JPH0348744B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a switching power supply testing device, and more particularly to testing of unregulated voltage.

[Prior Art] Switching power supplies are small, lightweight, and highly efficient, and are therefore widely used as power supplies for various devices.

One type of switching power supply is one in which the AC input voltage is rectified and smoothed and applied to the primary side of the transformer, and the DC voltage on the primary side is switched by a switching element to be transmitted to the secondary side of the transformer. There is an AC input type switching power supply in which a switching element is controlled to turn on and off so that the DC output voltage supplied to the load becomes a desired value by DC smoothing the switching voltage transmitted to the load.

In such a configuration, if the AC input voltage range is, for example, 90V to 250V, the duty of the switching element is, for example, 50V when the input is 90V.
% and is controlled to be 18% when inputting 250V. This allows the AC input voltage to range from 90V to
Even if the DC output voltage changes within the 250V range, the desired DC output voltage can always be supplied to the load.

Here, the ripple components of the AC input voltage are superimposed on the DC voltage applied to the primary side of the transformer, but the switching power supply also handles the peak and valley fluctuations of these ripple components in the range of 90V to 250V. It will work to compensate and stabilize,
The ripple superimposed on the DC output voltage supplied to the load becomes extremely small.

However, if the AC input voltage drops below 90V, it will deviate from the duty control range of the switching element, and the peaks and troughs of the ripple component of the AC input voltage superimposed on the DC voltage applied to the primary side of the transformer will change. Since the fluctuation cannot be compensated for anymore, the ripples superimposed on the DC output voltage supplied to the load rapidly increase.

The value of the AC input voltage at which ripples rapidly increase is standardized as the unregulation voltage, and is one of the test items for switching power supplies.

FIG. 3 is a block diagram showing an example of a conventional unregulation voltage testing device. In Figure 3, 1 is the switching power supply under test (unit under test, hereinafter referred to as UUT).
It is. 2 is an AC voltage source 2 that applies an AC input voltage AC to the input terminal IN of this UUT 1. 3 is
This is an oscilloscope connected to the output terminal OUT of UUT1. A DC output voltage DC is applied to this oscilloscope 3 through AC coupling, and the DC output voltage DC
Observation of ripples superimposed on the 4 is a voltage measuring device for measuring the AC output voltage AC of the AC voltage source 2;

In such a configuration, when testing the unregulation voltage of the UUT 1, the operator checks the AC output voltage AC of the AC voltage source 2 while observing ripples superimposed on the DC output voltage DC using the oscilloscope 3.
This is done by gradually lowering the rated voltage (for example, 100V) of the UUT 1 by manual operation, and reading the magnitude of the alternating current output voltage AC with the voltage measuring device 4 at the time when the ripple exceeds the standard value.

[Problems to be Solved by the Invention] However, according to such a conventional configuration, the test is performed manually by an operator, and there are drawbacks such as individual differences appearing in the test results and the fact that it takes a relatively long time.

The present invention has been made with attention to these points, and its purpose is to provide a switching power supply test device that can automatically test the unregulation voltage without manual intervention by an operator. It is in.

[Means for Solving the Problems] The present invention achieves the above object by rectifying and smoothing the AC input voltage and applying it to the primary side of the transformer, and switching the DC signal on the primary side using a switching element. is transmitted to the secondary side of the transformer,
A device for testing a switching power supply in which a switching element is controlled on and off so that the DC output voltage supplied to the load becomes a desired value by DC smoothing the switching voltage transmitted to the secondary side, Means for sequentially lowering the AC input voltage of the switching power supply under test from the rated voltage according to a control signal, and measuring the ripple superimposed on the DC output voltage of the switching power supply under test, and determining the AC input voltage at the point when it reaches a predetermined measured value. and means for measuring the held AC input voltage.

[Example] Hereinafter, an example of the present invention will be described in detail using the drawings.

FIG. 1 is a block diagram showing the main parts of an embodiment of the present invention, and the same parts as in FIG. 3 are given the same reference numerals. In FIG. 1, 5 is an AC voltage source that outputs an AC voltage AC applied to the input terminal IN of the UUT 1, and the magnitude of the AC output voltage AC is controlled according to the analog signal ACC applied from the DA converter 6. Ru. 7 is a comparator that compares the magnitude of the ripple voltage superimposed on the DC output voltage DC of UUT1 with a reference value AR; one input terminal is applied with the DC output voltage DC of UUT1 via an AC coupling capacitor C; The other input terminal has DA
A reference analog voltage AR is applied from a converter 8. The output signal CO of this comparator 7 is DA
When the magnitude of the ripple voltage applied to the converter 6 and superimposed on the DC output voltage DC of the UUT 1 exceeds the reference value AR, the conversion operation of the DA converter 6 is stopped and the output voltage AC of the AC voltage source 5 is reduced. is held at its current value. A transducer 9 converts the AC output voltage AC output from the AC voltage source 5 into a DC voltage ACD, and the converted analog DC voltage ACD is applied to the AD converter 10 and converted into a digital signal.

The operation of the circuit configured in this way will be explained using the waveform diagram of FIG. 2.

In FIG. 2, a shows the waveform of the analog control signal ACC applied from the DA converter 6 to the AC voltage source 5, b shows the waveform of the AC output voltage AC output from the AC voltage source 5, and c shows the waveform of the AC output voltage AC output from the AC voltage source 5. d shows the ripple waveform superimposed on the DC output voltage DC output from the comparator 7, and d shows the waveform of the output CO of the comparator 7.

Focusing on the AC output voltage AC of the AC voltage source 5,
Analog control signal applied from DA converter 6
According to ACC, the rated voltage at time _t1 decreases sequentially. Then, at time _t2 , when the voltage reaches a voltage that cannot be controlled internally by UUT1, the amplitude of the ripple superimposed on the DC output voltage DC output from UUT1 becomes larger than the reference voltage AR, and the output CO level of comparator 7 is reversed. do. As a result, the level of the output signal ACC of the DA converter 6 is held, and the AC output voltage AC of the AC voltage source 5 is also held. Then, the AC output voltage AC of the AC voltage source 5 in this state is converted into an analog DC voltage ACD by the transducer 9, and then converted into a digital signal by the DA converter 10 and read.

Such a series of test operations will be automatically executed under the control of a computer (not shown), which will reduce variations in measurement values and increase in measurement man-hours due to manual work by operators in the past. Inconveniences can be resolved.

[Effects of the Invention] As explained above, according to the present invention, it is possible to realize a switching power supply test device that can automatically test unregulation voltage without manual intervention by an operator, and it has practical effects. is big.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention;
FIG. 2 is a waveform diagram for explaining the operation of FIG. 1,
FIG. 3 is a block diagram showing an example of a conventional device. 1...Switching power supply to be tested (UUT),
5...AC voltage source, 6, 8...DA converter, 7...
... Comparator, 9 ... Transducer, 10
...AD converter.

Claims (1)

[Claims] 1. The AC input voltage is rectified and smoothed and applied to the primary side of the transformer, and the DC signal on the primary side is switched by a switching element to be transmitted to the secondary side of the transformer. This device tests a switching power supply in which the switching element is controlled on and off so that the DC output voltage supplied to the load becomes a desired value by DC smoothing the transmitted switching voltage. A means for sequentially lowering the AC input voltage from the rated voltage in accordance with a control signal, and a means for measuring the ripple superimposed on the DC output voltage of the switching power supply under test, and holding the AC input voltage at the point when it reaches a predetermined measured value. A switching power supply test device comprising: and means for measuring a held alternating current input voltage.