CONTROL CIRCUIT FOR A SWITCH UNIT OF A CLOCKED POWER SUPPLY CIRCUIT, AND RESONANCE CONVERTER

• US 20100135049A1
• Filed: 10/14/2009
• Published: 06/03/2010
• Est. Priority Date: 05/23/2005
• Status: Active Grant

• Current Assignee: Fabio Bisogno, Matthias Radecker, Michael Herfurth
• Original Assignee: Fabio Bisogno, Matthias Radecker, Michael Herfurth
• Inventors: Radecker, Matthias, Herfurth, Michael, Bisogno, Fabio
• Granted Patent: US 7,969,754 B2
• Time in Patent Office: Days
• US Class Current: 363/21.30
• CPC Class Codes: H02M 1/0058 by employing soft switching techniques, i.e. commutation of transistors when applied voltage is zero or when current flow is zero using an auxiliary actively switched resonant commutation circuit connected to an intermediate DC voltage or between two push-pull branches of an inverter bridge H02M7/4811; in resonant inverters H02M7/4815; in inverters operating from a resonant DC source H02M7/4826
• CPC Class Codes: H02M 3/33507 with automatic control of the output voltage or current, e.g. flyback converters H02M3/33561, H02M3/33569 take precedence
• 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 control circuit for a switch unit of a clocked power supply circuit, the switch unit being designed to effect input-side excitation of a resonant transformer arrangement, comprises an input for receiving an auxiliary signal from the resonant transformer arrangement. The auxiliary signal exhibits an essentially fixed phase relation to a load alternating current flowing through a resonant circuit of the transformer arrangement. The control circuit further comprises a phase detector designed to detect reference crossing moments when the auxiliary signal crosses a predefined reference value, a driver controllable to switch the switch unit, and a synchronization means designed to synchronize a turn-on of the switch unit by the driver with regard to a phase position with the auxiliary signal so as to achieve a turn-on of the switch unit within a predetermined time interval around a zero crossing of a voltage present across the switch unit, or of a current flowing through the switch unit. The synchronization means is further designed to receive information about the reference crossing moments from the phase detector, and to provide a turn-on signal to the driver with a fixed phase delay at the reference crossing moments, so as to define turn-on moments at which the driver is to turn on the switch unit. The control circuit further comprises a detector designed to determine an amplitude information which depends on an amplitude or a mean value of the auxiliary signal, and a regulator designed to change an operating frequency in dependence on the amplitude information supplied by the detector, and to determine a period duration between turn-off moments at which the driver is to turn off the switch unit as a reciprocal of the operating frequency. An inventive resonance converter enables independent control of frequency and turn-on moments, or duty cycle, and thus enables a particularly efficient operation of the resonance converter, and a particularly precise regulation.

Claims

1. A resonance converter for providing an output voltage or an output current for a load network based on an energy supplied by an energy source, the resonance converter comprising:

a resonant transformer arrangement having an input for receiving an input-side excitation, an output for providing the output voltage or the output current for the load network, and an auxiliary output for transformationally providing a signal which is essentially proportional to the output voltage provided by the resonant transformer arrangement, or to the output current provided by the resonant transformer arrangement;

a switch unit designed to generate the input-side excitation of the resonant transformer arrangement from the energy of the energy source, the switch unit comprising a switch; and

a control circuit designed to set or to regulate an operating frequency, with which the switch unit is switched, in dependence on a phase shift between a current flowing through the switch or a current flowing from the switch unit to the input of the resonant transformer arrangement, on the one hand, and on the signal present at the auxiliary output, on the other hand.

2. The resonance converter according to claim 1, wherein the auxiliary output is designed to provide an auxiliary signal which is essentially proportional to the output voltage,

which further includes an output current detector for determining a load current information about the output current or a current in the load network,

a logarithmizer for taking the logarithm for determining a logarithmized load current information by forming a logarithm of the load current information,

a phase reference value provider for deriving a phase reference value from the logarithmized load current information by applying a linear function to the logarithmized load current information, and

a regulator,

the regulator being designed to regulate the operating frequency so as to minimize a difference between the phase shift and the phase reference value.

3. The resonance converter according to claim 2, wherein the logarithmizer and the phase reference value provider are designed to provide, with a higher output current or current in the load network, a smaller phase reference value than with a smaller output current or current in the load network.

6. The resonance converter according to claim 1, wherein the auxiliary output is designed to provide an auxiliary signal essentially proportional to the output voltage,

which includes a first reference value comparator designed to detect zero crossing moments of the auxiliary signal,

a second reference value comparator designed to compare the auxiliary signal with a predefined reference value different from zero, and to provide an output signal which indicates whether the auxiliary signal is smaller or larger than the reference value, and

a zero crossing detector designed to detect zero crossing moments at which the current flowing through the switch, or the current flowing from the switch unit to the input of the resonant transformer arrangement, comprises zero crossings, and

wherein the control circuit is designed to determine a phase shift between the zero crossing moments of the auxiliary signal and the zero crossing moments of the current,

to generate a phase reference value as a function of the output signal of the second reference value comparator, and

to regulate the operating frequency based on the phase shift and the phase reference value.

7. The resonance converter according to claim 6, wherein the control circuit is designed to specify the direction of a change in the operating frequency as a function of the phase reference value, and to specify an amount of a change in the operating frequency as a function of the phase shift.

8. The resonance converter according to claim 1, further comprising a pump circuit connected in series to the input of the resonant transformer arrangement, wherein the control circuit is designed to sample a voltage curve across the pump circuit, to determine information about a source voltage, provided by the energy source, or a resonant frequency of the switch unit, and to determine, on the basis thereof, a correction variable and superimpose it onto the phase shift in a linear manner.

9. The resonance converter according to claim 1, which further comprises a pump circuit connected in series to the input of the resonant transformer arrangement,

which includes a driver which is controllable to switch the control unit,

and wherein the control circuit is further designed to generate a reverse detection signal when a current flowing through a switch of the switch unit falls below a predefined current value or flows in a reverse direction,

to provide a turn-on signal to the driver to define turn-on moments at which the driver is to turn on the switch unit,

to compare the voltage present across the pump circuit with a predefined pump voltage reference value,

to generate a pump voltage reference comparison signal indicating whether the voltage present across the pump circuit is larger or smaller than the pump voltage reference value,

to delay the pump voltage reference comparison signal to obtain a delayed pump voltage reference comparison signal, and

to generate the turn-on signal by an OR operation of the reverse detection signal and of the delayed pump voltage reference comparison signal.

10. The resonance converter according to claim 9, wherein the control circuit is designed to delay the pump voltage reference comparison signal by a phase delay ranging between 80°

and 100°

, based on an operating frequency.

12. The resonance converter according to claim 1, wherein a voltage rectified at the output load and proportional to the output voltage, or a rectified current proportional to the output current is used via a direct current feedback, such as a galvanically separating optocoupler, to provide a reference value, and thus to regulate the output voltage or the output current, present at the output-side resistive load, to have a constant value.

4. The resonance converter according to claimed 1, wherein the auxiliary output is designed to provide an auxiliary signal which is essentially proportional to the output voltage,

which includes a reference value comparator designed to compare the auxiliary signal with a predefined reference value and to detect reference crossing moments at which the auxiliary signal crosses the predefined reference value, and

a zero crossing detector designed to detect zero crossing moments at which the current flowing through the switch, or the current flowing from the switch unit to the input of the resonant transformer arrangement, comprises zero crossings,

and wherein the control circuit is designed to determine a phase shift between the reference crossing moments and the zero crossing moments to detect whether at least one reference crossing moment is present within a predefined time interval, so as to set a phase reference as a function of whether at least one reference crossing moment is present in the predefined time interval, and

to regulate the operating frequency as a function of a difference between the phase shift and the phase reference.

5. The resonance converter according to claim 4, wherein the control circuit is designed to regulate the operating frequency so as to minimize the difference between the phase shift and the phase reference.

11. A resonance converter for providing an output voltage or an output current for a load network based on an energy provided by an energy source, the resonance converter comprising:

a resonant transformer arrangement having an input for receiving an input-side excitation, an output for providing the output voltage or the output current, and an auxiliary output for transformationally providing an auxiliary signal, the amplitude of which is essentially proportional to the output voltage provided by the resonant transformer arrangement, the amplitude of which is essentially proportional to the output current provided by the resonant transformer arrangement, or the amplitude of which is essentially proportional to a load alternating current flowing through a resonant circuit of the resonant transformer arrangement;

a switch unit designed to generate the input-side excitation of the resonant transformer arrangement from the energy of the energy source; and

a regulator circuit, the regulator circuit comprising a comparator adapted to receive the auxiliary signal, to compare it with a predefined reference value and to provide comparison information indicating whether the auxiliary signal is larger or smaller than the reference value,

the regulator circuit further including a switching detector designed to detect whether the comparison information changes its state within a predefined time interval, and

the regulator circuit being designed to change an operating frequency, the period duration of which determines time intervals between turn-on moments or turn-off moments of the switch unit, from a resonant frequency of the resonant transformer arrangement when the detector detects that the comparison information has changed its state within the predefined time interval, and to change the operating frequency toward the resonant frequency when the detector detects that the comparison information has not changed its state within the predefined time interval.

13. The resonance converter according to claim 11, wherein a voltage rectified at the output load and proportional to the output voltage, or a rectified current proportional to the output current is used via a direct current feedback, such as a galvanically separating optocoupler, to provide a reference value, and thus to regulate the output voltage or the output current, present at the output-side resistive load, to have a constant value.

14. A control circuit for a switch unit of a clocked power supply circuit, the switch unit being designed to effect input-side excitation of a resonant transformer arrangement, the control circuit comprising:

an input for receiving an auxiliary signal from the resonant transformer arrangement, the auxiliary signal exhibiting an essentially fixed phase relation to a load alternating current flowing through a resonant circuit of the transformer arrangement;

a phase detector designed to detect reference crossing moments when the auxiliary signal crosses a predefined reference value;

a driver controllable to switch the switch unit;

a synchronizer designed to synchronize a turn-on of the switch unit by the driver with regard to a phase position with the auxiliary signal so as to achieve a turn-on of the switch unit within a predetermined time interval around a zero crossing of a voltage present across the switch unit, or of a current flowing through the switch unit,

the synchronizer being designed to receive information about the reference crossing moments from the phase detector, and to provide a turn-on signal to the driver with a fixed phase delay at the reference crossing moments, so as to define turn-on moments at which the driver is to turn on the switch unit;

a detector designed to determine an amplitude information which depends on an amplitude or a mean value of the auxiliary signal; and

a regulator designed to change an operating frequency in dependence on the amplitude information supplied by the detector, and to determine a period duration between turn-off moments at which the driver is to turn off the switch unit as a reciprocal of the operating frequency;

wherein a voltage rectified at the output load and proportional to the output voltage, or a rectified current proportional to the output current is used via a direct current feedback, such as a galvanically separating optocoupler, to provide a reference value, and thus to regulate the output voltage or the output current, present at the output-side resistive load, to have a constant value.