FIELD

The present disclosure relates to the field of power converters, and more particularly aims at the field of so-called phase-controlled converters.

BACKGROUND

A phase-controlled power converter typically comprises a primary stage modulating the input power at a relatively high frequency called cut-off frequency, followed by an isolation stage capable of transmitting the power modulated by the primary stage, followed by a secondary stage demodulating the power transmitted by the isolation stage and supplying the output power of the converter. Each of the primary and secondary stages comprises one of a plurality of switches controlled in switched mode, also called cut-off switches. The control of the power transfer between the input and the output of the converter is performed by varying the phase shift between the control of the switch(es) of the primary stage and the control of the switch(es) of the secondary stage, the two stages being controlled at the same frequency. Examples of phase-controlled power converters are particularly described in patent applications FR3061817 and FR3061818 previously filed by the applicant.

Conventionally, a phase-controlled converter comprises a control circuit common to the primary secondary stages, capable of implementing voltage and/or current measurements in each of the primary and secondary stages, of generating control laws for the switches of the primary and secondary stages, and of ensuring the distribution of the control signals to the primary and secondary stages. Due to the isolation between the primary and secondary stages, the common control circuit is relatively complex and expensive. In particular, isolated voltage and/or current measurements and isolated communication components between the primary stage and the secondary stage, for example, optocouplers or RF isolators, generally have to be provided. The links of the primary stage and of the secondary stage to a same common control circuit raise a particular issue when the primary and secondary stages are physically separated from each other, for example, in the case of a wireless power transmission system.

It would be desirable to overcome all part of the disadvantages of known phase-controlled converters.

SUMMARY

For this purpose, an embodiment provides a power converter comprising:a primary stage comprising at least one first cut-off switch;a control circuit capable of applying a first control signal to said at least one first switch;a secondary stage comprising at least one second cut-off switch;a control circuit capable of applying a second control signal to said at least one second switch; anda power transmission stage coupling the primary stage to the secondary stage, the power transmission stage comprising a transformer comprising a primary winding and a secondary winding,wherein the primary stage comprises a series inductance between said at least one first switch and the primary winding of the transformer or wherein the secondary stag comprises a series inductance between said at least one second switch and the secondary winding of the transformer,wherein the control circuit of the secondary stage is electrically isolated from the control circuit of the primary stage, and wherein the control circuit of the secondary stage is configured to, dining a synchronization phase, based on a measurement of a current or of a voltage in the secondary stage, generate a third signal representative of the first control signal applied to said at least one first switch,and wherein the control circuit of the secondary stage is configured to, during the synchronization phase, control said at least one second switch to couple to each other the two ends of the secondary winding of the transformer.

According to an embodiment, the control circuit of the secondary stage is further configured to, at the end of the synchronization phase, synchronize the second control signal of the second switch with respect to the third signal, to synchronize the control of the second switch on that of the first switch.

According to an embodiment, the control circuit of the secondary stage is configured to periodically repeat the synchronization phase.

According to an embodiment, the control circuit of the secondary stage is further configured to, during an operating range selection phase, determine, based on a measurement of a current and/or of a voltage in the secondary stage, in which operating range a phase shift φ between the first control signal of the first switch and the second control signal of the second switch is located.

According to an embodiment, the control circuit of the secondary stage is further configured to, during the operating range selection phase, modify the phase of the second control signal of the second switch to place phase shift φ in a desired operating range.

According to an embodiment, the primary stage comprises four first switches forming a first H bridge controlled by the control circuit of the primary stage, and the second stage comprises four second switches forming a second H bridge controlled by the control circuit of the secondary stage.

According to an embodiment, the control circuit of the primary stage is configured to measure an AC input signal of the converter, and accordingly adapt a duty cycle between control signal of the first and second anus of the first H bridge to ensure a sinusoidal absorption of the input current of the converter.

According to an embodiment, the control circuit of the secondary stage is configured to, based on a measurement of a current or of a voltage in the secondary stage, determine the variation of an AC input signal of the converter, and accordingly adapt a duty cycle between control signals of first and second arms of the first H bridge to ensure a sinusoidal absorption of the input current of the converter.

According to an embodiment, the control circuit of the primary stage and the control circuit of the secondary stage are capable of controlling the first switch and the second switch in switched mode at a frequency in the range from 10 kHz to 10 MHz.

wherein the control circuit of the secondary stage is electrically isolated from the control circuit of the primary stage, and wherein the control circuit of the secondary stage is configured to, during an operating range selection phase, determine, based on a measurement of an output current of the secondary stage or of an output power of the secondary stage, in which operating image a phase shift φ between the first signal for controlling said at least one first switch and a signal for controlling said at least one second switch is located.

According to an embodiment, the control circuit of the secondary stage is further capable of, during the operating range selection phase, modify the phase of the second signal for controlling the second switch to place phase shift in a desired operating range.

According to an embodiment, the control circuit of the secondary stage is capable of, during the operating range selection phase:a) determining a direction of transfer of an electric power tween the primary stage and the secondary stage;b) determining the sign of a ratio ΔX/Δφ between a variation ΔX of the electric power transferred between the primary stage and the secondary stage or of an output current of the secondary stage and a corresponding variation Δφ of the phase of the second signal for controlling the second switch; andc) modifying the phase of the second signal for controlling the second switch according to the transfer direction determined at step a) and to the sign of the ratio ΔX/Δφ determined at step b).

According to an embodiment, the control circuit of the secondary stage is configured to, at step c):if the transfer direction determined at step a) is positive and if the sign of the ratio ΔX/Δφ determined at step b) is negative, apply a −π/2 phase shift to the second signal for controlling said at least one second switch;if the transfer direction determined at step a) is positive and if the sign of the ratio ΔX/Δφ determined at step b) is positive, apply no phase shift to the second signal for controlling said at least one second switch;if the transfer direction determined at step a) is negative and if the sign of the ratio ΔX/Δφ determined at step b) is positive, apply a π/2 phase shift to the second signal for controlling said at least one second switch; andif the transfer direction determined at step a) is negative and if the sign of the ratio ΔX/Δφ determined at step b) is negative, apply a π phase shift to the second signal for controlling said at least one second switch.

According to an embodiment, the control circuit of the secondary stage is configured to repeat the operating range selection phase each time the converter is started.

According to an embodiment, the control circuit of the secondary stage is further configured to, during a synchronization phase, based on a measurement of a current or of a voltage in the secondary stage, generate a third signal representative of the first control signal applied to said at least one first switch.

According to an embodiment, the control circuit of the secondary stage is further configured to, during the synchronization phase, adapt the second signal for controlling the second switch according to the third signal, to synchronize the control of the second switch on that of the first switch.

According to an embodiment, the control circuit of the secondary stage is configured to periodically repeat the synchronization phase.

According to an embodiment, the primary stage comprises sour first switches forming a first H bridge controlled by the control circuit of the primary stage, and the second stage comprises four second switches forming a second H bridge controlled by the control circuit of the secondary stage.

According to an embodiment, the isolated power transmission stage comprises a transformer.

