US 6,608,521 B1 · Pulse width modulation regulator control circuit having precise frequency and amplitude control

Abstract

A control circuit (50) for a switch mode power converter having precise control of amplitude and frequency that does not exhibit overshoot error nor undershoot error during a fast charge cycle nor a fast discharge cycle, respectively. In a first embodiment, the control circuit (50) does not exhibit undershoot error during a fast discharge cycle. The control circuit (50) comprises an oscillator (70) for providing a periodic carrier signal comprising a sawtooth wave output signal (VST). The oscillator (70) includes a capacitor (CT2) charged and discharged to the power supply voltage (VCC) to provide the sawtooth wave output signal (VST). In addition, the oscillator (70) includes a switching circuit (65) coupled to the reference voltage level (Vref). The control circuit (50) further includes a gain circuit (64) having a reference voltage input (Vref2), voltage input (Vin) and an output (Out). The reference voltage input (Vref2) receives the reference voltage(Vref). The voltage input (Vin) connects to the capacitor (CT2). The output (Out) of the gain circuit (64) connects to the switching circuit (65) to provide feedback proportional to the analog error signal related to the difference between the sawtooth wave output signal (VST) and the predetermined reference voltage level (Vref).

Claims12

Dependent claims

A control circuit for a switch mode regulator having a fast discharge cycle, the control circuit having a reference voltage level and a power supply, comprising:

an oscillator for providing a periodic carrier signal comprising a sawtooth wave output signal, the oscillator having a first capacitor charged and discharged to the reference voltage to provide the sawtooth wave output signal and a switching circuit coupled to the reference voltage level;
and
a gain circuit having a reference voltage input, voltage input and an output, the reference voltage input coupled to receive the reference voltage, the voltage input coupled to the first capacitor, the output coupled to the switching circuit to provide feedback proportional to the analog error signal related to the difference between the sawtooth wave output signal and the predetermined reference voltage level.

A control circuit for a switch mode power converter having a reference voltage, a power supply voltage and ground, comprising:

a voltage divider circuit having an input and an output, the input coupled to receive the reference voltage;
a first comparator having a positive input, a negative input, and an output, the positive input coupled to receive the reference voltage;
a second comparator having a positive input, a negative input, and an output, the positive input coupled to the negative input of the first comparator, the negative input coupled to the output of the voltage divider circuit;
a first capacitor coupled between the negative input of the second comparator and ground;
a reset flip-flop having a set input, a reset input, an inverting output and a non-inverting output, the set input coupled to the output of the second comparator, the reset input coupled to the output of the first comparator;
a first current source coupled to the power supply voltage to provide a charge current during the charge cycle;
a first resistor coupled between the first current source and ground;
a second current source to provide a charge current during the discharge cycle;
a second resistor coupled between the second current source and ground;
a second capacitor coupled between ground and the negative input of the first comparator;
a first transistor having a gate, a drain and a source, the drain coupled to the first current source, the source coupled to the second capacitor, the drain coupled to the non-inverting output of the reset flip-flop;
a second transistor having a gate, a drain and a source, the drain coupled to the second capacitor, the source coupled to the second current source, the gate coupled to the inverting output of the reset flip-flop;
a third transistor having a gate, a drain and a source, the source coupled to receive the reference voltage, the gate coupled to the output of the gain circuit;
a third resistor coupled to the drain of the third transistor and the negative input of the second comparator;
and
a gain circuit having a first and second input and an output, the first coupled to receive the reference voltage, the second input coupled to the second capacitor, the output coupled to the gate of the third transistor to provide feed back proportional to the voltage error.

13 more elements

A control circuit for a switch mode regulator, having a fast charge cycle, the control circuit having a reference voltage level and a power supply, comprising:

an oscillator for providing a periodic carrier signal comprising a sawtooth wave output signal, the oscillator having a first capacitor charged and discharged to the power supply voltage to provide the sawtooth wave output signal and a switching circuit coupled to the reference voltage level;
and
a gain circuit having a reference voltage input, voltage input and an output, the reference voltage input coupled to receive the reference voltage, the voltage input coupled to the first capacitor, the output coupled to the switching circuit to provide feedback proportional to the analog error signal related to the difference between the sawtooth wave output signal and the predetermined reference voltage level.

A control circuit for a switch mode power converter having a reference voltage, a power supply voltage and ground, comprising:

a voltage divider circuit having an input and an output, the input coupled to receive the reference voltage;
a first comparator having a positive input, a negative input, and an output, the positive input coupled to receive the reference voltage;
a second comparator having a positive input, a negative input, and an output, the positive input coupled to the negative input of the first comparator, the negative input coupled to the output of the voltage divider circuit;
a first capacitor coupled between the negative input of the second comparator and ground;
a reset flip-flop having a set input, a reset input, an inverting output and a non-inverting output, the set input coupled to the output of the second comparator, the reset input coupled to the output of the first comparator;
a first current source coupled to the power supply voltage to provide a charge current during the charge cycle;
a first resistor coupled between the first current source and ground;
a second current source to provide a charge current during the discharge cycle;
a second resistor coupled between the second current source and ground;
a second capacitor coupled between ground and the negative input of the first comparator;
a first transistor having a gate, a drain and a source, the drain coupled to the first current source, the source coupled to the second capacitor, the drain coupled to the non-inverting output of the reset flip-flop;
a second transistor having a gate, a drain and a source, the drain coupled to the second capacitor, the source coupled to the second current source, the gate coupled to the inverting output of the reset flip-flop;
a third transistor having a gate, a drain and a source, the source coupled to receive the reference voltage, the gate coupled to the output of the gain circuit;
a third resistor coupled to the drain of the third transistor and the negative input of the second comparator;
and
a gain circuit having a first and second input and an output, the first coupled to receive the reference voltage, the second input coupled to the second capacitor, the output coupled to the gate of the third transistor to provide feed back proportional to the voltage error.

13 more elements

Dependencies are inferred from the claim text.

Pulse width modulation regulator control circuit having precise frequency and amplitude control

Life of this patent

Pulse width modulation regulator control circuit having precise frequency and amplitude control

Life of this patent

Abstract

Claims12