Electronic load module and a method and a system therefor

The present invention relates to an electronic load module and to a method and a system therefor. The method comprises receiving control data (301) from a connectable power controller via a data bus connector (202), and controlling (302) an active load (203) based on the received control data to sink a defined current from a connectable device under test via a first input (204). The method further comprises controlling (303) the activate load (203) based on the received control data by means of a digital control circuit (201) and the connectable power controller to generate and maintain an ambient temperature of the device under test.

CROSS REFERENCE TO RELATED APPLICATION(S)

This application is a 35 U.S.C. §371 National Phase Entry Application from PCT/EP2012/076781, filed Dec. 21, 2012, designating the United States, the disclosure of which is incorporated herein in its entirety by reference.

TECHNICAL FIELD

The present disclosure relates to an electronic load, and more particularly to an electronic load module configured for testing power supply systems on a printed board assembly as well as a method and a system therefor.

BACKGROUND

Modern integrated circuits, IC, consume more and more power at lower supply voltages. Therefore, the traditional approach of delivering converted power from a power supply unit (PSU) at the right voltage to the IC on a printed circuit board (PCB) via a connector on the PCB is no longer a viable solution. This can easily be understood by simple calculations using ohms law: an IC with a supply voltage of 2.2 V and a power consumption of 30 W requires a current of approximately 13 A. A PSU with such ratings exhibits large ohmic losses due to the resistance of the leads from the PSU to the IC.

A common solution to this problem is to place the PSU close to the IC on the PCB and to utilize an intermediate bus voltage provided to the PSU on the PCB via a connector. It is also common today to integrate a power controller on the PCB that controls all PSU's with a dedicated bus, such as a PMBUS for example.

This results in PCB's comprising several intertwined subsystems related to different functions of the circuit. One critical subsystem is the power supply system. The power supply system must provide large power consumers, such as a field programmable gate array (FPGA) circuit, with stable power at low supply voltage and high current. Especially the phase of turning on a FPGA circuit proves to be very demanding for the PSU since it is usually recommended to ramp-up the supply voltage in a controlled manner.

During the development of a modern PCB it is frequently desired to test each subsystem separately before integrating the full system on the PCB. Hence, in order to test the PSU system on the PCB an electronic load is needed to replace the current consuming subcircuits such as the FPGA circuit.

Such an electronic load is commonly available as bench-top equipment and rack mounted devices connected to the PCB by means of leads and connectors.

Another aspect to test is the effect of the environment on the PCB, and especially temperature effects on the stability and functionality of the power supply system on the PCB.

This environmental test is usually performed in an environmental test chamber, seeFIG. 1. Such an environmental test is performed by placing the PCB in the chamber with the electric load connected to the power supply system. The temperature in the chamber is gradually increased until the desired working temperature is reached. Then the electrical test of the power supply system is performed by turning on the power supply system and variate the electrical load to simulate different working conditions.

Some problems exists with this setup. First, the environmental test chamber is usually quite expensive and bulky. Secondly, the leads connecting the electronic load to the PCB are usually long and cause parasitic inductances and capacitances between the electronic load and the PCB. Such parasitic effects makes it difficult to correctly simulate slew-rate effects on the PCB by means of the electronic load.

SUMMARY

An object is therefore to address the problems and disadvantages outlined above, and to provide an improved electronic load module as well as a system and a method.

This object and others are achieved by the method, the electronic load module and the system according to the independent claims, and by the embodiments according to the dependent claims.

In accordance with one embodiment a method for operating an electronic load module is provided. The electronic load module comprises a digital control circuit configured to be connected to a power controller via a data bus connector, an active load operatively connected to and controlled by said digital control circuit and a first input operatively connected to the active load and configured to be connected to a device under test. The method comprises receiving control data from said connectable power controller via the data bus connector, and controlling the active load based on the received control data to sink a defined current from said connectable device under test via the first input. The method also comprises controlling the activate load based on the received control data by means of the digital control circuit and the connectable power controller to generate and maintain an ambient temperature of the device under test.

In accordance with another embodiment, an electronic load module is provided. The electronic load module comprises a digital control circuit configured to be connected to a power controller via a data bus connector, an active load operatively connected to and controlled by said digital control circuit, and a first input operatively connected to the active load and configured to be connected to a device under test. The digital control circuit is configured to receive control data from said connectable power controller via the data bus connector. The digital control circuit is further configured to control the active load to sink a defined current from said device under test via the first input. The activate load of the electronic load module is configured to be controlled by said digital control circuit to generate and maintain an ambient temperature of the connectable device under test.

In accordance with yet another embodiment a system for electrical loading of a device under test is provided. The system comprises a power controller configured to control at least one power converter circuit within the device under test, a physical housing of the device under test, and a temperature sensor operatively connected to said power controller and being configured to measure an ambient temperature inside said physical housing. The system further comprises an electronic load module configured to be controlled by said power controller and being configured to be arranged within the device under test. The electronic load module comprises an active load configured to sink a current from said device under test. The electronic load module of the system is configured to generate and maintain a defined ambient temperature within the physical housing of the device under test using the active load, and

the power controller is configured to control the ambient temperature within the physical housing based on said measured temperature and by means of the electronic load module.

An advantage of particular embodiments is that the conventional environmental test chamber becomes unnecessary.

DETAILED DESCRIPTION

In the following, different aspects will be described in more detail with references to certain embodiment and to the accompanying drawings. For purposes of explanation and without intention of limitation, specific details are set forth, such as particular scenarios and techniques, in order to provide a thorough understanding of the different embodiments. However, other embodiments that depart from these specific details may also exist.

FIG. 1is a schematic drawing of a conventional measurement set up, generally designated100, for performing measurements at elevated temperatures. This setup comprises an environmental test chamber101that can control the temperature inside the same. Inside the environmental test chamber101is a device under test (DUT)103arranged. The DUT103can be a PCB or a complete device with an internal PSU. To test the PSU of the DUT it is suitable to connect an electronic load102to the PSU. In order to connect the electronic load102to the DUT103leads104are arranged there between. These leads104are usually relatively thick in order to minimize the impact of ohmic losses.

A severe drawback of this system is the parasitic inductances and capacitances caused by the long leads104. These parasitic components make it very hard to perform precise slew-rate measurements on the DUT103.

Another drawback is related to the measurement setup itself. By arranging the electronic load102separated from the DUT103local heating effects in the DUT103is not captured during the measurement.

Therefore, it would be beneficial if these drawbacks could be obviated.

This disclosure describes a feasible way to overcome the shortcomings of the conventional setup system100.

Generally, a modern electronic circuit on a PCB often comprises some circuits that have huge power demands at low supply voltages. Such a circuit might be a Field Programmable Gate Array (FPGA). In order to fulfill the power need from the FPGA the PCB often includes several point of load (POL) voltage converters. These POL regulators are usually connected to a power controller via a dedicated bus, such as a power management bus (PMBUS). The power controller is configured to control each of the POL regulators via said dedicated bus.

FIG. 2is a schematic block diagram of an embodiment of an electronic load module, generally designated200. The electronic load module200comprises a digital control circuit201configured to be connected to the power controller mentioned above via a data bus connector202. The digital control circuit201is further connected to an active load203. The active load203further comprises a first input204configured to be connected to a OUT. The active load203is configured to sink a defined current from the first input204to ground potential and to generate and maintain an ambient temperature of the connectable OUT. The control of the active load203to sink the defined current or to generate heat, respectively, is performed by the digital control circuit201and the connectable power controller.

The control of the electronic load module is performed according to a method disclosed in the flowchart inFIG. 3. The method300comprises:

301: Receive control data from the connectable power controller via the data bus connector204. This control data may comprise defined set temperatures and defined set currents.

302: Control the active load to sink a defined current from said connectable DUT via the first input204.

303: Control the active load by means of the digital control circuit and the connectable power controller to generate and maintain the ambient temperature of the DUT. This step of the method uses the active load as a heating device for providing the necessary heat in order to bring the OUT to the defined temperature.

In one embodiment, the electronic load module200may be arranged to replace a FPGA on a PCB during a test phase. The electronic load module200may be in thermal contact with a heat sink provided for the FPGA.

InFIG. 4another embodiment of the electronic load module200is disclosed. In this embodiment is the digital control circuit provided with a computer interface401that is configured to be connected to an external computer. This computer interface may be used to reprogram the digital control circuit201. In one embodiment the computer interface is a JTAG interface.

In one embodiment comprises the active load203a second input400configured for supplying the active load203with external power from an external power supply for the purpose of heating.

An embodiment of an active load203will now be disclosed with reference made toFIG. 5. The active load203comprises said selector circuit501with the first input204configured to be connected to a DUT. The second input400of the active load203is configured to be connected to an external power supply for heating purposes. The selector circuit further comprises a select input502configured to receive a select signal from the digital control circuit201.

The active load further comprises a control input503configured for receiving an analog control signal from the digital control circuit201. This analog control signal from the digital control circuit201may be generated by a digital to analog converter of the digital control circuit201.

The active load203further comprises a MOSFET transistor T1with the drain thereof connected to an output of said selector circuit501, and the source being connected to ground potential via a first resistor R1.

The active load203further comprises an operational amplifier OP1having the non-inverting input connected to the output of a buffer amplifier A1. The input of the buffer amplifier A1is configured to be connected to said digital control circuit201via said control input503, the inverting input of the operational amplifier OP1being connected to the source of the MOSFET transistor via a second resistor R2forming a feedback loop, and the output of the operational amplifier OP1is connected to the inverting input of the operational amplifier OP1via a third resistor R3and a first capacitor C1. The output of the operational amplifier OP1is further connected to the gate of the MOSFET transistor T1.

The operation of the active load203will now be described with reference made toFIG. 5using a first scenario and a second scenario.

In the first scenario the first input204is selected by said select signal from the digital control circuit201. By applying a control voltage to the control input503the buffer amplifier A1applies the control voltage to the non-inverting input of the operational amplifier OP1. Due to the first feedback branch the operational amplifier will adjust its output voltage in order to achieve zero voltage offset between the non-inverting input and the inverting input of the operational amplifier OP1. Hence, the MOSFET transistor will be activated by means of the voltage potential of the gate thereof caused by the output of the operational amplifier OP1causing a current through the first resistor R1. The current through the first resistor R1causes a voltage drop over the first resistor R1. This voltage drop is fed back to the inverting input of the operational amplifier OP1. In this first scenario the current through the first resistor R1is controlled by means of the control voltage at the control input503.

In the second scenario the second input400is selected by said select signal from the digital control circuit201. The second input400is configured to be connected to the external power supply. In this second scenario, the purpose of connecting an external power supply is to use the MOSFET transistor to dissipate heat by flowing a current through the same. In this scenario the control voltage at the control input503is used to control the amount of heat that the MOSFET transistor dissipates.

FIG. 6is a schematic block diagram of an embodiment of a system600for electrical loading of a DUT601. The system comprises a power controller602configured to control at least one power converter circuit605within the DUT601, and a physical housing603of the DUT601. This housing603is used to shield the DUT601from the surrounding environment. This housing could also be a RF shield.

The system600further comprises a temperature sensor604operatively connected to said power controller602and being configured to measure a temperature inside said physical housing603.

The system600further comprises an electronic load module200configured to be controlled by said power controller602and being configured to be arranged within the DUT601. The electronic load module200comprises an active load203configured to sink a current from said DUT601

The electronic load module200is configured to generate and maintain a defined temperature within the housing603of the DUT601using the active load203. The power controller602is configured to control the temperature within the physical housing603based on said measured temperature by means of the electronic load module200.

Another embodiment of a system for electrical loading of a DUT is now disclosed with reference toFIG. 7. In this embodiment an external power supply701is connected to the second input400of the active load203. This external power supply may be used to generate heat and to maintain the temperature within said housing603. The whole test sequence is controlled and supervised via a control computer702. The control computer702is operatively connected to the power controller602by means of for example a computer bus such as a PMBUS.

The operation of this system can shortly be described as: measure the ambient temperature within the DUT601with the temperature sensor604and send the temperature data to the control computer702. If it is determined by the control computer702that the temperature must be increased, a command is sent from the control computer702via the power controller602to the electronic load module200. The digital control circuit201of the electronic load module200selects the second input400as an input source. Hence, the DUT601is disconnected from the electronic load module200by means of the selector circuit501. The active load203is then used to generate heat within the DUT601and the housing603. This heating is supervised and controlled by the power controller602and the control computer702. When the defined ambient temperature within the DUT601is reached, the external power supply is disconnected. At this point the DUT601is ready for testing by means of the electronic load module200. A test program emulating different loading conditions is then executed by the control computer702and performed by the electronic load module200. If it is determined that the DUT601needs some extra heating during the test sequence, the external power supply is then temporarily connected and used to heat the DUT601.

In one embodiment is the electronic load module200configured to be pin compatible with a circuit in the DUT and to use existing heatsinks within the DUT to dissipate heat. In this way realistic temperature distributions within the DUT601can be achieved.

Such a mounting of the electronic load module within the DUT601also enables realistic slew-rate tests. That may emulate the power-on sequence for a FPGA circuit. This can be attributed to the fact that long leads connecting a DUT to the electronic load is eliminated, or significantly reduced, resulting in a minimization of the parasitic elements.

In order to further illustrate the beneficial features of the system some exemplary scenarios will now be disclosed.

In the first exemplary scenario a PCB comprising a FPGA circuit will be described. The DUT601in this first exemplary scenario is a PCB with functions relating to a telecommunication system. The physical housing603of this DUT601is provided for RF shielding. In order to have sufficient power for the FPGA circuit a modern distributed PSS is utilized. This PSS comprises a power controller602operatively connected to several POL converters by means of a PMBUS. The designers of this PCB wants to test the capabilities of the PSS under different working conditions, unfortunately the FPGA sub-circuit is not ready for testing at this early stage of development. It is therefore desired to emulate the loading by the FPGA on the PSS by means of the electronic load module200. The electronic load module is configured to be pin compatible with the FPGA circuit, and therefore the electronic load module200is a drop-in replacement for the FPGA circuit. The MOSFET T1of the active load203is configured to be thermally connected to the heatsink of the FPGA. The electronic load module200is further configured to be controlled by Instructions received from the PMBUS via the data bus connector202. In this way no extra control leads are needed to control the electronic load module. The control computer702is connected to the power controller via a USB to PMBUS converter.

In this scenario no environmental test chamber is required and no long leads are required to connect the electronic load module200to the PCB. Hence, a very realistic test of the DUT is possible including the demanding slew-rate measurements.

In a second exemplary embodiment several active loads203are connected to the digital control circuit201. Accordingly, the electronic load module can generate heat and sink current simultaneously.

The above mentioned and described embodiments are given only as examples and should not be limiting to the present invention.

ABBREVIATIONS

DUT Device Under Test

FPGA Field Programmable Gate Array

JTAG Joint Test Acton Group

PCB Printed Circuit Board

PMBUS Power Management BUS

POL Point Of Load

PSS Power Supply System

PSU Power Supply Unit