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Apparatus for converting DC to DC having non-feed back variable hysteretic current-mode control for maintaining approximately constant frequency

  • US 4,929,882 A
  • Filed: 06/23/1987
  • Issued: 05/29/1990
  • Est. Priority Date: 06/23/1987
  • Status: Expired due to Term
First Claim
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1. An hysteretic current-mode controlled stable frequency DC to DC buck power stage converter having an input voltage and an output voltage comprising:

  • a. a power stage circuit having;

    (1) an inductor having an inductor current for forming the output voltage;

    (2) a capacitor coupled to said inductor;

    (3) a first control switch coupled to said inductor having an open position and a closed position;

    (4) means for oscillating said switch between said open position and said closed position thereby establishing a first duty cycle, said switch in said closed position coupling said input voltage to said power stage and said switch in said open position uncoupling said input voltage from said power stage; and

    (5) feedback means for controlling a peak value of the inductor current wherein the feedback means controls an average inductor current with a control signal whereby the non-feedback means establishes the turn-on and said turn-off limits symmetrically around the control signal; and

    b. non-feedback hysteretic control circuit for controlling said inductor current having a turn-on limit for closing said switch and a turn-off limit for opening the switch, said turn-on and turn-off limits being adjustable by said non-feedback control circuit to approximately maintain a constant frequency of oscillation wherein said control circuit is a nonlinear circuit comprising;

    (1) a first node;

    (2) a first voltage coupled to said node;

    (3) a first voltage controlled current source having a first terminal and a second terminal, said first terminal coupled to said first node;

    (4) a first NPN transistor having a first emitter, a first base and a first collector, said first collector and said first base coupled to said second terminal;

    (5) a first PNP transistor having a second emitter, a second base and a second collector, said second emitter coupled to said first emitter;

    (6) a second node;

    (7) ground coupled to said second node;

    (8) said second base and said second collector coupled to said second node;

    (9) a second PNP transistor having a third emitter, a third base and a third collector, said third emitter coupled to said first node;

    (10) a second NPN transistor having a fourth emitter, a fourth base and a fourth collector, said fourth collector coupled to said third collector and to said third base;

    (11) a third PNP transistor having a fifth emitter, a fifth base and a fifth collector, said fifth emitter coupled to said fourth emitter, said fifth base coupled to said second terminal and said fifth collector coupled to said second node;

    (12) a fourth PNP transistor having a sixth emitter, a sixth base and a sixth collector, said sixth emitter coupled to said first node and said sixth base coupled to said third base;

    (13) a third node coupled to said sixth collector;

    (14) a second voltage controlled current source having a third terminal and a fourth terminal, said third terminal coupled to said first node and said fourth terminal coupled to said fourth base;

    (15) a third NPN transistor having a seventh emitter, a seventh base and a seventh collector, said seventh collector and said seventh base coupled to said fourth terminal;

    (16) a fourth NPN transistor having an eighth emitter, an eighth base and an eighth collector, said eighth collector and said eighth base coupled to said seventh emitter;

    (17) a fifth PNP transistor having a ninth emitter, a ninth base and a ninth collector, said ninth emitter coupled to said eighth emitter;

    (18) a sixth PNP transistor having a tenth emitter, a tenth base and a tenth collector, said tenth emitter coupled to said ninth base and said ninth collector and said tenth collector and said tenth base coupled to said second node; and

    (19) a third voltage controlled current source having a fifth terminal and a sixth terminal, said fifth terminal coupled to said third node and said sixth terminal coupled to said second node, whereby said control current is generated in said third node to implement a hysteretic current control equation ##EQU22##

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