The output of most DC power supplies provides a set voltage, which we call constant voltage mode (CV mode). Using "set fixed output voltage" to describe it can better express the overall meaning. At this time, the current of the power supply changes with the load.

However, this maximum fluctuation current cannot exceed the maximum design current of the power supply (to meet the application and price design goals) or the maximum set current (to protect the circuit under test). Therefore, once the load current exceeds any of the above current values, the power supply output will switch from CV mode to constant current mode (CC mode).

Taking DC power with a maximum design voltage/current of 30V/3A as an example. When the load does not exceed 3A, the power supply is in constant voltage mode, and the set output voltage can be 0~30V (based on the minimum setting resolution). Taking the output as 12V as an example, as long as the load does not exceed 3A, the ideal value of the output voltage is fixed at 12V (the unideal output is affected by specifications such as output accuracy, ripple/noise, line voltage regulation rate, load regulation rate, etc.), and the current value varies depending on load.

Once the load exceeds 3A (according to Ohm's law 12V/3A = 4 ohms, when the load is lower than 4 ohms, the load will exceed 3A), because the power supply can only provide 3A, it switches to constant current mode and the current is 3A, and the output voltage varies depending on the load.

The relationship between load, current and resistance is as follows: Generally, the reason why the current does not reach the set current is that the resistance is not small enough.

Large load = large current = small resistance; small load = small current = large resistance

How to set the maximum current:

• Knob setting: The output must be short-circuited to see the current reading. It is recommended to turn the knob to the state where the current is 0. If the knob is at the maximum current position, there may be sparks at the moment the output is short-circuited (possible shock). Slowly turn the knob from the position where the current reading is 0 to the required maximum set current.

• Button setting: Just use the number and unit buttons to input the required maximum set current.

More Porduct information: DC Power Supply

Dual-channel positive and negative low-dropout voltage regulators require positive and negative voltages for excitation. Three methods of generating positive and negative voltages are provided below.

Method 1: If you only have two single-channel DC power supplies, the wiring method is as follows:

Method 2: If you have a dual-channel DC power supply but there is no automatic wiring switch inside, you need to connect it externally.

Method 3: If you use GW Instek's dual-channel power supply, it has an automatic wiring switch.

They all claim to be dual-channel power supplies, but the devil is in the details, and details determine value.

There are many dual-channel DC power supplies on the market. In addition to providing two independent power supplies, dual-channel power supplies also have the following three applications due to their dual-channel design:

• Application 1: Series and parallel connection between channels. Series connection can meet the requirement of larger voltage applications, and parallel connection can meet the requirement of larger current applications.
• Application 2: Provide positive and negative voltages to test the DUT, such as a dual-channel positive and negative low dropout voltage regulator.
• Application 3: Simultaneous output of dual channels to excite the DUT that requires synchronous action.

The above three applications will have different impacts on users due to different designs. The followings are three designs on the market.

When used as separate channels, no difference can be seen between the three designs.

Applications in parallel

For design 1, when considering series and parallel applications, it can only be used in series but not in parallel. Design 2 requires users to spend more time on external wiring. GW Instek's automatic wiring design allows users to easily complete series and parallel applications.

Applications in series

After discussing the application 1 of series and parallel connections between channels. Next, let’s talk about application 2: providing positive and negative voltages to test the DUT.

Finally, the application of synchronous stimulation

The actual measurement comparison is between the output start-up and output shutdown transients of GW Instek's GPP series and a different brand. When outputting the same voltage, the inter-channel delay of GW Instek's GPP is extremely low (typical value is 0.1ms), while the other brand has a 12ms channel delay when turned on and there is a 100ms channel delay when turned off.

Summarize:

In addition to attaching importance to the details of multi-channel applications, GW Instek's GPP series multi-channel DC power supplies also provide the following features:

• Electronic load
• Sequential output
• Data collection/logging function is only available on channel 1 and channel 2
• Channel 3 outputs via USB Type A (only available on GPP3323/3060/6030)
• Series and parallel automatic tracking/automatic wiring (not available on GPP1326 single channel)

Compatible with the commands of GPD-x303S series DC power supply

More Porduct information: DC Power Supplies

GRA-450

The GRA-450 rack mount is suited for several models including GSM-20H10、PPH-1503、PPH-15XXD. The GRA-450 supports both the EIA (GRA-450-E) and JIS (GRA-450-J) standards. Incorporating a strong frame and robust design, the GRA-450 is specifically designed to hold one and two units and fits in a standard 19” 2U rack.

GRA-439-J (JIS) for ASR-2000 series

GRA-441-J (JIS) for PPX-series

GRA-442-J (JIS) for ASR-3000 series

GRA-449-J (JIS) for GPP-series

GRA-439-E (EIA) for ASR-2000 series

GRA-441-E (EIA) for PPX-series

GRA-442-E (EIA) for ASR-3000 series

GRA-449-E (EIA) for GPP-series

GRA-413-E for PEL-3221/3211H

GRA-423 for APS-7050/7100/7050E/7100E series

GRA-418-J (JIS) for PSB-1000 series

GRA-418-E (EIA) for PSB-1000 series

GRA-424 for PSB-2000 series

GRA-429 for APS-7200 series

GRA-431-J (JIS) for PFR series

GRA-414-E (EIA) for PEL-3021/3021H/3041/3041H/3111/3111H/3031E/3032E

GRA-424 for PSB-2000 series

GRA-419-J (JIS) for PCS-1000i

GRA-419-E (EIA) for PCS-1000

GRA-428 for PSP series

GRA-430 for APS-7300 series

GRA-431-E (EIA) for PFR series 

GRA-401 for PPE-3323/PPT-1830/PPT-3615

PEL-002 for PEL-2000 series

GRA-403 for PSH-series

GRA-407 for PSM-series and PST series

GRA-413-J (JIS) for PEL-3211/3211H

GRA-408 for PSS-2002/3203

GRA-409 for APS-1102A

GRA-410-J (JIS) for PSW-series

GRA-410-E (EIA) for PSW-series

GRA-414-J for PEL-3021/3021H/3041/3041H/3111/3111H/3031E/3032E

The electronic load verifying the LED driver not only has the functions of a general electronic load (CC, CR, CV, CP), but also must be able to simulate the load characteristics of the LED, set the forward bias (Vd) and the on-resistance ( Rd), etc. In addition, the built-in dimming control signal output is convenient for the PWM dimming test of the LED driver.

The dedicated electronic loads that GW Instek supports for LED driver testing are as follows:

• Must be installed on  3302G mainframe [single channel], 3305G [two channels] or 3300G [four channels], and the mainframe has 150 sets of store/recall memory
• 341G LED DC Electronic Load Simulator 300V, 24A, 300W
• 3342G LED DC Electronic Load Simulator 500V, 12A, 300W
• 3343G LED DC Electronic Load Simulator 500V, 24A, 300W
• 3345G LED DC Electronic Load Simulator 120V, 4A, 150W
• 3346G LED DC Electronic Load Simulator 120V, 12A, 300W
• 33401G LED DC Electronic Load Simulator 500V, 6A, 150W*2
• 33402G LED DC Electronic Load Simulator 120V, 2A, 75Wx2
• 33403G LED DC Electronic Load Simulator 120V, 6A, 150Wx2

• The power input dimming frequency of 3345G & 33402G can reach 25KHz, which is the fastest and widest bandwidth electronic load in the market
• The dimming control output of 3345G & 33402G is DC~10KHz (other models are DC~1kHz)

The measurement function of the ASR series AC/DC power supply can be performed through the free software to perform data logging (Data Logger)

The software diagram is as follows

Figure 1 Data logging of ASR measurement parameters

Figure 2 Harmonic data logging

For free software, please click the link below, file download option, registered members can download for free after login

https://www.gwinstek.com/en-global/products/detail/ASR-3000

The power supply over-voltage protection (OVP) is designed as a DUT protection mechanism to avoid supplying excessive voltage to the device under test (DUT) or circuit under test (DUC).

Three possible overvoltage (OVP) scenarios are provided below.

Scenario 1: Users forget that the overvoltage protection was set for the last project, and the voltage of this test project is higher than the overvoltage protection setting value.

For example: the OVP of the last project was set to 12.5V, the required voltage of this project is 15V, and the set output voltage is higher than the 12.5V of the overvoltage protection, so the power supply starts the protection mechanism to stop the output.

Scenario 2: After connecting the remote compensation, the output of the power supply is higher than the overvoltage protection setting value due to compensation

For example: the working voltage of the circuit is 12V, and the overvoltage protection is set to 12.5V. Due to the excessive loss from wiring, a voltage drop of 0.6V is caused on the wiring, resulting in only 11.4V voltage of the DUT. The power supply starts to compensate, and the compensation reaches 12.5V, the DUT is 11.9V, and the overvoltage setting value of 12.5V is exceeded after compensation, so the power supply starts the protection mechanism to stop the output.

Scenario 3: Due to the inductance of the test lead, at the moment of the power supply switching or the moment of the programmable voltage change, the stray components on the lead cause LC resonance, and the transient voltage during the voltage change exceeds the OVP protection voltage setting value.

In addition to installing the driver for the APS-1102A, your computer must also have NI-VISA installed.

During the production line test, the programmable DC power supply provides voltage, current, and test time. These three programmable variables enable the automation of complex production line test procedures. However, if you want to further improve the test capacity after automation, you must understand the design and special features of programmable power supply.

First, we need to understand the output characteristics and load effects of the DC power supply.

In order to provide a stable DC output, the DC power supply will have a capacitor at the output to perform the filtering work, and the capacitor does not allow the voltage to change instantaneously, so when you want to change the voltage output, the DC output filter capacitor will make this change a dilemma of application. The smaller the output ripple, the slower the response speed of the voltage change.

The output voltage should become larger: fast when no load, slow when loaded. Life scenario: A car full of passengers and an empty car climb a hill. Under the same throttle condition, the empty car climbs quickly, and the fully loaded car climbs slowly.

The output voltage should be smaller: slow when no load, fast when loaded. Life scenario: a car full of passengers and an empty car go downhill. When the accelerator is not stepped on, the empty car goes downhill slowly, and the full load goes downhill fast. When the power supply provides the function of the bleeder resistor, the voltage reduction time can be increased through the bleeder resistor.

If you need the power supply to perform rapid voltage changes (100u sec level), you can use the DC mode of the AC power supply, such as GW Instek ASR-2000 series, ASR-3000 series AC/DC dual-purpose power supplies.

If a rapid change in current is required, an electronic load can be used to extract the load, forcing the power supply to provide fast current.

In addition to the above issues, the setting time of the hardware and the computer control interface (GPIB, RS-232, USB, LAN) adopted will affect the time of the programmable voltage change.

Application Keywords: Rise Time, Fall Time