SU1320800A1 - Method of protecting regulated power supply source from overloads and short circuits - Google Patents

Abstract

The invention relates to electrical engineering and can be used in secondary power sources. The goal is to increase the reliability of protection by reducing the current of the key element and the diode of the LCD filter when overloaded or short-circuited. To do this, measure the output voltage, sum it with the reference voltage, and limit the duration of the control pulses to the key element directly proportional to the resulting summation signal, which leads to a decrease in the average current through the LCD. 1 il. i (L

Description

The invention relates to electrical engineering and can be used in the construction of sources of secondary power for autonomous television equipment, for example, portable transmission television cameras.

The purpose of the invention is to increase reliability by reducing the currents of the key element and / of the LCD filter during an overload or short circuit,

The drawing shows a stabilized power source.

The stabilized power supply contains a control unit 1 consisting of a key element 2 connected in series and an LCD-filter-diode 3, throttles 4 and a capacitor 5. The pulse selector 6 contains a coincidence circuit 7 and, for example, a time-controlled circuit 8. One input of the coincidence circuit 7 is connected to the diode 3 of the LCD filter, the second input is connected to the output of the control unit 9, and the third input is connected to the output of the driver circuit 8, the inputs of the driver circuit 8 are connected to the terminals of the choke 4. ale Entu 2. One input of the adder 10 is connected. with the output terminal of the power supply and the second input connected to the voltage code of the reference voltage. The output of the adder 10 is connected with the time setting circuit 8.

The stabilized power source operates as follows.

In the overload or short circuit mode, the output of control unit 9 is at a logic high. In this case, the open state duration of the key element 2 is determined by the duration of the limiting pulses of the driving circuit time 8j, and the duration of the closed state is determined by the time the current drops through the choke 4 to zero. The maximum current through the inductor D1

t max

in this case equals

- - O and L,

L.

(one)

where t

the duration of the pulse limiting time of the master circuit;

throttle voltage; L is the inductance of the choke. The limiting time of the toj-p is inversely proportional to the voltage UL, and

and,

may be proportional to the sum of the voltages

and

f)

+ and.

Where

 ogre

and

U2 out

+ and „„),

(2)

bull

- output voltage; Ug is the reference voltage;

K - coefficient of proportionality.

Substituting the expression (2) in- (1), get

E

s

+ and, „.), (3)

Those. the maximum value of the current through the inductor, and hence the current of the key element during an overload or short circuit, is limited and decreases with decreasing the output voltage to the minimum value determined by the value of the voltage

and.

 on

Average current through the diode

five

Where

-sr t

(.

2 t „-Tt.

(four)

Where

gokhar

and -gr, closed

- the time of the closed state of the power key, equal to

0 „. „+ And

(five)

YOU) 1

diode voltage

LCD35

filter.

Substituted expressions (2), (3), (5) into expression (4) and taking into account that

and, E - and

K |,

- and

out

five

0

0

get

1c where

, )

E-ut

-and

Eu,

+ U

SiiLi.

- voltage on key

element.

From this expression, it can be seen that as the output voltage decreases during an overload or short circuit, the average current through the diode of the LCD filter also decreases.

Claims (1)

Formula iso The method of protection against overloads and short circuits stabilized. power source auth. No. 1117616, characterized in that, in order to increase reliability by reducing the currents of the key element and the LCD diode during an overload or short circuit, the output voltage is measured, summed with the reference voltage, and pulses are generated Editor I. Casard Compiled by V. Baranov Tehred M. Morgental Proofreader L. Pilipenko Order 2658/51 Circulation 863 Subscription VNIIPI USSR State Committee for inventions and discoveries 113035, Moscow, Zh-35, Raushsk nab., 4/5 Production and printing company, Uzhgorod, Projecto st., 4 controls are a key element whose duration is directly proportional to the resulting voltage.