Hughes Electronics Corporation

Kin E Shum

Craig H Becker-Irvin

A single-fault tolerant DC-to-DC converter having an output voltage clamp is capable of sourcing current to and sinking current from a load while maintaining a well regulated secondary bus voltage V.sub.bus. The clamp is disabled when the DC-to-DC converter is sourcing current so that all of the current is delivered to the load and is enabled when V.sub.bus exceeds a clamp set point voltage V.sub.clamp to sink the excess current and clamp V.sub.bus at V.sub.clamp. To provide single fault tolerance, the clamp includes a fault detection clamp element that is controlled by the DC-to-DC converter so that they operate mutually exclusively and a regulator clamp element whose resistance is set in a negative feedback control loop so that, when the fault protection clamp element is activated, both clamp elements sink the excess current and control the secondary bus voltage.

DC to DC converter with a single-fault tolerant clamp

A method and sensor for accurately measuring DC current includes an electromagnetic circuit component, such as a current transformer, having a saturated state and an unsaturated state which generates a DC current based on the DC current being measured. The current transformer includes a first circuit for generating the DC current being measured. A second circuit is electromagnetically coupled to the first circuit to generate a constant DC offset current so as to minimize error at low levels of the measured DC current. A third circuit is electromagnetically coupled to the first circuit for generating a third DC current representative of the first DC current. The first DC current is then measured based on the third DC current. The measured first DC current is then adjusted based on the added second DC current. A sampling circuit is operatively coupled to the third circuit component for sampling the third DC current during a sampling interval. A one-shot circuit is operatively coupled to the sampling circuit for controlling the sampling interval so that the measured DC current is only sampled when the current transformer is in the unsaturated state.

Method for sensing DC current and sensor for carrying out same

A full shunting BVL with current sense capability includes a pair of parallel connected switches that switch with the same duty cycle D/2 but 180 degrees out of phase to provide current from a power source through a coupled power inductor to a bus. A current transformer is provided with first and second windings connected in series with the pair of switches, respectively, and a third winding. The alternating conduction of current through the first and second windings produces a bidirectional voltage across the third sensor winding that automatically resets the current transformer's ferrite core during each cycle. As a result, the bidirectional voltage can be rectified to produce a current sense signal. The current sense signal is used to provide current-mode control to regulate the bus voltage and supply the demanded load current. The current sense signal can also be used to provide current limiting and current sharing, which allows multiple BVLs to be connected to the same solar array. This smooths the transitions in the load current supplied to the bus.

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Kin E Shum