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Diode Noise Suppression

IP.com Disclosure Number: IPCOM000079345D
Original Publication Date: 1973-Jun-01
Included in the Prior Art Database: 2005-Feb-26
Document File: 2 page(s) / 26K

Publishing Venue

IBM

Related People

Bunch, AD: AUTHOR [+4]

Abstract

In the circuit of Fig. 1, the square-wave current generator 2 represents the current switching action that takes place in some transistor voltage regulators, a diode 3 is a component of the voltage regulator circuit, and impedances 4 and 5 represent the resistance and inductance of the regulator. In such a circuit, diode 3 produces undesirable radiation when it turns off. Fig. 2 shows the normal turn off operation of diode 3. Between times t0 and t1, the forward current in the diode decreases toward zero and between time t1 and t2 the current reverses. Between time t2 and t3, the reverse current in the diode decreases very rapidly and thereafter has a damped oscillation to time t4. The current changes which occur between times t2 and t4 produce undesirable radiation.

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Diode Noise Suppression

In the circuit of Fig. 1, the square-wave current generator 2 represents the current switching action that takes place in some transistor voltage regulators, a diode 3 is a component of the voltage regulator circuit, and impedances 4 and 5 represent the resistance and inductance of the regulator. In such a circuit, diode 3 produces undesirable radiation when it turns off. Fig. 2 shows the normal turn off operation of diode 3. Between times t0 and t1, the forward current in the diode decreases toward zero and between time t1 and t2 the current reverses. Between time t2 and t3, the reverse current in the diode decreases very rapidly and thereafter has a damped oscillation to time t4. The current changes which occur between times t2 and t4 produce undesirable radiation.

As Fig. 3 shows, diode 3 is arranged to form a single-turn winding of a ferrite core 9. The diode may be mounted in a preformed core or the core can be formed as an integral part of the diode. The core can be mounted on the diode lead, if the metal can adversely shields the core from the magnetic flux of the diode current. Core 9 produces an inductance 10 and resistance 11 the circuit with diode 3, as Fig. 1 shows. Core 9 is arranged to provide a high value of resistance to the frequency during the interval to t2 to t4. Thus, the core suppresses the undesirable radiation caused by the diode switching operation, but it does not otherwise significantly effect the circuit operati...