The integrated voltage regulator is also called integrated power supply, and the circuit form mostly adopts series voltage regulation. Compared with discrete component regulators, the integrated regulator has many advantages such as fewer external components, convenient use, stable performance, and low price. The integrated voltage regulator can be roughly divided into three-terminal fixed type, three-terminal adjustable type, multi-terminal adjustable type and single-chip type switch according to the number of lead terminals and the use condition.
First, the measurement principle and method of the integrated regulator's adjustment rate parameterThe integrated voltage regulator (hereinafter referred to as the voltage regulator) is a commonly used device in electronic equipment, and the adjustment rate parameter is the main and key parameter reflecting the performance of the integrated voltage regulator, mainly including voltage regulation rate, current regulation rate and power adjustment rate ( Thermal adjustment rate). The measurement principle of the adjustment rate parameter is shown in Figure 1.
The voltage regulation rate parameter SV is defined as:
When the output current IL and the ambient temperature Ta remain the same, the relative change in the output voltage VO due to the change in the input voltage VI.
The current regulation rate (load regulation rate) is defined as:
When the input voltage VO and the ambient temperature Ta remain unchanged, the relative change in the output voltage VO due to the change in the output current IL.
The power adjustment rate is defined as:
When the input voltage VO, the output current IL, and the ambient temperature Ta remain unchanged, the relative change amount of the output voltage VO caused by the variation of the device chip temperature Tj due to the power pulse.
Second, the reason analysis and corresponding measures to influence the accuracy of the adjustment rate parameter testThere are several reasons for affecting the accuracy of the adjustment rate parameter test:
1. Detect ΔVO small change signal at output voltage VO
The test of each regulation parameter of the voltage regulator requires accurate measurement of the relative change amount ΔVO of the output voltage VO, which is usually a small number compared with the output voltage VO. The voltage output of the voltage regulator, VO, is typically a few volts, a few volts, or even tens of volts, while ΔVO is typically only a few tens of millivolts, a few millivolts, or even a fraction of a millivolt. There are several ways to ensure test accuracy:
a. Increase the number of digits in the voltmeter.
The voltage measurement can be measured by double integral method and bit by bit method. The double integral method is easier to obtain more test digits and higher measurement accuracy, but due to the long integration time (tens to hundreds of milliseconds), the sampling rate is reduced, which cannot meet the detailed specifications of the national military standard regulator for test time. Claim.
The bit-by-bit A/D has a high sampling rate, which can meet the test time requirements specified by the national military standard. However, to meet the measurement accuracy and resolution of the regulator output voltage variation ΔVO, 16 bits (or more) are required. ) A/D is pushed bit by bit, which usually requires expensive prices.
b. Sample and hold voltage compensation method.
The test principle of the sample-and-holder voltage compensation method is shown in Fig. 2. The value VO1 before the output voltage change is held by the sample-and-hold, and the difference between the value VO2 and the output voltage change is compared and amplified by the differential amplifier, that is, the output voltage variation ΔVO. With the sample-and-hold voltage compensation method, the output voltage variation ΔVO can be measured with a small voltage range. This reduces the number of A/D digits, which in turn reduces test costs. However, the sample and hold device is susceptible to various disturbances during operation, especially the interference caused by sudden changes in the load current, thus affecting the stability of the test data.
c. D/A voltage compensation method
The test principle of D/A voltage compensation method is shown in Figure 3. This method is similar to the sample-and-hold voltage compensation method except that the sample-and-hold is replaced by D/A. One input of the differential amplifier is connected to the output voltage VO to be measured. The other end is connected to a compensation D/A and programmed to have a voltage similar to VO. Perform A/D sampling before the change of the output voltage VO to obtain VO1. After the output voltage VO changes with the input voltage VI (or the output current IL), perform an A/D sampling to obtain VO2, and obtain two A/D samples. The values ​​are subtracted to obtain the desired ΔVO value. This method can also reduce the A/D digits compared with the sample-and-holder voltage compensation method, thus also reducing the test cost, but the D/A voltage stability and anti-interference ability are better than the sample-and-holder, plus D/A. The voltage compensation method requires two A/D samplings to eliminate system errors and therefore has better test results. It is only necessary to perform a VO test before the test to determine the D/A compensation voltage value, which is not a problem for the automated test system.
Because D/A voltage compensation method has the characteristics of high precision, good stability and low cost compared with other methods, and the test timing is in accordance with the detailed specifications of the national military standard, D/A voltage compensation method is the best. select.
2. Effect of device thermal effect on output voltage VO variation test
During the regulation of the regulator's regulation parameter, the corresponding input voltage VI and output current IL need to be applied to the device under test, so that the device under test is subjected to a certain power. This power will be caused by the thermal resistance of the device. The chip temperature Tj of the device under test rises. The output voltage VO of the regulator itself is also a function of temperature. Therefore, the output voltage variation ΔVO obtained in the measurement of the voltage regulation rate SV and the current regulation rate SI includes, on the one hand, the input voltage VI (or output). The change in current IL) causes the output voltage VO to change, which is exactly what we need to test. On the other hand, due to the change of power of the device under test, the temperature coefficient of the device will affect the value of the output voltage VO, which interferes with the measurement of ΔVO. The longer the measurement time of the device, the more prominent the problem.
In order to solve this problem, the test timing is clearly defined in the national military standard specification (such as GJB 597/42-96), and the test timing is shown in Figure 4.
The standard specifies an initial test of 0.5 mS before the leading edge of the voltage pulse (or current pulse) and a final test of 0.5 mS after the leading edge. The determination of this time is based on the consideration that the regulator output voltage VO requires a certain settling time as the input voltage VI (or the output current IL) changes. On the other hand, it is also considered to minimize the VO measurement due to the thermal effects of the device. influences. The standard also specifies the width of the voltage pulse (or current pulse).
In order to meet the test timing specified by the standard, a high performance requirement is imposed on a programmable constant voltage source that provides an input voltage VO in the test system and a programmable constant current source (electronic load) that provides an output current IL. In addition to meeting the voltage (current) accuracy required for the test, the test pulse should have good transient characteristics, ie, a straight pulse front and rear edge and a flat pulse top, while effectively suppressing self-oscillation during the test. . In order to meet this requirement, the programmable constant voltage source and constant current source in the test system need to be carefully designed and debugged.
3. Test system additional resistance and contact resistance on the output voltage change ΔVO test
In the test system, there are always cables and wires from the programmable electronic load to the device under test. In order to complete the test switching of different types of devices in the system, there will always be some plug-in conversion links, test adapter sockets and device under test. The pins are also connected by plug-in, which constitutes the additional resistance and contact resistance of the system. Although these resistors are small (milliohms), they can cause a voltage drop of the order of millivolts at an amperage level. For example, an output current of 1.5A flowing through a 10 mΩ resistor will produce a voltage drop of 15 mV. For the test of ΔVO in the order of millivolts, it has not been tolerated. Due to the instability of the contact resistance, it is not possible to compensate for the inaccuracy and instability of the ΔVO data by subtracting a fixed value. Therefore, the National Military Standard Specification specifies that the Kelvin connection must be used for the output of the regulator.
The so-called Kelvin connection requires the Kelvin four-terminal method to be connected in the test system from the programmable power supply, the electronic load, the voltage measuring device to the pin of the device under test. In addition to the way the system is wired, the test socket that ultimately connects to the device under test must use a Kelvin four-terminal socket. Only in this way can the internal resistance and contact resistance inside the system be effectively deducted, and the authenticity and accuracy of the adjustment rate parameter test can be guaranteed.
4. The effect of various interferences in the test system on the output voltage variation ΔVO test
In the automated test system, various disturbances also affect the measurement of the output voltage variation ΔVO, mainly high frequency interference, power frequency interference and random interference.
The high-frequency interference mainly comes from the microcomputer part of the test system. When the CPU is working, the control bus, the data bus and the address bus all have high-frequency signals on the mega frequency. These high-frequency digital signals pass through the ground system, the power supply system and some digital-analog. Hybrid chips can interfere with the operation and measurement of the analog portion of the system.
The power frequency interference mainly comes from the power grid. The 50 Hz AC and 100 Hz half-wave pulsation interference signals will interfere with the operation and measurement of the analog part of the system through the ground line system and the power supply system. The leakage flux of the power transformer is also a non-negligible factor.
Random interference is also mainly from the power grid. The startup and shutdown of high-power electrical appliances in the power grid will cause random spike interference in the power grid. When such interference occurs in the A/D sampling process, the accuracy of the test data will be seriously affected.
In order to eliminate the effects of the above various disturbances on the input voltage variation ΔVO test, the test system needs to take the following measures:
a. Place the measured portion of the output voltage VO in a test box away from the power transformer and take shielding measures.
b. Use no-current analog ground technology to effectively isolate digital ground and analog ground, and reduce interference introduced through analog ground.
c. Use effective digital processing and software filtering techniques, and use software to adjust the test sampling period to an integer multiple of the power frequency period.
d. Use the WAIT signal to force the CPU's bus signal to pause during sample-and-hold sampling and A/D conversion, giving the analog system a “quiet†sampling environment.
e. Use the 74HC tri-state bus driver to isolate the system data bus and D/A chip to prevent high frequency interference from being introduced from the D/A chip.
f. Use high frequency monolithic capacitors to perform effective high frequency filtering on the required parts of the system.
g. Properly lay out and route the PCB board, simulate some parts and lines are relatively concentrated, independent, and away from the digital part.
Third, STS 2108B integrated voltage regulator test systemThe STS 2108B integrated voltage regulator test system is an analog circuit test system developed and developed by Beijing Huafeng Measurement and Control Technology Co., Ltd. It is an upgraded version of the STS 2108A system. The company owns the independent intellectual property rights of the product.
The STS 2108B is suitable for parametric testing of fixed positive output, fixed negative output, adjustable positive output, and adjustable negative output regulators. The system test principle conforms to the national standard GB 4377-84.
The system has a 50V programmable input voltage range and 5A programmable output load current capability to complete output voltage VO, reference voltage VREF, startup voltage VST, voltage regulation SV, current regulation rate SI, standby dissipation current IDS, standby dissipation current Tests of parameters such as the amount of change ΔIDS (V), ΔIDS (I), output short-circuit current IOS, ripple rejection ratio Srip, and power adjustment rate SP.
The system meets the test requirements specified in the National Military Standard Specification GJB 597/4A-96 in pulse test, which can effectively avoid the interference of the thermal effect of the device under test, and also avoid the temperature rise of the device under test during the test.
The system selects the four-terminal test socket of the Kelvin Bridge of the United States 3M Company, and uses the Kelvin four-terminal method for parameter testing.
Because the system has good test accuracy and stability, it has been designated as the designated equipment for the national military standard integrated voltage regulator production line by Beijing Semiconductor Device Factory No. 5, No. 471, and No. 4,343, and other units. Research institutes, production plants and test centers are selected.
Uv Vacuum Curing Machine,Uv Protection Screen Protector,Uv Glass Curing Screen Protector,Uv Film Screen Protector Phone
Shenzhen TUOLI Electronic Technology Co., Ltd. , https://www.hydrogelprotector.com