DE102007057312A1 - Active power factor correction, for example in an LED converter - Google Patents

Abstract

A circuit (30, 40) for the isolated production of an output voltage (Vout), starting from a mains voltage (Vin), is proposed, comprising - a power factor correction circuit (31) with an inductance (L31) supplied by the mains voltage (Vin) and a controllable switch (T31) for controlling the charging and discharging of the inductance (L31) and - at least one potential separation transformer (N1-N2, N1'-N2 ') for galvanic isolation of the output voltage (Vout) to the mains voltage (Vin), wherein when discharging the inductance (L31) the potential separation transformer (N1-N2, N1'-N2 '), a first part of the energy stored by the inductance (L31) during charging is supplied directly.

Description

The The present invention relates to active power factor correction (in English Power Factor Control or PFC) and in particular on a circuit with galvanically isolated power factor correction. The technical field of application of the invention is in particular the the supply and control of a light source by means of such a circuit.

in the Generally, the power factor reflects the current drain an electrical device from the mains. The AC line voltage points known to have a sinusoidal time course and ideally Therefore, the current drawn from the grid should also be sinusoidal Time course have. This one with a power factor of 1 However, the ideal case characterized does not always occur, but rather can the current even deviates significantly from a sinusoidal envelope, where then the power factor drops.

at If the power factor is less than 1, the current removed is not sinusoidal, so that harmonics are generated in the mains current. These unwanted harmonic currents in the utility grid will be As is known, with the aid of a power factor correction circuit be reduced.

In order to achieve a sinusoidal and in phase to the mains AC voltage input current, for example, the use of a in. From the prior art 1 shown up-converter topology based active power factor correction circuit 20 known. "Active", therefore, because a switch is actively turned on and off by control signals from a control unit.

there a smoothing capacitor C21 filters a rectified one Input AC voltage Vin, by means of a voltage divider R21, R22 is measured. The input AC voltage Vin becomes one Inductor L21 supplied, wherein a secondary winding L22 the zero crossings of the current through the inductance L21 determines.

Farther enables a current measuring resistor (shunt) R23 in series to the switch, for example in the source line of a transistor T21, the detection of the peak inductor current to one possibly be able to determine overcurrent condition. Parallel to an output capacitor C22 is a second voltage divider R24, R25 arranged to measure the bus DC voltage Vbus and an overvoltage condition eg due to load jumps determine.

These four measurements are made using four measuring inputs 21 . 22 . 23 . 24 from a control circuit 25 performed, this control circuit 25 depending on these measurements, the transistor or switch T21 is controlled such that the bus voltage remains constant and the power factor is increased.

It is disadvantageous in this prior art that the circuit 20 can not supply galvanically isolated voltage.

The US 2007040516 A1 discloses in this context a circuit with power factor correction for the conversion of alternating voltage in galvanically isolated DC voltage. After a rectifier has converted a mains voltage into a rectified input AC voltage, this in turn is converted by a converter 10 converted into a DC voltage suitable for operating a lamp.

The in 2 shown converter 10 for generating the DC output voltage Vout is a half-bridge converter, which consists of a push-pull converter 11 and an output stage 12 for energy storage and low pass filtering exists.

The converter 10 is preceded by a power factor correction circuit (not shown), which provides as an active power factor correction for a nearly sinusoidal current consumption from the network. This upstream power factor correction circuit provides the converter 10 a step-up bus DC voltage Vin.

The push-pull converter or half-bridge 11 consists of two transistors T11, T12, such as two MOSFET transistors connected in parallel with two capacitors C11, C12. The center point of the two series-connected transistors T11, T12 is connected to the primary side n1 of a transformer such that one side of this primary transformer coil n1 is alternately connected to a positive and negative voltage. The other side of the primary transformer coil n2 is held at a fixed voltage by the capacitive voltage divider C11, C12.

On the secondary side n2 of the transformer is the through the push-pull converter 11 generated chopped AC voltage from the output stage 12 rectified and smoothed. The resulting output voltage Vout is then in continuous operation: Vout = f (n2 / n1 * Vbus).

It It is an object of the present invention to provide an improved circuit for the electrically isolated generation of an output voltage starting from to propose a mains voltage.

basic Idea of the invention is that a part of the current flow of the Switch of the active power factor correction circuit immediately the transformer is supplied and not only a temporary storage is subjected.

A Circuit for the isolated generation of an output voltage starting from a mains voltage can thus be a power factor correction circuit with an inductance and an actively controlled switch have, wherein the current flow from the inductance or through the switch (when it is closed) always to one Part of a caching is used in a capacitor while the other part of the current flow directly to a potential separation transformer is supplied.

The power factor correction circuit of the present invention on the one hand has the normal task of such a circuit, but on the other hand also assumes the function of the half bridge of US 2007040516 A1 ,

The Activation of the power factor correction switch is in particular at network level. If now the return secondary side, namely from the output voltage, this feedback must be be isolated, to continue a full Potential separation between the input side (mains side) and the To have an outlet side.

in principle So can the invention then be used advantageously, if there is a requirement for a potential-separated output voltage.

The Asked object is achieved by the Features of the independent claims solved. The dependent claims form the central one Thoughts of the invention in a particularly advantageous manner.

• – eine Leistungsfaktorkorrektur-Schaltung mit einer von der Netzspannung versorgte Induktivität und einem steuerbaren Schalter zur Steuerung des Ladens und Entladens der Induktivität, und
• – mindestens einen Potentialtrennungs-Transformator zur galvanischen Trennung der Ausgangsspannung zur Netzspannung. Beim Entladen der Induktivität wird dem Potentialtrennungs-Transformator ein erster Teil der von der Induktivität während des Ladens gespeicherten Energie direkt zugeführt.

According to a first aspect of the invention, a circuit for electrically isolated generation of an output voltage from a mains voltage (in general: input voltage)

• A power factor correction circuit having a mains voltage supplied inductance and a controllable switch for controlling the charging and discharging of the inductance, and
• - At least one potential separation transformer for galvanic isolation of the output voltage to the mains voltage. When the inductance is discharged, a first portion of the energy stored by the inductor during charging is directly supplied to the potential separation transformer.

The Circuit can have at least one capacitor for caching a second part of the inductance during of the store stored energy.

The Energy cached by the capacitor may be preferred to the potential separation transformer be forwarded in the next load / unload cycle.

The Power factor correction circuit can be in a continuous or discontinuous mode.

The Energy storage performance of the capacitor may be smaller as that of an electrolytic capacitor.

The Output voltage can be filtered by a low-pass filter.

According to one Another first aspect of the invention is a control gear for light sources, such as, for example, a light-emitting diode converter proposed with a circuit described above.

• – die Netzspannung eine Induktivität einer Leistungsfaktorkorrektur-Schaltung versorgt, – ein steuerbarer Schalter der Leistungsfaktorkorrektur-Schaltung das Laden und Entladen der Induktivität steuert, und
• – ein Potentialtrennungs-Transformator zur galvanischen Trennung der Ausgangsspannung zur Netzspannung dient. Beim Entladen der Induktivität wird dem Potentialtrennungs-Transformator ein erster Teil der von der Induktivität während des Ladens gespeicherten Energie direkt zugeführt.

According to a further first aspect of the invention, a method is proposed for electrically isolated generation of an output voltage from a mains voltage (generally: input voltage), wherein

• The line voltage supplies an inductance of a power factor correction circuit, a controllable switch of the power factor correction circuit controls the charging and discharging of the inductance, and
• - A potential separation transformer for galvanic isolation of the output voltage to the mains voltage is used. When the inductance is discharged, a first portion of the energy stored by the inductor during charging is directly supplied to the potential separation transformer.

One second part of the inductance during Energy stored in the store can be from at least one capacitor be cached.

The Cached energy from the capacitor can be forwarded to the potential separation transformer become.

• – eine Leistungsfaktorkorrektur-Schaltung zur Erzeugung einer nicht-potentialgetrennten Busspannung,
• – eine Steuerschaltung zur Steuerung der Leistungsfaktorkorrektur-Schaltung, wobei die zum Zweck dieser Steuerung notwendige Erkenntnis der Busspannung von der Ermittlung der Ausgangsspannung hergeleitet wird.

According to a further first aspect of the invention, a circuit for the potential-separated generation of an output voltage starting from a mains voltage is proposed. In particular, it indicates:

• A power factor correction circuit for generating a non-isolated bus voltage,
• - A control circuit for controlling the quiet tion factor correction circuit, wherein the purpose of this control necessary knowledge of the bus voltage is derived from the determination of the output voltage.

According to one Another first aspect of the invention is a light-emitting diode converter proposed with such a circuit.

• – eine Leistungsfaktorkorrektur-Schaltung eine nicht-potentialgetrennte Busspannung erzeugt, und
• – eine Steuerschaltung die Leistungsfaktorkorrektur-Schaltung steuert,
• – wobei die zum Zweck dieser Steuerung notwendige Erkenntnis der Busspannung von der Ermittlung der Ausgangsspannung abgeleitet wird.

According to a further first aspect of the invention, a method for the potential-separated generation of an output voltage from a mains voltage is proposed, wherein

• A power factor correction circuit generates a non-isolated bus voltage, and
• A control circuit controls the power factor correction circuit,
• - Wherein the purpose of this control necessary knowledge of the bus voltage is derived from the determination of the output voltage.

According to one Another first aspect of the invention is an integrated circuit proposed to carry out a method described above is designed.

Further Features and advantages of the invention will become apparent upon reading the following description of preferred embodiments, the refers to the drawing.

1 shows a known DC-DC converter for converting a DC voltage in a galvanically isolated DC voltage,

2 shows a known power factor correction circuit,

3 shows a circuit according to a first embodiment of the invention,

4 shows a circuit according to a second embodiment of the invention, and

5 shows a circuit according to a third embodiment of the invention.

In 3 is an embodiment of a power factor correction circuit 30 shown in accordance with the present invention.

On the input side is the power factor correction circuit 30 an input voltage Vin, which is a power factor correction circuit 31 supplied, which in turn generates a bus voltage Vbus.

These Input AC voltage Vin is preferably one of a rectifier rectified line voltage (not shown).

The input AC voltage Vin is supplied to an inductor L31, ie, a coil. The coil L31 is connected in series with a diode D31 between a first input terminal DC_IN / MAINS supplied with the input AC voltage Vin and a second bus terminal 33 to which the bus DC voltage Vbus is provided.

An output DC capacitor C31, which is preferably designed as an electrolytic capacitor, connects the bus connection 33 with mass. Parallel to this output DC capacitor C31 and two switches T32, T33 are connected in series. The switches or the circuit breakers T31, T32, T33 are preferably the same.

To the connection 32 between the coil L31 and the diode D31, a transistor or a controllable switch T31 is connected.

Between the drain line 32 of the switch T31 and the middle point 34 the switches T32, T33 are the primary side N1 of a first transformer N1-N2 and the primary side N1 'of a second transformer N1'-N2' connected in series. Although both transformers N1-N2, N1'-N2 'may be different, they are preferably the same size.

If the switch T31 is turned on, the coil L31 is grounded short-circuited and the diode D31 locked. The coil L31 charges itself up, so that energy is actually stored in this L31 coil can be.

at switched switch T31 thus flows from the network Vin the coil L31 a current through the switch T31.

A however, further current component comes from the midpoint of the switches T32, T33 via the primary side of the transformer N1, N2 through the switch T31.

at When the switch is open, the coil L31 is known to line up a current through the diode D31. It means that the diode D31 is conductive and that the coil L31 then over the diode D31 discharges into the output DC capacitor C31. The energy is thereby applied to the output DC capacitor C31 transferred.

Meanwhile, another current component now flows from the connection point 32 between the switch T31 and the diode D31 again around (this time in the opposite direction) via the primary side N1 of the transformer N1, N2 to the midpoint 34 the switch T32, T33.

In an on and off cycle of the switch T31, according to the invention, only a part of the flowing current is supplied to the output capacitor C31 and to the bus voltage Vbus. In contrast, according to the prior art, the whole current flows to the bus voltage, see 2 in combination with 1 ,

The secondary sides N2 and N2 'of the transformers N1-N2 and N1'-N2' are connected in series and each connected to a diode D32, D33. These two diodes D32, D33 are also at one point 36 connected to each other.

The tension that is between the midpoint 35 the transformers N1-N2, N1'-N2 'and the connection point 36 of the diodes D32, D33 is then fed to a low-pass filter and accordingly filtered or averaged.

This For example, low pass consists of a choke L32 and a Output capacitor C32, wherein at the output capacitor C32, the output voltage Vout yields.

4 shows a further embodiment of the invention. The power factor correction circuit shown there 40 essentially comprises the components of in 3 shown circuit 30 ,

The power factor correction circuit has faced 3 in that the output DC capacitor C31 has been replaced by two capacitors C41, C42 connected in series. These capacitors C41, C42 are preferably electrolytic capacitors.

The Switches T32, T33 are not in this embodiment more provided.

Parallel to each capacitor C41, C42, a diode D41, D42 is connected, wherein the center point 34 ' the capacitors C41, C42 and thus also the diodes D41, D42 is connected to the series arrangement of the two transformers N1-N2, N1'-N2 '.

The operation of the circuit 40 is similar to the one in 3 shown circuit 30 ,

Consequently In each cycle ton-toff of the switch T31 becomes part of the flowing one Current supplied to the bus voltage Vbus while the other part directly into the primary sides N1, N1 ' the transformers N1-N2, N1'-N2 'flows.

According to the invention accordingly directly through the transformers N1-N2, N1'-N2 'converted portion, that is not to hold the bus voltage Vbus via the electrolytic capacitors C41, C42 serves, directly and lossless implemented.

As a result, the capacitors C41, C42 according to FIG 4 be made simpler than in a conventional power factor correction circuit.

It is possibly even possible for the capacitors C41, C42 to dispense with electrolytic capacitors. This brings If necessary, cost advantages and service life benefits.

On In any case, by directly converting part of the current flow Capacity of the electrolytic capacitors C41, C42 significantly be reduced.

Of the two described embodiments 30 . 40 has the circuit embodiment 30 according to 3 most control margin, since it comprises the two switches or MOSFETs transistors T32, T33. However, this control has the following disadvantage that these switches T32, T33 must also be synchronized.

This additional effort to operate or control the circuit 30 , however, omitted in the circuit embodiment 40 according to 4 because the switches T32, T33 are not used there. This eliminates the need for a corresponding controller for these switches T32, T33, which simplifies power factor correction as a whole.

5 shows how the inventive active power factor correction based on the in 4 shown circuit 40 can be carried out.

Alternatively, according to the invention, the circuit topology of in 3 shown embodiment can be selected.

The switch T31 is controlled by a control circuit 50 driven. For this purpose, the control circuit 50 an exit 51 on, via the switch T31, a control signal is supplied. The frequency of the control signal (typically at least 10 kHz) and therefore the switching on and off of the switch 306 is much higher than the frequency of the mains voltage (typically 50 Hz) and the rectified input AC voltage (typically 100 Hz).

To determine the switch-on time t _on or the switch-off time toff of the switch T31 requires the control circuit 50 information about the bus voltage Vbus (or via the output voltage Vout) or via the zero crossing of the current through the coil L31.

This is because the turn-on time t _{on of} the switch T31, and hence the charging time of the coil L31 is controlled based on a comparison of the bus DC voltage Vbus with a fixed reference voltage and on the basis that the control circuit 50 Turn off the switch T31 until the current through the coil 301 has dropped to zero.

The Information about the zero crossing of the current through the Spool L31 is actually only needed in discontinuous operation, in which the coil current actually in each period drops to zero. In continuous operation, however, the coil current goes when switching off the switch T31 does not return to zero, so that this zero crossing information is not necessary either.

For The power factor correction can also provide information about the input voltage Vin or the peak current through the coil L31 are required, in the latter case in particular to overcurrent conditions to prevent.

So it remains to be noted that the control circuit 50 must know the bus DC voltage Vbus or the output voltage Vout and possibly also the input voltage Vin, the zero crossing of the coil current or the coil tip current.

As already out 2 As is known, the zero crossing of the coil current and the coil peak current can each be determined by means of a secondary winding L22 and a current measuring resistor R23.

However, unlike the prior art in which the control circuit 25 If the bus voltage Vbus and the profile of the mains input voltage Vin are monitored via two voltage dividers R21, R22 and R24, R25, the triggering of the switch T31 can detect the profile of the mains voltage as well as the output voltage at the filter C32, L32.

The Intermediate bus voltage Vbus, however, is no longer detected.

This is possible because the bus voltage Vbus via the Transformers N1-N2, N1'-N2 'with the output voltage Vout is "hard" coupled, so that any improper States at the bus voltage Vbus directly in the output voltage Vout would recognize.

5 also shows like a load 60 , In particular, a light source such as a light emitting diode, directly to the output of the power factor correction circuit 30 . 40 can be connected.

alternative can, for example, the light source by means of a subsequent converter (not shown) are controlled. This subsequent converter can be a simple constant current source. But the bulb can also be controlled by one or more converters with their own regulation, in which case these converters are preferably independent of each other Brightness settings (or controls) or controls.

The control circuit 50 has an additional entrance 61 which measures or records a load-dependent quantity (such as voltage, current or power).

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• US 2007040516 A1 [0009, 0017]

Claims (15)

Circuit ( 30 . 40 ) for the potential-separated generation of an output voltage (Vout) from an input voltage, such as a mains voltage (Vin), comprising - an active power factor correction circuit ( 31 ) with an inductance (L31) supplied by the input voltage (Vin) and a controllable switch (T31) for controlling the charging and discharging of the inductance (L31), and - at least one potential separation transformer (N1-N2, N1'-N2 ' ) for galvanically isolating the output voltage (Vout) from the input voltage (Vin), wherein when the inductance (L31) is discharged, the potential separation transformer (N1-N2, N1'-N2 ') receives a first portion of the inductance (L31) during stored energy is supplied directly to the store. Circuit ( 30 . 40 ) according to claim 1, comprising at least one capacitor (C31) for latching a second part of the energy stored by the inductance (L31) during charging. Circuit ( 30 . 40 ) according to claim 2, wherein the energy cached by the capacitor (C31) is forwarded to the potential separation transformer (N1-N2, N1'-N2 ') preferably in the next charge / discharge cycle. Circuit ( 30 . 40 ) according to one of the preceding claims, wherein the power factor correction circuit ( 31 ) is operated in a continuous or discontinuous mode. Circuit ( 30 . 40 ) according to one of the preceding claims, wherein the energy storage capacity of the capacitor (C31) is smaller than that of an electrolytic capacitor. Circuit ( 30 . 40 ) according to one of the preceding claims, wherein the output voltage (Vout) is filtered by a low-pass filter (L32, C32). Light-emitting diode converter with a circuit ( 30 . 40 ) according to one of the preceding claims. Operating device for light bulbs, comprising a circuit according to one of claims 1 to 6th A process for the potential-separated generating an output voltage (Vout) from a mains voltage (Vin), wherein - the mains voltage (Vin), an inductance (L31) of a ^Lei stungsfaktorkorrektur circuit ( 31 ), - a controllable switch (T31) of the power factor correction circuit ( 31 ) controls the charging and discharging of the inductance (L31), and - a potential separation transformer (N1-N2, N1'-N2 ') for the galvanic isolation of the output voltage (Vout) to the mains voltage (Vin), wherein when discharging the inductance ( L31) the potential separation transformer (N1-N2, N1'-N2 '), a first part of the energy stored by the inductance (L31) during charging is supplied directly. The method of claim 9, wherein a second part that of the inductor (L31) during charging stored energy of at least one capacitor (C31) cached becomes. The method of claim 10, wherein the of the capacitor (C31) cached energy the potential separation transformer (N1-N2, N1'-N2 ') is forwarded. Circuit ( 30 . 40 ) for the potential-separated generation of an output voltage (Vout) from a mains voltage (Vin), comprising - a power factor correction circuit ( 31 ) for generating a non-isolated bus voltage (Vbus), - a control circuit ( 50 ) for controlling the power factor correction circuit ( 31 ), wherein for the purpose of this control necessary knowledge of the bus voltage (Vbus) is derived from the determination of the output voltage (Vout). Operating device for lamps, for example light-emitting diode converter, comprising a circuit ( 30 . 40 ) according to claim 12. Method for electrically generating an output voltage (Vout) from a mains voltage (Vin), wherein - a power factor correction circuit ( 31 ) generates a non-isolated bus voltage (Vbus), and - a control circuit ( 50 ) the power factor correction circuit ( 31 ), wherein the knowledge of the bus voltage (Vbus) necessary for the purpose of this control is derived from the determination of the output voltage (Vout). Integrated circuit, characterized in that for carrying out a method according to one of the claims 9 to 11 and 14 is designed.