DE102006032418A1 - Voltage converter i.e. direct current-direct current-voltage converter for generating active voltage supply, has terminal provided for connecting inductor, and switches connecting terminal with input, outputs and ground line - Google Patents

Abstract

The converter has an input (1) supplying an input voltage (Vin), and an output (2) supplying an output voltage (Vout1). Another output (3) supplies an inverted output voltage (Vout2), and a terminal (4) is provided for connecting an inductor (5). Switches (S1-S4) connect the terminal with the input, the outputs and a ground line (6), where a control logic (7) controls the switches. The control unit is connected with control terminals of the switches. Each capacitor (C1, C2) is connected to the outputs, where the switches (S3, S4) have a diode. An independent claim is also included for a method for converting a voltage.

Description

The The present invention relates to a voltage converter and a method for voltage conversion.

to Conversion of DC voltages are usually inductive DCDC converters used. Such converters can for example, work according to the buck or the boost principle, depending on whether a downward or upconversion an input voltage desired is.

Should multiple output voltages are provided, so is normal one DCDC converter per desired one Output voltage required. However, this has the disadvantage that everyone Converter own inductance needed. This inductance becomes common realized as an external component and in any case has a relatively large space requirement.

In the essay "A pseudo CCM / DCM SIMO Switching Converter with Free Wheel Switching", Dongsheng Ma et al., IEEE International Solid-State Cercuits Conference 2002, Session 23, Analog Techniques, 23.6, 0-7803-7335-9 is a switched voltage converter with multiple outputs and a single inductance specified. Thus, two voltages of the same polarity can be delivered with different amount, in the example described there, an output voltage of 3 volts and a further output voltage of 2.5 volts.

task the present invention is to provide a voltage converter, the output voltages of different polarity generated and thereby with only an inductance gets along.

The Task is relative the device solved by a voltage converter, having an input for feeding an input voltage, a first output for providing an output voltage, a second output for providing an inverted output voltage, means to connect an inductance, and switching means comprising the means for connecting the inductor to the Input, the first output, the second output and a reference potential terminal couple.

To the proposed principle, the voltage converter is set up to with only one inductance two different output voltages, namely an output voltage and to provide an inverted output voltage.

For this purpose are switching means provided, the means for connecting the inductance with a Input of the voltage converter, a first output, a second Coupling output and a reference potential connection.

The Switching means are preferably designed so that the voltage converter in terms of the first output in a boost mode, ie as an up-converter, is working.

Regarding the second output for providing the inverted output voltage the voltage converter works preferentially as inverting converter, So as an inverting converter. That means the sign the voltage delivered to the second output when the voltage is positive Input voltage is negative.

Prefers The voltage converter comprises a control unit which controls the switching means controls.

The Control unit comprises in one embodiment an input to Respectively a clock signal. In another embodiment, the control unit comprises an internal clock generator. The clock is preferably used for Controlling the switching means in a periodic manner, for example for the operation of a clocked voltage transformer.

The Means for connection has an inductance prefers two connections, between which an inductance connectable is.

The Switching means preferably comprises four switches, one of which switch the input of the voltage transformer with the first connection of the means to connect an inductance coupled, a second switch the reference potential terminal with the second terminal of the means for connecting an inductance, a third switch connecting the first terminal of the means for connecting a inductance coupled to the second output of the voltage converter and a fourth Switch the second port of the means for connecting a inductance coupled to the first output of the voltage converter.

It is therefore an aspect of the proposed principle that the first Output of the voltage transformer at a connection of the means for connecting the Inductance over one Switch is formed and that the second output also has a Switch on another connection of the means for connecting the inductance is formed.

The Control unit is preferred for driving the switch with respective Control terminals of the Switch connected.

To realize a so-called Voltage Mode DCDC converter, the first and the second output are preferably via a means for voltage Measurement connected to the control unit.

alternative or additionally can Means be provided for current detection. Preferred is a first Means for current sensing in the load current branch at the first output and another means for current detection in the with the reference potential connected branch. This can be a so-called Current Mode DCDC converter be realized.

alternative or additionally can be a means of voltage measurement at the input of the voltage converter be connected to detect the input voltage, which also like the other means of voltage measurement and the means of current detection can be connected to the control unit.

In an embodiment a capacitor is connected to the first and the second output. Under certain conditions, for example when one is at the exit connected load is capacitive, can dispense with the capacitor become. The capacitor is in each case preferred with a reference potential terminal connected.

The Switches are preferred with respective transistors, for example Field effect transistors built.

Some the switch, for example the third and / or the fourth switch can but also include a diode.

Parallel to the means for connection an inductance For example, a bypass switch is provided in one embodiment.

Of the Bypass switch is switched so that when connected inductance formed a parallel connection of the inductance with the bypass switch is.

Of the Bypass switch preferably comprises a transistor, for example a field effect transistor. The bypass switch is in one embodiment connected to its control with the control unit.

Prefers is the means of connecting one inductance an inductance connected.

The inductance is preferred, each with a connection with a first and a second terminal of the means for connecting an inductance connected.

While the rest of the voltage converter is preferably implemented in an integrated circuit, the inductance an external to a semiconductor body, comprising the integrated circuit of the voltage converter, be connectable inductance. alternative can the inductance be an on-chip inductor.

Regarding the Procedure, the task is solved by feeding an input voltage, converting the input voltage into one Output voltage by means of an inductance and con vert the input voltage in an inverted output voltage by means of the inductance.

Prefers Both the input voltage and the output voltages are DC voltages.

The The input voltage is converted into the output voltage in an embodiment according to the boost principle.

the across from the input voltage is converted to an inverted one Output voltage preferably in a so-called inverting Business.

there the operation of the voltage converter is preferably clocked.

The Convert the input voltage to the output voltage and the Convert the input voltage to the inverted output voltage can in the pulsed operation preferably take place alternately periodically.

alternative it is also possible several consecutive clock periods long the boost operation perform and subsequently one or more clock periods in the inverting mode.

For example may be charging the inductor take place in a first clock phase. For this purpose, the inductance is preferred between the input of the voltage converter and a reference potential terminal connected. Subsequently, the inductance in a second clock phase be discharged by the input of the voltage transformer over the inductance is connected to the first output of the voltage converter.

following can again be performed the first clock phase, as already described. After that is preferably provided for providing the inverted output voltage the reference potential connection via the inductance with the input coupled to the inductor second output connect to.

After that can the described clock phases repeat periodically.

In an execution a further clock phase is provided in which the inductance bridges or shorted. This serves in particular to different To provide services at the first and second output.

In order to provided in all clock phases, the first and second output voltage can be it is advantageous to capacitively support the output voltage.

Further Details and embodiments of the proposed principle are Subject of the dependent Claims.

The Invention will be described below in several embodiments with reference to Figures explained in more detail.

there demonstrate:

1 A first embodiment of a voltage converter,

2 A second embodiment of a voltage converter,

3 A third embodiment of a voltage converter,

4 the voltage transformer of 3 in a first clock phase,

5 the voltage transformer of 3 in a second clock phase,

6 corresponds to 4 .

7 the voltage transformer of 3 in a third clock phase,

8th the voltage transformer of 2 in a fourth clock phase and

9 an embodiment of a voltage converter with diodes.

In the described embodiments like reference characters designate like or equivalent parts.

1 shows a first embodiment of a voltage converter according to the proposed principle. An entrance 1 serves to supply an input voltage Vin. A first exit 2 is arranged to provide a first output voltage Vout1 while at a second output 3 a second, inverted output voltage Vout2 can be tapped off. A means for connecting an inductance 5 includes two connections 4 . 4 ' , between which the inductance 5 is arranged. A first switch S1 connects the input 1 with the first connection 4 the inductance 5 , A second switch S2 connects the second port 4 ' the inductance 5 with a reference potential connection 6 while a third switch S3, the first terminal of the inductance 5 with the second exit 3 coupled. A fourth switch connects the second terminal of the inductor 5 with the first exit 2 of the converter. All switches S1 to S4 are controlled by a control unit 7 driven. This is the control unit 7 connected via respective control lines to respective control inputs of the switches S1 to S4. In addition, the control unit points 7 two inputs, one of which for voltage detection with the first output 2 and a second for voltage detection with the second output 3 connected is. The first and the second exit 2 . 3 are via a respective, against reference potential connection 6 switched capacitance C1, C2 stabilized. The capacity is in the present embodiment at the same time each part of the voltage converter.

Optionally, at least one means for current detection is provided, which measures the current in a current-carrying branch. In particular, a plurality of current measuring means are positioned to detect the currents through a plurality of switches. In the embodiment of 1 is a first means of current detection 8th between the second port 4 ' the inductance 5 and the fourth switch S4 and outputs a current at an output, which is connected to an input of the control unit 7 connected is. Another means of current detection 9 is between the second switch S2 and the reference potential terminal 6 switched and carries a measured current of the control unit 7 to.

The first switch S1, the inductance 5 , the second switch S2 and the fourth switch S4 and the first capacitor C1 are comprised of a circuit part with which in a boost operation, a voltage at the first output can be output, whose sign that of the voltage at the input 1 corresponds, but the amount is larger.

At the same time, an inverting operation is possible with the same inductance. This is the inductance 5 together with the first switch S1, the second switch S2 and the third switch S3 and the second capacitance C2 part of an inverting converter according to the proposed example.

Accordingly, the control unit as well as the inductance and the first and second switches S1, S2 can be used for the provision of both output voltages. Overall, the proposed principle results in a reduced chip area requirement and in particular the advantage of off supply voltages of different polarity and preferably the same amount with a DCDC converter arrangement to produce, which only requires an inductance.

The operation of the circuit of 1 should later on the basis of 4 to 7 be explained in more detail.

2 shows a development of the circuit of 1 , As far as the circuit of 2 with that of 1 used components and their advantageous interconnection matches a repetition of the description is avoided. Additionally is at 2 a bypass switch S5 is provided between the two terminals 4 the means for connecting the inductance 5 is switched.

With the additional switch it is possible to have different powers at the two outputs 2 . 3 provide. To further explain the operation is on 8th with associated description.

3 shows a development of the circuit of 1 , which differs from that in that the switches S1 to S4 of 1 in 3 are replaced by transistors T1 to T4. These are field-effect transistors of the self-locking type, whose gate connections are used for their control with the control unit 7 are connected.

4 shows the circuit of 3 in a first clock phase A. The inductance is charged with the input voltage Vin via the grounded through current path.

5 shows the transfer mode, in which the inductance is effectively between the input 1 and the first exit 2 is switched. This clock phase is designated B.

In a conventional one Boost operation with only one output voltage would be the clock cycles A, B alternate periodically.

6 and 7 describe the ones for generating the inverted output voltage at the output 3 required clock phases A, B *. The clock phase A of 6 corresponds to the clock phase A of 4 , The clock phase B * of 7 is characterized by having a current path between the second output 3 via the inductance 5 to the reference potential connection 6 is formed. This realizes an inverting operation.

In order now both at the second exit 2 as well as at the third exit 3 To provide different voltages, namely the output voltage Vout1 and the output voltage in inverted form Vout2, several modes are possible.

In a first mode, the four clock periods A, B, A, B * as based on 4 to 7 described, repeated periodically. Thus, an alternate operation is achieved.

alternative can in each case a plurality of identical clock sequences are carried out in succession, for example in a sequence A, B, A, B, A, B, A, B *, A, B *, A, B *. This is also called burst operation.

If different power at the two output terminals 2 . 3 can be provided, the additional switch 55 from 2 to be used.

8th describes the closed state of the switch S5. This keeps the current through the coil 5 at a certain lower limit. In this clock phase C, the in 8th is shown, the current flows in the loop and, when the on-resistance of the switch 5 is sufficiently small, keep the current through the coil constant. At the beginning of a subsequent phase A, whether in boost or inverted mode, the coil starts again with a starting current, namely the IDCO limit. This principle isolates load changes at one of the two outputs of the DCDC converter from the other output.

In another mode, it is therefore possible, after the sequence A, B, A, B * insert the clock phase C, which results in the periodic repetition of A, B, A, B *, C.

In a fourth mode, the clock phase A according to 6 which results in the sequence A, B, B *, A, B, B * and so on.

Of course you can also changed the order be, in a fifth Mode in which the sequence A, B *, B repeats periodically becomes.

In a preferred embodiment of the control method is the sum of the time intervals of all clock phases constant.

Constant voltages at the outputs 2 . 3 To achieve the control of the switch takes place as a function of the measured voltages and possibly currents as based on 1 explained.

9 shows a modification of the circuit of 3 , wherein the third switch T3 and the fourth switch T4 by respective Schottky diodes he are set. The first Schottky diode D1, which replaces the third transistor T3, is between the first terminal of the coil 5 and the second exit 3 in the reverse direction, while the second diode D2 between the second terminal of the coil 5 and the first exit 2 is poled in the forward direction.

These execution is characterized by the fact that the high voltage capability of the Circuit is improved. The breakdown voltage of the diodes is higher as in a standard NMOS transistor whose drain has a limited current Has dielectric strength.

The two Schottky diodes D1, D2 of 9 are designed as passive components.

In addition, a resistor R1 is between the second output 3 and an input of the control unit 7 connected. This resistor R1 together with an internal current source I1, which is connected to the input of the control unit and the resistor R1, is used to perform a level shift of the negative output voltage. As in 9 shown, the voltage at the output 2 directly through the control unit 7 be recorded. Alternatively, a resistor divider or a level shift could be provided to a network comprising a resistor and a current source.

In the described operation according to 4 to 7 , which can be referred to as alternating mode, it is recommended that the coil is driven in a löckenden operation and therefore at the beginning of each cycle, the coil current starts from zero. This simplifies the regulation.

In burst mode, in which several clock cycles of the same kind are repeated in each case, for example, A, B, A, B, A, B, A, B *, A, B *, A, B *, the change of the mode, for example by be triggered that at the first and second output 2 . 3 measured output voltage is compared with a set value, for example, plus 10 volts or minus 10 volts. In this case, the coil can be operated in either stacking or non-latching operation, since the two DCDC converters can be considered separately for stability and the influence of one on the other is negligible.

The proposed principle is, for example, for the active supply voltage generation of organic light emitting diodes, OLED, suitable, as well as for each other Application in which positive and negative supply voltages, which are stable, needed in the form of DC voltages.

1

entrance

2

first output

3

second output

4

connection

4 '

connection

5

inductance

6

Reference potential terminal

7

control unit

8th

medium for current detection

9

medium for current detection

A

first clock phase

B

second clock phase

B *

third clock phase

C

fourth clock phase

C1

capacitor

C2

capacitor

Claims (14)

Voltage transformer, comprising - an input ( 1 ) for supplying an input voltage (Vin), - a first output ( 2 ) for providing an output voltage (Vout1), - a second output ( 3 ) for providing an inverted output voltage (Vout2), - means ( 4 ) for connecting an inductance ( 5 ), - switching means (S1, S2, S3, S4), the means for connecting the inductance ( 5 ) with the entrance ( 1 ), the first output ( 2 ), the second output ( 3 ) and a reference potential terminal ( 6 ) couple. Voltage converter according to claim 1, characterized in that a control unit ( 7 ) is provided, which controls the switching means (S1, S2, S3, S4). Voltage transformer according to claim 1 or 2, characterized in that - the means for connecting an inductance ( 5 ) a first and a second connection ( 4 . 4 ' ), and that the switching means - a first switch (S1), the input ( 1 ) with the first connection ( 4 ), - a second switch (S2) connecting the reference potential terminal (6) to the second terminal (S2) 4 ' ), - a third switch (S3) connecting the first port ( 4 ) with the second output ( 3 ), and - a fourth switch (S4) connecting the second terminal (S4) 4 ' ) with the first output ( 2 ). Voltage transformer according to claim 2 and 3, characterized in that the control unit ( 7 ) is connected to respective control terminals of the first to fourth switches (S1, S2, S3, S4). Voltage transformer according to one of claims 1 to 4, as far as dependent on claim 2, characterized in that at least one means for voltage measurement at the first and / or at the second output ( 2 . 3 ) of the voltage converter is connected to an output of the at least one means for voltage measurement, which is connected to the control unit ( 7 ) connected is. Voltage converter according to one of claims 2 to 5, characterized in that at least one means for current detection ( 8th ) is provided in a circuit branch comprising a current branch, with an output of the at least one means for current detection, which is connected to the control unit ( 7 ) connected is. Voltage transformer according to claim 6, characterized in that the at least one means for current detection ( 8th ) is provided in a current branch comprising the second switch (S2) and / or in a current branch comprising the fourth switch (S4). Voltage transformer according to one of claims 1 to 7, characterized in that at the first and at the second output ( 2 . 3 ) each a capacitor (C1, C2) is connected. Voltage converter according to one of claims 1 to 8, as far as dependent on claim 3, characterized in that the third and / or the fourth switch (S3, S4) comprise a diode (D1, D2). Voltage transformer according to one of claims 1 to 9, characterized in that parallel to the means for connecting an inductance ( 5 ) a bypass switch (S5) is provided. Voltage converter according to one of claims 1 to 10, characterized in that an inductance ( 5 ) is connected to the means for connecting an inductance. Method for voltage conversion, comprising - supplying an input voltage (Vin), - converting the input voltage (Vin) into an output voltage (Vout1) by means of an inductance ( 5 ), - Converting the input voltage (Vin) into an inverted output voltage (Vout2) by means of the inductance ( 5 ). Method according to claim 12, characterized by - charging the inductance ( 5 ) in a first clock phase (A), - discharging the inductance ( 5 ) and providing the output voltage (Vout1) in a second clock phase (B), - discharging the inductance ( 5 ) and providing the inverted output voltage (Vout2) in a third clock phase (B *) Method according to Claim 13, characterized by bridging the inductance ( 5 ) in a fourth clock phase (C).