I. Introduction
An adjustable power supply is a type of power supply that can adjust its voltage and current within a certain range, and it is widely used in various electronic devices. However, sometimes we need to reduce the voltage to increase the current output, and this operation requires changing the parameters of the adjustable power supply circuit. This article will introduce how to increase the current output of an adjustable power supply.
II. Methods to increase the current of adjustable power supplies
1. Increase the output resistance
Changing the output resistance of an adjustable power supply can alter the current output; generally, the smaller the output resistance, the larger the current output. Therefore, adding a parallel resistor or decreasing the resistance value in the circuit can increase the current output. It's important to note that changing the resistance in the circuit may also affect the output voltage of the adjustable power supply, so proper matching of circuit parameters is necessary.
2. Increase the power transistor parameters
Power transistors are crucial components in adjustable power supplies, and changing their parameters can increase current output. This can be achieved by increasing the transistor's on-state current or setting a higher operating voltage, but it's essential to be mindful of the transistor's maximum power load capacity and avoid exceeding it.
3. Increase the power input voltage
Increasing the power input voltage can increase the current output of an adjustable power supply, but care must be taken not to exceed the maximum withstand voltage of the circuit components to prevent damage to the components.
III. Points to Note
1. Before changing the circuit parameters, be sure to understand the circuit structure of the adjustable power supply in detail to ensure that the circuit after the change is stable.
2. Changing circuit parameters can affect other performance indicators of the adjustable power supply. Therefore, it is necessary to test the parameters in actual applications to avoid affecting the operation of other circuit components.
3. Exercise extreme caution when adjusting circuit parameters to avoid damaging circuit components and posing a danger to the user.
IV. Conclusion
This article introduces three methods for increasing the output current of an adjustable power supply and points out some precautions. It is hoped that this will be helpful to everyone. In practical applications, trade-offs and adjustments need to be made based on specific requirements and circuit structure to obtain optimal circuit performance.
When using an adjustable DC power supply with constant voltage or constant current, no current will be output if no load is connected. When using an adjustable DC power supply, the DC voltage should first be set to an approximate value based on the rated voltage of the load. In most cases, this adjustable DC voltage is used to change the voltage, and changing the DC voltage will also change the current within a certain range.
According to Ohm's law I=U/R, there is also a range for fine-tuning the current.
The problem likely concerns so-called constant voltage and constant current sources, which can be adjusted based on current and voltage. However, the output voltage and output current must be set separately.
For example, we want to set the output to 12.6V 1.8A:
During operation, please first turn on the power switch and test the no-load voltage. The digital display and two buttons are used to display and adjust the output voltage value. One of the two knobs is for coarse setting, and the other is for fine adjustment. Rotating both knobs should allow the voltage to change continuously from 0 to the maximum value. After confirming that the voltage regulation function is normal, you can adjust the current in the next step.
When adjusting the current, the output terminals must be short-circuited. To avoid power supply failure, first reduce the voltage to approximately 2V (but not to 0V, otherwise no current will be output), then short-circuit the power supply's output terminals. At this point, the voltmeter reading will drop sharply, approaching zero volts, and the ammeter will display the current value. Then, adjust the current to 1.8A using the two current regulators on the right. Next, disconnect the positive and negative terminals of the output connector to end the short-circuit state. At this point, the current will disappear, and the voltage will return to its pre-adjustment state.
The next step in adjusting the tension is relatively simple. Just adjust the two rotary knobs to set the voltage to 12.6V.
If the current and voltage still cannot be adjusted after following the above steps, it indicates a power supply malfunction. Excessive wear of the potentiometer is common and can be resolved by replacing it with a component of the same specification. If other errors exist, it becomes more complex and can only be analyzed on a case-by-case basis.
To clarify, this type of power supply has the capability to achieve either constant current or constant voltage. This is not a malfunction of the power supply itself, but rather determined by Ohm's Law. For example, with the 12.6V and 1.8A listed above, when the load connected to the power supply is low and the current does not reach 1.8A, the power supply output is in a constant voltage state. The voltage remains constant from 0 to 1.8A and 12.6V, and the current varies with the load, but a constant current cannot be achieved.
If we want to further increase the output voltage, you'll find that the voltage cannot be increased when the current reaches 1.8A. This is because the power supply enters a constant current state at this point.
However, as the charging power increases, the current will exceed 1.8A, for example, greater than or equal to 1.8A. 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 shows that it is impossible to obtain constant current and constant voltage simultaneously. When the current is constant, the voltage is not constant, and when the voltage is constant, the current is not constant.
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.
Gisele Electronics (Suzhou) Co., Ltd. specializes in the research and application of power electronic conversion technology. We are a professional manufacturer and solution provider of products including frequency converters, DC power supplies, AC loads, DC loads, regenerative electronic loads, regenerative grid simulators, battery simulators, charging pile test loads, photovoltaic inverter testing equipment, new energy motor and electronic control test power supplies, and automated testing systems. We are a high-tech enterprise in China's power supply industry and a leader in core technology automation for testing systems. How to adjust the voltage in a switching power supply?
Switching power supplies are among the most commonly used power supplies in electronic devices. Unlike traditional power supplies, they employ switching circuits to control the flow of current. Switching power supplies not only achieve high-efficiency output but also offer advantages such as energy saving, small size, light weight, and long lifespan. They are widely used in various electronic devices, including computers, mobile phones, tablets, cameras, and audio equipment.
The output voltage of a switching power supply is adjusted based on the source voltage and the load. In most cases, the output voltage of a switching power supply needs to be adjusted to meet the requirements of different types of loads. This article will introduce how to adjust the voltage of a switching power supply, including its working principle, voltage adjustment methods, and precautions for voltage adjustment.
I. Working principle of switching power supply
Switching power supplies intermittently convert direct current (DC) into high-frequency alternating current (AC), then use a high-frequency transformer to increase or decrease the voltage, and finally use a rectifier circuit to convert it back into stable, clean DC. Switching power supplies are typically designed with microprocessor control circuits to achieve precise and efficient voltage and current regulation. When the power supply is in normal operating condition, the microprocessor monitors parameters such as the power supply's operating voltage, current, and power, and then automatically adjusts the output current and voltage based on the monitoring results.
II. Voltage Regulation Methods for Switching Power Supplies
1. Converter Design
A converter is a key component of a switching power supply, used to convert input direct current (DC) into output alternating current (AC). Depending on its type and design, a converter typically performs voltage transformation and regulation. Transformer design is one of the most common voltage regulation methods used in switching power supplies. A transformer raises or lowers the voltage by changing the turns ratio of the input and output coils. Furthermore, transformers can be used to address magnetic coupling and voltage stability issues, improving the overall stability and reliability of the power supply.
2. Step-down circuit
A buck converter reduces the input voltage to a required level to meet the needs of low-voltage loads. Common buck converters include linear buck converters and nonlinear buck converters. Linear buck converters use passive components such as resistors and capacitors to reduce voltage, while nonlinear buck converters use power semiconductor devices such as MOSFETs and IGBTs to achieve both voltage reduction and power dissipation, while simultaneously improving power conversion efficiency and load capacity.
