JPS61132071A - Power source - Google Patents

Abstract

PURPOSE:To suppress harmonic currents by applying a pulsating voltage from a rectifier to a DC/DC converter without smoothing. CONSTITUTION:An AC voltage supplied through a noise filter 2 from an AC power source 1 is full-wave rectified by a rectifier 3, and applied as a pulsating voltage to a DC/DC converter 4. A modulator 9 generates a drive pulse of the prescribed width by setting a voltage regulator 10, and applied to the base of a transistor 5 in the converter 4. Thus, a transistor 5 starts switching. Thus, a DC voltage is obtained across a smoothing condenser 8, and supplied to a load RL.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a power supply device that converts alternating current voltage from a commercial power source into direct current voltage, and particularly relates to a power supply device that aims to reduce the amount of harmonic current generated.

[Technical background of the invention and its problems] Home appliances such as televisions, radios, stereos, and microwave ovens are equipped with power supplies (AC/DC conversion circuits) that convert AC voltage to DC voltage.

Furthermore, with the recent development of power electronics, inverter circuits have come to be used for all speeds of induction motors, and an AC/DC converter circuit similar to the above is also disposed in the preceding stage of this inverter circuit.

The general circuit configuration of this AC/DC conversion circuit is shown in FIG. 1 is an AC power supply including a power transmission system, D is a rectifier fi (generally consisting of a group of bridge-connected silicon diodes) that performs full-wave rectification of the AC voltage from this AC power supply 1, and C is a This is a smoothing capacitor that smoothes the wave-rectified voltage, and the voltage across the smoothing capacitor C is applied to the load RL as a DC voltage.

By the way, as shown in Fig. 3, in an AC/DC converter circuit in which a smoothing capacitor C is connected immediately after the rectifier, the impedance of the circuit is non-linear with respect to the power supply voltage, so the AC power supply 1 is A wave current flows.

FIG. 4 is a waveform diagram showing the relationship between the current flowing through the AC power supply 1 and the power supply voltage in the circuit of FIG.

Because harmonic current (odd order) is generated, the voltage waveform VL
In contrast, the current waveform becomes as shown by iL.

This harmonic current not only distorts the voltage waveform of the AC power supply 1, but also causes various failures such as overheating of the power factor correction capacitor, burnout of the series reactor, and malfunction of protective relays such as reverse phase detectors and earth leakage circuit breakers. cause For this reason,
Measures to reduce harmonic current are extremely important.

However, many small and medium capacity devices do not have any reduction measures in place, especially home appliances. This is because home appliances have low power consumption and each device has little impact on the power system.

However, in the case of home appliances, the number of units used is large, and the times of use tend to be concentrated, so measures to reduce harmonic current cannot be ignored, and such measures are strongly desired. ing.

[Object of the Invention] The present invention has been made in view of the above circumstances, and its object is to provide a power supply device that generates an extremely small amount of harmonic current.

[Summary of the Invention] A summary of the present invention for achieving the above object is that the pulsating voltage from the rectifier is applied to the DC-DC converter section without intervening a smoothing means for smoothing the pulsating voltage. This is intended to reduce the amount of harmonic current generated.

[Embodiments of the invention] Hereinafter, the present invention will be specifically explained with reference to Examples.

FIG. 1 is a circuit diagram of a power supply device according to an embodiment of the present invention. 2 is a noise filter, which will be described later.
It functions to prevent switching noise generated from the converter section from flowing out to the AC power supply 1 side, that is, to the power transmission system.

3 is a rectifier that outputs a pulsating voltage Ei by full-wave rectifying the AC 1 m pressure inputted through the noise filter 2, and 4 is a rectifier that outputs a pulsating voltage Ei from the rectifier 3 by smoothing it to a switched voltage. , a DC-DC converter section that outputs a DC voltage Eo that is applied to the load RL.

This DC-D, C converter section 4 is connected between a switching element such as a transistor 5 connected to the cathode of the rectifier 3, an emitter of the transistor 5, and an anode side of the rectifier 3. a diode 7 whose cathode side is connected to the emitter of the transistor 1□5;
and a smoothing capacitor 8 connected between the 7 node side of this diode 7 and the anode side of the rectifier 3. Further, 9 is a modulation circuit that outputs a pulse-like drive signal (hereinafter referred to as a drive pulse) to the base of the transistor 5, and 10 is a circuit that changes the pulse width (duty ratio) of the drive pulse output from this modulation circuit 9. Therefore, the DC voltage E from the DC-DC converter 4.

This is a voltage regulator that adjusts the value of .

Next, the operation of the embodiment device having the above configuration will be explained.

The AC voltage supplied from the AC type 1111 via the noise filter 2 is full-wave rectified by the rectifier 3, and is input to the DC''-DC converter section 4 as a pulsating voltage E1.

On the other hand, the modulation circuit 9 generates a drive pulse having a predetermined pulse width according to the setting of the voltage regulator 10 and applies this to the base of the transistor 5 in the DC-09 converter 4 . ,
As a result, the transistor 5 starts a switching (opening/closing) operation.

Now, assuming that the transistor 5 is turned on for a time of Ton, the coil 6 has (1/2) L ((e/L) - Ton) 2
...-(1) L, :: The energy of the inductance of the coil 6 is stored. Note that during this period, the diode 7 is turned off due to reverse bias.

Next, when the transistor 5 is turned off, the current flows from the load RL side in the forward direction of the diode 7 due to the property of the coil 6 that causes the current to continue flowing. At this time, the energy previously stored in the coil 6 is released. Therefore, the smoothing capacitor 8 is charged to the illustrated polarity.

By repeating the above operations, a DC voltage EO is obtained across the smoothing capacitor 8, and this is supplied to the load RL.

Here, if the switching frequency of the transistor 5 and the duty ratio of the drive pulse are constant, and the switching frequency of the transistor 5 is sufficiently higher than the frequency of the AC power supply 1, then the DC-DC converter The power supplied to the section 4 is proportional to the square of the instantaneous value of the voltage at the AC power supply 1. If, for example, a resistive load is connected to the AC power source 1, the power is proportional to the square of the voltage, so the device of this embodiment is equivalently a resistive load when viewed from the AC power source 1. If it is a resistive load, no harmonic current will occur.

FIG. 2 shows the waveforms of the current 1iLt flowing through the AC power supply 1 and the power supply voltage VL when the device of this embodiment is operated. As is clear from the figure, iLt and VL are in the same phase, which means that no harmonic current is generated.

Note that by changing the duty ratio of the drive pulse from the modulation circuit 9 using the voltage regulator 1o, the value of the DC voltage E0 can be changed. Further, although switching noise is generated due to the switching operation of the transistor 5, this noise is blocked by the noise filter 2, so that it does not flow into the AC power supply 1.

In this way, in the device of this embodiment, the pulsating voltage output from the rectifier 3 is applied to the DC-DC converter section 4 without intervening a smoothing means (for example, a smoothing capacitor) for smoothing the pulsating voltage. Then, this pulsating voltage is transferred to transistor 5.
After switching, the DC voltage is obtained by smoothing by the smoothing capacitor 8, and the output of the rectifier is not directly smoothed by the smoothing capacitor C as the smoothing means as in the conventional method (Fig. 3). The impedance is never nonlinear with respect to the power supply voltage, so no harmonic currents occur. Moreover, by placing the noise filter 2 in the circle between the AC power supply 1 and the rectifier 3,
Switching noise generated by the switching operation of the transistor 5 in the DC-DCC comparator part 1 can be prevented from flowing into the AC power supply 1.

Although one embodiment of the present invention has been described above, it goes without saying that the present invention is not limited to the above-mentioned embodiment, and can be modified as appropriate within the scope of the gist of the present invention.

Although the DC-DC converter section 4 in the above embodiment is of a so-called non-insulated type, it can also be of an insulated type using a transformer.

Further, in the above embodiment, the transistor 5 is used as a switching element, but an MO8 type FET or a GTO
can also be applied.

Furthermore, in FIG. 1, the voltage across the load RL (that is, the DC voltage Eo) is divided and detected, this voltage is compared with a reference voltage, and the modulation circuit 9
The duty ratio of each drive pulse may be feedback-controlled. In this way, the DC voltage E
o can be stabilized.

[Advantageous Effects of the Invention 1] As described in detail above, according to the present invention, it is possible to provide a power supply device that generates an extremely small amount of harmonic current.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram of a power supply device according to an embodiment of the present invention;
The figure is a waveform diagram showing the relationship between the current flowing in the AC power supply and the power supply voltage when the power supply shown in Figure 1 is operated, Figure 3 is a circuit diagram of an AC/DC conversion circuit that is a conventional power supply, and Figure 4 4 is a waveform diagram showing the relationship between the current flowing through the AC i power source and the power supply voltage in the circuit of FIG. 3. FIG. 3... Rectifier, 4... DC-DC converter section, C...
- Smoothing capacitor (smoothing means).

Claims (1)

[Claims] A power supply device comprising a rectifier that rectifies an AC voltage to output a pulsating voltage, and a DC-DC converter unit that can output a DC voltage by switching and smoothing an input voltage, wherein the pulsating voltage is smoothed. The pulsating voltage from the rectifier is adjusted to
- A power supply device characterized by applying voltage to a DC converter section.