JP2006187140A - Converter power supply circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accommodate high power while operating a power-factor improvement converter in a current discontinuity mode. <P>SOLUTION: Between a low-pass filter 103 for smoothing a rectified AC power supply 101 and an output smoothing capacitor 112, a plurality of unit chopper circuits are connected in parallel to each other, one of which consists of a serial connection of a chalk coil L and a forward diode D and a switching transistor connected between a junction of the chalk coil L and the diode D and a ground. To keep a terminal voltage of an output smoothing capacitor, the respective switching transistors are constituted so as to have selective polyphase driving at the same frequency and with a driving signal having such a different phase as to cause no overlapped driving timing. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a converter power source of a power factor correction converter type that is configured to boost a voltage obtained by rectifying and smoothing an AC power source with a boost chopper, smooth it with a smoothing capacitor, and then supply it to a load. It is related with the converter power supply circuit which enabled multiphase drive.

  In general, power factor correction converters (PFCs) are roughly classified into operation methods, namely, a current discontinuous mode and a current continuous mode, which are selectively used depending on the magnitude of load power.

  That is, the current discontinuous mode is generally applied for small and medium power, and the current continuous mode is generally applied for medium and large power. The current discontinuous mode has a feature that the generation of noise is small, and the current continuous mode has a feature that the operation of the switching transistor becomes hard switching and the noise generation becomes large.

  In recent electronic devices, there are a variety of devices ranging from devices with low power consumption to devices with large power consumption, and power supply circuits corresponding to each of them are applied.

  However, some electronic devices can be switched from a small power consumption state to a large power consumption state, and a power supply circuit corresponding to a wide power range may be required.

  On the other hand, from the viewpoint of cost reduction, consideration is also given to the common use of circuits, and there is a demand for the realization of a power supply circuit corresponding to a wide power range with the same circuit.

  When the power factor correction converter is applied to the power supply circuit, it is necessary to change the operation mode depending on the power consumption as described above, and in the current continuous mode corresponding to the high power, the generation of noise increases. For example, it is not preferable to be applied to a television receiver that is easily received. In other words, if noise is mixed in the video signal or audio signal, the quality of the displayed image may be deteriorated or the image may be disturbed. In the case of noise, the noise may be annoying and the audio may be difficult to hear. .

  Further, in the current continuous mode, there is a possibility that EMC (Electromagnetic Compatibility) may be impaired, and noise that interferes with other devices may be generated.

  Therefore, although there is a strong demand for the realization of a power supply circuit that can provide a large amount of power in the current discontinuous mode with less noise generation, it has not been realized yet.

Many proposals have been made as power factor improving converters. For example, Patent Document 1 discloses a proposal in which a harmonic current is suppressed by combining a power factor improving converter and a DC-DC switching power supply. It does not support a wide range of power consumption.
JP 2002-101660 A

  As described above, in the conventional power factor correction converter, if it is operated in the continuous current mode that can output a large amount of power, a lot of noise is generated. It was necessary to avoid using it in an environment where there was a device affected by

  The present invention has been made in view of the above points, and an object of the present invention is to provide a converter power supply circuit that operates in a current discontinuous mode and can handle a large amount of power.

  The converter power supply circuit according to the present invention comprises an AC power supply, a rectifying / smoothing means for converting the AC power supply into DC, a boosting chopper connected in parallel to the output terminal of the rectifying / smoothing means, and smoothing the output of the boosting chopper. In the converter power supply circuit composed of a smoothing capacitor that supplies a load to the load, the boost chopper is connected in series between a choke coil and a forward diode, and connected between the connection point of the choke coil and the diode and a reference potential point. A unit circuit composed of an element is configured as a plurality of circuits connected in parallel between the rectifying / smoothing means and the smoothing capacitor, and the plurality of switching elements are arranged so that the terminal voltage of the smoothing capacitor becomes a predetermined value. Provided with control means for switching by drive signals having a constant frequency and different phases And wherein the door.

  According to the present invention, it is possible to realize a converter power supply circuit with less noise generation corresponding to high power consumption.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a circuit block diagram of a converter power supply circuit of the present invention.

  In FIG. 1, a converter power supply circuit 100 includes a full-wave rectifier 102 that rectifies an AC power supply 101 and a low-pass filter 103 that smoothes the output of the full-wave rectifier 102. The low-pass filter 103 includes a choke coil 104 connected in series to the output terminal of the full-wave rectifier 102, and capacitors 105 and 106 connected between both ends of the choke coil 104 and a reference potential point (grounding point). Composed.

  The output of the low-pass filter 103 is connected to the chopper circuit group 107. The chopper circuit group 107 includes, for example, four chopper circuits 108, 109, 110, and 111 connected in parallel, and the chopper circuits 108 to 111 are configured as exactly the same circuit.

  That is, the chopper circuit includes a series connection of a choke coil L (1-4) connected in series to the output terminal of the low-pass filter 103 and a forward diode D (1-4) having an anode connected to the choke coil L. The switching transistor (FET: Field Effect Transistor) Q (1 to 4) is connected between the connection point of the choke coil L and the diode D and the reference potential point.

  The cathodes of the diodes D1 to D4 of the chopper circuits 108 to 111 are connected to a reference potential point through a parallel connection of the smoothing capacitor 112 and the load 113.

  Furthermore, a voltage detector 114 that detects the terminal voltage of the smoothing capacitor 112 is provided, and detects the difference between the terminal voltage of the smoothing capacitor 112 and the reference voltage Vr.

  The detection result of the voltage detection unit 114 is supplied to the control circuit 115, and the control circuit 115 controls the drive circuit 116 based on the detected differential voltage value. The drive circuit 116 outputs a drive signal for turning on and off the switching transistors Q1 to Q4 of the chopper circuits 108 to 111. Each of the switching transistors Q1 to Q4 is turned on and off at a predetermined timing according to the detection result of the voltage detection unit 114. Is switched.

  The drive signals output from the drive circuit 116 are signals having the same frequency and only different phases, thereby driving the switching transistors Q1 to Q4 so that the ON periods do not overlap.

  Furthermore, if the terminal voltage of the smoothing capacitor 112 is low, all the switching transistors Q1 to Q4 are driven so that all the chopper circuits 108 to 111 operate. If the terminal voltage of the smoothing capacitor 112 is high, all the chopper circuits are driven. For example, only three chopper circuits are operated, or two chopper circuits are driven so as to correspond.

  The individual circuits of the chopper circuits 108 to 111 are well-known circuits and will not be described in detail. However, the operation will be briefly described. When the switching transistors Q1 to Q4 are on, the choke coils L1 to L4 are turned on. The stored energy operates so as to be superimposed on the input voltage and supplied to the smoothing capacitor 112 when the switching transistors Q1 to Q4 are turned off.

  FIG. 2 is a timing chart for explaining the drive signal output from the drive circuit 116 in accordance with the detection result of the voltage detection unit 114.

  FIG. 2A shows a drive signal when the terminal voltage of the smoothing capacitor 112 is considerably lower than the reference voltage Vr. That is, in this state, the drive circuit 116 outputs a drive signal for driving the switching transistors Q1 to Q4 to operate all the chopper circuits 108 to 111.

  That is, it is operated in a so-called four-phase drive state. Each drive signal is a pulse train having the same period ts but having a different phase, and rises at a timing that does not overlap each other to turn on the switching transistors Q1 to Q4. The timing at which each drive signal rises is 90 ° different in phase when each cycle is 360 °.

  FIG. 2B shows a driving signal in a so-called three-phase driving state in which only the chopper circuits 108 to 110 are operated, and the fourth driving signal is not output at all. In the case of three-phase driving, the switching transistors Q1 to Q3 are driven to be turned on at different timings of 120 degrees.

  FIG. 2C shows a drive signal in a so-called two-phase drive state in which only the chopper circuits 108 and 110 are operated, and the second and fourth drive signals are not output at all. In the case of two-phase driving, the switching transistors Q1 and Q3 are driven to be turned on at different timings of 180 degrees.

  FIG. 3 is a characteristic diagram for explaining the operation of the converter power supply circuit 100 shown in FIG. 1. The horizontal axis indicates time (t), and the vertical axis indicates voltage (V) and current (I).

  In FIG. 3, iin indicates an alternating current averaged by the low-pass filter 103 and approaching a sine wave (power factor improved). Further, iL indicates a current waveform in which the currents of the choke coils L1 to L4 of the chopper circuits 108 to 111 are combined. Furthermore, Vin is a waveform of a voltage output from the AC power supply 101 and indicates, for example, a half cycle of 50 Hz. Further, Vout is an output voltage and indicates a terminal voltage of the smoothing capacitor 112.

  FIG. 4 shows the reduction ratio of the ripple current by the chopper circuit. In this case, it is assumed that two chopper circuits similar to FIG. 1 are additionally connected in parallel to FIG. . In FIG. 4, the horizontal axis indicates the duty cycle, and the vertical axis indicates the input current value.

  When two chopper circuits are driven (NPH = 2) compared to the case where there is one chopper circuit (NPH = 1), the ripple current is halved and three chopper circuits are driven. In the case (NPH = 3), the ripple current is shown to be 1/3. When four chopper circuits are driven (NPH = 4), five chopper circuits are driven (NPH = 5), and six chopper circuits are driven (NPH = 6), the ripple current Are shown to be 1/4, 1/5, and 1/6, respectively.

  Next, effects of the converter power supply circuit 100 according to the present invention described above will be described. First, the ripple current of the smoothing capacitor 112 is reduced. For example, when two chopper circuits are driven, it is equivalent to a single chopper circuit configured to double the drive frequency. When four chopper circuits are driven, the drive frequency Is equivalent to 4 times.

  Next, there is an effect that the load fluctuation response characteristic becomes faster. For example, when two chopper circuits are driven, it is equivalent to one chopper circuit configured by doubling the drive frequency. When four chopper circuits are driven, the drive frequency is Is equivalent to 4 times.

  Further, the output voltage ripple is reduced. For example, when two chopper circuits are driven, it is equivalent to one chopper circuit configured by doubling the drive frequency. When four chopper circuits are driven, the drive frequency is Is equivalent to 4 times.

  Further, by using a plurality of chopper circuits, the current flows in a distributed manner in each circuit, so the current per component is reduced. In addition, the amount of heat generated by each circuit component is reduced, and it is possible to use a component having a low heat resistance rating. Also, when a heat radiating plate is applied, there is no need to exhibit a high heat radiating effect, so there is an effect that a circuit can be configured at low cost.

  The greatest effect of the converter power supply circuit according to the present invention described above is that it is possible to cope with high power in the current discontinuous mode only by increasing the number of chopper circuits having the same circuit configuration.

  In other words, each chopper circuit operates in a current discontinuous mode, but a plurality of chopper circuits are connected in parallel and operate in different phases. Will be output. That is, it is possible to obtain a converter power supply circuit corresponding to high power with little noise generation.

  Next, another embodiment of the converter power supply circuit of the present invention will be described with reference to the timing chart of FIG. In this embodiment, the generation timing of the drive signal output from the drive circuit 116 is slightly changed.

  That is, FIG. 5A shows a slight change of the rising timing of the first drive signal so as to return to the original in three cycles in the two-phase drive state. The interval between the first drive signals is set shorter by t0 than the standard ts, the interval between the next drive signals is the standard ts, and the interval between the next drive signals is longer by t0 than the standard ts. Is set. It is repeated thereafter.

  In this way, by slightly varying the generation timing of the drive signal, the frequency spectrum does not become an extreme peak at the standard frequency but has a width, so that the generation of noise can be suppressed. It is.

  FIG. 5B is a diagram in which the rise timing of the second signal of the drive signal for the two-phase drive is slightly changed alternately every cycle. That is, the interval between the first drive signals is set shorter by t0 than the standard ts, and the interval between the next drive signals is set longer by t0 than the standard ts. It is repeated thereafter.

  As shown in FIG. 5B, by correcting the generation timing of the drive signal, the frequency spectrum of the drive signal does not become an extreme peak but has a width as in FIG. 5A. Generation of noise can be suppressed.

  As described above, according to the converter power supply circuit of the present invention, a plurality of chopper circuit portions of the power factor correction converter are connected in parallel so that each chopper circuit has a predetermined frequency and a phase that does not overlap the on period. Driving with different drive signals, combining the output of each chopper circuit and supplying it as output power supply, it is possible to realize a circuit corresponding to high power while operating in the current discontinuous mode. .

  In addition, since the circuit configuration is such that a plurality of unit chopper circuits each composed of a choke coil, a diode, and a switching transistor are simply connected in parallel, the manufacturing is simple and the cost can be kept low.

  Furthermore, since the drive circuit only outputs a drive signal having a single frequency while changing the phase, there is an effect that a complicated configuration is not required.

  The present invention can be variously modified without departing from the gist thereof, and the number of chopper circuits connected in parallel is not limited to four or six as described in the embodiment.

The circuit block diagram shown in order to demonstrate one Embodiment of the converter power supply circuit concerning this invention. FIG. 2 is a timing chart for explaining the operation of the converter power supply circuit shown in FIG. 1. The characteristic view shown in order to demonstrate operation | movement of the converter power supply circuit shown in FIG. The characteristic view shown in order to demonstrate operation | movement of the converter power supply circuit shown in FIG. The timing diagram shown in order to demonstrate operation | movement of other embodiment of the converter power supply circuit concerning this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 ... Converter power supply circuit 101 ... AC power supply 102 ... Full wave rectifier 103 ... Low pass filter 107 ... Chopper circuit group 108,109,110,111 ... Chopper circuit 112 ... Smoothing capacitor 113 ... Load 114 ... Voltage detection part 115 ... Control circuit 116 ... Drive circuit

Claims (2)

An AC power supply, a rectifying / smoothing means for converting the AC power into DC, a boost chopper connected in parallel to the output terminal of the rectifying / smoothing means, and a smoothing capacitor for smoothing the output of the boost chopper and supplying it to a load In the configured converter power supply circuit,
The step-up chopper includes a unit circuit composed of a series connection of a choke coil and a forward diode and a switching element connected between a connection point of the choke coil and the diode and a reference potential point between the rectifying and smoothing means and the smoothing capacitor. It is configured as multiple circuits connected in parallel,
The converter power supply further comprising control means for switching the plurality of switching elements with drive signals having a constant frequency and different phases so that a terminal voltage of the smoothing capacitor becomes a predetermined value. circuit.   The converter power supply circuit according to claim 1, wherein the control unit is configured to change a phase of a drive signal supplied to a specific switching element at a predetermined period.

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