JP2018157727A - Bridgeless power factor correction circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a bridgeless power factor correction circuit capable of achieving simplification of a circuit, miniaturization of the whole size and cost reduction without using an expensive circuit component for voltage/current detection.SOLUTION: A bridgeless PFC circuit 100 includes: a step-up inductor L for accumulating energy from an input power source IP and converting a low-voltage high-current to a high-voltage low-current; switches Q1, Q2 for performing switching operation to intermittently accumulate energy in the step-up inductor; rectification elements D1, D1 for preventing backflow of respective currents from the switches; a current smoothing capacitor C for smoothing energy outputted from the step-up inductor L; an input voltage detection circuit 10 for detecting input voltage Vin while defining that the one side of the input power source IP as reference potential; an inductor current detection circuit 20 for detecting an inductor current by a resistor 21 inserted into a path of an inductor current; and an output voltage detection circuit 30 for detecting an output voltage Vo while defining that the one side of the input power source IP as the reference potential.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a bridgeless power factor correction (PFC) circuit having no rectifying bridge, and more particularly to simplification of a voltage / current sensor in a totem pole / bridgeless PFC circuit.

  Conventionally, in a switching power supply connected to an AC input, a PFC circuit is used to improve the power factor of input power and suppress harmonic current. In general, many rectifier bridges are provided, but since the loss of the bridge itself hinders high efficiency and miniaturization, bridgeless PFC circuits that do not have such rectifier bridges have also been proposed. (For example, refer to FIG. 10 of Patent Document 1 or Patent Document 2).

  Furthermore, a switching element that is subject to high-frequency switching in the positive half cycle of the AC input and a switching element that is subject to high-frequency switching in the negative half cycle are connected to the inductor provided on the AC input side, respectively. A totem pole type bridgeless power factor converter has also been proposed (see, for example, Patent Document 3).

JP 2002-017087 A International Publication No. 2010/061654 JP 2012-070490 A

  In the conventional bridgeless PFC circuit, it is necessary to measure the voltage and current on the input side and the voltage on the output side, but there is a switching element that performs switching operation between the input side and the output side of the circuit. Since the potentials at the voltage measurement point and the voltage measurement point on the output side are greatly different, an insulation type detection element or detection circuit such as a transformer is used as in Patent Document 1. For this reason, the circuit is complicated and expensive circuit parts must be used.

  In view of such problems of the prior art, an object of the present invention is to provide a bridge that can simplify a circuit, reduce the overall size, reduce costs, and the like without using expensive circuit components for voltage / current detection. It is to provide a power factor correction circuit.

  In order to achieve the above object, a bridgeless power factor correction circuit according to the present invention accumulates energy from an AC input power source and converts it from a low voltage high current to a high voltage low current, and the boost inductor intermittently. A switching element that performs a switching operation for accumulating energy, a rectifying element that prevents a backflow of current from the switching element, a smoothing capacitor that smoothes energy output from the boost inductor, and the boost inductor An inductor current detection circuit that detects the inductor current by a current detection element inserted in a path of the flowing inductor current, an input voltage detection circuit that detects an input voltage using one side of the input power supply as a reference potential, and an output to a load An output voltage detection circuit that detects the voltage using the one side of the input power supply as a reference potential. And a control unit that controls the switching operation based on an inductor current detection result by the inductor current detection circuit, an input voltage detection result by the input voltage detection circuit, and an output voltage detection result by the output voltage detection circuit. It is characterized by providing.

  Here, the output voltage detection circuit may be configured with, for example, a resistor and a differential amplifier, but is not limited thereto. Moreover, as a current detection element, although resistance is mentioned, for example, it is not restricted to this. One end of the current detection element is connected to the reference potential, and the inductor current detection circuit measures the voltage across the current detection element by measuring one side of the input power supply as a reference potential. The inductor current may be detected.

  The bridgeless power factor correction circuit is specifically a totem pole / bridgeless power factor correction circuit, but is not limited thereto.

  According to the bridgeless power factor correction circuit having such a configuration, it is not necessary to use expensive circuit parts for voltage / current detection, and the circuit can be simplified, the entire size can be reduced, and the cost can be reduced. .

  According to the bridgeless power factor correction circuit of the present invention, it is not necessary to use expensive circuit parts for voltage / current detection, and the circuit can be simplified, the entire size can be reduced, and the cost can be reduced.

1 is a circuit diagram showing a schematic configuration of a totem pole / bridgeless PFC circuit 100 according to an embodiment of the present invention. FIG. 3 is a circuit diagram illustrating a schematic configuration of an inductor current detection circuit 20. FIG. 3 is a circuit diagram illustrating a schematic configuration of an output voltage detection circuit 30. FIG.

  Hereinafter, embodiments according to the present invention will be described with reference to the drawings.

<Overall Configuration of Embodiment>
FIG. 1 is a circuit diagram showing a schematic configuration of a totem pole bridgeless PFC circuit 100 according to an embodiment of the present invention.

  As shown in FIG. 1, a bridgeless PFC circuit 100 stores power energy from an AC input power source IP and converts it from a low voltage and high current to a high voltage and low current, and the boost inductor L is intermittently connected. Switch Q1 and switch Q2 for performing a switching operation for accumulating power energy, rectifier element D1 and rectifier element D1 for preventing backflow of currents from these switches Q1 and Q2, and output from boost inductor L Current smoothing capacitor C for smoothing the generated power energy, input voltage detection circuit 10 for detecting input voltage Vin using one side of input power supply IP as a reference potential, and an inductor current path flowing through boost inductor L Inductor current for detecting the inductor current by the voltage generated across the resistor 21 A detection circuit 20, and an output voltage detection circuit 30 for detecting the output voltage Vo to the output load OL one side of the input power IP as a reference potential.

  Here, the resistor 21 is an example of a current detection element, but such a current detection element is not limited to a resistance.

  Examples of the switch Q1 and the switch Q2 include, but are not limited to, a switching element such as a field effect transistor (FET) and an IGBT.

  Further, the switch Q1 and the switch Q2 have their respective switching operations (ON) so that the output voltage Vo becomes constant based on the detection results by the input voltage detection circuit 10, the inductor current detection circuit 20, and the output voltage detection circuit 30. / Off, timing, etc.) are controlled by a control unit (not shown).

  The input voltage detection circuit 10 includes a resistor 11 and a resistor 12 connected in series. If a voltage obtained by dividing the input voltage Vin is detected, the input voltage Vin can be calculated based on the ratio of the resistor 11 and the resistor 12.

  The output voltage detection circuit 30 includes resistors 31 to 34 and a differential amplifier 35, and details will be described later.

  Further, the power supply of the differential amplifier 27 (details will be described later) and the differential amplifier 35 are common, and a voltage of ± 15 V with a reference potential of 0 V is supplied.

<Specific Example of Inductor Current Detection Circuit 20>
FIG. 2 is a circuit diagram illustrating a schematic configuration of the inductor current detection circuit 20. However, the configuration is not limited to this.

  As shown in FIG. 2, the inductor current detection circuit 20 includes resistors 22 to 25, a capacitor 26, and a differential amplifier 27 in addition to a resistor 21 for detecting the inductor current. One end of the resistor 21 is connected to the inverting input of the differential amplifier 27 through the resistor 23 and is connected to the reference potential, and the other end of the resistor 21 is connected to the non-inverting input of the differential amplifier 27 through the resistor 24. It is connected. The inverting input and output of the differential amplifier 27 are connected via a resistor 22, and a capacitor 26 is connected in parallel with the resistor 22.

  The voltage across the resistor 21 is measured using such a configuration. By calculating the current flowing through the resistor 21 using this voltage and the resistance value of the resistor 21, the inductor current detection circuit 20 can detect the inductor current.

  The bridgeless PFC circuit 100 is supplied with an input voltage Vin of 100 to 240 V from the input power supply IP, and a current of several A to several tens of A flows through the inductor current detection circuit 20. For example, when the value of the resistor 21 is 5 mΩ, the voltage applied to both ends of the resistor 21 is about 75 mV at maximum.

  Accordingly, the voltage at the inverting input of the differential amplifier 27 is the same as the reference potential, and the voltage at the non-inverting input is about 75 mV at maximum, so that the input voltage of the differential amplifier 27 can be lowered.

  At this time, the frequency of the current to be measured is related to the switching frequency of the circuit, but the frequency is high because the current shape is a triangular wave. For example, when the switching frequency is 1 MHz, it is necessary to be able to measure up to about 5 MHz, assuming that the fifth harmonic is included.

<Specific Example of Output Voltage Detection Circuit 30>
FIG. 3 is a circuit diagram illustrating a schematic configuration of the output voltage detection circuit 30.

  As shown in FIG. 3, the resistor 31 and the resistor 32 are connected in series, and the connection point is connected to the non-inverting input of the differential amplifier 35. One end of the resistor 31 (on the opposite side to the resistor 32) is connected to one side (see FIG. 1) of the output load OL, and one end of the resistor 32 (on the opposite side to the resistor 31) is the reference potential on the input power supply IP side. (See FIG. 1). The resistor 33 and the resistor 34 are also connected in series, and the connection point is connected to the inverting input of the differential amplifier 35. One end of the resistor 33 (on the side opposite to the resistor 34) is connected to the other side (see FIG. 1) of the output load OL, and one end of the resistor 34 (on the side opposite to the resistor 33) is the reference potential on the input power source IP side. (See FIG. 1).

  Thus, the output voltage Vo can be detected by measuring the potential difference between both ends of the output load with the input power source IP side as the reference potential. Note that the resistance value ratio of the resistor 31 to the resistor 32 may be several tens of times, for example. The resistance value ratio of the resistor 33 to the resistor 34 is the same. For example, the value of the resistor 31 and the resistor 33 is 493 kΩ, and the value of the resistor 32 and the resistor 34 is 10 kΩ.

  The output voltage Vo to be measured by the output voltage detection circuit 30 is about 400V, but when viewed from the reference potential, the voltage on the switch Q1 side of the output load OL is about 500V, and the voltage on the switch Q2 side is about 100V. . Even in this case, the inverting input of the differential amplifier 35 is about 1V, and the non-inverting input is about 0.2V. Therefore, the input voltage of the differential amplifier 35 can be lowered. The cut-off frequency only needs to correspond to about 20 Hz.

  It should be noted that the present invention can be implemented in various other forms without departing from the spirit or main features thereof. Therefore, the above-mentioned embodiment is only a mere illustration in all points, and should not be interpreted limitedly. The scope of the present invention is indicated by the claims, and is not restricted by the text of the specification. Further, all modifications and changes belonging to the equivalent scope of the claims are within the scope of the present invention.

  The present invention is suitable for an AC-DC converter, a power supply device, and the like, for example.

100 Bridgeless PFC Circuit 10 Input Voltage Detection Circuit 11, 12 Resistance 20 Inductor Current Detection Circuit 22-25 Resistance 26 Capacitor 27 Differential Amplifier 30 Output Voltage Detection Circuit 31-34 Resistance 35 Differential Amplifier C Current Smoothing Capacitor D1, D2 Rectification Element IP Input power supply L Boost inductor OL Output load Q1, Q2 Switch Vin Input voltage Vo Output voltage

Claims (4)

A boost inductor that accumulates energy from an AC input power source and converts low voltage high current to high voltage low current;
A switching element that performs a switching operation for intermittently storing energy in the boost inductor;
A rectifying element that prevents backflow of current from the switching element;
A smoothing capacitor for smoothing the energy output from the boost inductor;
An inductor current detection circuit for detecting the inductor current by a current detection element inserted in a path of an inductor current flowing through the boost inductor;
An input voltage detection circuit for detecting an input voltage using one side of the input power supply as a reference potential;
An output voltage detection circuit for detecting an output voltage to a load using the one side of the input power supply as a reference potential;
A control unit that controls the switching operation based on an inductor current detection result by the inductor current detection circuit, an input voltage detection result by the input voltage detection circuit, and an output voltage detection result by the output voltage detection circuit; Bridgeless power factor correction circuit. The bridgeless power factor correction circuit according to claim 1,
The bridgeless power factor correction circuit, wherein the output voltage detection circuit is composed of a resistor and a differential amplifier. The bridgeless power factor correction circuit according to claim 1,
One end of the current detection element is connected to the reference potential,
The bridgeless power factor correction circuit, wherein the inductor current detection circuit detects the inductor current by measuring a voltage across the current detection element with one side of the input power supply as a reference potential.   The bridgeless power factor correction circuit according to any one of claims 1 to 3, wherein the bridgeless power factor correction circuit is a totem pole / bridgeless power factor correction circuit.

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