Most DC power supplies provide a set output voltage, referred to as CV mode (Constant Voltage). Describing it as "setting a fixed output voltage" best captures its overall purpose, where the output current varies depending on the load.

However, this changing current cannot exceed the power supply's maximum designed current (determined by application and price design goals) or maximum set current (to protect the circuit under test). Therefore, once the load current exceeds either of these values, the power supply's output switches from CV mode to CC mode. For example, take a DC power supply with a max designed voltage of 30V and a current of 3A: when the load does not exceed 3A, the power supply operates in CV mode, allowing the output voltage to be set from 0V to 30V. Assuming an output of 12V, as long as the load stays under 3A, the ideal output voltage remains fixed at 12V while the current varies according to the load.

Once the load exceeds 3A, since the power supply can only deliver up to 3A, it switches to CC mode, holding the current at 3A while the output voltage varies based on the load.

The biggest difference lies in how feedback energy is handled during testing. Standard DC power supplies are suitable for testing scenarios that only require stable power delivery; when the load generates feedback energy, it is typically dissipated as heat. Bi-directional DC power supplies are ideal for applications such as battery charging/discharging, high-power, or long-duration testing. When energy feedback is generated during testing, they can absorb the energy and recycle it back into the grid, reducing overall power consumption and thermal burden while helping improve testing efficiency.

Step 1: Check whether the AC input of the power supply is normal. Verify if a switched power strip was accidentally left off or turned off by a colleague without notice. Check if the power supply display is on; if not, check whether the power supply fuse is blown.

Step 2: After confirming the power input is normal, set the output voltage and current of the power supply—neither should be zero (pay special attention that current is not set to 0). If the set value fails to display, check if the Key Lock indicator is lit; if so, unlock it first.

Step 3: If the power supply has an output control switch, press the "On" button. Power supplies with an output control switch typically feature an indicator light showing that output is enabled.

Step 4: If the output control switch is on but the indicator light is off, use a multimeter's voltage range to measure the output of the power supply. If the power supply still has no output after performing these troubleshooting steps, please contact your nearest GW Instek service center.