Overvoltage protection arrangement for power converters

Claim 1

Power converter apparatus comprising in combination, a. a nonregulated source of direct current energy having a normal voltage level and including a fusible element, b. a transistorized regulator circuit means connected across said source and operable to produce and maintain an output at a first preselected voltage level, c. a transistorized inverter circuit means connected to the output of said regulator circuit means and operable when energized to provide an alternating current voltage output, d. a rectifier means connected to the output of said inverter circuit means and operable to transform said alternating current output into a direct current output at a final preselected voltage level, e. a normally nonconducting controlled rectifier device having a control electrode and connected across said source poled to pass current from said source when an activating signal is applied to said control electrode, said current being sufficient to open said fusible element, f. a first Zener diode having a reverse breakdown voltage selected in the range between said normal voltage level and the breakdown potential of the transistoRs in said regulator circuit means, 1. said first Zener diode connected in multiple with said controlled rectifier device and poled to normally block flow of current from said source, g. the control electrode of said rectifier device connected to receive an activating signal through said first Zener diode, when its reverse breakdown voltage is exceeded by the voltage level of said source, to protect the transistors of said regulator circuit means from a continued overvoltage condition, h. a second Zener diode having a reverse breakdown voltage selected above said first preselected voltage level but below the breakdown potential of the transistors in said inverter circuit means, 1. said second Zener diode connected across the output of said regulator circuit means and poled to normally block any flow of current therethrough, i. the control electrode of said controlled rectifier device also connected to receive an activating signal through said second Zener diode, if the output of said regulator circuit means exceeds said first preselected voltage level, to protect the transistors of said inverter circuit means from the application of excessive operating voltage and to prevent an overvoltage output from said rectifier means, j. an inductor connected in each lead from said direct current source to be in series with the multiple paths through said controlled rectifier and said regulator circuit means, and k. a capacitor means connected in multiple with said controlled rectifier, l. the inductor-capacitor circuit path having transmission characteristics for providing a bypass for transient voltage surges having a potential level sufficient to damage the transistors of said apparatus.