ELECTRONIC DEVICE FOR AVERAGE CURRENT MODE DC-DC CONVERSION

• US 20130320949A1
• Filed: 06/04/2012
• Published: 12/05/2013
• Est. Priority Date: 06/04/2012
• Status: Active Grant

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments Deutschland Gesellschaft Mit Beschrã¤Nkter Haftung (Texas Instruments, Inc.)
• Inventors: Prexl, Franz, Neuhaeusler, Juergen
• Granted Patent: US 8,841,895 B2
• Time in Patent Office: Days
• US Class Current: 323/290
• CPC Class Codes: H02M 3/158 including plural semiconductor devices as final control devices for a single load
• CPC Class Codes: H02M 3/1582 Buck-boost converters H02M3/1584 takes precedence

Abstract

An average current mode buck-boost DC to DC converter has a buck stage coupled between an input voltage source terminal and an output terminal. A boost stage is coupled between the input voltage source terminal and the output terminal. A current ramp control circuit generates a ramp signal for driving the buck and boost stages, the ramp signals being coupled to the buck and boost stages. A constant voltage related to the desired output voltage by a constant is applied directly to both a voltage control feedback loop for adjusting the output voltage and directly to an input to the current ramp control circuit, whereby the output voltage can be shifted from one voltage to another by feedforward control.

Claims

1. An electronic device for DC-DC conversion of an input voltage into an output voltage using an inductor, the electronic device comprising:

a first transconductance amplifier having an inverting input;

a non-inverting input and an output and a second transconductance amplifier having an inverting input;

a non-inverting input and an output;

a first resistor, a second resistor;

a first capacitor, a second capacitor;

a current sensing stage for sensing a value of a current through the inductor and a current ramp control stage for controlling the ramps of the current through the inductor in a buck-mode and a boost-mode;

wherein the inverting input of the first transconductance amplifier is coupled to receive a feedback voltage that is derived from the output voltage;

the output of the first transconductance amplifier is coupled to the non-inverting input of the second transconductance amplifier and to a first side of the first resistor;

the second side of the first resistor is coupled to a first side of the first capacitor;

the second side of the first capacitor is coupled to ground;

the inverting input of the second transconductance amplifier is coupled to an output of the current sensing stage;

the output of the second transconductance amplifier is coupled to the current ramp control stage and to a first side of the second resistor;

the second side of the second resistor is coupled to a first side of the second capacitor;

the second side of the second capacitor is coupled to receive a first reference voltage;

the non-inverting input of the first transconductance amplifier is coupled to receive a second reference voltage; and

wherein the first reference voltage is proportional to the second reference voltage so as to change the output voltage of the electronic device by adjusting the first and the second reference voltage level.

2. The electronic device according to claim 1, wherein the first reference voltage is derived from a control voltage by a first resistive voltage divider and second reference voltage is derived from the control voltage by a second resistive voltage divider.

3. An average current mode buck-boost DC to DC converter comprising:

a buck stage coupled between an input voltage source terminal and an output terminal;

a boost stage coupled between the input voltage source terminal and the output terminal;

a current ramp control circuit generating a ramp signal for driving the buck and boost stages, the ramp signals being coupled to the buck and boost stages;

a constant voltage related to the desired output voltage by a constant being applied directly to both a voltage control feedback loop for adjusting the output voltage and directly to an input to the current ramp control circuit, whereby the output voltage can be shifted from one voltage to another by feedforward control.

4. The DC to DC converter of claim 3, wherein the duty cycle D equals VOUT/F in steady state operation, where F is a proportionality factor.

5. The DC to DC converter of claim 4, wherein the duty cycle is directly set via the voltage VCON.

6. The DC to DC converter of claim 5, wherein the duty cycle D=VCON*G/F where G=VOUT/VCON.

7. The DC to DC converter of claim 3, wherein the current ramp control circuit provides rising and falling ramps.

8. The DC to DC converter of claim 7, wherein a buck boost non-overlap control circuit moves the ramp signals apart so that they do not overlap.

9. The DC to DC converter of claim 8, wherein the buck boost non-overlap control circuit maintains the ramps close together without overlap.

10. The DC to DC converter of claim 6, wherein the current ramp control circuit provides rising and falling ramps.

11. The DC to DC converter of claim 10, wherein a buck boost non-overlap control circuit moves the ramp signals apart so that they do not overlap.

12. The DC to DC converter of claim 8, wherein the buck boost non-overlap control circuit maintains the ramps close together without overlap.

13. A method of operating an average current mode buck-boost DC to DC converter comprising:

generating a voltage VCON related to a desired output voltage by a constant;

applying VCON to a buck-boost current ramp control and substantially simultaneously applying VCON as a reference voltage for a voltage control loop;

whereby a duty cycle of the converter can be directly set.

14. The method of operating the DC to DC converter of claim 13, wherein the duty cycle D equals VOUT/F in steady state operation, where F is a proportionality factor.

15. The method of operating the DC to DC converter of claim 14, wherein the duty cycle is directly set via the voltage VCON.

16. The method of operating the DC to DC converter of claim 15, wherein the duty cycle D=VCON*G/F where G=VOUT/VCON.

17. The method of operating the DC to DC converter of claim 15, wherein the current ramp control circuit provides rising and falling ramps.

18. The method of operating the DC to DC converter of claim 17, wherein a buck boost non-overlap control circuit moves the ramp signals apart so that they do not overlap.