Switching power supply unit

• US 8,339,808 B2
• Filed: 06/14/2010
• Issued: 12/25/2012
• Est. Priority Date: 06/19/2009
• Status: Expired due to Fees

• Current Assignee: TDK Corporation
• Original Assignee: TDK Corporation
• Inventors: Nakahori, Wataru
• Primary Examiner(s): Zhang, Jue
• Application Number:
  US12/801,541
• Publication Number:
  US 20100321960A1
• Time in Patent Office: 925 Days
• Field of Search: 323/16, 323/17, 323/47, 323/56.02, 323/126, 323/132, 363/16, 363/17, 363/47, 363/56.02, 363/126, 363/132
• US Class Current: 363/17
• CPC Class Codes: H01F 2027/2819 Planar transformers with printed windings, e.g. surrounded by two cores and to be mounted on printed circuit
• CPC Class Codes: H01F 27/2804 Printed windings
• CPC Class Codes: H01F 27/2847 Sheets; Strips H01F27/2866 takes precedence
• CPC Class Codes: H02M 1/0064 Magnetic structures combining different functions, e.g. storage, filtering or transformation
• CPC Class Codes: H02M 1/40 Means for preventing magnetic saturation
• CPC Class Codes: H02M 3/01 Resonant DC/DC converters
• CPC Class Codes: H02M 3/33573 Full-bridge at primary side of an isolation transformer

Abstract

The switching power supply unit includes: a transformer having a primary winding and two secondary windings; and a rectifying-smoothing circuit having two rectifying elements, three choke coils and a capacitive element. A first rectifying element is between a junction of ends of the first secondary winding and the second choke coil, and one end of the capacitive element. A second rectifying element is between a junction of ends of the second secondary winding and the third choke coil, and the one end of the capacitive element. The other end of the first secondary winding and the other end of second secondary winding are connected to the one end of the first choke coil. The other end of the first choke coil, the other end of the second choke coil, and the other end of the third choke coil are connected to the other end of the capacitive element.

Claims

1. A switching power supply unit converting a DC input voltage inputted from an input terminal pair into a DC output voltage, and outputting the generated DC output voltage from an output terminal pair, the switching power supply unit comprising:

a transformer including;

a primary winding arranged on the input terminal pair side and a first and a second secondary windings arranged on the output terminal pair side, the first and a second secondary windings being connected in series to each other;

a magnetic core including two base-plates facing each other and four legs provided between the two base-plates to couple the two base-plates together, the four legs including a first pair of legs on a first diagonal line and a second pair of legs on a second diagonal line, the first and second diagonal lines intersecting each other in a plane along facing surfaces of the two base-plates;

a first conductive member having through-holes allowing the four respective legs to pass therethrough, and configuring the primary winding which is wound around the legs; and

a second conductive member having through-holes allowing the four respective legs to pass therethrough, and configuring the first and second secondary windings which are wound around the legs;

an inverter circuit arranged between the input terminal pair and the primary winding, and including switching elements; and

a rectifying-smoothing circuit arranged between the output terminal pair and the first and second secondary windings, and including first and second rectifying elements, first to third choke coils, and a capacitive element arranged between the output terminal pair;

wherein

the first rectifying element is arranged between a first junction and one end of the capacitive element, the first junction being defined as a junction of one end of the first secondary winding and one end of the second choke coil;

the second rectifying element is arranged between a second junction and the one end of the capacitive element, the second junction being defined as a junction of one end of the second secondary winding and one end of the third choke coil;

a third junction is connected to the one end of the first choke coil, the third junction being defined as a junction of the other end of the first secondary winding and the other end of second secondary winding; and

a fourth junction is connected to the other end of the capacitive element, the fourth junction being defined as a junction of the other end of the first choke coil, the other end of the second choke coil and the other end of the third choke coil.

2. The switching power supply unit according to claim 1, wherein

an expression L1<

L2=L3 is satisfied, where L1, L2 and L3 represent inductances of the first to third choke coils, respectively.

3. The switching power supply unit according to claim 1, wherein

a cathode of the first rectifying element is connected to the first junction while an anode thereof is connected to the one end of the capacitive element;

and

a cathode of the second rectifying element is connected to the second junction while an anode thereof is connected to the one end of the capacitive element.

4. The switching power supply unit according to claim 1, wherein

an anode of the first rectifying element is connected to the first junction while a cathode thereof is connected to the one end of the capacitive element;

and

an anode of the second rectifying element is connected to the second junction while a cathode thereof is connected to the one end of the capacitive element.

5. The switching power supply unit according to claim 1, wherein the inverter circuit is a switching circuit of full bridge type including four switching elements.

6. The switching power supply unit according to claim 1, wherein

the primary winding in the transformer is wound around so that:

closed magnetic paths are formed inside the magnetic core from the four legs to the two base-plates due to currents which flow through the primary winding;

a first couple of magnetic fluxes respectively generated inside the first couple of legs are both directed in a first direction; and

a second couple of magnetic fluxes respectively generated inside the second couple of legs are both directed in a second direction which is opposite to the first direction.

7. The switching power supply unit according to claim 1, wherein

the primary winding in the transformer is wound around so that:

closed magnetic paths are formed inside the magnetic core from the four legs to the two base-plates due to currents which flow through the primary winding, the four closed magnetic paths each passing through both adjacent two of the four legs and the two base-plates and then returning.

8. The switching power supply unit according to claim 1, wherein

the transformer includes

a third conductive member having through-holes allowing the four respective legs to pass therethrough, and configuring the second secondary winding which is wound around the legs.

9. The switching power supply unit according to claim 8, wherein

the primary winding in the transformer is wound around so that:

closed magnetic paths are formed inside the magnetic core from the four legs to the two base-plates due to currents which flow through the primary winding, the four closed magnetic paths each passing through both adjacent two of the four legs and the two base-plates and then returning.

13. The switching power supply unit according to claim 8, wherein the primary winding in the transformer is wound around so that:

closed magnetic paths are formed inside the magnetic core from the four legs to the two base-plates due to currents which flow through the primary winding;

a first couple of magnetic fluxes respectively generated inside the first couple of legs are both directed in a first direction; and

a second couple of magnetic fluxes respectively generated inside the second couple of legs are both directed in a second direction which is opposite to the first direction.

10. A switching power supply unit converting a DC input voltage inputted from an input terminal pair into a DC output voltage, and outputting the generated DC output voltage from an output terminal pair, the switching power supply unit comprising:

a transformer including;

a primary winding arranged on the input terminal pair side and first to fourth secondary windings arranged on the output terminal pair side, the first to fourth secondary windings being connected in series to each other;

a magnetic core including two base plates facing each other and four legs provided between the two base-plates to couple the two base-plates together, the four legs including a first pair of legs on a first diagonal line and a second pair of legs on a second diagonal line, the first and second diagonal lines intersecting each other in a plane along facing surfaces of the two base-plates;

a first conductive member having through-holes allowing the four respective legs to pass therethrough, and configuring the primary winding which is wound around the legs;

a second conductive member having through-holes allowing the four respective legs to pass therethrough, and configuring the first and second secondary windings which are wound around the legs; and

a third conductive member having through-holes allowing the four respective legs to pass therethrough, and configuring the third and fourth secondary windings which are wound around the legs;

an inverter circuit arranged between the input terminal pair and the primary winding, and including switching elements; and

a first rectifying-smoothing circuit arranged between the output terminal pair and the first and second secondary windings, and including first and second rectifying elements, first to third choke coils, and a first capacitive element arranged between the output terminal pair; and

a second rectifying-smoothing circuit arranged between the output terminal pair and the third and fourth secondary windings in parallel with the first rectifying-smoothing circuit, and including third and fourth rectifying elements, fourth to sixth choke coils, and a second capacitive element arranged between the output terminal pair;

wherein

the first rectifying element is arranged between a first junction and one end of the capacitive element, the first junction being defined as a junction of one end of the first secondary winding and one end of the second choke coil,

the second rectifying element is arranged between a second junction and the one end of the capacitive element, the second junction being defined as a junction of one end of the second secondary winding and one end of the third choke coil,

a third junction is connected to the one end of the first choke coil, the third junction being defined as a junction of the other end of the first secondary winding and the other end of second secondary winding,

a fourth junction is connected to the other end of the capacitive element, the fourth junction being defined as a junction of the other end of the first choke coil, the other end of the second choke coil and the other end of the third choke coil,

the third rectifying element is arranged between a fifth junction and one end of the second capacitive element, the fifth junction being defined as a junction of one end of the third secondary winding and one end of the fifth choke coil,

the fourth rectifying element is arranged between a sixth junction and the one end of the second capacitive element, the sixth junction being defined as a junction of one end of the fourth secondary winding and one end of the sixth choke coil,

a seventh junction is connected to the one end of the fourth choke coil, the seventh junction being defined as a junction of the other end of the third secondary winding and the other end of fourth secondary winding, and

an eighth junction is connected to the other end of the first capacitive element, the eighth junction being defined as a junction of the other end of the fourth choke coil, the other end of the fifth choke coil and the other end of the sixth choke coil.

11. The switching power supply unit according to claim 10, wherein

the primary winding in the transformer is wound around so that:

closed magnetic paths are formed inside the magnetic core from the four legs to the two base-plates due to currents which flow through the primary winding;

a first couple of magnetic fluxes respectively generated inside the first couple of legs are both directed in a first direction; and

a second couple of magnetic fluxes respectively generated inside the second couple of legs are both directed in a second direction which is opposite to the first direction.

12. The switching power supply unit according to claim 10,

wherein

the primary winding in the transformer is wound around so that:

closed magnetic paths are formed inside the magnetic core from the four legs to the two base-plates due to currents which flow through the primary winding, the four closed magnetic paths each passing through both adjacent two of the four legs and the two base-plates and then returning.