High Efficiency Stand-By Mode and normal Operation for Switching Mode Power Supply Circuit
Original Publication Date: 2005-Mar-25
Included in the Prior Art Database: 2005-Mar-25
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To achieve a high efficient Stand-By mode for switching mode power suppliers, prior solutions suffer from some disadvantages like high power consumption or high production costs. It is proposed to power the system during normal operation by auxiliary winding of the transformer. Thereby the auxiliary winding voltage is low (app. 20V), so the overall power consumption is low during normal operation. Two functions are provided by one pin: The pin represents the drain of the power device connector and the pin draws the current source from a high voltage point for the supply voltage. 1. During normal operation the supply current is provided by the auxiliary binding of the transformer. In Stand-By mode power is supplied by a switchable current source which is turned on during off_state time and turned off during on_state time only. 2. A voltage reference level for controlling the Vcc voltage regulation exists during the Stand-By mode only. When the system state switches to off_state, the Vcc capacitor gets charged by the current source. If the Vcc voltage reaches a certain level the current source will stop charging and the Vcc capacitor starts discharging itself over the integrated circuit. In Stand-By mode and off_state time the capacitor is being charged. In Stand-By mode and on_state the capacitor is not being charged.