Power conversion with current sensing coupled through saturating element
An architecture for current-modulating power-handling circuits, such as power converters, where a small saturating inductance is used to obtain a pulse edge when the main current value crosses zero.
1. A method for detecting current zero-crossing in a current-modulating power converter, the power converter having a link reactance and multiple switches connected to drive current into or out of the link reactance, comprising:
arranging a magnetic core to saturate when current passing through the link reactance rises up to a limit;
rectifying voltage pulses occurring when current passing through the link reactance causes the magnetic core to pass out of and into saturation;
using the rectified voltage pulses to control the switches in at least partial dependence on timing of the voltage pulses;
wherein the limit at which said magnetic core saturates is about 1.6% of a maximum current through the link reactance; and
wherein said magnetic core is distinct from said link reactance.
2. The method for detecting current zero-crossing in a current-modulating power converter of claim 1 , wherein the limit at which said magnetic core saturates is about 1% of the maximum current through the link reactance.
3. The method for detecting current zero-crossing in a current-modulating power converter of claim 1 , wherein the limit at which said magnetic core saturates is about 2% of the maximum current through the link reactance.
4. The method for detecting current zero-crossing in a current-modulating power converter of claim 1 , wherein said switches are all completely bidirectional.
5. The method for detecting current zero-crossing in a current-modulating power converter of claim 1 , wherein said step of using the rectified voltage pulses controls operation of said switches to both drive energy into and extract energy from said link reactance during each half-cycle of current flow in said link reactance.
6. The method for detecting current zero-crossing in a current-modulating power converter of claim 1 , wherein said step of using the rectified voltage pulses controls operation of said switches to change from extracting energy from said link reactance, to driving energy into said link reactance, when current flow crosses zero, as indicated by the output of said magnetic core.
7. The method for detecting current zero-crossing in a current-modulating power converter of claim 1 , wherein said magnetic core saturates more than thirty times as quickly as said link reactance.
8. The method for detecting current zero-crossing in a current-modulating power converter of claim 1 , wherein said magnetic core is small enough to remain in saturation during more than 97% of the time, when said link reactance is operated at full power.
9. The method for detecting current zero-crossing in a current-modulating power converter of claim 1 , wherein said link reactance comprises a link inductor which is paralleled by a capacitor.
10. The method for detecting current zero-crossing in a current-modulating power converter of claim 1 , wherein a duty cycle of said magnetic core is about 1% of a duty cycle of said link reactance.
11. The method for detecting current zero-crossing in a current-modulating power converter of claim 1 , wherein said magnetic core has a smaller inductance than the inductance of a magnetic core in said link reactance.