Micropower switch controller for use in a hysteretic current-mode switching regulator

• US 5,825,165 A
• Filed: 04/03/1996
• Issued: 10/20/1998
• Est. Priority Date: 04/03/1996
• Status: Expired due to Term

• Current Assignee: Fairchild Semiconductor Corporation (ON Semiconductor Corporation)
• Original Assignee: Micro Linear Corporation (Qorvo, Inc.)
• Inventors: Kitching, Christopher, Wymelenberg, Joseph Vanden
• Primary Examiner(s): NGUYEN, MATTHEW VAN
• Application Number:
  US08/627,115
• Time in Patent Office: 930 Days
• Field of Search: 323/222, 323/282, 323/284, 323/273, 323/274, 323/907
• US Class Current: 323/282
• CPC Class Codes: H02M 1/0022 the disturbance parameters being input voltage fluctuations
• CPC Class Codes: H02M 3/1563 without using an external clock H02M3/158 takes precedence

Abstract

A micropower switching regulator for use in a hysteretic current-mode switching mode power converter monitors a fraction of the voltage output to the load in order to maintain the output voltage at a desired level. When the output voltage is less than the desired level, a proportional current is generated, representative of the difference between the output voltage and the desired level, and used to control the switching regulator causing an inductor to alternate between charging to a hysteretic maximum current level and then discharging to a hysteretic minimum current level, controlled by the switching regulator, until the output voltage is greater than the desired level. The hysteretic maximum and minimum current levels vary as the proportional current varies, so that as the difference between the output voltage and the desired voltage increases or decreases, the current level in the inductor will also increase or decrease, responsively. The inductor is charged and discharged continuously during a continuous conduction mode. During a discontinuous conduction or idle mode, the switching regulator is only turned on when necessary to maintain the output voltage at a level equal to or greater than the desired voltage level. Power is only drawn by the switching regulator, from the input source, when the proportional current is generated, because there is a difference between the output voltage and the desired voltage. In this manner the power provided by the input source is conserved and the desired output voltage level is maintained efficiently.

Claims

1. A power supply circuit for providing a regulated voltage level by drawing power from a power source, the power supply circuit comprising:

a. a switch coupled to charge a magnetic element with energy by drawing an input current from the power source and coupled to discharge the magnetic element into a charge storage device for forming the regulated voltage level across the charge storage device;

b. an error amplifier coupled to compare the regulated voltage level to a reference level; and

c. a control circuit coupled to control the switch according to an output of the error amplifier and according to a level of the input current wherein the control circuit does not draw any quiescent current when the regulated voltage level is higher than the reference level.

2. The power supply circuit according to claim 1 wherein the error amplifier provides a control signal to the control circuit wherein the control circuit is responsive to the control signal only when the regulated voltage level is lower than the reference level.

3. The power supply circuit according to claim 1 wherein the error amplifier provides a control current to the control circuit wherein the control current is representative of a difference between the regulated voltage level and the reference level only when the regulated voltage level is lower than the reference level.

4. The power supply circuit according to claim 3 wherein the control circuit turns on the switch when the current through the inductor reaches a lower threshold and turns off the switch when the current through the inductor reaches an upper threshold.

5. The power supply circuit according to claim 4 wherein the lower and upper thresholds vary according to a difference between the regulated voltage level and the reference level.

6. The power supply circuit according to claim 5 wherein a difference between the lower and upper thresholds remains substantially constant despite variations in the difference between the regulated voltage level and the reference level.

7. The power supply circuit according to claim 6 wherein the difference between the lower and upper thresholds remains substantially constant despite variations in temperature.

8. The power supply circuit according to claim 1 wherein the control circuit comprises a plurality of transistors and resistors, all of which are non-conducting when the regulated voltage level is higher than the reference level.

9. The power supply circuit according to claim 1 wherein the error amplifier comprises a transconductance amplifier for forming a control current wherein the control current has a level other than substantially zero only when the regulated voltage level is lower than the reference level.

10. The power supply circuit according to claim 9 wherein the control circuit is coupled to receive the control current from the transconductance amplifier via an input node of the control circuit wherein the input node comprises a control terminal of a transistor wherein the transistor constrains the control current signal to a single polarity.

11. The power supply circuit according to claim 10 wherein the transistor is a bipolar transistor and the control terminal is a base of the bipolar transistor.

12. The power supply circuit according to claim 11 wherein a collector of the bipolar transistor is coupled to the base of the bipolar transistor.

13. The power supply circuit according to claim 1 wherein the control circuit turns on the switch when the current through the inductor reaches a lower threshold and turns off the switch when the current through the inductor reaches an upper threshold.

14. The power supply circuit according to claim 13 wherein the lower and upper thresholds vary according to a difference between the regulated voltage level and the reference level.

15. The power supply circuit according to claim 14 wherein a difference between the lower and upper thresholds remains substantially constant despite variations in the difference between the regulated voltage level and the reference level.

16. The power supply circuit according to claim 15 wherein the difference between the lower and upper thresholds remains substantially constant despite variations in temperature.

17. A power supply circuit for providing a regulated voltage level by drawing power from a power source, the power supply circuit comprising:

a. a switch coupled to charge a magnetic element with energy by drawing an input current from the power source and coupled to discharge the magnetic element into a charge storage device for forming the regulated voltage level across the charge storage device;

b. an error amplifier coupled to compare the regulated voltage level to a reference level; and

c. a control circuit coupled to control the switch according to an output of the error amplifier wherein the control circuit does not draw any quiescent current when the regulated voltage level is higher than the reference level.

18. The power supply circuit according to claim 17 wherein the error amplifier provides a control signal to the control circuit wherein the control circuit is responsive to the control signal only when the regulated voltage level is lower than the reference level.

19. The power supply circuit according to claim 17 wherein the error amplifier provides a control signal to the control circuit wherein the control signal is representative of a difference between the regulated voltage level and the reference level only when the regulated voltage level is lower than the reference level.

20. The power supply circuit according to claim 17 wherein the control circuit comprises a plurality of transistors and resistors, all of which are non-conducting when the regulated voltage level is higher than the reference level.

21. The power supply circuit according to claim 17 wherein the error amplifier comprises a transconductance amplifier for forming a control current wherein the control current has a level other than substantially zero only when the regulated voltage level is lower than the reference level.

22. The power supply circuit according to claim 21 wherein the control circuit is coupled to receive the control current from the transconductance amplifier via an input node of the control circuit wherein the input node comprises a control terminal of a transistor wherein the transistor constrains the control current signal to a single polarity.

23. The power supply circuit according to claim 22 wherein the transistor is a bipolar transistor and the control terminal is a base of the bipolar transistor.

24. The power supply circuit according to claim 23 wherein a collector of the bipolar transistor is coupled to the base of the bipolar transistor.

25. A switch for a hysteretic current-mode switching regulator having an input and an output comprising:

a. a first pnp bipolar transistor having a first base, a first emitter, and a first collector;

b. a second pnp bipolar transistor having a second base coupled to the first base, a second emitter, and a second collector;

c. a third pnp bipolar transistor having a third base coupled to the first base, a third emitter coupled to the first emitter, and a third collector;

d. a fourth pnp bipolar transistor having a fourth base coupled to the first base, a fourth emitter coupled to the first emitter, and a fourth collector;

e. a fifth pnp bipolar transistor having a fifth base coupled to the first base, a fifth emitter coupled to the first emitter, and a fifth collector coupled to the fifth base;

f. a base reference voltage;

g. a sixth npn bipolar transistor having a sixth base, a sixth emitter coupled to the base reference voltage, and a sixth collector coupled to the sixth base and the first collector;

h. a seventh npn bipolar transistor having a seventh base coupled to the sixth base, a seventh emitter coupled to the base reference voltage, and a seventh collector coupled to the second collector;

i. an eighth npn bipolar transistor having an eighth base coupled to the seventh collector, an eighth emitter coupled to the base reference voltage, and an eighth collector coupled to the third collector;

j. a ninth npn bipolar transistor having a ninth base coupled to the eighth collector, a ninth emitter coupled to the base reference voltage, and a ninth collector coupled to the fourth collector;

k. a tenth npn bipolar transistor having a tenth base, a tenth emitter coupled to the base reference voltage, and a tenth collector coupled to the tenth base;

l. an eleventh npn bipolar transistor having an eleventh base coupled to the fourth collector, an eleventh emitter coupled to the tenth collector, and an eleventh collector coupled to the eleventh base;

m. a twelfth npn bipolar transistor having a twelfth base coupled to the fourth collector, a twelfth emitter, and a twelfth collector coupled to the fifth collector;

n. a thirteenth npn bipolar transistor having a thirteenth base coupled to the twelfth base, a thirteenth emitter, and a thirteenth collector coupled to the first emitter;

o. a fourteenth NMOS transistor having a fourteenth gate coupled to the thirteenth base, a fourteenth source coupled to the base reference voltage, and a fourteenth drain forming a switch having an on position and an off position;

p. a first resistor coupling the input to the second emitter;

q. a second resistor coupling the input to the first emitter;

r. a third resistor coupling the twelfth emitter to the thirteenth emitter;

s. a fourth resistor coupling the thirteenth emitter to the base reference voltage;

t. an inductor coupling the second emitter to the fourteenth drain for storing energy when the fourteenth transistor is in the on position;

u. a rectifying diode having an anode and a cathode, the cathode coupled to the fourteenth drain, the anode coupled to the output;

v. a capacitor coupling the output to the base reference voltage the capacitor for storing energy from the inductor when the fourteenth transistor is in the off position and for providing energy to a load when the fourteenth transistor is in the on position;

w. a fifth resistor having a first and second terminal, the first terminal coupled to the output;

x. a sixth resistor coupling the second terminal to the base reference voltage;

y. an output reference voltage; and

z. a transconductance amplifier having a positive input node, a negative input node and a transconductance output node;

the positive input node coupled to the output reference voltage, the negative input node coupled to the second terminal, and the transconductance output node coupled to the first base.