WO2015063334A1

WO2015063334A1 - Circuit arrangement for current monitoring and power supply unit

Info

Publication number: WO2015063334A1
Application number: PCT/EP2014/073722
Authority: WO
Inventors: Peter Busch
Original assignee: Fujitsu Technology Solutions Intellectual Property Gmbh
Priority date: 2013-11-04
Filing date: 2014-11-04
Publication date: 2015-05-07

Abstract

The invention relates to a circuit arrangement for current monitoring for a plurality of outputs (12V1,…,12V5) of a power supply unit. For each output (12V1,…,12V5), the circuit arrangement in this case comprises a comparison element (COMP1,... COMP5), which is set up to compare two input voltages, a current measuring resistor, which is arranged in a current path of the output, and a resistance component. In this arrangement, a first side of the current measuring resistor (RS1,... RS5) is connected to a first input of the comparison element (COMP1,... COMP5) and a second side of the current measuring resistor (RS1,... RS5) is connected to a second input of the comparison element (COMP1,... COMP5). In addition, the resistance component is connected to an input of the comparison element (COMP1,... COMP5). All resistance components of the plurality of outputs (12V1,…,12V5) are connected to a reference voltage circuit (RS) of the circuit arrangement via a reference voltage line (RL). The reference voltage circuit (RS) is set up to provide a constant reference voltage. The invention additionally relates to a power supply unit (13) having a plurality of outputs (12V1,…,12V5).

Description

description

Circuit arrangement for current monitoring and power supply The invention relates to a circuit arrangement for a

Current monitoring of a plurality of outputs of a power supply and a power supply with a plurality of outputs.

Power supplies for computer systems need to power various components of a computer system. PC power supplies can deliver high currents. In the case of a

Overload the power supply and also protect the consumer over-current shutdown devices are provided. Since it is possible for most PCs to operate the system with the housing open, there is a safety standard that requires that in the event of an overload, the power supplied must be below 240W (energy hazard). For higher total power, therefore, the output current is divided into several outputs (Rails), which are measured independently of each other and switch off the entire power supply in case of overload of at least one output.

Figure 1 shows a conventional circuit for

Current monitoring. An output voltage of a power supply unit is connected to a common supply line + 12VCS. From this common supply line + 12VCS refer individual

Outputs 12V1, 12V5 of the power supply a regulated voltage.

The number of outputs can vary in different power supplies and thus different cases. In all cases, the output voltage is generated together, then divided into individual outputs with current sense resistors RS1, RS5, etc., a voltage drop across the Current measuring resistors measured separately and then with the outputs, z. B. 12V1, 12V2, etc. connected.

Figure 1 shows a simple circuit suitable for a

Over-current shutdown is used. In Figure 1 are

exemplarily five different outputs 12V1, 12V5 a regulated voltage source PSU shown. Each output 12V1, 12V5 is connected to the regulated voltage source PSU via a common supply line + 12VCS. About the common supply line + 12VCS provides the regulated

Voltage source PSU a voltage of +12 V available. In the current path of each output 12V1, 12V5 is a

Current measuring resistor RS1, RS5 switched. Above that

respective current measuring resistor RS1, RS5, an output current can be measured for each individual output 12V1, 12V5. Since the voltage is regulated to +12 V, the output power can be determined by the current measurement. The delivered power is directly dependent on the electricity. One

Comparator per PSU output (only Compl and Comp5 drawn here) is connected to the positive comparison input via a series resistor, here RVlp, for example

Output side of the associated current sense resistor RS1 connected. The negative comparison input is connected via a series resistor RVln to the input side of the associated current measuring resistor RS1. The resistance of RVln and RVlp is normally the same. In FIG. 1, the comparison element Compl is a comparator that compares and amplifies (for example by a factor of 1000). At the negative input of the comparison element Compl is via the series resistor RVln the common supply line + 12VCS side facing the current sense resistor RS1

connected. To the positive entrance of the

Comparative element COMP1 is via the series resistor RVlp the the common supply line + 12VCS opposite side of the current sense resistor RS1 switched. The same applies to the further outputs 12V2, 12V5 where in FIG

For reasons of clarity, only the circuit parts of the outputs 12V1, 12V5 are shown. Between

Series resistor RVln and the negative input of the

Comparison element Compl is connected to a trim pot VR1 whose second connection is connected to ground. About the trim potentiometer VR1 can specifically

Voltage drop at the negative input of the

Comparison elements Compl are generated. Through this

adjustable voltage drop, the current measurement on the current sense resistor RS1 is adjusted so that the output of the comparison element Compl of "High" to "low" switches. To generate the setpoint differential voltage for the overcurrent shutdown, is by a variable resistor

(Trim potentiometer, eg VR1) between the negative

Comparative input and ground a voltage drop across the series resistor RS1, RS2, ... of the negative comparison input generated.

Similarly, at output 12V5 is a corresponding one

Circuit part shown. The comparison element COMP5 is connected to the current measuring resistor RS5 as described for output 12V1 via two series resistors RV5p and RV5n. The negative input of the comparator COMP5 is the side of the voltage line + 12VCS facing the

Current sense resistor RS5 connected. The negative input of the comparator COMP5 is connected to ground via a trim pot VR5 to regulate the corresponding voltage drop for the output 12V5 for setting the cut-off threshold. The advantage of this circuit is its simple structure. The disadvantage of the circuit is the dependence of the nominal differential voltage on the output voltage before

Current sensing resistors. For example, if the output voltage varies by 5 "6 due to load jumps, the switch-off threshold set with the trim potentiometer also becomes 5 ~ 6

vary .

For example, finds a very strong output 12V1

Load fluctuation takes place, it can happen that the

Voltage regulated by the common supply line + 12VCS breaks down. By breaking in this

In the following, the voltage OCP12V1 generated by the comparator COMP1 can also fall to "low" because the setpoint differential voltage in the input has briefly fallen in. Thus, a voltage-independent switch-off threshold is not ensured.

The object of the invention is a circuit arrangement for a current monitoring and a power supply with a

Show circuit arrangement for a current monitoring, which ensure a constant shutdown threshold.

According to a first aspect of the invention, the object is achieved by a circuit arrangement for current monitoring of a plurality of outputs of a power supply according to claim 1. In this case, the circuit arrangement comprises for each output: a comparison element which is set up to compare two input voltages, one

Current measuring resistor, which is arranged in a current path of the output and a resistance component. Here, a first side of the current sense resistor is connected to a first input of the comparison element and a second side of the current sense resistor is connected to a second input of the comparison element. In addition, the resistance device is connected to an input of the

Connected predicates. All resistance devices of the plurality of outputs are over one

Reference voltage line connected to a reference voltage circuit of the circuit arrangement. The

Reference voltage circuit is adapted to provide a constant reference voltage.

The circuit arrangement described above provides a constant reference voltage via the reference voltage circuit. Due to the fact that the resistance components are not on

Ground, but are connected to the reference voltage line, a reference to the first page of

Current sense resistor produced. This creates a

constant voltage drop, the constant reference voltage. Thus, the overcurrent cut-off threshold can be kept independent of load-side caused voltage fluctuations. The first side of the current measuring resistor can be connected via a series resistor to the first input of the

Be associated with predicates. The second side of the current sense resistor may be connected via a further series resistor to the second input of the comparison element. The series resistors can be dimensioned equal. The comparison element may be a comparator which, after comparing the two input voltages, one

Reinforcement performs, for example, by a factor of 1000.

According to an advantageous embodiment, the

Circuitry a common supply line for the majority of outputs. The common

Reference voltage circuit provides over the

Reference voltage line an auxiliary voltage that is smaller by the constant reference voltage than the voltage of the common supply line. Here's the first one

Input of each Vergleichselements connected via a series resistor to the reference voltage line. Furthermore, the second input of each comparison element is connected via a further series resistor to the respective output.

By providing the auxiliary voltage, a

set over-current cut-off threshold regardless of

the load side caused voltage fluctuations are kept, so that such voltage fluctuations the

Do not directly influence the overcurrent cut-off threshold. The subtraction of the reference voltage causes the

Auxiliary voltage is lower by a constant value than the voltage of the common supply line. Thus, the current monitoring is independent of variations of the common supply line.

According to a further advantageous embodiment of a series resistor and the resistance component form a

Voltage divider. The voltage divider is between the

common supply voltage line and the

Reference voltage line arranged. Here, the first input of the predicate is between the one

Series resistor and the resistor component connected. By dimensioning the voltage divider of the

Voltage drop can be controlled at the Vergleichselement. By the voltage divider, a voltage difference is set, which is a dimensioning of an output signal of Predictive elements allowed, whereby the switch-off threshold can be adjusted.

According to a further advantageous embodiment of the voltage divider is adjustable.

The fact that the voltage divider is adjustable, a resistance value of the voltage divider can be adjusted even after the installation of the circuit arrangement. This leads to a possibility to compensate for tolerances of the components of the current monitoring, but also to an increased flexibility in the choice and dimensioning of the installed parts, as well as the timing of adjusting the voltage divider. The built-up circuit can also be dimensioned separately for each output. For example, the

Voltage divider adjustable via a potentiometer.

According to a further advantageous embodiment, the reference voltage circuit comprises a reference element, in particular a Zener diode, with its cathode side to the

common supply line of the plurality of outputs is connected. The auxiliary voltage is thereby voltage stabilized with respect to a regulated output voltage. By using a reference element, a stabilized reference voltage can be realized with a low component cost. If the reference element is designed as a Zener diode, then the anode side of the Zener diode is connected to the reference voltage line.

According to a further advantageous embodiment, the reference voltage circuit comprises a capacitor which is parallel to the reference element between the common Supply line of the plurality of outputs and the

Reference voltage line is connected.

Through the capacitor, the voltage at the

Reference element also held in the case of voltage jumps on the common supply line of the plurality of outputs. Thus, a voltage smoothing element is connected in parallel with the Zener diode between the common supply line of the plurality of outputs and the reference voltage line.

According to a further advantageous embodiment, the reference voltage circuit comprises a shunt regulator. As a result, a reference voltage can be stable and independent of a current at the reference voltage line

to be provided.

According to a further advantageous embodiment, the reference voltage circuit comprises a voltage follower

wired operational amplifier.

In this case, only the minimum specified

Reference current flow through the reference element. One

predetermined deduction of a stream is not required. The voltage follower provides an output signal suitable for the

Reference voltage line can be used.

According to a further advantageous embodiment, the reference voltage line is connected to ground via a reference resistor. The reference resistance can be dimensioned so that at the expected maximum current (for example, 0.5 mA) through the resistor elements, in particular the adjustable resistors, and at least one minimally specified

Reference current (for example, 1 mA) through the

Reference voltage circuit flows. By the safe

Provision of the minimum specified reference current becomes the reference voltage circuit at an operating point

held .

According to a second aspect of the invention, the object is achieved by a power supply having a plurality of outputs and a current monitor according to the first aspect for at least two of the plurality of outputs.

The invention will be described below with reference to

Embodiments and figures explained in more detail.

In the figures show

Figure 1 is a conventional circuit arrangement for a

Current monitoring,

Figure 2 is a schematic representation of a

Computer Systems,

3 shows a circuit arrangement according to a

Embodiment of the invention, Figure 4 shows a reference voltage circuit according to

Embodiment of the invention, FIG. 5 shows a reference voltage circuit according to a

another embodiment of the invention and

6 shows a reference voltage circuit according to a

another embodiment of the invention.

FIG. 2 shows a computer system 10. The computer system 10 has a first consumer 11 and a second consumer

Consumers 12, which are supplied by a power supply 13 with power through three outputs 12V1, 12V2 and 12V3, e.g. a switching power supply. The power supply unit 13 has two further outputs 12V4 and 12V5 in FIG. 2, to which, however, no load is connected here. The power supply 13 has a fuse device, not shown, which allows a maximum power of 240 W for each of the outputs 12V1, 12V5. Will the maximum power of 240 W at a single output 12V1, 12V5 of the power supply 13

exceeded, the power supply 13 turns off to protect the power supply 13, the consumer 11 and 12 and a user. Of course, the amount of power allowed for different systems may vary

be dimensioned. Likewise, the power supply 13 may have any number of outputs. In the exemplary embodiment, the first consumer 11 is a

Processor. The consumer 11 in this case requires a maximum power that is below 240 W, for example 60 W. It is supplied via the output 12V1 of the power supply 13. The second consumer 12 is in the embodiment a

Graphics card whose power consumption is greater than 240 W at full load, for example at 300 W. The consumer 12 is therefore powered by the two outputs 12V2 and 12V3 of the power supply 13 with energy. Figure 3 shows a circuit arrangement according to an embodiment of the invention, which can be used for an improved overcurrent shutdown. The individual outputs 12V1, 12V5 correspond to those of FIG. 1

described outputs 12V1, 12V5. Each of the outputs

12V1, 12V5 is as in Figure 1, each with a

Current sense resistor RS1, RS5 provided in order to specify a "low" level in the case of overcurrent with the aid of a comparison element COMP1, COMP5

Comparisons COMP1, COMP5 Comparators that amplify after a comparison, for example by a factor of 1000. In another embodiment, the predicates COMP1, COMP5 are

Differential amplifier with a high output gain.

Each comparison element Compl, Comp5 is connected to the positive comparison input via a series resistor RVlp, RV5p to the output side of the associated current measuring resistor RS1, RS5. The negative comparison input each

Comparisons Compl, Comp5 is about one

Series resistor RVln, RV5n with the input side of the

associated current sense resistor RS1, RS5. The improved overcurrent shutdown combines the advantage of a voltage-independent shutdown threshold with the advantage of a simple structure. This is due to a common

Supply line + 12VCS a reference voltage circuit RS connected. The reference voltage circuit RS provides a common voltage via a reference voltage line RL trim potentiometers VR1, VR5 of the individual outputs 12V1, 12V5

Auxiliary voltage 12VZ ready. In this case, by the deduction of a stabilized reference voltage (or constant Reference voltage) from the regulated input voltage of the common supply line + 12VCS the

Current measuring resistors RS1, RS5 generates the common auxiliary voltage 12VZ. By a reference element Z, a fixed voltage difference (the constant reference voltage) between the voltage of the common supply line + 12VCS and the voltage of the reference voltage line RL is generated. The lower connections of all trimming potentiometers VR1... VR5 are no longer connected to ground but to the common auxiliary voltage 12VZ in comparison to the example according to FIG. This causes the trimming potentiometers VR1, VR5 to operate at constant voltage or at a voltage which is constantly below the supply voltage. This flows from the output voltage of the power supply

independent current through the trim potentiometers VR1, VR5 and thus generates an independent of the output voltage shutdown threshold.

The reference voltage circuit RS comprises in

Embodiment, a Zener diode, with their

Cathode side to the common supply line + 12VCS and connected with its anode side to the reference voltage line RL. The zener diode serves as a

Reference element Z. Parallel to the zener diode is a

Connected capacitor CZ, which additionally stabilizes the voltage. To the anode side of the Zener diode is the

Furthermore, a resistor RZ connected to the

Reference voltage circuit RS connects to ground. The resistance RZ is dimensioned so that at the maximum current to be expected through the trimming potentiometers (eg 0.5mA) at least the minimum specified

Reference current (eg 1 mA) through the reference element Z, For example, a zener diode flows. The capacitor CZ keeps the voltage across the reference element Z even in the case of voltage jumps on the common supply line

+ 12VCS constant.

The additional component cost consists of the

Reference element Z, in the embodiment of the Zener diode, a capacitor CZ and a resistor RZ. These three components are only needed once per power supply since they are shared by all outputs.

In an alternative embodiment, instead of the drawn Zener diode, it is expedient to use a reference element Z with three terminals (for example a shunt regulator) which is either without resistors (see FIG. 4) or with resistors (for example a TL431, see FIG )

is connected. By using a shunt regulator, a more stable, independent of the reference current

Reference voltage supplied. The wiring with resistors depends on the particular reference element Z used.

A further alternative is to decouple the common auxiliary voltage 12VZ from the reference element Z by an operational amplifier OP connected as a voltage follower (see FIG. 6). FIG. 6 shows a circuit detail in which the circuit parts of the individual outputs 12V1, 12V5 according to FIG

Overview in Figure 6, however, are not shown. Of the

Operational amplifier OP is connected to a positive input between the reference element Z and the reference resistor RZ. The negative output of the operational amplifier OP is connected according to the wiring as a voltage follower to the output of the operational amplifier OP. In this In this case, only the minimum specified reference current has to flow through the reference element Z. However, then the tolerances of the common auxiliary voltage 12VZ to the

Offset voltage of the operational amplifier increased. Of the

Capacitor CZ is optional in this embodiment. The corresponding connection line is therefore shown in dashed lines.

Reference sign list 10 Computer system

11, 12 consumers

13 power supply

12V1, 12V5 output

+ 12VCS common supply line

RS1, RS5 current sense resistor

PSU regulated voltage source COMP1, COMP5 comparison element

RVlp, RV5p, RVln, RV5n series resistor

VR1, VR5 trimming potentiometer

OCP12V1, OCP12V5 voltage signal

12VZ common auxiliary voltage Z reference element

CZ capacitor

RZ reference resistor

RS reference voltage circuit RL reference voltage line

Claims

claims

Circuit arrangement for current monitoring of a plurality of outputs (12V1, 12V5) of a power supply comprising for each output (12V1, 12V5):

- A comparison element (COMP1, COMP5), the

is set to two input voltages too

to compare;

a current measuring resistor (RS1, RS5) arranged in a current path of an output (12V1, 12V5); and

a resistance component, wherein a first side of the current measuring resistor (RS1,

RS5) with a first input of the

Comparison element (COMP1, COMP5) is connected and a second side of the current sense resistor (RS1,

RS5) with a second input of the

Comparative elements (COMP1, COMP5) is connected, in addition, the resistance device is connected to an input of the Vergleichselements (COMP1, COMP5) and

wherein all the resistance components of the plurality of outputs (12V1, 12V5) via a

Reference voltage line (RL) with a

Reference voltage circuit (RS) of the

Circuitry are connected, which is adapted to provide a constant reference voltage. 2. Circuit arrangement according to claim 1, wherein the

Circuitry a common supply line (+ 12VCS) for the plurality of outputs (13), and

the common reference voltage circuit (RS) via the reference voltage line (RL) a

Supplying auxiliary voltage which is smaller than the voltage of the common supply line (+ 12VCS) by the constant reference voltage, the first input of each comparator (COMP1, COMP5) is connected to the reference voltage line (RL) via a series resistor (RVln, RV5n), and

the second input of each comparison element (COMP1, COMP5) is connected to the respective output via a further series resistor (RVlp, RV5p).

Circuit arrangement according to claim 2, wherein the one series resistor (RVIn, RV5n) and the

Resistor component form a voltage divider, wherein the voltage divider between the common

Supply voltage line (+ 12VCS) and the

Reference voltage line (RL) is arranged, wherein the first input of the Vergleichselements (COMP1, COMP5) between the a series resistor (RVIn, RV5n) and the resistance device is connected.

Circuit arrangement according to Claim 3,

characterized in that the voltage divider

is adjustable.

Circuit arrangement according to claim 2 to 4, wherein the reference voltage circuit (RS) comprises a reference element (Z), in particular a Zener diode, with its cathode side on the common supply line (+ 12VCS) of the plurality of outputs (12V1, 12V5) is connected so that the auxiliary voltage is voltage stabilized with respect to a regulated output voltage of the power supply (13).

6. Circuit arrangement according to claim 5, wherein the

Reference voltage circuit (RS) comprises a capacitor (CZ) which is parallel to the reference element (Z) between the common supply line (+ 12VCS) of the plurality of outputs (12V1, 12V5) and the

Reference voltage line (RL) is connected.

7. Circuit arrangement according to claim 1 to 6, wherein the

Reference voltage circuit (RS) comprises a shunt regulator.

8. Circuit arrangement according to one of claims 1 to 4, wherein the reference voltage circuit (RS) comprises a connected as a voltage follower operational amplifier.

9. Circuit arrangement according to one of claims 1 to 8, wherein the reference voltage line (RL) via a

Reference resistor (RZ) is connected to ground.

10. Power supply (13) with a plurality of outputs (12V1, 12V5) with a circuit arrangement for a

Current monitoring according to one of claims 1 to 9 for at least two of the plurality of outputs (12V1,

12V5).