Power converter circuit and power limit control circuit thereof
AssigneeRichtek Technology Corporation
InventorTzu-Chen Lin
Life of this patent
Estimating the term…
Abstract
A power converter circuit includes a transformer for converting a primary side voltage to a secondary side voltage and generating an output current. A power limit control unit senses the secondary side voltage to obtain a waveform feature of the primary side voltage, and decides a target of the output current according to the waveform feature of the primary side voltage. When the primary side voltage drops to a threshold, the output current is reduced.
Claims18
A power converter circuit, comprising:
- a transformer, including a primary winding configured to receive a primary side voltage at a primary side of the transformer and a secondary winding configured to generate a secondary side voltage and an output current at a secondary side of the transformer, wherein the primary side voltage has a waveform that includes at least a part of a semi-sinusoidal waveform;
- a switch, coupled to the primary winding to determine a primary side current flowing through the primary winding;
- a switch control unit at the primary side of the transformer, configured to operably control the switch to determine the primary side current;
- a power limit control unit at the secondary side of the transformer, configured to operably decide a target of the output current according to the primary side voltage, wherein the power limit control unit senses the secondary side voltage to obtain information of the primary side voltage, and sets the target of the output current according to the information of the primary side voltage such that when the primary side voltage drops to a first threshold, the output current is reduced to a constant, such that by setting the output current to the constant, the primary side voltage is controlled between the first threshold and an upper threshold of a higher voltage level than the first threshold;
- and
- a feedback unit, coupled between the power limit control unit and the switch control unit, and configured to operably provide a feedback signal from the power limit control unit to the switch control unit.
A power limit control circuit for use in a power converter circuit, wherein the power converter circuit includes a transformer, the transformer including a primary winding configured to receive a primary side voltage at a primary side of the transformer and a secondary winding configured to generate a secondary side voltage and an output current at a secondary side of the transformer, wherein the primary side voltage has a waveform that includes at least a part of a semi-sinusoidal waveform, the power limit control circuit being configured to be located at the secondary side of the transformer and configured to be coupled to the secondary winding, the power limit control circuit comprising:
- a voltage sample and hold circuit, configured to operably sense the secondary side voltage to obtain a waveform feature of the primary side voltage;
- a target determination circuit, configured to operably determine a target of the output current according to the waveform feature of the primary side voltage;
- and
- a comparison circuit, configured to operably compare the output current and the target of the output current, to generate a feedback signal which is sent to the primary side of the transformer,
- wherein the power limit control circuit sets the target of the output current such that when the primary side voltage drops to a first threshold, the output current is reduced to a constant, such that by setting the output current to the constant, the primary side voltage is controlled between the first threshold and an upper threshold of a higher voltage level than the first threshold.
Dependencies are inferred from the claim text.