# US 7,612,544 B2 · Linearized controller for switching power converter

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- Number: US 7,612,544 B2
- Document ID: US7612544B2
- Status: Granted
- Kind: B2
- Application number: 11/903,382
- Filed: 2007-09-20
- Published: 2009-03-26
- Granted: 2009-11-03
- Earliest claimed: 2007-09-20
- Assignees: Analog Devices, Inc.
- Inventors: A. Paul Brokaw; Marc J. Kobayashi
- Web page: https://patentgrep.com/patent/US7612544B2

## CPC

- H02M 1/08: Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters
- H02M 3/156: with automatic control of output voltage or current, e.g. switching regulators
- H02M: APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF (transformers H01F; dynamo-electric converters H02K47/00; controlling transformers, reactors or choke coils, control or regulation of electric motors, generators or dynamo-electric converters H02P)

## Abstract

A linearized controller to operate a switching power converter which includes an inductor having its first terminal coupled to a first voltage (V1) and its second terminal switched so that it alternately connects to a second, higher voltage (V2) or to a common terminal. A sawtooth voltage generator produces a ramp voltage (Vramp) having a period T and an amplitude which varies in response to a control voltage Vx, and a voltage comparator which compares Vramp to a control voltage Vy. The comparator output controls the switching such that T is divided into intervals t1 and t2, during which the second terminal is connected to the common terminal or to V2, respectively. When Vy is maintained in a fixed proportion to V1, V2 is driven to be in the same proportion to Vx, independently of changes in V1, providing a boost converter. A buck converter is similarly realized.

## Claims

### Claim 1

A controller for a power conversion circuit which includes an inductor having its first terminal coupled to a first power voltage V1 and its second terminal switched so that it alternately connects to a second, higher, power voltage V2 or to a common terminal of the two power voltages, said controller comprising:
a sawtooth voltage generator which produces a ramp voltage Vramp having a period T and an amplitude which may be varied in response to a first control voltage Vx; and
a voltage comparator arranged to compare Vramp to a second control voltage Vy, the output of the comparator arranged to control the switching of said second inductor terminal so as to divide period T into a first interval t1 during which said second terminal is connected to said common terminal and a second interval t2 during which said second terminal is connected to V2;
such that when said Vy is maintained in a fixed proportion to V1, V2 will be driven so as to be in the same proportion to Vx, independently of changes in V1, and alternatively when Vx is maintained in a fixed proportion to V2, V1 will be driven to be in the same proportion to Vy, independently of changes in V2.

### Claim 2 (depends on 1)

The controller of claim 1, wherein said second power voltage V2 is provided to said power conversion circuit as an input voltage and V1 is said conversion circuit's output voltage, said first control voltage Vx maintained in fixed proportion to V2 such that V1 is driven to be in the same proportion to Vy, independently of changes in V2.

### Claim 3 (depends on 2)

The controller of claim 2, wherein said switching network comprises:
a diode connected between said second inductor terminal and said common terminal; and
a transistor connected between said second inductor terminal and V2.

### Claim 4 (depends on 2)

The controller of claim 2, further comprising a means of providing an error signal which varies with the difference between V1 and a reference voltage, said first control voltage Vx varying with said error signal such that V1 is stabilized at a desired voltage.

### Claim 5 (depends on 1)

The controller of claim 1, wherein said first power voltage V1 is provided to said power conversion circuit as an input voltage and V2 is said conversion circuit's output voltage, said second control voltage Vy maintained in fixed proportion to V1 such that V2 is driven to be in the same proportion to Vx, independently of changes in V1.

### Claim 6 (depends on 5)

The controller of claim 5, wherein said switching network comprises:
a diode connected between said second inductor terminal and V2; and
a transistor connected between said second inductor terminal and said common terminal.

### Claim 7 (depends on 5)

The controller of claim 5, further comprising a means of providing an error signal which varies with the difference between V2 and a reference voltage, said first control voltage Vx varying with said error signal such that V2 is stabilized at a desired voltage.

### Claim 8 (depends on 1)

The controller of claim 1, wherein said switching network comprises:
a first transistor connected between said second inductor terminal and V2; and
a second transistor connected between said second inductor terminal and said common terminal, such that said power conversion circuit is a synchronous converter.

### Claim 9 (depends on 1)

The controller of claim 1, wherein Vramp toggles between a lower voltage and a higher voltage, said sawtooth voltage generator arranged such that Vramp steps up from said lower voltage to said higher voltage and ramps back down to said lower voltage during each period T.

### Claim 10 (depends on 1)

The controller of claim 1, wherein Vramp toggles between a lower voltage and a higher voltage, said sawtooth voltage generator arranged such that Vramp steps down from said higher voltage to said lower voltage and ramps back up to said higher voltage during each period T.

### Claim 11 (depends on 1)

The controller of claim 1, wherein said sawtooth generator comprises an oscillator arranged such that the slope of Vramp is proportional to said amplitude, such that T is invariant with changes in Vx.

### Claim 12 (depends on 11)

The controller of claim 11, wherein said oscillator comprises:
a P-type current mirror referred to a positive supply voltage and arranged to mirror a current applied to its input to a first node;
an N-type current mirror referred to a circuit common point and arranged to mirror a current applied to its input to a second node;
a resistor (R1) connected at its first and second terminals to the inputs of said P-type and N-type current mirrors, respectively, the current IR in said resistor mirrored to said first and second nodes and developing voltages VR1 and VR2 at said first and second terminals, respectively, said oscillator arranged such that the voltage across said resistor varies with Vx;
a third node;
a capacitor connected between said third node and said circuit common point;
a means for providing a current for discharging said capacitor to said third node which is proportional to IR;
a means for providing a current for charging said capacitor to said fifth node which is proportional to IR;
a first transistor having its control input connected to said third node and its current circuit connected between said first node and said circuit common point; and
a second transistor having its control input connected to said third node and its current circuit connected between said second node and said positive supply voltage, said oscillator arranged such that the output of said first transistor toggles when the voltage at said third node crosses VR2 and the output of said second transistor toggles when the voltage at said third node crosses VR1;
a switch arranged to block at least one of said charging and discharging currents when open; and
a means for operating said switch such that said third node oscillates between approximately VR1 and approximately VR2, such that the period of oscillation is independent of the voltage across said resistor, said third node providing said ramp voltage Vramp.

### Claim 13 (depends on 12)

The controller of claim 12, wherein said means for providing a discharging current comprises a third transistor connected to mirror a current proportional to IR to said third node, and said means for providing a charging current comprises a fourth transistor connected to mirror a current proportional to IR to said third node.

### Claim 14 (depends on 13)

The controller of claim 13, wherein said means for operating said switch comprises a flip-flop having an output, said controller arranged such that said flip-flop toggles said output when the voltage at said third node increases to VR2 and when the voltage at said third node falls to VR1, said flip-flop output connected to operate said switch.

### Claim 15 (depends on 12)

The controller of claim 12, further comprising:
a third transistor having its current circuit connected in series between the input of said P-type current mirror and said first resistor terminal; and
a fourth transistor having its current circuit connected in series between said switch and said third node, the control inputs of said third and fourth transistors connected together, said third and fourth transistors arranged such that a voltage applied to said control inputs establishes the peak voltage to which said third node oscillates.

### Claim 16 (depends on 15)

The controller of claim 15, wherein one of V1 and V2 provides said power conversion circuit's output voltage, further comprising an error amplifier which produces an output that varies with the difference between said output voltage and a reference voltage, said error amplifier output coupled to the control inputs of said third and fourth transistors such that the peak voltage to which said third node oscillates is varied as necessary to achieve an approximately constant output voltage.

### Claim 17 (depends on 16)

The controller of claim 16, said controller arranged such that said error amplifier receives said reference voltage and a signal representative of said output voltage at respective inputs such that said error amplifier output varies with the difference between said reference voltage and said representative signal.

### Claim 18 (depends on 1)

The controller of claim 1, wherein one of V1 and V2 provides said power conversion circuit's output voltage, further comprising circuitry arranged such that said controller provides current mode control of said power conversion circuit's output voltage.