Methods and systems related to operation of a switching power converter
Operation of a switching power converter, such as to reduce voltage spikes on the secondary side of switching power converters. One example is a method of operating a switching power converter, the method comprising: sensing, by a controller of a switching power converter, a strength-selection signal; and driving, by the controller within a plurality of switching cycles, a control input of a primary electrically-controlled switch, the driving in each switching cycle at a drive strength based on the strength-selection signal.
1. A method of operating a switching power converter, the method comprising:
sensing, by a controller of a switching power converter, an input voltage supplied to the switching power converter; and
driving, by the controller within a plurality of switching cycles, a control input of a primary electrically-controlled switch, the driving in each switching cycle at a drive strength based on the input voltage,
wherein driving the control input at the drive strength further comprises:
driving at a first drive strength when the input voltage is above a predetermined threshold; and
driving at a second drive strength, higher than the first drive strength, when the input voltage is below the predetermined threshold.
2. The method of claim 1 wherein the predetermined threshold is a first predetermined threshold, wherein driving the control input at the drive strength further comprises:
driving at the first drive strength when a value indicative of load is below a second predetermined threshold; and
driving at the second drive strength, higher than the first drive strength, when the value indicative of load is above the second predetermined threshold.
3. The method of claim 1 wherein the predetermined threshold is a first predetermined threshold, wherein driving the control input at the drive strength further comprises:
driving at the first drive strength when the input voltage supplied to the switching power converter is above the first predetermined threshold and a value indicative of load is below a second predetermined threshold; and
driving at the second drive strength, higher than the first drive strength, when the input voltage is below the first predetermined threshold.
4. The method of claim 1 wherein driving at the drive strength further comprises conducting current from a voltage rail through a conduction area, the conduction area selected by the controller based on the input voltage.
5. The method of claim 1 wherein driving at the drive strength further comprises conducting current from a voltage rail through a control device, wherein a voltage of the voltage rail is selected by the controller based on the input voltage.
6. A controller for a switching power converter, the controller comprising:
a gate terminal and a sense terminal;
a gate-drive controller coupled to the gate terminal and the sense terminal, wherein the gate-drive controller comprises:
a first transistor having a first connection coupled to a voltage rail, a second connection coupled to the gate terminal, and a control input; and
a second transistor having a first connection coupled to the voltage rail, a second connection coupled to the gate terminal, and a control input; and
a PWM controller defining a gate output coupled to the gate-drive controller, and the PWM controller configured to assert and de-assert the gate output in each switching cycle of the switching power converter;
wherein the gate-drive controller is configured to:
sense, by way of the sense terminal or the gate terminal, a strength-selection signal; and
drive, responsive to each assertion of the gate output, current to the gate terminal, the driving in each switching cycle at a drive strength based on the strength-selection signal,
wherein when the gate-drive controller drives the gate terminal at the drive strength, the gate-drive controller is further configured to:
assert the control input of both the first and second transistors when the strength-selection signal is below a predetermined threshold; and
assert the control input the first transistor, and hold de-asserted the control input of the second transistor, when strength-selection signal is above the predetermined threshold.
7. The controller of claim 6 wherein when the gate-drive controller drives the gate terminal at the drive strength, the gate-drive controller is further configured to:
drive at a first drive strength when the strength-selection signal indicates an input voltage supplied to the switching power converter is above a predetermined threshold; and
drive at a second drive strength, higher than the first drive strength, when the strength-selection signal indicates the input voltage is below the predetermined threshold.
8. The controller of claim 6 wherein when the gate-drive controller drives the gate terminal at the drive strength, the gate-drive controller is further configured to:
drive at a first drive strength when the strength-selection signal indicates a value indicative of load is below a predetermined threshold; and
drive at a second drive strength, higher than the first drive strength, when the strength-selection signal indicates the value indicative of load is above the predetermined threshold.
9. The controller of claim 6 wherein when the gate-drive controller drives the gate terminal at the drive strength, the gate-drive controller is further configured to:
drive at a first drive strength when the strength-selection signal indicates an input voltage supplied to the switching power converter is above a first predetermined threshold and a value indicative of load is below a second predetermined threshold; and
drive at a second drive strength, higher than the first drive strength, when the strength-selection signal indicates the input voltage is below the first predetermined threshold.
10. The controller of claim 6 wherein when the gate-drive controller drives the gate terminal at the drive strength, the gate-drive controller is further configured to conduct current from a voltage rail through a conduction area, the conduction area selected by the gate-drive controller based on the strength-selection signal.
11. The controller of claim 6 further comprising the controller is configured to change a voltage on a voltage rail of the gate-drive controller based on the strength-selection signal.
12. A switching power converter comprising:
a primary side comprising:
a primary winding of a transformer, the primary winding defining a first lead coupled to an input voltage, and a second lead;
a primary electrically-controlled switch having a control input, a first connection coupled to the second lead, and a second connection coupled to a reference voltage on the primary side;
a secondary side comprising:
a secondary winding of the transformer, the secondary winding defining a first lead coupled to a voltage output;
a secondary rectifier associated with the secondary winding;
a controller comprising:
a gate-drive controller coupled to the control input of the primary electrically-controlled switch and the input voltage;
a PWM controller defining a gate output coupled to the gate-drive controller, and the PWM controller configured to assert the gate output in each switching cycle of the switching power converter;
wherein the gate-drive controller is configured to:
sense a strength-selection signal; and
drive, responsive to each assertion of the gate output, current to the control input of the primary electrically-controlled switch, the driving in each switching cycle at a drive strength based on the strength-selection signal.
13. The switching power converter of claim 12 wherein when the gate-drive controller drives the gate output at the drive strength, the gate-drive controller is further configured to:
drive at a first drive strength when the strength-selection signal indicates the input voltage is above a predetermined threshold; and
drive at a second drive strength, higher than the first drive strength, when the strength-selection signal indicates the input voltage is below the predetermined threshold.
14. The switching power converter of claim 12 wherein when the gate-drive controller drives the gate output at the drive strength, the gate-drive controller is further configured to:
drive at a first drive strength when the strength-selection signal indicates a value indicative of load is below a predetermined threshold; and
drive at a second drive strength, higher than the first drive strength, when the strength-selection signal indicates the value indicative of load is above the predetermined threshold.
15. The switching power converter of claim 12 wherein when the gate-drive controller drives the gate output at the drive strength, the gate-drive controller is further configured to:
drive at a first drive strength when the strength-selection signal indicates the input voltage is above a first predetermined threshold and a value indicative of load is below a second predetermined threshold; and
drive at a second drive strength, higher than the first drive strength, when the strength-selection signal indicates the input voltage is below the first predetermined threshold.
16. The switching power converter of claim 12 wherein when the gate-drive controller drives the control input at the drive strength, the gate-drive controller is further configured to conduct current from a voltage rail through a conduction area, the conduction area selected by the gate-drive controller based on the strength-selection signal.
17. The switching power converter of claim 12 wherein the gate-drive controller further comprises:
a first transistor having a control input, a first connection coupled to a voltage rail, and a second connection coupled to the control input of the primary electrically-controlled switch;
a second transistor having a control input, a first connection coupled to the voltage rail, a second connection coupled to the control input of the primary electrically-controlled switch;
wherein when the gate-drive controller drives the control input of the primary electrically-controlled switch at the drive strength, the gate-drive controller is further configured to:
assert the control input of both the first and second transistors when the strength-selection signal is below a predetermined threshold; and
assert the control input the first transistor, and hold de-asserted the control input of the second transistor, when the strength-selection signal is above the predetermined threshold.
18. The switching power converter of claim 12 wherein the controller is configured to change a voltage on a voltage rail of the gate-drive controller based on the strength-selection signal.
19. The switching power converter of claim 12 , wherein the gate-drive controller is further configured to set the drive strength to one of more than two levels based on the strength-selection signal.
20. The switching power converter of claim 12 , wherein the gate-drive controller is further configured to set the drive strength indirectly proportional to the input voltage.