JPS5911290B2 - Pulse generation circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pulse generation circuit whose oscillation period can be varied.

Conventional variable oscillation period pulse generation circuits require two mutually insulated power supplies to separate the grounding system of the variable impedance element for control and the grounding system of the load serving as the output.

FIG. 1 shows a conventional pulse generation circuit diagram.

In this figure, a pulse generated by a known pulse oscillation circuit consisting of a variable impedance element 7, a capacitor 16, a single junction transistor 15, and resistors 14 and 17 is transmitted through an amplification circuit consisting of a capacitor 18, resistors 19 and 21, and a transistor 20. The voltage is applied to the control winding 4 of the transformer 1 via the control winding 4 of the transformer 1.

FIG. 2 shows the waveform of this applied pulse, the period of which is controlled by the impedance element 7.

This is set to a predetermined pulse width, and a known current feedback type drive circuit consisting of a transistor 5, a drive winding 2, a feedback winding 3, and a resistor 13 is configured for the purpose of power amplification, and pulse power is supplied to a load 6. .

At this time, it is well known that the pulse width is set by the pace-emitter voltage of the maximum magnetic flux density transistor 5 in the core of the transformer 1 and the constants of the drive winding 2.

The waveform is as shown in FIG.

This circuit can vary the oscillation period by controlling the variable impedance element 7, but when it is desired to separate the grounding system of the variable impedance element 7 and the grounding system of the load 6, two power supplies are required. It has the following disadvantages.

The present invention eliminates the need for a special power source by improving the drive circuit consisting of a transformer 1, a transistor 5, etc.
To provide a pulse generating circuit which can vary the oscillation frequency by controlling a variable impedance element 7 only by using a single power supply, and can separate the grounding system of the variable impedance element 7 and the grounding system of a load 6.

In order to achieve the above purpose, by applying a bias to the transistor 5 and configuring a self-excited oscillation circuit with the transformer 1, etc., the oscillation period is determined by the excitation reset time of the transformer 1, and the The reset time is
Focusing on the fact that it can be controlled by the termination condition of the reset voltage generated as a reverse voltage in each winding of the transformer 1 during the cut-off period of the transistor 5, it is possible to terminate only the reset voltage generated in the control winding 4 with the variable impedance element 7. This configuration is connected via a diode.

The present invention will be explained in detail below using the embodiment shown in FIG.

The drive winding 2 of the transformer 1 is connected between the base and emitter of the transistor 5 via a resistor 12, and a bias resistor 11 and a bias diode 10 are connected to the center tap of the drive winding 2.
is connected, activating the transistor 5, and connecting the load current to the feedback winding 3 in the positive feedback direction.

At the same time, a circuit in which a diode 9 and a variable impedance element 7 are connected in series is connected to both ends of the control winding 4 in the direction in which current flows through the variable impedance element 7 when the transistor 5 is cut off.

In this circuit, the conduction time of the transistor 5 is determined by the drive winding 2, the maximum magnetic flux density of the core of the transformer 1, and the constants of VBE of the transistor 5+voltage drop of the resistor 12.

Further, during this conduction period, the transformer 1 is excited by the load current flowing into the feedback winding 3 and reaches saturation.

After saturation, transistor 5 is cut off as soon as its drive is cut off, and each winding of transformer 1 induces a reverse voltage.

This voltage causes the bias resistor 11 to cause the transistor 5 to
The bias towards is also blocked.

The voltage induced in the period control winding 4 is terminated at the variable impedance element 7 via the diode 9.

The product of this reverse voltage and its induced time is constant with respect to the excitation energy of the transformer 1, so if the variable impedance element 7 is controlled low, the voltage at both ends is low, so it takes time for the excitation energy to re-center, and the element If the voltage is controlled to be high, the excitation energy can be reset in a short time because the voltage across both ends is high.

When the excitation energy is reset, the reversely applied voltage disappears and the bias current flowing through the bias resistor 11 activates the transistor 5, making it conductive and proceeding to the next new cycle.

FIG. 5 shows the pulses supplied to the load at this time.

As described above, by controlling the variable impedance element 7, the cut-off period of the transistor 5 can be controlled and the oscillation period can be controlled. Therefore, by only supplying a single power source, the grounding system of the variable impedance element 7 and the grounding system of the load 6 can be controlled. separation can be achieved.

Further, another example that takes advantage of the spirit of the present invention is shown in FIG.

This figure is the same as FIG. 4 except that the variable impedance element 7 is replaced with a transistor.

By applying a control signal to the terminals 22 and 22' in FIG. 6, the average conduction impedance of the transistor 7 can be controlled, and thereby the oscillation frequency can be controlled. Separation from the ground system can be achieved.

As described above, the present invention can control the pulse width of the pulse generation circuit and achieve separation of the grounding system of the suppressor circuit and the grounding system of the load even in the case of a single power supply, so it is economically effective. big.

[Brief explanation of the drawing]

FIG. 1 is a conventional pulse generation circuit, FIGS. 2 and 3 are waveform diagrams of the circuit in FIG. 1, FIG. 4 is a circuit diagram of an embodiment of the pulse generation circuit according to the present invention, and FIG. The waveform diagram in FIG. 6 is a circuit diagram of another embodiment of the pulse generating circuit according to the present invention. DESCRIPTION OF SYMBOLS 1...Transformer, 2...Drive winding, 3...Return winding, 4...Control winding, 5...Transistor, 6...
・Load, 7...i=1 variable impedance element, 10・
...Diode, 11...Bias resistor, 12...
Resistor, 13...Resistor, 14...Resistor, 15...Single junction transistor, 16...Capacitor? ,17...
Resistor L 1 8... Capacitor, 19... Resistor, 20
...Transistor, 21...Resistor.

Claims (1)

[Claims] 1. In a pulse generation circuit having a current feedback self-excited oscillation circuit in which a transistor, a load, and a power source are connected in series to the feedback winding of an oscillation transformer, a series connection circuit with a diode and a variable impedance element is connected to both ends of the control winding of the oscillation transformer. are connected in a direction in which current flows such that when the transistor of the oscillation circuit is in a cut-off state, the energy stored in the oscillation transformer is absorbed by the variable impedance element.