The invention relates to a method and a circuit to control the output voltage and current of a switched-mode power supply. In order to restrict the output current, a voltage value proportional to the primary current of a switched-mode power supply is measured and compared to a variable reference voltage Uext the value of which is determined by the total effect of the constant charging current of a capacitor Cext and a discharge circuit operating in step with the secondary diode of the power supply. If the voltage value proportional to the primary current is bigger than said reference voltage, the switching pulses of the primary current switch are shortened. In order to restrict the output voltage, an image voltage is generated for the secondary voltage of the power supply transformer which is filtered and rectified and combined with the aforementioned reference voltage in order to produce pulse-width-modulated switching pulses of the primary current switch.

A method and circuit for controlling the output characteristics of a switched-mode power supply

In order to adjust the output voltage and output current of a galvanically isolated switched-mode power supply, on the primary side there is formed an auxiliary voltage (15) proportional to the secondary voltage, and said auxiliary voltage is studied by means of a window comparator, so that when the auxiliary voltage is within the reference window, there is applied fixed power adjustment, and when the auxiliary voltage falls outside the reference window (>max, <min), the quantity of electric power fed in by the isolation transformer of the primary side is restricted. Most advantageously the auxiliary voltage is formed by means of an auxiliary coil (12b) contained in the isolation transformer, and the reverse threshold voltages of two zener diodes represent the limit values of the reference window.

Primary adjusted switched-mode power supply

http://tudr.thapar.edu:8080/jspui/bitstream/10266/737/3/T737.pdf

Design and Fabrication of Micro-Controller based 120Hz Earth Tester

Schaltung und Verfahren zur Steuerung der Ausgangseigenschaften eines Schaltnetzteiles

A new power supply concept is described. Using the main transformer to transfer the secorrdary regulation signal on a primary winding, a new developed IC controls the primary and secondary voltages to provide more protection in case of disturbance.

http://ieeexplore.ieee.org/iel4/5591/14973/00733098.pdf

P.A. Beriand

Papers

Switch Mode Power Supply, New Concept