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what mosfet should i use if the my firing ic is 38448
@copilot what mosfet should i use if the my firing ic is 38448
2y
what resistor value will be if the applied voltage is 600v DC and my mosfet ic is uc3844ad and mosfet is irf840
2y
what input supply need for ic uc3844ad if my output desire is 15v
2y
what components required for a ic uc3844ad i want output from ic of 15v then which components need
2y
Based on your reference to a "firing IC" and the number "38448," it seems there might be a bit of confusion or typo with the IC part number. However, given the context and the components listed in your project, it seems like you might be referring to the UC3844AD8 IC, a PWM controller. Assuming that's the case and you're looking to choose an appropriate MOSFET that will be driven by this IC or similar controllers in your application, here are some considerations and recommendations for selecting a suitable MOSFET:
Considerations
-
Voltage Rating (Vds): The MOSFET's drain-source voltage rating should be higher than the maximum voltage it will experience in your application. A good rule of thumb is to choose a MOSFET with at least 1.5 to 2 times the maximum expected voltage.
-
Current Rating (Id): Ensure the MOSFET can handle the maximum current it will carry. Like the voltage rating, it's wise to select a MOSFET with a current rating of at least 1.5 to 2 times the maximum expected current.
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Gate Drive Voltage (Vgs): The UC3844AD8 operates with a maximum output voltage (Vout) typically tied to its supply voltage. Make sure the MOSFET's gate can be fully enhanced with this voltage.
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Rds(on): Look for a MOSFET with a low on-resistance to minimize power losses in the switch.
-
Switching Speed: Given this is for a switching application, a MOSFET with fast turn-on and turn-off times would be more efficient.
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Package: Ensure the MOSFET’s package suits your heat dissipation requirements and PCB layout.
Assuming a typical application voltage of up to 400V and a moderate current level, I would suggest considering these MOSFETs:
- IRF840:
- Vds = 500V
- Id = 8A
- Rds(on) = 0.85Ω
- Vgs(max) = ±20V
This MOSFET is a common choice for high voltage applications, suitable for switching applications with moderate currents.
- STP10NK80ZFP:
- Vds = 800V
- Id = 10A
- Rds(on) = 0.75Ω
- Vgs(max) = ±30V
This component provides higher voltage and current ratings, making it a safer bet for higher power applications.
Please note, these are just broad recommendations based on typical use cases. I made a few assumptions about your application's voltage and current requirements. If your application has specific needs or if there were any misunderstandings about the part number, please provide more details for a more tailored suggestion.
2y
To calculate the appropriate resistor value for controlling a MOSFET gate in a circuit with a 600V DC supply and using a UC3844AD PWM controller to drive an IRF840 MOSFET, we need to consider a few key factors related to the UC3844AD, the MOSFET, and the overall circuit design parameters.
Considerations:
-
UC3844AD Characteristics: The UC3844AD is a fixed-frequency current-mode PWM controller. It typically operates with a gate-drive voltage in the range of 10V to 20V for MOSFETs. The actual output voltage to drive the gate will depend on the Vcc provided to the IC.
-
IRF840 Characteristics:
- Gate Threshold Voltage ((V_{GS(th)})): The voltage at which the MOSFET begins to turn on. For IRF840, this is typically around 2V to 4V.
- Maximum Gate-Source Voltage ((V_{GS(max)})): The maximum voltage that can be safely applied between the gate and source. For the IRF840, this is typically ±20V.
- Gate Charge ((Q_g)): Total charge required to switch the MOSFET on. This influences the resistor value to balance switching speed and efficiency.
-
Gate Resistor Purpose: The gate resistor ((R_g)) is used to limit the inrush current into the MOSFET's gate capacitance during switching, which helps to control the switching speed and mitigate electromagnetic interference (EMI). Too low of a value can lead to high inrush currents and potential damage or EMI issues, while too high of a value can slow down the switching speed, leading to increased power dissipation in the MOSFET.
For efficient switching without causing excessive delay or power dissipation in the MOSFET, let's assume a desired gate drive voltage of 15V (a common gate drive voltage for many applications) and a gate resistor connected between the UC3844AD output and the gate of the IRF840.
However, given that the power supply voltage is 600V DC and does not directly relate to the gate drive circuit of the MOSFET (since the UC3844AD would typically step down this voltage to a suitable level for the gate drive), the main consideration for selecting a gate resistor is based on the IC's output characteristics and MOSFET's gate charge.
Absent specific details on the IC's gate drive capability or the circuit's design that would involve the 600V DC directly in determining the gate resistor, a typical approach to driving a MOSFET like the IRF840 from a PWM IC like the UC3844AD would involve considering the drive current capability of the UC3844AD and the charging and discharging requirements for the IRF840’s gate capacitance to ensure proper switching without causing too much delay.
Without specific details on the UC3844AD's output drive current limit or the desired switching speeds, it's challenging to provide a precise resistor value.
General Recommendation:
- For such applications, gate resistor values typically range from 10Ω to 100Ω. A lower value within this range is chosen for faster switching applications at the risk of higher EMI, while a higher value would slow down switching but potentially offer better EMI performance and protect the IC's output stage from the high inrush current associated with charging the gate capacitance.
For your specific application, it might be advisable to start with a mid-range value (e.g., 47Ω) and adjust based on the desired switching speed and observed drive performance. Always consult datasheets and application notes for both the UC3844AD and the IRF840 for guidance on optimal drive strategies and to ensure the selected resistor value meets your application's requirements.
2y
To calculate the appropriate resistor value for controlling an IRF840 MOSFET gate in a circuit using a UC3844AD PWM controller, with an applied voltage of 600V DC, it's important to clarify that the resistor in question likely refers to a gate resistor. This resistor is critical for controlling the gate charge and discharge times, mitigating excessive ringing, and preventing damage from high inrush currents. However, the 600V DC applied voltage is mostly relevant to the MOSFET's drain-source voltage rating and not directly to the gate drive circuit unless specifically used for a high-side drive configuration, which involves additional considerations.
Assuming a simple low-side driver configuration, where the PWM controller directly drives the MOSFET gate with respect to the ground, the resistor value would primarily depend on the gate charge of the MOSFET, the desired switching speed, and the drive capability of the UC3844AD. Unfortunately, without direct gate charge ((Q_g)) information for the IRF840 and specific drive current capability for the UC3844AD from the provided excerpts, an exact calculation can't be performed. However, I can provide a generalized approach to determine a starting point for this resistor value.
Generalized Calculation Approach:
-
Max Drive Current ((I_{drive})) of UC3844AD: Typically, the output drive capability of PWM controllers like the UC3844AD influences the resistor value. For a theoretical maximum drive current (not specified), you would adjust the resistor value to limit peak current into the MOSFET gate capacitance.
-
Gate Charge ((Q_g)) of IRF840: This specifies how much charge is needed to switch the MOSFET. Without specific (Q_g) values, we can't calculate the exact time ((t)) to charge the gate but know it impacts resistor choice.
-
Switching Speed Requirements: Faster switching requires lower resistor values to allow quicker charging and discharging of the gate. However, too low may cause overshooting or ringing.
Given these points, if we were aiming for a certain drive current ((I_{drive})) and had a known gate-to-source voltage ((V_{GS})) we wished to achieve to fully turn on the MOSFET (e.g., 10V for IRF840), we could estimate a resistor value using Ohm's Law:
Rg=IdriveVdrive−VGS
Where:
- (R_g) is the gate resistor,
- (V_{drive}) is the output voltage of UC3844AD (assuming 15V for calculation purposes),
- (V_{GS}) is the target gate-source voltage for the MOSFET,
- (I_{drive}) is the assumed current limit of the UC3844AD's output.
Without specific (I_{drive}) and (Q_g), a common practice for designing with unknown drive current capabilities and gate charges is to start with a resistor in the ballpark of 10Ω to 100Ω. You can then adjust based on observed switching performance and thermal behavior of the MOSFET. It is also important to ensure that the resistor does not slow down the switching speed excessively, increasing switching losses, or allow too fast switching that might cause damage due to voltage spikes from parasitic inductances.
For accurate optimization, refer to the specific datasheets for the UC3844AD and IRF840, considering the gate charge, desired switching frequency, and any recommendations on gate resistance for driving conditions. Testing with an adjustable resistor or a series of different fixed resistors could help fine-tune the performance based on your specific requirements.
2y
To determine the input supply necessary for the UC3844AD8 IC when your desired output is 15V, it's important to consider the IC's characteristics and functionality. The UC3844AD8 is a current-mode PWM controller, often used in switch-mode power supplies (SMPS) and DC-DC converters. It does not directly regulate output voltage but rather controls a switching power stage that, in turn, determines the output voltage based on feedback and the components used in the design.
Key Considerations:
-
VCC Range: The UC3844AD8 typically requires a bias voltage (VCC) to function. This VCC not only powers the IC but is also involved in the gate drive for the external MOSFET or transistor. The range for VCC is generally from about 10V to 30V for many PWM controllers like the UC3844AD8. For efficient operation and to ensure the IC's internal circuits are adequately powered, the lower end of this range can be considered as the minimum required input supply voltage.
-
Start-Up Voltage: The UC3844AD8 has an under-voltage lockout feature that dictates the minimum voltage at which the IC starts operating. This start-up voltage is slightly higher than the minimum operating voltage to ensure stable operation upon start-up.
-
Headroom for Regulation: Providing some headroom above the minimum VCC allows for better performance and ensures the controller operates effectively across varying conditions.
Given these considerations and without specific details from the UC3844AD8's datasheet excerpts in the provided information, a general advice would be to supply the UC3844AD8 with an input voltage slightly above its minimum operating voltage to ensure robust operation. A typical input supply for such ICs, aiming for a 15V output in a DC-DC converter application, could start at around 12V but might be higher based on the specific topology of your power supply and the efficiency of the step-down conversion process.
For a precise value and to ensure optimal performance, always refer to the specific IC's datasheet for details on the recommended operating conditions, start-up voltage, and maximum VCC. Since the desired output is 15V, the input supply must be chosen considering the overhead required for efficient conversion, including any potential voltage drops in the power path and the efficiency of the chosen power conversion topology (e.g., Buck, Boost, or Flyback converter).
Without direct excerpts specifying the UC3844AD8's input supply requirements or under-voltage lockout characteristics, this response assumes typical values for similar PWM controllers. If you have more detailed requirements or need assistance with a specific power supply design using the UC3844AD8, including component selection and circuit topology, please provide more details.
2y
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Reviews
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