SU983687A1 - Switch-type direct current regulator - Google Patents

Description

The invention relates to electrical engineering, in particular to voltage converters with a key DC regulator and a node for dynamic current limiting through it.

Known key DC regulators with an overload protection node, containing a switching transistor and a DLC filter, in the current circuit of which an overload signal sensor is connected to which the amplifier input is connected, the output of which is connected to a control key having a latch.

When overloaded, the control key locks the control signal of the switching transistor. In the known regulators, a capacitor is included in the amplifier circuit that integrates the signal to the input of the control key. The capacitor eliminates the irreversible shutdown of the current regulator during a brief overload, for example, during the startup mode.

The disadvantage of these devices is the inertia of the protection device, which does not ensure the elimination of short-term emergency overloads of the switching transistor.

The closest in technical essence and the achieved result to the proposed is a key current regulator containing a switching transistor, a DLC filter and a dynamic current limiting node, which includes a control transistor and a current sensor connected to the emitter circuit of the switching transistor, to which the control transistor input is connected, the collector of which is connected to the base of the SzSZ switching transistor. The considered node of the dynamic current limit of the key regulator provides The reduction of the through current through the switching transistor and the diode of the DLC filter, in the case of unlocking the switching transistor, reduces the dynamic power loss on it. In this case, a simple limitation of the current amplitude gives a positive result, since the recovery time of the inverse resistance of the diode of the DLC filter, which determines the time of the through current flow, is very short.

The current limiting node in question does not provide overload protection for the switching transistor.

if the overload current itself is not limited to a short time interval, which is a disadvantage of this device. The switching transistor enters such an overload mode in case of a pause skip that corresponds to the locked state of the switching transistor for the time during which demagnetization of the DLC filter Dros filter magnetic circuit occurs. The reason for missing a pause may be the effects of interference or non-stationary phenomena during a transient process when the current regulator is turned on or off. The overload of the switching transistor may also occur during the starting period when the voltage on the capacitor of the DLC filter is still small and cannot provide during the pause time the demagnetization of the throttle magnetic circuit. In both cases, this leads to a biased magnetization of the throttle magnetic circuit of the DLC filter, down to us. Since the collector current of the switching transistor cannot increase more than the value determined by the current limiting node, the excess Magnetization of the magnetic cores of the throttle will remove the coil-tight transistor from the saturation mode during the operating cycle.

The purpose of the invention is to increase the reliability of the key DC regulator by increasing the efficiency of the dynamic current limiting node, by introducing a guaranteed pause using the overload signal and reducing the dynamic power loss on it.

The goal is achieved by the fact that a key DC regulator containing a switching transistor connected in series to the power bus, a DLC filter and a dynamic current limiting node having a control transistor and a current sensor, the current sensor is connected to the emitter circuit of the switching transistor , the emitter of the control transistor is connected to the common point of the current sensor and the throttles of the DLC filter, the base is connected to the second output of the current sensor, and the collector is connected to the control circuit of the switching transistor, at node o A current resistor is inserted between the base of the control transistor and the second output of the current sensor and an RC circuit, connected between the base of the control transistor and the collector of the switching transistor.

The RC circuit includes a capacitor, a second and a third resistors, and a common point of the resistors is connected through an input diode with the emitter of the switching transistor.

The drawing shows the electrical circuit of the device.

The key DC regulator contains a switching transistor 1, the output of which includes a DLC filter 2 as part of the first diode 3, droplets 4 and the first capacitor 5. The control transistor b, the current sensor 7 included in the emitter circuit of the switching transistor 1, the first resistor 8, through which the control transistor b is connected with the current sensor 7, and the RC circuit 9, through which positive feedback takes place. RC circuit 9 contains the second capacitor 10 and the second and third resistors 11 and 12, the common point of the second and third resistors 11 and 12 are connected via the second diode 13 with the aim of the emitter of the switching transistor 1, the Third diode 14 included in the. The emitter circuit of the switching transistor is not a required element and must be introduced in the case when the saturation voltage of the collector-emitter of the control transistor b is higher or equal to the base-emitter voltage of the commutator of the transistor 1, If the control of the switching transistor 1 is performed through an isolating transformer with a filling factor of more than 50%, then during a pause on the secondary winding an increased blocking voltage acts and then the control collector transistor 6 is connected via a diode to the booster secondary winding connected to the base of the switching transistor 1.

The current limiting device of the switching transistor operates in the following manner.

With an increase in the current flowing through the switching transistor 1 in saturation mode, the voltage drop across the resistor of the current sensor 7 exceeds the limiting voltage at which the control transistor 6 opens, resulting in a decrease in the control current of the switching transistor 1, due to which will exit saturation mode. Due to the positive feedback through RC 9, the control transistor b is opened even more, and the switching transistor 1 switches to the current cut-off mode. The time of the locked state of the switching transistor 1, over which demagnetization of the magnetic core of the throttle 4 occurs, is determined by the time constant of the RC circuit 9. When the current flowing through RC-itenb 9 is not enough to hold the control transistor 6 in the saturation mode, it will start is locked, and if a release signal acts on the input of the switching transistor 1, it will open again. At the same time, at the first moment of its unlocking, a through current, flowing through it, and the first diode 3 of the DLC filter 2 will arise. This creating a voltage drop on the current sensor 7, opens the control transistor 6 by this voltage, thus reducing the value of the control current entering the base of the switching 1 6 transistor 1, which leads to the limitation of the amplitude of the through current. The through-current pulse is limited in the duration of the recovery time of the reverse resistance of the first diode 3, after which the switching transistor 1 re-enters the saturation mode. In this case, the RC circuit 9 is discharged, which is completed in a shorter period of time than the charge, since it passes through a circuit consisting of a second resistor 11 and a second diode 13, which has a lower resistance. This will speed up the preparation of a dynamic current limiting node for possible overload in the considered operating cycle of the key controller.

In addition to performing the function of protecting the switching transistor against overcurrent, the current limiting node reduces the dynamic power loss on it and accelerates its locking process. So, when a blocking voltage is applied to the input of the switching transistor, an increase in the voltage on its collector causes current to flow through the JC circuit 9, which unlocks the control transistor which, bypassing the base-emitter / switching transistor 1, accelerates the resorption of minority carriers in the base switching transistor.

Thus, the proposed technical solution improves the reliability of the current regulator and reduces the dynamic power loss at the station.

Claims (3)

1. A key DC regulator containing a switching transistor connected in series to the power bus, a DLC filter and a dynamic current limiting unit having a control transistor and a current sensor, the current sensor being connected to the switch emitter circuit The transistor, the emitter of the control transistor is connected to the common point of the current sensor and the throttles of the DLC filter, the base is connected with. the second output of the current sensor, and the collector is connected to the circuit switching transistor control, characterized in that, in order to increase the controller's reliability by increasing the efficiency of the dynamic limiting node current due to input on the overload signal of a guaranteed pause and reduction of dynamic losses on it, the first resistor inserted between the base of the control transistor and the second output of the current sensor and the JC circuit connected between the base of the control transistor and the switching collector transistor.  2. The regulator of claim 1, which is based on the fact that the RC circuit contains a capacitor, is: the second and three resistors, and the common point of the resistors is connected through the input diode to the switching emitter transistor. Sources of information taken into account in the examination 1. Patent CIUA No. 4127885, cl. 361-18, 1978. 2, Electronics, 1975, No. 20,; 47, rice, 5. 3. Patent CIUA 4028612, l, 323-17, 1977.