Soft switching inverter device and method
An inverter comprises a first switch coupled to an input of an output filter and a positive dc bus, a second switch coupled to the input of the output filter and a negative dc bus, a first freewheeling apparatus coupled to the first switch, the second switch and ground, a first soft switching network coupled to the first freewheeling apparatus and the first switch, wherein the first soft switching network is configured such that the first switch is of a first zero voltage transition during a turn-on process of the first switch and a second soft switching network coupled to the first freewheeling apparatus and the second switch, wherein the second soft switching network is configured such that the second switch is of a second zero voltage transition during a turn-on process of the second switch.
1. An apparatus comprising:
a soft switching network coupled to a power converter comprising a main switch, a freewheeling apparatus and an output filter formed by an inductor and a capacitor, wherein the freewheeling apparatus is connected between an input of the output filter and a common node of two input capacitors, and wherein the soft switching network comprises:
a magnetic device, an auxiliary switch and a plurality of diodes, and wherein the soft switching network is configured such that:
the main switch is of zero voltage switching; and
the auxiliary switch is of zero current switching, wherein the auxiliary switch is configured to be turned on prior to a zero voltage transition of the main switch and be turned off after the zero voltage transition.
2. The apparatus of claim 1 , wherein:
the power converter is selected from the group consisting of an inverter, a multilevel inverter, a step-down converter, a step-up converter and any combinations thereof.
3. The apparatus of claim 1 , wherein:
the main switch is selected from the group consisting of an insulated gate bipolar transistor (IGBT) device, a metal oxide semiconductor field-effect transistor (MOSFET) device, an integrated gate commutated thyristor (IGCT) device, a gate turn-off thyristor (GTO) device, a silicon controlled rectifier (SCR) device, a junction gate field-effect transistor (JFET) device, a MOS controlled thyristor (MCT) device and any combinations thereof.
4. The apparatus of claim 1 , wherein the soft switching network comprises:
a transformer having:
a first terminal coupled to the main switch through the auxiliary switch;
a second terminal coupled to an input of the output filter;
a third terminal connected with the second terminal; and
a fourth terminal, wherein the fourth terminal and the second terminal share a same polarity;
a first diode coupled between the first terminal and an input terminal of the power converter;
a second diode coupled between the fourth terminal and the input terminal of the power converter; and
a third diode coupled between the third terminal and the input terminal of the power converter.
5. The apparatus of claim 1 , wherein:
the soft switching network comprises:
an inductor having a first terminal coupled to the main switch through the auxiliary switch;
a first diode coupled between the first terminal of the inductor and an input terminal of the power converter; and
a second diode coupled between a second terminal of the inductor and the input terminal of the power converter.
6. The apparatus of claim 1 , wherein:
the soft switching network comprises:
an inductor having a first terminal coupled to the main switch through the auxiliary switch;
a first diode and a second diode connected in series and further coupled between the first terminal of the inductor and an input terminal of the power converter; and
a third diode coupled between a second terminal of the inductor and the input terminal of the power converter; and
an auxiliary capacitor coupled between the second terminal of the inductor and a common node of the first diode and the second diode.
7. A method comprising:
providing a soft switching network coupled to a main switch, a freewheeling apparatus and an output filter of a power converter, wherein the freewheeling apparatus is connected between an input of the output filter and a common node of two input capacitors, and wherein the soft switching network comprises:
a magnetic device;
an auxiliary switch connected in series with the magnetic device; and
a plurality of diodes coupled to the magnetic device;
prior to a zero voltage transition of the main switch, turning on the auxiliary switch; and after the zero voltage transition, turning off the auxiliary switch.
8. The method of claim 7 , further comprising:
coupling a plurality of input capacitors to a dc input power source, wherein the plurality of input capacitors are connected in series and a common node of the plurality of input capacitors is connected to ground;
coupling a first main switch between the output filter and a first output terminal of the dc input power source;
coupling a second main switch between the output filter and a second output terminal of the dc input power source;
coupling the freewheeling apparatus between the output filter and ground;
coupling a first soft switching network to the first main switch; and
coupling a second soft switching network to the second main switch.
9. The method of claim 7 , wherein:
the auxiliary switch is of a zero current transition during a turn-off process of the auxiliary switch.
10. The method of claim 7 , wherein:
the magnetic device is a transformer, and wherein:
the transformer having a first terminal coupled to the main switch through the auxiliary switch, a second terminal coupled to an input of the output filter, a third terminal connected with the second terminal and a fourth terminal, wherein the fourth terminal and the second terminal share a same polarity;
a first diode coupled between the first terminal and an input terminal of the power converter;
a second diode coupled between the fourth terminal and the input terminal of the power converter; and
a third diode coupled between the third terminal and the input terminal of the power converter.