DC-DC converter controller having optimized load transient response and method
View Patent ↗A power supply controller ( 25 ) is configured to accurately adjust the value of an output voltage of a power supply system ( 10 ) responsively to the output voltage increasing to an undesirable value. The controller ( 25 ) accurately limits an upper value of the output voltage during a light load condition, and rapidly reduces the value of the output voltage to a desired value. The power supply controller is configured to turn off the first output transistor but inhibit turning off the second output transistor using two different control signals.
1. A method of forming a power supply controller comprising:
configuring the power supply controller to form a drive signal having switching cycles that are used to control a first switch and a second switch to regulate an output voltage to a first value wherein a cycle includes enabling and disabling the first switch during each switching cycle and also includes enabling the second switch during each switching cycle;
configuring a first control circuit of the power supply controller to set a first state of a first control signal responsively to a second value of the output voltage that is greater than the first value and responsively inhibit subsequent switching cycles of the power supply controller; and
configuring a second control circuit to turn the first switch off and not turn the second switch off responsively to inhibiting the subsequent switching cycles during at least a portion of time that the subsequent switching cycles are inhibited.
2. The method of claim 1 further including configuring the second control circuit to force the second switch to conduct a first current during the portion of time.
3. The method of claim 2 wherein configuring the second control circuit to force the second switch to conduct the first current includes selectively coupling the second switch in a first current mirror configuration to receive a control signal having a value that is ratioed to a current of a current source.
4. The method of claim 3 wherein selectively coupling the second switch in the first current mirror configuration includes coupling a second current mirror to form a second current that is ratioed to the current of the current source.
5. The method of claim 1 wherein configuring the second control circuit includes configuring the second control circuit to control a Vgs of the second switch to be no less than a threshold voltage of the second switch.
6. The method of claim 1 further including coupling a first transistor as the first switch, and selectively coupling a second transistor as the second switch in a first current mirror configuration with a third transistor to control a first current through the second switch.
7. The method of claim 6 wherein selectively coupling the second transistor includes selectively coupling the second transistor in the first current mirror configuration responsively to a control signal received from the first control circuit.
8. A method of forming a power supply controller comprising:
configuring the power supply controller to control a first switch and a second switch to regulate an output voltage to a first value, the first switch including a first transistor;
configuring a first control circuit of the power supply controller to set a first state of a first control signal responsively to a second value of the output voltage that is greater than the first value and responsively inhibit subsequent switching cycles of the power supply controller; and
configuring a second control circuit to turn the first switch off and not turn the second switch off during at least a portion of time that the subsequent switching cycles are inhibited; and
selectively coupling a second transistor as the second switch in a first current mirror configuration with a third transistor to control a first current through the second switch and selectively coupling the first current mirror to receive a second current and force the first current to be a ratio of the second current.
9. A method of forming a power supply controller comprising:
configuring the power supply controller to control a first switch and a second switch to regulate an output voltage to a first value, the first switch including a first transistor;
configuring a first control circuit of the power supply controller to set a first state of a first control signal responsively to a second value of the output voltage that is greater than the first value and responsively inhibit subsequent switching cycles of the power supply controller; and
configuring a second control circuit to turn the first switch off and not turn the second switch off during at least a portion of time that the subsequent switching cycles are inhibited; and
selectively coupling a second transistor as the second switch in a first current mirror configuration with a third transistor to control a first current through the second switch including coupling a fourth transistor to selectively couple a control electrode of the third transistor to a first current carrying electrode of the third transistor, to a control electrode of the second transistor and to receive a second current from a second current mirror.
10. The method of claim 9 further including configuring the second current mirror to from the second current as a ratio of a third current of a current source.