CS230772B1 - Wiring to indicate a symmetric power supply failure - Google Patents

Abstract

The invention relates to a circuit for indicating the failure of a symmetrical voltage source, for example for monitor screens. The essence of the invention is the connection of a resistive divider with transistors that have protective diodes in their bases, while the emitter of the second transistor is connected to a zener diode at the output terminals. The connection is intended to protect the monitor against burning out of the phosphor by an electron beam in the event of a source failure.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The invention relates to a circuitry for indicating a failure of a symmetrical power supply, for example for monitor screens.

For any reason, video monitors may fail to supply the power supply, the positive or negative branch, thereby stopping the beam from drawing on the screen and glowing to one point. At the brightness required to observe the image, a non-shifting beam can destroy the incident spot on the phosphor, causing damage to the screen.

These disadvantages are eliminated by a circuit for indicating the failure of a symmetrical voltage source consisting of a resistive divider connected between active elements, the principle being that the resistor divider consisting of three resistors is connected between the input terminals of the voltage source, the first diode being connected between the first and second resistors. connected by an anode to the base of the first transistor whose collector is connected via the fifth resistor to the negative input terminal and the emitter to the first output terminal is connected via the fourth resistor to the positive input terminal, while the second diode connected by the cathode to the base a transistor whose collector is connected to a first output terminal and an emitter to a second output terminal is connected to an anode of a zener diode, the cathode of which is connected to the first output terminal.

2230 772

The main advantage of the circuitry according to the invention is the independence of the circuit from the external supply voltage, thereby preventing damage to the monitor screen in the event of a power failure and thus prolonging the life of the screen.

BRIEF DESCRIPTION OF THE DRAWINGS The invention is illustrated in more detail by the accompanying drawing, in which an example of connection is shown.

The basic circuit wiring consists of a resistive divider of three resistors

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1, 2 · J connected in series between the two input terminals 11, 12. to which the supply voltage of the power supply is connected. Between the first and second resistors 1 and 2, the cathode of the first diode 2 is connected, and between the second and third resistors 2 and 2 the anode of the second diode 6. The first transistor 2 is connected base to the anode of the first diode 2. and an emitter with a first output terminal 13. A positive input terminal 11 is coupled to the first output terminal 13 via a fourth resistor 6. The cathode of the second diode 6 is connected to the base of the second transistor 8, whose emitter is connected to the second output terminal 14 and the collector is connected to the first output terminal 13. The emitter of the second transistor 8 is together with the second output terminal 14 still connected to the anode of the zener diode 10 connected to the first output terminal 13 ·

The wiring works as follows:

In the state where the absolute value of the positive and negative voltages at the input terminals 11 is the same, there is a voltage value between the first and second resistors 1, 2 as at the first output terminal 13 where the voltage is given by the fourth resistor 6 and the voltage of the zener diode 10. This voltage value between the output terminals 12 and 14 corresponds to the voltage value of the logic one. If the voltage at the positive input terminal 11 is zero and the negative input terminal 12 is supply voltage, then the first transistor 2 closes and at the first output terminal 13 there is a voltage corresponding to logic zero. If it is on the positive input terminal 11

230 supply voltage and at the negative input terminal 12 the zero voltage will switch on the second transistor 8 and at the first output terminal 13 there will be a voltage corresponding to logic zero. If the voltage at both input terminals 11, 12 is zero, the voltage at the first output terminal 13 will be zero.

The main field of application of this connection is in protective circuits for limiting the current of screens in monitors.

Claims (1)

SUBJECT OF THE INVENTION 230 772 Wiring for indicating the failure of a symmetrical voltage source consisting of a resistive divider connected between the active elements / characterized in that a resistive divider consisting of three resistors (1, 2, 3) is connected between the input terminals (11, 12) of the voltage source, and a second resistor (1, 2) is connected by a first diode (5) connected to the base of the first transistor (7), the collector of which is connected via a fifth resistor (9) to the negative input terminal (12) and emitter to the first output terminal (13) ) connected via a fourth resistor (4) to a positive input terminal (11), while a second diode (6) connected by a cathode to the base of the second transistor (8), the collector of which is connected between the second and third resistor (2,3) of the divider connected to a first output terminal (13) and an emitter to a second output terminal (14) which is connected to the anode of a zener diode (10) whose cathode is connected to the first output terminal (13).