Device for protecting a vertical deflection integrated circuit for a monitor

A device for protecting a vertical deflection circuit for a monitor having a display data channel (DDC) circuit, the device comprising:

• a computer input/output (I/O) circuit providing a vertical sync signal to said DDC circuit and said vertical deflection circuit when power is supplied, and receiving monitor information data from said DDC circuit when a predetermined time elapses thereafter;
• said DDC circuit receiving said vertical sync signal provided from said computer I/O circuit, and providing said monitor information data to said computer I/O circuit at said predetermined time thereafter;
• and
• a vertical frequency selection control circuit providing said vertical sync signal to said vertical deflection circuit if said vertical sync signal is received from said computer I/O circuit, and intercepting prior to reaching said vertical deflection circuit an abnormal vertical sync signal having a frequency higher than that of said vertical sync signal if said abnormal vertical sync signal is received from said computer I/O circuit, said vertical frequency selection control circuit comprising:
• a first monostable multivibrator receiving as a trigger input thereto said vertical sync signal, and providing a first pulse signal having a first pulse width determined by a first time constant;
• and
• a second monostable multivibrator receiving as a trigger input thereto directly without gating said first pulse signal provided from said first monostable multivibrator, and providing a second pulse signal having a second pulse width determined by a second time constant as an input to said vertical deflection circuit.

A circuit for providing on screen display information to a monitor while providing protection to a vertical deflection means within said monitor, the circuit comprising:

• display data channel (DDC) means for providing stored monitor information data;
• computer input/output (I/O) means providing a vertical sync signal to said DDC means and said vertical deflection means when power is supplied, and receiving monitor information data from said DDC means when a predetermined time elapses thereafter;
• said DDC means receiving said vertical sync signal provided from said computer I/O means, and providing said monitor information data to said computer I/O means at said predetermined time thereafter;
• and
• vertical frequency selection control means providing to said vertical deflection means:
• (a) if said vertical sync signal is received from said computer I/O means, said vertical sync signal;
• and
• (b) if an abnormal vertical sync signal is received from said computer I/O means, a single pulse having a pulse width equal to that of said vertical sync signal;
• whereby said vertical deflection means is protected;
• said vertical frequency selection control means comprising:
• a first monostable multivibrator receiving as a trigger input thereto said vertical sync signal, and providing a first pulse signal having a first pulse width determined by a first time constant;
• a second multivibrator receiving said first pulse signal directly without gating from said first monostable multivibrator, and providing a second pulse signal having a second pulse width determined by a second time constant;
• and
• switching means controlled according to said second pulse signal from said second monostable multivibrator, and providing said second pulse signal to said vertical deflection means.