US 5,387,822 AGranted

Error signal isolator circuit

AssigneeToko America, Inc.

InventorsFernando R. Martin-Lopez, Richard Redl

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Abstract

An error signal isolator circuit for conveying an error signal across an electrical isolation boundary such as an external pulse transformer employs a level shifting process whereby a controllable voltage is measured with respect to a reference voltage and, with any gain implemented in the process, is level shifted upward such that the higher potential is referenced to a supply voltage and the lower potential is used dynamically to control the magnitude of voltage conveyed in a pulse amplitude modulation (PAM) process. In the PAM process, an ON pulse is terminated by monitoring when a PAM current has increased to a predetermined and controllable level. An ON pulse is initiated by monitoring when the voltage across a clamp diode has decayed below its normal forward bias level, indicating a commensurate decay in PAM current, following termination of the previous ON pulse.

Claims3

Dependent claims

An error signal isolator circuit for conveying an error signal across an electrical isolation boundary such as an external pulse transformer, the error signal isolator circuit comprising:

error amplifier means for measuring a controllable external supply voltage with respect to a reference voltage and for providing an error voltage signal;
level shifting means coupled to the error amplifier means for receiving the error voltage signal and for altering said error voltage signal to provide a shifted error voltage signal, the magnitude of which is negatively proportional to said error voltage signal and which is referenced to the external supply voltage of said error signal isolator circuit;
and
pulse amplitude modulation means for receiving said shifted error voltage signal and for selectively switching said shifted error voltage signal across a winding of said external pulse transformer, said winding being connected to said external supply voltage.

1 more element

Dependencies are inferred from the claim text.