US 5,295,185 AGranted

Ringing signal generation circuit with protection against overvoltage

AssigneeFujitsu Limited

InventorToshihumi Washio

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Abstract

A ringing signal generation circuit contains a direct current power source, a transformer, a control transistor, a rectifying and smoothing circuit, an invertor circuit, and an invertor controlling circuit. The direct current power source generates a direct current voltage. The transformer contains a primary winding and a base-driving winding in a primary side, and a secondary winding in a secondary side. The control transistor is connected in series to the primary winding and the direct current power source, and controls a current flowing in the primary winding. The rectifying and smoothing circuit rectifies and smooths a current generated in the secondary winding. The invertor circuit for converting a direct current output of the rectifying and smoothing circuit into an alternating current. The invertor controlling circuit controls the invertor circuit. Further, an overvoltage detecting circuit is provided for detecting an overvoltage in the secondary winding; and a current supply stopping circuit is provided for stopping a supply of the current to the primary winding.

Claims10

Dependent claims

A ringing signal generation circuit, comprising:

a direct current power source for generating a direct current voltage;
a transformer, comprising a primary winding and a base-driving winding in a primary side, a secondary winding in a secondary side, and an additional winding;
a control transistor, connected in series to said primary winding and said direct current power source, for controlling a current flowing in said primary winding;
rectifying and smoothing means for rectifying and smoothing a current generated in said secondary winding;
an additional rectifying and smoothing means for rectifying and smoothing a current generated in said additional winding;
inverter means for converting a direct current output of said rectifying and smoothing means into an alternating current;
inverter controlling means for controlling said inverter means;
overvoltage detecting means for detecting an overvoltage in said secondary winding, said overvoltage detecting means including means for detecting an overvoltage in the output of said additional winding to indirectly detect said overvoltage in said secondary winding;
and
current supply stopping means for stopping a supply of the current to said primary winding in response to the detecting of the overvoltage by said overvoltage detecting means.

7 more elements

Dependencies are inferred from the claim text.

Facts

Application: 07/533,854Filed 6 Jun 1990
Priority: JP 1-1459638 Jun 1989
Granted: 15 Mar 1994
Term ends: Not estimatedThe source records don’t support an estimate.

Classification7 codes

H02M 1/32
Details of apparatus for conversion: means for protecting converters other than automatic disconnection
H02H 7/122
For static converters or rectifiers: for inverters, i.e. DC/AC converters
H02M 7/48
By static converters: using discharge tubes with control electrode or semiconductor devices with control electrode
H04M 19/02
Current supply arrangements for telephone systems: providing ringing current or supervisory tones, e.g. dialling tone or busy tone