Primary side regulated flyback converter with calibrated output voltage

Abstract

A variable-level flyback power converter is configured to provide an accurate output voltage at various regulation levels. The variable-level flyback power converter may include a switch coupled to asecondary winding of a transformer, a diode coupled to a primary winding of the transformer, and a controller coupled to the switch. The controller may scale an initial reference voltage based on a desired output voltage and a forward voltage drop across the diode, compare the scaled reference voltage with a feedback voltage sensed at an auxiliary winding of the transformer to generate an error signal, and modulate a pulse signal provided to the switch based on the error voltage.

Description

technical field [0001] The present application relates to switching power converters, and more particularly, to switching power converters configured to provide output voltages at various regulation stages. Background technique [0002] The explosive growth of mobile electronic devices, such as smartphones and tablets, has created an increasing demand in the art for compact and efficient switching power converters so that users can recharge these devices. A flyback switching power converter is typically provided with mobile equipment because its transformer provides safe isolation from AC household electrical current. The problem introduced by this isolation is that the power switch occurs at the primary side of the transformer but the load is on the secondary side. Power switch modulation for a flyback converter requires knowledge of the output voltage on the secondary side of the transformer. Such feedback can be obtained with an opto-isolator bridged from the secondary ...

AI Technical Summary

Problems solved by technology

[0018] However, using multiple resistors and switches to trim the auxiliary winding voltage and / or the reference voltage increases the number of components required for the power converter, which increases the cost of such power converters and also increases the chance of component failure

Trimming the auxiliary winding voltage and / or the reference voltage also requires costly post-production testing

Furthermore, because each output voltage setpoint requires a different combination of resistors or voltage dividers, the number of output voltage setpoints that can be provided by trimming of the feedback voltage V_FB is limited

In practice, conventional multi-level power converters cannot continuously vary the output voltage and typically only support three to five preset voltages

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