Overvoltage protection for input/output circuits
AssigneeKone Corporation
InventorSeppo Suur-Askola
Life of this patent
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Abstract
The invention relates to a method for protecting an I/O electronic circuit against overvoltages. The I/O circuit of the electronic circuit is provided with a current path (1) comprising a first diode (V1N), through which current path a current (ip) flows when the mains voltage is negative, and with a second current path (2) comprising a second diode (V1P) and a thyristor (T1), the thyristor (T1) being fired by a time-delay circuit charged by a positive voltage, and that the current flowing through the current paths (1,2) is used to trigger a protection device.
Claims11
A method for protecting an I/O circuit of an electronic circuit against overvoltages, comprising the steps of:
- (a) connecting the I/O circuit of the electronic circuit to a current path comprising a first diode through which current flows when the voltage on the I/O circuit is a negative overvoltage;
- (b) providing the I/O circuit of the electronic circuit with a second current path comprising a second diode connected in series to a time-delay circuit at a first node;
- the time delay circuit including a thyristor connected between the first node and ground and having a gate, a zener diode connected in series with a first resistance between the first node and ground, and a second resistance connected between the gate and a second node linking the zener diode and the first resistance, whereby the thyristor is fired by a time-delay in the time-delay circuit when the voltage on the I/O circuit is an a positive overvoltage, the current flowing through the current paths providing the overvoltage protection.
An apparatus for protecting an input/output circuit of an electronic circuit against overvoltages, comprising:
- a conductor for the input/output circuit of the electronic circuit;
- a first reverse-biased diode having an anode connected to ground and a cathode connected to said conductor;
- a second forward-biased diode connected between the conductor and a first node;
- and
- a time-delay circuit connected between the first node and ground, said time-delay circuit including a first capacitor and a thyristor connected in parallel between the first node and ground, a gate of said thyristor being connected through a Zener diode to the node and to a cathode of said second diode.
Dependencies are inferred from the claim text.