I. Methods for Adjusting Current
Adjustable power supplies are essential tools for circuit testing and experimentation, primarily used to control the voltage and current of a load. In practical applications, it is sometimes necessary to adjust the current, which requires understanding the relevant knowledge about adjusting the current of an adjustable power supply. The following are methods for adjusting the current of an adjustable power supply:
1. Knob Adjustment Method: Adjustable power supplies usually come with a current limiting knob. First, set the knob to the minimum current value, then connect the power supply output to the circuit under test. Gradually rotate the knob and observe the behavior of the circuit. When the current reaches the expected value, stop rotating the knob.
2. Fast Response Method: This method is suitable for applications requiring high current response speed. Adjustable power supplies are equipped with a fast current response switch. This switch can be turned on first, and then the current limiting knob can be gradually rotated to quickly adjust the current value.
II. Precautions
When using an adjustable power supply, the following precautions should be taken:
1. To ensure stability: When adjusting the current, it is necessary to ensure that the output current of the power supply remains stable at all times.
2. Avoid power supply overload: When adjusting the current, be sure to pay attention to the rated output current value of the power supply and do not exceed the load it can withstand.
3. Pay attention to voltage before testing: Before testing, check the voltage value of the circuit under test. If the voltage value is too high, reduce the voltage value of the test circuit before performing the current test.
4. Protect the circuit: During the test, care should be taken to protect the circuit under test to avoid overcurrent or short circuit.
5. Exercise caution during debugging: During the debugging process, the current value should be adjusted slowly and gradually to avoid damage caused by excessive current.
An adjustable power supply is a power device capable of providing stable output voltage and current. Its current regulation is achieved through a series of electronic circuits and control algorithms. The principle of an adjustable power supply is to adjust the output voltage or current by changing the output voltage or current. Specifically, an adjustable power supply typically contains a control circuit that adjusts the output voltage or current based on a set adjustment signal or feedback signal. The control circuit can use various techniques and algorithms to achieve regulation, such as pulse width modulation (PWM) and pulse frequency modulation (PFM).
The output voltage or current of an adjustable power supply can be controlled by an external regulator or microcontroller. The regulator or microcontroller can set a target voltage or current value and compare it with the actual output voltage or current. Based on the comparison result, the regulator or microcontroller outputs a control signal that adjusts the output voltage or current of the adjustable power supply to achieve the target value.
In addition, adjustable power supplies may include protection circuits such as overcurrent protection and overvoltage protection to ensure the safety of the power supply and the powered equipment. When the output current or voltage of the power supply exceeds the safe range, the protection circuit will trigger the corresponding protection mechanism, such as cutting off the power supply output or reducing the output voltage, to prevent damage to the equipment caused by excessive current or voltage.
The current regulation of an adjustable power supply can be mainly divided into the following steps:
1. Input Signal Acquisition: The current regulation system of an adjustable power supply first needs to acquire the output current signal of the power supply through an acquisition circuit. These signals can be analog or digital, depending on the design and implementation of the adjustable power supply.
2. Signal Processing: The acquired current signal will be processed by signal processing circuitry, including operations such as amplification, filtering, and comparison. This processing is a preliminary step to facilitate subsequent adjustment and control.
3. Adjustment Circuit: The adjustment circuit is the core component of the adjustable power supply. It compares the acquired current signal with a preset reference value and generates an adjustment signal. The adjustment signal is usually a control voltage or control current used to control the output current of the adjustable power supply.
4. Power Device Control: The power devices (such as transistors and MOSFETs) in an adjustable power supply are used to control the output current. The regulating signal generated by the regulating circuit adjusts the output current by controlling the switching state of the power devices. Specifically, the regulating signal controls the on and off times of the power devices, thereby changing the magnitude of the output current.
5. Feedback Control Loop: Adjustable power supplies typically include a feedback control loop for real-time monitoring and regulation of the output current. This loop can be either an open-loop or closed-loop control system, chosen based on specific application requirements. In an open-loop control system, the regulating signal directly controls the output current; in a closed-loop control system, the regulating signal is adjusted in real-time based on the feedback output current to ensure stability and accuracy of the output current.
6. Protection Circuits: To protect the adjustable power supply and the powered equipment, the adjustable power supply usually includes some protection circuits (such as overcurrent protection, overvoltage protection, etc.). When the output current exceeds the preset safe range, the protection circuit will trigger the corresponding protection mechanism, such as cutting off the switching state of the power device or reducing the output voltage, to prevent damage to the equipment caused by excessive current or voltage.
In summary, the current regulation of an adjustable power supply is achieved through multiple stages, including acquiring the output current signal, processing the signal, comparison and adjustment, controlling the switching state of power devices, feedback control, and protection circuits. These stages work together to ensure that the adjustable power supply can provide a stable and reliable output current to meet the needs of various application scenarios. In practical applications, it is necessary to select a suitable adjustable power supply based on specific requirements, considering its performance parameters, accuracy, stability, and other requirements. Furthermore, it is essential to pay attention to the operating environment and conditions of the adjustable power supply, and to comply with relevant safety regulations and operating procedures to ensure its normal operation and safety.
As charging power increases, the current will exceed 1.8A, for example, greater than or equal to 1.8A. This is achieved by connecting a high-performance 6Ω resistor. According to Ohm's law U/R = 1, 12.6 V ÷ 6Ω = 2.1 A. Since the current is set to 1.8 A, the power supply's output voltage becomes active at 10.8 V (1.8 A × 6Ω). This is reduced to meet the set current requirement. This demonstrates that it is impossible to obtain both constant current and constant voltage simultaneously. When the current is constant, the voltage is not constant, and vice versa.
This constant current function is very useful when measuring LED light sources. For example, when measuring a 1W LED chip, the current can be set to 0.3A and the voltage to 4-5V (slightly above VF). If the voltmeter reading is 3.25V, this is the VF value of the LED chip. It is convenient to classify and filter light sources or LED chips.
When the 220V power supply is normal, zero current indicates a power supply fault. Often, a long adjustment time for an adjustable potentiometer can cause poor contact. In this case, replace it with a new one. If the problem persists, the voltage regulator is faulty, and the voltage stabilizing circuit needs adjustment.
Jishili Electronics (Suzhou) Co., Ltd. is dedicated to the research and application of power electronic conversion technology. It is a professional manufacturer and solution provider of products such as frequency converters, DC power supplies, AC loads, DC loads, regenerative electronic loads, regenerative grid simulators, battery simulators, charging pile test loads, photovoltaic inverter test equipment, new energy motor and electronic control test power supplies and automated test systems. It is a high-tech enterprise in China with core technologies in power supply and test system automation.
