High efficiency linear regulator
First Claim
1. A voltage regulator comprising:
- a switching voltage regulator comprising a power switch electrically coupled to a first terminal of an inductor, the switch being controlled to turn on and off based on a feedback signal to the switching voltage regulator; and
a linear regulator, having an input electrically coupled to a second terminal of the inductor, for smoothing out ripples in the voltage applied to the input and outputting a regulated voltage, the combined switching regulator and linear regulator for providing a maximum load current, the inductor having an inductance value such that the inductor at least partially saturates at load currents below the maximum load current.
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Abstract
A single chip hybrid regulator is disclosed having a first stage being a switching regulator and a second stage being a linear regulator. The switching regulator uses a filter circuit including an inductor and a capacitor. To make the hybrid regulator very small, the inductor value is selected so that the inductor saturates at a current level well below the maximum load current for the regulator. At low load currents, the small inductor does not saturate, and the regulated voltage applied to the input of the linear regulator presents only a small differential voltage across the series transistor of the linear regulator, resulting in very little power being wasted by the series transistor. At higher currents, the small inductor begins to saturate or fully saturates; however, the increased ripple is smoothed by the linear regulator. For applications, such as cell phones, where the regulator operates at low currents for the vast majority of the time, the overall efficiency of the regulator is extremely high and the regulated voltage is very smooth. As the inductor becomes highly saturated, or if the switching regulator cannot supply sufficient current, the switching regulator may be bypassed by the closing of a switch to continuously couple the power supply input voltage to the input of the linear regulator.
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Citations
45 Claims
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1. A voltage regulator comprising:
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a switching voltage regulator comprising a power switch electrically coupled to a first terminal of an inductor, the switch being controlled to turn on and off based on a feedback signal to the switching voltage regulator; and
a linear regulator, having an input electrically coupled to a second terminal of the inductor, for smoothing out ripples in the voltage applied to the input and outputting a regulated voltage, the combined switching regulator and linear regulator for providing a maximum load current, the inductor having an inductance value such that the inductor at least partially saturates at load currents below the maximum load current. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21)
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22. A voltage regulator comprising:
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a switching voltage regulator comprising a power switch electrically coupled to a first terminal of an inductor, the switch being controlled to turn on and off based on a feedback signal to the switching voltage regulator;
a linear regulator, having an input electrically coupled to a second terminal of the inductor, for smoothing out ripples in the voltage applied to the input and outputting a regulated voltage;
a current sensor for sensing when a current exceeds a threshold and, in response to the sensing, issuing a first signal; and
a switch, other than the power switch, for continuously coupling a power supply input voltage terminal to the input of the linear regulator in response to the first signal. - View Dependent Claims (23)
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24. A method performed by a hybrid regulator, the regulator for providing a maximum load current, comprising:
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generating a pulsed signal by a switching regulator turning on and off a power switch, the pulsed signal being applied to an inductor and a capacitor to generate a first regulated voltage at a first terminal;
controlling the conductance of a series transistor in a linear regulator, having a second terminal electrically coupled to the first terminal, so that a second regulated voltage is generated at an output terminal of the linear regulator; and
at least partially saturating the inductor prior to the hybrid regulator generating the maximum load current. - View Dependent Claims (25, 26, 27)
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28. A method performed by a hybrid regulator, the regulator for providing a maximum load current, comprising:
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generating a pulsed signal by a switching regulator turning on and off a power switch, the pulsed signal being applied to an inductor and a capacitor to generate a first regulated voltage at a first terminal;
controlling the conductance of a series transistor in a linear regulator, having a second terminal electrically coupled to the first terminal, so that a second regulated voltage is generated at an output terminal of the linear regulator;
sensing when a current exceeds a threshold and, in response to the sensing, issuing a first signal; and
controlling a switch, other than the power switch, for continuously coupling a power supply input voltage terminal to the input of the linear regulator in response to the first signal. - View Dependent Claims (29)
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30. A hybrid voltage regulator comprising:
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a switching voltage regulator comprising a power switch electrically coupled to a first terminal of an inductor, the switch being controlled to turn on and off based on a feedback signal to the switching voltage regulator;
a linear regulator, having an input electrically coupled to a second terminal of the inductor, for smoothing out ripples in the voltage applied to the input and outputting a regulated voltage;
a current sense amplifier connected to detect the output current of the linear regulator; and
a current limit comparator receiving a signal from the current sense amplifier and generating a current limit signal when the current output by the linear regulator exceeds a threshold, the current limit comparator being connected to suspend operation of the switching voltage regulator when the current limit signal is generated.
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31. A transformerless DC-DC step down voltage regulator comprising:
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a switching voltage regulator comprising a power switch having a first terminal connected to a power supply, the power switch being controlled to turn on and off based on a feedback signal;
a non-transformer inductor, a first terminal of the inductor being coupled to a second terminal of the power switch to receive a pulse of voltage from the power switch when the power switch is turned on and, in response, generate a ramping current through the inductor, the switching voltage regulator for providing a maximum load current at a regulated output voltage, the inductor having an inductance value such that the inductor at least partially saturates at load currents below the maximum load current under normal operating conditions as the inductor conducts the ramping current;
a rectifying device having a first terminal connected to a node between the inductor and the power switch and a second terminal connected to a fixed reference potential, the rectifying device conducting only when a voltage at the first terminal is less than the reference potential; and
a filter capacitor connected to a second terminal of the inductor for filtering the ramping current through the inductor and providing the regulated output voltage. - View Dependent Claims (32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43)
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44. A method performed by a DC-DC step down transformerless switching voltage regulator, the regulator for providing a maximum load current at a regulated voltage, comprising:
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generating a pulsed signal by the switching voltage regulator turning on and off a power switch, a first terminal of the power switch being connected to a power supply;
applying the pulsed signal to a non-transformer inductor, which conducts a ramping current through the inductor, the inductor having an inductance value such that the inductor at least partially saturates at load currents below the maximum load current under normal operating conditions as the inductor conducts the ramping current;
at least partially saturating the inductor prior to the regulator reaching the maximum load current;
rectifying a signal at a node between the inductor and the power switch by a rectifying device having a first terminal connected to the node between the inductor and the power switch and a second terminal connected to a fixed reference potential, the rectifying device conducting only when a voltage at the first terminal is less than the reference potential; and
filtering the ramping current by a filter capacitor to generate the regulated voltage. - View Dependent Claims (45)
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Specification