SU813392A1 - Protected line voltage stabilizer - Google Patents

Description

(54) LINEAR VOLTAGE STABILIZER WITH PROTECTION

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The invention relates to electrical engineering, in particular to the question of protecting linear stabilizers against overload.

A stabilizer with protection is known that reduces the collector currents of the regulating transistor as the stabilizer overload increases, which allows the power dissipation of the regulating transistor to be reduced in the overload mode compared to stabilizers containing previously common protection ensuring that the stabilizer current is limited at the maximum level. .

Closest to this technical solution is a linear voltage regulator with protection, containing a regulating transistor, a collector connected to the input terminal, a transistor of the feedback amplifier connected to the base of the regulating transistor by a collector, and the base of the adjustable voltage divider connected between output pins, and the emitter - through the reference element with a total thickness, the protection node, consisting of an executive transistor, the collector connected to the base of the regulating transistor a resistor, an emitter - with an output pin, and a base through a resistor. with the emitter of the regulating transistor, and a resistive current sensor included in the power circuit between the emitters of the regulating and actuating transistors 2.

The disadvantage of this stabilizer is a change in the trigger threshold when adjusting the output voltage, resulting in the trigger threshold setting

protection must be selected above the rated stabilizer current. In connection with this, when overloading the control transistors, more power is dissipated, which reduces the reliability of the stabilizer.

The purpose of the invention is to eliminate the change in the threshold of protection operation when adjusting the output voltage.

Claims (2)

The goal is achieved by introducing a current stabilizing transistor into the linear voltage regulator with protection, the collector of which is connected to the base of the actuating transistor, the base to the base of the amplifying transistor, and the emitter to the common resistor. The drawing shows an electrical circuit of a linear voltage regulator with overload protection. The circuit contains a regulating transistor 1 connected between the input and E output positive poles of the stabilizer, the base of which is connected to the output of amplifier 2 (in the given example contains transistor 3 and load resistor 4) and to the collector of protection transistor 5. Through the first resistor 6, the base-emitter junction of the protection transistor 5 is connected to the second resistor 7 connected to the stabilizer load circuit. The output voltage of the stabilizer is connected to a voltage divider consisting of a third resistor 8 and a fourth resistor 9, the midpoint of which is connected to one of the amplifier inputs, and the second input of the amplifier is connected to a voltage source 10, which contains a zener diode 11 and a ballast resistor 12. In addition, a transistor 13 and a fifth resistor 14 are included in the stabilizer, connected in accordance with the current regulator circuit. The device works as follows. If there is no overload, the protection device does not affect the operation of the stabilizer. Adjusting the output voltage is performed by using a resistor 8. When the stabilizer is overloaded, when the voltage drops across the second resistor 7, exceeding the reference voltage on the first resistor 6 and the cut-off voltage of the input characteristic of the protection transistor 5, opens the protection transistor 5. In this case, the control transistor 1 is no longer controlled by the amplifier 2, but by the protection transistor 5, which reduces the control current of the control transistor, leads to a decrease in the output voltage of the stabilizer. In this mode of operation of the stabilizer, decreasing the output voltage causes a proportional decrease in voltage on the fourth resistor 9, the output voltage regulator of the stabilizer, as a result of which the collector current of the auxiliary transistor 13 decreases and, accordingly, the reference voltage on the first resistor 6 5 zaphity. A decrease in the voltage drop across the first resistor b as the stabilizer overload increases ensures that the protection transistor 5 is held open by a smaller voltage drop on the second resistor 7, which reduces the load current and the power dissipated by the control transistor 1 in the emergency mode. If, for consistency, to consider an extreme overload mode — a short circuit, then in this mode the output voltage of the stabilizer is completely absent, and therefore the reference voltage on the first resistor 6 is zero. This ensures that the protection transistor 5 is held open by lower residual stabilizer currents, which creates a control voltage across the second resistor 7, which significantly reduces the power dissipated by the regulating transistor. Thus, the chain from the auxiliary transistor 13 and the fifth resistor 14 changes its conductivity characteristic when the stabilizer transitions from the operating mode to the overload mode. In the operating mode of the stabilizer, it behaves as a current stabilizer, and in the overload mode as a linear resistor, which ensures the achievement of the set goal. The proposed technical solution of a linear stabilizer, having an output voltage adjustment and containing overload protection, has a higher reliability, since eliminating the effect of output voltage adjustment on the setpoint of the protection response threshold allows choosing this setpoint closer to the nominal value of the stabilizer load current, therefore, less power is dissipated at the overload on the control transistor. Claims of the invention Linear voltage regulator with protection, containing a regulating transistor, a collector connected to the input terminal, a transistor of the feedback amplifier connected to the base of the regulating transistor by a collector, and the base with the midpoint of an adjustable voltage divider connected between the output terminals and the emitter through a common support element, a protection node consisting of an executive transistor, a collector connected to the base of the regulating transistor, an emitter — with an output terminal, and the base through a resistor with an emitter of the regulating transistor, and a resistive current sensor included in the power circuit between the emitters of the regulating and actuating transistors, characterized in that, in order to eliminate the change in the protection threshold when adjusting the output voltage, a current stabilizing the transistor whose collector is connected to the base of the executive transistor, the base to the base of the amplifying transistor, and the emitter via the inserted resistor to the common bus. Sources of information taken into account in the examination 1. Dulski R., Lipinski M., Igschen Viet Dung. Some issues of designing circuits for protecting low-voltage power sources against short-circuits. JINR communications. Dubna, 1977. 2. “Radio No. 9, 1971, p. 44. 07 -az-0 + entrance Output 15 -0П 40