JPS5875472A - Switching regulator - Google Patents

Abstract

PURPOSE:To contrive simplification and cost down for the titled switching regulator by a method wherein a smoothing capacitor to be provided between a rectifier and a series transistor is omitted, and the duty ratio of the series transistor is controlled in the reverse relation to the large and small value of the output voltage instantaneous ratio of the rectifier. CONSTITUTION:An AC power source 1 is rectified by a rectifier 2, connected to the series transistor 4, and power is fed to a DC load 9 without passing through a smoothing capacitor. Then, a switching control is performed on the transistor 4 in such a manner that the duty ratio will become in reverse relation to the large or small output voltage instantaneous value of the rectifier 2 within each half cycle of AC voltage using the saw tooth wave of a delta wave generating circuit 21, the output of a duty ratio mathematic operation circuit 20, and the switching control circuit 11 which will be compared by a comparator 22. As a result, no inteference is encountered on the final output, the capacitor to be provided on the powersource side can be omitted, and the simplification of circuit constitution and cost down of the titled switching regulator can be accomplished.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a switching regulator that uses a rectified voltage as a power source and supplies power to a DC load via a series transistor whose switching is controlled at a high frequency.

[Prior art]

This type of switching regulator generally has the configuration shown in FIG. In the device shown in FIG. 1, the voltage of an AC power source 1 (for example, a commercial power source) is rectified by a rectifier 2, and the rectified voltage is converted into a smoothing capacitor. 3 is applied by a series transistor 4 and switched at a predetermined duty ratio at a repetition frequency of 50 KHz, and the output voltage is transferred to a commutating I/O P6, a smoothing reactor 7 and a smoothing; The smoothed signal is smoothed through a smoothing circuit 5 consisting of a capacitor 8 and then supplied to a DC load 9 . To 2ndji...:
:lj:l"" The duty ratio of the switching performed by the star 4, that is, the duty ratio Dr of the control signal of the transistor 40, is determined by the switching period To, IW as shown in FIG.
! The on time during the U period is t. As long as n and the through pressure Vo are constant, the duty ratio Dr is also the same as that of the switching control circuit 10.
controlled at a constant level.

[Problems with conventional technology]

In the circuit shown in FIG. 1, a smoothing capacitor 3 is connected immediately after the rectifier 2 to smooth the rectified voltage that fluctuates greatly.

However, this capacitor is for DC use, has a high rated voltage, and has a large capacitance, so it is large and expensive, reduces the packaging density of the entire device, and
This was a contributing factor to making the whole thing expensive.

[Purpose of the invention]

The purpose of the present invention is to eliminate the above-mentioned drawbacks, and to simplify the circuit configuration.
An object of the present invention is to provide a switching layer with high packaging density and low cost.

[Summary of the invention]

In order to achieve the above object, the present invention eliminates the smoothing capacitor provided between the rectifier and the series transistor, and at the same time, the duty ratio within each switching cycle of the series trunk transistor is The switching of the series transistors is controlled so as to have an inverse relationship with the temporary value of the output voltage of the rectifier.

[Embodiments of the invention]

FIG. 3 shows an embodiment of the present invention.

AC power supply 1 and rectifier 2 of this switching regulator
, series transistor 4, smoothing circuit 5 (commutating diode-P6
, consisting of a smoothing reactor 7 and a smoothing capacitor 8),
The DC load 9 and the DC load 9 are the same as those in FIG. A special feature of this main circuit configuration is that no smoothing capacitor is provided between the rectifier 2 and the series transistor 4. The series transistor 4 outputs the output voltage of the rectifier 2 (
), the output side voltage of the transistor 4, and the smoothing circuit 5
Based on the output voltage, that is, the load voltage, the switching control circuit 11 performs switching control as described below. The switching frequency is the same as mentioned above (additionally ~50
It is about 1 Gis.

FIG. 4 shows the method of determining the duty ratio in the switching control circuit 11: 1) paddle turn. Here, the period between the zero points of the output voltage a of the rectifier 2, that is, the half period of the AC voltage before rectification is assumed to be Ts. One way to determine the duty ratio e-turn is to make it completely inversely proportional to the voltage a. However, with this method, calculation becomes impossible near the zero point of voltage a, so as shown in the lower half of FIG. -, the maximum value of voltage a is 1rvrn, the time is t, and the duty ratio Dr
Vary according to I. The minimum value Drmln of Dr is. Note that, on the contrary, the layer ml□ may be set first, and Vs t'' may be determined based on it.

Based on the calculation result of the duty ratio, a specific phase point of the next cycle of the AC power supply voltage, for example, the rectified voltage a
It is sufficient to generate a trigger signal at the zero point of and change the duty ratio.

FIG. 5 shows an example of a switching/arm pulse generation circuit that embodies such duty ratio control. The duty ratio calculation circuit 1 is a circuit that calculates the above-mentioned duty ratio Dr based on the voltage a and the input signal 3 (see FIG. 4). This calculation (b) outputs a voltage Vd proportional to the duty ratio Dr, and inputs it to the comparator 22 as a comparison voltage.

The triangular wave generating circuit 21 generates a sawtooth wave voltage St shown in FIG. 6(a). This voltage St is synchronized with the voltage a and oscillates at a frequency equal to the switching frequency of the series transistor 4, for example, 50 KHz, and its maximum value is set to match the value of the voltage Vd when the duty ratio is 100 or more. be done. This voltage 8t is inputted to the router n as a reference voltage. As shown in FIG. 6(b), the converter n outputs a 11' signal in the range let<Va, and outputs a 10' signal in the range at<Vd. In FIGS. 6(a) and 6(b), the right half shows the situation when the value of the voltage Vd is relatively large, that is, near the phase point where the voltage a is relatively low, and the right half shows the situation where the voltage Vd is relatively low.
The situation near the phase point where d is relatively low and therefore the voltage 1 is relatively high is shown. The series transistor 4 is controlled to be turned on in response to the output signal of the cone/regulator 4.

FIG. 6(c) shows the output voltage of the series transistor 4 when switching is controlled in this way. In the left half, the voltage is relatively low, but the on-time width is
It can be seen that in the right half, the voltage is relatively high, but the on-time width is relatively narrow.

What is important here is that, as can be seen from Figure 6 (C), the area of the on section of each switching cycle, that is, the voltage-time product, is almost exactly the same regardless of the voltage level. be. This corresponds to finding the duty ratio Dr f in inverse proportion to the voltage 1, except for the vicinity of the zero point of the AC power supply voltage. Due to this fact, even if the smoothing capacitor immediately after the rectifier is omitted, smoothing after switching becomes easy, and the smoothing ability of the smoothing circuit 5 can be avoided without particularly increasing.

[Modified example of the invention]

FIG. 7 shows an alternative embodiment to FIG. 5.

In this embodiment, the duty ratio of each switching cycle is determined based on the synchronization signal, frequency signal, and voltage signal input from the control signal generation circuit 5, and the duty ratio generation pattern ( For example, as mentioned above, the duty ratio should be inversely proportional to the input voltage, or
In other words, whether or not the area of each output voltage waveform in FIG. 6(C) should be kept approximately constant regardless of the value of the input voltage is an analog test! It is configured to output as a value. Based on the above-mentioned synchronization signal, frequency signal and voltage signal, the Norse oscillation circuit n outputs an output signal similar to the output signal of the comparator 4 based on the output signal of the integer and the voltage V@ (see FIG. 4).

In this example, the only difference is in the signal processing method in the middle.
It is clear that the same control result 1 as that shown in FIG. 5 can be obtained as a result.

Although the above explanation has been made for the case of a single-phase full-wave rectification system, the present invention can of course be applied to other rectifier circuit systems, and is particularly desirable as the number of phases increases because the ripple component decreases. That's true.

[Effects of the Invention] As described above, the present invention eliminates the smoothing capacitor between the rectifier and the series transistor, and also allows the duty ratio of the series transistor within each switching cycle to be equal to or smaller than that of the rectifier within each half cycle of the AC voltage. Switching of the series transistors is controlled so that the relationship is inverse to the magnitude of the instantaneous output voltage value, so there is no major problem with the final output, and the circuit configuration is simplified and costs are reduced by omitting the power supply side capacitor. This makes it possible to provide a switching layer with high packaging density.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram of a conventional switching regulator, Fig. 2 is an explanatory diagram of a duty ratio, Fig. 3 is a circuit diagram of a switching regulator of the present invention, and Fig. 4 is an example of setting a duty ratio according to the present invention. FIG. 5 is a block diagram of a circuit that generates switch pulses and pulses according to the duty ratio shown in FIG. 4, and FIGS.
A signal waveform diagram is used to explain the operation of the circuit shown in the figure, and FIG. 7 is a block diagram showing another embodiment of the circuit shown in FIG. 2... Rectifier, 4... Series transistor, 5...
Smoothing circuit, 11... switching control circuit. Applicant's agent Kiyoshi Inomata:

Claims (1)

[Claims] 1. A rectifier that rectifies AC voltage, a series transistor directly connected to the output side of the rectifier without using a smoothing capacitor, and between the output side of this transistor and a DC load. and a smoothing circuit connected to the series transistors such that the demitty ratio within each switching cycle of the series transistors is inversely related to the magnitude of the instantaneous value of the output voltage of the rectifier within each half cycle of the alternating current voltage. A switching regulator comprising a switching control circuit that controls switching of transistors. 2. The simultaneous switching control includes a triangular wave generation circuit that generates a triangular wave that repeats at a period corresponding to the switching frequency of the series transistor, and a triangular wave generation circuit that generates a triangular wave that repeats at a cycle corresponding to the switching frequency of the series transistor, and a triangular wave generating circuit that generates a triangular wave that repeats at a cycle corresponding to the switching frequency of the series transistor, and a triangular wave generating circuit that generates a triangular wave that repeats at a cycle corresponding to the switching frequency of the series transistor, and a triangular wave generating circuit that generates a triangular wave that repeats at a cycle corresponding to the switching frequency of the series transistor. is characterized in that it includes a duty ratio calculation circuit that outputs a comparison voltage that changes in an inverse relationship, and a connocerator that outputs a switching control signal for the series transistor based on a comparison result between the triangular wave and the comparison voltage. A switching layer generator according to claim 1. 36 The switching control circuit includes a control signal generation circuit that outputs a frequency signal representing the frequency of the output voltage of the rectifier and a voltage signal representing the voltage value, and a control signal generating circuit that outputs a frequency signal representing the frequency of the output voltage of the rectifier and a voltage signal representing the voltage value, and a control signal generating circuit that outputs the frequency signal, the voltage signal, and the rectifier output stored in advance. Claim 1, characterized in that it includes a circuit that outputs a switching pulse according to an instantaneous voltage value vs. duty ratio curve, and a pulse oscillation circuit that outputs a switching control signal for the series transistor based on the switching pulse. The switching layer generator described in item 1.