Halogen power converter with complementary switches

A power converter for use in a ballast supplying low voltage a.c. current, to a load circuit that incorporates a low voltage lamp, from a high voltage a.c. source comprising:

• (a) a full-wave rectifier circuit for connection to a bus conductor and a reference conductor;
• (b) a pulsating-d.c.-to-a.c. converter circuit comprising first and second switches serially connected between said bus conductor and said reference conductor, being connected together at a common node through which said a.c. current flows and having a shared control node, the voltage between said control node and said common node determining the conduction state of the associated switch;
• (c) the load circuit comprising:
• (i) a transformer and a capacitor serially connected between said common node and said reference conductor, the transformer being of sufficient leakage inductance to provide short circuit protection;
• and
• (ii) a low voltage lamp connected to nodes such that it bridges the common winding of said autotransformer;
• and
• (d) a regenerative control circuit bridging said common node and said control node comprising:
• (i) a first driving inductor mutually coupled to said transformer in such manner that a voltage is induced therein which is proportional to the instantaneous rate of change of said a.c. current;
• (ii) a second serially connected timing inductor;
• and
• (iii) a serially connected timing capacitor, the timing capacitor and timing inductor selected such that their serially combined timing constant determines the frequency of operation of said power converter.

A power converter for use in a ballast supplying low voltage a.c. current, to a load circuit that incorporates a low voltage lamp, from a high voltage source comprising:

• (a) an a.c.-to-pulsating-d.c. converter circuit comprising a full-wave rectifier bridged with a small first capacitor, for connection to a bus conductor and a reference conductor;
• (b) a pulsating-d.c.-to-a.c. converter circuit comprising first and second switches serially connected between said bus conductor and said reference conductor;
• being connected together at a common node through which said a.c. current flows;
• and having a shared control node, the voltage between said control node and said common node determining the conduction state of the associated switch;
• (c) first and second resistors serially connected between said bus and reference conductors, with their intermediate node connected to said control node;
• (d) a third resistor connected between said common node and one of said bus conductor and said reference conductor;
• (e) an autotransformer with one end connected to said common node;
• (f) a second capacitor connected between said reference conductor and the remaining end of said autotransformer;
• (g) a first lamp node connected to the center terminal of said autotransformer;
• (h) a second lamp node connected to the common point between said autotransformer and said second capacitor with provision for connecting said low voltage lamp between said first and second lamp nodes;
• (i) a third capacitor connected in parallel with said third resistor;
• (j) a fourth capacitor connected between said common node and said control node;
• (k) a first driving inductor mutually coupled to said autotransformer in such manner that a voltage is induced therein which is proportional to the instantaneous rate of change of said a.c. current;
• (l) a second timing inductor connected at one end to said driving inductor;
• and
• (m) a fifth timing capacitor connected serially between said control node and the remaining end of said timing inductor being selected such that the timing constant of said timing inductor serially connected to timing capacitor determine the frequency of operation of said power converter.