Hewlett-packard Company

Agilent Technologies, Inc.

Keysight Technologies, Inc.

Joe E Marriott

David Paul Kjosness

Sylvia Jane Budak

John F Kenny

Michael J Benes

Lawrence T Jones

David W Ricci

David W Palermo

Thomas J Heger

Katherine Mueller

Daniel Miller

James Ressmeyer

Embodiments are described for reducing common-mode current in electronic devices. In the various embodiments, a resonant converter is employed, for example in a power supply, and the resonant converter is driven by a DC input to generate an AC primary voltage on the primary windings of a power transformer. The DC input may be derived from an AC line voltage or a DC-to-DC converter. The AC primary voltage drives the primary winding of the transformer to generate an AC secondary voltage on at least one secondary winding of the transformer. The AC secondary voltage may then drive a rectifier, which in turn drives a low-pass filter to produce a DC output voltage. Phase-shift modulation is employed which, in conjunction with the resonant converter, applies a sinusoidal waveform to the primary of the transformer resulting in a reduced amount of common-mode current injected onto the secondary.

Resonant converter for achieving low common-mode noise, along with isolated power supply and method employing the same

An apparatus and technique that reduces induced cross-talk current between transformer windings. The apparatus includes a transformer having a first secondary winding that provides a first voltage relative to earth ground, a second secondary winding that provides a second voltage relative to floating ground, and a shield disposed between the first and second secondary windings. A correction circuit connected to the first secondary winding is configured to generate a correction voltage. The correction voltage drives a shield to induce a correction current into the second secondary winding to reduce cross-talk current induced between the first and second secondary windings.

Transformer correction circuit and technique for reducing cross-talk current

A precision AC input voltage divider of input resistance Rand feedback resistance Ron a substrate is printed as a serpentine pattern for a thin line of resistive material. The input resistance is formed between a first and second terminal, and feedback resistance is formed between the second terminal and a third terminal. A first metallic conductor is formed on the substrate, connected to the first terminal, disposed to be adjacent to the input resistance, and having a distributed capacitive coupling to the input resistance that compensates for corresponding distributed stray capacitance from the input resistance to a circuit ground. A second metallic conductor is formed on the substrate, connected to the third terminal, disposed to be adjacent the feedback resistance, and having a distributed capacitive coupling to the feedback resistance that compensates for corresponding distributed stray capacitance from the feedback resistance to the circuit ground.

Precision thin film AC voltage divider

A precision AC input voltage divider on a substrate is printed as a serpentine pattern for a thin line of resistive material. Bothersome original 'bad' stray capacitances to a ground, particularly those to or from the middle of the serpentine, are effectively removed by coupling to their ungrounded ends additional 'good' stray capacitances that are themselves driven by the input voltage. The additional good stray capacitances are chosen to supply substantially the exact current needed by the original bad strays, so that the original resistive divider never &#x201c;sees&#x201d; the strays at all, and requires in addition only minimal conventional compensation by external parts. The additional good strays are obtained by a metallic conductor that is electrically connected to the input terminal, and runs adjacent to the serpentine resistance for part or all of its length.

A switching network for coaxial transmission lines switches both the center conductors and the shields to allow floating measurements and eliminate the effects of ground loops. The shields are switched even though the coaxial relays use to switch the center conductors do not themselves also switch the shields. This is accomplished by using two coaxial relays having connected center conductors, each of which coaxial relay is itself shielded, and a third relay to selectively connect and disconnect the shields of the coaxial relays. All three relays open and close in unison. Although this arrangement provides excellent isolation when open within the circuit where it is used, there is unfortunatly a coupling mechanism between pairs of such circuits having such relay arrangements that are closed. This coupling mechanism produces crosstalk between such pair of circuits. The crosstalk current tends to flow in a resonant circuit. Both the resonant peak of the crosstalk current and its non resonant magnitude can be reduced by the inclusion of magnetic cores (such as lossy ferrites) around the coaxial transmission lines as they enter and leave the coaxial relays.

Coaxial switching system with switched shields and crosstalk suppression

A switching network for coaxial transmission lines switches both the center conductors and the shields to allow floating measurements and eliminate the effects of ground loops. The shields are switched even though the coaxial relays used to switch the center conductors do not themselves also switch the shields. This is accomplished by using two coaxial relays having connected center conductors, each of which coaxial relay is itself shielded, and a third relay to selectively connect and disconnect the shields of the coaxial relays. All three relays open and close in unison. Although this arrangement provides excellent isolation when open within the circuit where it is used, there is unfortunately a coupling mechanism between pairs of such circuits having such relay arrangements that are closed. This coupling mechanism produces crosstalk between such pairs of circuits. The crosstalk current tends to flow in a resonant circuit. Both the resonant peak of the crosstalk current and its non resonant magnitude can be reduced by the inclusion of magnetic cores (such as lossy ferrites) around the coaxial transmission lines as they enter and leave the coaxial relays.

An asynchronous interface enables the transfer of information between a set of devices operating in a loop and having a wide range of operating speeds. Each device can enter a Controller active state in which it sources command frames to control the loop operation. Each device can also enter a Talker active state in which it sources Data frames on a Listener active state in which it received Data frames. The transfer of frames is coordinated by a set of handshakes which enable the frames to be transferred in an asynchronous manner.

Asynchronous interface message transmission using source and receive

A multislope A/D converter is presented which employs a multislope integration technique enabling the use of a single comparator to detect polarity changes in the integrator output voltage. The A/D converter integrates a test signal during a run-up interval and integrates a discharging signal during the run-up interval as well as during a pre-run-down interval and a run-down interval subsequent to the run-up interval. The magnitude and polarity of the discharging signal are regulated in accordance with a switching scheme that converts circuit element mismatch error into offset measurement errors which can be eliminated by subtraction. The discharging current during the pre-run-down interval ensures that the slope of the integrator output voltage at the final polarity change is independent of test signal polarity thereby avoiding a comparator hysteresis error. A decade-run-down technique is employed during the run-down interval enabling the digital conversion to be implemented on a decade counter.

Multislope converter and conversion technique

A circuit for performing dual slope integration to provide a digital measurement of an input voltage of either positive or negative polarity employs a single source of reference potential in combination with a switchable resistive network as a source of reference current.

Dual slope integration circuit

An improved feedback/compensation scheme for a precision active rectifier circuit improves the slew rate and loop gain during diode switching and thereby reduces fractional scale linearity problems.

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Loveland, CO, United States of America

Joe E Marriott