KR100319524B1 - Passive PFC circuit - Google Patents

Abstract

According to the present invention, a first electrolytic capacitor having a cathode terminal connected to a + output terminal of a bridge diode rectifying an input AC power source, an anode terminal connected to an -output terminal of the bridge diode, and a cathode connected to an anode terminal of the first electrolytic capacitor A first diode having a terminal connected thereto, a third diode having a cathode terminal connected to the + output terminal of the bridge diode, an anode terminal connected to the -output terminal of the bridge diode, and having a cathode connected to the anode terminal of the third diode A second electrolytic capacitor having a terminal connected thereto, and an anode terminal connected to a connection point of the first electrolytic capacitor and the first diode, and a second diode having a cathode terminal connected to a connection point of the second electrolytic capacitor and the third diode It relates to a high power factor correction circuit of Valley Filled type, in particular, to the AC input terminal of the bridge diode. Compared to the second diode in parallel to improve the current limit and power factor, and a capacitor connected to the second diode in parallel to reduce the switching noise in the second diode to improve the EMI to provide a passive high power factor compensation circuit Therefore, the switching noise generated during the switching operation of the diode can be suppressed without being limited by variations in the input voltage or the output load.

Description

Passive high power factor correction circuit {Passive PFC circuit}

The present invention relates to a high power factor correction circuit, and more particularly, to a passive high power factor correction circuit capable of suppressing switching noise generated during switching operation of a diode without being limited by variations in input voltage or output load.

Many circuits proposed so far have advantages and disadvantages. Therefore, which of the proposed circuits is to be adopted should consider whether the circuit employed in the selected system is economical and suitable. From this point of view, one of the tasks that must be overcome to implement the high power factor correction circuit is firstly to reduce current distortion for a wide variation of input voltage and large output load, and thirdly, economically and fourthly, to implement easily.

However, the average current mode control, which provides the most functionally improved control form among the circuits introduced so far, is automatically controlled in the form of mixed input current (DCM + CCM) even when the input voltage or output load changes, and is proportional to the input voltage. It is possible to obtain the current waveform that forms a sine curve, which makes the linear current distortion very low. However, the technically complicated control structure makes it difficult to understand and increases the number of external parts for realization.

On the other hand, the CURRENT CLAMPED control method, which is additionally designed with low-cost feedforward function, is one of the simplest PFC circuit configurations and has the advantage of being easy to implement and economical. If there is a variation in the output load or the output load is less than 50%, the linear current distortion increases rapidly and the total harmonic distortion (TOTAL HARMONIC DISTORTION-THD) has the disadvantage of increasing the variation of the input voltage and the output load. Will receive.

As described above, the conventional high power factor correction circuits have their disadvantages. Among them, the conventional 'Valley Filled PFC' circuit has a bridge diode (BD) for rectifying the input AC power, as shown in FIG. A first electrolytic capacitor (C1) having a cathode terminal connected to the + output terminal of the anode, and an anode terminal is connected to the-output terminal of the bridge diode (BD), the cathode terminal is connected to the anode terminal of the first electrolytic capacitor (C1) An anode terminal is connected to the first diode D1, a third diode D3 having a cathode terminal connected to a + output terminal of the bridge diode BD, and an output terminal of the bridge diode BD. And an anode terminal connected to a connection point between the second electrolytic capacitor C2 and the first electrolytic capacitor C1 and the first diode D1 having a cathode terminal connected to an anode terminal of the third diode D3. Second electrolysis The second diode D2 has a cathode terminal connected to a connection point of the capacitor C2 and the third diode D3.

In the existing 'Valley Filled PFC' circuit configured as described above, the power factor is improved by continuously flowing the input current at 1/2 or more of the input voltage.

However, when the input voltage reaches 1/2 or more of the maximum value, the input current flows excessively, and switching noise of the diode is generated.

An object of the present invention for solving the above problems relates to a high power factor correction circuit, in particular, to suppress the switching noise generated during the switching operation of the diode without being limited by variations in input voltage or output load. To provide a passive high power factor correction circuit.

1 is an exemplary configuration diagram of a conventional Valley Filled PFC,

2 is an exemplary configuration diagram of a passive high power factor correction circuit according to the present invention;

3 is an exemplary input voltage current waveform of the passive high power factor correction circuit according to the present invention shown in FIG.

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

BD: bridge diode D1 to D3: diode

C1, C2: Electrolytic Capacitor C3: Capacitor

A feature of the present invention for achieving the above object is a first electrolytic capacitor having a cathode terminal connected to the + output terminal of the bridge diode rectifying the input AC power source, an anode terminal is connected to the-output terminal of the bridge diode and A first diode having a cathode terminal connected to the anode terminal of the first electrolytic capacitor, a third diode having a cathode terminal connected to the + output terminal of the bridge diode, and an anode terminal connected to the -output terminal of the bridge diode; A second electrolytic capacitor having a cathode terminal connected to the anode terminal of the third diode, an anode terminal connected to a connection point of the first electrolytic capacitor and the first diode, and a cathode terminal connected to a connection point of the second electrolytic capacitor and the third diode In the high power factor correction circuit of the Valley Filled type composed of a second diode connected to: A coil provided at the AC input terminal of the diode to improve current limiting and power factor; And a capacitor connected to the second diode in parallel to reduce switching noise of the second diode to improve EMI.

The above objects and various advantages of the present invention will become more apparent from the preferred embodiments of the invention described below with reference to the accompanying drawings by those skilled in the art.

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

FIG. 2 is a diagram illustrating a configuration of a passive high power factor correction circuit according to the present invention, a first electrolytic capacitor C1 having a cathode terminal connected to a + output terminal of a bridge diode BD rectifying an input AC power, and the bridge A first diode D1 having an anode terminal connected to the -output terminal of the diode BD and a cathode terminal connected to the anode terminal of the first electrolytic capacitor C1, and a + output terminal of the bridge diode BD. A third electrode D3 having a cathode terminal connected thereto, and an anode terminal connected to the -output terminal of the bridge diode BD, and a second electrolyte having a cathode terminal connected to the anode terminal of the third diode D3. An anode terminal is connected to a condenser C2, a connection point of the first electrolytic capacitor C1 and a first diode D1, and a cathode terminal is connected to a connection point of the second electrolytic capacitor C2 and the third diode D3. To the second diode (D2) To which the following components are added to the conventional circuit configuration properties.

The additional components are a capacitor C3 connected in parallel to the second diode D2 and a coil L1 provided at an AC input terminal of the bridge diode BD.

The coil L1 provided in the passive high power factor correction circuit according to the present invention configured as described above is provided for the purpose of current limiting and power factor improvement, and the capacitor C3 reduces the switching noise of the diode to improve EMI. It is connected to both ends of the second diode (D2) for the purpose to perform the function of snubber (snubber).

That is, as shown in FIG. 3, the input current starts to flow when the input voltage reaches 1/2 or more of the maximum value and resembles the form of the input voltage, and does not flow when the input voltage reaches 1/2 or less of the maximum value.

At this time, the excessively flowing current is limited to the coil L1, and the coil L1 further filters the current to further improve the power factor, and the capacitor C3 reduces the switching noise of the diode to improve EMI. It is connected to both ends of the second diode D2 and performs a function of snubber.

While the invention has been shown and described in connection with specific embodiments thereof, it will be appreciated that various modifications and changes can be made without departing from the spirit and scope of the invention as indicated by the claims. Anyone who owns it can easily find out.

As described above, when the passive high power factor correction circuit according to the present invention is provided, switching noise generated during the switching operation of the diode can be suppressed without being limited by variations in input voltage or output load.

Claims (1)

A first electrolytic capacitor having a cathode terminal connected to a + output terminal of a bridge diode rectifying an input AC power source, an anode terminal connected to a negative output terminal of the bridge diode, and a cathode terminal connected to an anode terminal of the first electrolytic capacitor. A first diode, a third diode having a cathode terminal connected to the + output terminal of the bridge diode, an anode terminal connected to the -output terminal of the bridge diode, and a cathode terminal connected to the anode terminal of the third diode Valley-filled type consisting of a second electrolytic capacitor and a second diode having an anode terminal connected to a connection point of the first electrolytic capacitor and a first diode and a cathode terminal connected to a connection point of the second electrolytic capacitor and a third diode. In the high power factor correction circuit of: A coil provided at an AC input terminal of the bridge diode to improve current limit and power factor; And a capacitor connected in parallel to the second diode to reduce switching noise of the second diode to improve EMI.