Start-up circuit to discharge emi filter for power saving of power supplies
AssigneeSemiconductor Components Industries, LLC
InventorsWEI-HSUAN HUANG, MENG-JEN TSAI, CHIEN-YUAN LIN, MING-CHANG TSOU, CHUAN-CHANG LI, GWO-HWA WANG
Life of this patent
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Abstract
A start-up circuit to discharge EMI filter is developed for power saving. It includes a detection circuit detecting a power source for generating a sample signal. A sample circuit is coupled to the detection circuit for generating a reset signal in response to the sample signal. The reset signal is utilized for discharging a stored voltage of the EMI filter.
Claims21
1-46. (canceled)
A discharge circuit for discharging an EMI filter that has an X-capacitor comprising:
- a monitor circuit configured for receiving a first signal from the EMI filter wherein the first signal is representative of a waveform of a power source;
- the monitor circuit configured for charging a supply voltage from the first signal;
- a first transistor of the monitor circuit configured for receiving the first signal;
- and
- the monitor circuit configured for detecting that the power source is disconnected over a period of time and responsively enable the first transistor to provide a discharging path to conduct a discharge current from the EMI filter through the first transistor for discharging a stored voltage of the EMI filter wherein the discharging path is substantially cut off when the power source is in an active state.
A method of configuring a circuit for discharging an EMI filter having an X-capacitor comprising:
- configuring a monitoring circuit to monitor an AC power source;
- configuring a detect circuit of the monitoring circuit for detecting that the AC power source is disconnected;
- configuring a delay circuit of the monitoring circuit for receiving a signal from the detect circuit in response to detecting that the power source is disconnected and to responsively provide a drive signal after a period of time;
- and
- configuring the monitoring circuit to form a discharge path for discharging a stored energy of the EMI filter in response to the drive signal, wherein the discharge path is substantially disabled in response to the monitoring circuit detecting an active state of the AC power source.
A discharge circuit for a discharging an EMI filter having an X-capacitor comprising:
- a first transistor and a second transistor coupled in series with each other and configured to receive a first signal from a power source that is filtered by the EMI filter;
- and
- a monitor circuit configured to detect that the power source is not operating for a time interval and responsively form a discharge path to conduct a discharge current through both the first transistor and the second transistor to discharge a stored value of the EMI filter.
Dependencies are inferred from the claim text.