Ael Microtel, Ltd.

Ael Mirrotel, Ltd.

John E White

Edward T Ball

An input signal is applied to the inverting input of a class B amplifier and to the input of a limiter circuit. The square wave signal from the limiter is applied to the input of a switching amplifier which drives this amplifier between V and ground at the switching rate established by the input signal; thereby, obtaining a power control signal. The power control signal is applied to one terminal of a load and to the non-inverting input of said class B amplifier. Ignoring the input signal to the amplifier, this switches the output of the class B amplifier between V and ground at the same rate and in phase with the output from the switching amplifier. The gain of the input signal path in the amplifier is such that the input signal will just drive the output between V and ground. The switching action of the power control signal in combination with the input signal then causes the output signal across the load to have the same characteristic as the input signal but with a peak-to-peak amplitude of 2V.

Switch mode - class B power amplifier

A switched mode power supply employs a pulse width modulation controlled DC-to-DC converter to change a first voltage from a source of DC power into a regulated power source providing direct current at a second DC voltage. A transformerless current-sensing device is adapted for connection in the path between said source and said converter and provides a control signal which is representative of the current flowing in said path. A current-limiter control circuit is responsive to said control signal and provides an enabling output state when the sensed-current exceeds a predetermined value. The enabling state overrides the pulse width modulator control and inhibits the converter, thus terminating the output pulse when the sensed current exceeds said predetermined value.

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Port Moody, Canada

John E White