A controller ( 3 ) includes an AC voltage generator ( 12 ) that generates first to Nth AC voltages, a DC voltage generator ( 13 ) that converts the first to Nth AC voltages into first to Nth DC voltages, respectively, and a driver ( 14 ) that turns on and off a switch ( 1 ) based on the first to Nth DC voltages. The AC voltage generator ( 12 ) includes first to Nth isolation transformers (T 1 to TN). The primary windings of the nth and (n+1)th isolation transformers receive an AC source voltage. The nth to first isolation transformers are sequentially connected. The (n+1)th to Nth isolation transformers are sequentially connected. The first to Nth isolation transformers respectively output the first to Nth AC voltages from their respective secondary windings.
1. A controller that controls a switch including first to Nth semiconductor switching elements connected in series, the controller comprising:
an AC voltage generator that generates first to Nth AC voltages;
a DC voltage generator that converts the first to Nth AC voltages into first to Nth DC voltages, respectively; and
a driver that provides the first to Nth DC voltages to gates of the first to Nth semiconductor switching elements, respectively, to turn on the switch, and stops supplying the first to Nth DC voltages to the gates of the first to Nth semiconductor switching elements, respectively, to turn off the switch, wherein
the AC voltage generator includes first to Nth isolation transformers,
primary windings of the nth and (n+1)th isolation transformers receive an AC source voltage,
primary windings of the first to (n−1)th isolation transformers are connected to secondary windings of the second to nth isolation transformers, respectively,
primary windings of the (n+2)th to Nth isolation transformers are connected to secondary windings of the (n+1)th to (N−1)th isolation transformers, respectively,
the first to Nth isolation transformers respectively output the first to Nth AC voltages from their respective secondary windings, and
N is a natural number of two or more, and n is a natural number smaller than N.
2. The controller according to claim 1 , wherein
the first to Nth semiconductor switching elements are first to Nth insulated gate bipolar transistors, respectively.
3. The controller according to claim 2 , wherein
the switch further includes first to Nth diodes connected in antiparallel to the first to Nth insulated gate bipolar transistors, respectively.
4. The controller according to claim 1 , further comprising a determination unit that determines whether or not a commercial AC power source is normal, wherein
the switch is connected between the commercial AC power source and a load, and
the driver operates based on a determination result from the determination unit, wherein the driver turns on the switch when the commercial AC power source is normal, and turns off the switch when the commercial AC power source is not normal.
5. A controller that controls a switch including first to Nth semiconductor switching elements connected in series, the controller comprising:
an AC voltage generator that generates first to Nth AC voltages;
a DC voltage generator that converts the first to Nth AC voltages into first to Nth DC voltages, respectively; and
a driver that provides the first to Nth DC voltages to gates of the first to Nth semiconductor switching elements, respectively, to turn on the switch, and stops supplying the first to Nth DC voltages to the gates of the first to Nth semiconductor switching elements, respectively, to turn off the switch, wherein
the AC voltage generator includes first to Nth isolation transformers,
a primary winding of the nth isolation transformer receives an AC source voltage,
primary windings of the first to (n−1)th isolation transformers are connected to secondary windings of the second to nth isolation transformers, respectively,
primary windings of the (n+1)th to Nth isolation transformers are connected to secondary windings of the nth to (N−1)th isolation transformers, respectively,
the first to Nth isolation transformers respectively output the first to Nth AC voltages from their respective secondary windings, and
N is a natural number of three or more, and n is a natural number smaller than N.
6. The controller according to claim 5 , wherein
the AC voltage generator further includes an AC power source that generates the AC source voltage, and
the nth isolation transformer is provided in the AC power source.
7. The controller according to claim 5 , wherein
the first to Nth semiconductor switching elements are first to Nth insulated gate bipolar transistors, respectively.
8. The controller according to claim 7 , wherein
the switch further includes first to Nth diodes connected in antiparallel to the first to Nth insulated gate bipolar transistors, respectively.
9. The controller according to claim 5 , further comprising a determination unit that determines whether or not a commercial AC power source is normal, wherein
the switch is connected between the commercial AC power source and a load, and
the driver operates based on a determination result from the determination unit, wherein the driver turns on the switch when the commercial AC power source is normal, and turns off the switch when the commercial AC power source is not normal.