DC-DC converter
A DC-DC converter in which a primary side and a secondary side are insulated by a transformer, includes: two diodes having anodes respectively connected to both ends of a secondary winding of the transformer and cathodes connected to each other; a series circuit composed of a resistor and a capacitor connected in series; and a snubber circuit formed by connecting the cathodes of the diodes to the connection point between the resistor and the capacitor. Surge voltage caused on the secondary side of the transformer is clamped at the voltage of the capacitor, and surge energy stored in the capacitor is regenerated to a load via the resistor. Thus, surge voltage caused on the secondary side of the transformer is suppressed with a simple configuration, and effective use of surge energy is ensured.
1. A DC-DC converter for performing DC-DC conversion of inputted DC power and outputting the converted power to a load, the DC-DC converter comprising:
an inverter having a plurality of semiconductor switching devices, for converting DC power to AC power;
a transformer having a primary side connected to AC output of the inverter;
a rectification circuit having a plurality of semiconductor devices and connected to a secondary side of the transformer; and
a snubber circuit including:
a series circuit composed of a resistor having one end connected to the positive terminal of the load, and a capacitor having one end connected to the negative terminal of the load, the resistor and the capacitor being connected in series; and
two diodes having anodes respectively connected to both ends of a secondary winding of the transformer and cathodes connected to a connection point between the resistor and the capacitor,
wherein the snubber circuit suppresses surge voltage caused on the secondary side of the transformer, and regenerates power of the capacitor to the load via the resistor.
2. The DC-DC converter according to claim 1 , wherein the cathodes of the two diodes are connected to each other, and the connection point therebetween is connected to the connection point between the resistor and the capacitor.
3. The DC-DC converter according to claim 1 , wherein two of the series circuits are provided in parallel, and the series circuits are respectively connected to the cathodes of the diodes.
4. The DC-DC converter according to claim 1 , further comprising:
means for detecting one of the values of input voltage of the inverter, voltage of the transformer, and current of the transformer; and
current interruption means for interrupting forward current of each diode of the snubber circuit,
wherein the forward current of each diode is interrupted based on the detected value.
5. The DC-DC converter according to claim 4 , wherein a semiconductor switching device to which a diode is connected in antiparallel is connected between the cathodes of the diodes and the connection point of the series circuit, thereby forming the current interruption means.
6. The DC-DC converter according to claim 1 , wherein the inverter includes: capacitors respectively connected in parallel to the semiconductor switching devices; and a reactor connected on an AC output line, whereby the semiconductor switching devices perform zero-voltage switching operations.
7. A DC-DC converter for performing DC-DC conversion of inputted DC power and outputting the converted power to a load, the DC-DC converter comprising:
an inverter having a plurality of semiconductor switching devices, for converting DC power to AC power;
a transformer having a primary side connected to AC output of the inverter;
a rectification circuit having a plurality of semiconductor devices and connected to a secondary side of the transformer; and
a snubber circuit including:
two diodes having anodes respectively connected to both ends of a secondary winding of the transformer and cathodes connected to each other;
a capacitor connected between a negative terminal of the load and the connection point between the two diodes; and
a step-down chopper circuit composed of a semiconductor switching device to which a diode is connected in antiparallel, a diode, and a reactor, and connected between the capacitor and the load,
wherein the snubber circuit suppresses surge voltage caused on the secondary side of the transformer, and regenerates power of the capacitor to the load via the step-down chopper circuit.
8. The DC-DC converter according to claim 7 , further comprising: means for detecting voltage of the capacitor, wherein the step-down chopper circuit operates so that the voltage of the capacitor will become predetermined voltage.
9. The DC-DC converter according to claim 7 , wherein the inverter includes: capacitors respectively connected in parallel to the semiconductor switching devices; and a reactor connected on an AC output line, whereby the semiconductor switching devices perform zero-voltage switching operations.