TWI586092B - Single-stage ac-to-dc converter - Google Patents

Description

Single stage AC to DC converter

The present invention relates to power conversion techniques, and more particularly to a single stage AC to DC converter.

The AC to DC converter can use a single-stage architecture or a multi-stage architecture to convert an AC input voltage into a DC output voltage. Single-stage AC to DC converters have higher conversion efficiency, simpler control logic, fewer components, and lower cost than multi-level AC to DC converters. For a single-stage AC to DC converter, how to achieve a wide range of input voltages at the same time and a low chopping of the output voltage is an important issue.

Accordingly, it is an object of the present invention to provide a single stage AC to DC converter that achieves a wide range of input voltages and a low chopping of the output voltage.

Thus, the single-stage AC to DC converter of the present invention includes a bus capacitor, a power factor correction module, a resonant converter module, and a control module. The power factor correction module is coupled to the bus capacitor, Suitable for receiving an AC input voltage, further receiving a first control signal and a second control signal, and generating a voltage across the bus according to the input voltage, the first control signal and the second control signal The DC bus voltage and an intermediate voltage that switches between the bus voltage and zero. The resonant converter module is coupled to the power factor correction module to receive the intermediate voltage, and generates a DC output voltage according to the intermediate voltage. The control module is coupled to the bus capacitor to receive the bus voltage, and generates the first control signal and the second control signal to the power factor correction module according to the bus voltage. Each of the first control signal and the second control signal switches between an active state and an inactive state, and a ratio of its operation is associated with the bus voltage.

The effect of the present invention is that the control module adjusts the working ratio of each of the first control signal and the second control signal according to the bus voltage, and the input voltage can have a wider range; The bus capacitor acts as a relay for power conversion, which can have low chopping.

1‧‧‧voltage source

2‧‧‧load

3‧‧‧Bus Capacitor

4‧‧‧Power Factor Correction Module

41‧‧‧Rectifier circuit

42‧‧‧First switch

421‧‧‧ Essential Dipole

422‧‧‧Parasitic capacitance

43‧‧‧Second switch

431‧‧‧ Essential Diode

432‧‧‧Parasitic capacitance

44‧‧‧Boost Inductance

45‧‧‧third switch

5‧‧‧Resonance conversion module

51‧‧‧Transformers

511‧‧‧First winding

512‧‧‧second winding

531‧‧‧fourth switch

532‧‧‧ output capacitor

54‧‧‧Resonant inductance

6‧‧‧Control module

iD2‧‧‧current flowing through the fourth switch

iLb‧‧‧current flowing through the boost inductor

iLm‧‧‧current flowing through the magnetizing inductor

iLr‧‧‧current flowing through the leakage inductance

t‧‧‧Time

T0-t6‧‧‧

Length of the Td‧‧‧ dead zone

Ta1‧‧‧ When the first control signal is valid Length of the segment

When the Ta2‧‧‧ second control signal is valid Length of the segment

Length of Ts‧‧‧ switching cycle

Vbus‧‧‧ bus voltage

513‧‧‧Magnetic inductance

514‧‧‧Leakage inductance

52‧‧‧Resonant capacitor

53‧‧‧Rectifier filter circuit

Vgs1‧‧‧ first control signal

Vgs2‧‧‧ second control signal

Vin‧‧‧Input voltage

Vout‧‧‧ output voltage

Other features and advantages of the present invention will be apparent from the embodiments of the present invention, wherein: FIG. 1 is a circuit block diagram illustrating an embodiment of a single-stage AC to DC converter of the present invention; a timing diagram illustrating a first control signal and a second control signal of the embodiment; 3 is a timing chart illustrating the operation of the embodiment; FIGS. 4 to 9 are equivalent circuit diagrams respectively illustrating the case where the embodiment operates in the first mode to the sixth mode; and FIG. 10 is a circuit block diagram illustrating A variation of the embodiment.

Referring to FIG. 1, an embodiment of the single-stage AC to DC converter of the present invention is adapted to receive an AC input voltage Vin from a voltage source 1, convert the input voltage Vin into a DC output voltage Vout, and apply the output voltage. Vout is output to a load of 2. The single-stage AC to DC converter of this embodiment includes a bus capacitor 3, a power factor correction module 4, a resonant converter module 5, and a control module 6.

The bus capacitor 3 has a first end and a second end.

The power factor correction module 4 is coupled to the bus capacitor 3, and is adapted to be coupled to the voltage source 1 to receive the input voltage Vin, and further receives a first control signal Vgs1 and a second control signal Vgs2, and according to the input voltage Vin, A control signal Vgs1 and a second control signal Vgs2 generate a bus voltage Vbus across the bus capacitor 3 and being DC, and an intermediate voltage switching between the bus voltages Vbus and zero.

In this embodiment, the bus voltage Vbus is greater than the amplitude of the input voltage Vin, and the power factor correction module 4 includes a rectifier circuit 41, a first switch 42, a second switch 43, a boost inductor 44, and a third Switch 45. The rectifier circuit 41 has a first input terminal adapted to be coupled to the voltage source 1 to receive the input voltage Vin and a first Two inputs. The rectifier circuit 41 also has a first output and a second output coupled to the second end of the bus capacitor 3. The first switch 42 has a first end coupled to the first end of the bus capacitor 3, a second end, and a control terminal receiving the first control signal Vgs1. The second switch 43 has a first end coupled to the second end of the first switch 42, a second end coupled to the second output of the rectifier circuit 41, and a control terminal receiving the second control signal Vgs2. The voltage across the second switch 43 acts as an intermediate voltage. The boost inductor 44 and the third switch 45 are connected in series between the first output of the rectifier circuit 41 and the second terminal of the first switch 42.

In the present embodiment, the rectifier circuit 41 is a full bridge rectifier circuit including four switches (for example, four diodes). The first switch 42 is an N-type MOS field effect transistor, and the N-type MOSFET has a drain serving as a first end of the first switch 42 and a second end serving as the first switch 42. a source, and a gate serving as a control terminal of the first switch 42. The second switch 43 is an N-type MOS field effect transistor, and the N-type MOSFET has a drain serving as a first end of the second switch 43 and a second end serving as a second switch 43. a source, and a gate serving as a control terminal of the second switch 43. The boost inductor 44 has a first end coupled to the first output of the rectifier circuit 41 and a second end. The third switch 45 is a diode having an anode coupled to the second end of the boost inductor 44 and a cathode coupled to the second end of the first switch 42.

The resonant converter module 5 is coupled to the power factor correction module 4 to receive an intermediate voltage, is adapted to be coupled to the load 2, and is produced according to the intermediate voltage The output voltage Vout is given to the load 2.

In this embodiment, the output voltage Vout is smaller than the bus voltage Vbus, and the resonant converter module 5 includes a transformer 51, a resonant capacitor 52, and a rectifying filter circuit 53. The transformer 51 includes a primary winding 511 and a secondary winding 512, and the number of turns of the primary winding 511 is greater than the number of turns of the secondary winding 512. The resonant capacitor 52 and the primary winding 511 are connected in series between both ends of the second switch 43 to receive an intermediate voltage. Rectifier filter circuit 53 is coupled to secondary winding 512 and is adapted to be coupled to load 2 to provide an output voltage Vout.

In the present embodiment, each of the primary winding 511 and the secondary winding 512 has a first end and a second end, and the first end of the primary winding 511 and the first end of the secondary winding 512 have the same voltage polarity. And the second end of the primary winding 511 is coupled to the second end of the second switch 43. The resonant capacitor 52 is coupled between the first end of the second switch 43 and the first end of the primary winding 511. The rectifying filter circuit 53 includes a fourth switch 531 for rectification and an output capacitor 532 for filtering. The output capacitor 532 is connected in parallel to the load 2, and the fourth switch 531 and the parallel output capacitor 532 are connected in series with the load 2 between the two ends of the secondary winding 512. The output capacitor 532 has a first end and a second end coupled to the first end of the secondary winding 512, and its voltage across the voltage acts as an output voltage Vout. The fourth switch 531 is a diode having an anode coupled to the second end of the secondary winding 512 and a cathode coupled to the first end of the output capacitor 532.

Referring to FIG. 1 and FIG. 2, the control module 6 is coupled to the bus capacitor. 3 and the output capacitor 532 to receive the bus voltage Vbus and the output voltage Vout respectively, and is also coupled to the control end of the first switch 42 and the control end of the second switch 43, and respectively generate the first according to the bus voltage Vbus and the output voltage Vout The first control signal Vgs1 and the second control signal Vgs2 of the switch 42 and the second switch 43. Each of the first control signal Vgs1 and the second control signal Vgs2 is in an active state (eg, a logic high level, and corresponds to a corresponding one of the first switch 42 and the second switch 43) and an inactive state (for example, a logic low level, and corresponding to the corresponding one of the first switch 42 and the second switch 43 is not turned on), and its duty ratio and its switching period are respectively associated with the bus voltage Vbus and the output voltage Vout.

In the present embodiment, the first control signal Vgs1 and the second control signal Vgs2 have the same switching period (the length of which is Ts) and are alternately in an active state. When one of the first control signal Vgs1 and the second control signal Vgs2 is in an active state, the other of the first control signal Vgs1 and the second control signal Vgs2 is in an inactive state. After a predetermined dead zone period (the length of which is Td) from one of the first control signal Vgs1 and the second control signal Vgs2 to the inactive state, the first control signal Vgs1 and the second The other of the control signals Vgs2 is switched to the active state.

In this embodiment, when the bus voltage Vbus is greater than a preset first target voltage, the control module 6 increases the working ratio of the first control signal Vgs1 and reduces the working ratio of the second control signal Vgs2, and the bus voltage Reduce the first control when Vbus is less than the first target voltage The duty ratio of the signal Vgs1 is increased and the duty ratio of the second control signal Vgs2 is increased to stabilize the bus voltage Vbus at the first target voltage. The control module 6 also reduces the switching period of each of the first control signal Vgs1 and the second control signal Vgs2 when the output voltage Vout is greater than a preset second target voltage, and the output voltage Vout is smaller than the second target voltage. At this time, a switching period of each of the first control signal Vgs1 and the second control signal Vgs2 is increased to stabilize the output voltage Vout at the second target voltage. Therefore, for the first control signal Vgs1, its effective period (the length of which is Ta1) is determined by its switching period and its operating ratio, and for the second control signal Vgs2, its effective period (the length of which is Ta2) is Its switching period and its work ratio are determined.

In the present embodiment, under the control of the control module 6, the power factor correction module 4 operates in a discontinuous conduction mode to allow the phase of the current supplied by the voltage source 1 to follow the phase of the input voltage Vin provided by it. Thereby a high power factor is obtained.

Referring to FIGS. 3 through 9, the single-stage AC to DC converter of the present embodiment operates cyclically in the first mode to the sixth mode. In FIGS. 4 to 9, an intrinsic diode 421, 431 and a parasitic capacitance 422, 432 of each of the first switch 42 and the second switch 43 are drawn for simulating the non-ideal characteristics of the transformer 51. An imaginary magnetizing inductance 513 and an imaginary leakage inductance 514 are drawn, the controller 6 (see Fig. 1) is not drawn, and the conducting components are drawn in solid lines, and the non-conducting components are drawn in dashed lines. . 3 shows a first control signal Vgs1, a second control signal Vgs2, a current iLb flowing through the boosting inductor 44, and a magnetic flux inductance 513. The current iLm, the current iLr flowing through the leakage inductance 514, and the current iD2 flowing through the fourth switch 531 are related to time t. It should be noted that in Figure 3, the waveform of each of the currents iLb, iLm, iLr, iD2 simultaneously conveys information about the magnitude and direction of the current (ie, positive and negative values of this current indicate the current) In the opposite direction), in FIGS. 4 to 9, the direction of each of the currents iLb, iLm, iLr, iD2 is indicated by a corresponding arrow. In addition, the resonant capacitor 52 and the leakage inductance 514 can resonate at a resonant frequency determined by the capacitance of the resonant capacitor 52 and the inductance of the leakage inductance 514.

Referring to FIGS. 3 and 4, the single-stage AC to DC converter of the present embodiment operates in the first mode during a time point t0 to a time point t1. In the first mode, the first switch 42 is not turned on, and the second switch 43 is switched to be turned on in a zero voltage switching manner. The third switch 45 is switched to be turned on, the boost inductor 44 is charged, and the magnitude of the current iLb flowing through the boost inductor 44 rises linearly from zero. The magnitude of the current iLm flowing through the magnetizing inductance 513 gradually drops to zero, and then its direction is reversed and its magnitude gradually rises from zero. The magnitude of the current iLr flowing through the leakage inductance 514 gradually decreases to zero, and then its direction is reversed and its magnitude gradually rises from zero to a maximum value and then falls. The magnitude of the current iLm flowing through the magnetizing inductance 513 is not equal to the magnitude of the current iLr flowing through the leakage inductance 514. The fourth switch 531 is switched to be turned on, and energy is transferred to the output capacitor 532 and the load 2 via the transformer 51 and the fourth switch 531. The voltage across the first switch 42 is equal to the bus voltage Vbus. The voltage across the second switch 43 is equal to zero. 4 shows only the direction in which the direction of the current iLm flowing through the magnetizing inductance 513 and the direction of the current iLr of the leakage inductance 514 are reversed.

Referring to FIGS. 3 and 5, the single-stage AC to DC converter of the present embodiment operates in the second mode during a time point t1 to a time point t2. In the second mode, the first switch 42 remains non-conductive and the second switch 43 remains on. The third switch 45 is maintained in conduction, the boost inductor 44 is charged, and the magnitude of the current iLb flowing through the boost inductor 44 rises linearly. The magnitude of the current iLm flowing through the magnetizing inductance 513 gradually rises. The magnitude of the current iLr flowing through the leakage inductance 514 gradually increases. The magnitude of the current iLm flowing through the magnetizing inductance 513 is equal to the magnitude of the current iLr flowing through the leakage inductance 514. The fourth switch 531 switches to non-conduction in a zero current switching mode, and the energy stored in the output capacitor 532 is released to the load 2. The voltage across the first switch 42 is equal to the bus voltage Vbus. The voltage across the second switch 43 is equal to zero.

Referring to FIGS. 3 and 6, the single-stage AC to DC converter of the present embodiment operates in the third mode during a time point t2 to a time point t3. In the third mode, the first switch 11 remains non-conductive and the second switch 12 switches to non-conduction. The third switch 45 is maintained in conduction, the energy stored in the boost inductor 44 is released, and the magnitude of the current iLb flowing through the boost inductor 44 decreases linearly. The magnitude of the current iLm flowing through the magnetizing inductance 513 gradually decreases. The magnitude of the current iLr flowing through the leakage inductance 514 gradually decreases. The magnitude of the current iLm flowing through the magnetizing inductance 513 is equal to the magnitude of the current iLr flowing through the leakage inductance 514. The fourth switch 531 is maintained non-conducting, and the energy stored in the output capacitor 532 is released to the load 2. The energy stored in the parasitic capacitance 422 of the first switch 42 is released, so that the voltage across the first switch 42 drops from the bus voltage Vbus to zero, and then the intrinsic diode 421 of the first switch 42 is switched to be turned on, so that the first Cross-pressure dimension of switch 42 Hold at zero. The parasitic capacitance 432 of the second switch 43 is charged such that the voltage across the second switch 43 rises from zero to the bus voltage Vbus. The bus capacitor 3 is charged. FIG. 6 only shows the case after the parasitic capacitance 432 of the second switch 43 is charged.

Referring to FIGS. 3 and 7, the single-stage AC to DC converter of the present embodiment operates in the fourth mode during a time point t3 to a time point t4. In the fourth mode, the first switch 11 is switched to be turned on in a zero voltage switching manner, and the second switch 12 is maintained in a non-conducting state. The third switch 45 is maintained in conduction, the energy stored in the boost inductor 44 is released, and the magnitude of the current iLb flowing through the boost inductor 44 linearly drops to zero. The magnitude of the current iLm flowing through the magnetizing inductance 513 gradually drops to zero, and then its direction is reversed and its magnitude gradually rises from zero. The magnitude of the current iLr flowing through the leakage inductance 514 gradually decreases to zero, and then its direction is reversed and its magnitude gradually rises from zero. The magnitude of the current iLm flowing through the magnetizing inductance 513 is equal to the magnitude of the current iLr flowing through the leakage inductance 514. The fourth switch 531 is maintained non-conducting, and the energy stored in the output capacitor 532 is released to the load 2. The voltage across the first switch 42 is equal to zero. The voltage across the second switch 43 is equal to the bus voltage Vbus. The bus capacitor 3 is charged and then the energy stored therein is released. FIG. 7 only shows the direction before the direction of the current iLm flowing through the magnetizing inductance 513 and the direction of the current iLr flowing through the leakage inductance 514.

Referring to FIGS. 3 and 8, the single-stage AC to DC converter of the present embodiment operates in the fifth mode from time t4 to time t5. In the fifth mode, the first switch 42 is maintained in conduction and the second switch 43 is maintained in non-conduction. The third switch 45 is switched to non-conducting in a zero current switching manner. And the magnitude of the current iLb flowing through the boost inductor 44 is equal to zero. The magnitude of the current iLm flowing through the magnetizing inductance 513 gradually rises. The magnitude of the current iLr flowing through the leakage inductance 514 gradually increases. The magnitude of the current iLm flowing through the magnetizing inductance 513 is equal to the magnitude of the current iLr flowing through the leakage inductance 514. The fourth switch 531 is maintained non-conducting, and the energy stored in the output capacitor 532 is released to the load 2. The voltage across the first switch 42 is equal to zero. The voltage across the second switch 43 is equal to the bus voltage Vbus. The energy stored in the bus capacitor 3 is released.

Referring to FIGS. 3 and 9, the single-stage AC to DC converter of the present embodiment operates in the sixth mode from time t5 to time t6. In the sixth mode, the first switch 42 is switched to be non-conductive, and the second switch 43 is maintained to be non-conductive. The third switch 45 is maintained non-conducting, and the magnitude of the current iLb flowing through the boost inductor 44 is equal to zero. The magnitude of the current iLm flowing through the magnetizing inductance 513 gradually decreases. The magnitude of the current iLr flowing through the leakage inductance 514 gradually decreases. The magnitude of the current iLm flowing through the magnetizing inductance 513 is equal to the magnitude of the current iLr flowing through the leakage inductance 514. The fourth switch 531 is maintained non-conducting, and the energy stored in the output capacitor 532 is released to the load 2. The parasitic capacitance 422 of the first switch 42 is charged such that the voltage across the first switch 42 rises from zero to the bus voltage Vbus. The energy stored in the parasitic capacitance 432 of the second switch 43 is released, so that the voltage across the second switch 43 drops from the bus voltage Vbus to zero, and then the intrinsic diode 431 of the second switch 43 is switched to be turned on, so that the second The voltage across the switch 43 is maintained at zero. FIG. 9 only shows the case after the parasitic capacitance 422 of the first switch 42 is charged.

Referring to FIG. 1, in summary, the single-stage AC to DC converter of this embodiment has the following advantages:

1. By adjusting the duty ratio of each of the first control signal Vgs1 and the second control signal Vgs2 according to the bus voltage Vbus, the bus voltage Vbus can be prevented from changing as the condition of the load 2 changes. As a result, the input voltage Vin can have a wide range.

2. By the bus capacitor 3 acting as a relay for power conversion, the output voltage Vout can have a lower chopping.

3. The output voltage Vout may be constant by the controller 6 adjusting the switching period of each of the first control signal Vgs1 and the second control signal Vgs2 according to the output voltage Vout.

It should be noted that in other embodiments, the following modifications may be made to the embodiment:

1. The third switch 45 can be an N-type gold oxide half field effect transistor. At this time, the controller 6 is also coupled to the third switch 45, and controls the switching of the third switch 45 between conduction and non-conduction.

2. The fourth switch 531 can be an N-type gold oxide half field effect transistor. At this time, the controller 6 is also coupled to the fourth switch 531, and controls switching of the fourth switch 531 between conduction and non-conduction.

3. Referring to FIG. 10, the resonant converter module 52 can further include a resonant inductor 54 coupled between the resonant capacitor 52 and the primary winding 511. At this time, the resonance capacitor 52, the resonance inductor 54 and the leakage inductance 514 (see FIG. 9) are at a resonance frequency determined by the capacitance value of the resonance capacitor 52, the inductance value of the resonance inductor 54, and the inductance value of the leakage inductance 514 (see FIG. 9). resonance.

However, the above is only the embodiment of the present invention, and the scope of the invention is not limited thereto, and all the equivalent equivalent changes and modifications according to the scope of the patent application and the patent specification of the present invention are still The scope of the invention is covered.

1‧‧‧voltage source

2‧‧‧load

3‧‧‧Bus Capacitor

4‧‧‧Power Factor Correction Module

41‧‧‧Rectifier circuit

42‧‧‧First switch

43‧‧‧Second switch

44‧‧‧Boost Inductance

45‧‧‧third switch

5‧‧‧Resonance conversion module

51‧‧‧Transformers

511‧‧‧First winding

512‧‧‧second winding

52‧‧‧Resonant capacitor

53‧‧‧Rectifier filter circuit

531‧‧‧fourth switch

532‧‧‧ output capacitor

6‧‧‧Control module

Vbus‧‧‧ bus voltage

Vgs1‧‧‧ first control signal

Vgs2‧‧‧ second control signal

Vin‧‧‧Input voltage

Vout‧‧‧ output voltage

Claims (15)

A single-stage AC to DC converter comprising: a bus capacitor; a power factor correction module coupled to the bus capacitor, adapted to receive an AC input voltage, and to receive a first control signal and a second control And generating, according to the input voltage, the first control signal and the second control signal, a bus voltage that is DC across the bus capacitor, and an intermediate voltage that switches between the bus voltage and zero; a resonant conversion module coupled to the power factor correction module to receive the intermediate voltage, and generating a DC output voltage according to the intermediate voltage; and a control module coupled to the bus capacitor to receive the bus voltage, And generating, according to the bus voltage, the first control signal and the second control signal, each of the first control signal and the second control signal switching between an active state and an inactive state, and a working ratio thereof Associated with the bus voltage. The single-stage AC to DC converter of claim 1, wherein the control module increases a working ratio of the first control signal when the bus voltage is greater than a preset target voltage, and reduces the first And comparing a working ratio of the control signal, and when the bus voltage is less than the target voltage, reducing a working ratio of the first control signal and increasing a working ratio of the second control signal. A single-stage AC to DC converter as described in claim 1 The control module is further electrically connected to the resonant converter module to receive the output voltage, and further generates the first control signal and the second control signal according to the output voltage, the first control signal and the second control The switching period of each of the signals is associated with the output voltage. The single-stage AC to DC converter of claim 3, wherein the control module reduces the first control signal and the second control signal when the output voltage is greater than a predetermined target voltage Each of the switching cycles, and when the output voltage is less than the target voltage, increasing a switching period of each of the first control signal and the second control signal. The single-stage AC to DC converter of claim 1, wherein the first control signal and the second control signal have the same switching period, and alternately in the active state, when the first control signal And when one of the second control signals is in the active state, the other of the first control signal and the second control signal is in the inactive state. The single-stage AC to DC converter of claim 5, wherein a preset is calculated from a point of switching from one of the first control signal and the second control signal to each of the inactive states After the dead zone period, the other of the first control signal and the second control signal is switched to the active state. The single-stage AC to DC converter of claim 1, wherein the power factor correction module operates in a discontinuous conduction mode. The single-stage AC to DC converter of claim 1, wherein the bus capacitor has a first end and a second end, the total The line voltage is greater than the amplitude of the input voltage, and the power factor correction module includes: a rectifier circuit having a first input terminal, a second input terminal, a first output terminal, and a coupling to the bus capacitor a second output of the second end receiving the input voltage from a first input thereof and a second input thereof; a first switch having a first end coupled to the first end of the bus capacitor, a second end coupled to the resonant converter module, and a control end coupled to the control module to receive the first control signal; a second switch having a coupled to the first switch a first end of the second end, a second end coupled to the second output end of the rectifier circuit, and a control end coupled to the control module to receive the second control signal, the cross of the second switch The voltage acts as the intermediate voltage; and a boost inductor and a third switch are connected in series between the first output of the rectifier circuit and the second end of the first switch. The single-stage AC to DC converter of claim 8, wherein each of the first switch and the second switch is an N-type MOS field effect transistor, and the third switch is a Diode. The single-stage AC to DC converter of claim 8, wherein the boost inductor is coupled to the first output of the rectifier circuit, and the third switch is coupled to the first switch Second end. A single-stage AC to DC converter as claimed in claim 8 wherein the rectifier circuit is a full bridge rectifier circuit. The single-stage AC to DC converter of claim 1, wherein the resonant converter module comprises: a transformer including a primary winding and a secondary winding; and a resonant capacitor connected in series with the primary winding The resonant capacitor and the primary winding are coupled to the power factor correction module to receive the intermediate voltage; and a rectifying and filtering circuit coupled to the secondary winding and providing the output voltage. The single-stage AC to DC converter of claim 12, wherein the resonant converter module further includes a resonant inductor coupled between the resonant capacitor and the primary winding. The single-stage AC to DC converter of claim 12, wherein the rectifying and filtering circuit includes a switch connected in series between the two ends of the secondary winding and an output capacitor, the cross-voltage of the output capacitor acts as The output voltage. A single-stage AC to DC converter as claimed in claim 14, wherein the switch is a diode.