KR100674713B1 - Power factor correction compensating circuit for low loss - Google Patents

Abstract

The present invention relates to a low loss power factor correction circuit, and by adding a saturable core, a spike reduction unit, and a turn-off loss reduction unit, not only can reduce the turn-on and turn-off loss of the switching semiconductor element, but also the loss of the diode. In addition, the voltage spike caused by the leakage inductance of the inductor can be reduced to suppress serious circuit damage.

A low loss power factor correction circuit according to the present invention includes: a rectifier for rectifying an input AC power and outputting a DC voltage according thereto; A first inductor having one end connected to an output terminal of the rectifier; A first switching element connected between the output end of the rectifier and the other end of the first inductor; A second inductor having one end connected to a first node to which the first inductor and the first switching element are connected; A first capacitor connected between a second node connected to the other end of the second inductor and a ground terminal; A second switching element connected between the second node and a third node at which a DC voltage is output; And a second capacitor connected between the third node and a ground terminal.

Power Factor Correction Circuit, Saturated Core, Voltage Spikes, Turn-On and Turn-Off Loss

Description

Low loss power factor correction circuit {POWER FACTOR CORRECTION COMPENSATING CIRCUIT FOR LOW LOSS}

1 is a circuit diagram of a low loss power factor correction circuit according to the prior art;

2 is a diagram illustrating the reverse recovery characteristics of a low loss power factor correction circuit according to the related art.

3 is a diagram illustrating a voltage spike of a low loss power factor correction circuit according to the related art.

4 is a diagram showing the turn-on and turn-off loss of the conventional low loss power factor correction circuit;

5 is a circuit diagram of a low loss power factor correction circuit according to the present invention.

<Description of Major Symbols in Drawing>

500: power factor correction circuit 501: rectifier

501a: bridge diode 501b: third capacitor

502: first inductor 503: first switching element

504: second switching element 505: second capacitor

506: second inductor 507: first capacitor

508: spike reduction unit 508a: diode

508b: Zener Diode 509: Turn-Off Loss Reduction Section

509a: fourth capacitor 509b: fourth switching element

509c: fifth switching element 509d: resistor

510: third switching element a, b, c, d: first, second, third, fourth node

The present invention relates to a low loss power factor correction circuit, and by adding a saturable core, a spike reduction unit, and a turn-off loss reduction unit, not only can reduce the turn-on and turn-off loss of the switching semiconductor element, but also the loss of the diode. In addition, the present invention relates to a low loss power factor correction circuit capable of reducing voltage spikes caused by leakage inductance of an inductor to prevent serious circuit damage.

In the power calculation of the DC circuit, only the voltage and the current need to be multiplied. In the power calculation of the AC circuit, except for the case where the current and the voltage are in phase, the effective value of the voltage and the current must be multiplied by the coefficient of cosθ. This coefficient is called the power factor and is commonly referred to as p.f. Therefore, the higher the current and the voltage in phase, that is, the higher the power factor, the higher the efficiency of the AC circuit.

In general, DC voltage is widely used not only in the industry but also in the home, and thus, a rectifying circuit for converting an AC voltage into a DC voltage is widely used. The most commonly used among these rectifier circuits is a capacitor input rectifier circuit, which has an advantage of simple phase.

However, the condenser input type rectifier circuit has a disadvantage in that the input current flows only in the peak portion of the commercial AC voltage, so that the power factor pulsates and is very bad.

In addition, since various electrical devices have a combination of resistance, inductance, and capacitance components, the phase of the current is different from the commercial AC voltage, which causes the output DC voltage to be distorted.

In addition, in the current industrial field, since a predetermined electric device is controlled through a high speed switching method, a lot of noise is generated due to the high speed switching, and the electric noises which are connected to the same power supply line adversely affect each other due to the generated noise. It may be.

Therefore, current industrial electric devices are designed to have a high in-phase input power factor in order to minimize the adverse effect on the commercial AC power supply due to the current flowing in the electric device itself.

For example, by adding a capacitance component to an AC power input line of an electrical device having an inductance component, the input currents applied to each of the inductor and the capacitor cancel each other out.

However, there is a limit to the performance that can be achieved only with such passive devices. In driving a converter system, switching the active devices such as transistors at high speed removes noise with smaller inductance and capacitance values and suppresses the voltage distortion to suppress the power factor. In order to improve the power consumption, various researches to make high power factor have been published.

In order to control the high power factor, the discontinuous current mode (DISCONTINUOUS CONDUCTION MODE; DCM), the boundary current mode (BCM), and the continuous current mode (CONTINUOUS CURRENT MODE; CCM), etc. There is this.

In particular, the continuous current mode method is known as the closest control method to obtain a unit power factor (UNITY POWER FACTOR), the continuous current mode method, peak current detection (PEAK CURRENT DETECTION) method, variable hysteresis (VARIABLE HYSTERESIS) ) Control method and average current control method.

These continuous current mode methods have the advantage of obtaining a high power factor, but among the above-mentioned continuous current methods, the peak current detection method generates current distortion and dead distortion of the current flowing to an external coil. And, the maximum duty cycle (MAXIMUM DUTY CYCLE) must be maintained at 50% or less, there is a problem that can not be accurate compensation, variable hysteresis control method is a variable frequency method according to the current sensing of the coil, when the input voltage is low Since the frequency must be infinitely increased in order to control the magnitude of the current flowing in the coil, there is a limit to the control of the frequency, and the average current control method has a problem in that a control method for realizing a unit power factor is very complicated.

1 shows a circuit diagram of a low loss power factor correction circuit 100 according to the prior art.

As shown in FIG. 1, the conventional low loss power factor correction circuit 100 includes a rectifying unit 101 for rectifying an input AC power and outputting a DC voltage according thereto, and one end of the rectifying unit 101 at an output terminal of the rectifying unit 101. The inductor 102 connected in series, the first switching device 103 connected between the output terminal of the rectifier 101 and the other end of the inductor 102, the inductor 102 and the first switching device 103 A second switching element 104 connected between the node M to be connected and the node N to which the DC voltage is output, and a first connected between the node N and the ground terminal at which the DC voltage is output. Capacitor 105 is included.

Here, the rectifier 101 includes a bridge diode 101a and a second capacitor 101b. The bridge diode 101a rectifies an input AC power, and the second capacitor 101b is the bridge diode ( It serves to smooth the power rectified from 101a).

The DC voltage (hereinafter referred to as DC voltage) input to the low loss power factor correction circuit 100 is applied to the first switching element 103 and the second switching element 104 through the inductor 102.

Here, as the inductor 102, a core having a characteristic of repeating increase and decrease of magnetic flux and reciprocating a predetermined section on a hysteresis curve is used, and a ferrite core is most commonly used.

A hysteresis curve is a curve showing the relationship between the strength of a magnetic field given by a magnetic material and the permeability caused by the magnetic material. The hysteresis curve is used to select a direction to change the strength of the magnetic field to a certain magnitude, and then periodically to the same magnitude in the opposite direction. The curve obtained when changed to.

In addition, a switching semiconductor device is used as the first switching device 103, and a transistor, a FET, an IGBT, etc. are used as the switching semiconductor device, but a FET is usually used the most, and as the second switching device 104. Diodes are used.

On the other hand, when the first switching device 103 is turned on and the second switching device 104 is turned off, energy of the input DC voltage is accumulated in the inductor 102, and the first switching device ( When 103 is turned off and the second switching element 104 is turned on, the energy accumulated in the inductor 102 is superimposed on the input DC voltage and rectified by the second switching element 104. Since it is smoothed by the capacitor 105 and output as the output DC voltage Vo, the magnitude of the output DC voltage Vo becomes larger than the magnitude of the input DC voltage.

In addition, when the first switching device 103 is turned on and the second switching device 104 is turned off, a reverse leakage current I _r is generated in the second switching device 104. The reverse leakage current I _r is generated due to a reverse recovery characteristic.

FIG. 2 is a diagram for explaining reverse recovery characteristics of a low loss power factor correction circuit according to the related art. As shown in FIG. 2, when a current I _F flows in a forward direction in a PN junction diode, the voltage V _F suddenly occurs. ), The forward current (I _F ) does not immediately go to zero due to accumulated minority carriers, but the reverse leakage current (I _r ) flows for a certain time, and then gradually the forward current (I _F ) Approaches 0, which is called reverse recovery. In this case, a time for generating the reverse leakage current I _r is called a reverse recovery time (Trr), and the longer the reverse recovery time, the higher the turn-on loss of the switching semiconductor element and the switching loss of the diode. .

However, in the conventional low loss power factor correction circuit as described above, due to the reverse leakage current generated by the reverse recovery characteristic of the diode, the turn-on loss of the switching semiconductor element and the switching loss of the diode are generated, resulting in a problem of low efficiency. There was this.

In addition, FIG. 3 is a diagram illustrating a voltage spike of a low loss power factor correction circuit according to the prior art. As shown in FIG. 3, when the switching semiconductor device is turned off and the diode is turned on, due to the leakage inductance of the inductor A spike occurs in the relationship between the voltage V _DS between the drain and the source of the switching semiconductor element. Here, the spike refers to an instantaneous transient phenomenon in a portion of the pulse waveform, and the voltage spike (V _spike ) means a portion V _b far exceeding the average amplitude V _a of the pulse and the average amplitude of the pulse ( Means a difference from V _a ). Therefore, conventionally, there is a problem in that damage is caused in the circuit due to a severe voltage spikes _(spike V) produced as described above.

In addition, FIG. 4 is a diagram illustrating a turn-on and turn-off loss of the low-loss power factor correction circuit according to the prior art. As shown in FIG. 4, V _DS falls when the switching semiconductor device is turned on due to the characteristics of the switching semiconductor device. Since the V _DS rises faster than the speed at which the switching semiconductor device is turned off, there is a problem that the turn-off loss B of the switching semiconductor device is larger than the turn-on loss A of the switching semiconductor device.

Accordingly, the present invention has been made to solve the above problems, and by adding a saturable core, a spike reduction unit and a turn-off loss reduction unit, the turn-on and turn-off loss of the switching semiconductor element can be reduced and the loss of the diode can be reduced. In addition, the present invention provides a low loss power factor correction circuit capable of suppressing serious circuit damage by reducing voltage spikes caused by leakage inductance of an inductor.

Low loss power factor correction circuit according to the present invention for achieving the above object, the rectifier for rectifying the input AC power source and outputs a DC voltage according thereto; A first inductor having one end connected to an output terminal of the rectifier; A first switching element connected between the output end of the rectifier and the other end of the first inductor; A second inductor having one end connected to a first node to which the first inductor and the first switching element are connected; A first capacitor connected between a second node connected to the other end of the second inductor and a ground terminal; A second switching element connected between the second node and a third node at which a DC voltage is output; And a second capacitor connected between the third node and a ground terminal.

Here, the rectifier is characterized by consisting of a bridge diode.

At this time, the rectifier, characterized in that the third capacitor for converting the rectified input power into a smooth DC voltage further comprises.

The first switching element is a switching semiconductor element.

The second switching element is a diode.

The apparatus may further include a third switching device connected between the output terminal of the rectifier and the third node.

At this time, the third switching element is characterized in that the diode.

In addition, the first inductor is characterized in that a core having a characteristic of repeating the increase and decrease of the magnetic flux and reciprocating a predetermined section on the hysteresis curve is used.

In addition, the second inductor is characterized in that a saturable core is used.

In addition, a spike reduction unit for reducing a voltage spike generated when the first switching device is turned off is connected between the first node and the third node.

In this case, the spike reduction unit, it is characterized in that the diode and the zener diode for the switching operation is connected.

The diode may be connected between the first node and the second node, and the zener diode may be connected between the second node and the third node.

The turn-off loss reducing unit may be connected between the third node and the ground terminal to reduce the off-loss of the switching semiconductor device.

In this case, the turn-off loss reduction unit may include a fourth capacitor charged when the first switching element is turned off; Fourth and fifth switching elements that are turned on to form a current path for charging the fourth capacitor when the first switching element is turned off; And a resistor forming a current path for discharging the fourth capacitor when the first switching element is turned on.

In addition, the fourth capacitor is characterized in that the connection between the fourth node and the ground terminal.

The fourth switching element is connected between the second node and the ground terminal.

In addition, the fifth switching device is characterized in that connected between the second node and the fourth node.

In addition, the resistor is characterized in that connected in parallel with the fifth switching element.

The fourth and fifth switching elements are diodes.

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

5 shows a circuit diagram of a low loss power factor correction circuit 500 according to the present invention.

As shown in FIG. 5, the low loss power factor correction circuit 500 according to the present invention includes a rectifying unit 501 for rectifying an input AC power and outputting a DC voltage according thereto, and one end of the rectifying unit 501 at an output terminal of the rectifying unit 501. The first inductor 502 is connected, the first switching element 503 is connected between the output terminal of the rectifier 501 and the other end of the first inductor 502, the first inductor 502 and the first switching A second inductor 506, one end of which is connected to the first node a to which the device 503 is connected, and a second node b connected to the other end of the second inductor 506, and a ground terminal connected thereto. The first capacitor 507, the second switching element 504 connected between the second node b and the third node c outputting a DC voltage, and the third node c and ground. And a second capacitor 505 connected between the stages.

In addition, a spike reducing unit 508 is connected between the first node a and the third node c to reduce voltage spikes generated when the first switching element 503 is turned off. A turn off loss reduction unit 509 for reducing turn off loss of the first switching element 503 is connected between the third node c and the ground terminal.

In addition, a third switching element 510 is connected between the output terminal of the rectifier 501 and the third node c. In this case, a diode is used as the third switching element 510.

Here, the rectifier 501 is composed of a bridge diode 501a and a third capacitor 501b, the bridge diode 501a rectifies the input AC power, and the third capacitor 501b is the bridge diode ( It serves to smooth the power source rectified from 501a).

The input DC voltage of the low loss power factor correction circuit 500 is applied to the first switching element 503 and the second switching element 504 through the first inductor 502.

Here, as the first inductor 502, a core having a characteristic of repeatedly increasing and decreasing magnetic flux and reciprocating a predetermined section on a hysteresis curve is used, and a ferrite core is most commonly used.

In addition, a switching semiconductor element is used as the first switching element 503, and a transistor, a FET, an IGBT, etc. are used as the switching semiconductor element, but a FET is usually used the most, and as the second switching element 504. Diodes are used.

On the other hand, when the first switching device 503 is turned on and the second switching device 504 is turned off, the energy of the input DC voltage is accumulated in the first inductor 502, the first switching device When 503 is turned off and the second switching device 504 is turned on, the energy accumulated in the first inductor 502 is superimposed on the input DC voltage and rectified by the second switching device 504. Since the second capacitor 505 is smoothed and output as the output DC voltage Vo, the magnitude of the output DC voltage Vo is greater than the magnitude of the input DC voltage.

Conventionally, when the first switching element 503 is turned on and the second switching element 504 is turned off, a reverse leakage characteristic is generated in the second switching element 504 due to a reverse recovery characteristic. In this case, since the generated reverse leakage current causes a significant loss in the turn-on of the first switching element 503 and the turn-off of the second switching element 504, in the present invention, the occurrence of the reverse leakage current is minimized. In order to connect the second inductor 506 between the first node (a) and the second node (b).

In this case, the second inductor 506 uses a saturable core, and the saturable core refers to a core that becomes saturated even though a small current flows due to a high permeability.

Here, saturation means that there is no change in the magnetic flux anymore, and since there is no change in the magnetic flux, the inductance value becomes zero. This can be proved through the formula L = n (dφ / dt), which represents the inductance. (L: inductance, φ: magnetic flux, n: number of turns)

In addition, since the voltage applied to the inductor is expressed as V = L (di / dt), when the inductance value is 0 as described above, the voltage applied to the inductor becomes 0, resulting in the same result as when only a wire exists without an inductor. do.

On the other hand, before saturation, the saturable core has a characteristic that the value of inductance is considerably large even when a small amount of current flows. Accordingly, it serves to hinder the flow of current before saturation.

Thus, the saturable core can play a role similar to a switch. In other words, it can be said to be turned on in the saturation region and turned off in the saturation region. Accordingly, in the present invention, when the reverse leakage current flows due to the reverse recovery characteristic of the second switching device 504, the second inductor 506 is turned off to minimize the reverse leakage current, and the first switching device When 503 is turned off so that current Ioff flows in the second inductor 506, the second inductor 506 is turned on to reduce the loss of the second switching element 504. It is designed.

In addition, in the related art, when the first switching element 503 is turned off and the second switching element 504 is turned on, due to leakage inductances of the first inductor 502 and the second inductor 506. Since a spike has occurred in the relationship between the voltage (hereinafter, V _DS ) between the drain and the source of the first switching element 503, causing serious damage to the circuit. In the present invention, in order to reduce such spike, the first node The spike reduction unit 508 is connected between (a) and the third node (c).

At this time, the spike reduction unit 508 is composed of a diode 508a and a zener diode 508b for switching operation, the diode is connected between the first node (a) and the second node (b), The zener diode is connected between the second node (b) and the third node (c).

The process of reducing the voltage spike by the spike reduction unit 508 configured as described above is as follows.

First, when the output DC voltage Vo to be outputted is 400V, if a transient response exceeding 400V is generated due to the generated voltage spike, the diode 508a and the zener diode of the spike reduction unit 508 ( 508b is turned on, so that the current flows through the spike reducing unit 508, so that the voltage spike generated by the leakage inductance of the first inductor 502 and the second inductor 506 is reduced to 400V. Maintains the output direct-current voltage Vo.

In addition, due to the characteristics of the switching semiconductor device used as the first switching device 503, the first switching device 503 may be turned off than the speed at which V _DS is lowered when the first switching device 503 is turned on. when V _DS is the rising speed is faster to and, since the first switching element 503 is greater lost when the first switching element 503 is turned to be off than when turned on occurs, in the present invention V _DS In order to slow the rising rate of, a turn-off loss reduction unit 509 is connected between the second node b and the ground terminal.

In this case, the turn-off loss reduction unit 509 may include a fourth capacitor 509a that is charged with charge when the first switching element 503 is turned off, and when the first switching element 503 is turned off. And fourth and fifth switching elements 509b and 509c that are turned on to form current paths for charging the fourth capacitor 509a, and when the first switching element 503 is turned on, the fourth capacitor. The resistor 509d forms a current path for discharging 509a. In this case, a diode is used as the fourth and fifth switching elements 509b and 509c.

Here, the fourth capacitor 509a is connected between the fourth node d and the ground terminal, and the fourth switching element 509b is between the second node b and the ground terminal, and the fifth switching is performed. The element 509c is connected between the second node b and the fourth node d, and the resistor 509d is connected in parallel with the fifth switching element 509c.

The process of reducing the loss generated when the first switching device 503 is turned off by the turn-off loss reduction unit 509 configured as described above will be described below.

First, as shown in FIG. 5, when the first switching device 503 is turned off, the fourth and fifth switching devices 509b and 509c are turned on so that the current I _off flows, and accordingly, the fourth capacitor 509a is to be charged.

In addition, when the first switching device 503 is turned on, the fourth and fifth switching devices 509b and 509c are turned off to discharge the fourth capacitor 509a, thereby allowing the current I _on to flow. do.

If the above process is repeated, the turn-off time of the first switching device 503 can be delayed, and thus the rising speed of the V _DS can be slowed down, so that the first switching device 503 is turned off. It is possible to reduce the losses incurred.

Preferred embodiments of the present invention described above are disclosed for the purpose of illustration, and various substitutions, modifications, and changes within the scope without departing from the spirit of the present invention for those skilled in the art to which the present invention pertains. It will be appreciated that such substitutions, changes, and the like should be considered to be within the scope of the following claims.

As described above, according to the low-loss power factor correction circuit according to the present invention, the inductance value is set to 0 at saturation, and the saturation core is added to significantly increase the value of the inductance at saturation, thereby minimizing the reverse leakage current. As a result, the turn-on loss of the switching semiconductor device can be reduced and the loss of the diode can be reduced.

In addition, by adding a spike reducing unit, it is possible to reduce voltage spikes generated due to leakage inductance of the inductor, thereby preventing serious circuit damage.

In addition, by adding a turn-off loss reduction unit, it is possible to delay the turn-off time of the switching semiconductor element, and accordingly, the rising speed of the V _DS can be slowed down, thereby reducing the loss generated when the switching semiconductor element is turned off. It has an effect.

Claims (19)

A rectifier for rectifying the input AC power and outputting a DC voltage according thereto; A first inductor having one end connected to an output terminal of the rectifier; A first switching element connected between the output end of the rectifier and the other end of the first inductor; A second inductor having one end connected to a first node to which the first inductor and the first switching element are connected; A first capacitor connected between a second node connected to the other end of the second inductor and a ground terminal; A second switching element connected between the second node and a third node at which a DC voltage is output; And And a second capacitor connected between the third node and a ground terminal. The method of claim 1, The rectifier is a low loss power factor correction circuit, characterized in that consisting of a bridge diode. The method of claim 2, The rectifier further includes a third capacitor for converting the rectified input power into a smooth DC voltage. The method of claim 1, And the first switching element is a switching semiconductor element. The method of claim 1, And said second switching element is a diode. The method of claim 1, And a third switching device connected between the output terminal of the rectifier and a third node. The method of claim 6, And said third switching element is a diode. The method of claim 1, The first inductor is a low-loss power factor correction circuit, characterized in that the core having a characteristic of repeating the increase and decrease of the magnetic flux and reciprocating a predetermined section on the hysteresis curve is used. The method of claim 1, The second inductor is a low loss power factor correction circuit, characterized in that a saturable core is used. The method of claim 1, And a spike reduction unit for reducing a voltage spike generated when the first switching element is turned off between the first node and the third node. The method of claim 10, The spike reduction unit, a low-loss power factor correction circuit, characterized in that the switching diode and the zener diode is configured to be connected. The method of claim 11, And the diode is connected between the first node and the second node, and the zener diode is connected between the second node and the third node. The method of claim 4, wherein And a turn-off loss reduction unit for reducing the off-loss of the switching semiconductor element between the third node and the ground terminal. The method of claim 13, wherein the turn off loss reduction unit, A fourth capacitor charged when the first switching element is turned off; Fourth and fifth switching elements that are turned on to form a current path for charging the fourth capacitor when the first switching element is turned off; And And a resistor for forming a current path for discharging said fourth capacitor when said first switching element is turned on. The method of claim 14, And said fourth capacitor is connected between a fourth node and a ground terminal. The method of claim 14, The fourth switching device, the low power factor correction circuit, characterized in that connected between the second node and the ground terminal. The method of claim 14, And the fifth switching element is connected between the second node and a fourth node. The method of claim 17, And the resistor is connected in parallel with the fifth switching element. The method according to claim 16 or 17, And said fourth and fifth switching elements are diodes.

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