|Publication number||USRE40072 E1|
|Application number||US 11/062,350|
|Publication date||Feb 19, 2008|
|Filing date||Feb 18, 2005|
|Priority date||Apr 13, 2001|
|Also published as||EP1249924A2, EP1249924A3, US6522108, US20020149348|
|Publication number||062350, 11062350, US RE40072 E1, US RE40072E1, US-E1-RE40072, USRE40072 E1, USRE40072E1|
|Inventors||Jay Prager, Patrizio Vinciarelli|
|Original Assignee||Vlt Corporation|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (27), Non-Patent Citations (5), Referenced by (12), Classifications (17), Legal Events (2)|
|External Links: USPTO, USPTO Assignment, Espacenet|
This invention relates to reducing energy loss and noise in power converters.
As shown in
During another, shunt period 14 of each cycle, while switch 22 is closed, the voltage at the left side of the diode (node 23) is grounded, and no current flows in the diode. Instead, a shunt current (Is) is conducted from the source 26 into the inductor 21 via the closed switch 22. In a circuit with ideal components, the current in the inductor would begin at zero and rise linearly to time ts1off, when switch 22 is turned off to start another power delivery period 12.
In a non-ideal converter, in which there are parasitic circuit capacitances and the diode is non-ideal (e.g., for a bipolar diode there will be a reverse recovery period and for a Schottky diode there will be diode capacitance), an oscillatory ringing will occur after tcross.
In one example, waveforms for a non-ideal converter of the kind shown in
Because of the reverse flow of current in the diode during the diode recovery period, energy has been stored in the inductor as of the off time tdoff (the “recovery energy”). In addition, parasitic circuit capacitances (e.g., the parasitic capacitances of the switch 22, the diode 24, and the inductor 24, not shown) also store energy as of time tdoff (e.g., the parasitic capacitance of switch 22 will be charged to a voltage approximately equal to Vout).
After time tdoff, energy is exchanged between the inductor and parasitic capacitances in the circuit. As shown in
In general, in one aspect, the invention features apparatus that includes (a) switching power conversion circuitry including an inductive element connected to deliver energy via a unidirectional conducting device from an input source to a load during a succession of power conversion cycles, and circuit capacitance that can resonate with the inductive element during a portion of the power conversion cycles to cause a parasitic oscillation, and (b) clamp circuitry connected to trap energy in the inductive element and reduce the parasitic oscillation.
Implementations of the invention may include one or more of the following. The power conversion circuitry comprises a unipolar, non-isolated boost converter comprising a shunt switch. The power conversion circuitry is operated in a discontinuous mode. The clamp circuitry is configured to trap the energy in the inductor in a manner that is essentially non-dissipative. The clamp circuitry comprises elements configured to trap the energy by short-circuiting the inductor during a controlled time period. The inductive element comprises a choke or a transformer. The elements comprise a second switch connected effectively in parallel with the inductor. The second switch is connected directly in parallel with the inductor or is inductively coupled in parallel with the inductor. The second switch comprises a field effect transistor in series with a diode.
The power conversion circuitry comprises a unipolar, non-isolated boost converter comprising a shunt switch and a switch controller, the switch controller being configured to control the timing of a power delivery period during which the shunt switch is open and a shunt period during which the shunt switch is closed.
The shunt switch is controlled to cause the power conversion to occur in a discontinuous mode. The second switch is opened for a period before the shunt switch is closed in order to discharge parasitic capacitances in the apparatus. The power conversion circuitry comprises at least one of a unipolar, isolated, single-ended forward converter, a buck converter, a flyback converter, a zero-current switching converter, a PWM converter, a bipolar, non-isolated, boost converter, a bipolar, non-isolated boost converter, a bipolar, non-isolated buck converter, a bipolar, isolated boost converter, or a bipolar, isolated buck converter.
In general, in another aspect, the invention features, a method that reduces parasitic oscillations by trapping energy in the inductive element during a portion of the power conversion cycles.
Implementations of the invention include releasing the energy from the inductor essentially non-dissipatively. The energy is trapped by short-circuiting the inductive element during a controlled time period. The short-circuiting is done by a second switch connected effectively in parallel with the inductive element. The second switch is opened for a portion of the power conversion cycle in order to discharge parasitic capacitances. The invention reduces undesirable ringing noise generated in a power converted by oscillatory transfer of energy between inductive and capacitive elements in the converter and recycles this energy to reduce or eliminate the dissipative loss of energy associated with turn-on of a switching element in the converter.
Other advantages and features will become apparent from the following description and from the claims.
With reference to
After tdoff, with the switch 22 open and the diode non-conductive, energy stored in the resonant circuit formed by the circuit parasitic capacitances and inductor L1 causes oscillatory ringing in Iin and Vs. This oscillation (referred to herein as “parasitic oscillation” or simply “noise”) is unrelated to the power conversion process, and may require that noise filtering components be added to the converter (not shown). In addition, closure of the switch 22 after tdoff will result in a wasteful loss of some or all of this energy (“switching loss”).
By providing mechanisms for clamping the circuit voltages, the noise can be reduced or eliminated, and the stored energy can be trapped in an inductor and then released essentially losslessly back to the circuit. Generally, the capturing and later release of the energy is achieved by effectively shorting and then un-shorting the two ends of an inductor at controlled times.
As shown in
The recovery switch 30 is turned on and off in the following cycle. The switch may be turned on any time during the power delivery period 12 when the voltage across the inductor, VB (FIG. 3), is negative, because this will result in diode 32 being reverse biased. During the reverse recovery period, the diode 32 prevents the current that is flowing backward from the diode 38 from flowing in recovery switch 30. Instead, the reverse recovery energy is stored in the inductor.
After the diode snaps off, the energy stored in circuit parasitic capacitances will be exchanged with the inductor and the voltage, Vs, across shunt switch 22 will ring down. When the input voltage Vs rings down to the input voltage, Vin, the voltage VB will equal zero, the recovery diode 32 will conduct and the recovery switch 30 and the diode 32 will short the ends of the inductor 34. In that state, the inductor 34 cannot exchange energy with any other circuit components. Therefore, the energy is “trapped” in the inductor and ringing in the main circuit is essentially eliminated.
Later, prior to the shunt switch being closed to start the shunt period, the recovery switch is opened. Because the current trapped in the inductor flows in the direction back toward the input source, opening the recovery switch 30 will result in an essentially lossless charging and discharging of parasitic circuit capacitances and a reduction in the voltage, Vs, across the shunt switch. By providing for a reduction in shunt switch voltage, Vs, the loss in the shunt switch associated with discharging of parasitics (“turn-on loss”) can be reduced or, in certain cases, essentially eliminated.
As shown in
As shown in
As shown in
Care must be taken not to have the shunt switch and the recovery switch on at the same time, which would short-circuit the source.
The energy-trapping technique may be applied to any power converter, isolated or non-isolated, PWM or resonant, in which energy storage in inductive and capacitive circuit elements results in parasitic oscillations within the converter.
At time tcross the current Io declines to zero and attempts to reverse. After the diode 75 ceases conducting, the voltage VD rings up until the clamp diode 80 begins to conduct at time tc, when the voltage VD is approximately equal to Vout. Between times tc and tcoff the clamp circuit clamps the inductor and prevents parasitic oscillations. At time tcoff, the clamp switch is opened and the voltage VD rings up toward Vin. At time tson the switch 74 is closed, initiating another converter operating cycle. A switch controller 77 controls the relative timing of the two switches 74, 78. As for the timing discussed in
The transformer coupled clamp circuit of
Other embodiments are within the scope of the following claims.
For example, the technique may be applied to any switching power converter in which there is a time period during which undesired oscillations occur as a result of energy being transferred back and forth between unclamped inductive and capacitive energy storing elements.
The clamp circuit may be modified to be of the magnetically coupled kind shown in
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|International Classification||H02M3/155, G05F1/56, H02M3/28, H02M3/335, H02M1/34|
|Cooperative Classification||H02M1/34, H02M3/33576, H02M3/33569, Y02B70/1433, Y02B70/1491, H02M3/155, H02M2001/342|
|European Classification||H02M3/335S, H02M3/155, H02M1/34, H02M3/335S2|
|Aug 18, 2010||FPAY||Fee payment|
Year of fee payment: 8
|Jul 23, 2014||FPAY||Fee payment|
Year of fee payment: 12