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US 9,287,776 B2Granted
Low power switching mode regulator having automatic PFM and PWM operation
AssigneeTexas Instruments Incorporated
InventorTawen Mei
Life of this patent
Estimating the term…
Abstract
A circuit and method for operating a switching mode power supply. A clock is driven by a current source to generate pulses at a fixed frequency using pulse width modulation for normal load demands. For light load demands, the current to the clock is reduced, and therefore the clock generates pulses at a lower, variable frequency and fixed duration using pulse frequency modulation. Thus, depending on the load condition, either fixed frequency pulses or fixed duration pulses are automatically provided to a power stage for conversion to an output voltage.
Claims16
A switching mode power supply circuit, comprising:
- a pulse generation circuit including an oscillator that is always on, the oscillator being configured to generate pulses using pulse width modulation for a first load condition that exceeds a predefined threshold and configured to generate pulses using pulse frequency modulation for a second load condition that does not exceed the predefined threshold;
- a power stage coupled to the pulse generation circuit and configured to convert an input voltage to a modulated voltage at a switching node using pulses generated by the pulse generation circuit;
- a clock circuit coupled to the power stage and to a bias current source, the bias current source driving the clock to generate pulses to drive the power stage;
- a circuit to take away some of current generated by the bias current source to operate the switch mode power supply in a pulse frequency modulation (PFM) mode;
- and
- an output filter circuit coupled to the switching node and configured to produce an output voltage from the modulated voltage.
3 more elements
A switching mode power supply circuit, comprising:
- a pulse generation circuit including an oscillator that is always on, the oscillator being configured to generate pulses using pulse width modulation for a first load condition that exceeds a predefined threshold and configured to generate pulses using pulse frequency modulation for a second load condition that does not exceed the predefined threshold;
- a power stage coupled to the pulse generation circuit and configured to convert an input voltage to a modulated voltage at a switching node using pulses generated by the pulse generation circuit;
- an output filter circuit coupled to the switching node and configured to produce an output voltage from the modulated voltage, the pulse generation circuit comprising:
- a transconductance amplifier having an inverting input coupled to a voltage feedback signal and a non-inverting input coupled to a voltage reference for generating a compare signal as an output;
- a comparator having a non-inverting input coupled to an voltage offset signal and an inverting input coupled to the output of the transconductance amplifier for generating a reset signal as an output;
- a clock having an input driven by a drive current for generating a set signal as an output;
- a latch having a reset input coupled to the reset signal from the comparator and a set input coupled to the set signal from the clock for generating a gate drive signal as an output, the gate drive signal coupled to the power stage;
- and
- a clamp configured to drain at least some of the drive current away from the clock when the compare signal drops below the predetermined threshold,
- the clamp comprising a field effect transistor having a source coupled to the output of the transconductance amplifier, a drain coupled to the input of the clock, and a gate coupled to a clamping voltage.
7 more elements
A switching mode power supply circuit, comprising:
- a transconductance amplifier configured to compare two input voltages and generate a compare signal as an output;
- a comparator configured to compare the compare signal with an offset voltage signal and generate a reset signal as an output;
- a clock driven by a drive current and configured to generate a series of pulses as an output;
- a latch having a reset input coupled to the output of the comparator, a set input coupled to the output of the clock, and an output;
- a clamp configured to drain at least some of the drive current away from the clock when the compare signal drops below a predetermined threshold, the clamp comprising a field effect transistor having a source coupled to the output of the transconductance amplifier, a drain coupled to the input of the clock, and a gate coupled to a clamping voltage;
- a power driver having an input coupled to the output of the latch for generating an output at a switching node;
- an output filter having active elements coupled to the switching node for generating a voltage output;
- and
- a resistive divider network having at least two resistors coupled in series, the resistive divider network coupled to the voltage output.
6 more elements
A method for operating a switching mode power supply, comprising:
- generating pulses at a fixed frequency using pulse width modulation when a first signal comparing two input voltages exceeds a predetermined threshold level;
- generating pulses at a variable frequency and fixed duration when the first signal does not exceed the predetermined threshold level;
- generating the pulses at the fixed frequency and a variable frequency utilizing oscillator is always on;
- utilizing a clock circuit coupled to a power stage and to a bias current source, the bias current source driving the clock to generate the pulses to drive the power stage;
- taking away some of the current generated by the bias current source to operate the switch mode power supply and a pulse frequency modulation (PFM) mode:
- providing the pulses to the power stage, the power stage using the pulses to modulate an input voltage thereby generating a modulated output;
- and
- generating an output voltage from the modulated output using an output filter.
5 more elements
Dependencies are inferred from the claim text.