Abstract: Circuits and methods for bidirectional power conversion are provided that allow mobile and other devices to generate power suitable to support multiple modes of operation. The bidirectional power converters of the present invention may operate in both step up and step down configurations rather than having a single dedicated conversion function and use many of the same components thereby reducing converter size and complexity.

Abstract: A novel system and methodology for providing a volt-second clamp. A DC/DC conversion system configured for producing an output voltage in response to an input voltage has a transformer with a primary winding responsive to the input voltage and a secondary winding for producing the output voltage. The conversion system has a power switch coupled to the primary winding of the transformer and controlled with a converter control signal, such as a PWM control signal. The power switch is further controlled by a comparator that compares an input value supplied to its input with a variable reference value so as to prevent magnetic flux density of the transformer from increasing to an undesired level. The input value of the comparator is produced by a comparator input circuit as a function of the input voltage and an on-time of the power switch. A reference circuit produces the reference value that varies as a function of the input voltage.

Abstract: A current mode power conversion system and method are described that provide a stable output voltage and a maximum-limited output current to a load. The system comprises: a feedback control linearly operable so as to control the output voltage across the load during constant load conditions, and non-linearly operable so as to control the output voltage across the load during certain detected changes in load conditions above a predetermined threshold so as to speed up the transient response of the power conversion system.

Abstract: A circuit for charging a capacitor block including series-connected capacitive elements has an input node for receiving an input, an output node coupled to the capacitor block, a third capacitive element connectable to the input node and the output node, and first and second switching circuitries coupled to the third capacitive element. A voltage sensor determines a relationship between first voltage at the first capacitive element and second voltage at the second capacitive element to separately control switching of the first and second switching circuitries in accordance with the relationship between the voltages.

Abstract: A temperature compensation circuit is used in a peak current control multi-phased DC/DC converter. Each phase has a duty cycle needed to generate a regulated output voltage of the converter. The temperature for each phase in the converter is sensed to generate corresponding first signals for all the phases. The first signals are averaged to generate a second signal corresponding to the average temperature of all the phases. For each phase, a third signal is generated corresponding to the difference between the first signal and the second signal. The third signal is then used to adjust the duty cycle of each phase to control the temperature of each phase to be substantially equal to the average temperature. In the steady state, the output voltage of the converter will be the desired voltage and the temperatures of the phases will be balanced.

Abstract: A system for providing power to a load, having first and second power supply inputs respectively responsive to first and second input signals from first and second power supply sources to supply power to the load. For example, the first power supply input may be configured for supplying the load with power received from a communication link, such as an Ethernet link, and the second power supply input may be configured for supplying the load with power from an auxiliary power source. A power converter is provided to produce an output signal for supplying power to the load in response to the second input signal. The power converter is controlled to produce the output signal in accordance with a value of the first input signal.

Abstract: An analog-to-digital converter (ADC) system configured to receive a first and a second analog quantity and to provide a plurality of numerical parameters representative of the first and second analog quantities. The ADC system includes a first, a second, and a third ADC circuit, and a digital interface circuit. The first ADC circuit is configured to provide a first code representative of the first analog quantity and to provide a first analog residue quantity representative of the first analog quantity with respect to the first code. The second ADC circuit is configured to provide a second code representative of the second analog quantity and to provide a second analog residue quantity representative of the second analog quantity with respect to the second code. The third ADC circuit is configured to receive the first and second analog residue quantities, and to provide a third digital code representative of a difference of the first and second analog residue quantities.

Abstract: A flyback converter uses primary side sensing to sense the output voltage for regulation feedback. Such sensing requires a predetermined minimum duty cycle even with very light load currents. Therefore, such a minimum duty cycle may create an over-voltage condition. In the flyback phase, after a minimum duty cycle of the power switch at light load currents, a synchronous rectifier turns off approximately when the current through the secondary winding falls to zero to create a discontinuous mode. If it is detected that there is an over-voltage, the synchronous rectifier is turned on for a brief interval to draw a reverse current through the secondary winding. When the synchronous rectifier shuts off, a current flows through the primary winding via a drain-body diode while the power switch is off. Therefore, excess power is transferred from the secondary side to the power source to reduce the over-voltage so is not wasted.

Abstract: A single stage current sense amplifier is described that generates a differential output that is proportional to a current through a sense resistor. The voltage across the sense resistor is Vsense. The current sense amplifier includes a differential transconductance amplifier having high impedance input terminals. An on-chip RC filter filters transients in the Vsense signal. A feedback circuit for each leg of the amplifier causes a pair of input transistors to conduct a fixed constant current irrespective of Vsense, which stabilizes the transconductance. A gain control resistor (Re) is coupled across terminals of the pair of input transistors and has Vsense across it. The current through the gain control resistor is therefore Vsensex1/Re. A level shifting circuit coupled to each of the input transistors lowers a common mode voltage at an output of the amplifier. Chopper circuits at the input and output cancel any offset voltages.

Abstract: High efficiency drive circuitry for a group of parallel-connected light emitting devices, in which each device is driven in series by a respective source of bias current. The maximum voltage drop among the group of biased light emitting devices is determined and in response, a control voltage to drive all the light emitting device at the lowest effective voltage for the LED group is produced.

Abstract: Frequency conversion circuitry has an input node for receiving an input signal at a first frequency and an output node for producing an output signal at a second frequency different from the first frequency. A mixer circuit is responsive to the input signal for producing a signal at the second frequency. A step down impedance transformation circuit is coupled between the input node and an input of the mixer circuit for providing input impedance of the mixer circuit lower than impedance at the input node. An amplifier circuit is coupled between an output of the mixer circuit and the output node for amplifying the signal at the second frequency produced at the output of the mixer circuit. The mixer circuit is configured for providing input impedance of the output amplifier lower than the impedance at the input node.

Abstract: A system for providing power to a powered device over a communication cable has a cable resistance measuring mechanism that determines values of response signals detected in response to supplying each of at least three reference signals over the communication cable, and determines the resistance of a pair of wires in the cable based on these values. The cable resistance measuring mechanism may be configured for determining resistance of an Ethernet cable that delivers power to the powered device in a Power over Ethernet system.

Abstract: A common mode bias circuit may include a weak common mode bias generator and a common mode bias capacitance. During a first state of the common mode bias circuit, the weak common mode bias generator may be coupled to the common mode bias capacitance and may impart to them a predefined common mode signal level. During a second state of the common mode bias circuit, the common mode bias capacitance may be coupled to differential inputs of an amplifier in a manner that establishes an input common mode level for the amplifier.

Abstract: Circuits and methods for bidirectional power conversion are provided that allow mobile and other devices to generate power suitable to support multiple modes of operation. The bidirectional power converters of the present invention may operate in both step up and step down configurations rather than having a single dedicated conversion function and use many of the same components thereby reducing converter size and complexity. In some embodiments, the converter of the present invention may be used to provide a power component of a communications link, such as a USB link.

Abstract: A flyback converter uses primary side sensing to sense the output voltage for regulation feedback. A comparator on the primary side detects whether the output voltage has exceeded a predetermined regulated voltage by a first threshold to detect an over-voltage condition, resulting from a current generated by the converter exceeding the load current. Triggering of the comparator causes the converter to enter a non-switching sleep mode, whereby the output voltage droops over a period of time. When the output voltage has drooped below the predetermined regulated voltage by a second threshold, a synchronous rectifier is controlled to turn on, then off, to generate a pulse in the primary winding. Upon detection of the pulse, the sleep mode is terminated, and normal operation resumes until a regulated voltage is achieved or until the first threshold is again exceeded by the output voltage.

Abstract: Method and system for developing low noise bandgap references. A stacked ?VBE generator is disclosed for generating ?VBE. The stacked ?VBE generator includes an error amplifier configured to generate an output based on an error signal provided by a first stack of the ?VBE generator. The first stack of the ?VBE is coupled to a first sub-circuit and the error amplifier to form a closed loop. The first sub-circuit is coupled to a power supply and ground and configured to provide a source current between the power supply and the ground. The stacked ?VBE generator also includes a second sub-circuit coupled to the output of the error amplifier, the first and second stacks, and the ground, as well as a second stack of the ?VBE generator, which is coupled to the first stack and the second sub-circuit. The ?VBE is measured at outputs of the first and second stacks and equals the sum of individual ?VBEs of the first and second stacks.

Abstract: A switch circuit is described, where a switch to be controlled is formed of two NMOS transistors having their source terminals connected together and their gate terminals connected together. Their drain terminals are the input and output terminals of the switch. A driver circuit controls a bootstrap circuit that is formed of a latching circuit and a capacitor. When the switch is in an off state, the driver circuit connects the capacitor to a charging voltage source for charging the capacitor to a bootstrap voltage, and applies a non-zero voltage across the latching circuit. When the driver circuit is controlled to turn on the switch, the driver circuit disconnects the capacitor from the charging voltage source, and the latching circuit becomes conductive and effectively connects the capacitor across the gate and source terminals of the switch to turn it on with the bootstrap voltage. The bootstrap voltage across the capacitor maintains the latching circuit in a latched conductive state.

Abstract: A flyback converter uses primary side sensing to sense the output voltage for regulation feedback. Such sensing requires a predetermined minimum duty cycle even with very light load currents. Therefore, such a minimum duty cycle may create an over-voltage condition. In the flyback phase, after a minimum duty cycle of the power switch at light load currents, a synchronous rectifier turns off approximately when the current through the secondary winding falls to zero to create a discontinuous mode. If it is detected that there is an over-voltage, the synchronous rectifier is turned on for a brief interval to draw a reverse current through the secondary winding. When the synchronous rectifier shuts off, a current flows through the primary winding via a drain-body diode while the power switch is off. Therefore, excess power is transferred from the secondary side to the power source to reduce the over-voltage so is not wasted.

Abstract: A stacked leadframe assembly is disclosed. The stacked leadframe assembly includes a first die having a surface that defines a mounting plane, a first leadframe stacked over and attached to the first die, a second die stacked over and attached to the first leadframe; and a second leadframe stacked over and attached to the second die. The leadframes have die paddles with extended side panels that have attachment surfaces in the mounting plane.

Abstract: A technique for cancelling out target IM2 components in a wireless receiver's mixer output is disclosed. A differential RF signal and a differential local oscillator (LO) signal are mixed by a mixer to demodulate the RF signal. A first common node signal is generated between a first resistor and a second resistor coupled across the mixer's differential output terminals. A second common node signal is generated between a third resistor and a fourth resistor coupled across the differential output terminals, where a capacitor is coupled between the second common node and a power supply terminal. The second common node signal provides a stable reference signal for IM2 components above a certain frequency. The two common node signals are subtracted to create a difference signal. The difference signal is scaled by a scaling factor obtained during calibration. The scaled difference signal is coupled to the mixer output to offset IM2 distortion.