Current mode switching regulator configured such that a measuring resistor is not needed to measure the current at an inductor

• US 6,222,356 B1
• Filed: 04/01/1999
• Issued: 04/24/2001
• Est. Priority Date: 04/01/1998
• Status: Expired due to Term

• Current Assignee: Infineon Technologies AG
• Original Assignee: Siemens AG
• Inventors: Taghizadeh-Kaschani, Karim-Thomas
• Primary Examiner(s): Riley, Shawn
• Application Number:
  US09/283,903
• Time in Patent Office: 754 Days
• Field of Search: 323/288, 323/284, 323/285, 323/290, 323/293
• US Class Current: 323/288
• CPC Class Codes: H02M 1/0009 Devices or circuits for detecting current in a converter
• CPC Class Codes: H02M 3/1563 without using an external clock H02M3/158 takes precedence

Abstract

The novel current-mode switching regulator does not determine the load current by picking off a measurement voltage at a measuring resistor, as in the conventional prior art. Instead, the voltage drop across the inductor which is required in any case is picked off as the measurement voltage. A regulating signal derived from the load current is determined, by integration with respect to time, with a voltage-controlled current source. The regulating signal is fed back, as a regulated variable, into regulators of the inner control loop. In this way, it is possible to dispense with the measuring resistor. An additional compensation device makes it possible, moreover, to compensate for a regulation deviation in the desired potential of the outer control loop.

Claims

1. A current-mode switching regulator, comprising:

a first regulating device for voltage regulation and a second regulating device for load current regulation, each of said first and second devices having a first input, a second input, and an output, and whereby

said first input of said first regulating device is connected to receive a reference signal and said second input of said first regulating device is connected to receive an output signal of the current-mode switching regulator, as a regulated variable; and

said output of said first regulating device is connected to said first input of said second regulating device;

a power switch connected to said second regulating device and controlled by a control signal of said second regulating device, said power switch having a load path connected between a first supply potential and a second supply potential;

a choke device connected in said load path of said power switch; and

an integrator connected to said choke device and to said second regulating device, said integrator generating a regulating signal by integrating, with respect to time, an inductor voltage dropping across said choke device, said regulating signal mirroring a load current and being coupled, as regulated variable, into said second input of said second regulating device.

2. The switching regulator according to claim 1, wherein said integrator is a voltage-controlled current source.

3. The switching regulator according to claim 1, wherein said integrator is a first transconductance amplifier with a capacitive element connected at an output thereof.

4. The switching regulator according to claim 1, wherein said integrator is an operational amplifier with a capacitive element connected to an output thereof.

5. The switching regulator according to claim 1, wherein said second regulating device includes a pulse width modulator with at least a pulse width-modulated comparator and a clocked storage device.

6. The switching regulator according to claim 1, wherein said power switch is a transistor selected from the group consisting of field effect controlled transistors and bipolar transistors.

7. The switching regulator according to claim 1, wherein the switching regulator has a step-down converter.

8. The switching regulator according to claim 1, which comprises a capacitor for signal smoothing connected in said load path.

9. The switching regulator according to claim 1, which further comprises a compensation device connected to said second regulating device for generating, if a regulation deviation occurs in said first regulating device, a compensation signal derived from the regulation deviation, wherein the compensation signal is superposed on the regulating signal derived from the load current and is coupled, as regulated variable, into said second regulating device.

10. The switching regulator according to claim 9, wherein said compensation device has an output signal with a limited output quantity.

11. The switching regulator according to claim 9, wherein said compensation device compensates in a slow-acting manner, with said integrating element of said first regulating device acting as an inertia-determining element.

12. The switching regulator according to claim 1, wherein said integrator is a first transconductance amplifier with a capacitive integrating element connected at an output thereof, and including a clocked current source outputting a pulsed current to said integrating element, wherein the pulsed current is integrated together with the regulating signal derived from the load current and is coupled, as a regulated variable, into said second regulating device.

13. The switching regulator according to claim 1, wherein said choke device is an inductor.