JPH0258863B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a ringing chain converter type switching regulator, and particularly to a switching regulator based on a detection voltage determined by a predetermined ratio to an AC input voltage. The present invention relates to a switching regulator capable of detecting a voltage drop in its AC input voltage.

[Conventional technology]

Fig. 4 is a circuit diagram of a conventional switching regulator. or connected to an input terminal to which direct current is applied. In the case of DC input, of course, this rectifying and smoothing circuit 1 may be omitted. Primary winding 31 of transformer 3
A transistor 2 is connected in series with the transistor 2, and its base is connected to another winding 32. When AC input is applied, the base current first flows through the starting resistor 21, and the collector current of the transistor 2 begins to flow. Since the windings 31 and 32 are wound with the polarities shown in the figure, a voltage is generated in the winding 31 and a voltage is generated in the winding 32, so that the base current increases.
Therefore, a positive feedback effect occurs in which the collector current also increases, and the transistor 2 is turned on. At this time, a voltage is generated in the secondary winding 33, but since the direction of the diode 51 is reversed, no current flows. Therefore, the collector current of the transistor 2 increases linearly by the inductance of the transformer 3. After transistor 2 is turned on, the base current begins to decrease as the collector current saturates, resulting in a decrease in the collector current, a positive feedback effect opposite to the previous one, and transistor 2 turns off. At this time, the energy stored in the transformer 3 is released, a current flows through the diode 51, and is smoothed by the capacitor 52. A blocking oscillator is constructed in this manner, and direct current is supplied to the load through the rectifying and smoothing circuit 5 connected to the secondary winding 33 of the transformer 3. In addition, 20 is a spike voltage protection circuit for suppressing the spike voltage of the transistor 2, and 25 is a differentiating circuit composed of a current blocking capacitor 23 and a base resistor 24, which prevents the starting current from flowing to the winding 32 side. This prevents it from flowing. Diode 22 is transistor 2
This is to prevent reverse bias.

The above is the basic operation, but the output voltage of this circuit is stabilized by utilizing the fact that the voltage of the winding 32 changes according to the input voltage and output voltage, and using the Zener diode 41 as shown in FIG. , diode 4
2. Control circuit 4 consisting of a capacitor 43 and a resistor 44
A common method was to connect the terminal to apply negative feedback. That is, the voltage of the winding 32 is connected to the diode 42.
The voltage is rectified by the voltage, stored in the capacitor 43, and compared with the voltage at the base to which the Zener diode 41 is connected. When the input voltage becomes higher or the load becomes lighter and the output voltage rises, the voltage on the winding 32 also rises and the anode of the Zener diode 41 is negatively biased. When this exceeds the Zener voltage, the Zener current begins to flow, the current that should flow to the base of the transistor 2 is bypassed, the on-period of the transistor 2 is shortened, and the output voltage is stabilized.

Voltage drop detection in the switching regulator configured as described above is performed by determining the voltage across the capacitor 52 stabilized to DC, or the voltage across the capacitor 64 of the series regulator 6 connected to further stabilize the DC voltage. This is done by comparing the detected voltage.

[Problem that the invention seeks to solve]

However, in conventional switching regulators that detect voltage drops by comparing them with a predetermined detection voltage, for example, when the allowable input voltage is between 90 VAC and 260 VAC, the rated
Whether it is used at 100 VAC or the rated 200 VAC, the voltage detected by the voltage drop detection device will be the same value as, for example, 70 VAC in terms of input.

In other words, a switching regulator is always
Outputs a stabilized DC voltage of 12V DC. If it is determined that an abnormality occurs when this voltage reaches 10V DC, in the conventional voltage drop detection method, 10V DC is calculated as 70V AC in terms of input.
If you are trying to obtain 12V DC with the rated input of 100V AC, you will know that there is an abnormality when the AC input drops to 70%, but with 200V AC
If you are trying to get 12V DC at the rated input, you will know that something is wrong when the AC input drops to 3.5%.

When something like this happens and it is necessary to use AC100V and AC200V as the power supply for the entire system, some equipment will detect a voltage drop and take backup mode, while other equipment will detect the voltage drop and take backup mode. However, the drawback is that the voltage drop is not detected and the process continues as is.

This invention was made in order to eliminate the above-mentioned drawbacks, and is a switching regulator that can correctly detect fluctuations in the supply voltage for both equipment requiring 100V AC power and 200V AC power at the same rate. The purpose is to obtain a rate.

[Means for solving problems]

The switching regulator according to the present invention has a second rectifying and smoothing circuit that rectifies and extracts a voltage of a polarity different from the polarity of the voltage supplied to the first rectifying and smoothing circuit, on the secondary winding side of the transformer. A rectifying and smoothing circuit and a low-pass filter with a large time constant for further stabilizing the output of the rectifying and smoothing circuit are provided, and each output of the low-pass filter and the second rectifying circuit is compared by a comparator.

[Effect]

The comparator in this invention compares the output of the low-pass filter with a large time constant and the output of the second rectifying and smoothing circuit, and for example, when the output of the second rectifying and smoothing circuit is lower than the output of the low-pass filter, AC100V It acts to output a voltage drop detection signal assuming that the voltage has dropped to 70% of the rated voltage power supply of either the system or the AC200V system.

[Embodiments of the invention]

Embodiments of the invention will be described below with reference to the drawings. In FIG. 1, 7 is a second rectifying and smoothing circuit connected to the secondary winding 23, and is composed of a diode 71 and a capacitor 72. This second rectifying and smoothing circuit 7 corresponds to the first rectifying and smoothing circuit 5 consisting of a diode 51 and a capacitor 52, and rectifies and smoothes voltages of different polarities. 81 and 82 are voltage dividing resistors that divide the output voltage of the rectifying and smoothing circuit 7;
A low-pass filter 9 stabilizes the divided voltage output by the voltage dividing resistors 81 and 82, and is composed of a capacitor 91 having a larger capacity than the capacitor 72 and a resistor 92. 100 is a comparator that compares the above-mentioned partial pressure output and the output of the low-pass filter 9.

Note that other circuit parts that are the same as those shown in FIG. 4 are designated by the same reference numerals, and redundant explanation thereof will be omitted.

Next, the operation will be explained.

The transistor 2 connected to the primary winding of the transformer 3 outputs a saw-tooth collector current as shown in FIG. The voltage change of the winding 33 is as shown in FIG. 2b,
Positive and negative voltages that change with 0V as the reference level can be obtained. That is, when the transistor 2 is turned off, the energy stored in the transformer 3 is released to the load side via the diode 5. This is the portion indicated by voltage P in FIG. 2b. As described above in the prior art, the level la of the voltage P is fed back to the primary winding 32 of the transformer 3 to control the on-time of the transistor 2, thereby stabilizing the voltage level la of the voltage P. .

On the other hand, as is well known from the principle of operation of a switching regulator, the level lb of the voltage Q is not stabilized, but varies in proportion to variations in the input voltage. The present invention utilizes this voltage Q level.

That is, in this invention, in order to extract voltage Q, a capacitor 72 and a diode 71 are newly connected as shown in FIG. 1, and the level of voltage Q is smoothed by this capacitor 72 so that it is proportional to the input voltage. A low pass filter 9 which obtains a DC voltage and has a large time constant made of a capacitor 91
, further stabilize the voltage proportional to this voltage,
These two voltage levels are compared by a comparator 100.

FIG. 3 shows the voltage characteristics at the input points R and S of the comparator 100. According to the above circuit, when the AC input voltage drops, the capacitor 72
Since the capacitance of the capacitor 91 is small, the voltage at point R starts to drop immediately, but the voltage at point S starts to drop relatively slowly due to the presence of capacitor 91. As a result, as shown in FIG. The magnitude is reversed, and the voltage drop can be determined from this reversal point.

Then, the voltage levels of input points R and S are respectively
Given l ₁ and l ₂ , l ₂ /l ₁ can be determined by selecting the values of resistors 81, 82, and 92, so whether the AC input voltage is obtained from different power sources such as 100 V AC or 200 V AC, Even if, for example, voltage drops reaching 70% of each of these voltages can be reliably detected.

In addition, when there are only two AC inputs, AC100V system and AC200V system, this selected state is stored in advance in the controller, and the value related to the voltage charged to the capacitor 72 is inputted into the controller, and AC100V is input. system or
If you compare it with the reference value for 200V AC, you will be able to detect a voltage drop at 70% of both 100V and 200V.

In this way, we focused on the fact that among the alternating voltages obtained in the secondary winding 33 of the transformer 3, the voltage level of the polarity, which has not conventionally been involved in voltage stabilization, is proportional to the alternating current input voltage level on the primary side. By detecting this voltage level, it is possible to reliably detect a drop in AC input voltage or a power outage.

〔Effect of the invention〕

As described above, according to the present invention, the second rectifying and smoothing circuit and the low-pass filter are provided on the secondary winding side of the transformer, and the respective output voltages are compared by the comparator.
It is possible to accurately detect voltage fluctuations at a predetermined percentage (for example, 70%) of voltage fluctuations in AC100V systems, AC200V systems, or other voltage systems, and the circuit can be configured easily and inexpensively. Therefore, the effect is that something extremely useful in practice can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a switching regulator according to an embodiment of the present invention, FIG. 2 is a current and voltage waveform diagram of each part of the circuit in FIG. 1, and FIG. 3 is a diagram of input voltage characteristics of a comparator. FIG. 4 is a circuit diagram of a conventional switching regulator. 2 is a transistor, 3 is a transformer, 5 is a first rectifying and smoothing circuit, 7 is a second rectifying and smoothing circuit, 9 is a low-pass filter, and 100 is a comparator. In addition,
In the figures, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] 1 A blocking oscillator is configured by connecting a transistor in series to the primary winding of the transformer, and connecting the base of the transistor to the other winding of the transformer to form a positive feedback circuit, and the secondary winding of the transformer In a switching regulator in which a first rectifying and smoothing circuit for extracting either positive or negative polarity voltage is connected to the line, two of the above transformers are connected.
A second rectifying and smoothing circuit that takes out the voltage of the other polarity is connected to the next winding, and a low-pass filter with a large time constant that stabilizes the output of this second rectifying and smoothing circuit is connected, and this low-pass filter and A switching regulator characterized in that each output level of the second rectifying and smoothing circuit is compared by a comparator.