Switched-mode power supply with wake-up circuitry

1. A switched-mode power supply comprising:

a switching converter operable to receive an input voltage (V IN ) and to convert the input voltage into an output voltage (V OUT ) in accordance with a switching signal (V GD ), wherein the switching converter includes a transformer providing galvanic isolation between a primary side and a secondary side of the switching converter; and

a wake-up circuit connected to the secondary side of the switching converter, the wake-up circuit operable to generate a feedback signal (V FB ) that indicates whether the output voltage (V OUT ) is greater than threshold value (V TH );

a primary side regulator operable to generate a current setpoint control signal (V CSET ) depending on a reference value (V REF ) and a measured value (V AUX ) representing the output voltage,

a primary side logic circuit operable to generate the switching signal (V GD ) depending on the control signal (V CSET ); and

a tracking unit operable to receive the feedback signal (V FB ) via a galvanically isolating component and to adjust the reference value based on the feedback signal (V FB ) from the wake-up circuit.

2. The switched-mode power supply as in claim 1 , further comprising:

a controller, coupled to the primary side of the switching converter, which includes the regulator and the tracking unit.

3. The switched-mode power supply as in claim 2 , wherein the tracking unit is operable to reduce the reference value (V REF ) if the feedback signal (V FB ) indicates, for a predetermined time interval (ΔT), that the output voltage (V OUT ) is greater than or equal to the threshold value (V TH ), and

wherein the tracking unit is operable to increase the reference value (V REF ) if the feedback signal (V FB ) indicates, for the predetermined time interval (ΔT), that the output voltage (V OUT ) is smaller than the threshold value (V TH ).

4. The switched-mode power supply as in claim 3 ,

wherein the tracking unit is operable to fix the reference value (V REF ) after the feedback signal (V FB ) has changed its state N times in a row and in each case at least the predetermined time interval (ΔT) is present between the state changes, wherein N≥2.

5. The switched-mode power supply as in claim 1 ,

wherein, in a switch-on phase, the reference value (V REF ) has a starting value (V REF0 ) that is set such that the resulting regulated output voltage (V OUT ) is less than the threshold value (V TH ).

6. The switched-mode power supply as in claim 5 ,

wherein the tracking unit is operable to, after the switch-on phase, increase the reference value (V REF ) in steps, until the feedback signal (V TH ) indicates that the resulting regulated output voltage (V OUT ) is greater than the threshold value (V TH ).

7. The switched-mode power supply as in claim 1 ,

wherein the threshold value (V TH ) is settable.

8. The switched-mode power supply as in claim 7 , further comprising:

a communication interface arranged on the secondary side, the communication interface operable to receive data that represent a desired output voltage, and to set the threshold value (V TH ) depending on the received data.

9. The switched-mode power supply as in claim 1 ,

wherein the switching converter has a primary winding (L P ), a secondary winding (L S ), an auxiliary winding (L AUX ), and an electronic switch (T 1 ), to which the switching signal (V GD ) is fed, and is connected to the primary winding (L P ).

10. The switched-mode power supply as in claim 1 ,

wherein the regulator is a digital regulator and the reference value (V REF ) is represented by a digital word.

11. The switched-mode power supply as in claim 1 , wherein the tracking unit is operable to reduce the reference value (V REF ) in response to detecting that the feedback signal (V FB ) indicates that the output voltage (V OUT ) is greater than the threshold value (V TH ); and

wherein the tracking unit is operable to increase the reference value (V REF ) in response to detecting that the output voltage (V OUT ) is less than the threshold value (V TH ).

12. The switched-mode power supply as in claim 1 , wherein the tracking unit is operable to repeatedly increase a magnitude of the reference value (V REF ) over each of multiple control cycles in response to detecting that the feedback signal (V FB ) indicates that the output voltage (V OUT ) is less than the threshold value (V TH ).

13. The switched-mode power supply as in claim 1 , wherein the primary side regulator is operable to produce the current setpoint control signal (V CSET ) based on a comparison of the measured value (Vaux) to the reference value (V REF ).

14. The switched-mode power supply as in claim 13 further comprising:

a comparator operable to compare an amount of current through a primary winding of the primary side to the current setpoint control signal (Vcset), an output of the comparator used to produce the switching signal (Vgd).

15. The switched-mode power supply as in claim 1 , wherein the tracking unit increases a magnitude of the reference voltage (Vref) in response to detecting that the feedback signal from the wake-up circuit indicates that the output voltage is below the threshold value.

16. The switched-mode power supply as in claim 15 , wherein the increased magnitude of the reference voltage (Vref) increases a magnitude of the output voltage.

17. The switched-mode power supply as in claim 15 , wherein the tracking unit is operable to repeatedly increase a magnitude of the reference value (V REF ) over each of multiple control cycles in response to detecting that the feedback signal (V FB ) indicates that the output voltage (V OUT ) is less than the threshold value (V TH ).

18. The switched-mode power supply as in claim 1 , wherein the tracking unit is operable to switch between increasing a magnitude of the reference value (V REF ) and decreasing the magnitude of the reference voltage (Vref) depending on a comparison of the output voltage (V OUT ) to the threshold value (V TH ).

19. The switched-mode power supply as in claim 1 , wherein the measured value (Vaux) is a voltage received from an auxiliary winding of the transformer; and

wherein the tracking unit is operable to generate the reference value (Vref) based on a combination of the feedback signal (Vfb) and the measured value (Vaux) received from the auxiliary winding of the transformer.

20. A method comprising:

driving a switching converter with a switching signal (V GD ), the switching signal controlling conversion of an input voltage (V IN ) into an output voltage (V OUT ), wherein the switching converter includes a transformer operable to provide galvanic isolation between a primary side and a secondary side of the switching converter;

regulating the output voltage (V OUT ) by way of a regulator arranged on the primary side that generates a current setpoint control signal (V CSET ) depending on a reference value (V REF ) and a measured value (V AUX ) representing the output voltage,

generating the switching signal (V GD ) for the switching converter depending on the current setpoint control signal (V CSET );

generating a feedback signal (V FB ) that indicates whether the output voltage (V OUT ) is greater than a threshold value (V TH ), and

transmitting the feedback signal (V FB ) via a galvanically isolating component;

adjusting the reference value (V REF ) based on the feedback signal (V FB ).

21. The method as in claim 20 , wherein adjusting the reference value (V REF ) comprises:

reducing the reference value (V REF ) if the feedback signal (V FB ) indicates, for a predetermined time interval (ΔT), that the output voltage (V OUT ) is greater than or equal to the threshold value (V TH ), and

increasing the reference value (V REF ) if the feedback signal (V FB ) indicates, for the predetermined time interval (ΔT), that the output voltage (V OUT ) is less than the threshold value (V TH ).

22. The method as in claim 21 ,

wherein the reference value (V REF ) is fixed after the feedback signal (V FB ) has changed its state N times in a row and in each case at least the predetermined time interval (ΔT) is present between the state changes, wherein N≥2.

23. The method as in claim 20 , further comprising:

in a switch-on phase of the switching converter: setting the reference value (V REF ) to a starting value (V REF0 ), wherein the starting value (V REF0 ) is set such that the resulting regulated output voltage (V OUT ) is less than the threshold value (V TH ).

24. The method as in claim 23 , further comprising:

after the switch-on phase of the switching converter: increasing the reference value (V REF ) in steps, until the feedback signal (V TH ) indicates that the resulting regulated output voltage (V OUT ) is greater than the threshold value (V TH ).

25. The method as in claim 24 further comprising:

setting the threshold value (V TH ).

26. The method as in claim 25 , wherein setting the threshold value (V TH ) comprises:

receiving data by way of a communication interface arranged on the secondary side, wherein the data represents a desired output voltage; and

setting the threshold value (V TH ) depending on the received data.

27. The method as in claim 26 ,

wherein the reference value (V REF ) is represented by a digital word.

28. The method as in claim 20 further comprising:

feeding the switching signal (V GD ) to an electronic switch (T 1 ) coupled to a primary winding (L P ) of the transformer, the switching signal controlling the primary current (i P ) flowing through the primary winding (L P ).

29. The method as in claim 28 , wherein generating the switching signal (V GD ) comprises:

determining a measured value (V CS ) for the primary current (I P );

comparing the measured value (V CS ) for the primary current (I P ) with the current setpoint control signal (V CSET );

generating the switching signal (V GD ) with a level that indicates the switching off of the electronic switch (T 1 ) as soon as the measured value (V CS ) for the primary current (I P ) reaches a value that is determined by the current setpoint control signal (V CSET ).