JPS642028B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to, for example, an AC-DC converter device equipped with a semiconductor switching element for circuit interruption.
Its purpose is to prevent overcurrent to the load, and in a converter device equipped with a semiconductor switching element for circuit interruption, a current transformer is connected in series with the switching element, and the secondary coil of the current transformer is connected in series with the switching element. The AC input terminal of the full-wave rectifier circuit and a parallel circuit of a resistor are connected to the AC input terminal of the full-wave rectifier circuit, and one terminal of the DC output terminal of the full-wave rectifier circuit is connected to the midpoint of the resistor, and the DC output terminal is connected to the output voltage. The switching element is characterized in that it is connected to the control pole of the switching element via an oscillation circuit that oscillates a signal with a pulse width corresponding to the switching element.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a partially blocked circuit diagram of an embodiment of the present invention.

In the figure, 1 is a rectifier circuit connected to an AC power supply 2. This circuit 1 is connected to the primary coil of a transformer 4 via a semiconductor switching element 3 for circuit interruption, and the secondary coil is connected to a rectifier 5 via a rectifier 5. is connected to the output terminal 6, thus rectifying the alternating current, and then converting this direct current to the switching element 3, e.g.
By switching on and off the circuit at a high frequency of 100KHz to 200KHz, the voltage is converted to AC again through the transformer 4, and further rectified by the rectifier 5 to obtain the desired DC output voltage.

The present invention provides such a converter circuit,
A current transformer 7 is connected in series with the switching element 3, its secondary coil is connected to the detection circuit ₈ via the terminal _A1A1 , and its output terminal is connected to a current transformer 7 with a pulse width corresponding to the future output voltage. Connect to a known oscillation circuit 9 that oscillates a signal, and connect the output of the oscillation circuit 9 to a terminal.
B ₁ B ₁ is applied to the control poles of the two switching elements 3 with opposite polarities, and the detection circuit 8 is connected to the secondary coil of the current transformer 7 as shown in the second diagram. The resistors 10A, 10B and the AC input terminals 12A, 12B of the full-wave rectifier circuit 11 are connected in parallel, and the DC output terminal 14 of the full-wave rectifier circuit 11 is connected to the detection signal output terminals 13A, 13B.
One of the resistors A and 14B, 14B, is connected to the midpoint between the resistors 10A and 10B.

In FIG. 1, reference numeral 15 denotes a soft start circuit 17, 17 that gradually increases the rectified voltage of the full-wave rectifier circuit 1 by applying a gradually increasing voltage to the control pole of the thyristor 16 that intervenes in the full-wave rectifier circuit 1. is a tertiary coil of the transformer 4, which is used to return the energy stored in the transformer 4 during the cut-off period of the switching elements 3, 3 to the power supply side via a rectifier. In FIG. 2, 18 is a filter circuit.

Next, the operation of this embodiment will be explained.

Now, in FIG. 1, the current flowing in the connection circuit 19 between the full-wave rectifier circuit 1 and the primary coil of the transformer 4 is caused by the intermittent opening and closing of the switching element 3 and the tertiary coil 17 of the transformer 4 when the switching element 3 is switched on and off. To return energy to the power source, a current flows as shown in FIG. 3A. In the secondary coil of the current transformer 7, a secondary current corresponding to the primary current flows through the resistors 10A and 10B according to the ampere-turn law.
A voltage drop occurs at the 0B terminal. FIG. 3B shows that due to this voltage drop, a current flows through the DC output circuit of the full-wave rectifier circuit 11, and this current causes the detection signal output terminal 1 to flow.
This is the waveform of the detection signal voltage Ecc occurring between 3A and 13B. This detection signal voltage Ecc is
Depending on the resistance values of A and 10B, the primary current of the current transformer 7, that is, the load current I _CT changes as follows.

When the resistance value of the resistor 10B is increased while the resistance value of the resistor 10A is kept constant, the voltage waveform between the terminals 13A and 13B changes from a broken line to a solid line, as shown in FIG. 3C. do. In this way, the resistor 10B affects the detection signal waveform, and when this resistance value is increased to 9Ω, 12Ω, and 20Ω, for example (in this case, the resistor 10A is 100Ω), the relationship between the detection signal voltage Ecc and the load current _ICT is , 4th
The detection signal voltage Ecc changes as shown in Figures A, B, and C, and all of the detection signal voltages Ecc decrease from a predetermined load current value.

Thus, by inputting this detection signal voltage Ecc _{to the} oscillation circuit ₉ as shown in FIG _.
An oscillating voltage having a pulse width corresponding to the oscillating voltage is outputted, and this oscillating voltage is inputted to the control pole of the semiconductor switching element 3 for circuit disconnection with mutually opposite polarity. When the current I _CT flowing through the connection circuit 19 rises above a predetermined value, the fourth
As shown in the figure, the detection signal voltage Ecc begins to decrease, so the pulse width of the oscillation voltage output from the oscillation circuit 9 becomes narrower, and the increase in the current I _CT is controlled. Therefore, no excessive current flows through the load circuit connected to the output terminal 6 of the transformer 4, and the load and the transformer 4 are protected.

As described above, according to the present invention, the converter device has the effect of suppressing excessive current to the load with a simple configuration.

[Brief explanation of drawings]

FIG. 1 is a partial block circuit diagram of an embodiment of the present invention, FIG. 2 is a circuit diagram of the detection circuit 8, FIG. 3 is a waveform diagram of each part, and FIG. B
and C is the current transformer 1 according to the values of resistors 10A and 10B.
A characteristic diagram of secondary current versus detection signal voltage is shown. 3...Switching element for circuit interruption, 4...Transformer, 7...Current transformer, 8...Detection circuit, 9...Oscillation circuit, 10A, 10B...Resistor, 11...Full-wave rectifier circuit.

Claims (1)

[Claims] 1. In a converter device equipped with a semiconductor switching element for circuit interruption, a current transformer is connected in series with the switching element, and the AC input terminal of a full-wave rectifier circuit and a parallel circuit of a resistor are connected to the secondary coil of the current transformer. At the same time, one terminal of the DC output terminal of the full-wave rectifier circuit is connected to the midpoint of the resistor, and the DC output terminal is connected to the DC output terminal through an oscillation circuit that oscillates a signal with a pulse width corresponding to the output voltage. A converter device characterized in that it is connected to a control pole of a switching element.