Direct current power converter with start-up and protection circuits
AssigneeTeletype Corporation
InventorDennis L. Stephens
Life of this patent
Estimating the term…
Abstract
A D.C. to D.C. converter including a start circuit having a choke with a primary winding and a start winding. A portion of the input power is fed through a section of the start winding to the base of a switching transistor connected in series with the primary winding. The transistor is operated as a blocking oscillator by the start circuit and a voltage is induced across a secondary winding of the choke. The secondary voltage is rectified and fed to the control input of a pulse width modulator. In response to a predetermined level of the secondary voltage, the output of the pulse width modulator is coupled to the base of the transistor and the start circuit disabled. Current overload and transient voltage protection circuits are also included.
Claims11
An apparatus for converting a direct current input voltage level to a preselected direct current output level including a start circuit for initiating operation of the apparatus upon the application of the direct current input comprising:
- a choke having a primary inductance, a start inductance and at least one secondary inductance, said primary, start and secondary inductances being magnetically coupled,
- a first switching means having a control terminal for intermittently switching the direct current input through said primary inductance,
- said start circuit including means for passing at least a portion of said direct current input to the control terminal of said first switching means, and means for passing at least a portion of the voltage across said start inductance to said control terminal of said switching means so that the rate of voltage change across said primary inductance created by the switching of current therethrough by said first switching means is reflected across said start inductance and to the control terminal of said switching means thereby causing said switching means to intermittently interrupt the input current through said primary inductance;
- means for rectifying the varying voltage induced across said secondary inductance by the current passing through said primary inductance to provide said selected direct current output level;
- a pulse generator responsive to the voltage across said secondary inductance and serving to provide a pulsed signal to the control terminal of said switching means in response to a predetermined level of said rectified secondary voltage;
- and
- means for disabling said start circuit in response to the output of said pulse generator so that said start circuit controls said switching means upon the initial application of said direct current input and said pulse generator serves to control subsequent operation of said switching means.
A method for converting a direct current at a first voltage level to a second predetermined direct current voltage level comprising the steps of:
- initially interrupting the input current through a primary inductance of a choke having a start inductance and a secondary inductance, so that the voltage is induced in said start inductance which initially controls the interruption of current through said primary inductance;
- rectifying the voltage across the secondary inductance;
- generating a pulsed signal related to the rectified output voltage from the secondary inductance;
- subsequently controlling the rate of current flow through said primary inductance with said pulsed signal when the rectified secondary voltage reaches a predetermined level;
- sensing the current flow through the primary inductance;
- interrupting the current flow therethrough when the current reaches a predetermined level and allowing current to commence flowing after said interruption in response to said pulsed signal;
- and
- preventing the interruption of current through said primary inductance by the voltage induced in said start inductance when said rectified voltage level reaches said predetermined level.
Dependencies are inferred from the claim text.