Efficient low EMI switching output stages and methods

Details Efficient low EMI switching output stages and methods Efficient low EMI switching output stages and methods

2007-03-13

2007-03-13

Nguyen, Patricia (Department: 2817)

Amplifiers

With semiconductor amplifying device

Including class d amplifier

C330S264000, C330S20700P

Reexamination Certificate

active

10948586

ABSTRACT:
Efficient low EMI switching output stages and methods that may be used, by way of example, in class D amplifiers. The output stages comprise class AB output stages having complementary FETs for the output. The FETs are switched in response to a switch control signal in a manner to simultaneously switch the FETs so that both FETs are not off at the same time. The extent to which both FETs are on at the same time is controlled to maintain efficiency of the circuit, and preferably the output voltage slew rate is set by circuit parameters to a relatively low slew rate. By maintaining conduction in one or both the FETs during the transition, forced conduction through a parasitic diode in either FET, as may occur in response to an inductive load (an effect commonly called freewheeling), together with the rapid and wide voltage swing associated therewith, is avoided. The removal of dead time (time when all switches are OFF), and associated freewheeling behavior, enables a controlled reduction in the output voltage slew rate and grossly reduces EMI emissions. The invention is particularly useful for switching power level outputs, and/or where lead wires or substantial circuit traces may be connected thereto.

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