Switch mode power supply and method for operating the switch mode power supply

1. A switch mode power supply, comprising:

a switch element; and

a control for operative coupling to a DC link of a converter having a main contactor electrically connected to an auxiliary contactor which is electrically connected in series with a resistor, the control controlling the switch element and the switch mode power supply being electrically connected in parallel to a capacitor of the DC link;

wherein the switch mode power supply has a start-up delay such that control of the switch element is blocked during the start-up delay, after a DC link voltage, applied to an input-side of the switch mode power supply, at the DC link reaches a specified threshold value, and is blocked during the start-up delay until a predetermined start delay period (T), which is longer than a time interval for charging the DC link, has elapsed.

2. The switch mode power supply as claimed in claim 1 , further comprising:

a switching circuit for detecting a voltage rise at an input side; and

a blocking circuit for blocking the control of the switch element during the predetermined start delay period (T).

3. The switch mode power supply as claimed in claim 2 , wherein the switch mode power supply comprises a dual in-line package (DIP) switch for activating the predetermined start-up delay.

4. The switch mode power supply as claimed in claim 1 , wherein the switch mode power supply comprises a dual in-line package (DIP) switch for activating the predetermined start-up delay.

5. The switch mode power supply as claimed in claim 1 , wherein the predetermined start delay period (T) is adjustable via operating means of the switch mode power supply.

6. The switch mode power supply as claimed in claim 5 , wherein the switch mode power supply comprises a function switch for setting the predetermined start delay period (T).

7. The switch mode power supply as claimed in claim 4 , wherein the DIP switch comprises a function switch for setting the predetermined start delay period (T).

8. The switch mode power supply as claimed in claim 5 , wherein the switch mode power supply comprises a signaling element for setting the predetermined start delay period (T).

9. The switch mode power supply as claimed in one of claim 1 , wherein the switch mode power supply supplies a control of the converter.

10. The switch mode power supply as claimed in claim 1 , wherein at least one of the converter and a peripheral of the converter is supplied by the switch mode power supply.

11. The switch mode power supply as claimed in claim 1 , wherein the predetermined start delay period (T) is approximately 10 seconds.

12. A method for operating a switch mode power supply, comprising:

detecting a threshold value (Us) of a DC link voltage (U, U′) applied to an input-side of the switch mode power supply at a DC link of a converter having a main contactor electrically connected to an auxiliary contactor which is electrically connected in series with a resistor such that a predetermined start delay period (T) commences after the threshold value (Us) is reached, the switch mode power supply being electrically connected in parallel to a capacitor of the DC link; and

blocking control of a switch element of the switch mode power supply after a voltage at the DC link reaches a specified threshold value after a start-up delay (t0) and until the predetermined start delay period (T), which is longer than a time interval for charging the DC link, has elapsed.

13. The method as claimed in claim 12 , further comprising:

activating a programming mode via a function switch;

outputting repeated signals by a signaling element during the programming mode to indicate the predetermined start delay period (T) to be set, and

wherein the predetermined start delay period (T) is specified by renewed actuation of the function switch.

14. The method as claimed in claim 12 , wherein the predetermined start delay period (T) is approximately 10 seconds.