Cambridge Semiconductor Limited

Intersil Americas Inc.

Vinod A Lalithambika

David Michael Garner

Paul Thomas Ryan

Russell Jacques

Devarahandi Indika Mahesh De Silva

Catriona McKay

David Robert Coulson

Jayaraman Kumar

Mahesh Devarahandi Indika De Silva

Jay Kumar

Gehan Amaratunga

Claudio Collura

Zahid Ansari

A Johannes Schiff

Devarahandi Indika Mahaesh De Silva

Niek Van Der Dui{grave Over (j)}n Schouten

A controller, for use with an SMPS DC-DC converter, includes a PWM/PFM generator and a switch driver. The PWM/PFM generator simultaneously generates CTRLand CTRLsignals in dependence on a CTRL signal. The switch driver generates a drive signal in dependence on both the CTRLand CTRLsignals. The drive signal is used to control a power switch of the DC-DC converter. The CTRL signal is generated in dependence on a feedback signal indicative of an output voltage or current of the DC-DC converter. Regardless of the mode of the DC-DC converter, the CTRLsignal is used to control a peak current in an inductor of the DC-DC converter, and the CTRLsignal is used to control a switching frequency of the power switch. In certain embodiments, both the CTRLand CTRLsignals are varied in dependence on the feedback signal when the DC-DC converter is in a PWM-PFM mode.

PWM/PFM controller for use with switched-mode power supply

We describe a resonant discontinuous power converter including a magnetic energy storage device, and a bipolar junction transistor (BJT) switch having a collector terminal coupled to repetitively switch power from the input on and off to said magnetic energy storage device such that power is transferred from the input to the output. During an off-period of said BJT switch a voltage on said magnetic energy storage device and on said collector terminal of said BJT is at least partially resonant. The power converter includes a voltage clamping circuit to clamp a base voltage on a base terminal of said BJT during a resonant portion of said off-period to limit an excursion of a collector voltage on said collector terminal of said BJT towards or beyond an emitter voltage of said BJT during said resonant portion of said off-period, in particular to inhibit reverse bias of a base emitter junction of the transistor.

Power converters

Embodiments include a signal generator circuit for generating a time-varying signal, comprising capacitive element; FET to supply to or from the capacitive element a current matched to the FET drain current; a bias voltage generator to provide a bias voltage to the FET gate, wherein: the capacitances per unit area of the capacitive element and the FET gate are matched; the bias voltage is substantially equal to a sum of a first voltage substantially proportional to a reference voltage and a second voltage substantially proportional to temperature; the FET source-gate voltage substantially equal to the sum of the bias voltage and the gate threshold voltage, the bias voltage and a further voltage approximately equal to the gate threshold voltage summed to determine the FET source-gate voltage, the circuit to control a time period of the time-varying signal dependent on the current supply.

Signal generator

We describe a switching power converter comprising a bipolar switching device (BJT or IGBT) switching an inductive load, and including a closed-loop control system. The control system comprises a voltage sensing system to sense a voltage on a collector terminal of the switching device and provide a voltage sense signal; a controller; and a drive modulation system coupled to an output of the controller for modulating a drive to the control terminal of said bipolar switching device responsive to a controller control signal; wherein said controller is configured to monitor changes in the sensed voltage during a period when said switching device is switched on and to control said drive modulation system to control the degree of saturation of said bipolar switching device when the device is switched on and hence improve turn-off times.

Bipolar transistor drivers

This invention relates to control techniques and controllers for resonant discontinuous forward power converters (RDFCs). A method of controlling a resonant discontinuous forward converter (RDFC), said converter including a transformer with primary and secondary matched polarity windings and a switch to, in operation, cyclically switch DC power to said primary winding of said transformer, said converter further having a DC output coupled to said secondary winding of said converter, said method comprising: sensing a primary winding signal during an on period of said switch, said primary winding signal representing a current in said primary winding; comparing said sensed primary winding signal with a threshold value; and controlling one or both of an on and off duration of said switch in response to said comparison.

Forward power converter controllers

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). A controller for a resonant discontinuous forward converter (RDFC), said converter including a transformer with primary and secondary matched polarity windings and a switch to, in operation, cyclically switch DC power to said primary winding of said transformer, said converter further having a DC output coupled to said secondary winding of said converter, said controller having a primary sense input to sense a primary winding signal, said primary winding signal representing a voltage across said primary winding or across an additional winding coupled to said primary winding, and wherein said controller is configured to switch on said switch in response to detection of a reduction in a rate of change of said primary winding signal below a threshold, adjacent a substantially minimum value in an operational cycle of said sensed primary winding signal to convey power to said DC output.

This invention generally relates to saturation detection circuits, in embodiments for substantially lossless detection of saturation of power switches in power integrated circuits. We describe a saturation detection circuit for detecting saturation of a power semiconductor device, the circuit including a said power semiconductor device having an input terminal and an output terminal, a second semiconductor device connected across said input and output terminals of the power semiconductor device, and a circuit responsive to a current flowing through the second semiconductor device to detect the saturation of the power semiconductor device.

Saturation detection circuits

This invention relates to control techniques and controllers for resonant discontinuous forward power converters (RDFCs). A method of controlling a resonant discontinuous forward converter (RDFC), said converter including a transformer with primary and secondary matched polarity windings and a switch to, in operation, cyclically switch DC power to said primary winding of said transformer, said converter further having a DC output coupled to said secondary winding of said converter, said method comprising: sensing a transformer signal, said transformer signal representing a voltage across a winding of said transformer or a resonant current in a winding of said transformer; calculating a resonance period of said RDFC from said sensed transformer signal; and controlling an off duration of said switch in response to said calculated resonance period such that a sub-harmonic oscillation in said resonant voltage across said primary winding is reduced.

This invention relates to switch mode power supply (SMPS) controllers employing primary side sensing. We describe an (SMPS) controller which uses an area correlator to compare an area under a feedback signal waveform between a start point defined by said first timing signal and an end point defined by said second timing signal with a reference area. An output of the area correlator provides an error signal for regulating the SMPS output.

Switch mode power supply controllers

This invention generally relates to discontinuous conduction mode switch mode power supply (SMPS) controllers employing primary side sensing. We describe an SMPS controller which integrates a feedback signal from a point determined by a target operating voltage to a peak or trough of an oscillatory or resonant portion of the feedback signal when substantially no energy is being transferred to the SMPS output. When regulation is achieved this value should be zero; the difference from zero can be used to regulate the output voltage of the SMPS.

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.

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Cambridgeshire, United Kingdom

Vinod A Lalithambika