Freescale Semiconductor,inc.

Vincent Teil

Matthew Bacchi

Cor Voorwinden

Philippe Debosque

In the field of step-down voltage conversion, it is known to regulate an output of a DC-DC converter circuit with both a Pulse Wave Modulation voltage signal or a Pulse Frequency Modulation voltage signal, depending upon a current demand made upon the DC-DC converter circuit. Typically, circuits to generate both voltage signals are provided and selection of the appropriate regulation mode is achieved by means of a pin and decision software controlling the pin. However, the use of the pin and the software is an overhead that is desirably avoided. Consequently, the present invention provides a voltage conversion apparatus comprising a signal analyzer to analyze a load current signal and compare a characteristic of the load current signal to at least one predetermined criterion. Regulation by the PWM signal or the PFM signal is selected in response to the evaluation of the comparison with the at least one criterion.

Voltage converter apparatus and method therefor

An electronic switch circuit includes an electronic switch having a first terminal, a second terminal and a third terminal, control means for applying to the first terminal a cyclic drive waveform which causes the electronic switch to conduct between the second and third terminals during a selected portion of each cycle of the waveform, operably coupled to the control means to control synchronisation of the cyclic drive waveform a detector operable to detect a change of direction of current flow at the second terminal of the electronic switch and means for monitoring and, where required, compensating for offset error of the detector. The electronic switch may beneficially be a synchronous rectifier. The synchronous rectifier may be used in DC-DC power converters to improve efficiency.

Electronic switch circuit, converter and method of operation

A Universal Serial Bus transmitter comprising a USBTXP input and a USBTXM input for receiving respective data signals, and a USBP driver and a USBM driver for applying the respective data signals to USBP and USBM wires respectively. The transmitter comprises a transmit signal generator responsive to an asserting edge of a signal at one of the USBP and USBM inputs to define a leading edge of a transmit signal (USBTXIP) and to a corresponding de-asserting edge of a signal at the other of the USBP and USBM inputs to define the subsequent trailing edge of said transmit signal (USBTXIP). Even if the duty cycles of the input signals USBTXP and USBTXM are substantially different from 50%, this does not cause unacceptable jitter of successive crossover points nor cause the crossover point voltage level to be outside the USB tolerance, centred on 50% of the voltage swings of the USBP and USBM signals.

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Ramonville St Agne, France

Vincent Teil