DE10213515B4 - Device for generating a supply voltage with a shunt regulator - Google Patents

Abstract

contraption for generating an internal supply voltage (VDDint) with a Shunt regulator (10, 12, 16), a second high-gain Stage (14), which is the shunt regulator (10, 12, 16) downstream and driving a third stage comprising a transistor (28), which regulates the supply voltage (VDDint), the second stage a second amplifier (14, 34) and at least one current mirror (20, 30, 32) and the second amplifier (14; 34) about at least one current mirror (20, 30, 32) the transistor (28) of the triggers third stage, characterized in that the second amplifier (34) a first current mirror (32) drives, the transistor (28) via a second and third current mirror (20, 30) drives in parallel and the second current mirror (20) further controlled by a current source (22) which is powered by an internal supply voltage (VDDint) becomes.

Description

The The invention relates to a device for generating a supply voltage with a shunt regulator according to claim 1.

shunt regulator are used, for example, in linear voltage regulators for generation used a regulated supply voltage. A shunt regulator serves to provide an excess of electricity from a power source to ground to dissipate. As control elements become prevalent Transistors used, which are driven by an amplifier, the compared to regulated supply voltage with a reference voltage and dependent on it controls the transistors. To generate the reference voltage is usually a bandgap circuit used by the regulated Supply voltage is fed.

Around from a high external supply voltage a low, regulated Supply voltage to produce, are usually so-called two-stage Bandgag controller used. Such regulators have a first stage which generates a control signal for setting a second stage. The second stage is here with the external, unregulated supply voltage connected. The second stage can also be countered by a shunt regulator Be formed mass. It is also known as a second stage one Emitter or source follower use.

5 shows such a two-stage bandgap regulator, wherein the second stage as an emitter-follower connected npn bipolar transistor 40 is used. The collector of the transistor 40 is connected to an external, unregulated supply voltage VDDext.

Emitter side is the transistor 40 with a load 24 connected. For driving the base of the transistor 40 is an amplifier 12 provided, the input side with a bandgap circuit 10 is connected. While the amplifier 12 is supplied from the external, unregulated supply voltage VDDext, the bandgap circuit 10 powered by an internal, regulated supply voltage VDDint, which is essentially across the transistor 40 is set. bandgap circuit 10 and amplifiers 12 form the first stage of this two-stage bandgag controller. A capacitor C1 (reference numeral 18 ) is at the output of the amplifier 12 against mass. It is used for simple, robust and EMC-proof dynamic compensation. However, this regulator has the serious disadvantage that a high voltage drop of at least one base-emitter voltage takes place in the output stage. Thus, the level of the internal regulated supply voltage VDDint is limited to approximately VDDext-0.8V.

In 6 is another two-stage bandgag controller shown, in contrast to the in 5 shown regulator instead of the transistor 40 a power source 42 and a pnp bipolar transistor connected as a shunt regulator 44 having. The transistor 44 gets from the amplifier 12 driven. Its load path is connected between the internal, regulated supply voltage VDDint and ground. Over transistor 44 will excess power from the power source 42 derived against mass. A disadvantage of this bandgag controller is a permanent high constant current, due to which the own power consumption is relatively high, especially at low load currents. Furthermore, the load current is limited by the set constant current; he can only be smaller than this. Finally, the control accuracy only corresponds to that of a single-stage operational amplifier, since the amplification of the second stage, essentially by the transistor 44 is formed, slightly less than 1.

However, it is advantageous in the case of the two regulators explained above that the dynamic stability requirements can be met in a straightforward and robust manner. This is especially due to the capacitor 18 formed capacity at the output of the first stage.

Around To reduce control deviations, two-stage control amplifiers are proposed in which the reinforcement the second stage much higher than 1. These control amplifiers or regulators are even more complicated to compensate dynamically, which is all the more true, even if a very good interference suppression required is. Also, these regulators in most cases, the power consumption the second stage still relatively high, since their base current consumption already very high.

Farther Multi-stage controllers have been proposed, which have a very good control accuracy exhibit. These are even more complicated than those described before two-stage control amplifier with a very high gain to stabilize in the second stage and robust against noise interpreted. An example of a three-stage regulator is in the article "A Low-Power Differential CMOS Bandgag Reference "T.L. Brooks, A.L. Westwick, IEEE-ISSCC 1994, Digest of Technical Papers, pp. 248-249. This controller ultimately regulates the power consumption in a shunt branch. However, that is the compromise to be realized between current consumption and load control speed disadvantageous: the bigger that Current mirror ratio, the smaller the power consumption, the larger a required one Compensation capacity. It also has to be bigger than usually be designed because the parasitic Polfrequenz in the output current mirror is smaller. However, this in turn leads to slow load control speeds.

In DE 44 31 466 C1 is a generic voltage regulator described. The in DE 44 31 466 C1 The voltage regulator described is equipped with a first p-channel MOS transistor and a first n-channel MOS transistor connected in parallel thereto, the gate terminals of which are coupled to an output of a control amplifier. The source terminal of the first p-channel transistor is connected to a first fixed point, and the source terminal of the first n-channel transistor is connected to a second fixed point. A switching device couples the current of the first p-channel transistor and the current of the first n-channel transistor to form a difference in a node connected to an output line. However, two parallel drive paths of an output transistor via a respective current mirror are not described therein.

US 4,549,129 A also discloses a voltage regulator having a shunt regulator and a second high-gain stage connected downstream of the shunt regulator, which activates a transistor in a third stage, which regulates a supply voltage. Also in this document are not described two parallel drive paths via a respective current mirror.

task The invention is therefore an apparatus for generating a Supply voltage with a shunt regulator, with the on the one hand, the supply voltage can be stably controlled and on the other hand has a low power consumption, a huge Can cover load current range and insensitive to interference signals is.

These The object is achieved by a device for generating a supply voltage solved with a shunt regulator with the features of claim 1. Further advantageous embodiments, embodiments and aspects of the present invention will be apparent from the dependent claims, which Description and the accompanying drawings.

One Advantage of the invention is a shunt with a especially highly reinforcing second and third stages combine so that the benefits a robust shunt regulator and the second and third stages stay without their drawbacks. This concerns in particular current consumption, Robustness, especially dynamic stability among all possible Operating conditions, Voltage drop, load range, interference suppression and / or Load control speed. Here is the control accuracy of correspond to a two- to three-stage amplifier arrangement. Such a device may advantageously be in circuits are used, with a particular unregulated supply voltage be fed and an internally reduced and regulated supply voltage with high stability and need low power consumption. Such circuits can for example, be implemented in a highly integrated technology, in which the device according to the invention implement particularly advantageous. Preferably, a low voltage drop between an external operating voltage the device according to the invention and a supply voltage generated from this.

Of Furthermore, the invention relates to a device for generating a Supply voltage with a shunt regulator. The device is drawing through a second high-gain stage, the shunt regulator is connected downstream, and a third stage, which is a transistor, which controls the supply voltage, and that of the second Stage is controlled. The second and third stages cause that the shunt current can be small and of the load be decoupled and therefore relatively independent of this regulated can. By controlling the supply voltage through the individual Third stage transistor can reduce the power consumption of the device and the voltage drop between an external voltage, which the device feeds and reduces the generated supply voltage become. In particular, the current consumption is opposite to a current of the load in all operating states the device only by a minimum amount larger. As a result, the load range can be very designed large be while the power consumption is not unnecessary increased in one or another case of operation. A high internal stability can be achieved by a Negative feedback of the second and third stage with the impedance of the Shunt regulator a high internal stability can be achieved. Likewise a high stability the second and third stages by an appropriately sized Actuator for the third stage transistor can be achieved. Another advantage is that the speed of control by the second and third stage inner loop formed to be high can, because this loop is bridged by the shunt regulator and so on a small reinforcement is set by about 1, which makes this loop no natural oscillations can generate.

In a preferred embodiment, the shunt regulator comprises a bandgap circuit, which is supplied by the supply voltage, a first amplifier for amplifying output signals of the bandgap circuit and a transistor connected as a source follower, which is driven by the output signal of the amplifier and whose load path is between the supply voltage and Reference potential is switched. The bandgap circuit and the first amplifier produce gen a voltage at the control terminal of the transistor, which is controlled by continuous measurement of the internal supply voltage. Via the transistor, positive deviations of the internal supply voltage can be corrected directly, since over its load path "excess" current can be dissipated.

to simple, robust, EMC-proof dynamic compensation can be between the output of the first amplifier and a reference potential to be a capacitance.

The second stage comprises a second amplifier and at least one current mirror. The second amplifier controls over at least one current mirror to the transistor of the third stage. On the at least one current mirror may be part of the output current of the first amplifier be mirrored in at least one path and thus the transistor influence the third stage.

In a circuitry very simple, presently preferred embodiment includes the second amplifier a transistor connected as a source follower.

Of the second amplifier drives a first current mirror, which connects the transistor via a second and third current mirror drives in parallel; the second Current mirror is also driven by a power source, the is powered by the supply voltage. In this case, in particular formed two paths, in which the part of the output current of the first amplifier is mirrored. This almost doubles the control speed the device.

Between the first current mirror and the control terminal of the transistor the load path of a second transistor can be switched, which is controlled by the supply voltage and its emitter or drain over a capacity is coupled to the supply voltage. This transistor works as a cascode and significantly improves the load control speed the device.

Around the effect of the cascode formed by the second transistor To ensure, the second transistor is preferably via a Low pass circuit activated.

Around a high gain slope to reach the first and / or second amplifier as Transconductance amplifier formed be. Transconductance amplifier form a kind of transconductance, which is an input voltage in one Output current converts. This will cause the load control speed elevated. Because the first and second stages are essentially the inner control loop their control speed can be higher by the use of transconductance amplifiers, in particular because a pole due to a usually existing output current level at the device according to the invention Does not exist. Transconductance amplifiers are voltage current amplifiers and provide an accurate gain-bandwidth product and essentially a feedback-free one gain so that they can be used here particularly advantageous.

Preferably the transistor of the third stage is designed such that its input capacitance the inner loop formed by the second and third stages the device compensated. This can otherwise be required compensation capacitors be saved.

Preferably becomes the device according to the invention used in an automotive and / or sensor circuit, since at such circuits, the advantages of the invention in the rule typical requirements are.

The Invention will be described in more detail with reference to figures of the drawing. Show it:

1 a first embodiment of the device according to the invention for generating a supply voltage;

2 A second embodiment of the device according to the invention for generating a supply voltage;

3A A third embodiment of the device according to the invention for generating a supply voltage;

3B an embodiment of a bandgap circuit for use in the device according to the invention;

4 A fourth embodiment of the device according to the invention for generating a supply voltage;

5 a bandgag regulator with an emitter follower according to the prior art; and

6 a bandgag regulator with a shunt regulator according to the prior art.

In the following, the same and in particular functionally identical elements are designated by the same reference numerals. To the description of 5 and 6 Reference is made to the introduction to the description.

In the 1 shown electronic scarf tion is used to generate a regulated supply voltage VDDint from an external, in particular unregulated supply voltage VDDext. Between the supply voltage VDDext and the internal supply voltage VDDint is the load path of a pnp bipolar transistor 28 connected. The transistor 28 acts as a third stage according to the invention with a slope gm3. The slope gm is defined by di / dV, ie the ratio of a current change to a voltage change. With the collector of the transistor 28 is a burden 24 connected to an output current of the transistor 28 is fed.

To control the transistor 28 a first and second stage of the electronic circuit are provided. The first stage is essentially a bandgap circuit 10 , a first transconductance amplifier 12 and a p-channel MOSFET connected as a shunt regulator 16 educated. The bandgap circuit 10 and the first transconductance amplifier 12 are powered by the supply voltage VDDint. The transconductance amplifier 12 amplifies output currents of the bandgap circuit 10 and generates a voltage at the gate of the p-channel MOSFET 16 is applied. The load path of the MOSFET 16 is connected between the supply voltage VDDint and ground. The MOSFET 16 thus acts as a shunt regulator for the supply voltage VDDint. Through him positive deviations of the regulated supply voltage VDDint can be corrected directly, as over its load path excess current can be derived to ground.

A part of an output current of the first amplifier 12 is via a second transconductance amplifier 14 over a current mirror 20 derived to mass. The second transconductance amplifier 14 and the current mirror 20 essentially form the second stage in the context of the invention. The second transconductance amplifier 14 compares the part of the output current of the first amplifier supplied to it 12 with a through a voltage source 26 given voltage Vth. As a result, a manipulated variable in two ways for an opposite drive of the transistor 28 generated. This effectively suppresses positive and negative noise both on the load side 24 as well as on the side of the supply voltage VDDext. Overall, the stability and robustness of a simple shunt regulator.

2 shows a further device for generating a regulated supply voltage VDDint, in which a part of the output current of the transconductance amplifier 12 via a first current mirror 32 in two more current mirrors 20 and 30 is mirrored. The part of the output current of the transconductance amplifier 12 is first via a p-channel MOSFET 34 in the current mirror 32 mirrored. The current mirror 32 has two outputs Out1 and Out2. The two outputs Out1 and Out2 correspond to two different current paths. The current path of the output Out2 leads via a current mirror 20 to an influence, in particular an increase in the potential at the base of the PNP bipolar transistor 28 , This causes the current through the transistor 28 decreases and the supply voltage VDDint is de-regulated. The current mirror 20 is the input side further with a power source 22 wired, the current mirror 20 fed with a constant current. This in turn causes the current mirror 20 provides a predetermined output current at its output Out, essentially by the current mirror 32 supplied current, ie is changed.

The further path through the output Out1 of the current mirror 32 leads over the current mirror 30 also to an increase of the potential at the base of the transistor 28 , As a result, the control speed is almost doubled.

On the one hand, by the circuit described above, excess current from the load 24 be weggeregelt and on the other hand missing power are applied. As a result, the internal supply voltage VDDint can be regulated relatively independently of the load. In the steady state of the illustrated circuit arises in the two p-channel MOSFETs 16 and 34 a current that essentially follows the constant current source 22 directed at the mirror conditions. The same applies to the current mirror 30 , As a supply current is thereby only the current through the load 24 and a constant shunt current is needed. The bandgap circuit 10 is thus regarded as a constant load.

The capacitor 18 at the output of the first transconductance amplifier 12 Serves for simple, robust and EMC fixed dynamic compensation. This simple combination is through the shunt-control transistors 16 and 34 possible, which are connected as a source follower, possible, since their gain to the internal supply voltage VDDint is slightly less than 1. The second and third stages, essentially by the current mirror 20 . 30 . 32 , the p-channel MOSFET 34 and the pnp bipolar transistor 28 significantly increase control accuracy through their internal high gain. The stages are characterized by a large input capacitance of the pnp bipolar transistor 28 compensated.

3A shows a further circuit for generating a supply voltage with a shunt regulator, wherein the internal structure of the in 2 illustrated current mirror 32 . 20 and 30 is shown. Furthermore, between the output of the current mirror 20 and the base of the transistor 28 an npn bipolar transistor 36 , more precisely switched its load path. The base of the npn bipolar transistor 36 is connected via a resistor R1 to the internal, regulated supply voltage VDDint. Further, the base of the transistor 36 connected via a capacitor C3 to ground. Another capacitor C2 connects the internal, regulated supply voltage VDDint to the emitter of the transistor 36 , This capacity serves as additional cascode Miller compensation, which accelerates the control behavior and increases the stability. An EMC-proof implementation of this compensation is ensured by the fact that both terminals of the capacitor C2 are below the regulated, internal supply voltage VDDint. As a result, the external supply voltage VDDext can respond less to the internal, regulated supply voltage VDDint. The load regulation speed is by a nearly direct path from the internal regulated supply voltage VDDint through the capacitor C2 and the npn bipolar transistor 36 to the base of the pnp bipolar transistor 28 improved. The effect of the cascode is ensured by the low-pass filter formed by the resistor R1 with the capacitor C3. The cascode no longer limits the control loop of the inner loop by an otherwise low transit frequency gm2 / (2πC2).

In the p-channel MOSFET branches, currents flow substantially through the constant current source 22 are predetermined. In the PNP bipolar transistor 28 Flows flow according to the load. The bipolar transistors can also be replaced by MOSFETs and vice versa. P-channel MOSFETs at the external supply voltage VDDext, however, need so-called reverse protection resistors in the bulk branch, so that the drain-bulk diode does not lead to a limitation of the reverse voltage.

3B shows a possible realization of the in the 1 - 3A pictured bandgap circuit 10 ,

4 shows a further circuit for generating a supply voltage with a shunt regulator. In this circuit, no current mirror are provided. This makes them relatively easy to implement without great technical effort and run especially with a few components. The current mirror 20 and 32 the in 3A shown here are essentially by the power source 38 replaced, which provides a constant current. Further, the current mirror 30 out 3A replaced by a simple resistor R2. In this circuit too, currents flow in the p-channel MOSFET branches, which are ultimately through a partial current of the constant current source 38 are predetermined. Furthermore, flow in the PNP bipolar transistor 28 Currents that are after the load 24 judge. In principle, the resistor R2 at the base of the pnp bipolar transistor 28 also be omitted or replaced by a power source.

The described circuits are preferably used in circuits in highly integrated technologies that used an internally reduced supply voltage with high stability and need low power consumption. Especially advantageous can the circuits in automotive and sensor circuits be used, especially if this is an internal regulated Need supply voltage, derived from an external supply voltage with a wide voltage range becomes.

10

Bandgag

12

first Transconductance amplifier

14

second Transconductance amplifier

16

p-channel MOSFET

18

capacitor

20

current mirror

22

power source

24

load

26

voltage source

28

PNP bipolar transistor

30

second current mirror

32

third current mirror

34

second MOSFET

36

NPN bipolar transistor

38

power source

40

NPN bipolar transistor

42

power source

44

PNP bipolar transistor

Claims (10)

Device for generating an internal supply voltage (VDDint) with a shunt regulator ( 10 . 12 . 16 ), a second high-gain stage ( 14 ), the shunt regulator ( 10 . 12 . 16 ) and drives a third stage comprising a transistor ( 28 ), which regulates the supply voltage (VDDint), wherein the second stage comprises a second amplifier ( 14 ; 34 ) and at least one current mirror ( 20 . 30 . 32 ) and the second amplifier ( 14 ; 34 ) via at least one current mirror ( 20 . 30 . 32 ) the transistor ( 28 ) the third stage, characterized in that the second amplifier ( 34 ) a first current mirror ( 32 ) driving the transistor ( 28 ) via a second and third current mirror ( 20 . 30 ) drives in parallel and the second current mirror ( 20 ) further from a power source ( 22 ), which is fed by an internal supply voltage (VDDint). Device according to claim 1, characterized in that the shunt regulator comprises a bandgap circuit ( 10 ), which is fed by the supply voltage (VDDint), a first amplifier ( 12 ) for amplifying output signals of the bandgap circuit ( 10 ) and a transistor connected as a source follower ( 16 ), which depends on the output signal of the amplifier ( 12 ) and whose load path is connected between the internal supply voltage (VDDint) and a reference potential. Device according to claim 2, characterized in that between the output of the first amplifier ( 12 ) and a reference potential a capacity ( 18 ) is switched. Device according to one of Claims 1 to 3, characterized in that the second amplifier has a transistor connected as a source stage or emitter stage ( 34 ). Apparatus according to claim 4, characterized in that between the first current mirror ( 20 ) and the control terminal of the transistor, the load path of a second transistor ( 36 ), which is controlled by the internal supply voltage (VDDint) and whose emitter or source is coupled via a capacitance (C2) to the internal supply voltage (VDDint). Device according to one of claims 1 to 5, characterized in that the second transistor ( 36 ) is controlled via a low-pass circuit (R1, C3). Device according to one or more of claims 2 to 6, characterized in that the first and / or second amplifier ( 14 ; 34 ) Are transconductance amplifiers. Device according to one or more of the preceding claims, characterized in that the transistor ( 28 ) of the third stage is designed so that its input capacitance compensates for the inner loop of the device formed by the second and third stages. Device according to one of the preceding claims, characterized characterized in that the internal supply voltage (VDDint) with connected to an output of the device, whereby additional external loads can be controlled. Use of the device according to one of claims 1 to 8 in an automotive and / or sensor circuit.