POWER REGULATOR HAVING CURRENT AND VOLTAGE MODES

• US 20170005574A1
• Filed: 06/30/2015
• Published: 01/05/2017
• Est. Priority Date: 06/30/2015
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Inventors: Wyland, David C.
• Granted Patent: US 9,853,545 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: H02M 3/156 with automatic control of output voltage or current, e.g. switching regulators
• CPC Class Codes: H02M 3/158 including plural semiconductor devices as final control devices for a single load

Abstract

A power supply is configured to automatically and rapidly switch from a voltage maintaining mode to a current limiting mode (at times that are unpredictable from a point of view of the power supply) when supplying replenishing current to a combination of a power insulated gate switching device and power capacitor that drive relatively large surges of pulsed power through a load such as a laser emitter of a Time of Flight (TOF) determining system. The current limiting mode is automatically activated by the start of each train of large surges of pulsed power and it replenishes charge to the power capacitor on a time averaged basis such that the capacitor develops a temperature appropriate voltage for providing the time averaged current to the power insulated gate switching device and its load and causing the load (e.g., laser) to output a desired amount of output power. The current limiting mode automatically stops when the time averaged current is detected to drop below a threshold and then the voltage maintaining mode automatically begins. The voltage maintaining mode maintains a stored voltage across the capacitor slightly greater than a maximum voltage needed to drive the load (e.g., laser emitter) to the desired magnitude of output power (e.g., output luminance).

Claims

1. A method of supplying power to a load that episodically becomes connected to receive current from a power supply, the method comprising:

automatically detecting if the load is drawing on a time averaged basis, more than a predetermined first amount of average current, and if not, responsively causing a charge storage device to be charged to a predetermined first voltage using a voltage controlled mode of a multi-mode regulated power supply, where the load becomes connected to the charge storage device at substantially a same time that the load becomes episodically connected to receive current from the multi-mode regulated power supply;

in response to detecting that the load is on the time averaged basis drawing more than the predetermined first amount of average current, automatically switching the multi-mode regulated power supply to a current regulating mode to thereby limit the amount of average current received by the load to a second amount of average current greater than the first amount of average current; and

in response to detecting that the load is no longer on the time averaged basis drawing more than the predetermined first amount of average current, automatically switching the multi-mode regulated power supply to the voltage controlled mode to thereby cause the charge storage device to again be charged to the predetermined first voltage.

2. The method of claim 1 and further comprising:

automatically switching the multi-mode regulated power supply back to a current regulating mode upon again detecting that the load is on the time averaged basis again drawing more than the predetermined first amount of average current.

3. The method of claim 1 wherein:

the charge storage device includes a capacitor; and

the load includes a temperature and voltage sensitive device whose output behavior is more so determined by current levels that it receives rather than by its temperature and by corresponding load voltages that develop across the temperature and voltage sensitive device.

4. The method of claim 3 wherein:

the temperature and voltage sensitive device includes a semi-conductive light emitter whose output luminance is more so determined by current levels that it receives rather than by its temperature and by corresponding load voltages that develop across the semi-conductive light emitter.

5. The method of claim 4 wherein:

the semi-conductive light emitter is one that needs to receive an episodic surge of current of 0.5 Ampere or more to produce an application adequate output luminance.

6. The method of claim 1 wherein:

the load is connected in series with a semi-conductive switching device and the load episodically becomes connected to receive current from the multi-mode regulated power supply due to episodic closing and opening of the semi-conductive switching device, the method further comprising;

causing the semi-conductive switching device to close and open, the closing of the semi-conductive switching device occurring in 10 nanoseconds (10 ns) or less.

7. The method of claim 1 wherein the causing of the charge storage device to be charged to the predetermined first voltage while using the voltage controlled mode comprises:

generating a feedback voltage that is predetermined amount less than an output voltage produced by the multi-mode regulated power supply;

applying the feedback voltage to a feedback resistor;

comparing the feedback voltage with a reference voltage; and

in response to detecting that feedback voltage is equal to or greater than the reference voltage, deactivating a voltage booster that generates the output voltage produced by the multi-mode regulated power supply.

8. The method of claim 7 wherein the generating of the feedback voltage comprises:

passing a feedback current through the feedback resistor; and

passing the feedback current through a voltage sensitive device having a threshold voltage, where the voltage sensitive device switches from a relatively low resistance mode to a substantially higher resistance mode at substantially a same time that voltage across the voltage sensitive device drops below the threshold voltage;

wherein during the voltage regulating mode, the voltage sensitive device operates just above its threshold voltage; and

wherein the load is coupled so as to divert current away from the voltage sensitive device at substantially a same time that the load draws on the time averaged basis, more than the predetermined first amount of average current, where the diverting away of the current causes the voltage sensitive device to operate below its threshold voltage and thus in its substantially higher resistance mode.

9. The method of claim 8 wherein the switching of the multi-mode regulated power supply to the current regulating mode comprises:

producing a sampling current that is representative of a magnitude of the on the time averaged basis drawn current of the load; and

passing the sampling current through the feedback resistor.

10. The method of claim 1 and further comprising:

causing the load to become episodically connected to receive current from the multi-mode regulated power supply by commanding a firing of a rapid train of pulses each have a pulse duration of 50 nanoseconds or less.

11. A power supply configured to supply power to a load that episodically becomes connected to receive current from the power supply, the power supply having a voltage regulating mode and a current regulating mode and comprising:

a voltage maintaining portion that is configured to be active while the voltage regulating mode is in effect, the voltage maintaining portion including a subtractive circuit that subtracts a predetermined first voltage magnitude from a voltage present at an output sampling node to thereby produce a first feedback voltage which is applied to a feedback resistor;

a comparator coupled to the feedback resistor so as to receive the first feedback voltage and configured to compare the first feedback voltage with a predetermined first reference voltage; and

a booster configured to pump charge to the output sampling node in response to the comparator indicating that the first feedback voltage is less than the first reference voltage; and

a current limiting portion that is configured to automatically become active at substantially a same time that an over-time averaged current drawn to the load is detected to exceed a predetermined first current magnitude, the drawn averaged current being one drawn to the load at substantially a same time that the load is episodically connected to receive current from the power supply;

wherein the voltage maintaining portion is configured to automatically stop producing the first feedback voltage in response to detection that the drawn averaged current exceeds the first current magnitude; and

wherein the current limiting portion is configured to supply a sampling current to the feedback resistor at substantially a same time that the current limiting portion becomes active, the sampling current being representative of a magnitude of the drawn averaged current and causing a second feedback voltage to develop at the feedback resistor such that the booster stops pumping charge to the output sampling node in response to the comparator indicating that the second feedback voltage is equal to or greater than the first reference voltage.

12. The power supply of claim 11 wherein:

the voltage maintaining portion is configured to automatically again produce the first feedback voltage in response to detection that the drawn averaged current ceases to exceed the predetermined first current magnitude.

13. The power supply of claim 11 wherein:

the load is connected to a charge storage device so as to be able to receive pulses of current from the charge storage device at substantially a same time that the load episodically becomes connected to receive current from the power supply;

the charge storage device is connected to the power supply so as to store a maintained output voltage developed by the power supply while the voltage regulating mode is in effect.

14. The power supply of claim 13 wherein:

the charge storage device includes a capacitor;

the load is configured to draw pulses of current each of 0.5 Ampere or more from the capacitor; and

the booster that pumps charge to the output sampling node has sufficient charge producing capability to replenish over a duration of two pulses the drawn amount of charge that the load has drawn as pulses of current from the capacitor.

15. The power supply of claim 11 wherein:

the subtractive circuit comprises a Zener diode in series with a semi-conductive diode, the semi-conductive diode having a predetermined threshold voltage;

the subtractive circuit is configured to bias the semi-conductive diode just above its predetermined threshold voltage while the voltage regulating mode is in effect; and

the current limiting portion is connected so as to deprive the semi-conductive diode of at least some of its biasing current in response to detection that the drawn averaged current exceeds the first current magnitude, thus shifting the semi-conductive diode below its predetermined threshold voltage and causing the semi-conductive diode to decrease in conductivity.

16. The power supply of claim 11 wherein:

the current limiting portion includes an operational amplifier having a first input terminal coupled to a current sensor through which the drawn averaged current passes and a second input terminal coupled to a current diverting resistor through which the sampling current flows.

17. The power supply of claim 16 wherein:

the current limiting portion further includes a bipolar transistor interposed in series between the current diverting resistor and the comparator, a base terminal of the bipolar transistor being coupled to an output terminal of the operational amplifier.

18. The power supply of claim 11 and further comprising:

a digitally controllable current supply operatively coupled to the feedback resistor so as to perform at least one of, injecting a digitally defined current into the feedback resistor, drawing off a digitally defined current from a node of the feedback resistor and in response to a supplied digital command, not injecting current into the feedback resistor or drawing current out from the node of the feedback resistor.

20. The TOF determining system of claim 18 wherein:

the power supply is configured to alternatingly and between its supplying of replenishing current to the first said capacitor, to supply replenishing current to one or more additional capacitors, each having a corresponding additional semi-conductive light emitter connected to it to draw corresponding high powered surges of current from the corresponding capacitor.

19. A time of flight (TOF) determining system comprising:

a semi-conductive light emitter;

a capacitor connected to the light emitter such that the light emitter can draw high powered surges of current from the capacitor, the surges having a magnitude of 0.5 Amperes or more; and

a power supply configured to supply a charge replenishing current to the capacitor after the light emitter has drawn the high powered surges of current from the capacitor, the power supply having a voltage regulating mode and a current regulating mode and including;

a voltage maintaining portion that is configured to be active while the voltage regulating mode is in effect, the voltage maintaining portion including a subtractive circuit that subtracts a predetermined first voltage magnitude from a voltage present at an output sampling node to thereby produce a first feedback voltage which is applied to a feedback resistor;

a comparator coupled to the feedback resistor so as to receive the first feedback voltage and configured to compare the first feedback voltage with a predetermined first reference voltage; and

a booster configured to pump charge to the output sampling node in response to the comparator indicating that the first feedback voltage is less than the first reference voltage; and

a current limiting portion that is configured to automatically become active in response to detection that an over-time averaged current drawn to the load is detected to exceed a predetermined first current magnitude, the drawn averaged current being one drawn to the load when the load is episodically connected to receive current from the power supply;

wherein the voltage maintaining portion is configured to automatically stop producing the first feedback voltage in response to detection that the drawn averaged current exceeds the first current magnitude; and

wherein the current limiting portion is configured to supply a sampling current to the feedback resistor at substantially a same time that the current limiting portion becomes active, the sampling current being representative of a magnitude of the drawn averaged current and causing a second feedback voltage to develop at the feedback resistor such that the booster stops pumping charge to the output sampling node in response to the comparator indicating that the second feedback voltage is equal to or greater than the first reference voltage.