, taking the particular load into account, so as to minimize the power loss in the switches by ensuring that immediately prior to, and during each, transition of each switch from its non-conducting (off) state to its conducting (on) state, both the voltage across the switch and the first derivative with respect to time of the voltage across the switch are substantially zero.
A power supply (10) has a first transistor (20) coupled for switching a coil current (I.sub.l9) in response to a first control signal (V.sub.C1). A second transistor (30) has a body diode (32) for discharging the coil current to produce a power factor corrected signal (V.sub.PFC). A conduction channel (31) of the second transistor is responsive to a second control signal (V.sub.C3) for developing a second coil current (I.sub.61) from the power factor corrected signal to adjust an output signal of the power supply, where the second control signal commences a time interval (TD2) after the first control signal terminates.
To provide a resonant switching power supply switch with a simple structure and little noise, a push-pull resonant switching power supply circuit includes a transformer 104, a capacitor 105, two transistors 106a and 106b (bipolar transistors or field-effect transistors), and a bias circuit 201. The transformer 104 has a rectification circuit 340 connected to its secondary winding. The capacitor 105 forms a parallel resonant circuit in combination with the transformer 104. The transistors 106a and 106b are push-pull connected to the primary winding of the transformer 104 and the bases of which are connected to a feedback winding 104 of transformer. The bias circuit 201 applies a variable bias voltage to the base of the transistors.
A resonant switching power supply has a zero voltage and zero current switch feature which can be operated in a half-bridge or a full-bridge scheme. This enables power consumption to be reduced and electromagnetic radiation to be minimized, and provides for low cost and convenient manufacture, in mass production. The power supply is not influenced by parasitic capacitance and leak inductance. The resonant switching power supply is disclosed in several different embodiments.
The present invention discloses a new family of switching amplifier classes called "class E/F amplifiers." These amplifiers are generally characterized by their use of the zero-voltage-switching (ZVS) phase correction technique to eliminate of the loss normally associated with the inherent capacitance of the switching device as utilized in class-E amplifiers, together with a load network for improved voltage and current wave-shaping by presenting class-F.sup.-1 impedances at selected overtones and class-E impedances at the remaining overtones. The present invention discloses a several topologies and specific circuit implementations for achieving such performance.
A cross-differential amplifier is provided. The cross-differential amplifier includes an inductor connected to a direct current power source at a first terminal. A first and second switch, such as transistors, are connected to the inductor at a second terminal. A first and second amplifier are connected at their supply terminals to the first and second switch. The first and second switches are operated to commutate the inductor between the amplifiers so as to provide an amplified signal while limiting the ripple voltage on the inductor and thus limiting the maximum voltage imposed across the amplifiers and switches.
