KR20040001573A - Single stage high power factor converter - Google Patents

Abstract

PURPOSE: A single stage high-power-factor converter is provided to reduce the total size, the weight, and the manufacturing cost by obtaining the high-power factor and controlling an output voltage without using a power circuit and a high-priced high-power-factor IC. CONSTITUTION: A single stage high-power-factor converter includes an input filter circuit(10), a rectification circuit(20), a high-power-factor power circuit(40), and an output control circuit(50). The input filter circuit(10) is used for filtering an input voltage. The rectification circuit(20) is used for rectifying the filtered input voltage of the input filter circuit(10). The high-power-factor circuit(40) is used for performing a high-power-factor operation according to a PWM signal of a PWM control circuit(70). The output control circuit(50) is used for controlling the high-power-factor and the output voltage of the high-power-factor power circuit(40). The single stage high-power-factor converter further includes a noise/inverse current prevention circuit(30) to reduce the noise of a first inductor and prevent the inverse current.

Description

Single power stage high power factor converter {SINGLE STAGE HIGH POWER FACTOR CONVERTER}

The present invention relates to a single power stage high power factor converter for application to power supplies used in home appliances, measuring equipment, and industrial products, and more particularly, using a single switch for high power factor in the use of power supplies. The present invention relates to a single power stage high power factor converter that is designed to reduce the link capacitor voltage while improving the input filter to effectively reduce very high frequency noise current including discontinuous current.

A typical converter power system is composed of an input power supply unit, a control unit and a converter unit. In this case, the input power supply unit obtains the DC power of the converter by rectifying the input voltage by the input diode rectifier. However, diode rectifiers have various problems such as reduced power factor of input current and high frequency generation.

A method generally used to achieve high power factor in a converter circuit that outputs a DC power source is shown in FIG. 1. Referring to FIG. 1, an AC input power source, an input filter, a diode rectifier, a high power factor circuit, and a DC / DC converter are sequentially connected. That is, the high power factor circuit is added to the existing converter.

In this method, a high power factor circuit is added to the converter to be used, causing a problem in that the price of the product increases and the weight and size of the product increase.

Recently, in order to overcome this problem, a converter technology has been proposed that eliminates the need for a high power factor control IC by using one switch Q1 as shown in FIG. 2. In this case, since the power factor control is automatically performed by the operation of the switch Q1 in FIG. 2, a separate controller for power factor control is not necessary.

However, in the circuit having a single switch as shown in FIG. 2, the switching operation of the switch Q1 generates a very large high frequency noise current including a discontinuous current, and effectively filters the high frequency current at the DC stage. There was this difficult issue.

In more detail, in the case of the high power factor converter having a single switch Q1 according to the related art, each rectifier diode DR1, DR2, DR3, DR4 of the diode rectifier uses a low-cost commercial diode, in which case the rectification is performed. When the diode is switched at a high speed, the switching loss is greatly increased according to the switching operation, and the switching noise of each rectifier diode is further increased.

The present invention has been made to solve the above problems, the object of which is a very high frequency noise current including a discontinuous current generated by the switching of the switch (Q1) which is a disadvantage of the high power factor converter using a conventional single switch To provide a single power stage high power factor converter that can effectively reduce the power consumption.

Another object of the present invention is to provide a single power stage high power factor converter capable of simultaneously controlling the output voltage while achieving a high power factor without including a power circuit and an expensive high power factor IC.

In addition, another object of the present invention is to provide a single power stage high power factor converter that can operate smoothly without breaking the circuit despite the reduction of noise by providing a circuit for preventing the reverse current.

According to an aspect of the present invention for achieving the above object, an input filter circuit for filtering an input voltage applied from the outside; A rectifier circuit for rectifying the input voltage filtered through the input filter circuit; A high power factor power circuit for turning on the switch by a PWM signal output from a PWM control circuit sensing a load voltage and a load current to output a current to the first inductor to perform a high power factor operation; And an output control circuit for controlling the high power factor and the output voltage output through the high power factor power circuit; And a first capacitor connected between the output terminals of the rectifier circuit and a first diode connected to the output terminal of the rectifier circuit and the cathode terminal connected to the input terminal of the high power factor power circuit. When the input voltage is output, a single power unit including a noise and reverse current prevention circuit that reduces noise generated in the first inductor and prevents current flowing in the reverse direction due to switching of a high power factor and a switch for controlling the output voltage. Provide a power factor converter.

At this time, according to an additional feature of the present invention, the PWM control circuit is coupled to the first inductor included in the high power factor power circuit to generate a power source, or to the second inductor included in the output control circuit coupling It is preferable to receive the control power from any one of the inductor means to generate power.

According to another additional aspect of the present invention, the high power factor power circuit includes a DC link capacitor constituting the first inductor and an LC circuit, and a transformer having a center tap to reduce the voltage rise of the DC link capacitor. It is preferable to include.

1 is a block diagram showing the configuration of a high power factor converter according to the prior art;

2 is a circuit diagram showing the configuration of a high power factor converter having one switch according to the prior art.

3 is a block diagram showing the configuration of a single power stage high power factor converter according to the present invention.

4 is a circuit diagram showing the configuration of a single power stage high power factor converter according to an embodiment of the present invention.

5 is a circuit diagram showing the configuration of a single power stage high power factor converter according to another embodiment of the present invention.

FIG. 6 is a diagram for describing a configuration of generating control power in the first inductor of FIG. 4. FIG.

FIG. 7 is a diagram for describing a configuration of generating control power in the second inductor of FIG. 4. FIG.

8 is a circuit diagram illustrating a voltage and current sensing unit in the single power stage high power factor converter of the present invention.

9 is a circuit diagram showing a configuration in which the technical matters of the present invention are applied to a flyback converter.

<Explanation of symbols for the main parts of the drawings>

5: AC power supply 10: input filter circuit

20: rectifier circuit 30: noise and reverse current prevention circuit

40: high power factor power circuit 50: output control circuit

60: load 70: PWM control circuit

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

Hereinafter, the present invention will be described as a preferred embodiment of a single power stage high power factor converter for applying to a power supply device used in home appliances, measuring equipment, and industrial products, but the technical idea of the present invention is not limited thereto. Of course, it can be variously modified by those skilled in the art.

A single power stage high power factor converter according to an embodiment of the present invention will be described in detail with reference to FIGS. 3 to 9 as follows.

Figure 3 is a block diagram showing the configuration of a single power stage high power factor converter according to the present invention, Figure 4 is a circuit diagram showing the configuration of a single power stage high power factor converter according to an embodiment of the present invention.

3 and 4, reference numeral 5 denotes an AC power source applied from the outside, and 10 denotes an input filter circuit for filtering an unnecessary portion included in the voltage input from the AC power source 5. 20 denotes a rectification circuit for performing rectification on the input voltage filtered through the input filter circuit 10. At this time, the rectifier circuit 20 is composed of a diode bridge including a plurality of diodes (DR1, DR2, DR3, DR4).

In addition, reference numeral 30 denotes a noise and reverse current prevention circuit that effectively reduces switching noise and simultaneously prevents current from flowing in the reverse direction, and 40 denotes a high power factor power for performing a high power factor operation according to an input PWM control signal. A circuit represents a circuit, 50 represents an output control circuit for controlling the output voltage output through the high power factor power circuit 40, 60 represents a load, 70 represents a load voltage and a load current, and accordingly, A PWM control circuit for outputting a PWM control signal to the high power factor power circuit 40 is shown.

At this time, the noise and reverse current prevention circuit 30 is the first inductor (D1) due to the switching of the first diode (D1) for preventing the current flowing in the reverse direction, and the switch (Q1) for controlling the high power factor and output voltage ( In order to reduce noise generated in L1), the first capacitor C1 is connected between both output terminals of the rectifier circuit 20.

In addition, the high power factor power circuit 40 includes a first inductor L1 and a DC link capacitor C3 constituting an LC circuit, a transformer T for converting an output voltage into a voltage suitable for the load 60, and The switch Q1 connected to the primary side of the transformer T and on / off operating according to the PWM control signal of the PWM control circuit 70 and the output voltage Vs of the rectifier circuit 20 are low. A second diode (D2) and a second capacitor (C2) are included to perform a function of increasing the input power factor by allowing a current to flow through the first inductor (L1).

In addition, the output control circuit 50 is composed of a DC-DC converter, the third diode (D3) and the fourth diode (D4) and connected to the secondary output terminal of the transformer (T) to prevent reverse current, A second inductor L2 connected to the secondary output terminal of the transformer T and a fourth capacitor C4 connected to the input terminal of the load 60 are included to obtain a control power supply of the PWM control circuit 70.

At this time, the PWM control circuit 70 represents a PWM controller including an existing IC for controlling the output voltage, and is automatically made by the switch Q1 in the PWM control, there is no need for a separate controller for power factor control.

Referring to the operation of the present invention having the configuration as described above in detail.

Due to the switching of the switch Q1, a very large high frequency noise component including a discontinuous current may be included in the first inductor L1. The noise current may be a DC power supply unit next to the rectifier circuit 20, that is, noise and inversion. It is effective to filter by the current prevention circuit 30. Therefore, the present invention effectively reduces noise by adding the first capacitor C1 to the noise and reverse current prevention circuit 30. In this case, the first diode D1 prevents the reverse current of the first inductor L1 and operates smoothly without breaking the circuit according to the change of the load and the input voltage.

During the above operation, the operation of the output control circuit 50 and the PWM control circuit 70 performs the same operation as the general case. That is, referring to the operation of the PWM control circuit 70, the current delivered to the load 60 of the output voltage and the current flowing through the switch (Q1) is sensed based on the result. At this time, since the switch Q1 includes a current flowing in the second capacitor C2 in addition to the current delivered to the load 60, only the component transmitted to the load 60 side should be sensed using the current sensing unit.

Therefore, the sensing of the current may be performed at the output side of the circuit and may be sensed at the primary side of the transformer T. That is, the current sensing units 1 and 2 are intended to remove the current because the current of the switch Q1 includes the current of the second capacitor C2 for the high power factor in addition to the PWM output current.

Meanwhile, referring to the operation of the high power factor power circuit 40, if there is no second diode D2 and the second capacitor C2, this becomes a general LC filter circuit, and the voltage of the DC link capacitor C3 is the first capacitor. When the output voltage of (C1) is lower than the rectified voltage (Vs), the DC link capacitor (C3) is charged through the first inductor (L1), the rectified voltage (Vs) than the voltage of the DC link capacitor (C3) If this is low, no current flows. In this case, the input power factor is very low.

In order to increase the input power factor, even when the rectified voltage Vs is low, a current substantially proportional to the rectified voltage Vs is allowed to flow through the first inductor L1. This function is performed by the second diode D2 and the second capacitor C2.

In this case, even if the input voltage is low in the first capacitor C1, a current may flow in the first inductor L1, thereby increasing the power factor. That is, when the switch Q1 is ON, the voltage of the second capacitor C2 is initially lower than the input rectified voltage Vs, so that the current of the first inductor L1 is transmitted through the second diode D2. It flows through the switch Q1 through the second capacitor C2 without flowing, thereby increasing the current of the first inductor L1.

The increase in the current of the first inductor L1 is performed until the voltage of the second capacitor C2 becomes equal to the input voltage, that is, the rectified voltage Vs. In this case, the first inductor L1 current flows through the second capacitor C2 until the voltage of the second capacitor C2 is equal to the voltage of the DC link capacitor C3. That is, when the voltage of the second capacitor C2 is greater than the voltage of the DC link capacitor C3, the second diode D2 is turned on so that the current of the first inductor L1 is changed to the second capacitor ( The DC link capacitor C3 is charged through the second diode D2 without flowing to C2).

In addition, when the switch Q1 is turned off, the magnetizing inductor current of the transformer T is discharged to the second capacitor C2 to charge the voltage of the second capacitor C2 in reverse. In this case, the current of the first inductor L1 may be “0”, and the rectified voltage and the DC are connected to the transformer T and the first inductor L1 by the first capacitor C1 connected for noise reduction. The voltage difference from the link voltage is applied.

This means that the transformer T may cause saturation, and the function of preventing the transformer T is performed by the first diode D1. That is, if there is no first diode D1, the transformer T may be saturated when there is a load change or a sudden change in the input voltage, thereby causing the breakdown of the second diode D2 and the switch Q1.

Therefore, the circuit without the first diode D1 is a cause which is almost impossible to use due to such a disadvantage.

Although the voltage of the DC link capacitor C3 is very low at no load, the voltage of the DC link capacitor C3 increases gradually as the load 60 increases and becomes maximum, and then decreases again when the load increases further. At this time, the maximum value of the DC link voltage of the DC link capacitor C3 has a higher value than a circuit having only the existing LC filter without the second diode D2 and the second capacitor C2.

An increase in the DC link voltage of the DC link capacitor C3 causes a price increase and a volume increase, which may be a disadvantage, and thus may be reduced by connecting a center tap to the transformer T. Since the presence of the sensor tap increases the voltage portion at the bottom of the center tap when the voltage of the DC link capacitor C3 is large, the current increase of the first inductor L1 is slowed down when the switch Q1 is turned on. The voltage rise of the link capacitor C3 can be reduced.

6 and 7 illustrate circuits used to reduce an increase in the voltage of the DC link capacitor C3, and FIG. 6 illustrates a configuration of generating control power in the first inductor L1. FIG. 7 is a diagram for describing a configuration of generating control power in the second inductor L2.

Referring to FIG. 6, a process of obtaining a power source of the PWM control circuit 70 by coupling to the first inductor L1 is illustrated. At this time, when current begins to flow in the first inductor L1, power is supplied to a control circuit power source, which is a coupled circuit. At this time, the load 60, which is a control circuit, has a very small power, but a voltage variation of the first inductor L1 occurs during a period immediately after the ON / OFF of the switch Q1. That is, power is supplied to the control circuit only during a short period of time during which current flows in the second capacitor C2. This means that the DC link voltage rise can be significantly lowered at a low load which greatly increases the voltage of the DC link capacitor C3.

Therefore, a circuit having a control power source from the first inductor L1 or the second inductor L2 rather than the transformer T has a great advantage of reducing the voltage of the DC link capacitor C3.

8 is a circuit diagram of a current sensing unit.

Referring to FIG. 8, in order to output a PWM control signal from the PWM control circuit 70, a voltage and a current must be sensed. A voltage sensing unit, a current sensing unit 1, and a current sensing unit 2 are provided for this purpose. The current of the switch Q1 is necessary for the current mode control of the PWM control circuit 70, but the current of the switch Q1 cannot be used because the current of the high power factor power circuit 40 is added. Therefore, the current sensing units 1 and 2 should be sensed on the transformer primary side or the transformer secondary side as shown in FIG. 8. In addition, the voltage sensing unit senses at the output terminal of the output control circuit 50.

The present invention is not limited to the embodiments described above, and various modifications and changes can be made by those skilled in the art, which are included in the spirit and scope of the present invention as defined in the appended claims. For example, the technical idea of the present invention can be applied to a flyback converter as shown in FIG. 9.

As described above, the application of the single power stage high power factor converter of the present invention does not include a power circuit and an expensive high power factor IC, but it is possible to simultaneously control the output voltage while achieving a high power factor. This has the effect of lowering weight, weight and product price.

In addition, in the present invention, by effectively removing the noise current including the discontinuous high frequency noise generated by using a single switch in the DC unit, it is effective to reduce the burden on the input filter circuit, and to effectively reduce the DC link voltage It works.

In addition, in the present invention, by providing a circuit for preventing the reverse current, there is an effect that the circuit can be operated smoothly without being destroyed despite the reduction of noise.

Claims (3)

An input filter circuit 10 for filtering an input voltage applied from the outside; A rectifier circuit 20 for rectifying the input voltage filtered through the input filter circuit; A high power factor operation is performed by turning on the switch Q1 by the PWM signal output from the PWM control circuit 70 for sensing the load voltage and the load current to output a current to the first inductor L1. Power factor power circuit 40; And an output control circuit (50) for controlling the high power factor and the output voltage output through the high power factor power circuit. A first capacitor connected between both output terminals of the rectifier circuit, and a first diode (D1) having an anode (ANODE) terminal connected to the output terminal of the rectifier circuit and a cathode (CATHODE) terminal connected to the input terminal of the high power factor power circuit. When the rectified input voltage is output, the noise generated from the first inductor L1 is reduced due to the switching of the high power factor and the switch Q1 for controlling the output voltage, and the noise and reverse current prevent the current flowing in the reverse direction. Single power stage high power factor converter characterized in that it comprises a prevention circuit (30). The method of claim 1, The PWM control circuit 70 is coupled to the first inductor L1 included in the high power factor power circuit 40 to generate power, or a second inductor L2 included in the output control circuit 50. And a control power supply from any one of the inductor means coupled to the power generator. The method of claim 1, The high power factor power circuit 40 includes a DC link capacitor C3 constituting the first inductor L1 and an LC circuit, and a transformer T having a center tap to reduce a voltage rise of the DC link capacitor C3. Single power stage high power factor converter comprising a.