An embodiment of the present invention is a switching power supply comprising a transformer (12) with a primary (14) and two secondaries (16,18), a switching transistor (20) in series with the primary, a rectifier (22) and filter (24) on one secondary to provide regulated output power, a feedback control circuit (26) that monitors the secondary (18) and adjusts the duty cycle of an on-off control signal to the switching transistor (20) to maintain a constant output at the terminals (30,32), and a monitor (34) that detects when the power level flowing through the switching regulator has dropped to a predetermined minimum and then linearly turns on a load to the transformer (12). Transistor (20) is typically a power MOSFET. The monitor (34) tracks a summing junction current before any slope compensation is added. Load (36) is a shunt regulator that is activated when the summing junction current falls below 12% of full scale. Alternatively, the predetermined value of 12% is adjustable. The shunt regulator load (36) increases the load on secondary until the summing junction current returns to 12% of full scale.

Linear load circuit to control switching power supplies under minimum load conditions

A method of providing power regulation in power conversion equipment, where power regulation is implemented on the primary side of a transformer used to provide isolation of a power source from the load. The feedback mechanism utilizes current perturbations which are summed with the primary current in the power transformer. These perturbations are transformed with the load current to the primary side of the power transformer and extracted using signal processing means to regenerate a useful signal which is isolated from the load.

Method of feedback regulating a flyback power converter

A single ended forward converter periodically resets the transformer core to prevent saturation and returns magnetizing energy to the energy source, requiring only the addition of one resonating capacitor to the converter circuit. The transformer is reset and the energy recovered into the input voltage source by resonant commutation of the magnetizing current between the magnetizing inductance and a resonating capacitor. A resonant current path is completed during a nonconducting interval of the power transistor switch through a resonating capacitor, shunting the output rectifying diode connected to the secondary winding, and the flyback diode of the output filter to permit transfer of the transformer's magnetizing energy to the input energy source. This magnetizing energy transfer from core to capacitor to input energy source has a resonant quasi-sine waveform and utilizes the resonant properties of the network to enable its flow back into the input voltage source.

Single ended forward converter with resonant commutation of magnetizing current

A DC-to-DC converter (10) is operated in accordance with a predetermined primary circuit ON time (tON) and a sensed predetermined secondary circuit current level (IS) to provide improved charging performance and extended battery life. Energy is stored in the primary (14) of a coupled inductor (12) when power in the primary, provided by a battery (20) having an internal impedance (24) which varies over the battery's lifetime, is switched ON for a predetermined time tON. Upon expiration of time tON, power is switched OFF, whereupon stored energy is transferred to the secondary (16) via a flyback type process, thus charging a storage capacitor (28). A preventing means (56) prevents a premature switching ON of power in the primary (14) subsequent to the expiration of time tON. The energy storage cycle repeats when current (IS) sensed in the secondary decreases below a predetermined minimum current threshold (IMIN).

DC-to-DC converter using coupled inductor current sensing and predetermined on time

The high voltage generating apparatus includes a flyback transformer to be employed in television equipment and has a circuit for stabilizing a high voltage output. This circuit comprises an additive voltage generating coil, a reference voltage generating circuit, a voltage detector, a comparison amplifier, a switching circuit and a voltage multiplying rectifier circuit. The reference voltage generating circuit generates an inclined voltage in the flyback time of the horizontal deflection cycle and the voltage detector detects a mode of the high voltage output. The comparison amplifier compares an inclined voltage and a detection voltage and generates a control signal. The switching circuit operates with the control signal. With this operation, an additive voltage generated by the additive voltage generating coil is supplied to the high voltage coil of the flyback transformer through the voltage multiplying rectifier circuit. The voltage to be supplied compensates the voltage fall if the high voltage output and accordingly the high voltage output is stabilized.

High voltage generating apparatus for television equipment

A d.c. voltage converter having alternating energy intake and energy discharge phases. The converter includes a power transformer having a core and at least primary, secondary and tertiary windings associated with the core. A primary circuit including a pulse width controlled semiconductor switch connected in series with the primary winding conducts an energy intake current during the energy intake phase of the converter. A secondary circuit including a smoothing capacitor and at least one rectifier element connecting the smoothing capacitor to the secondary winding conducts an energy discharge current during the energy discharge phase on the converter. Circuit means are provided for connecting the tertiary winding to the smoothing capacitor so that, following the energy discharge phase of the converter, excess energy of the smoothing capacitor in the form of an energy feedback current is fed back into the core until the start of the next energy intake phase of the converter.

D.C. voltage converter including a pulse width controlled semiconductor switch

Der Gleichspannungswandler weist einen pulsbreitengesteuerten Halbleiterschalter auf, der in Serie zur Primarwicklung w1 eines Leistungstransformators (Tr) liegt. Die Sekundarwicklung (w2) dieses Leistungstransformators (Tr) ist uber ein Gleichrichterelement (Gr1) mit dem Giattungskondensator (Cg) und dem Lastwiderstand (RL) verbunden. Eine Tertiarwicklung (w3) des Leistungstransformators (Tr) ist derart mit dem Glattungskondensator (Cg) verbunden, das dessen uberflussige Energie im Anschlus an die Energieabgabephase des Gleichspannungswandlers bis zur nachsten Energieaufnahmephase in den Kern des Leistungstransformators (Tr) zuruckgespeist wird.

Eckhardt Grunsch

Papers

D.C. voltage converter including a pulse width controlled semiconductor switch

Direct voltage converter with a pulse width controlled semiconductor switch