Control circuit for an input filter capacitor in a switch-mode power supply
AssigneeRenesas Electronics America Inc.
InventorZhihong Yu
Life of this patent
Estimating the term…
Abstract
One or more embodiments relate to a control circuit for an input filter circuit in a switch mode power supply comprising a power switch and a switch controller to control the power switch to provide a regulated output voltage and current to a load. The control circuit, also referred to as a filter control circuit, can be used to detect a high voltage surge at its input and disconnect a capacitor in the input filter circuit from an input return, thereby protecting the input filter capacitor and the SMPS from damage. According to certain aspects, the control circuit can be integrated with the switch controller. Additionally, the control circuit can provide power to the switch controller at start-up.
Claims20
A Switch Mode Power Supply (SMPS) comprising:
- a primary winding of a primary side coupled to receive an input voltage via an input terminal and referenced to an input return,
- an auxiliary winding coupled to the primary winding,
- a secondary winding on a secondary side coupled to provide an output voltage, an output current, and an output power to a load, and referenced to an output return,
- a power switch on the primary side,
- a switch controller comprising a main control circuit and a filter control circuit,
- a feedback circuit coupled to sense the output voltage,
- an overvoltage protection (OVP) circuit comprising a first resistor and a second resistor to generate an OVP threshold voltage signal coupled to the input terminal,
- an input filter capacitor coupled to receive the input voltage at a first terminal,
- wherein the main control circuit is configured to control the switching operation of the power switch via a switch control signal during a normal mode,
- wherein the filter control circuit is configured to connect the input filter capacitor to the input return in response to detecting a safe voltage at the input terminal,
- wherein the filter control circuit is further configured to disconnect the input filter capacitor from the input return in response to detecting an overvoltage at the input terminal, and
- wherein the filter control circuit is further configured to turn off the switching operation of the power switch via a switch drive signal in response to detecting an overvoltage at the input terminal.
A method for a power supply comprising:
- a primary winding of a primary side coupled to receive an input voltage via an input terminal and referenced to an input return,
- an auxiliary winding coupled to the primary winding,
- a secondary winding on a secondary side coupled to provide an output voltage, an output current, and an output power to a load, and referenced to an output return,
- a power switch on the primary side,
- a switch controller comprising a main control circuit and a filter control circuit,
- a feedback circuit coupled to sense the output voltage,
- an overvoltage protection (OVP) circuit comprising a first resistor and a second resistor,
- an input filter capacitor coupled to receive the input voltage at a first terminal,
- the method comprising:
- controlling by the main control circuit a switching operation of the power switch via a switch control signal during a normal mode,
- generating an OVP threshold voltage signal by the OVP circuit,
- connecting by filter control circuit the input filter capacitor to the input return in response to detecting a safe voltage at the input terminal,
- disconnecting by filter control circuit the input filter capacitor from the input return in response to detecting an overvoltage at the input terminal, and
- turning off by the filter control circuit the switching operation of the power switch via a switch drive signal in response to detecting an overvoltage at the input terminal.
Dependencies are inferred from the claim text.