KR101937013B1 - Power factor correction converter - Google Patents

Abstract

An isolated voltage source power factor improving converter capable of maximizing efficiency without using a high voltage switch is disclosed. The power factor improving converter includes a transformer, a front end circuit used at the front end of the primary side of the transformer, and a rear end circuit used at the rear end side of the primary side of the transformer. Here, the front-end circuit does not include an inductor and the rear-end circuit uses an inductor.

Description

[0001] POWER FACTOR CORRECTION CONVERTER [0002]

The present invention relates to a power factor improving converter.

Conventional chargers mainly use isolated DC / DC converters for power factor improvement. These isolated DC / DC converters are designed to accommodate a wide range of battery voltages, but they are designed to be charged even at the peak of the battery, resulting in higher transformer secondary winding ratios, which increases switch current stress and secondary rectifier voltage stress. As a result, the maximum efficiency of the isolated DC / DC converter does not exceed 92% in practice considering power factor improvement.

To improve this, an isolated boost converter appeared. However, the isolation type boost converter requires a high voltage switch due to the increase of the switch voltage stress due to leakage of the transformer. In order to suppress the voltage surge due to leakage of the transformer, a snubber circuit must be added, It is inevitable to deteriorate.

KR 10-1675846 B

The present invention provides an isolated voltage source power factor improving converter capable of maximizing the efficiency without using a high withstand voltage switch.

In order to achieve the above object, a power factor improving converter according to an embodiment of the present invention includes a transformer; A front end circuit used at the front end of the primary side of the transformer; And a rear end circuit used at a rear end of the primary side of the transformer. Here, the front-end circuit does not include an inductor and the rear-end circuit uses an inductor.

According to another aspect of the present invention, a power factor improving converter includes a transformer; A front end circuit used at the front end of the primary side of the transformer; And a rear end circuit used at a rear end of the primary side of the transformer. The front end circuit includes at least one first switch and the rear end circuit includes at least one second switch. Here, the first switch and the second switch each have a back-to-back structure in which switches are serially connected in series, and the front-end circuit does not use a bridge diode.

A power factor improving converter according to another embodiment of the present invention includes a transformer; A primary side circuit of the transformer; And a secondary circuit of the transformer. Here, the primary circuit has at least one first switch and the secondary circuit has at least one second switch. The first switch has a duty ratio and is controlled at a fixed frequency, and the second switch controls the operation of the transformer.

In a three-phase power factor improving converter according to another embodiment of the present invention, each phase includes a transformer; A front end circuit used at the front end of the primary side of the transformer; And a rear end circuit used at a rear end of the primary side of the transformer. Here, the front-end circuit does not include an inductor and the rear-end circuit uses an inductor.

The power factor improving converter according to the present invention is implemented by a circuit in which the inductor is positioned at the rear end of the primary side without being positioned at the front side of the primary side of the transformer. As a result, a high-voltage switch is not required and a general switch can be used, and the efficiency of the converter can be improved because a snubber circuit is not required.

In addition, the primary side switch of the transformer can be implemented as a back-to-back (B2B) structure, so that the bridge diode can be omitted from the primary side.

Further, in the case of a three-phase structure, a circuit structure is used in which the three-phase uses the secondary circuit of the transformer in common and adds the output capacitor and the load only to a specific phase. As a result, the size of the converter is reduced and the use of film capacitors as output capacitors is possible.

1 is a circuit diagram showing an isolated voltage source PFC converter according to a first embodiment of the present invention.
2 is a circuit diagram illustrating a circuit for controlling a switch according to an embodiment of the present invention.
FIG. 3 is a diagram illustrating operation waveforms during a positive half period of an input voltage according to an embodiment of the present invention.
4 is a diagram showing the operation of the PFC converter according to the waveform of FIG.
FIG. 5 is a diagram illustrating an operation waveform during a negative half period of an input voltage according to an embodiment of the present invention.
6 is a diagram showing the operation of the PFC converter according to the waveform of FIG.
7 is a graph showing input current peak values and AC current waveforms when WAVESHAPER is absent and when WAVESHAPER is absent.
8 is a graph showing the input current, the inductor current, and the output voltage waveform of the PFC converter as simulation results.
FIG. 9 is a graph showing a switching waveform (a) at a half period of the input voltage and a switching waveform (b) at a negative half period as a simulation result.
10 is a circuit diagram showing an isolated voltage source PFC converter according to a second embodiment of the present invention.
11 is a circuit diagram showing an isolated voltage source PFC converter according to a third embodiment of the present invention.
Fig. 12 is a diagram showing the waveform of Fig. 11. Fig.

As used herein, the singular forms "a", "an" and "the" include plural referents unless the context clearly dictates otherwise. In this specification, the terms "comprising ", or" comprising "and the like should not be construed as necessarily including the various elements or steps described in the specification, Or may be further comprised of additional components or steps. Also, the terms "part," " module, "and the like described in the specification mean units for processing at least one function or operation, which may be implemented in hardware or software or a combination of hardware and software .

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an isolated voltage source power factor correction (PFC) converter, for example, a PFC converter for an electric vehicle, and can realize high efficiency without using a high voltage switch.

According to one embodiment, the PFC converter of the present invention can use a structure in which the inductor is positioned at the rear end of the primary side without being positioned at the front end of the primary side of the transformer.

If the inductor is placed at the front of the primary side of the transformer, the switch voltage stress is increased due to the leakage of the transformer, and a high voltage switch is required. In order to suppress the voltage surge due to leakage of the transformer, a snubber circuit High efficiency can not be realized.

On the other hand, since the PFC converter of the present invention uses an inverter placed at the rear end of the primary side of a transformer, a general switch can be used instead of a high-voltage switch, and a high efficiency can be realized because a snubber circuit is not required.

According to another embodiment, the PFC converter of the present invention may be implemented as a back-to-back (B2B) structure of the primary side switch of the transformer, so that the bridge diode may not be used on the primary side.

Hereinafter, various embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a circuit diagram showing an isolated voltage source PFC converter according to a first embodiment of the present invention, and FIG. 2 is a circuit diagram illustrating a circuit for controlling a switch according to an embodiment of the present invention.

Referring to FIG. 1, the isolated voltage source PFC converter of the present embodiment may include a front end circuit 100, a transformer 102, a rear end circuit 104, a transformer control unit 110, and an output end 112.

The front-end circuit 100 refers to circuits located at the front end (near the voltage source) of the primary side of the transformer 102 and may include a capacitor C and switches M1 and M2. A voltage is used as the input source of the front-end circuit 100.

The capacitor C is connected to the voltage source and is connected in parallel to the switches M1 and M2.

The switch M1 is connected to the node n1, that is, to one end of the capacitor C, the switch M2 is connected in series with the switch M1 on the basis of the node n1, And may be connected in parallel with the switch M1.

According to one embodiment, the switches Ml and M2 may operate at a fixed frequency with a duty ratio, for example, each with a 50% duty ratio. As a result, the circuits located in the flow path of the input current i _ac can operate at high frequencies, and thus the high-frequency transformer can be used as the transformer 102.

Also, the switches M1 and M2 can operate complementarily. For example, switch M2 may be off when switch M1 is on, and switch M2 may be on when switch M1 is off.

1, each of the switches M1 and M2 may be implemented as a back-to-back (B2B) structure. As a result, a rectifier May not be used. That is, the transformer 102 may have a voltage-fed input structure in which only the capacitor C is present at the front ends of the primary-side switches M 1 and M 2 of the transformer 102.

One terminal of the primary side of the transformer 102 is connected to the node n2 between the switches M1 and M2, and the other terminal of the primary side can be connected to the inductor Lp. That is, the inductor Lp may be located at the rear end of the primary side of the transformer 102 (far from the voltage source).

According to one embodiment, the transformer 102 may be controlled by the transformer control 110.

The transformer control unit 110 is connected to the secondary side of the transformer 102 and may include a switch M5 having a back-to-back (B2B) structure as shown in FIG. Here, the switch M5 is connected to the front end of the full bridge diode.

The PFC converter of the present invention uses a structure for controlling the transformer 102 with the switch M5 in particular. As a result, the voltage on the primary side of the transformer 102 changes as the switch M5 is turned on / off. Thus, the current flowing in the primary side of the transformer 102 flows into a discontinuous mode (DCM). In this case, it is not necessary to control the harmonic of the input current, i.e., no additional circuit for controlling the harmonic is required.

Therefore, the switch control unit for controlling the switch M5 may include only the voltage controller 200 and the PWM circuit 204 for controlling charging without a circuit for controlling harmonics, as shown in Fig. 2A.

The PWM circuit 204 converts the output of the voltage controller 200 into a PWM signal and provides it to the switch M5 so that the switch M5 switches to a specific frequency.

According to one embodiment, the switch control may further include a wave adjuster 202. [ The waveform adjuster 202 adjusts the waveform of the output of the voltage controller 200 to realize the input current as an ideal sinusoidal wave from the input voltage and the battery voltage information. As a result, a high power factor of 0.96 or more can be realized.

The rear stage circuit 104 is located at the rear end of the primary side of the transformer 102 and may include an inductor Lp and a plurality of switches M3 and M4.

One end of the inductor Lp is connected to the other terminal of the primary side of the transformer 102 and the other end is connected to the node n3 between the switches M3 and M4.

The switches M3 and M4 may operate at a fixed frequency with a duty ratio, for example, each with a 50% duty ratio.

According to one embodiment, the switches M3 and M4 may each have a Back-to-Back (B2B) structure and operate complementarily. For example, switch M4 may be off when switch M3 is on, and switch M4 may be on when switch M3 is off.

According to one embodiment, the switches M3 and M4 may operate complementarily with the switches Ml and M2 as shown in Figure 2 (B). And can be performed by the inverter 212 which is this complementary operation.

The output stage 112 may comprise a full bridge diode, an output capacitor (e.g., a battery), and a load R ₀ .

The full bridge diode is composed of diodes D1 to D4 and can perform a rectifying function. Of course, half bridge diodes may be used instead of full bridge diodes.

The output capacitor and the load (R ₀ ) are connected in parallel to the full bridge diode.

In summary, the PFC converter of the present embodiment is implemented such that the inductor Lp is positioned at the rear end of the primary side of the transformer 102 and only the capacitor C is present at the front end of the switches M1 and M2. As a result, it is possible to use a general switch, not a high-voltage switch, and achieve high efficiency.

Meanwhile, although not shown, a DC-coupling capacitor may be added in series with the transformer 102 to remove the DC bias component of the voltage applied to the transformer 102. In this case, saturation of the transformer 102 can be prevented.

Hereinafter, the operation of the PFC converter having such a structure will be described with reference to the accompanying drawings.

FIG. 3 is a view showing an operation waveform during a positive half period of an input voltage according to an embodiment of the present invention, and FIG. 4 is a diagram illustrating operation of a PFC converter according to the waveform of FIG. FIG. 5 is a view showing an operation waveform during a negative half period of an input voltage according to an embodiment of the present invention, and FIG. 6 is a diagram illustrating an operation of the PFC converter according to the waveform of FIG. 7 is a graph showing input current peak values and AC current waveforms when WAVESHAPER is absent and when WAVESHAPER is absent.

First, the operation of the positive half of the input voltage will be described with reference to FIGS. 3 and 4. FIG.

Mode ₁ (t ₀ ~ t 1) at the, in the switch t ₀ point (M1 and M3) is turned on and the, switch (M2 and M4) maintains the OFF state. In addition, the switch M5 is turned on simultaneously with the activation timing of the switches M1 and M3.

As a result, the inductor current i _p flows via the switch Ml, the transformer 102 and the switch M3. At this time, the primary side voltage Vp of the transformer 102 becomes zero and the inductor current i _p has a slope of (V _in / L _r ) as shown in Equation 1 (input current) . Further, since the diodes D1 to D4 are deactivated, only discharge operation from the output capacitor to the load occurs.

Mode 20,000 (t ₁ ~ t ₂₎ in, t in the _first time switch (M1 and M3) on the switch (M5), while maintaining the state is turned off. As a result, the diodes (D1 and D3) 1-side voltage (Vp) of the active transformer _{(102) (V 0 / n} ) is applied. Where (V ₀ / n) is the voltage greater than the input voltage and n is the turns ratio. Thus, the inductor current (i _p ) decreases linearly with a slope of (V _in- V ₀ / n) / L _r , which is expressed in the input current of equation (2). At this time, the output capacitor (battery) is charged and discharged simultaneously.

In mode 3 (t ₂ to t ₃ ), mode 3 is started and the operation of the converter is stopped when the input current (i _in ) falls to 0 _in mode 2.

Mode ₄ (t ₃ ~ t 4) from, the switches at the time t ₃ (M2 and M4) is turned on, is turned on and the switches (M1 and M3) is turned off. In addition, the switch M5 is turned on simultaneously with the activation timing of the switches M2 and M4.

As a result, the inductor current i _p flows via the switch M4, the transformer 102 and the switch M2. At this time, the primary side voltage Vp of the transformer 102 becomes zero and the inductor current i _p linearly decreases with a slope of (V _in / L _r ) as shown in Equation (1). Further, since the diodes D1 to D4 are inactivated, no current flows through the battery.

Mode ₅ (t ₄ ~ t 5) only in, the switch t ₄ at the time switch (M5) and (M2 and M4) maintains the on state is turned off. As a result, diodes D2 and D4 are activated and - (V ₀ / n) is applied to the primary side voltage Vp of the transformer 102. Where (V ₀ / n) is a voltage greater than the input voltage. Therefore, the inductor current (i _p ) linearly increases with a slope of (V _in -V ₀ / n) / L _r , which is expressed in the input current of Equation (2). At this time, the output capacitor, that is, the battery, simultaneously performs the charging operation and the discharging operation.

In mode 6 (t ₅ to t ₆ ), mode 6 starts when the input current (i _in ) rises to zero _in mode 5 and the operation of the converter is stopped.

Next, the operation of the input voltage during the negative half period will be described with reference to FIGS. 5 and 6. FIG.

Mode ₁ (t ₀ ~ t 1) at the, in the switch t ₀ point (M1 and M3) is turned on and the, switch (M2 and M4) maintains the OFF state. In addition, the switch M5 is turned on simultaneously with the activation timing of the switches M1 and M3.

As a result, the inductor current i _p flows via the switch M3, the transformer 102 and the switch M1. At this time, the primary side voltage Vp of the transformer 102 becomes zero and the inductor current i _p is linearly proportional to the slope of (V _in / L _r ) as shown in Equation 1 (input current) . Further, since the diodes D1 to D4 are deactivated, only discharge operation from the output capacitor to the load occurs.

Mode 20,000 (t ₁ ~ t ₂₎ in, t in the _first time switch (M1 and M3) on the switch (M5), while maintaining the state is turned off. As a result, diodes D2 and D4 are activated and - (V ₀ / n) is applied to the primary side voltage Vp of the transformer 102. Where (V ₀ / n) is a voltage greater than the input voltage. Thus, the inductor current (i _p ) decreases linearly with a slope of (V _in- V ₀ / n) / L _r , which is expressed in the input current of equation (2). At this time, the output capacitor (battery) is charged and discharged simultaneously.

In mode 3 (t ₂ to t ₃ ), mode 3 starts when the input current (i _in ) rises to 0 _in mode 2 and the operation of the converter is stopped.

Mode ₄ (t ₃ ~ t 4) from, the switches at the time t ₃ (M2 and M4) is turned on, is turned on and the switches (M1 and M3) is turned off. In addition, the switch M5 is turned on simultaneously with the activation timing of the switches M2 and M4.

As a result, the inductor current i _p flows via the switch M2, the transformer 102 and the switch M4. At this time, the primary side voltage Vp of the transformer 102 becomes zero and the inductor current i _p linearly decreases with a slope of (V _in / L _r ) as shown in Equation (1). Further, since the diodes D1 to D4 are inactivated, no current flows through the battery.

Mode ₅ (t ₄ ~ t 5) only in, the switch t ₄ at the time switch (M5) and (M2 and M4) maintains the on state is turned off. As a result, the diodes (D1 and D3) 1-side voltage (Vp) of the active transformer _{(102) (V 0 / n} ) is applied. Where (V ₀ / n) is a voltage greater than the input voltage. Therefore, the inductor current (i _p ) linearly increases with a slope of (V _in -V ₀ / n) / L _r , which is expressed in the input current of Equation (2). At this time, the output capacitor, that is, the battery, simultaneously performs the charging operation and the discharging operation.

In mode 6 (t ₅ to t ₆ ), mode 6 starts when the input current (i _in ) rises to zero _in mode 5 and the operation of the converter is stopped.

Next, let's look at the waveform of the AC current when there is no WAVESHAPER and when it is present.

In the absence of the waveform adjuster, the peak value of the input current i _in follows the input voltage as shown in FIG. 7 (a), but the AC current i _ac is distorted.

On the other hand, when the waveform adjuster is used, the peak value of the input current i _in is distorted as shown in FIG. 7 (b), but the AC current i _ac can form a sinusoidal wave without distortion. The duty ratio for forming the input current i _in as an ideal sinusoidal wave is expressed by Equation (3).

As shown in Equation (3), the final duty ratio generated through PWM is represented by the product of the term D ₀ according to the load condition and the term Waveshaping using the input voltage and the battery voltage.

FIG. 8 is a graph showing input current, inductor current, and output voltage waveform of the PFC converter as simulation results. FIG. 9 is a graph showing the relationship between the switching waveform (a) and the half- And a switching waveform (b). Here, L _{r was set} to 25 μH, and the turns ratio of the transformer 102 was set to 1: 1.1. As shown in Figs. 8 and 9, it can be confirmed that the input current (i _in ) has an ideal sinusoidal wave.

10 is a circuit diagram showing an isolated voltage source PFC converter according to a second embodiment of the present invention.

10, the PFC converter of the present embodiment includes a front end circuit 1000, a transformer 1002, a rear end circuit 1004, and a transformer control unit and an output stage 1010.

Unlike in the first embodiment, the trailing circuit 1004 is composed of capacitors C1 and C2, not switches. Here, the capacitors C1 and C2 are connected in parallel to one end of the inductor Lp, that is, the node n3.

In addition, the output stage uses a half bridge diode rather than a full bridge diode.

The remaining circuits are similar to those in the first embodiment, and a description thereof will be omitted.

On the other hand, the duty ratio for forming the input current i _in as an ideal sinusoidal wave is expressed by Equation (4).

FIG. 11 is a circuit diagram showing an isolated voltage source PFC converter according to a third embodiment of the present invention, and FIG. 12 is a diagram showing the waveform of FIG.

The primary circuit structure of each phase transformer is the same as in Fig. However, in the secondary circuit structure of the transformer, the output stages 1210, 1212, and 1214 are interconnected. That is, the secondary circuits of the phases are commonly used.

Specifically, the output terminals of the full bridge diodes are interconnected. In this case, the output capacitor (battery, _C0 ) and the load ( _Ro ) can be commonly used. That is, the three-phase of the and only the output of the particular full-bridge diode on the formation of the output capacitor (battery, C _O) and a load (R _O), the output capacitor (battery, C _O) output terminal of the full-bridge diode of the other phase and the load (R _O ) is not formed separately but uses a specific phase output capacitor (battery, C _O ) and load (R _O ).

Of course, the output stages can be formed independently for each phase, but the size of the PFC converter can not but be increased.

On the other hand, the use of the secondary circuit of the transformer of respective phases in common, the ripple (Ripple) the frequency of the output capacitor (C _O) is the line frequency of six times can be designed smaller output capacitor (C _O). Therefore, since the output capacitor C _O does not need to be large, the use of the film capacitor becomes possible, and as a result, the lifetime of the PFC converter can be increased, so that the PFC converter can be suitably used for an automobile high capacity charger.

On the other hand, in the simulation, the output capacitor (C _O ) was used at 50 kV and the capacity was 11 kW, and the resultant waveform is shown in FIG.

On the other hand, the components of the above-described embodiment can be easily grasped from a process viewpoint. That is, each component can be identified as a respective process. Further, the process of the above-described embodiment can be easily grasped from the viewpoint of the components of the apparatus.

It will be apparent to those skilled in the art that various modifications, additions and substitutions are possible, without departing from the spirit and scope of the invention as defined by the appended claims. Should be regarded as belonging to the following claims.

100: Shear circuit 102: Transformer
104: rear stage circuit 110: transformer control section
112: output stage 200: voltage controller
202: Waveform controller 204: PWM circuit
210: Fixed frequency duty generator

Claims (14)

Transformers;
A front end circuit used at the front end of the primary side of the transformer; And
And a rear stage circuit used at a rear stage of the primary side of the transformer,
Wherein the front-
A capacitor; And
And a first switch and a second switch connected in parallel with the capacitor,
The above-
An inductor connected to the other terminal of the primary side of the transformer; And
A third switch, and a fourth switch,
Wherein the front stage circuit does not include an inductor and the rear stage circuit uses the inductor and a node between the first and second switches is connected to a terminal of the primary side of the transformer, And the first switch or the second switch has a back-to-back structure in which the switches are connected in series, and the front-end circuit does not use a rectifier composed of a bridge diode, A node between the third switch and the fourth switch is connected to one end of the inductor, the first switch and the third switch operate in the same manner, and the second switch and the fourth switch operate in the same manner , And the third switch or the fourth switch has a back-to-back structure in which switches are connected in series Power Factor Correction Converter. delete delete delete The method according to claim 1,
A transformer control unit connected to a secondary side of the transformer;
And a bridge diode coupled to the transformer control,
Wherein the transformer control unit controls the operation of the transformer as a fifth switch, the fifth switch operates at a fixed frequency, and the current flowing in the primary side of the transformer as the fifth switch operates at a fixed frequency is in a discontinuous mode Discontinuous mode, DCM). 6. The method of claim 5,
Further comprising a switch control unit controlling the transformer control unit and having a voltage controller and a PWM circuit,
Wherein the PWM circuit converts an output of the voltage controller into a PWM signal and outputs the PWM signal as a control signal of the fifth switch. 7. The apparatus of claim 6,
Further comprising a wave adjuster (WAVESHAPER)
Wherein the waveform adjuster adjusts the waveform of the output of the voltage controller. delete delete delete delete delete delete delete

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