The power supply module is the core component that provides power output. It can achieve adjustable output by controlling the output voltage and current. Common power supply modules include switching power supplies and linear regulated power supplies.
The voltage measurement module is used to accurately measure the voltage output of the power supply. It typically uses an analog-to-digital converter (ADC) to convert the analog voltage signal into a digital signal for processing by a microcontroller.
Current measurement modules are used to accurately measure the current output by the power supply. Common measurement methods include the resistance method and the Hall effect.
The control module uses a microcontroller to control and regulate the power supply. Based on measured voltage and current signals, and user-defined parameters, the microcontroller controls the power supply module's operating state to achieve programmable functionality.
Finally, carefully review the instruction manual and technical documentation of the digital programmable frequency converter. Understand the equipment's characteristics, functions, and operating methods to fully utilize its performance. If you encounter any difficulties operating the equipment or problems, contact the manufacturer or seek assistance from a professional.
In summary, the correct and safe use of digital programmable frequency converters requires attention to input power conditions, understanding output capabilities, proper equipment connection, reasonable parameter settings, continuous monitoring of operating status, adherence to safe operation, and thorough understanding of the equipment's instruction manual and technical documentation. Only in this way can we ensure the reliable operation of the digital programmable frequency converter and provide stable power support for our industrial production and research work. A programmable power supply is a power system capable of providing adjustable voltage and current output, and it has wide applications in engineering design, scientific research experiments, and other fields. This article will introduce how to implement a programmable power supply system design using a microcontroller and discuss related key technologies and design considerations.
When assessing reliability, a common starting point is determining the level of protection that ensures the system is protected in the event of any unexpected operating conditions. A fuse is clearly a simple implementation to prevent short circuits in overcurrent protection schemes. However, we must consider how to restore the system to the field after the fuse blows in a short-circuit situation. Operational downtime is costly and, in many cases, unacceptable. A fuse provides only two pieces of information: whether the current is excessive and whether the system power bus is open.
Circuits that actively measure system current can detect out-of-range conditions with great precision and allow for adjustments to operating performance to achieve safe operation at full power budget without sacrificing reliability.
The INA199 shunt monitor is a common building block for this function because of its small printed circuit board (PCB) footprint, high precision, and integrated matching gain setting resistor.
The INA199 series of voltage-output, current-shunt monitors (also known as current-sense amplifiers) are commonly used for overcurrent protection, precision current measurement for system optimization, or closed-loop feedback circuits. This series of devices can sense a voltage drop across a shunt resistor from -0.3 V to 26 V common-mode voltages, independent of the supply voltage. Three fixed gains are available: 50 V/V, 100 V/V, and 200 V/V. The low offset of the zero-drift construction allows the maximum voltage drop across the shunt to be as low as 10 mV at full scale. These devices operate from a single 2.7-V to 26-V supply and can draw a maximum supply current of 100 μA. All versions are specified for a temperature range of -40°C to 125°C and are available in SC70-6 and thin UQFN-10 packages.
●Features
■ Wide common-mode range: –0.3 V to 26 V
■ Offset voltage: ±150μV (maximum) (allows shunt voltage drop to reach 10 mV full scale)
■Accuracy:
▲–Gain Error (Maximum Over-Temperature):
▲–±1% (Version C)
▲–±1.5% (Type A and Type B)
▲–0.5-μV/°C offset drift (maximum value)
▲–10 ppm/°C gain drift (maximum) gain selection:
▲–INA199x1:50 V/V
▲–INA199x2:100 V/V
The output is directed to a comparator with a fixed threshold that corresponds to the current level that the function block wants to detect.
INA199 shunt monitor in typical applications
The comparator output can directly control the circuitry to turn on the power bus, or allow the microcontroller to adjust system performance and continue operating within the permissible power budget, or completely shut down the system. For severe faults, this shutdown function is crucial to prevent damage to system components from out-of-range conditions.
The current-limiting threshold of this circuit is set by the reference voltage applied to the non-inverting input of the comparator. This voltage level directly corresponds to the current level measured by the INA199. Using a voltage divider, we can calculate the reference voltage using Equation 1:
Limiting reference voltage = Current limit (A) * Shunt resistor (Ω) * Amplifier gain (V/V) (1)
The INA300 is a dedicated current-sensing comparator that achieves the same function in a slightly different way by integrating a current-sensing amplifier and a comparator into a single device. Figure 2 shows a typical application of this comparator. The approach is the same as the previous example using the INA199, except that the INA300 uses a single external resistor to set the threshold limit, which corresponds to the system's current limit.
INA300 Current Sensing Comparator Block Diagram
An internal 20µA current source is present on the limiting pin, which creates a reference voltage for the comparator based on the value of the R LIMIT resistor connected to this pin. This voltage is set to be equal to the voltage generated across the shunt resistor at the current-limiting level. Formula 2 calculates the R LIMIT resistor value:
(2)
I hope we are now familiar with how the INA199 and INA300 devices can more effectively detect and handle overcurrent events.
DC/DC power supply circuits have the advantages of low power consumption and high power, but at the same time, since the DC/DC conversion is completed through switching, noise is inevitably introduced, specifically the ripple and noise of the power supply circuit.
1.
Compared with linear power supplies, the most prominent advantage of switching power supplies (including AC/DC converters, DC/DC converters, AC/DC modules, and DC/DC modules) is their high conversion efficiency, which can generally reach 80% to 85%, and can even reach 90% to 97%.
Secondly, switching power supplies use high-frequency transformers instead of bulky power frequency transformers, which not only reduces weight but also size, thus expanding their application range.
However, the disadvantage of switching power supplies is that because their switching transistors operate in a high-frequency switching state, the output ripple and noise voltage are relatively large, generally around 1% of the output voltage (as low as around 0.5% of the output voltage), and even the best products have ripple and noise voltages of tens of mV;
The regulating transistor of a linear power supply operates in a linear state, with no ripple voltage and relatively low output noise voltage, measured in μV.
2. Ripple and noise
noise:
definition:
Ripple: refers to the fluctuations in the output voltage of a power supply caused by periodic changes. It is commonly used to describe periodic changes in the output waveform of a power supply, especially in DC power supplies where the output voltage is not perfectly stable and exhibits certain periodic fluctuations.
The low-frequency components in power supply fluctuations are generally below 5MHz, and are caused by the switching action of MOSFETs.
Noise is an unwanted, random electrical signal that includes various disturbances and random variations introduced into a system. Noise can be caused by instabilities in electronic components, circuits, the external environment, etc.
The high-frequency components in power supply fluctuations are generally higher than 5MHz and are quite complex, typically including MOSFET switching noise, white noise, and interference from surrounding signals.
Causes:
Ripple: Voltage fluctuations mainly caused by factors such as power supply design, switching operation, and inductor and capacitor components.
Noise can come from various factors such as internal thermal noise of electronic components, environmental interference, and electromagnetic interference.
Periodicity:
Ripple: It has obvious periodicity and is a regular fluctuation that appears in the power supply output.
