Resonant Dc/Dc Converter With Zero Current Switching

• US 20080198634A1
• Filed: 04/13/2006
• Published: 08/21/2008
• Est. Priority Date: 04/26/2005
• Status: Active Grant

• Current Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Original Assignee: Koninklijke Philips N.V.
• Inventors: Loef, Christoph, Scheel, Thomas, Luerkens, Peter
• Granted Patent: US 7,948,774 B2
• Time in Patent Office: Days
• US Class Current: 363/21.02
• CPC Class Codes: H02M 3/01 Resonant DC/DC converters
• CPC Class Codes: H02M 3/158 including plural semiconductor devices as final control devices for a single load
• CPC Class Codes: H02M 3/33573 Full-bridge at primary side of an isolation transformer
• CPC Class Codes: H02M 3/3376 with automatic control of output voltage or current
• CPC Class Codes: Y02B 70/10 Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

Abstract

A resonant DC/DC converter for supplying an output power comprises a switching device (18) for supplying a switched voltage (UWR) to a resonant circuit (20) having a transformer (T). The switched voltage (UWR) is derived from an intermediate circuit voltage (Uz) having a fixed pulse width and frequency so that the zero crossings of the resonant current (Ires) generated in the resonant current are defined. The switching configuration of an inverter circuit (18) is selected by a control device (31) to either increase, decrease or maintain at a substantially constant level the resonant current according to the polarity of the switched voltage, so as to control the output power as required.

Claims

1. A resonant power converter for supply an output power, comprising a switching device for converting an intermediate circuit voltage into a switched voltage, a resonant circuit realised by means of a transformer for supplying an output voltage and being fed by the switched voltage, so as to generate a resonant current, the power converter further comprising an inverter circuit comprising a plurality of switches and respective rectifying components for defining the current flow path around said inverter circuit according to the switch configuration thereof, and a control device for selecting one of a plurality of switch configurations of said inverter circuit dependent on a required output power of said converter;

wherein the frequency and pulse width of said intermediate circuit voltage are adjusted such that switching events of said inverter circuit occur at or adjacent to that the zero crossings of said resonant current.

2. A converter according to claim 1, wherein said plurality of switching configurations include first and second switching configurations for increasing or decreasing the resonant current by controlling the phase relationship of the switched voltage with respect to the resonant current.

3. A converter according to claim 2, arranged and configured such that the resonant current is increased if, by the selection of a first switching configuration, switched voltage is in-phase with the resonant current, and decreased if, by the selection of a second switch configuration, the switched voltage is in anti-phase with the resonant current.

4. A converter according to claim 2, wherein said plurality of switch configurations further includes a third switch configuration for maintaining the resonant current at a substantially constant level.

5. A converter according to claim 4, wherein in said third switching configuration, the switch voltage is substantially zero.

6. A converter according to claim 1, wherein said resonant circuit includes a series resonant capacitor, and values representative of a voltage across said series resonant capacitor and said output voltage are input to said control device.

7. A converter according to claim 6, comprising a multi-level controller including a plurality of outputs corresponding to respective said plurality of switch configurations.

8. A converter according to claim 7, wherein said plurality of outputs comprising respective next output voltage step values input to a decision block.

9. A converter according to claim 8, wherein said decision block is arranged and configured to compare each of said step values to a reference value representative of a desired next output voltage to determine which is the closest, and to output a control value to cause an appropriate switch configuration to be selected.

10. A converter according to claim 1, wherein said inverter and said rectifying components comprise diodes.

11. A converter according to claim 1, comprising a plurality of inverter circuits working on a single transformer, wherein the number of inverter circuits determines the number of switch configurations from which said control device can select.

12. A method of controlling a resonant power converter according to claim 1, the method comprising the steps of receiving data representative of a required output power of said converter, and selecting one of a plurality of switch configurations of said inverter circuit dependent on said required output power of said converter.

13. A control device for a resonant power converter according to claim 1, the control device comprising an input for receiving data representative of a required output power of said converter, means for selecting one of a plurality of switch configurations of said inverter circuit dependent on said required output power of said converter, and an output for outputting a signal for causing respective switches of said inverter circuit to be configured according to said selected switching configuration.