Voltage margin test device

1. Technical Field

The present disclosure relates to test devices, and particularly to a test device to determine a voltage margin of an electronic device.

2. Description of Related Art

An electronic device, such as a computer motherboard, may work normally at a working voltage. The working voltage may vary between an allowable maximum and an allowable minimum, that is, the voltage may vary within a certain margin. To determine an acceptable voltage margin, testing is normally performed using expensive equipment.

FIG. 1 is a block diagram of an exemplary embodiment of a voltage margin test device, together with an electronic device to be tested.

FIG. 2 is a circuit diagram of the voltage margin test device of FIG. 1 .

Referring to FIGS. 1 and 2 , an exemplary embodiment of a voltage margin test device is used to determine a voltage margin of an electronic device 4 , such as a motherboard. The voltage margin test device includes a voltage generating module 1 , a voltage dividing module 2 connected to the voltage generating module 1 and the electronic device 4 , and a feedback voltage regulating module 3 connected to the voltage dividing module 2 .

The voltage generating module 1 includes a voltage output terminal Vout and a feedback voltage input terminal FB. The voltage output terminal Vout outputs a controllably varied working voltage to the electronic device 4 via the voltage dividing module 2 . The feedback voltage input terminal FB connects to the voltage dividing module 2 and receives a first regulation voltage or a second regulation voltage from the feedback voltage regulating module 3 . The working voltage is adjusted by the first and second regulation voltages. In one embodiment, the voltage generating module 1 may be a pulse width modulation (PWM) chip. And voltage of the voltage output terminal Vout is inversely proportional to voltage of the feedback voltage input terminal FB.

The voltage dividing module 2 includes two resistors R 1 , R 2 . A first terminal of the resistor R 1 is connected to the voltage output terminal Vout of the voltage generating module 1 and the electronic device 4 . A second terminal of the resistor R 1 is grounded via the resistor R 2 , and also connected to the feedback voltage input terminal FB of the voltage generating module 1 and the feedback voltage regulating module 3 .

The feedback voltage regulating module 3 includes a first voltage output unit 32 , a second voltage output unit 34 , and a switch unit 36 . The first voltage output unit 32 and the second voltage output unit 34 are connected to the switch unit 36 to respectively provide the first regulation voltage and the second regulation voltage.

The first voltage output unit 32 includes two resistors R 5 , R 7 , a sliding rheostat R 6 , an amplifier U 1 , a zener diode D 1 , and a diode D 2 . A non-inverting terminal of the amplifier U 1 is grounded via the sliding rheostat R 6 , and also connected to a cathode of the zener diode D 1 via the resistor R 5 . An anode of the zener diode D 1 is grounded. A power terminal of the amplifier U 1 and the cathode of the zener diode D 1 are connected to a +12 V power supply via the resistor R 7 . A ground terminal of the amplifier U 1 is grounded. An output terminal and an inverting terminal of the amplifier U 1 are connected to an anode of the diode D 2 . A cathode of the diode D 2 is connected to the switch unit 36 .

The second voltage output unit 34 includes a resistor R 4 , a sliding rheostat R 8 , an amplifier U 2 , and a zener diode D 3 . A non-inverting terminal of the amplifier U 2 is connected to a −8V power supply via the resistor R 4 , and also grounded via the sliding rheostat R 8 . A power terminal of the amplifier U 2 is connected to a +12 V power supply.

A ground terminal of the amplifier U 2 is grounded. An inverting terminal and an output terminal of the amplifier U 2 are connected to an anode of the zener diode D 3 . A cathode of the zener diode D 3 is connected to the switch unit 36 .

The switch unit 36 includes a single-pole three-throw switch SW 1 , a sliding rheostat R 3 , and a capacitor C 1 . A pole terminal 1 of the switch SW 1 is grounded via the capacitor C 1 , and also connected to a node between the resistors R 1 and R 2 via the sliding rheostat R 3 . A first throw terminal 2 of the switch SW 1 is connected to the cathode of the diode D 2 . A second throw terminal 3 of the switch SW 1 is idle. A third throw terminal 4 of the switch SW 1 is connected to the cathode of the zener diode D 3 . A maximum resistance of the sliding rheostat R 3 is at least ten times greater than resistance of the resistor R 2 .

Before conducting a test, the pole terminal 1 of the switch SW 1 is connected to the second throw terminal 3 , the resistance of the sliding rheostat R 3 is adjusted to be at least ten times greater than the resistance of resistor R 2 for increasing resistance of the feedback voltage regulating module 3 .

To determine the allowable minimum working voltage, the pole terminal 1 of the switch SW 1 is connected to the first throw terminal 2 . The resistance of the sliding rheostat R 6 is adjusted to be minimum and then gradually increased. A voltage at the inverting terminal of the amplifier U 1 is equal to a voltage at the output terminal of the amplifier U 1 . The first voltage output unit 32 outputs the first regulation voltage to the node between the resistors R 1 and R 2 of the voltage dividing module 2 and the feedback voltage input terminal FB of the feedback voltage regulating module 3 . The first regulation voltage is positive and increases with the resistance of the sliding rheostat R 6 increasing. Because voltage of the voltage output terminal Vout is inversely proportional to voltage of the feedback voltage input terminal FB, voltage of the feedback voltage input terminal FB increases to make voltage of the voltage output terminal Vout decrease. The working voltage is decreased gradually until the electronic device 4 cannot work, thus determining a minimum working voltage. A meter (not shown) can be used to measure the current working voltage to determine the allowable minimum of the working voltage. In this embodiment, the maximum resistance of the sliding rheostat R 3 is at least ten times greater than the resistance of the resistor R 2 , and the voltage at the node between the resistors R 1 and R 2 of the voltage dividing module 2 is far greater than the first regulation voltage, the diode D 2 is capable of preventing the voltage at the node between the resistors R 1 and R 2 from burning the amplifier U 1 . The capacitor C 1 can act as a filter or a buffer for stabilizing the first regulation voltage. The zener diode D 1 keeps a voltage at a node between the resistors R 5 and R 7 stable.

To determine the allowable maximum working voltage, the pole terminal 1 of the switch SW 1 is connected to the third terminal 4 , the resistance of the sliding rheostat R 8 is adjusted to be minimum, and then gradually increased. Voltage of the inverting terminal of the amplifier U 2 is equal to voltage of the output terminal of the amplifier U 2 . The second voltage output unit 34 outputs the second regulation voltage to the node between the resistors R 1 and R 2 of voltage dividing module 2 and the feedback voltage input terminal FB of the feedback voltage regulating module 3 . The second regulation voltage is negative and decreases with the resistance of the sliding rheostat R 8 increasing. Because voltage of the voltage output terminal Vout is inversely proportional to voltage of the feedback voltage input terminal FB, voltage of the feedback voltage input terminal FB decreases to make voltage of the voltage output terminal Vout increase. The working voltage dividing module 2 is increased gradually until the electronic device 4 cannot work, thus determining the maximum allowable working voltage. The meter can be used to measure the current working voltage to determine the allowable maximum of the working voltage. In this embodiment, the zener diode D 3 can prevent the amplifier U 2 from being burned.

It is to be understood, however, that even though numerous characteristics and advantages of the embodiments have been set forth in the foregoing description, together with details of the structure and function of the embodiments, the disclosure is illustrative only, and changes may be made in details, especially in matters of shape, size, and arrangement of parts within the principles of the embodiments to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.