Control device for a resonant converter

• US 20020186026A1
• Filed: 05/09/2002
• Published: 12/12/2002
• Est. Priority Date: 05/09/2001
• Status: Active Grant

• Current Assignee: Philips Lighting BV (Koninklijke Philips N.V.)
• Original Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Inventors: Elferich, Reinhold
• Granted Patent: US 6,822,881 B2
• Time in Patent Office: Days
• US Class Current: 324/652
• 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 (12) for generating an AC voltage,

and a resonant circuit (14) supplied with the AC voltage and comprising at least a capacitor (C) and at least a transformer (16),

at least two secondary units (20a, 20b) being provided each formed by at least one respective secondary winding (18a, 18b) of the transformer (16) and at least one respective rectifier element (Da, Db),

of which a first secondary unit (20a) and a second secondary unit (20b) have opposite orientations,

and in which at least two output voltages are supplied a first output voltage (Va) of which being supplied by the first secondary unit (20a) and a second output voltage (Vb, Vab) either by the second secondary unit (20b) or by the first and the second secondary unit (20a, 20b),

in which, in addition, a control system (22) is provided for controlling the first and second output voltage (Va, Vb;

Vab) by driving the inverter (12).

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

two types of secondary units (20a, 20b) are provided,

the secondary units of a first type (20a) having opposite orientation to the secondary units of a second type (20b).

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

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

a first group of which output voltages being fed by one or more secondary units of the first type (20a),

and a second group of output voltages being fed by either one or more secondary units of the second type (20b) or both by secondary units of the first and of the second type (20a, 20b).

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

the control system (22) is provided for controlling 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 one of the preceding claims, in which

the inverter (12) is driven by a pulse signal so that a pulse-width modulated voltage is supplied for feeding the resonant circuit (14).

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

the control system (22) is arranged so that it produces two set values (f,δ

;

tsH, tsL) which predefine the waveform of the pulse-width modulated voltage.

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

the two set values are the switch-on times (tsH, tsL) for a first and a second voltage pulse while the first voltage pulse is positive,

and the second voltage pulse is zero or negative.

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

the two set values are the switching frequency (f) and the duty cycle (δ

).

9. A resonant converter as claimed in claim 8, in which

the control system (22, 60, 70) is arranged so that it determines a first and a second control error size (Δ

a, Δ

b) for the first and second output voltage to be controlled (Va, Vb;

Va, Vab),

and calculates herefrom a cumulative sum which depends on the sum of the control error sizes (Δ

a, Δ

b),

and a cumulative difference which depends on the difference of the control error sizes (Δ

a, Δ

b),

while the cumulative sum is applied to a controller (62) for the frequency (f) and the cumulative difference is applied to a controller (64) for the duty cycle (δ

) of the pulse-width modulated voltage.

10. A resonant converter as claimed in claim 8, in which

the control system (22, 70) is arranged so that it determines a first and a second control error size (Δ

a, Δ

b) for the first and second output voltage (Va, Vb;

Va, Vab) to be controlled,

in which the first control error size (Δ

a) is applied to a controller (74) for the duty cycle (δ

),

and the second control error size (Δ

b) is applied to a controller (72) for the frequency (f) of the pulse-width modulated voltage.

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

the control system (22, 80) is arranged so that it determines a first and a second control error size for the first and second output voltage (Va, Vb) to be controlled

a predefined value for the duration (tsH) of the first voltage pulse of the pulse-width modulated voltage being determined from the first control error size,

and a predefined value for the duration (tsL) of the second voltage pulse of the pulse-width modulated voltage being determined from the second control error magnitude.

12. A resonant converter as claimed in one of the claims 7 or 11, in which

the control system is realized as an analog circuit (90) comprising

at least two error units (96) for forming error size signals (i1a, i1b),

and at least one multivibrator (100) for generating a pulse signal to control the inverter (12),

while the pulse duration of the pulses of the pulse-width modulated voltage generated by the inverter are predefined in dependence on 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 one of the claims 1-12 which is supplied with power by the indirect DC voltage.

13. A control method for a resonant converter

in which the converter (10, 30, 40) comprises at least one inverter (12) for generating an AC voltage,

and a resonant circuit (14) comprising at least one capacitance (C) and at least one transformer (16), which circuit is fed by the AC voltage,

and in which at least two secondary units (20a, 20b) are provided each formed by at least one secondary winding (18a, 18b) of the transformer and at least one rectifier element (Da, Db),

of which secondary units (20a, 20b) a first secondary unit (20a) and a second secondary unit (20b) have opposite orientations,

and at least two output voltages (Va, Vb;

Va, Vab) are produced of which a first output voltage (Va) is supplied by the first secondary unit (20a) and a second output voltage (Vb, Vab) is supplied either by the second secondary unit (20b) or by the first and the second secondary unit (20a, 20b),

the driving of the inverter (12) is predefined by controlling the first and second output voltage (Va, Vb;

Va, Vab) to a nominal value (VAref, VBref;

VAref, VABref).