SU1691945A1 - A pulse generator being protected from current overloading - Google Patents

Abstract

The invention relates to a pulse technique and can be used in secondary power sources. The purpose of the invention — improving reliability — is achieved by limiting the current load at a given level. A pulse shaper with overcurrent protection contains a power supply 1, a half-bridge pulse amplifier 2, a power transformer 3 with a primary winding 4 and a secondary winding 5, a capacitor 6, a control input 7, output terminals 8, 9 for connecting the load, a current transformer 10 with the primary winding 11 and the secondary winding 12, resistors 13, 14, 15, transistors 16, 17, diode 18, resistors 19, 20, load 21. With external influences in the form of a current overload on the output terminals, the driver is self-protected and does not fail . 2 Il.

Description

The invention relates to a pulse technique and can be used in secondary power sources.

The purpose of the invention is to increase reliability by limiting the load current at a given level.

FIG. 1 shows a simplified electrical circuit of the driver; in fig. 2 - diagrams of his work.

Pulse shaper with overcurrent protection contains source 1. power supply, half-bridge switching amplifier 2, power transformer 3 with primary winding 4 and secondary winding 5, capacitor 6. control input 7, output terminals 8 and 9 for connecting the load, current transformer 10 with primary winding 11 and secondary winding 12, resistors 13 , 14, 15, np-p and pnp transistors 16, 17, respectively, diode liL resistors 19, 20, load 21.

Transistors 16, 17 with resistors 14, 15 form a threshold device that triggers when the winding 12, bounded by resistor 20, reaches a voltage amplitude of a predetermined value, which is determined by the magnitude of the instantaneous current in the primary winding 11 of the current transformer 10. When triggered, the threshold device is blocked for the duration of the control pulse input from terminal 7.

 The value of the resistor 20 determines the threshold of the protection circuit. The current transformer 10 can be made on a core with a rectangular hysteresis loop, since it operates in a symmetrical mode without bias current.

The pulse shaper with overcurrent protection works as follows.

In the initial state, when the power source 1 is turned on, the key 22 is a pulse one.

with

o you

Yu

Ј

cl

The switch 2 is set to the open state, the key 23 to the closed state. Capacitor 6 is discharged, the voltage on it is zero. The load current 21 is also zero. Transistors 16 and 17 of the coating protection circuit. The control pulses 24, coming from the external pulse generator to the control terminal 7, open the key 23, which closes the key 22. A current AND consumed from the power source 1 starts to flow through the negative terminal of the power source 1 - the closed key 23 - primary winding 4 of the transformer 3 - current winding 22 of the current transformer 10 - capacitor 6 - positive terminal of power supply 1.

The initial current value is determined by the load resistance 21 - the lower the resistance, the greater the initial current value. During the control pulse current, the current And linearly increases, the growth rate is determined by the inductance of treatment 4 and the voltage applied to the winding 4 of the transformer 3. Under the influence of the current And, the capacitor 6 starts to charge, and the reactive energy accumulates in the core of the transformer 3 .

At the moment of end of the pulse 24 (see FIG. 2) of the control switch 23, the switch 22 closes the current H and the current r flows through the circuit capacitor 6 (power source) - winding 11 of current transformer 10 - primary winding 4 of transformer 3 - closed key 22. The energy stored in the capacitor 6 and the transformer 3 begins to discharge to the load 21.

With the arrival of the next control pulse 24, the process is repeated.

In the steady state mode, the average value of the voltage 25 on the capacitor 6 is directly proportional to the ratio of the duration of the tu pulses to the period T following them. The voltage at load 21 is a variable rectangular shape, symmetrical at a ratio of, 5, and asymmetric at other values of tu / T.

The currents H and 12 flowing through the winding 11 of the current transformer 10 lead in the secondary winding 12 and across the resistor 20 voltage pulses 26, the amplitude of which is proportional to the currents And and 2 and is controlled by changing the resistance of the resistor 20. The pulses 26 through the resistor 19 are applied to the junction transistor emitter base 16.

With a load resistance of 21 not exceeding the nominal value, the amplitude of the pulses 26 is not sufficient for the coupling of the transistor 16, therefore, again, the active elements have no effect on the operation of the pulse shaper. The control pulses 27 at the control input of the pulse amplifier 2 repeat the shape of the pulses 24 from the removal of some voltage drop across the resistor 13, which is caused by the input current of the amplifier 2. At the collector of the transistor 16, the pulses 28 also repeat the shape of the pulses 24 of the control.

When the load resistance 21 decreases, the current consumption of the device increases, the amplitude of the current i also increases. At a certain value of the load resistance 21, the amplitude of the current And reaches such a value that the voltage induced in the winding 12 of the transformer

0 Yu current causes the transistor 16 to turn on, the voltage 28 on its collector abruptly decreases, which causes the transistor 17 to turn on, and the protection circuit is blocked for the duration of the pulse 24

5 controls The low voltage through the diode 18 bypasses the control input of the amplifier 2, which causes the closure of the key 23 and the opening of the key 22. Almost all of the amplitude of the pulse 24 falls on

0 to the resistor 13. Upon termination of the pulse 24, the protection circuit is unblocked, transistors 16 and 17 are turned off, as their base currents are reduced to zero, and the next period / - 3 is repeated. amount

5, the energy accumulated in the capacitor 6 and partly in the transformer 3 decreases in this case, since the open state of the key 23 decreases (the connection time of the reactive elements 4 and 6 to the source 1 of the power supply). Thus, the current consumption is limited, i.e. overcurrent protection.

With a short circuit load 21 current amplitude And at the time of opening the key

5 23 increases dramatically, which leads to almost instantaneous operation of transistor 16, then transistor 17, and switching off key 23 through diode 18. The open state duration of key 23 decreases sharply, therefore, the amount of energy stored in capacitor 6 from power supply 1 also decreases. that protects the driver 2 current pulses, preventing it from breaking down.

5 Thus, the proposed pulse shaper with overcurrent protection has the property of self-limiting consumption current, which ensures safe operation of its key elements. At the same time, a proportional limitation of the current consumption is provided, the protection circuit is automatically disconnected after the overload is removed and in the absence of an overload it does not consume additional current.

Claims (1)

Invention Formula A pulse shaper with overcurrent protection, containing a half-bridge switching amplifier, the output of which is connected to the first output of the transformer primary winding, and the power inputs to the positive and negative terminals of the power supply, a capacitor, the first output of which is connected to the positive terminal of the power supply, the secondary winding a transformer, the terminals of which are connected to the output terminals of the driver, characterized in that, in order to increase reliability due to current limiting at the rear level, a current transformer, a pnp transistor, a pnnp transistor, a diode and five resistors are introduced into it, the second terminal of the transformer primary winding is connected to the second capacitor terminal through the primary winding of the current transformer, the control input terminal is connected to the first terminal of the first resistor, through the second resistor to the emitter, and through the third resistor to the pnp transistor base, diode cathode and npn collector transistor, the base of which is connected to the collector of a pnp transistor, and through the fourth resistor and connected in parallel the secondary winding of the transformer and the fifth resistor - to the emitter of the npn transistor and the den power supply terminal, second terminal the first resistor is connected to the diode anode and control input of the half-bridge pulse amplifier. FIG. 2