JPH0527068B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an output level setting circuit included in a DC tester having a programmable power supply and incorporating an oscillator to enable AC output and AC measurement.

DC testers can perform DC output and DC measurements. By the way, by incorporating an oscillator into this DC tester, the output level of this oscillator can be freely controlled by a microcomputer program, so that even though it is a DC tester, it can be used for AC output and
It is designed to allow AC measurements. However, in order to incorporate such an oscillator and be able to perform AC output and AC measurement, it is necessary to change the memory capacity of the microcomputer or add or change programs to scan the oscillator output level. You will have to do something. Such changes are relatively cumbersome and can be costly.

The present invention utilizes a programmable power supply built into a DC tester to increase the memory capacity of a microcomputer and to control the output level of an oscillator easily and at low cost without the need to change the program. The purpose is to do.

Hereinafter, the present invention will be explained in detail based on an embodiment shown in the drawings.

The figure is a circuit diagram of an output level setting circuit according to this embodiment. Output level setting circuit 1 of this embodiment
is applied to a DC tester that has a programmable power supply and can control the output of this programmable power supply by a program of a built-in microcomputer. DC testers are typically capable of only DC output and measurements, but may be made capable of AC output and measurements by incorporating an oscillator. The output level setting circuit 1 of this embodiment allows the output level of an oscillator to be controlled by varying the output of a programmable power supply. That is, this output level setting circuit 1
has an oscillator 2 providing a sinusoidal output as shown in FIG. 2A, for example at 1 KHz and with an effective value of 1 V. On the other hand, as shown in FIG. 2B, for example,
The DC output of the 0.5V programmable power supply is given to the A/D converter 4 via the terminal 3. A/D
The converter 4 performs A/D conversion in accordance with the output level of the programmable power supply. The timing of this A/D conversion operation is determined by a means 7 comprising a zero cross comparator 5 that generates a detection output when the output level of the oscillator 2 is zero, and a frequency dividing circuit 6 that divides the frequency of the detection output of the zero cross comparator 5. determined by the output of Therefore, even if the level of the programmable power supply is switched, the A/D converter 4
The operation is performed when the output of the oscillator 2 crosses zero, thereby preventing unnecessary fluctuations (so-called fluctuations) in the level of the output that the circuit 1 of the embodiment provides to the external measurement circuit.

The output of the A/D converter 4 is given in parallel to the latch circuit 8 as a 12-bit digital signal whose content corresponds to the level of the programmable power supply. A timing signal for outputting the data to the D/A converter 9 is also provided. The latch circuit 8 is composed of, for example, three latch circuits each having a configuration of 4 bits, and is used to stabilize the output of the programmable power supply and then provide it to the D/A converter 9 at the next stage. A D/A converter 9 uses the output of the oscillator 2 as a reference voltage input and converts the output from the latch circuit 8 into a D/A converter. Therefore, the D/A converter 9 outputs a level corresponding to the level of the programmable power supply shown in FIG. 2B, for example, FIG. 2C with an effective value of 0.5V.
The oscillation output shown in is obtained. 10 is a buffer amplifier.

As described above, according to the present invention, the oscillation output level corresponding to the level of the programmable power supply is obtained from the D/A converter by varying the level of the programmable power supply, so that it is possible to increase the memory capacity of the microcomputer. With an easy and low-cost configuration, it is possible to provide AC output to the measurement circuit using the existing programmable power supply built into the DC tester, without having to create a program to scan the output level of the oscillator. . Further, according to the present invention, since the timing of the operation of A/D converting the output of the programmable power supply is set when the output of the oscillator crosses zero,
This is desirable because it can provide an output with less so-called wildness to the measurement circuit.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of an embodiment of the present invention, and FIG. 2 is a signal waveform diagram of each part. 1... Output level setting circuit, 2... Oscillator, 3
...Input terminal for programmable power supply, 4...A/
D converter, 5...Zero cross comparator, 6...
...Frequency divider circuit, 8...Latch circuit, 9...D/A converter.

Claims (1)

[Claims] 1. A DC tester that has a programmable power supply and is capable of AC output and AC measurement by incorporating an oscillator, the A/D converter converting the output of the programmable power supply into an A/D converter. /D
It has a converter, a latch circuit that latches the output of the A/D converter, and a D/A converter that uses the output of the oscillator as a reference voltage input and converts the output of the latch circuit to D/A, and the level of the programmable power supply. A variable output level setting circuit that outputs an AC signal from the D/A converter that corresponds to the level of the programmable power supply. 2 A DC tester that has a programmable power supply and is equipped with an oscillator to enable AC output and AC measurement, and is an A/D that converts the output of the programmable power supply into A/D.
A converter, a latch circuit that latches the output of the A/D converter, a D/A converter that uses the output of the oscillator as a reference voltage input and converts the output of the latch circuit to D/A, and a zero level of the output of the oscillator. and means for detecting the detection output and supplying the detection output to the A/D converter as a timing signal for the A/D conversion operation of the A/D converter, and detecting the detection output from the D/A converter by varying the level of the programmable power supply. Output level setting circuit that outputs an AC signal corresponding to the level of the programmable power supply.