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

• Current Assignee: National Semiconductor Corporation (Texas Instruments, Inc.)
• Original Assignee: National Semiconductor Corporation (Texas Instruments, Inc.)
• Inventors: Szepesi, Tamas S.
• Primary Examiner(s): Beha, Jr., William H.
• Application Number:
  US07/065,584
• Time in Patent Office: 1,071 Days
• Field of Search: 323/272, 323/282, 323/284-281, 323/300
• US Class Current: 323/222
• CPC Class Codes: H02M 3/156 with automatic control of output voltage or current, e.g. switching regulators
• CPC Class Codes: H03F 2200/351 Pulse width modulation being used in an amplifying circuit

Abstract

An hysteretic current-mode controlled DC to DC converter has an input voltage, an output voltage and a control switch. The switch alternately coupled the input voltage into an energy storage inductor. It is controlled by an hysteretic conparater sensing the current of the inductor and having turn-on and turn-off limits. The limits are symmetrical about an average inductor current. The limits are adjusted by simple non-closed-loop methods to maintain an approximately constant frequency of oscillation. The average inductor current is controlled by an error amplifier to maintain a constant output voltage. The two controls are independent.

Claims

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##

2. 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 establishes a duty cycle proportional control having;

(1) a controlled switch having a first pole and a second pole, said controlled switch being controlled by a switching signal for switching said controlled switch between said first pole and said second pole, said first pole being coupled to a first voltage and said second pole coupled to a second voltage;

(2) a voltage filter and storage means coupled to a wiper of said controlled switch; and

(3) a driver means coupled to said filter and storage means for forming said control current.

3. An hysteretic current-mode controlled stable frequency DC to DC boost 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 establishes a duty cycle proportional control having;

(1) a controlled switch having a first pole and a second pole, said controlled switch being controlled by a switching signal for switching said controlled switch between said first pole and said second pole, said first pole being coupled to a first voltage and said second pole coupled to a second voltage;

(2) a voltage filter and storage means coupled to a wiper of said controlled switch; and

(3) a driver means coupled to said filter and storage means for forming said control current.

4. An hysteretic current-mode controlled stable frequency DC to DC buck-boost 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 establishes a duty cycle proportional control having;

(1) a controlled switch having a first pole and a second pole, said controlled switch being controlled by a switching signal for switching said controlled switch between said first pole and said second pole, said first pole being coupled to a first voltage and said second pole coupled to a second voltage;

(2) a voltage filter and storage means coupled to a wiper of said controlled switch; and

(3) a driver means coupled to said filter and storage means for forming said control current.