GB2378000A - Power supply apparatus and methods employing intermittent averaging of current sense signals - Google Patents
Power supply apparatus and methods employing intermittent averaging of current sense signals Download PDFInfo
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- GB2378000A GB2378000A GB0022554A GB0022554A GB2378000A GB 2378000 A GB2378000 A GB 2378000A GB 0022554 A GB0022554 A GB 0022554A GB 0022554 A GB0022554 A GB 0022554A GB 2378000 A GB2378000 A GB 2378000A
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- current
- secondary winding
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- circuit
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- 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
- H02M3/00—Conversion of DC power input into DC power output
- H02M3/22—Conversion of DC power input into DC power output with intermediate conversion into AC
- H02M3/24—Conversion of DC power input into DC power output with intermediate conversion into AC by static converters
- H02M3/28—Conversion of DC power input into DC power output with intermediate conversion into AC by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate AC
- H02M3/325—Conversion of DC power input into DC power output with intermediate conversion into AC by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate AC using devices of a triode or a transistor type requiring continuous application of a control signal
- H02M3/335—Conversion of DC power input into DC power output with intermediate conversion into AC by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate AC using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only
- H02M3/33507—Conversion of DC power input into DC power output with intermediate conversion into AC by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate AC using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of the output voltage or current, e.g. flyback converters
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- 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
- H02M1/00—Details of apparatus for conversion
- H02M1/0003—Details of control, feedback or regulation circuits
- H02M1/0009—Devices or circuits for detecting current in a converter
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- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Dc-Dc Converters (AREA)
Abstract
An apparatus is provided for determining current delivered by a power converter (10) that transfers current from a secondary winding (12b) of a transformer (12). The current determining apparatus includes a current sensor (110), coupled to the secondary winding that generates a current sense signal representing current through the secondary winding of the transformer. The apparatus further includes an intermittent averaging circuit (120), operatively associated with the current sensor that intermittently averages the current sense signal. For example, the intermittent averaging circuit may produce an average current indicating signal from the current sense signal responsive to a state of an output circuit (13) of the converter, such as a voltage across a flywheel diode in the output circuit. The current sensor may be a transformer (210, Fig 2) or a resistor (510, Fig 5).
Description
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POWER SUPPLY APPARATUS AND METHODS EMPLOYING
INTERMITTENT AVERAGING OF CURRENT SENSE SIGNALS
BACKGROUND OF THE INVENTION
The present invention relates to power supply apparatus and methods, and more particularly, to apparatus and methods for sensing current.
Power converters, such as DC-DC power converters, are used in a variety of applications, including power supplies for electronic devices such as computers and uninterruptible power supplies (UPSs) for computer and telecommunications networks. Typically, power converters are used in such applications to generate various voltages needed to operate components and to provide voltage regulation, current limiting and other power control functions. A variety of circuit topologies may be used in power converters, with the choice of circuit topology typically being based on the performance, size, weight, cost and other parameters desired for the particular application.
In many power converter applications, it is desirable to determine output current delivered by the power converter so that control functions, such as output current limiting, can be achieved. This may be problematic in switchmode power converters, such as forward converters or flyback converters, which intermittently or discontinuously transfer current. Approaches for determining average current delivered by such converters have been proposed. For example, United States Patent No. 5,457, 620 to Dromgoole describes a current estimating technique for a switchmode power supply in which switch current of a primary-side power switch of the switchmode power supply is connected to a low pass filter network during a time interval when current is flowing through the power switch, and average output current is inferred from this filtered current based on assumptions regarding circuit characteristics. Similarly, other conventional switchmode power converters may determine a peak current in a component coupled in series with the output (load) of the converter and infer an average output current from this determined peak current based on assumptions regarding circuit characteristics.
Such techniques may have disadvantages, however. In particular, techniques that rely on inferences regarding circuit parameters may suffer from inaccuracy due to
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variation and drift in these circuit parameters and/or failure to account for other circuit parameters, such as transformer leakage inductance.
SUMMARY OF THE INVENTION
According to one aspect of the present invention, an apparatus for determining current delivered by a power converter that transfers current from a secondary winding of a transformer comprises a current sensor, such as a current transformer or current sense resistor, that is coupled to the secondary winding and that generates a current sense signal representing current through the secondary winding, and an intermittent averaging circuit, operatively associated with the current sensor, that intermittently averages the current sense signal.
The intermittent averaging circuit may average the current sense signal when current in the secondary winding of the transformer meets a predetermined criterion.
The intermittent averaging circuit may produce an average current indicating signal from the current sense signal responsive to a control signal, generated by an output circuit of the converter that indicates the state of the current in the secondary winding of the transformer. For example, the output circuit may include a flywheel diode, and the control signal may comprise a voltage across the flywheel diode.
The current sensor may comprise a current transformer coupled to the secondary winding of the transformer. The intermittent averaging circuit may comprise a capacitor and a controllable current source, coupled to the current transformer, that charges the capacitor responsive to a control signal. For example, the intermittent averaging circuit may include a load circuit, coupled to the current transformer, and a switching circuit, e. g., a transistor that couples the load circuit to the capacitor responsive to a control signal, such as a gate drive signal generated from a flywheel diode voltage.
The invention provides also a power supply apparatus comprising a power converter including a transformer having primary and secondary windings, an input circuit that receives power from a power source and transfers power to the primary winding, and an output circuit that transfers current from the secondary winding to a load; a current sensor, coupled to the secondary winding, that generates a current sense signal representing a current through the secondary winding; and an
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intermittent averaging circuit, operatively associated with the current sensor, that intermittently averages the current sense signal.
According to another aspect of the present invention a method of determining current delivered by a power converter that transfers current from a secondary winding of a transformer comprises of generating a current sense signal representing a current in the secondary winding of the transformer, and intermittently averaging the current sense signal to determine current delivered by the power converter.
The current sense signal may be averaged when current in the secondary winding of the transformer meets a predetermined criterion. For example, the current sense signal may be intermittently averaged responsive to a state of an output circuit of the converter, e. g., responsive to a state of a component such as a flywheel diode.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic diagram illustrating a power converter and average current determining apparatus according to embodiments of the invention.
FIG. 2 is a schematic diagram illustrating a power converter and average current determining apparatus according to other embodiments of the invention.
FIG. 3 is a schematic diagram illustrating a forward converter and average current determining apparatus according to embodiments of the invention.
FIG. 4 is a waveform diagram graphically illustrating exemplary operations of the forward converter and average current determining apparatus of FIG. 3.
FIGs. 5-6 are schematic diagrams illustrating power converters and average current determining apparatus according to still other embodiments of the invention.
DETAILED DESCRIPTION
The present invention now will be described more fully hereinafter with reference to the accompanying drawings, in which preferred embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.
In the drawings, like numbers refer to like elements.
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In embodiments of the invention described herein, a current delivered by a power converter, such as a forward converter, flyback converter or other type of switchmode converter, is determined using an intermittent averaging technique. As used herein,"intermittent averaging"includes techniques whereby a signal, such as a current sense signal generated by a device such as a current transformer, sense resistor or other current sensor, is averaged during intermittently occurring intervals, for example, intermittent intervals during which current is being delivered to a load from the secondary winding of a power converter transformer. It will be appreciated that "averaging,"as used herein, may include a variety of techniques for determining a mean or average value over a time interval, and includes filtering and other techniques that generate signals representing such average values.
According to some embodiments of the invention, intermittent averaging comprises generating a voltage or other signal that indicates an average current.
Those skilled in the art will appreciate that such an average current indicating signal may be applied to various monitoring and/or control functions. For example, such an average current indicating signal may be used for current metering functions and/or for current limiting or other current control functions.
FIG. 1 illustrates a power supply apparatus 2 for delivering power to a load 20 from a power source 1 according to embodiments of the invention. The power source 1 may comprise a variety of power sources, including, but not limited to AC power sources such as an AC utility line, an AC generator, or the like, or a DC power source such as a battery or DC generator. The power supply apparatus 2 may be embodied in any of a number of different forms, including, but not limited to, as a freestanding or rackmount power supply unit, as a power supply subassembly integrated into a personal computer or other system or device, as a modular power supply such as a power supply card, as an uninterruptible power supply (UPS) and as an integrated circuit power supply.
The power supply apparatus 2 includes a power converter 10 that includes an input circuit 11 that applies a voltage to a primary winding 12a of a transformer 12.
An output circuit 13 is coupled to a secondary winding 12b of the transformer 12.
The output circuit 13 is operative to transfer current between the secondary winding and a load 20.
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It will be appreciated that the input circuit 11 and output circuit of FIG. 1 may take various forms. For example, in DC-DC converter applications, the input circuit 11 may comprise a switching circuit operative to selectively couple the primary winding 12a of the transformer 12 to a DC power source such that a DC voltage is intermittently applied across the primary winding 12a. It will be appreciated that such a switching circuit may take various forms, which may be dependent on the type of converter topology (e. g., forward, flyback, full-bridge, etc. ) being implemented.
Similarly, the output circuit 13 may take a variety of forms, such as passive or active switching networks, the form of which is generally dependent upon the type of converter topology being implemented. Detailed operations of such input and output circuits are known to those skilled in the art.
Still referring to FIG. 1, an apparatus 100 for determining an average current supplied to a load 20 by the converter 10 includes a current sensor 110 that generates a current sense signal 115 that represents a current in the secondary winding 12b of the transformer 12. The average current determining apparatus 100 also includes an intermittent averaging circuit 120 that intermittently averages the current sense signal 115 to generate an average current indication signal 125. The intermittent averaging performed by the intermittent averaging circuit 120 preferably is synchronized with the operation of the converter 10, such that the current sense signal 115 is averaged when current in the secondary winding 12b of the transformer 12 meets a predetermined criterion. For example, as shown, the intermittent averaging circuit 120 may operate responsive to a state of the output circuit 13 of the converter 10 that indicates the state of the current in the secondary winding 12b.
FIG. 2 illustrates an average current determining apparatus 200 for a power converter 10 according to other embodiments of the invention that implements an intermittent averaging technique. Like reference numerals indicate like elements of the power converters 10 of FIGs. 1 and 2 and, accordingly, further description of the power converter 10 of FIG. 2 will be omitted in light of the description of FIG. 1.
The average current determining apparatus 200 includes a current sensor, here shown as a current transformer (CT) 210 having a first winding 210a coupled in series with the secondary winding 12b of the transformer 12 of the power converter 10. The apparatus 200 further includes an averaging circuit 220 including a load circuit 226
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that is intermittently coupled to a capacitor C by a switch 224. The load circuit 226 includes a series combination of a resistor R and a diode D coupled to a second winding 210b of the CT 210. The switch 224 is operative to intermittently couple the capacitor C across the resistor R under control of a control circuit 222, which is, in turn, responsive to the output circuit 13 of the power converter 10. The control circuit 222 operates the switch 224 such that an average current indicating voltage Viavg is generated across the capacitor C.
FIG. 3 illustrates an average current determining apparatus 300 according to other embodiments of the invention, in which an average current indication signal Viavg is generated for a forward converter 10'. The forward converter 10'includes an input circuit 11 coupled to a primary winding 12a of a transformer 12, each of which may be configured as described above with reference to FIG. 1. The forward converter 10'also includes an output circuit 13'coupled to a secondary winding 12b of the transformer 12. The output circuit 13'includes a rectifying diode Dr, a flywheel diode Df, an output inductor Lout and an output capacitor Cout. As will be appreciated by those skilled in the art, the forward converter 10'generally operates by intermittently conducting energy from the secondary winding 12b of the transformer 12b to a load 20 via the output inductor Lout and the capacitor Cout. Such operations are known to those skilled in the art, and are described, for example, in United States Patent No. 4,415, 959 to Vinciarelli.
The average current determining apparatus 300 generates the average current indicating voltage Viavg responsive to a voltage Vf across the flywheel diode Df. The average current determining apparatus 300 includes a CT 210 having a first winding 210a coupled in series with the secondary winding 12b of the transformer 12. The apparatus 300 further includes an averaging circuit 320, including a load circuit 226 coupled to a second winding 210b of the CT 210, a switch 324 that is operative to intermittently couple the load circuit 226 to a capacitor C, and a scaling circuit 322 that drives the switch responsive to the flywheel diode voltage Vf. The load circuit 226 includes a resistor R and a diode D. The switch 324 includes a MOSFET transistor Q and diode DQ (which may be a body diode of the MOSFET). The scaling circuit 322 applies a gate drive signal to the transistor Q responsive to the flywheel diode voltage Vf.
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Preferably, the scaling circuit 322 causes the transistor Q to connect the capacitor C across the loading resistor R when the flywheel diode voltage Vf indicates that current Is through the secondary winding 12b of the transformer 12 is greater than or equal to the current flowing in the output inductor lout. Referring to FIGs. 3 and 4, after the input circuit 11 of the forward converter 10'is turned"on"at time tl, i. e., such that a voltage is applied across the primary winding 12a of the transformer, current Is in the secondary winding 12b initially ramps up due to the leakage inductance of the transformer 12. At time t2, the current Is in the secondary winding 12b of the transformer 12 exceeds the current in the output inductor Lout, causing the voltage Vf across the flywheel diode Df to rise. From time t2 to time t3, current Is in the secondary winding 12b ramps up essentially with a slope defined by the output inductance. During the interval from time t2 to time t3, the average current in the secondary winding 12b approximately equals the average current in the output inductor Lout during the same interval and, assuming continuous-mode operation, the average current in the output inductor Lout during the complete switching cycle.
If the transistor switch Q (which preferably has an"on"resistance much less that the resistance of the resistor R) is closed during in the interval from time t2 to time t3, the voltage Viavg across the capacitor C, assuming that the CT 210 is substantially ideal, is governed by the equation:
where N is the turns ratio of the CT 210, IL is the current in the output inductor Lout, and Ic is a charging current in the capacitor C. At steady state, the net charge added to the capacitor during the interval from time t2 to time t3 equals the net charge removed, such that:
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where ILavg is the average current in the output inductor Lout in the interval from time t2 to time t3. The capacitor C may be chosen such that the ripple voltage across it is small.
Potential advantages of the apparatus of FIG. 3 are apparent from the foregoing description. Constraining averaging by the averaging circuit 320 to occur during the interval from time t2 to time t3 can reduce inaccuracies that may arise due to variation in circuit characteristics such as the leakage inductance of the transformer 12 and the inductance of the output inductor Lout. In addition, because the effects of such circuit characteristics may be reduced, calibration of parameters, such as current limit thresholds, can be avoided.
In addition, the small-signal charge and discharge time constants for the averaging circuit 320 are substantially equal, which can be beneficial in average current mode control and other applications. The charge and discharge time constants are generally determined by the capacitance of the capacitor C, the resistance of the resistor R and the duty-cycle of the forward converter 10'. In particular, the (charge or discharge) time constant T for the averaging circuit may be expressed as:
where T is the period of the forward converter 10'.
The presence of the diode DQ can provide additional benefits. Under large signal conditions, such as when the output of the converter 10'is short-circuited, the time constant of the averaging circuit 320 may be reduced by action of the diode DQ.
In particular, under short circuit conditions, the output current of the forward converter 10'may become so large that the diode DQ conducts before the transistor Q is turned on, causing the capacitor C to begin charging before the transistor Q turns on. This can be beneficial under short circuit conditions, as it may allow the average current indicating voltage Viavg to quickly reflect the short circuit condition with less overshoot. If used in conjunction with a current limiting control circuit, this can allow the current limiting control circuit to more quickly limit output current under short circuit conditions.
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It will be appreciated that the invention is not limited to the configuration illustrated in FIG. 3. For example, although the circuit illustrated in FIG. 3 uses a flywheel diode voltage Vfthat is indicative of a relationship between the current Is in the secondary winding 12b and the output current delivered by the converter 10', other"state variables"of the output circuit 13'could be used for timing intermittent averaging operations.
The invention is also applicable to other types of output circuits. For example, referring to FIG. 3, the output circuit 13'may be modified to include a magnetic amplifier (saturable reactor) coupled in series between the secondary winding 12b and the rectifying diode Dr to provide control of the secondary current Is. Such an approach may be used, for example, in multi-output applications in which respective ones of a plurality of such modified output circuits are coupled to respective secondary windings that are magnetically coupled to a common primary winding.
The presence of the magnetic amplifiers in the output circuits allows the output voltages produced by the output circuits to be individually controlled, i. e. , by individually affecting the timing of the currents in the secondary windings.
Other types of output circuits, such as active output circuits including synchronous rectifiers, may also be used with the present invention. Intermittent averaging operations for such converters may be synchronized using, for example, control signals that control operation of active devices in the active output circuit.
The invention is also applicable to converters other than forward converters.
For example, the invention may be used with a flyback converter or other converter that exhibits intermittent or discontinuous current transfer. Average current determining apparatus for these types of converters may utilize, for example, other internal voltages or currents as timing references for intermittent averaging operations.
The invention may also use different current sensing techniques than illustrated in FIG. 3. Referring to FIG. 5, according to yet other embodiments of the invention, a power converter 10 includes an input circuit 11, a transformer 12 and an output circuit 13 as described with reference to FIG. 1. An average current determining apparatus 500 includes a current sensor 510 and an averaging circuit 520. The current sensor 510 comprises a current sense resistor Rs coupled in series with the
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secondary winding 12b of the transformer 12. The averaging circuit 520 includes a switch 524 that is operative to intermittently couple a capacitor C across the resistor Rs responsive to a control signal generated by a control circuit 522 to thereby generate an average current indicating voltage Viavg across the capacitor C. The control circuit 522 generates the control signal responsive to the output circuit 13 of the power converter 10, e. g. , responsive to a flywheel diode voltage or similar parameter that is indicative of a relationship between current in the secondary winding 12b and current delivered to the load 20.
FIG. 6 illustrates an average current determining apparatus 600 for a power converter 10 according to still other embodiments of the invention. The power converter 10 includes an input circuit 11, a transformer 12 and an output circuit 13, which may be as described above with reference to FIG. 1. The average current determining apparatus 600 includes a CT 210 having a first winding 21 Oa coupled in series with the secondary winding 12b of the transformer 12. The apparatus 600 further includes an averaging circuit 620 comprising a diode D and a controllable current source 622, coupled to a second winding 210b of the CT 210. The controllable current source 622 is responsive to the output circuit 13 of the power converter 10 to charge and discharge a capacitor C to thereby generate an average current indicating voltage Viavg across the capacitor C. It will be appreciated that the controllable current source 622 may be implemented using any of a number of different circuits. For example, in applications in which the apparatus 600 is implemented in an integrated circuit (IC), the controllable current source 622 may be an active microelectronic circuit. Such current source circuits are known to those skilled in the art.
In the drawings and specification, there have been disclosed typical preferred embodiments of the invention and, although specific terms are employed, they are used in a generic and descriptive sense only and not for purposes of limitation, the scope of the invention being set forth in the following claims.
Claims (33)
1. An apparatus for determining current delivered by a power converter that transfers current from a secondary winding of a transformer, the apparatus comprising : a current sensor, coupled to the secondary winding, that generates a current sense signal representing a current through the secondary winding; and an intermittent averaging circuit, operatively associated with the current sensor, that intermittently averages the current sense signal.
2. An apparatus according to Claim 1, wherein the intermittent averaging circuit averages the current sense signal when the current in the secondary winding of the transformer meets a predetermined criterion.
3. An apparatus according to Claim 1 or 2, wherein the intermittent averaging circuit averages the current sense signal responsive to a control signal that is indicative of a state of the current in the secondary winding.
4. An apparatus according to Claim 3, wherein the power converter comprises an output circuit that selectively transfers current from the secondary winding, and wherein the output circuit generates the control signal.
5. An apparatus according to Claim 4, wherein the output circuit comprises a flywheel diode, and wherein the control signal comprises a voltage across the flywheel diode.
6. An apparatus according to any one of claims 1,2, 3,4 or 5, wherein the intermittent averaging circuit charges and discharges a capacitor responsive to the current sense signal.
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7. An apparatus according to Claim 6, wherein the intermittent averaging circuit charges and discharges the capacitor with respective substantially equal charge and discharge time constants.
8. An apparatus according to any one of claims 1, 2,3, 4,5, 6 or 7, wherein the intermittent averaging circuit produces an average current indicating signal from the current sense signal.
9. An apparatus according to any one of claims 1, 2,6, 7 or 8, wherein the power converter comprises an output circuit that intermittently transfers current from the secondary winding of the transformer, wherein the intermittent averaging circuit intermittently averages the current sense signal responsive to a state of the output circuit.
10. An apparatus according to any one of claims 1, 2,3, 4,5, 6,7, 8 or 9, wherein the current sensor comprises a current transformer coupled to the secondary winding of the transformer.
11. An apparatus according to any one of claims 1,2, 3,4, 5,6, 7,8 or 9, wherein the current sensor comprises a resistor coupled in series with the secondary winding of the transformer.
12. An apparatus according to Claim 3: wherein the current sensor comprises a current transformer coupled to the secondary winding of the transformer ; and wherein the intermittent averaging circuit comprises : a capacitor; and a controllable current source, coupled to the current transformer, that charges the capacitor responsive to the control signal.
13. An apparatus according to Claim 3:
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wherein the current sensor comprises a current transformer coupled to the secondary winding of the transformer ; and wherein the intermittent averaging circuit comprises: a capacitor; a load circuit coupled to the current transformer; and a switching circuit that couples the load circuit to the capacitor responsive to the control signal.
14. An apparatus according to Claim 3: wherein the current sensor comprises a resistor coupled in series with the secondary winding of the transformer ; and wherein the intermittent averaging circuit comprises: a capacitor; and a switching circuit that couples the resistor across the capacitor responsive to the control signal.
15. An apparatus according to Claim 1: wherein the power converter comprises a forward converter that includes a flywheel diode; wherein the current sensor comprises a current transformer coupled to the secondary winding of the transformer; and wherein the intermittent averaging circuit comprises: a capacitor; a load circuit coupled to the current transformer ; and a switching circuit that couples the load circuit to the capacitor responsive to a voltage across the flywheel diode.
16. An apparatus according to any one of claims 13,14 or 15, wherein the switching circuit comprises a transistor.
17. An apparatus according to Claim 16, wherein the transistor is operative to connect the capacitor across the resistor responsive to a transistor drive signal
<Desc/Clms Page number 14>
applied to the transistor, and wherein the switching circuit further comprises a scaling circuit that generates the transistor drive signal responsive to the voltage across the flywheel diode.
18. An apparatus according to Claim 16, wherein the switching circuit further comprises a diode coupled across the transistor.
19. An apparatus according to Claim 1, wherein the power converter, the transformer, the current sensor and the intermittent averaging circuit are included in a power supply apparatus.
20. A power supply apparatus, comprising: a power converter including a transformer having primary and secondary windings, an input circuit that receives power from a power source and transfers power to the primary winding, and an output circuit that transfers current from the secondary winding to a load; a current sensor, coupled to the secondary winding, that generates a current sense signal representing a current through the secondary winding; and an intermittent averaging circuit, operatively associated with the current sensor, that intermittently averages the current sense signal.
21. An apparatus according to Claim 20, wherein the intermittent averaging circuit averages the current sense signal when the current in the secondary winding of the transformer meets a predetermined criterion.
22. An apparatus according to Claim 20 or 21, wherein the intermittent averaging circuit averages the current sense signal responsive to a control signal that is indicative of a state of the current in the secondary winding
23. An apparatus according to Claim 22, wherein the output circuit generates the control signal
<Desc/Clms Page number 15>
24. An apparatus according to Claim I or Claim 20 and substantially as herein before described with reference to the accompanying drawings.
25. A method of determining current delivered by a power converter that transfers current from a secondary winding of a transformer, the method comprising: generating a current sense signal representing a current in the secondary winding of the transformer ; and intermittently averaging the current sense signal to determine current delivered by the power converter.
26. A method according to Claim 25, wherein the step of intermittently averaging comprises averaging the current sense signal when the current in the secondary winding of the transformer meets a predetermined criterion.
27. A method according to Claim 25 or 26, wherein the step of intermittently averaging comprises intermittently averaging the current sense signal responsive to a control signal that is indicative of a state of the current in the secondary winding.
28. A method according to Claim 27, wherein the power converter comprises an output circuit that selectively conducts current from the secondary winding to a load, and wherein the method further comprises generating the control signal responsive to the output circuit.
29. A method according to Claim 28, wherein the output circuit comprises a flywheel diode, and wherein the step of generating the control signal comprises generating a voltage across the flywheel diode.
30. A method according to any one of claims 25,26, 27,28 or 29 wherein the step of intermittently averaging comprises intermittently averaging the current sense signal to generate an average current indicating signal.
<Desc/Clms Page number 16>
31. A method according to any one of claims 25,26, 27,28, 29 or 30 wherein the step of intermittently averaging comprises intermittently charging and discharging a capacitor responsive to the current sense signal.
32. A method according to Claim 30, further comprising applying the average current indicating signal in a monitoring and/or control function.
33. Method according to Claim 25 and substantially as herein before described.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB0022554A GB2378000B (en) | 2000-09-14 | 2000-09-14 | Power supply apparatus and methods for sensing current |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB0022554A GB2378000B (en) | 2000-09-14 | 2000-09-14 | Power supply apparatus and methods for sensing current |
Publications (3)
| Publication Number | Publication Date |
|---|---|
| GB0022554D0 GB0022554D0 (en) | 2000-11-01 |
| GB2378000A true GB2378000A (en) | 2003-01-29 |
| GB2378000B GB2378000B (en) | 2005-01-19 |
Family
ID=9899449
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB0022554A Expired - Lifetime GB2378000B (en) | 2000-09-14 | 2000-09-14 | Power supply apparatus and methods for sensing current |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2378000B (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20170201180A1 (en) * | 2010-03-26 | 2017-07-13 | Russell Jacques | Controller for controlling a power converter |
| ITUB20169969A1 (en) * | 2016-01-14 | 2017-07-14 | Osram Gmbh | DEVICE FOR DETECTING CURRENTS AND ITS PROCEDURE |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5457620A (en) * | 1993-07-30 | 1995-10-10 | At&T Ipm Corp. | Current estimating circuit for switch mode power supply |
-
2000
- 2000-09-14 GB GB0022554A patent/GB2378000B/en not_active Expired - Lifetime
Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5457620A (en) * | 1993-07-30 | 1995-10-10 | At&T Ipm Corp. | Current estimating circuit for switch mode power supply |
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20170201180A1 (en) * | 2010-03-26 | 2017-07-13 | Russell Jacques | Controller for controlling a power converter |
| US10396669B2 (en) * | 2010-03-26 | 2019-08-27 | Russell Jacques | Power converter measuring the average rectified primary current |
| ITUB20169969A1 (en) * | 2016-01-14 | 2017-07-14 | Osram Gmbh | DEVICE FOR DETECTING CURRENTS AND ITS PROCEDURE |
| WO2017122129A1 (en) | 2016-01-14 | 2017-07-20 | Osram Gmbh | A current sensing circuit and corresponding method |
| US10613121B2 (en) | 2016-01-14 | 2020-04-07 | Osram Gmbh | Current sensing circuit and corresponding method |
Also Published As
| Publication number | Publication date |
|---|---|
| GB0022554D0 (en) | 2000-11-01 |
| GB2378000B (en) | 2005-01-19 |
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| PE20 | Patent expired after termination of 20 years |
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