WO2011085866A2

WO2011085866A2 - Rectifier

Info

Publication number: WO2011085866A2
Application number: PCT/EP2010/068732
Authority: WO
Inventors: Richard Dilger
Original assignee: Osram Gesellschaft mit beschränkter Haftung
Priority date: 2010-01-15
Filing date: 2010-12-02
Publication date: 2011-07-21
Also published as: WO2011085866A3; DE102010000934A1

Abstract

The invention relates to a rectifier, comprising at least one electronic switch, wherein said electronic switch can be controlled by means of a capacitive voltage divider and an ohmic voltage divider. The invention further relates to an electronic ballast comprising such a rectifier and to a method for controlling the rectifier.

Description

description

Rectifier The invention relates to a rectifier, a

electronic ballast and a method for

Control of the rectifier.

A variety of electrical circuits requires the use of a rectifier. In particular, one is

Bridge rectifier known, also called Graetz circuit or two-pulse bridge circuit, in which four diodes are provided and converts an AC voltage into a pulsating DC voltage. Since this is a full-wave rectification, the negative half-cycle of the AC voltage in the DC voltage appears as a positive voltage. In addition, there are more

Rectifier (e.g., half-wave rectifier,

Midpoint rectifier, rectifier for

Three-phase alternating current), in which diodes or

Semiconductor switching elements, e.g. Mosfets, are usable.

There are so-called retrofit applications are known, which take over the shape of conventional lamps, in particular their socket with pistons essentially but instead of the technique of a light bulb electronics for operation

at least one semiconductor light-emitting element (for example at least one light-emitting diode) and the at least one

Semiconductor lighting element itself in the form of

Illuminant included. For example, such a retrofit bulb can be used instead of a conventional bulb, the technology of the retrofit bulb allows a much higher efficiency.

Instead of the at least one semiconductor light-emitting element, a gas discharge lamp or the like may also be provided. To operate the retrofit application, for example, the retrofit bulb has an electronic ballast (ECG) for operating the semiconductor light elements. The electronic ballast comprises a rectifier, which converts the applied AC voltage into a DC voltage.

The rectifier is also needed because the socket of conventional bulbs mostly no

Polarity coding, the inputs of a

Driver circuit for operating the semiconductor light elements, however, require a fixed polarity.

Also, it is desirable for the rectifier to have an alternating signal having a comparatively high frequency, e.g. in the range of 40 kHz, can handle.

Conventional rectifiers, whether one-way, two-way, or (full) bridge rectifiers, have high losses.

For example, as much as 15% of the total loss of an ECG may be due to a conventional four-diode bridge rectifier. Due to the high losses in the rectifier, the components are to be made correspondingly large in order to derive the resulting heat suitable. Since the installation space is limited, especially in retrofit applications, the size of the rectifier limits the possibilities or functionalities of the entire retrofit application. The object of the invention is to avoid the above-mentioned disadvantages and in particular to provide a possibility of an efficient rectifier which can be used, for example, in lighting applications, for example in retrofit lamps. This object is achieved according to the features of the independent claims. Further developments of the invention will become apparent from the dependent claims. To achieve the object, a rectifier is specified comprising at least one electronic switch, wherein the electronic switch by means of a capacitive

Voltage divider and by means of an ohmic

Voltage divider is controllable.

Thus, a rectifier diode or a rectifying component of a rectifier can advantageously be replaced by the electronic device proposed here

Switch which can be controlled by means of a capacitive voltage divider and by means of a resistive voltage divider. In particular, the electronic switch can each have a capacitive voltage divider and a resistive

Have voltage divider. In this case, it is advantageous that an efficient setting of the rectifier is possible by suitable adjustment of the two voltage dividers, even if not all the rectifying components (for example rectifier diodes) are replaced by the electronic switch proposed here.

A development is that the electronic switch has one of the following components:

a semiconductor switch,

a transistor,

a field effect transistor,

- a mosfet,

- an IGBT,

a BiCMOS switch,

- an IGBT. Another development is that the electronic switch instead of a rectifying component of the rectifier, in particular instead of a

Rectifier diode is used.

In particular, a diode of the rectifier by an electronic switch comprising a capacitive

Voltage divider and a resistive voltage divider to control the electronic switch to be replaced. Accordingly, two or more diodes of the

Rectifier be replaced.

In particular, it is a continuing education that the

Rectifier based on one of the following arrangements:

a bridge rectifier,

a half-wave rectifier,

a two-way rectifier,

- a mid-point rectifier,

a rectifier for a multiphase,

in particular a three-phase alternating current.

It is also a development that a switching input of the electronic switch is connected to a center tap of the ohmic voltage divider and to a center tap of the capacitive voltage divider.

The switching input is, for example, a gate terminal of a MOSFET or a base terminal of a (bipolar) transistor.

Furthermore, it is a training that

a channel connection of the electronic switch is connected to the first connection of an AC voltage source,

- The capacitive voltage divider with the second

Connection of the AC voltage source is connected, - the ohmic voltage divider with the second

Connection of the AC voltage source is connected.

The channel connection is a connection of the electronic switch, through which current can flow in the switched-on (or active) state. Of the

Channel connection of a mosfet includes e.g. a drain terminal and the channel terminal of a transistor include e.g. a collector connection.

As part of an additional training is the

Capacitive voltage divider parallel to the ohmic

Voltage divider executed. A next development is that the ohmic voltage divider at least two connected in series

Having resistors.

An embodiment is that of the capacitive

Voltage divider at least two in series

Has capacitors.

An alternative embodiment is that two n-channel MOSFETs are provided as electronic switches, each n-channel MOSFET having a capacitive

Voltage divider and a resistive voltage divider and has a parallel connection of the capacitive

Voltage divider and the ohmic voltage divider

is controllable.

The above object is also achieved by an electronic ballast for controlling a

Bulb or a lamp comprising a

Rectifier as described herein.

Furthermore, the above object is achieved by means of a method for driving the described here Rectifier, wherein the at least one electronic switch is controlled by means of the capacitive voltage divider and by means of the resistive voltage divider. Embodiments of the invention are illustrated and explained below with reference to the drawing. It shows:

Fig.l an exemplary circuit for a

Bridge rectifier with two n-channel MOSFETs and two diodes.

In particular, a rectifier is proposed comprising at least one electronic switch, e.g. a transistor, a mosfet, an IGBT, etc., wherein the electronic switch is driven by a capacitive and a resistive voltage divider.

The capacitive voltage divider and the resistive voltage divider are preferably designed parallel to one another.

The electronic switch can be dimensioned such that, in particular in conjunction with the capacitive and ohmic voltage divider, an alternating voltage with a frequency up to approximately 250 kHz can be rectified. In addition, the electronic switch may have a low threshold for its activation (i.e., a low voltage for

Activation of a gate of an n-channel MOSFET).

In particular, the solution proposed here can be used to at least one diode of a conventional

Rectifier to replace using the electronic switch in the proposed circuit with capacitive and ohmic voltage divider. For example, a

Bridge rectifier have two diodes and two n-channel MOSFETs. This will reduce the losses of

Rectifier, which significantly reduces the space required for the rectifier and the required cooling. Fig.l shows an exemplary circuit for a

Bridge rectifier with two n-channel MOSFETs 101, 102 and two diodes Dl, D2.

A (rectified) AC voltage 106 is connected to two nodes 104 and 105.

The drain terminal of the mosfet 101 and the anode of the diode Dl are connected to the node 104, respectively. The cathode of the diode Dl is connected to a terminal 103, on which a rectified signal can be tapped. The drain terminal of the mosfet 102 and the anode of the diode D2 are connected to the node 105, respectively. The cathode of the diode D2 is connected to the terminal 103.

The source terminal of the MOSFET 101 and the source terminal of the MOSFET 102 are each connected to ground.

Above the gate terminal and the drain terminal, the MOSFET 101 has a gate-drain capacitance C5, and above the gate terminal and the source terminal, the MOSFET 101 has a gate-source capacitance C6.

Accordingly, the MOSFET 102 has a gate-drain capacitance C7 over the gate terminal and the drain terminal, and a gate-source capacitance C8 above the gate terminal and the source terminal.

A series connection of a resistor Rl with a resistor R2 represents an ohmic voltage divider. This series circuit is connected on the one hand to the node 105 and on the other hand to ground. The center tap of this series connection of the resistors R 1 and R 2 is connected to the gate terminal of the MOSFET 101. A series connection of a capacitor Cl with a capacitor C2 represents a capacitive voltage divider. This series circuit is connected on the one hand to the node 105 and on the other hand to ground. The center tap of this series connection of the capacitors C 1 and C 2 is connected to the gate terminal of the MOSFET 101.

A series connection of a resistor R3 with a resistor R4 represents an ohmic voltage divider. This series circuit is connected on the one hand to the node 104 and on the other hand to ground. The center tap of this series connection of the resistors R3 and R4 is connected to the gate terminal of the Mosfets 102. A series arrangement of a capacitor C3 with a capacitor C4 represents a capacitive voltage divider. This series circuit is connected on the one hand to the node 104 and on the other hand to ground. The center tap of this series connection of the capacitors C3 and C4 is connected to the gate terminal of the MOSFET 102.

Thus, the Mosfet 101 will have a capacitive

Voltage divider comprising the capacitors Cl, C2 and a resistive voltage divider comprising the

Resistors Rl, R2 controlled. Sizing of the components can be determined as follows:

(1) The data sheet of the Mosfet 101 shall contain the

the following values are determined:

- C ' _lss for Uos ^ 0.2V ... IV, where Ups is a voltage

between the terminals drain and source of the mosfet 101;

- C _rss for U _DS = i / in-peak where U _iu _ _peak a

Peak voltage of the AC voltage source 106 denotes; a minimum value for a threshold value of the voltage GS-threshoid between the gate and source terminals of the mosfet 101.

A desired maximum value for the threshold value of the voltage U _GS. max between the gate and source terminals of mosfet 101 results in:

(3) The minimum value of the threshold tGS_threshoid results in:

CGS-C6 C _ISS - C _RSS ·

It is necessary to determine a corresponding value for the capacitor C2. Thus, efficient functionality of the mosfet 101 can be ensured.

According to the equation

Cl

Cl + C2 + C ", a value for the capacitor Cl can be determined

Accordingly, the design of the capacitive and the ohmic voltage divider for the Mosfet 202 can be carried out.

It is also possible that all diodes of the

Rectifier be replaced accordingly by electronic switches, with a capacitive and an ohmic voltage divider are provided for each electronic switch. Thus, the proposed rectifier allows an efficient supply of a consumer, such as a

Driver for driving a light source, e.g.

at least one semiconductor element. If one

Consumer is provided, the one

Minimum input voltage required to become active (e.g., a driver for driving a semiconductor light emitting element) may be applied to the load by means of the rectifier

Input signal can be provided, which already allows optimized operation of the consumer. Thus, the rectifier can provide the consumer with an input signal having a minimum voltage; in one

Voltage range up to this minimum voltage is therefore advantageously almost no power consumption by the consumer.

In particular, n-channel MOSFETs can be considered electronic

Switch can be used in the rectifier. Also, e.g. in addition, p-channel MOSFETs, e.g. instead of the diodes D1 and D2 shown in FIG.

The approach proposed here allows an at least partial compensation of the capacitances of the electronic switch, in particular the gate capacitances of a MOSFET, on the basis of the proposed capacitive and resistive ones

Voltage divider. In this respect it is possible that the

Rectifier can also be controlled with a high-frequency AC voltage.

In particular, a half-synchronous bridge rectification by means of the two n-channel MOSFETs shown in Fig.l an advantageous application, since already a significant

Increasing the efficiency of an electronic ballast can be achieved and the additional costs for the extension over a conventional bridge rectifier are low. In addition, it should be noted that the approach proposed here for a rectifier with at least one electronic switch can be used in different applications. In particular, the rectifier can be used in a ballast or in a retrofit application for a light source, for example in a lamp.

Claims

Comprising rectifier

- At least one electronic switch, wherein the electronic switch is controlled by means of a capacitive voltage divider and by means of a resistive voltage divider.

A rectifier according to claim 1, wherein the electronic switch comprises one of the following components:

a semiconductor switch,

a transistor,

a field effect transistor,

- a mosfet,

- an IGBT,

a BiCMOS switch,

- an IGBT.

Rectifier according to one of the preceding claims, wherein the electronic switch instead of a rectifying component of the rectifier,

in particular instead of a rectifier diode is used.

A rectifier according to any one of the preceding claims, wherein the rectifier is based on one of the following arrangements:

a bridge rectifier,

a half-wave rectifier,

a two-way rectifier,

- a mid-point rectifier,

a rectifier for a multiphase,

in particular a three-phase, alternating current.

5. Rectifier according to one of the preceding claims, wherein a switching input of the electronic switch with a center tap of the resistive voltage divider and with a center tap of the capacitive

Voltage divider is connected.

Rectifier according to claim 5,

- In which a channel connection of the electronic

Switch with the first connection one

AC source is connected,

- In which the capacitive voltage divider with the

second terminal of the AC voltage source is connected,

- In which the ohmic voltage divider is connected to the second terminal of the AC voltage source.

Rectifier according to one of claims 5 or 6, in which the capacitive voltage divider is designed parallel to the ohmic voltage divider.

Rectifier according to one of the preceding claims, wherein the resistive voltage divider comprises at least two resistors connected in series.

Rectifier according to one of the preceding claims, wherein the capacitive voltage divider comprises at least two capacitors connected in series.

Rectifier according to one of the preceding claims, wherein two n-channel MOSFETs as electronic

Switches are provided, wherein each n-channel MOSFET has a capacitive voltage divider and a resistive voltage divider and a

Parallel connection of the capacitive voltage divider and the ohmic voltage divider can be controlled.

Electronic ballast for controlling a lamp or a lamp comprising a

Rectifier according to one of the preceding

Claims . Method for controlling the rectifier according to one of claims 1 to 10, wherein the at least one electronic switch by means of the capacitive voltage divider and by means of the ohmic

Voltage divider is controlled.