Active damping with a switched capacitor
An active damping switching system includes an active damping switching apparatus, including a damping capacitor, a damping resistor coupled to the damping capacitor, an input switch coupled to the damping capacitor, an oscillator coupled to the input switch and configured to open and close the input switch at a frequency, a direct current power source coupled to the active damping switching apparatus, a constant power load and an input filter disposed between the constant power load and the active damping switching apparatus.
1. An active damping switching system, comprising:
an active damping switching apparatus, including:
a damping capacitor;
a damping resistor coupled to the damping capacitor;
an input switch coupled to the damping capacitor;
an oscillator coupled to the input switch and configured to open and close the input switch at a frequency;
a direct current (DC) power source coupled to the active damping switching apparatus;
a constant power load; and
an input filter disposed between the constant power load and the active damping switching apparatus.
2. The system as claimed in claim 1 wherein the oscillator generates a frequency that decreases a steady state ripple voltage through the damping capacitor and the damping resistor.
3. The system as claimed in claim 2 wherein the oscillator is switched to generate the frequency during steady state operation.
4. The system as claimed in claim 1 further comprising a second switch coupled to the oscillator.
5. The system as claimed in claim 4 further comprising a transition conditions controller coupled to the second switch.
6. The system as claimed in claim 5 further comprising a zero cross detector.
7. The system as claimed in claim 6 wherein the zero cross detector is configured to switch the second switch on and off responsive to a current input.
8. The system as claimed in claim 7 wherein the zero cross detector couples a current from the input filter to the damping capacitor and the damping resistor.
9. The system as claimed in claim 6 wherein the zero cross detector is configured to pass a current from the input filter in response to transient inputs to the damping capacitor.
10. The system as claimed in claim 6 wherein the input filter is an LC filter that includes an input capacitor coupled to an input inductor.
11. The system as claimed in claim 10 further comprising a current sensor coupled to the input capacitor.
12. The system as claimed in claim 11 further comprising a low pass filter coupled between the current sensor and the zero cross detector.