JPS5815469A - Ac/dc converter - Google Patents

Abstract

PURPOSE:To output a voltage having equal positive and negative amplitudes from an AC/DC converter by providing a tertiary coil at an intermediate tap provided in a transformer and independently providing routes of current when a thyristor is conducted and of reverse high voltage current when the thyristor is interrupted. CONSTITUTION:(N2/N3)Vp=(N2/N1)E is obtained, where Vp: counterelectromotive force when a thyristor is OFF, and E: output of a rectifier 2. That is, the voltage induced in the secondary coil N2 by the voltage of the primary coil N1 of a transformer becomes the same when a thyristor 5 is conducted. Accordinly, a smooth DC voltage having no ripple can be obtained at a load 10 after the voltage is smoothed.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an AO-DC converter. In a converter that converts AO power into the required DC power, the AC power is rectified to Do, which is switched using a high-speed switching element to become A and O at about 25 KHz, and then the AC is rectified by the transformer again. There is a converter that can achieve the desired 4DO using a converter, but this type of converter has the great advantage of being able to reduce the size and weight of the entire device because the transformer is particularly small. However, in devices that use this type of high-speed switching element to convert a single frequency to a high frequency, a high voltage electromotive force is generated in the reverse direction when the high-speed switching element is turned off, so it is necessary to take measures to remove it. Otherwise, some kind of countermeasure had to be taken, such as using electrical parts that could withstand the high voltage output even if they were not removed.

For example, to explain this type of conventional case with reference to Fig. 1, a commercial A, 0 power supply 1 is rectified by a bridge rectifier 2,
The positive output is inputted to one end of the primary coil N1 of the transformer 4, and the other end of the negative coil N1 is grounded via the high speed switching element 5.

6P As the high-speed switching element 5, a gate turn-off switch is used. 3 and 6 are capacitors, and 7 is a circuit for controlling the thyristor 5 described above. A bridge rectifier 8 and an electrolytic capacitor 9 are provided on the secondary side of the transformer 4, so that a predetermined voltage DO is applied to the load. In this circuit, the thyristor 5 is turned on and the output E of the rectifier 2 is transferred to the transformer 4.
A voltage flows through the primary coil N1 and is induced in the secondary coil N2 according to the number of turns of the primary and secondary coils, and when the thyristor 5 is turned off, the electric power accompanying the interruption of the current, that is, the opposite of what was before, is generated. A high-voltage electromotive force is generated in the direction and flows as shown by the arrow in the figure, and the secondary coil N of the transformer naturally receives a voltage of a value corresponding to the turns ratio of the primary coil and the secondary coil, just as in the case of the positive direction described above. It is induced by becoming. Rectifier 2
The reverse electromotive force is quite high compared to the output voltage of 9
If illustrated, it looks like the broken line in FIG. 2 (1). Since such high voltage components are boosted by the transformer, even the direct current appearing on the secondary side of the transformer.

JP-A-58-15469 (2) As shown by the broken line in Figure 2 (2), it exists as a high-voltage ripple component, causing the need to improve the voltage resistance of electrical components, and at the same time causing noise interference to other equipment. This caused negative effects such as

The present invention has been made in view of the above-mentioned drawbacks of the conventional technology.The present invention has been made in view of the above-mentioned drawbacks of the conventional technology.The present invention has been developed by installing an intermediate tap at a suitable number of turns on the input side winding of a transformer to form a primary coil and a tertiary coil. The paths of the reverse high voltage current are made independent, and a constant voltage is induced in the transformer output winding in response to input from either path.
This prevents abnormal ripples from appearing in the transformer output as described in the conventional example.

That is, if the configuration is explained below using an example,
As shown in Figure 6. In FIG. 6, the same reference numerals as in FIG. 1 are the same as or equivalent to those in FIG.

Now, in the circuit shown in Fig. 6, the transformer 4 has an intermediate tap on the input winding, and the primary coil N1 and the tertiary coil N1.
3 and a P secondary coil is formed on the output side winding. The output of the rectifier that rectifies the commercial A, 0 is connected to the center tap of the transformer input winding, and the side of the -order coil other than the center tap is connected to the anode of the thyristor 5, whose cathode is grounded. A switching control circuit 7 is connected to the gate and cathode of this thyristor 5. A series circuit of a diode 11 and a capacitor B is connected between the anode cand of the thyristor 5, and in this case, the diode and the thyristor 5 have the same directionality. Further, a diode 12 is connected between the connection point between the diode 11 and the capacitor 6 and one end of the tertiary coil N3 on the side other than the center tap. The directionality of this diode 12 is in the forward direction of the diode 11. And a capacitor 1 is connected between both ends of the tertiary coil N3.
Connected by 3. Note that this capacitor 13 may not be necessary in some cases. And primary coil NI+tertiary coil N3 in the transformer input side winding. And the relationship between the number of turns of the secondary coil N2 of the output side winding is as follows.

N257. , N2. , -P. However, ■p in the formula: Cyrisk OFF
Reverse electromotive force E: Output voltage of rectifier 2 In this circuit configuration, the primary coil of the transformer,
The number of turns of the secondary coil and tertiary coil is adjusted so that the output voltage of the secondary coil remains constant.

The voltage induced in the secondary coil N2 by the transformer secondary coil N1 when the thyristor 5 is turned on and the O of the thyristor
During FF, a high voltage flows through the tertiary coil N3 as shown by the arrow in Figure 6, and the voltage induced in the secondary coil N2 becomes the same value, so a clean voltage without ripples is given to the load 1o after smoothing. be able to.

As described above, according to the present invention, the transformer input side winding is set to have an appropriate number of turns as a primary coil and a tertiary coil by means of an intermediate tap,
The same voltage is always induced in the secondary coil on the output side of the transformer, regardless of the input of normal voltage from the rectifier when the risk is ON or the input of reverse high voltage electromotive force when the risk is OFF. There is no need to increase the voltage resistance of the 7P, and there is no need to worry about negative effects such as noise interference on other equipment.

[Brief explanation of the drawing]

FIG. 1d is an electrical circuit diagram of a conventional AC-DC converter. FIG. 2 is an operating waveform diagram of the AC-DC converter. (1) is an operation waveform diagram of the voltage induced on the secondary coil side. (2) is an operating waveform diagram of the voltage applied to the load, and Figure 3 is 2
...Bridge type rectifier 4...Transformer 5...
High-speed switching element 6... Capacitor 11.12
...Diode 16...Capacitor N1.
...-Secondary coil N2...Secondary coil N3...Tertiary coil Applicant Hitachi Thermal Appliances Co., Ltd. Figure 2

Claims (1)

[Claims] By providing an intermediate tap, the primary coil with an appropriate number of turns (
The positive pole of the DC rectified with AO is connected to the intermediate tap of the transformer (4), which is composed of the input winding forming the N1), the tertiary coil (N3), and the output winding forming the secondary coil (N2). The anode of the high-speed switching element (5) is connected to one end of the secondary coil (N1) on the side other than the intermediate tap, and the cathode is grounded. A series circuit of a forward diode 01) and a capacitor (6) is connected such that the capacitor (6) is on the cathode side, and the connection point between these diodes I and the capacitor (6) is connected to the tertiary coil (
A, 0-DO converter, characterized in that one end of N3) on the side other than the intermediate tap is connected to the diode 01 through a forward diode Q2.