JPH06284725A - Push-pull-type power supply - Google Patents

Abstract

PURPOSE:To provide a push-pull-type power supply wherein biased excitation detector which can detect the biased excitation amount of a transformer is provided, the biased excitation of the transformer is reduced to a minimum and the iron core of the transformer is small and lightweight. CONSTITUTION:A push-pull-type power supply is provided with a switching control circuit 10 by which two transistors Q1, Q2 perform a switching operation alternately and with a powersupply transformer 20 which has an intermediate terminal 2 in a primary winding. In the power supply, a current is made to flow to primary windings 2-3, 2-4 for the power-supply transformer in mutually opposite directions, and a direct current is converted into an alternating current. In addition, the power supply is provided with a biased excitation detection transformer 30 having two primary windings 5-6, 7-8, and the respective primary windings are connected in series across two transistors and the power-supply transformer. In addition, the power supply is provided with a detection circuit 32 which detects a biased excitation amount on the basis of the secondary-side output of the biased excitation detection transformer and by which the output is fed back to the switching control circuit.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a power transformer,
More specifically, it relates to a push-pull type power supply mounted on space equipment.

[0002]

2. Description of the Related Art Of the power supply devices, the push-pull type power supply is
It is known as a high-efficiency, high-capacity power supply. The push-pull type power supply has a circuit configuration as shown in FIG. 4, for example, and includes a switching control circuit 10 for alternately switching the transistors Q1 and Q2, primary side terminals 3 and 4, and an intermediate terminal 2. The transformer 20 and the DC power source 12 are provided, and the switching control circuit 10 alternately performs switching operation of the transistors Q1 and Q2, whereby the + pole of the DC power source 12 to the intermediate terminal 2 of the transformer 20 to the primary side terminal 3 to the transistor Q1. Flow from the collector C to the negative pole of the DC power supply 12 (hereinafter referred to as Q1 loop)
And the + pole of the DC power supply 12 to the intermediate terminal 2 of the transformer 20.
A flow (hereinafter, referred to as a Q2 loop) of the primary side terminal 4 to the collector C of the transistor Q2 to the negative electrode of the DC power supply 12 is alternately created, whereby a reverse current is alternately applied to the primary winding of the transformer 20. Then, a desired AC power source is obtained on the secondary side of the transformer 20. The power source installed in space equipment such as artificial satellites is, for example, about 20V to about 30V.
Fluctuates up to. The push-pull type power supply described above is used, for example, to generate an AC power supply from such an unstable DC power supply and then obtain a desired stable DC output by the rectifying circuit 14 and the smoothing circuit 15. Further, the DC output is fed back to the switching control circuit 10 in order to control the product V · T of the voltage V and the time T constant by a feedback loop via the control circuit 16 and the signal insulation element 17 (for example, a transformer or a photocoupler). To be done. FIG. 5 shows waveforms controlled by the transistors Q1 and Q2 in the push-pull power supply. The waveform (A) of the voltage between C and E of Q1 due to the switching operation of the transistor Q1 and the waveform (B) of the voltage between C and E of Q2 due to the switching operation of the transistor Q2 are out of phase with each other by 180 °. It is a waveform, and the product V · T of the waveform voltage V and the time T is constant during normal operation.

[0003]

FIG. 6 shows a transformer 20.
Is a so-called B-H curve, the horizontal axis H in this figure is a magnetic field, which is proportional to the exciting current, and the vertical axis B shows the magnetic flux density. When the product V · T of the waveforms alternately flowing in the primary winding of the transformer 20 is completely coincident with each other, a BH curve (,) symmetrical to the origin of the figure is obtained, but the product is affected by noise or the like. When V · T does not match, the B-H curve deviates from the origin little by little, and the B-H curve shown in, for example, is drawn. Such a phenomenon is known as a biased excitation failure of the transformer. Since the transformer has magnetic saturation, when the partial excitation becomes large and reaches magnetic saturation, the relative permeability of the core decreases to 1 and the impedance on the primary side becomes extremely small, which is almost the same as a short circuit. . For this reason, the current flowing through the Q1 loop or Q2 loop described above becomes extremely large, causing burnout of the primary coil of the transformer, damage to the transistor, etc., and almost no power can be taken out from the output terminal. There was a point. In order to avoid such a problem, in the conventional push-pull power supply, the core (iron core) of the transformer 20 is made large so that the biased excitation and the magnetic saturation are hard to occur. However, such a method has a problem that the push-pull type power source becomes heavy and cannot be mounted on space equipment. The present invention was created to solve such problems. That is, an object of the present invention is to provide a push-pull type power supply including a biased excitation detector capable of detecting the biased excitation amount of a transformer. Another object of the present invention is to provide a push-pull type power supply which can minimize the biased excitation of the transformer. A further object of the present invention is to provide a push-pull type power supply having a small transformer core and a light weight.

[0004]

According to the present invention, a switching control circuit for alternately switching two transistors and a power transformer having an intermediate terminal in the primary winding are provided, and the primary winding of the power transformer is provided. In a push-pull type power supply that alternately supplies current in the opposite direction to convert direct current to alternating current, a bias excitation detection transformer having two primary windings is further provided, and each of the primary windings includes the two transistors. A detection circuit that is connected in series between the power supply transformers and further detects a biased excitation amount from the secondary side output of the biased excitation detection transformer and feeds back the output to the switching control circuit. A push-pull type power supply is provided. According to a preferred embodiment of the present invention, the detection circuit includes a buffer circuit that temporarily stores the secondary side output of the bias excitation detection transformer, and an addition and integration circuit that adds and integrates the secondary side output. Is characterized by.

[0005]

According to the configuration of the present invention, since the bias excitation detection transformer having the two primary windings is provided and each of the primary windings is connected in series between the two transistors and the power transformer, Q flowing in the primary winding of the power transformer
Waveforms proportional to the waveforms of the 1-loop and Q2 loop are always output to the secondary side of the bias excitation detection transformer. Further, according to the present invention, since the detection circuit for detecting the amount of biased excitation from the secondary side output of the biased excitation detection transformer and feeding back the output to the switching control circuit is provided, biased excitation occurs due to the influence of noise, etc. When the waveforms of the loop and Q2 loop do not match, the amount of biased excitation is detected from the difference and fed back to the switching control circuit to control the current waveforms of the Q1 loop and Q2 loop (for example, time T) to control the amount of biased excitation. Can be minimized. With this, it is possible to prevent the biased excitation failure of the transformer, and it is possible to provide a push-pull type power supply having a small transformer core and a light weight.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram of a push-pull power supply according to the present invention. In this figure, a push-pull type power supply according to the present invention is a switching control circuit 10 for alternately switching operating two transistors Q1 and Q2.
And a power supply transformer 20 having the intermediate terminal 2 in the primary winding 3-4, and a current is alternately passed through the primary windings 3-4 of the power supply transformer 20 in the opposite direction to convert direct current to alternating current. Has become. Such a configuration is similar to that of the conventional push-pull type power supply shown in FIG.

Furthermore, according to the invention, the two primary windings 5
The bias excitation detection transformer 30 having -6 and 7-8 is provided. Primary windings 5-6, 7-8 of the bias excitation detection transformer 30
Are two transistors Q1 and Q2 and a power transformer 20.
Are connected in series between the windings 2-3 and 2-4. That is, by alternately switching the two transistors Q1 and Q2, the + pole of the DC power supply 12, the primary winding 2-3 of the power transformer 20, the primary winding 5-6 of the bias excitation detection transformer 30, and the transistor Q1. C
-E to the-pole of the DC power supply 12, the flow (Q1 loop),
+ Pole of DC power source 12-primary winding 2-4 of transformer 20
The flow (Q2 loop) of the primary winding 7-8 of the bias excitation detection transformer 30, the CE of the transistor Q2, and the negative pole of the DC power supply 12 can be alternately created. As a result, a desired AC power source can be obtained on the secondary side of the transformer 20, and at the same time, a waveform proportional to the waveforms of the Q1 loop and the Q2 loop flowing in the primary winding of the power transformer is always supplied to the secondary excitation detection transformer 30. It is possible to output to the secondary winding AB. That is, the bias excitation detection transformer 30 serves as a kind of sensor.

According to the present invention, a detection circuit 32 is further provided which detects the amount of biased excitation from the secondary output of the biased excitation detection transformer 30 and feeds back the output to the switching control circuit. FIG. 2 is a circuit diagram showing an example of the detection circuit 32, and includes a buffer circuit 34 that detects the secondary side output of the bias excitation detection transformer 30 and an addition integration circuit 36 that adds and integrates the secondary side outputs. . Buffer circuit 3
Reference numeral 4 includes an amplifier and a plurality of resistors, and serves to increase the input impedance, reduce the current flowing through the detection circuit 32, and improve the detection accuracy. The integrating / adding circuit 36 is composed of a diode, a capacitor, a resistor, an amplifier, etc., adds the Q1 loop waveform and the Q2 loop waveform, integrates them, and outputs an area difference, that is, a deviation amount between the Q1 loop waveform and the Q2 loop waveform. To do.

FIG. 3 shows an input waveform (A) and an output waveform (B) in the circuit of FIG. When the biased excitation is not generated or is small, the Q1 loop (positive) and the Q2 loop (negative) have substantially the same area as shown by the solid line in the figure, and the output of the integral addition circuit 36 is almost zero. Become. When the bias excitation becomes large, one of the waveforms of the Q1 loop (positive) and the Q2 loop (negative) becomes large, as shown by the broken line in the figure.
The other becomes smaller and the area difference becomes larger, and the output of the integration and addition circuit 36 becomes + (or −) as shown by the broken line in the figure. The output of the integrating and adding circuit 36 is fed back to the switching control circuit 10, and the switching control circuit 10 adjusts the voltage waveform (for example, time T) of the Q1 loop or the Q2 loop to control the biased excitation amount to the minimum. . As a result, it is possible to prevent the bias excitation failure of the transformer. Therefore, there is no risk of partial excitation failure, and the transformer core can be made sufficiently small,
It can be a lightweight push-pull type power supply as a whole.

[0010]

As described above, according to the present invention, the bias excitation detection transformer having the two primary windings is provided, and each of the primary windings is connected in series between the two transistors and the power transformer. Therefore, the waveform proportional to the waveforms of the Q1 loop and the Q2 loop flowing in the primary winding of the power transformer can always be output to the secondary side of the bias excitation detection transformer. Since a detection circuit for detecting the amount of biased excitation from the side output and feeding back the output to the switching control circuit is provided, when biased excitation occurs due to the influence of noise and the waveforms of the Q1 loop and the Q2 loop do not match, the difference The amount of biased excitation is detected and fed back to the switching control circuit to control the voltage waveforms of the Q1 loop and the Q2 loop (for example, time T),
The amount of biased excitation can be minimized, and the biased excitation failure of the transformer can be prevented.

Therefore, according to the present invention, a push-pull type power source is provided which is provided with a bias excitation detector capable of detecting the bias excitation amount of the transformer, minimizes the bias excitation of the transformer, and has a small transformer core and a light weight. can do.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a push-pull power supply according to the present invention.

FIG. 2 is a circuit diagram showing an example of a detection circuit.

3 is a diagram showing an input waveform (A) and an output waveform (B) in the circuit of FIG.

FIG. 4 is a circuit diagram of a conventional push-pull power supply.

FIG. 5 is a diagram showing waveforms in a push-pull power supply.

FIG. 6 is a diagram showing a BH curve of a transformer.

[Explanation of Codes] 2 Intermediate terminal of power supply transformer 3, 4 Primary winding terminal of power supply transformer 5, 6, 7, 8 Primary winding terminal of bias excitation detection transformer 10 Switching control circuit 12 DC power supply 14 Rectifier circuit 15 Smoothing circuit 16 Control Circuit 17 Signal Insulation Element 20 Power Transformer 30 Unbalanced Excitation Detection Transformer 32 Detection Circuit 34 Buffer Circuit 36 Summing Integration Circuit A, B Secondary Winding Terminals of Unbalanced Excitation Detection Transformer Q1, Q2 Transistors

Claims (2)

[Claims] 1. A switching control circuit for alternately switching two transistors and a power supply transformer having an intermediate terminal in a primary winding, wherein a current is alternately passed through the primary winding of the power supply transformer in a reverse direction, In a push-pull type power supply for converting direct current into alternating current, a bias excitation detection transformer having two primary windings is provided, and each of the primary windings is connected in series between the two transistors and the power transformer. The push-pull type power supply further comprising a detection circuit that detects the amount of biased excitation from the secondary side output of the biased excitation detection transformer and feeds back the output to the switching control circuit. 2. The detection circuit comprises a buffer circuit for temporarily storing the secondary side output of the bias excitation detection transformer, and an adding and integrating circuit for adding and integrating the secondary side output. The push-pull power supply according to item 1.