DC power supply circuit
View Patent ↗In a DC power supply circuit ( 1 ), when an instantaneous value (Vin) of a voltage from a rectifier circuit ( 2 ) is higher than or equal to a voltage (VC 2 ) across terminals of a capacitor (C 2 ), in an ON period of a switching element (Q 1 ), current flows along a first current path, from a high-potential output terminal of the rectifier, through a load ( 11 ), an inductor (L 2 ), and the switching element in the stated order, and into a low-potential output terminal of the rectifier, and in an OFF period of the switching element, current flows along a second current path, from the high-potential output terminal of the rectifier, through the load, the inductor, a diode (D 1 ), and the capacitor in the stated order, and into the low-potential output terminal of the rectifier.
1. A direct current (DC) power supply circuit comprising;
a rectifier circuit rectifying alternating current (AC) supplied thereto from an AC power supply; and
a voltage conversion circuit connected across output terminals of the rectifier circuit, converting a voltage from the rectifier circuit, and outputting a converted voltage to a load,
the voltage conversion circuit comprising:
an inductor having terminals, a first one of which is connected, via the load, to a high-potential one of the output terminals of the rectifier circuit;
a switching element connected between a second one of the terminals of the inductor and a low-potential one of the output terminals of the rectifier circuit;
a capacitor having terminals, a first one of which is connected to the low-potential one of the output terminals of the rectifier circuit; and
a first unidirectional element connected between a second one of the terminals of the capacitor and the second one of the terminals of the inductor, wherein
when an instantaneous value of the voltage from the rectifier circuit is higher than or equal to a voltage across the terminals of the capacitor,
in an ON period of the switching element, current flows along a first current path from the high-potential one of the output terminals of the rectifier circuit, through the load, the inductor, and the switching element in the stated order, and into the low-potential one of the output terminals of the rectifier circuit, and
in an OFF period of the switching element, current flows along a second current path from the high-potential one of the output terminals of the rectifier circuit, through the load, the inductor, the first unidirectional element, and the capacitor in the stated order, and into the low-potential one of the output terminals of the rectifier circuit, wherein
the voltage conversion circuit further comprises:
a second unidirectional element connected between the second one of the terminals of the capacitor and the high-potential one of the output terminals of the rectifier circuit, wherein
when the instantaneous value of the voltage from the rectifier circuit is lower than the voltage across the terminals of the capacitor,
in the ON period of the switching element, current flows along a third current path from the second one of the terminals of the capacitor, through the second unidirectional element, the load, the inductor, and the switching element in the stated order, and into the first one of the terminals of the capacitor, and
in the OFF period of the switching element, current flows along a fourth current path from the second one of the terminals of the inductor, through the first unidirectional element, the second unidirectional element, and the load in the stated order, and into the first one of the terminals of the inductor.
2. The DC power supply circuit of claim 1 , wherein
the first unidirectional element conducts current only in one direction from the second one of the terminals of the inductor to the second one of the terminals of the capacitor, and
the second unidirectional element conducts current only in one direction from the second one of the terminals of the capacitor to the high-potential one of the output terminals of the rectifier circuit.
3. The DC power supply circuit of claim 2 , wherein
the first unidirectional element is a diode, an anode of which is connected to the second one of the terminals of the inductor and a cathode of which is connected to the second one of the terminals of the capacitor, and
the second unidirectional element is a diode, an anode of which is connected to the second one of the terminals of the capacitor and a cathode of which is connected to the high-potential one of the output terminals of the rectifier circuit.
4. The DC power supply circuit of claim 1 , wherein
the power conversion circuit further comprises:
a second unidirectional element connected between the second one of the terminals of the capacitor and the high-potential one of the output terminals of the rectifier circuit; and
a third unidirectional element connected between the second one of the terminals of the inductor and the high-potential one of the output terminals of the rectifier circuit, wherein
when the instantaneous value of the voltage from the rectifier circuit is lower than the voltage across the terminals of the capacitor,
in the ON period of the switching element, current flows along a third current path from the second one of the terminals of the capacitor, through the second unidirectional element, the load, the inductor, and the switching element in the stated order, and into the first one of the terminals of the capacitor, and
in the OFF period of the switching element, current flows along a fourth current path from the second one of the terminals of the inductor, through the third unidirectional element and the load in the stated order, and into the first one of the terminals of the inductor.
5. The DC power supply circuit of claim 4 , wherein
the third unidirectional element is a diode, an anode of which is connected to the second one of the terminals of the inductor and a cathode of which is connected to the high-potential one of the output terminals of the rectifier circuit.
6. The DC power supply circuit of claim 4 , wherein
the power conversion circuit further comprises:
an element that limits current, the current-limiting element connected between the second one of the terminals of the capacitor and the first unidirectional element.
7. The DC power supply circuit of claim 6 , wherein
the current-limiting element is an inductor.
8. The DC power supply circuit of claim 1 , wherein
a length of each cycle of ON and OFF switching of the switching element and an on-duty ratio of the switching element are set based upon a rate at which the voltage across the terminals of the capacitor increases.
9. A direct current (DC) power supply circuit comprising;
a rectifier circuit rectifying alternating current (AC) supplied thereto from an AC power supply; and
a voltage conversion circuit connected across output terminals of the rectifier circuit, converting a voltage from the rectifier circuit, and outputting a converted voltage to a load,
the voltage conversion circuit comprising:
an inductor having terminals, a first one of which is connected to a high-potential one of the output terminals of the rectifier circuit;
a switching element connected between a second one of the terminals of the inductor and a low-potential one of the output terminals of the rectifier circuit;
a capacitor having terminals, a first one of which is connected to the low-potential one of the output terminals of the rectifier circuit and a second one of which is connected to a first terminal of the load; and
a first unidirectional element connected between the second one of the terminals of the inductor and a second terminal of the load, wherein
when an instantaneous value of the voltage from the rectifier circuit is higher than or equal to a voltage across the terminals of the capacitor,
in an ON period of the switching element, current flows along a first current path from the high-potential one of the output terminals of the rectifier circuit, through the inductor and the switching element in the stated order, and into the low-potential one of the output terminals of the rectifier circuit, and
in an OFF period of the switching element, current flows along a second current path from the high-potential one of the output terminals of the rectifier circuit, through the inductor, the first unidirectional element, the load, and the capacitor in the stated order, and into the low-potential one of the output terminals of the rectifier circuit, wherein
the voltage conversion circuit further comprises:
a second unidirectional element connected between the second one of the terminals of the capacitor and the high-potential one of the output terminals of the rectifier circuit, wherein
when the instantaneous value of the voltage from the rectifier circuit is lower than the voltage across the terminals of the capacitor,
in the ON period of the switching element, current flows along a third current path from the second one of the terminals of the capacitor, through the second unidirectional element, the inductor, and the switching element in the stated order, and into the first one of the terminals of the capacitor, and
in the OFF period of the switching element, current flows along a fourth current path from the second one of the terminals of the inductor, through the first unidirectional element, the load, and the second unidirectional element in the stated order, and into the first one of the terminals of the inductor.
10. The DC power supply circuit of claim 9 , wherein
the first unidirectional element conducts current only in one direction from the second one of the terminals of the inductor to the second terminal of the load, and
the second unidirectional element conducts current only in one direction from the second one of the terminals of the capacitor to the high-potential one of the output terminals of the rectifier circuit.
11. The DC power supply circuit of claim 10 , wherein
the first unidirectional element is a diode, an anode of which is connected to the second one of the terminals of the inductor and a cathode of which is connected to the second terminal of the load, and
the second unidirectional element is a diode, an anode of which is connected to the F one of the terminals of the capacitor and a cathode of which is connected to the high-potential one of the output terminals of the rectifier circuit.