Control device for a resonant converter

• US 6,822,881 B2
• Filed: 05/09/2002
• Issued: 11/23/2004
• Est. Priority Date: 05/09/2001
• Status: Expired due to Term

• Current Assignee: Philips Lighting BV (Koninklijke Philips N.V.)
• Original Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Inventors: Elferich, Reinhold
• Primary Examiner(s): NGUYEN, MATTHEW VAN
• Application Number:
  US10/142,586
• Publication Number:
  US 20020186026A1
• Time in Patent Office: 929 Days
• Field of Search: 363/15-17, 363/21.01, 363/21.02, 363/97, 363/98, 363/131, 363/132, 363/56.01, 363/56.02, 363/20.02
• US Class Current: 363/21.02
• CPC Class Codes: H02M 3/33561 having more than one ouput with independent control
• 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 converter and a control method for a resonant converter are proposed. The resonant converter comprises a resonant circuit with a transformer, which circuit is supplied with power by an AC inverter with a switched AC voltage, preferably a pulse-width modulated voltage. The circuit comprises a plurality of secondary units each consisting of a secondary winding of the transformer and at least one rectifier element (diode). The secondary units are subdivided into secondary units of the first and second type, secondary units of the first type and secondary units of the second type having opposite orientations. Secondary units of opposite types preferably have either with the same wiring a different winding orientation or with opposite wiring the same winding orientation. The resonant converter produces at least two output voltages, a first output voltage of which depending on the voltage on the first secondary unit (“direct output”) and a second output voltage depending only on the voltage of the second secondary unit or on the voltage on the first and the second secondary unit (“stack output”). In addition, the converter comprises a control device for separately controlling the two output voltages caused by the driving of the inverter. In various embodiments either frequency and duty cycle or the pulse durations of the pulse-width modulated voltage to be generated are predefined for the inverters, so that with these two parameters as a setting signal the two output voltages can be controlled independently of each other. Different controllers are proposed here for different output configurations.

Claims

1. A resonant converter comprising

an inverter that generates an AC voltage,

a resonant circuit supplied with the AC voltage and comprising

at least a capacitor and

at least a transformer, and

at least two secondary units, each formed by

at least one respective secondary winding of the transformer and

at least one respective ractifier element,

wherein:

a first secondary unit and a second secondary unit of the at least two secondary units have opposite orientations,

at least two output voltages are supplied

a first output voltage of which being supplied by the first secondary unit and

a second output voltage either by the second secondary unit or by the first and the second secondary unit, and

a control system is provided for controlling the first and second output voltage by driving the inverter.

2. A resonant converter as claimed in claim 1, wherein

the secondary units are of two types,

the secondary units of a first type having opposite orientation to the secondary units of a second type.

3. A resonant converter as claimed in claim 2, wherein

two groups of output voltages are supplied, each group comprising one or more output voltages,

a first group of the output voltages being fed by one or more secondary units of the first type, and

a second group of the output voltages being fed by either

one or more secondary units of the second type or

secondary units of the first and of the second type.

4. A resonant converter as claimed in claim 3, wherein

the control system controls an output voltage of the first and an output voltage of the second group to a set value.

5. A resonant converter as claimed in claim 1, wherein

the inverter is driven by a pulse signal so that a pulse-width modulated voltage is supplied for feeding the resonant circuit.

6. A resonant converter as claimed in claim 5, wherein

the control system is arranged so that it produces two set values which define a characteristic waveform of the pulse-width modulated voltage.

7. A resonant converter as claimed in claim 6, wherein

the two set values are switch-on times for a first and a second voltage pulse, and

the first voltage pulse is positive, and

the second voltage pulse is zero or negative.

8. A resonant converter as claimed in claim 6, wherein

the two set values are a switching frequency and a duty cycle.

9. A resonant converter as claimed in claim 8, wherein:

the control system is arranged so that it determines a first and a second control error size for the first and second output voltage to be controlled, and

calculates

a cumulative sum which depends on a sum of the first and second control error sizes, and

a cumulative difference which depends on a difference between the first and second control error sizes,

the cumulative sum is applied to a controller for the switching frequency, and

the cumulative difference is applied to a controller for the duty cycle of the pulse-width modulated voltage.

10. A resonant converter as claimed in claim 8, wherein:

the control system is arranged so that it determines a first and a second control error size for the first and second output voltage,

the first control error size is applied to a controller for the duty cycle, and

the second control error size is applied to a controller for the frequency of the pulse-width modulated voltage.

11. A resonant converter as claimed in claim 7, wherein

the control system is arranged so that it determines a first and a second control error size for the first and second output voltages,

a duration of a first voltage pulse of the pulse-width modulated voltage being determined from the first control error size, and

a duration of a second voltage pulse of the pulse-width modulated voltage being determined from the second control error size.

12. A resonant converter as claimed in claim 7, wherein:

the control system is realized as an analog circuit comprising

at least two error units that form error size signals, and

at least one multivibrator that generates a pulse signal to control the inverter, and

a pulse duration of the pulses of the pulse-width modulated voltage generated by the inverter is dependent upon the error size signals.

14. A switched-mode power supply comprising

a power supply input circuit for connection to the electricity mains and for delivering an indirect DC voltage, and

a resonant converter as claimed in claim 1 which is supplied with power by the indirect DC voltage.

16. A resonant converter as claimed in claim 11, wherein:

the control system is realized as an analog circuit comprising

at least two error units that forms error size signals, and

at least one multivibrator that generates a pulse signal to control the inverter, and

a pulse duration of the pulses of the pulse-width modulated voltage generated by the inverter is dependent upon the error size signals.

17. A resonant converter as claimed in claim 4, wherein

the inverter is driven by a pulse signal so that a pulse-width modulated voltage is supplied for feeding the resonant circuit.

18. A resonant converter as claimed in claim 17, wherein

the control system is arranged so that it controls a switching frequency and a duty cycle of the AC voltage.

19. A resonant converter as claimed in claim 18, wherein:

the control system is arranged so that it

determines a first and a second control error size for the first and second output voltage to be controlled, and

calculates

a cumulative sum which depends on a sum of the first and second control error sizes, and

a cumulative difference which depends on a difference between the first and second control error sizes,

the cumulative sum is applied to a controller for the switching frequency, and

the cumulative difference is applied to a controller for the duty cycle of the pulse-width modulated voltage.

20. A resonant converter as claimed in claim 17, wherein

the control system is arranged so that it determines a first and a second control error size for the first and second output voltages,

a duration of a first voltage pulse of the pulse-width modulated voltage being determined from the first control error size, and

a duration of a second voltage pulse of the pulse-width modulated voltage being determined from the second control error size.

13. A control method for a resonant converter comprising:

generating an AC voltage;

driving a first secondary unit of the resonant converter by a first phase of the AC voltage to provide a first output voltage;

driving a second secondary unit of the resonant converter by a second phase of the AC voltage to provide a second output voltage;

comparing the first output voltage to a first reference voltage to produce a first error signal;

comparing the second output voltage to a second reference voltage to produce a second error signal; and

controlling the AC voltage based on the first and second error signals.

15. The method of claim 13, wherein

the first error signal controls the first phase of the AC voltage, and

the second error signal controls the second phase of the AC voltage.