TWI885499B - Forward converter and forward power factor corrector - Google Patents

Abstract

A forward converter includes a voltage converting device, a switch and an assistance device. The voltage converting device includes a primary coil and a secondary coil, and is configured to convert an input voltage into an output voltage. The switch is connected to the voltage converting device, and is switched to make the voltage converting device receive or not receive the input voltage. The assistance device is connected to the voltage converting device. When the switch is cut off, the assistance device stores electrical energy released by the voltage converting device and generates a compensating voltage, and when the switch is turned on, the assistance device provides the compensating voltage, wherein the compensating voltage and the input voltage have same polarity. The present disclosure further provides a forward power factor corrector including the forward converter described above and a rectifying device.

Description

Forward converter and forward power factor corrector

The present invention relates to a forward converter and a forward power factor corrector.

Currently, many electrical appliances use low-voltage direct current, but since the mains is alternating current, it needs to be converted from AC to DC. In order to reduce the phantom power of the power system and reduce the system interference caused by current harmonics, many electrical appliances are required to have high power factor and low current harmonics, so power factor correctors are widely used.

Based on safety and performance considerations, power factor correctors are required to have high power factor, high conversion efficiency and electrical isolation. The conversion efficiency of conventional circuit structures such as flyback is relatively poor; and when the input AC power is at a low voltage, if the inductive voltage on the secondary side is less than the output voltage at the output end of the power factor corrector, the input current cannot be introduced, thus causing a current dead zone. Therefore, the power factor correction effect is not good, and the demagnetization requirements of the transformer need to be additionally processed. Other conventional technologies and circuit structures also face different technical bottlenecks and cannot meet the increasingly stringent regulatory requirements.

In view of the above, the present invention provides a forward converter and a forward power factor corrector.

According to an embodiment of the present invention, a forward converter includes a voltage conversion device, a switch and an auxiliary device. The voltage conversion device includes a primary winding and a secondary winding, and is used to convert an input voltage into an output voltage. The switch is connected to the voltage conversion device and is switched so that the voltage conversion device receives or does not receive the input voltage. The auxiliary device is connected to the voltage conversion device, and when the switch is turned off, the electric energy released by the voltage conversion device is stored and a compensation voltage is generated, and when the switch is turned on, the compensation voltage is provided, wherein the compensation voltage has the same polarity as the input voltage.

According to an embodiment of the present invention, a forward-type power factor corrector comprises the forward-type converter and a rectifier as described above. The rectifier is connected to the forward-type converter and is used to receive and rectify the power supply to generate an input voltage.

Through the above structure, the forward converter disclosed in this case can have the advantages of high conversion efficiency, satisfying the transformer winding demagnetization requirements, providing compensation voltage, small size and light weight through the setting of auxiliary devices, and can not add additional complex and high-cost mechanisms. In addition to the above advantages, the forward power factor corrector disclosed in this case including the forward converter can reduce the current blind area through the compensation voltage of the auxiliary device, and can achieve the effect of high power factor and low harmonic rate.

The above description of the disclosed content and the following description of the implementation method are used to demonstrate and explain the spirit and principle of the present invention, and provide a further explanation of the scope of the patent application of the present invention.

1,1_1,1_2,1_3,1_4,1_5,1_6: Forward converter

2: Rectifier

3: Filter device

10,10_1,10_2,10_3,10_4,10_5,10_6: switch

20,20_1,20_2,20_3,20_4,20_5,20_6: Voltage conversion device

30,30_1,30_2,30_3,30_4,30_5,30_6: Auxiliary devices

100,100’: Forward-type power factor corrector

V _s : Power supply

V _i : Input voltage

V _o : Output voltage

V _ca : Compensation voltage

D ₂₁ ,D ₂₂ ,D ₂₃ ,D ₂₄ : Diode

Q1: Active power switching element

201,N1: primary side winding group

202, N2: Secondary winding group

La1, La2, La3, La4, La5: Auxiliary winding

Da1, Da2, Da3, Da4, Da5: Auxiliary diodes

D1,D2: Flywheel diode

L1: Energy storage inductor

L _f : Inductance

C1: output capacitor

Ca: auxiliary capacitor

D _f : Capacitance

Vgs, Vds: voltage

Ids,Is,I2:current

d1: Demagnetization interval

FIG1 is a block diagram of a forward converter according to an embodiment of the present invention.

FIG2 is a block diagram of a forward-type power factor corrector according to an embodiment of the present invention.

FIG3 is a block diagram of a forward-type power factor corrector according to another embodiment of the present invention.

FIG. 4 exemplarily shows the circuit diagram of the rectifier and filter device included in the forward power factor corrector of FIG. 3.

FIG5 is a circuit diagram of a forward converter according to the first embodiment of the present invention.

FIG. 6A to FIG. 6C respectively illustrate the first operating mode, the second operating mode, and the third operating mode of the forward converter of FIG. 5 .

FIG. 7 is a circuit diagram of a forward converter according to the second embodiment of the present invention.

FIG8A to FIG8D respectively illustrate the first operating mode, the second operating mode, the third operating mode and the fourth operating mode of the forward converter of FIG7.

FIG9 is a circuit diagram of a forward converter according to the third embodiment of the present invention.

FIG. 10A to FIG. 10C respectively illustrate the first operating mode, the second operating mode, and the third operating mode of the forward converter of FIG. 9 .

FIG11 is a circuit diagram of a forward converter according to the fourth embodiment of the present invention.

FIG. 12A to FIG. 12D respectively illustrate the first operating mode, the second operating mode, the third operating mode and the fourth operating mode of the forward converter of FIG. 11 .

FIG13 is a circuit diagram of a forward converter according to the fifth embodiment of the present invention.

FIG. 14A to FIG. 14C respectively illustrate the first operating mode, the second operating mode, and the third operating mode of the forward converter of FIG. 13 .

FIG15 is a circuit diagram of a forward converter according to the sixth embodiment of the present invention.

FIG. 16A to FIG. 16D respectively illustrate the first operating mode, the second operating mode, the third operating mode and the fourth operating mode of the forward converter of FIG. 15 .

FIG. 17 exemplarily shows the waveforms of the gate-source voltage, the current flowing through, and the drain-source voltage of the switch of the forward converter of an embodiment of the present invention.

FIG. 18 exemplarily shows the relationship between the output voltage and the switch duty cycle of the forward power factor corrector of an embodiment of the present invention.

The detailed features and advantages of the present invention are described in detail in the following implementation method. The content is sufficient for anyone familiar with the relevant technology to understand the technical content of the present invention and implement it accordingly. According to the content disclosed in this specification, the scope of the patent application and the drawings, anyone familiar with the relevant technology can easily understand the relevant purposes and advantages of the present invention. The following embodiments are to further illustrate the viewpoints of the present invention, but do not limit the scope of the present invention by any viewpoint.

Please refer to FIG. 1, which is a block diagram of a forward converter according to an embodiment of the present invention. As shown in FIG. 1, the forward converter 1 includes a switch 10, a voltage conversion device 20, and an auxiliary device 30. The switch 10 is connected to the voltage conversion device 20, and the voltage conversion device 20 is connected to the auxiliary device 30.

The switch 10 is used to switch so that the voltage conversion device 20 receives or does not receive the input voltage. For example, the switch 10 can be an active power switch element, which is used to be triggered to cut off or conduct, so that the voltage conversion device 20 receives or does not receive the input voltage.

The voltage conversion device 20 includes a primary winding 201 and a secondary winding 202, and is used to convert an input voltage into an output voltage. The primary winding 201 and the secondary winding 202 each include one or more coils. In one embodiment, the voltage conversion device 20 may further include a flywheel diode, an energy storage inductor, and an output capacitor. The first end of the energy storage inductor is used to output the output voltage. The cathode end of the flywheel diode and the second end of the energy storage inductor can be connected to a first node together, and the first node can be connected to the auxiliary device 30. One end of the output capacitor can be connected to the other end of the energy storage inductor, and the other end of the output capacitor can be connected to the anode end of the flywheel diode.

The auxiliary device 30 may include one or more passive elements. One end of the auxiliary device 30 is connected to the secondary winding 202, and the other end of the auxiliary device 30 is connected to the second end of the energy storage inductor of the voltage conversion device 20. Alternatively, one end of the auxiliary device 30 is used to receive the input voltage, and the other end of the auxiliary device 30 is connected to the primary winding N1. When the switch 10 is turned off, the auxiliary device 30 stores the electric energy released by the voltage conversion device 20 and generates a compensation voltage; when the switch 10 is turned on, the auxiliary device 30 provides a compensation voltage, wherein the compensation voltage has the same polarity as the input voltage.

By storing the electric energy released by the voltage conversion device when the switch is turned off and generating a compensation voltage, the forward converter can have a demagnetization function and can provide a compensation voltage when the switch is turned on. In particular, in AC input applications, the compensation voltage can reduce the current dead zone condition.

Please refer to FIG. 2, which is a block diagram of a forward power factor corrector according to an embodiment of the present invention. As shown in FIG. 2, the forward power factor corrector 100 includes a forward converter 1 and a rectifier 2. The forward converter 1 can be the forward converter 1 shown in FIG. 1. The rectifier 2 is connected to the power source _Vs and the forward converter 1, and the rectifier 2 is used to receive and rectify the power source _Vs to generate the aforementioned input voltage. Specifically, the power source _Vs can provide alternating current, which is converted into direct current by the rectifier 2 and provided to the forward converter 1. The forward converter 1 converts an input voltage into an output voltage V _o , wherein the output voltage V _o can be output to a load connected to the forward converter 1 .

Please refer to FIG. 3, which is a block diagram of a forward-type power factor corrector according to another embodiment of the present invention. As shown in FIG. 3, the forward-type power factor corrector 100' comprises a forward-type converter 1, a rectifier 2 and a filter 3. The rectifier 2 is connected to the forward-type converter 1 and the filter 3, wherein the connection relationship and operation of the forward-type converter 1 and the rectifier 2 are the same as those in the above embodiment, and are not described in detail here. In this embodiment, the filter 3 is connected between the rectifier 2 and the power source _Vs to filter the AC power first and then transmit the filtered AC power to the rectifier 2 for AC-DC conversion.

To further explain the circuits of the filter device 3 and the rectifier device 2, please refer to FIG4, which exemplarily shows a circuit diagram of the rectifier device 2 and the filter device 3 included in the forward power factor corrector 100' of FIG3. As shown in FIG4, the rectifier device 2 may include a first diode _D21 , a second diode _D22 , a third diode _D23 , and a fourth diode _D24 . The anode terminal of the first diode D ₂₁ is connected to the cathode terminal of the third diode D ₂₃ , the cathode terminal of the first diode D ₂₁ is connected to the cathode terminal of the second diode D ₂₂ , the anode terminal of the second diode D ₂₂ is connected to the cathode terminal of the fourth diode D ₂₄ , and the anode terminal of the third diode D ₂₃ is connected to the anode terminal of the fourth diode D _24. The filter device 3 may include a capacitor D _f and an inductor L _f . A first end of capacitor _Df is connected to a first end of inductor _Lf , an anode of first diode _D21 and a cathode of third diode _D23 , a second end of capacitor _Df is connected to power source _Vs , an anode of second diode _D22 and a cathode of fourth diode _D24 . A second end of inductor _Lf is connected to power source _Vs.

The filter device 3 is used to receive and filter the power source _Vs to generate the filtered power source _Vs , and the rectifier device 2 is used to receive and rectify the filtered power source _Vs to generate the aforementioned input voltage V _i between the cathode terminal of the second diode _D22 and the anode terminal of the fourth diode D24. The forward converter 1 converts the input voltage V _i into an output voltage V _o , wherein the output voltage V _o can be output to a load connected to the forward converter 1. It should be particularly noted here that FIG. 4 shows a basic circuit that can realize the rectifier device 2 and the filter device 3, and it is not intended to limit the rectifier device 2 and the filter device 3 to only the circuit structure shown in FIG. 4. In addition, the filter device 3 shown in FIG. 4 is a selectively arranged circuit.

The following further describes multiple embodiments of implementing the above-mentioned forward converter 1. Please refer to FIG. 5, which is a circuit diagram of a forward converter according to the first embodiment of the present invention. As shown in FIG. 5, the forward converter 1_1 includes a switch 10_1, a voltage conversion device 20_1, and an auxiliary device 30_1.

The switch 10_1 includes an active power switch element Q1. The voltage conversion device 20_1 includes a primary winding N1 and a secondary winding N2 as well as the flywheel diode D1, the energy storage inductor L1 and the output capacitor C1 as mentioned above. The auxiliary device 30_1 includes an auxiliary capacitor Ca.

Specifically, the first end of the energy storage inductor L1 is used to output the output voltage V _o , the second end of the energy storage inductor L1 is connected to the cathode end of the flywheel diode D1 , one end of the auxiliary capacitor Ca of the auxiliary device 30_1 is connected to the secondary winding N2 , and the other end of the auxiliary capacitor Ca is connected to the second end of the energy storage inductor L1 and the cathode end of the flywheel diode D1 .

Please refer to FIG. 5 and FIG. 6A to FIG. 6C together, wherein FIG. 6A to FIG. 6C respectively illustrate the first operating mode, the second operating mode and the third operating mode of the forward converter of FIG. 5 .

Please refer to FIG. 6A , in the first operation mode, the active power switch element Q1 is turned on and the flywheel diode D1 is turned off. When the active power switch element Q1 is in the on state, the input voltage _Vi supplies power to the primary winding N1 of the voltage conversion device 20_1, and the inductive voltage of the secondary winding N2 of the voltage conversion device 20_1 and the compensation voltage _Vca of the auxiliary capacitor Ca together charge the output capacitor C1. At this time, the energy storage inductor L1 stores energy, and the auxiliary capacitor Ca is in a discharge state. This operation mode continues until the active power switch element Q1 is turned off and enters the second operation mode.

Please refer to FIG. 6B . In the second operation mode, the active power switch element Q1 is turned off and the flywheel diode D1 is turned on. The magnetized secondary winding N2 can be demagnetized through the path formed by the flywheel diode D1 to the auxiliary capacitor Ca, and the auxiliary capacitor Ca can be charged to establish the compensation voltage V _ca . The energy storage inductor L1 can release energy through the path formed by the output capacitor C1 and the flywheel diode D1. This operation mode continues until the secondary winding N2 and the energy storage inductor L1 have released all their energy, and then enters the third operation mode.

Please refer to FIG. 6C. In the third operation mode, the active power switch element Q1 and the flywheel diode D1 are turned off, and the forward converter is in a non-conversion state. The energy stored in the output capacitor C1 can continue to provide current to the load. Then, when the active power switch element Q1 is turned on again, the energy stored in the auxiliary capacitor Ca is used to charge the output capacitor C1, that is, the forward converter 1_1 returns to the first operation mode of FIG. 6A. In particular, in the application of the forward converter of this embodiment in the circuit design operating in the continuous current mode, the third operation mode may not exist, that is, it can directly return to the first operation mode after the second operation mode.

Please refer to FIG. 7, which is a circuit diagram of a forward converter according to the second embodiment of the present invention. As shown in FIG. 7, the forward converter 1_2 includes a switch 10_2, a voltage conversion device 20_2, and an auxiliary device 30_2, wherein the implementation circuit/device, function, and connection relationship of the switch 10_2 and the voltage conversion device 20_2 may be the same as the switch 10_1 and the voltage conversion device 20_1 included in the forward converter 1_1 of FIG. 5.

The auxiliary device 30_2 includes an auxiliary capacitor Ca, an auxiliary diode Da1, and an auxiliary winding La1. The anode end of the auxiliary diode Da1 is connected to the first end of the auxiliary capacitor Ca. The auxiliary winding La1 is coupled to the energy storage inductor L1 of the voltage conversion device 20_2, one end of the auxiliary winding La1 is connected to the cathode end of the auxiliary diode Da1, and the other end of the auxiliary winding La1 is connected to the second end of the auxiliary capacitor Ca.

Please refer to FIG. 7 and FIG. 8A to FIG. 8D together, wherein FIG. 8A to FIG. 8D respectively illustrate the first operating mode, the second operating mode, the third operating mode and the fourth operating mode of the forward converter of FIG. 7 .

Please refer to FIG8A. In the first operation mode, the active power switch element Q1 is turned on, the auxiliary diode Da1 is turned off, and the flywheel diode D1 is turned off. When the active power switch element Q1 is in the on state, the input voltage _Vi supplies power to the primary winding N1 of the voltage conversion device 20_2, and the inductive voltage of the secondary winding N2 of the voltage conversion device 20_2 and the compensation voltage _Vca of the auxiliary capacitor Ca together charge the output capacitor C1. At this time, the energy storage inductor L1 stores energy, the auxiliary capacitor Ca is in a discharge state, and _Vca decreases. This operation mode continues until the active power switch element Q1 is turned off and enters the second operation mode.

Please refer to FIG. 8B . In the second operation mode, the active power switch element Q1 is turned off, the auxiliary diode Da1 is turned on, and the flywheel diode D1 is turned off. The magnetized secondary winding N2 can be demagnetized through the path formed by the auxiliary diode Da1 to the auxiliary capacitor Ca, and the auxiliary capacitor Ca can be charged to establish the compensation voltage V _ca , and V _ca rises. The energy storage inductor L1 can release the stored energy to the auxiliary capacitor Ca through the auxiliary winding La1. This operation mode continues until the compensation voltage V _ca is equal to the first mapping voltage, and enters the third operation mode. The first mapped voltage is the output voltage _Vo mapped to the equivalent voltage on the auxiliary winding La1 side according to the turns ratio between the energy storage inductor L1 and the auxiliary winding La1.

Please refer to FIG. 8C . In the third operation mode, the active power switch element Q1 is turned off, the auxiliary diode Da1 is turned off, and the flywheel diode D1 is turned on. The magnetized secondary winding N2 continues to be demagnetized through the path formed by the flywheel diode D1 to the auxiliary capacitor Ca, and the auxiliary capacitor Ca can be charged to establish the compensation voltage V _ca . The inductor L1 releases the stored energy through the path formed by D1 and the output capacitor C1. This operation mode continues until the energy of the energy storage inductor L1 and the magnetized secondary winding N2 is completely released, and enters the fourth operation mode.

Please refer to FIG8D. In the fourth operation mode, the active power switch element Q1, the flywheel diode D1 and the auxiliary diode Da1 are all turned off, and the forward converter is in a non-conversion state. The energy stored in the output capacitor C1 can continue to provide current to the load. Then, when the active power switch Q1 is turned on again, the energy stored in the auxiliary capacitor Ca is used to charge the output capacitor C1, that is, the forward converter 1_2 returns to the first operation mode of FIG8A. In particular, in the application of the forward converter of this embodiment in the circuit design operating in the continuous current mode, the fourth operation mode may not exist, that is, it can directly return to the first operation mode after the third operation mode.

Please refer to FIG. 9, which is a circuit diagram of a forward converter according to the third embodiment of the present invention. As shown in FIG. 9, the forward converter 1_3 includes a switch 10_3, a voltage conversion device 20_3, and an auxiliary device 30_3, wherein the implementation circuit/device, function, and connection relationship of the switch 10_3 and the voltage conversion device 20_3 can be the same as the switch 10_1 and the voltage conversion device 20_1 included in the forward converter 1_1 of FIG. 5, and will not be described in detail here.

The auxiliary device 30_2 includes an auxiliary capacitor Ca, an auxiliary diode Da2, and an auxiliary winding La2. The anode end of the auxiliary diode Da2 is connected to the first end of the auxiliary capacitor Ca. The auxiliary winding La2 is coupled to the primary winding N1 and the secondary winding N2. One end of the auxiliary winding La2 is connected to the cathode end of the auxiliary diode Da2, and the other end of the auxiliary winding La2 is connected to the second end of the auxiliary capacitor Ca.

Please refer to FIG. 9 and FIG. 10A to FIG. 10C together, wherein FIG. 10A to FIG. 10C respectively illustrate the first operating mode, the second operating mode and the third operating mode of the forward converter of FIG. 9 .

Please refer to FIG. 10A , in the first operation mode, the active power switch element Q1 is turned on, the auxiliary diode Da2 is turned off, and the flywheel diode D1 is turned off. When the active power switch element Q1 is in the on state, the input voltage _Vi supplies power to the primary winding N1 of the voltage conversion device 20_3, and the inductive voltage of the secondary winding N2 of the voltage conversion device 20_3 and the compensation voltage _Vca of the auxiliary capacitor Ca together charge the output capacitor C1. At this time, the energy storage inductor L1 stores energy, and the auxiliary capacitor Ca is in a discharge state. This operation mode continues until the active power switch element Q1 is turned off and enters the second operation mode.

Please refer to FIG. 10B , in the second operation mode, the active power switch element Q1 is turned off, the auxiliary diode Da2 is turned on, and the flywheel diode D1 is turned on. Since the auxiliary winding La2 is coupled with the primary winding N1 and the secondary winding N2, the energy stored in the primary winding N1 and the secondary winding N2 can be released from the auxiliary winding La2 for demagnetization, and the auxiliary capacitor Ca can be charged to establish the compensation voltage V _ca . The energy storage inductor L1 can release energy through the path formed by the output capacitor C1 and the flywheel diode D1. This operation mode continues until the demagnetization is completed and the energy storage inductor L1 completes the energy release. In particular, in some embodiments, the demagnetization of the auxiliary winding La2 through the auxiliary diode Da2 and the auxiliary capacitor Ca and the energy release of the energy storage inductor L1 through the output capacitor C1 and the flywheel diode D1 can be completed at different times. When the demagnetization of the auxiliary winding La2 and the energy release of the energy storage inductor L1 are completed, the auxiliary device 30_2 enters the third operation mode.

Please refer to FIG. 10C . In the third operation mode, since the energy stored in the energy storage inductor L1 has been completely released, the current on the energy storage inductor L1 drops to zero. After the magnetized secondary winding N2 has completely released its energy in the second operation mode, the current on the auxiliary capacitor Ca drops to zero. The flywheel diode D1 and the auxiliary diode Da2 both enter the cut-off state, while the active power switch element Q1 remains in the cut-off state. The energy stored in the output capacitor C1 can continue to provide current to the load. When the active power switch element Q1 is triggered to conduct again, the energy stored in the auxiliary capacitor Ca is used to charge the output capacitor C1, that is, the forward converter 1_3 returns to the first operation mode again. In particular, in the application where the forward converter of this embodiment is designed to operate in the continuous current mode, the third operation mode may not exist, that is, the first operation mode may be directly returned to after the second operation mode.

Please refer to FIG. 11, which is a circuit diagram of a forward converter according to the fourth embodiment of the present invention. As shown in FIG. 11, the forward converter 1_4 includes a switch 10_4, a voltage conversion device 20_4, and an auxiliary device 30_4, wherein the implementation circuit/device, function, and connection relationship of the switch 10_4 may be the same as the switch 10_1 included in the forward converter 1_1 of FIG. 5, and the implementation circuit/device, function, and connection relationship of the voltage conversion device 20_4 may be the same as the voltage conversion device 20_2 included in the forward converter 1_2 of FIG. 7, which will not be described in detail here.

The auxiliary device 30_4 includes an auxiliary capacitor Ca, a first auxiliary diode Da2, a first auxiliary winding La2, a second auxiliary diode Da3 and a second auxiliary winding La3. The anode end of the first auxiliary diode Da2 is connected to the first end of the auxiliary capacitor Ca. The first auxiliary winding La2 is coupled to the primary winding N1 and the secondary winding N2, wherein one end of the first auxiliary winding La2 is connected to the cathode end of the first auxiliary diode Da2, and the other end of the first auxiliary winding La2 is connected to the second end of the auxiliary capacitor Ca. The anode end of the second auxiliary diode Da3 is connected to the first end of the auxiliary capacitor Ca. One end of the second auxiliary winding La3 is connected to the cathode end of the second auxiliary diode Da3, and the other end of the second auxiliary winding La3 is connected to the second end of the auxiliary capacitor Ca. The second auxiliary winding La3 is coupled to the energy storage inductor L1.

Please refer to FIG. 11 and FIG. 12A to FIG. 12D together, wherein FIG. 12A to FIG. 12D respectively illustrate the first operating mode, the second operating mode, the third operating mode and the fourth operating mode of the forward converter of FIG. 11 .

Please refer to FIG. 12A , in the first operation mode, the active power switch element Q1 is turned on, the first auxiliary diode Da2 is turned off, the second auxiliary diode Da3 is turned off, and the flywheel diode D1 is turned off. When the active power switch element Q1 is in the on state, the input voltage _Vi supplies power to the primary winding N1 of the voltage conversion device 20_4, and the inductive voltage of the secondary winding N2 of the voltage conversion device 20_4 and the compensation voltage _Vca of the auxiliary capacitor Ca together charge the output capacitor C1. At this time, the energy storage inductor L1 stores energy, and the auxiliary capacitor Ca is in a discharge state. This operation mode continues until the active power switch element Q1 is turned off and enters the second operation mode.

Please refer to FIG. 12B , in the second operation mode, the active power switch element Q1 is turned off, the first auxiliary diode Da2 is turned on, the second auxiliary diode Da3 is turned on, and the flywheel diode D1 is turned off. Since the first auxiliary winding La2 is coupled with the primary winding N1 and the secondary winding N2, the magnetized secondary winding N2 can release energy through the path formed by the first auxiliary diode Da2 to the auxiliary capacitor Ca through the coupling inductance with the first auxiliary winding La2 to demagnetize, and can charge the auxiliary capacitor Ca to establish the compensation voltage V _ca . Since the second auxiliary winding La3 and the energy storage inductor L1 are coupled to each other, the energy stored in the energy storage inductor L1 can be released from the second auxiliary winding La3 to charge the auxiliary capacitor Ca. Therefore, the compensation voltage _Vca rises. This operation mode continues until the compensation voltage _Vca is equal to the second mapping voltage, and enters the third operation mode. The second mapping voltage is the output voltage _Vo mapped to the equivalent voltage on the second auxiliary winding La3 side according to the turns ratio of the energy storage inductor L1 and the second auxiliary winding La3.

Please refer to FIG. 12C . In the third operation mode, the active power switch element Q1 is turned off, the first auxiliary diode Da2 is turned on, the second auxiliary diode Da3 is turned off, and the flywheel diode D1 is turned on. The magnetized secondary winding N2 continues to be demagnetized through the path formed by the first auxiliary diode Da2 to the auxiliary capacitor Ca, and continues to charge the auxiliary capacitor Ca to establish the compensation voltage V _ca . The energy storage inductor L1 continues to release energy to charge the output capacitor C1. This operation mode continues until the energy of the magnetized secondary winding N2 and the energy storage inductor L1 is completely released, and enters the fourth operation mode.

Please refer to FIG. 12D , when the magnetized secondary winding N2 and the energy storage inductor L1 are completely released in the third operation mode, the current on the auxiliary capacitor Ca and the energy storage inductor L1 drops to zero, and the first auxiliary diode Da2, the second auxiliary diode Da3 and the flywheel diode D1 are all in the cut-off state. The energy stored in the output capacitor C1 can continue to provide current to the load. When the active power switch element Q1 is triggered to conduct again, the energy stored in the auxiliary capacitor Ca is used to charge the output capacitor C1, that is, the forward converter 1_4 returns to the first operation mode again. In particular, in the application where the forward converter of this embodiment is designed to operate in the continuous current mode, the fourth operation mode may not exist, that is, the first operation mode may be directly returned to after the third operation mode.

Please refer to FIG. 13, which is a circuit diagram of a forward converter according to the fifth embodiment of the present invention. As shown in FIG. 13, the forward converter 1_5 includes a switch 10_5, a voltage conversion device 20_5, and an auxiliary device 30_5, wherein the implementation circuit/device and function of the switch 10_5 may be the same as the switch 10_1 included in the forward converter 1_1 of FIG. 5, and will not be described in detail here.

In addition to the components of the voltage conversion device 20_1 shown in FIG5 , the voltage conversion device 20_5 of the forward converter 1_5 further includes another flywheel diode D2, the anode end of the flywheel diode D2 is connected to the secondary winding N2, and the cathode end of the flywheel diode D2 is connected to the second end of the energy storage inductor L1.

The auxiliary device 30_5 is disposed on the primary side of the forward converter 1_5. Specifically, one end of the auxiliary device 30_5 is used to receive the input voltage V _i , and the other end of the auxiliary device 30_5 is connected to the primary winding N1. The auxiliary device 30_5 includes an auxiliary capacitor Ca, an auxiliary diode Da4, and an auxiliary winding La4. The first end of the auxiliary capacitor Ca is used to receive the input voltage V _i , and the second end of the auxiliary capacitor Ca is connected to the primary winding N1. The anode end of the auxiliary diode Da4 is connected to the first end of the auxiliary capacitor Ca. The auxiliary winding La4 is coupled to the primary winding N1 and the secondary winding N2, wherein one end of the auxiliary winding La4 is connected to the cathode end of the auxiliary diode Da4, and the other end of the auxiliary winding La4 is connected to the second end of the auxiliary capacitor Ca.

Please refer to FIG. 13 and FIG. 14A to FIG. 14C together, wherein FIG. 14A to FIG. 14C respectively illustrate the first operating mode, the second operating mode and the third operating mode of the forward converter of FIG. 13 .

Please refer to FIG. 14A . In the first operation mode, the active power switch element Q1 is turned on, the auxiliary diode Da4 is turned off, the flywheel diode D1 is turned off, and the flywheel diode D2 is turned on. When the active power switch element Q1 is in the on state, the input voltage _Vi and the auxiliary capacitor Ca supply power to the primary winding N1 of the voltage conversion device 20_5, and the inductive voltage of the secondary winding N2 of the voltage conversion device 20_5 charges the output capacitor C1 through the flywheel diode D2. At this time, the energy storage inductor L1 stores energy, and the auxiliary capacitor Ca is in a discharge state. This operation mode continues until the active power switch element Q1 is turned off, and enters the second operation mode.

Please refer to FIG. 14B , in the second operation mode, the active power switch element Q1 is turned off, the auxiliary diode Da4 is turned on, the flywheel diode D1 is turned on, and the flywheel diode D2 is turned off. Since the auxiliary winding La4 is coupled with the primary winding N1 and the secondary winding N2, the energy stored in the primary winding N1 and the secondary winding N2 can be released from the auxiliary winding La4 for demagnetization, and the auxiliary capacitor Ca can be charged to establish the compensation voltage V _ca . The energy storage inductor L1 can release energy through the path formed by the output capacitor C1 and the flywheel diode D1. This operation mode continues until the demagnetization is completed and the energy storage inductor L1 completes the energy release. In particular, in some embodiments, the demagnetization of the auxiliary winding La4 through the auxiliary diode Da4 and the auxiliary capacitor Ca and the energy release of the energy storage inductor L1 through the output capacitor C1 and the flywheel diode D1 can be completed at different times. When the demagnetization of the auxiliary winding La4 and the energy release of the energy storage inductor L1 are completed, the auxiliary device 30_5 enters the third operation mode.

Please refer to FIG. 14C . In the third operation mode, the energy stored in the primary winding N1 and the secondary winding N2 has been completely released. After the energy storage inductor L1 has been completely released in the second operation mode, the current on the energy storage inductor L1 drops to zero, and the active power switch element Q1, the flywheel diodes D1 and D2, and the auxiliary diode Da4 all enter the cut-off state. When the active power switch element Q1 is triggered to conduct again, the energy stored in the auxiliary capacitor Ca is used to charge the output capacitor C1, that is, the forward converter 1_5 returns to the first operation mode again. The energy stored in the output capacitor C1 can continue to provide current to the load. In particular, in the application where the forward converter of this embodiment is designed to operate in the continuous current mode, the third operation mode may not exist, that is, the first operation mode may be directly returned to after the second operation mode.

Please refer to FIG. 15, which is a circuit diagram of a forward converter according to the sixth embodiment of the present invention. As shown in FIG. 15, the forward converter 1_6 includes a switch 10_6, a voltage conversion device 20_6 and an auxiliary device 30_6, wherein the implementation circuit/device and function of the switch 10_6 and the voltage conversion device 20_6 can be the same as the switch 10_5 and the voltage conversion device 20_5 included in the forward converter 1_5 of FIG. 13, and will not be described in detail here.

The auxiliary device 30_6 is disposed on the primary side of the forward converter 1_6. The auxiliary device 30_6 includes an auxiliary capacitor Ca, a first auxiliary diode Da4, a second auxiliary diode Da5, a first auxiliary winding La4, and a second auxiliary winding La5. The first end of the auxiliary capacitor Ca is used to receive the input voltage V _i , and the second end of the auxiliary capacitor Ca is connected to the primary winding N1. The anode end of the first auxiliary diode Da4 is connected to the first end of the auxiliary capacitor Ca. The first auxiliary winding La4 is coupled to the primary winding N1 and the secondary winding N2. One end of the first auxiliary winding La4 is connected to the cathode end of the first auxiliary diode Da4, and the other end of the first auxiliary winding La4 is connected to the second end of the auxiliary capacitor Ca. The anode end of the second auxiliary diode Da5 is connected to the first end of the auxiliary capacitor Ca. The second auxiliary winding La5 is coupled to the energy storage inductor L1. One end of the second auxiliary winding La5 is connected to the cathode end of the second auxiliary diode Da5, and the other end of the second auxiliary winding La5 is connected to the second end of the auxiliary capacitor Ca.

Please refer to FIG. 15 and FIG. 16A to FIG. 16D together, wherein FIG. 16A to FIG. 16D respectively illustrate the first operating mode, the second operating mode, the third operating mode and the fourth operating mode of the forward converter of FIG. 15 .

Please refer to FIG. 16A . In the first operation mode, the active power switch element Q1 is turned on, the first auxiliary diode Da4 is turned off, the second auxiliary diode Da5 is turned off, the flywheel diode D1 is turned off, and the flywheel diode D2 is turned on. When the active power switch element Q1 is in the on state, the input voltage _Vi and the auxiliary capacitor Ca supply power to the primary winding N1 of the voltage conversion device 20_6, and the inductive voltage of the secondary winding N2 of the voltage conversion device 20_6 charges the output capacitor C1. At this time, the energy storage inductor L1 stores energy, and the auxiliary capacitor Ca is in a discharge state. This operation mode continues until the active power switch element Q1 is turned off and enters the second operation mode.

Please refer to FIG. 16B , in the second operation mode, the active power switch element Q1 is turned off, the first auxiliary diode Da4 is turned on, the second auxiliary diode Da5 is turned on, and the flywheel diodes D1 and D2 are turned off. After the active power switch element Q1 is turned off, since the first auxiliary winding La4 is coupled with the primary winding N1 and the secondary winding N2, the energy stored in the primary winding N1 and the secondary winding N2 can be demagnetized through the path formed by the first auxiliary diode Da4 to the auxiliary capacitor Ca, and the auxiliary capacitor Ca can be charged to establish the compensation voltage V _ca . Since the second auxiliary winding La5 and the energy storage inductor L1 are coupled to each other, the energy stored in the energy storage inductor L1 can charge the auxiliary capacitor Ca through the path formed by the second auxiliary winding La5 through the second auxiliary diode Da5 to the auxiliary capacitor Ca to establish the compensation voltage _Vca . Therefore, the compensation voltage _Vca rises. This operation mode continues until the compensation voltage _Vca is equal to the third mapping voltage, and enters the third operation mode. The third mapping voltage is the output voltage _Vo mapped to the equivalent voltage on the second auxiliary winding La5 side according to the turns ratio of the energy storage inductor L1 and the second auxiliary winding La5.

Please refer to FIG. 16C , in the third operation mode, the active power switch element Q1 is turned off, the first auxiliary diode Da4 is turned on, the second auxiliary diode Da5 is turned off, the flywheel diode D1 is turned on, and the flywheel diode D2 is turned off. The first auxiliary winding La4 continues to be demagnetized through the path formed by the first auxiliary diode Da4 to the auxiliary capacitor Ca, and continues to charge the auxiliary capacitor Ca to establish the compensation voltage V _ca . The energy stored in the energy storage inductor L1 is released through the flywheel diode D1 to charge the output capacitor C1. This operation mode continues until the energy of the first auxiliary winding La4 and the energy storage inductor L1 is completely released, and then enters the fourth operation mode.

Please refer to Figure 16D. After the first auxiliary winding La4 and the energy storage inductor L1 are fully released in the third operation mode, the current of the auxiliary capacitor Ca and the energy storage inductor L1 drops to zero, the first auxiliary diode Da4, the second auxiliary diode Da5 and the flywheel diodes D1 and D2 all enter the cut-off state, and the active power switch element Q1 remains in the cut-off state. The energy stored in the output capacitor C1 can continue to provide current to the load. When the active power switch element Q1 is triggered to conduct again, the energy stored in the auxiliary capacitor Ca is used to charge the output capacitor C1, that is, the forward converter 1_6 returns to the first operation mode again. In particular, in the application where the forward converter of this embodiment is designed to operate in the continuous current mode, the fourth operation mode may not exist, that is, the first operation mode may be directly returned to after the third operation mode.

From the description of the above-mentioned multiple embodiments, it can be seen that the auxiliary device of the forward converter of the present invention can be summarized into the following multiple embodiments. In the first embodiment, the auxiliary device of the forward converter includes an auxiliary capacitor. In the second embodiment, the auxiliary device includes an auxiliary capacitor, an auxiliary diode and an auxiliary winding, wherein the anode end of the auxiliary diode is connected to the first end of the auxiliary capacitor, the auxiliary winding is coupled to the primary winding and the secondary winding, and one end of the auxiliary winding is connected to the cathode end of the auxiliary diode, and the other end of the auxiliary winding is connected to the second end of the auxiliary capacitor. In a third implementation, the voltage conversion device further includes an energy storage inductor for outputting the output voltage, and the auxiliary device includes an auxiliary capacitor, an auxiliary diode and an auxiliary winding, wherein the anode end of the auxiliary diode is connected to the first end of the auxiliary capacitor, the auxiliary winding is coupled to the energy storage inductor, and one end of the auxiliary winding is connected to the cathode end of the auxiliary diode, and the other end of the auxiliary winding is connected to the second end of the auxiliary capacitor. In the fourth embodiment, the voltage conversion device further includes an energy storage inductor for outputting the output voltage, the auxiliary device includes an auxiliary capacitor, a first auxiliary diode, a second auxiliary diode, a first auxiliary winding and a second auxiliary winding, the anode end of the first auxiliary diode is connected to the first end of the auxiliary capacitor, the first auxiliary winding is coupled to the primary winding and the secondary winding, and the first auxiliary winding is connected to the secondary winding. One end of the first auxiliary winding is connected to the cathode end of the first auxiliary diode, and the other end of the first auxiliary winding is connected to the second end of the auxiliary capacitor, the anode end of the second auxiliary diode is connected to the first end of the auxiliary capacitor, the second auxiliary winding is coupled to the energy storage inductor, one end of the second auxiliary winding is connected to the cathode end of the second auxiliary diode, and the other end of the second auxiliary winding is connected to the second end of the auxiliary capacitor.

The auxiliary device of the above-mentioned embodiment can be connected to the primary winding or the secondary winding, wherein the primary winding is particularly suitable for the second to fourth embodiments. It should also be noted that by connecting the auxiliary device to the secondary winding, a diode can be omitted between the secondary winding and the energy storage inductor of the voltage conversion device of the forward converter, and compared with the configuration in which the auxiliary device is connected to the primary winding, a simpler circuit structure can be provided.

Please refer to FIG. 17, which exemplarily presents the waveform diagram of the voltage at the AC input end, the current at the AC input end, and the secondary side current of the forward power factor corrector of the forward converter of an embodiment of the present invention. As shown in FIG. 17, the voltage _Vs at the AC input end matches the waveform of the current Is at the AC input end, and has a low harmonic rate. In addition, according to the demagnetization interval d1 of the secondary side current I2, it can be known that the forward power factor corrector can effectively demagnetize.

其中V_o為輸出電壓，V_s為交流輸入的電壓，如圖2所示，D為開關責任週期。 Please refer to FIG. 18, which exemplarily presents a relationship diagram between the output voltage and the switch duty cycle of a forward power factor corrector according to an embodiment of the present invention. The relationship between the output voltage and the switch duty cycle can be presented by the following formula 1:

Where V _o is the output voltage, V _s is the AC input voltage, as shown in Figure 2, and D is the switch duty cycle.

In summary, the forward converter according to one or more embodiments of the present invention can have the advantages of high conversion efficiency, satisfying the transformer winding demagnetization requirements, providing compensation voltage, small size and light weight through the setting of auxiliary devices, and can not add additional complex and high-cost mechanisms. The forward power factor corrector disclosed in this case, which includes the forward converter mentioned above, can reduce the current blind area through the compensation voltage of the auxiliary device, and can achieve the effect of high power factor and low harmonic rate in addition to the above advantages.

Although the present invention is disclosed as above by the aforementioned embodiments, it is not intended to limit the present invention. Any changes and modifications made within the spirit and scope of the present invention are within the scope of patent protection of the present invention. Please refer to the attached patent application for the scope of protection defined by the present invention.

1: Forward converter

10: Switch

201: Primary side winding group

202: Secondary side winding group

20: Voltage conversion device

30: Auxiliary devices

Claims (14)

A forward converter comprises: A voltage conversion device, comprising a transformer, the transformer having a primary winding and a secondary winding, and used to convert an input voltage into an output voltage; A switch, connected to the voltage conversion device, and switched so that the voltage conversion device receives or does not receive the input voltage; and An auxiliary device, connected to the voltage conversion device, storing the electric energy released by the voltage conversion device and generating a compensation voltage when the switch is turned off, and providing the compensation voltage when the switch is turned on, wherein the compensation voltage has the same polarity as the input voltage. A forward converter as described in claim 1, wherein the auxiliary device includes an auxiliary capacitor. The forward converter as described in claim 2, wherein the auxiliary device further comprises: an auxiliary diode, the anode end of the auxiliary diode is connected to the first end of the auxiliary capacitor; and an auxiliary winding coupled to the primary winding and the secondary winding, wherein one end of the auxiliary winding is connected to the cathode end of the auxiliary diode, and the other end of the auxiliary winding is connected to the second end of the auxiliary capacitor. A forward converter as described in claim 3, wherein the voltage conversion device further includes an energy storage inductor for outputting the output voltage, the auxiliary diode is a first auxiliary diode, the auxiliary winding is a first auxiliary winding, and the auxiliary device further includes: a second auxiliary diode, the anode end of the second auxiliary diode is connected to the first end of the auxiliary capacitor; and a second auxiliary winding, coupled to the energy storage inductor, wherein one end of the second auxiliary winding is connected to the cathode end of the second auxiliary diode, and the other end of the second auxiliary winding is connected to the second end of the auxiliary capacitor. A forward converter as described in claim 2, wherein the voltage conversion device further comprises an energy storage inductor for outputting the output voltage, and the auxiliary device further comprises: an auxiliary diode, the anode end of the auxiliary diode is connected to the first end of the auxiliary capacitor; and an auxiliary winding coupled to the energy storage inductor, wherein one end of the auxiliary winding is connected to the cathode end of the auxiliary diode, and the other end of the auxiliary winding is connected to the second end of the auxiliary capacitor. A forward converter as described in claim 1, wherein the voltage conversion device further includes an energy storage inductor, a first end of the energy storage inductor is used to output the output voltage, one end of the auxiliary device is connected to the secondary winding, and the other end of the auxiliary device is connected to the second end of the energy storage inductor. A forward converter as described in claim 6, wherein the auxiliary device comprises: an auxiliary capacitor, a first end of the auxiliary capacitor is connected to the secondary winding, and a second end of the auxiliary capacitor is connected to the second end of the energy storage inductor. The forward converter as described in claim 7, wherein the auxiliary device further comprises: an auxiliary diode, the anode end of the auxiliary diode is connected to the first end of the auxiliary capacitor; and an auxiliary winding coupled to the energy storage inductor, wherein one end of the auxiliary winding is connected to the cathode end of the auxiliary diode, and the other end of the auxiliary winding is connected to the second end of the auxiliary capacitor. The forward converter as described in claim 7, wherein the auxiliary device further comprises: an auxiliary diode, the anode end of the auxiliary diode is connected to the first end of the auxiliary capacitor; and an auxiliary winding coupled to the primary winding and the secondary winding, wherein one end of the auxiliary winding is connected to the cathode end of the auxiliary diode, and the other end of the auxiliary winding is connected to the second end of the auxiliary capacitor. A forward converter as described in claim 9, wherein the auxiliary diode is a first auxiliary diode, the auxiliary winding is a first auxiliary winding, and the auxiliary device further comprises: a second auxiliary diode, the anode end of the second auxiliary diode is connected to the first end of the auxiliary capacitor; and a second auxiliary winding, coupled to the energy storage inductor, wherein one end of the second auxiliary winding is connected to the cathode end of the second auxiliary diode, and the other end of the second auxiliary winding is connected to the second end of the auxiliary capacitor. A forward converter as described in claim 1, wherein one end of the auxiliary device is used to receive the input voltage, and the other end of the auxiliary device is connected to the primary winding. A forward converter as described in claim 11, wherein the auxiliary device comprises: an auxiliary capacitor, a first end of the auxiliary capacitor is used to receive the input voltage, and a second end of the auxiliary capacitor is connected to the primary winding; an auxiliary diode, an anode end of the auxiliary diode is connected to the first end of the auxiliary capacitor; and an auxiliary winding coupled to the primary winding and the secondary winding, wherein one end of the auxiliary winding is connected to the cathode end of the auxiliary diode, and the other end of the auxiliary winding is connected to the second end of the auxiliary capacitor. A forward converter as described in claim 12, wherein the voltage conversion device further includes an energy storage inductor for outputting the output voltage, the auxiliary diode is a first auxiliary diode, the auxiliary winding is a first auxiliary winding, and the auxiliary device further includes: a second auxiliary diode, the anode end of the second auxiliary diode is connected to the first end of the auxiliary capacitor; and a second auxiliary winding, coupled to the energy storage inductor, wherein one end of the second auxiliary winding is connected to the cathode end of the second auxiliary diode, and the other end of the second auxiliary winding is connected to the second end of the auxiliary capacitor. A forward power factor corrector comprises: A forward converter as described in any one of claims 1 to 13; and A rectifying device connected to the forward converter for receiving and rectifying a power source to generate the input voltage.

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