JPH04109871A - Rectifying and smoothing device - Google Patents

Abstract

PURPOSE:To improve an input power factor, and to reduce a harmonic wave component of an input current by reducing a pause period of the input current from an AC power source. CONSTITUTION:When a switching element Q1 is ON and a switching element Q2 are OFF, a current i1 flows from an AC power source in a circuit of a rectifier circuit DB, a diode D1, the element Q1, a capacitor C2, a rectifier circuit DB, and the power source AC to charge the capacitor C2. In this case, a current i2 flows from the capacitor C1 through the diode D1 and the element Q1, and the charge of the capacitor C1 is discharged. On the other hand, when the element Q1 is OFF and the element Q2 is ON, a current i1 flows from the power source AC in a circuit of the rectifier circuit DB, the capacitor C1, the element Q2, a diode D2, the rectifier circuit DB and the power source AC to charge the capacitor C1. In this case, a current i2 flows from the capacitor C2 through the element Q2 and a diode D2 to discharge the charge of the capacitor C2.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a rectifying and smoothing device that receives a commercial AC voltage as an input and obtains a DC voltage to a smoothing capacitor.

[Prior Art] Conventionally, an inverter lighting device as shown in FIG. 7 has been widely used as a device for lighting a discharge lamp at high frequency.

In this device, when the AC power source AC is turned on, the switching element Q2 for oscillation is triggered by the starting circuit 4 to start self-excited oscillation, and after that, the resonant choke L
An oscillating voltage is induced in the winding '++12+ni' wound around 2, and the oscillation switching elements Q, Q2 are alternately controlled on and off via the base resistors R1 and R2, respectively, and the resonant choke L2 , the discharge lamp La is lit by the vibration energy of the resonant circuit of the capacitor C4. Here, the capacitor C1 is a coupling capacitor for cutting direct current, and the diodes D s and D
4 is a flywheel diode.

In this conventional example, an AC power source AC is rectified by a rectifier circuit DB, and a DC power source smoothed by a smoothing capacitor C0 is used as an input power source for an inverter circuit. Therefore, since the envelope of the high-frequency current supplied to the discharge lamp La does not vary with the commercial AC cycle, the re-ignition phenomenon of the discharge lamp La is substantially eliminated, the luminous efficiency of the discharge lamp La is improved, and the device It is possible to improve the power consumption of the lighting device, reduce the power consumption of the device, and eliminate flickering of light, thereby improving the performance of the lighting device.

[Problems to be Solved by the Invention] However, when the commercial power supply AC is rectified and smoothed by the rectifier circuit DB, the smoothing capacitor C8 is removed from the commercial power supply AC.
The current Iin flowing into the input current Iin flows only near the peak value of the commercial AC voltage Vin, and as shown in FIG. As a result, the input power factor is poor, and since it contains many high-order harmonic current components relative to the AC fundamental frequency, it has negative effects such as mixing in high-frequency noise to other equipment connected to the same AC power distribution system. there were.

The present invention has been made in view of these points, and its purpose is to provide rectification that reduces distortion of input current from an AC power source and reduces high-order harmonic current components flowing through the AC power source. An object of the present invention is to provide a smoothing device.

[Means for Solving the Problems] In the present invention, in order to solve the above problems, the first
As shown in the figure, a rectifier circuit DB that rectifies the alternating current power supply AC
At the output terminal of
and a series circuit of second capacitors C,,C2 are connected in parallel, and the connection point of the first and second switching elements Q,,Q2 and the connection point of the first and second capacitors C,,C, are connected to the first and second switching elements Q, ,Q.

A smoothing capacitor Co is connected in parallel with the series circuit of the first and second switching elements Q1. The present invention is characterized in that it includes a control circuit 2 that alternately drives Q2 on and off at a switching frequency higher than the power frequency of the AC power supply.

[Effect] Figure 2 (8) shows the action of the rectifying and smoothing device shown in Figure 1.

This will be explained using (b).

First, when the switching element Q1 is on and the switching element Q2 is off, as shown in FIG.
A current 11 flows from the AC power supply AC through the rectifier circuit DB, diode D3, switching element Q1, and capacitor C2. Also, from capacitor C to diode D1. A current 12 flows through the switching element Q1, and the voltage of the capacitor C1 is discharged.

Next, when the switching element Q is off and the switching element Q2 is on, as shown in FIG. 2(b),
A current 11 flows from the AC power supply AC through the rectifier circuit DB, capacitor C3, switching element Q2, and diode D2. Also, from the capacitor C2 to the switching element Q
2. Current 12 flows through diode D2, and the accumulated charge in capacitor C2 is discharged. Therefore, from the viewpoint of the AC power supply AC, the switching element Q1. Q2
This means that the input current 11 always flows in every switching period of , the rest period of the input current Iin is reduced, and the distortion of the input current is improved.

The more detailed structure and operation of the present invention will become clearer in the following description of the embodiments.

[Example 1] FIG. 1 is a circuit diagram of a first embodiment of the present invention.

The circuit configuration will be explained below. The alternating current power supply AC is connected to an alternating current input terminal of a rectifier circuit DB formed of a diode bridge or the like. A smoothing capacitor C0 is connected to the DC output end of the rectifier circuit DB via an input waveform improving circuit 1. A DC-driven load 3 is connected in parallel to the smoothing capacitor C0. In input waveform improvement circuit 1,
A series circuit of diode D1, switching element Q, Q2, and diode D2 is connected to the output terminal of rectifier circuit DB, and a series circuit of capacitors C+ and C2 is connected in parallel, and smoothing capacitor C0 is connected to switching element Q.
It is connected in parallel to the series circuit of L and Q2.

The connection point of switching elements Q, , Q, is capacitor C+
, is connected to the connection point of C2. Each of the switching elements Q, , Q2 is made of a bipolar transistor, and is driven on and off alternately by a control signal from the control circuit 2 via base resistors R, , R2.

The AC power supply AC generates a sine wave AC voltage Vin at a commercial frequency (50Hz or 60Hz), and the control circuit 2 alternately turns on and off the switching elements Q, Q2 at a switching frequency sufficiently higher than this commercial frequency. It is driven off.

FIGS. 2(a) and 2(b) are circuit diagrams for explaining the operation of this embodiment. First, when switching element Q is on and switching element Q2 is off, as shown in FIG.
), as shown by the solid line, the rectifier circuit DB is connected from the AC power supply AC to the rectifier circuit DB.
, diode D1, switching element Q1, capacitor C2, rectifier circuit DB, and AC power supply AC, current 11 flows to charge capacitor C2. At this time, the second
As shown by the broken line in Figure (a), a current 12 flows from the capacitor C1 through the diode D and the switching element Q, and the charge in the capacitor C7 is discharged. Furthermore, the smoothing capacitor C6 is charged with the charging voltage (■) of the smoothing capacitor C8, regardless of whether the switching elements Q, Q2 are on or off. 0 is lower than the pulsating voltage obtained at the output of the rectifier circuit DB, a charging current i, as shown by the broken line, flows.

Next, when the switching element Q1 is off and the switching element Q2 is on, as shown by the solid line in FIG.
1. Current 11 flows through the path of switching element Q2, diode D2, rectifier circuit DB, and AC power supply AC, and capacitor C1 is charged. At this time, as shown by the broken line in FIG. 2(b), from the capacitor C2 to the switching element Q
2. Current 12 flows through diode D2, and the charge in capacitor C2 is discharged. Also, smoothing capacitor C
0, as shown by the broken line, only when the charging voltage VCO of the smoothing capacitor C8 is lower than the pulsating voltage obtained at the output terminal of the rectifier circuit DB, regardless of whether the switching elements Q, Q2 are on or off. A charging current i3 flows. And its charging voltage V. 0 is supplied to load 3.

In this way, by charging and discharging the capacitors C, C2 by turning on and off the switching elements Q, Q2,
Capacitors C, , C over the entire range of input voltage Vin
, a charging current i is caused to flow in from an alternating current power source AC.

The current waveform is shown in FIG.

Current 1 in Figure 3(a). is the charging current waveform of the capacitors C, , C2, and as shown, a whisker-shaped high frequency current flows over the entire range of the input voltage Vin in accordance with the switching period of the switching elements Q, , Q. Further, the current i is a charging current waveform of the smoothing capacitor C6. A current waveform obtained by combining these two input current waveforms is shown in FIG. 3(a). In the actual circuit, a filter circuit is used to shape the input current waveform from the power supply circuit K as shown in FIG. 3(b), so the AC power supply A
The waveform of the input current Iin from C has a waveform close to a sine wave, as shown in FIG. 3(c). Comparing this with the conventional waveform of the input current Iin shown in FIG. 8, it can be seen that an input current waveform with less distortion and a high power factor can be obtained. In addition, the load 3 is supplied with a DC voltage (■) with few pulls as shown in Fig. 4. 0 can be supplied. If the input voltage from the AC power supply AC is Vin=E-sin(ωt),
DC voltage V. The peak value of 0 is approximately (2E).

[Example 2] FIG. 5 is a circuit diagram of a second embodiment of the present invention.

In this embodiment, the switching elements Q, . . . Q2 of the inverter circuit 5 surrounded by broken lines are replaced with the switching elements Q, . . . Q of the input waveform improvement circuit 1 described in the first embodiment.

It is shared with The circuit configuration of the inverter circuit 5 is the seventh
This is similar to the conventional example shown in the figure.

The operation of this embodiment will be explained below with reference to FIGS. 6(a) and 6(b). Regarding the first flow 'l+'2+j3, as explained in FIG. The circuit 6 also has switching currents i to 4 due to the on/off switching of the switching elements Q, Q2. i, will flow.

First, when the switching element Q is on and the switching element Q2 is off, as shown in FIG. 6(a),
A current 11 flows from the AC power supply AC through the rectifier circuit DB, diode D1, switching element Q, and capacitor C2. Further, a current 12 flows from the capacitor C through the diode D1 and the switching element Q1, and the accumulated charge in the capacitor C1 is discharged. Further, a charging current i flows through the smoothing capacitor C8, and a current i4 flows through the resonant circuit 6 of the inverter circuit 5 in a direction to charge the coupling capacitor C1.

Next, when the switching element Q1 is off and the switching element Q2 is on, as shown in FIG. 11 is played. Also, from the capacitor C2 to the switching element Q2
A current 12 flows through the diode D, and the accumulated charge in the capacitor C2 is discharged. Furthermore, a charging current i flows through the smoothing capacitor C0, and a current 15 flows through the resonant circuit 6 of the inverter circuit 5 in a direction to discharge the accumulated charge in the capacitor C1. Therefore, high-frequency AC power is supplied to the resonance circuit 6 of the inverter circuit 5, and the discharge lamp La can be lit by this power.

Note that the power MO8 is used as the switching elements Q, Q2.
When FETs are used, a parasitic anti-parallel diode is built in between the train and the source, so the flywheel diodes D3 and D- can be omitted.

In addition, it is preferable to insert a filter circuit into the AC power source AC to smooth the current waveform shown in FIG. 3(a) as shown in FIG. 3(c), but even if there is no filter circuit, The effect of reducing the rest period of the input current can be achieved. Further, the filter circuit may be inserted at either the power supply side or the non-power supply side of the rectifier circuit DB.

[Effects of the Invention] Since the rectifying and smoothing device of the present invention is configured as described above, when the first switching element is turned on, the second capacitor is charged by the output of the rectifying circuit, and when the second switching element is turned on, the second capacitor is charged. Similarly, when the second switching element is turned on, the first capacitor is charged by the output of the rectifier circuit;
When the first switching element is turned on, the charge in the first capacitor can be discharged, thereby reducing the rest period of the input current from the AC power supply, improving the input power factor, and reducing harmonics of the input current. This has the effect of reducing the amount of components.

Note that it is advantageous if an inverter circuit is adopted as the load connected in parallel to the smoothing capacitor, and the first and second switching elements are shared as the switching elements of the inverter circuit, since the inverter device can be constructed at a low cost. .

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of the first embodiment of the present invention, FIG. 2 is a circuit diagram for explaining the operation of the same, FIG. 3 and FIG. 4 are operational waveform diagrams of the same, and FIG. 5 is a circuit diagram of the first embodiment of the present invention. Circuit diagram of the second embodiment, No. 6
FIG. 7 is a circuit diagram for explaining the operation of the same as above, FIG. 7 is a circuit diagram of a conventional example, and FIG. 8 is an operation waveform diagram of the same as above. AC is an alternating current power supply, DB is a rectifier circuit, D 1. D2 is a diode, Q, C2 is a switching element, CO is a smoothing capacitor, C1 is a first capacitor, C2 is a second capacitor, 1 is an input waveform improvement circuit, 2 is a control circuit, 3
is the load.

Claims (1)

[Claims] (1) A first diode, first and second switching elements, and a second diode are sequentially connected in series so that their forward directions coincide with each other, and The series circuits of the first and second capacitors are connected in parallel, the connection point of the first and second switching elements and the connection point of the first and second capacitors are connected, and the first and second capacitors are connected in parallel.
and a means for connecting a smoothing capacitor in parallel with the series circuit of the second switching element and driving the first and second switching elements on and off alternately at a switching frequency higher than the power frequency of the AC power source. A rectifying and smoothing device comprising: