Cambridge Semiconductor Limited

Other

Graseby Medical Limited

Redisem Ltd.

David Robert Coulson

David Michael Garner

Johan Piper

Russell Jacques

Vinod A Lalithambika

Nicolaas Van Der Duijn Schouten

Devarahandi Indika Mahesh De Silva

Niek Van Der Duijn Schouten

Jayaraman Kumar

Zahid Ansari

Philip John Moyse

Michael J Lindsey

There is provided a current control circuit for a power converter. The power converter has a primary circuit for receiving a supply current across a first supply rail and a second supply rail. There is a primary connection in the primary circuit. The power converter also has a secondary circuit providing an output current. There is a secondary connection in the secondary circuit. The secondary connection is connected to the primary connection. A controller controls one or more switches in the primary circuit to control the output current. The nature of the power converter is such that it has a reactive circuit which produces a reactive current. The current control circuit comprises a current sensing circuit connected to bypass or cancel the reactive current. The controller is connected to the current sensing circuit and controls the one or more switches based on a signal current sensed by the current sensing circuit.

Power control circuit

A power converter controller and methods for its operation are provided that can control a self-oscillating power converter that uses a Bipolar Junction Transistor (BJT) as a switch by manipulating the current flowing in a control winding. The controller is able to determine the optimum time to remove a short circuit applied to the control winding, as well as being able to determine the optimum time to pass current through the control winding. The controller can further draw power from the power converter using the control winding. The controller is capable of maintaining the midpoint voltage of the power converter in the case that the converter has more than one switch. The controller estimates the output power of the converter without requiring a connection to the secondary side of the converter transformer. The controller further controls entry and exit into a low-power mode in which converter oscillations are suppressed.

Power converter measuring the average rectified primary current

Regulating controller for controlled self-oscillating converters using bipolar junction transistors

This invention relates to SMPS controllers employing primary side sensing. We describe a system for identifying a knee point in a sensing waveform, at which the output voltage of the SMPS may be sampled accurately on the primary side. The system identifies the knee point, broadly speaking, by tracking a portion of a power transformer voltage waveform, and samples the voltage waveform at the knee point to determine the SMPS output voltage. In preferred embodiments this technique is implemented using a circuit akin to a decaying peak detector, providing a timing signal indicating detection of the knee point. Sample/hold and error amplifier circuits may be employed to achieve output voltage regulation.

Switch mode power supply controller with feedback signal decay sensing

This invention generally relates to cable compensation, and is particularly applicable to cable compensation for an AC-DC voltage converter. In one embodiment, a cable compensation apparatus for compensating voltage drop of a cable connected between an electrical power supply and an electrical device comprises: a first capacitor; a timer circuit to time a predetermined time period; a current source to supply to said first capacitor during substantially said predetermined time period a first current substantially proportional to an output current outputted by the power supply to the cable; and a control circuit to adjust an output voltage outputted by said power supply to said cable dependent on a voltage on said first capacitor. The compensation in some embodiments is programmable by means of a discrete capacitor component.

Cable compensation

This invention relates to SMPS controllers employing primary side sensing. We describe a system for identifying a knee point in a sensing waveform, at which the output voltage of the SMPS may be sampled accurately on the primary side. The system identifies the knee point by fitting a tangent to a portion of a power transformer voltage waveform, and samples the voltage waveform at the knee point to determine the SMPS output voltage. In preferred embodiments this technique is implemented using a decaying peak detector, providing a timing signal indicating detection of the knee point. Sample/hold and error amplifier circuits may be employed to achieve output voltage regulation.

Techniques for programming trimming circuitry of a power integrated circuit without the need for separate programming pins are disclosed. According to a first aspect of the invention, there is provided a power supply controller IC with internal circuitry, a plurality of external connections, the IC further comprising trimming circuitry with no external connections to the IC other than via shared ones of the external connections. The shared external connections can comprise a first connection comprising a data input for receiving data for programming the trimming circuitry, and a second, different connection comprising a select input to select between a data receiving mode for receiving data from the data input and a programming mode for programming the trimming circuitry using the received data.

Trimming circuits and methods

This invention relates to control techniques and controllers for resonant discontinuous forward power converters (RDFCs). We describe a controller for a resonant discontinuous forward converter (RDFC), said forward converter including a transformer with first and second matched polarity windings and a switch to switch dc power to said first winding of said transformer, said converter further having a dc output coupled to said second winding of said transformer, and wherein said controller has two modes, a first operational mode during which said switch is controlled to switch said dc power at a frequency which substantially coincides with a resonant frequency of operation of said RDFC such that said RDFC supplies power from said dc output, and a second, reduced power operational mode during which a drive to said switch is controlled to increase a proportion of time during which said switch is off.

Forward power converter controllers

This invention relates to methods and apparatus for sensing the output current in a switch mode power supply (SMPS) using primary side sensing. We describe a module which senses a current in a primary winding of a transformer and a voltage on a primary or auxiliary winding of the transformer, and which includes a multiplier coupled to an output of a signal averager averaging a primary winding current and to an output of a timing signal generator using the sensed voltage to signal when a secondary winding is powering an output of the SMPS, to multiply an averaged current sense signal by a fraction of a total cycle period of said SMPS during which the secondary winding is providing power to provide a signal estimating an output current of the SMPS.

Switch mode power supply systems

A discontinuous resonant forward power converter including a controller having an output coupled to a controllable switch and which is configured to control the switch such that a voltage waveform on a secondary winding of a transformer of the converter has a first portion during which the switch is on and current flows into an output node of the converter which is coupled to the output rectifier and to a smoothing capacitor, and which has a second substantially resonant portion during which the switch and an output rectifier are both off. Substantially no current flows into the output node during the second portion of said voltage waveform.

Discontinuous quasi-resonant forward converter

Switch mode power supply controllers

We describe a switch mode power supply (SMPS) controller employing a combination of pulse frequency and pulse width modulation. The controller employs a 'gear box' control scheme using two complementary control loops, one for real-time control of the SMPS using PFM and a second using a PWM control scheme which monitors the switching frequency and, at defined operating points, adjusts the pulse width up or down through a set of pre-determined values. This can be considered analogous to the gearbox of a motor vehicle with the SMPS pulse width, switching frequency and output power roughly corresponding to the vehicle's gear ratio, engine speed and road speed respectively.

Switch mode power supply control systems

This invention relates to SMPS controllers employing primary side sensing to detect a point of zero magnetic flux, at which the output voltage of the SMPS may be sampled accurately on the primary side. We describe a switch mode power supply (SMPS) controller for regulating the output voltage of an SMPS is response to a feedback signal from an auxilliary winding of a magnetic energy storage device forming part of an output circuit of the SMPS, the SMPS controller comprising: a reference level input to receive an output reference level signal; an input to receive said feedback signal, said feedback signal being responsive to a voltage on said auxilliary winding of said magnetic energy storage device; an integrator to integrate a difference between said feedback signal and a first fixed reference level signal; a first comparator to compare an output of said integrator with a second fixed reference level signal and to provide an output responsive to said comparison for regulating said SMPS output voltage.

Single ended flyback power supply controllers with integrator to integrate the difference between feedback signal a reference signal

Methods and apparatus for sensing the output current in a switch mode power supply (SMPS) using primary side sensing are described. A module senses a current in a primary winding of a transformer and a voltage on a primary or auxiliary winding of the transformer, and which includes a multiplier coupled to an output of a signal averager averaging a primary winding current and to an output of a timing signal generator using the sensed voltage to signal when a secondary winding is powering an output of the SMPS, to multiply an averaged current sense signal by a fraction of a total cycle period of said SMPS during which the secondary winding is providing power to provide a signal estimating an output current of the SMPS.

Growing community of inventors

Cambridge, United Kingdom

David Robert Coulson