1, in the switching power supply switching power supply pwm control chip , PWM control chip such as: uc3842 Switching power supply pwm control chip , read the output and input voltage and current feedback signal to adjust the PWM duty ratio. The PWM chip is usually selected with the following principles: The maximum output frequency of the chip: based on the PWM frequency and the output power of the power supply, the input voltage and other selection of the magnetic core and inductance. Therefore, the output frequency range of PWM is importantThe driving power of the output signal, of course, you can also increase the driving power with the peripheral circuit.
2, the switching power supply chip is an integrated circuit used to control the power switch. The working principle is to realize the switching and adjusting of the power supply by controlling the conduction and cutoff of the switching tube. When the input voltage is converted into the required output voltage through the transformer or DC-DC converter, the switching power supply chip will control the on-time of the switching tube according to the change of the output voltage, so as to achieve stable regulation of the output voltage.
3, pulse width modulation, with the square wave to drive the switch tube, when the IC outputThe switch tube is on at high normal times, and the output is off at low normal times. In this way, voltage can be generated in the transformer secondary.
4, UC3842 is a PWM control chip, often used in switching power supply control circuit. The working principle is as follows: The controller receives feedback signals: In the switching power supply, a feedback loop is usually formed through components such as inductors and capacitors, and the output voltage or current information is fed back to the controller. The UC3842 receives the feedback signal through an internal comparator and converts it into a digital signal.
5, the basic principle of pwm control is: the inverter circuitThe on-off of the switching device is controlled so that the output end gets a series of pulses with equal amplitude, and these pulses are used to replace the sine wave or the desired waveform. Several pulses are generated in half cycle of the output waveform, so that the equivalent voltage of each pulse is sinusoidal waveform, and the output is smooth and low harmonic is less.
6, the control mode is to control the on-off of the switching device of the inverter circuit, so that the output end gets a series of pulses with equal amplitude, and these pulses are used to replace the sine wave or the required waveform. That is, multiple pulses are generated in half a cycle of the output waveform, so that the equivalent voltage of each pulse is a sinusoidal waveform.What is it? '> What are the features of the Fp1451 chip?
Fp1451 is a pWM control chip, which has a wide range of applications in switching power supply and inverter circuits. The chip consists of reference voltage, oscillator, error amplifier, timer and pWM comparator circuits. The use of Fp1451 can be composed of a variety of switching power supply and control system, not only can make the switching power supply and control system simplified, easy maintenance, cost reduction, and more importantly, can reduce the failure rate of the system, improve the reliability of system equipment operation.
Roger structure drive circuitWhen combined with drive control ics (such as BIT3101A, BIT3102A, Fp145BA9741, etc.), an inverter circuit with brightness adjustment and protection functions can be formed.
1, the switching power supply chip is an integrated circuit used to control the power switch. The working principle is to realize the switching and adjusting of the power supply by controlling the conduction and cutoff of the switching tube. When the input voltage is converted to the desired output voltage by a transformer or DC-DC converterWhen Switching power supply pwm control chip , the switching power supply chip will control the switching tube turn-on time according to the change of output voltage Switching power supply pwm control chip , so as to achieve stable regulation of the output voltage.
2, the working principle of the switching power supply control chip r7731 Switching power supply pwm control chip : the VDD pin of the chip is connected to a capacitor to the ground Switching power supply pwm control chip , a resistor to the positive input voltage, the input voltage through the resistor to charge the capacitor, when the capacitor voltage charged to the chip starting voltage threshold, the chip starts to work.
3, UC3842 is a PWM control chip, often used in switching power supply control circuit. The working principle is as follows: Switching power supply pwm control chip : The controller receives feedback signals: In the switching power supply, a feedback loop is usually formed through components such as inductors and capacitors, and the output voltage or current information is fed back to the controller. UC3842The feedback signal is received through an internal comparator and converted into a digital signal.
4, switching power supply is mainly the use of modern power electronics technology, by controlling the turn-on and turn-off time ratio of electronic switching devices, to maintain the stability of the output voltage. Generally composed of PWM (pulse width modulation) control IC and MOSFET, it has the characteristics of small size, light weight, low power and high efficiency.
5, when the output is high voltage, the TL431 output high level, so that the current flowing through PC817 increases, so that the degree of light emitting diode inside it increasesThe degree of conduction of the photosensitive transistor is increased, and the feedback is sent to the corresponding pin of the core piece, so that the core piece stops opening, and the output of low voltage is conversely, the result is to increase the pulse width; This is subedge-feedback; Of course, there are also some primitive side feedback, like control theory, not detailed.
2, circuit design and principle 1 UC3842 Working principle of uc3842UC3842 is a single power supply, with current forward compensation, single-channel modulation output integrated chip, its internal composition diagram is shown in Figure l. Pin 1 is connected with an external resistance-capacitance element to compensate the frequency characteristics of the error amplifier. Pin 2 is the feedback voltage input, the sampling voltage is added to the inverting input of the error amplifier, and then compared with the reference voltage of the in-phase input to generate the error voltage.
3, UC3842 working principle: the power supply part of the circuit uses single-ended pulse width modulation switching power supply, pulse width modulation IC uses UC3842UC3842 is a kind ofThe current type pulse width controller, which can directly drive MOS tube, IGBT, etc., is suitable for making single-ended circuits.
4, the switching power supply using uc3842 series chips is a lot, and the analysis is similar to the original tl494 series chips. High-frequency filtering, power frequency rectification, high-frequency conversion, high-frequency rectification, output filtering, these parts are basically the same. The key is the difference in pulse width on the integrated circuit. Here, we must first know the role of each foot of the chip used, chip parameters and basic principles.
5, the circuit structure and working principle is shown in Figure 2 of the author's actual workMake the circuit diagram used in. The input voltage is 24V DC. Three DC outputs, respectively 5V/4A, 12V/0.3A and -12V/0.3A. All diodes use fast reaction diodes, and the core PWM device uses UC3842. The switching tube adopts fast high-power field effect tube.