High voltage transistorized power supply employing switching regulator and d.c.-a.c. converter circuitry

• US 3,914,679 A
• Filed: 04/15/1974
• Issued: 10/21/1975
• Est. Priority Date: 04/15/1974
• Status: Expired due to Term

• Current Assignee: James F. Sullivan
• Original Assignee: James F. Sullivan
• Inventors: Sullivan, James F.
• Primary Examiner(s): Goldberg, Gerald
• Application Number:
  US05/461,081
• Time in Patent Office: 554 Days
• Field of Search: 321/2,18 323/DIG.1,17 178/DIG.11
• US Class Current: 363/25
• CPC Class Codes: H02M 3/3372 of the parallel type

Abstract

An electronic power supply employs a high voltage transistor in a switching regulator, coupled to a d.c.-a.c. converter stage employing two high voltage transistors, and an auxiliary transformer for initial activation of the supply. A transformer secondary winding is employed in conjunction with diodes within the d.c.-a.c. converter to prevent both transistors in this stage from operating simultaneously. A slow voltage buildup sequencing circuit is employed within the control loop of the switching regulator to prevent the occurrence of an unwanted overvoltage fault condition.

Claims

1. An electronic power supply comprising:

input rectifier and filter means coupled to an alternating current (a.c.) input to convert said alternating current into direct current, said input rectifier and filter means including electrical storage means for providing ridethrough capability for the power supply;

switching regulator means coupled to said input rectifier and filter means, said switching regulator means including a first high voltage transistor with its collector connected to the relatively positive output line from the input rectifier and filter means and its emitter coupled to a first terminal of a choke element for limiting peak currents emitted by the emitter of said first transistor;

means to convert direct current to alternating current coupled to said switching regulator means, said d.c.-a.c. converter means including a second and a third high voltage transistor, a transformer and means to inhibit simultaneous turn-on of said second and said third transistors, said transformer having a primary winding with a center tap connected to a second terminal of said choke element, opposite terminals of said primary winding connected to the collectors of said second and third transistors respectively, the emitters of said second and said third transistors connected to the relatively negative output line from said input rectifier and filter means, said inhibiting means including a secondary winding of said transformer and a pair of diodes coupled between each terminal of said secondary winding and the base of each of said second and said third transistors respectively;

a plurality of output rectifier and filter circuits, each of which is coupled to said d.c.-a.c. converter means and each of which produces a preselected output voltage;

a control loop coupled to said switching regulator means and to at least one of said output rectifier and filter circuits, said control loop providing a regulation signal to said first transistor for varying the duty cycle of said first transistor, said regulation signal responsive to the voltage level of said one output rectifier and filter circuit; and

an auxiliary transformer circuit coupled to the a.c. input and to said control loop, said auxiliary transformer circuit providing power to said control loop before said output voltages have reached their operating levels.

2. The power supply of claim 1 wherein said control loop further includes fault detection means for shutting off said power supply and a slow voltage build-up sequencing circuit for preventing erroneous generation of an overvoltage fault condition signal during initial turn-on of the power supply.

3. The power supply of claim 2 wherein said d.c.-a.c. converter means further comprises an oscillator for driving said converter means, said oscillator comprising a uni-junction transistor circuit, a dual flip-flop, two NPN transistors, and a second transformer, said unijunction transistor circuit providing a switching signal to said dual flip-flop, said two NPN transistors responsive to complementary outputs of said dual flip-flops respectively, said two NPN transistors alternately driving said transformer to opposite polarity, said second transformer having a secondary winding coupled to the bases of said second and said third transistors, said fault condition signal causing an initialization of said dual flip-flop.

4. The power supply of claim 1 wherein said variation of the duty cycle of said first transistor is acHieved by producing said regulation signal by comparing in a voltage comparator the output voltage level of said one output rectifier and filter circuit with a triangular waveform generated by a uni-junction transistor circuit within said control loop.

5. The power supply of claim 1 wherein said switching regulator means further comprises a capacitor coupled between the second terminal of said choke element and the relatively negative output line from the input rectifier and filter means, and a diode having its cathode coupled to said first terminal of said choke element and its anode coupled to the relatively negative output line from the input rectifier and filter means.

6. An electronic power supply comprising:

input rectifier and filter means coupled to an alternating current input to convert said alternating current input into direct current, said input rectifier and filter means comprising electrical storage means for providing ridethrough capability for the power supply when the power supply is shut-off;

switching regulator means coupled to a pair of output lines from said input rectifier and filter means, said switching regulator means comprising a first high voltage transistor coupled to gate the output from said input rectifier and filter means, an inductor coupled to limit the path currents passing through said first transistor, a capacitor for filtering the output voltage of said switching regulator means, and a diode coupled so as to provide a current path when said first transistor is non-conducting;

means to convert direct current to alternating current coupled to said switching regulator means, said d.c.-a.c. converter means comprising;

a second and a third high voltage transistor;

a first transformer;

an oscillator comprising a uni-junction transistor for providing a switching signal, a dual flip-flop responsive to said switching signal, two NPN transistors responsive to complementary outputs of said dual flip-flop such that only one of said two NPN transistors is conducting at a time, and a second transformer driven by said two NPN transistors; and

means to inhibit the simultaneous turn-on of said second and said third high voltage transistors comprising a secondary winding of said first transformer and a pair of diodes coupling each terminal of said secondary winding to the base of each of said second and said third high voltage transistors respectively;

a plurality of output rectifier and filter circuits, each of which is coupled to a secondary winding of said first transformer and each of which produces a preselected output voltage;

a control loop coupled to said switching regulator means and to at least one of said output rectifier and filter circuits, said control loop providing a regulation signal responsive to the output voltage level of said one output rectifier and filter circuit and applied to said first high voltage transistor to vary the duty cycle of said first high voltage transistor, said regulation signal obtained by comparing in a voltage comparator the output voltage level of said one output rectifier and filter means with a triangular waveform generated by a uni-junction transistor within said control loop;

said control loop further comprising fault detection means for shutting off said power supply and a slow voltage build-up sequencing circuit for preventing the erroneous generation of an overvoltage fault condition during initial turn-on of the power supply, said slow voltage build-up sequencing circuit comprising a pair of transistors connected collector-to-base, a grounded capacitor coupled to a pair of transistors, and a diode coupled to said capacitor and said fault detection means; and

an auxiliary transformer circuit coupled to the a.c. input and to said control loop for providing power to said control loop before said output voltages have reached their operating levels.