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Fiber Optic Media Coverters Control Type

Aifon Technology Co.,Ltd | Updated: Jul 11, 2017

Voltage mode and current mode are two types of control commonly used in switching power supply systems. Fiber Optic Media Coverters In the switching power supply system, when the input voltage changes, Fiber Optic Media Coverters the output load changes and changes in the internal parameters of the power supply, the control circuit will detect the controlled voltage and current signals, compare them with the reference signal, and then amplify the difference, Feedback control to adjust the main circuit power device conduction pulse width or switching frequency, Fiber Optic Media Coverters thus ensuring the system output voltage or output current and other adjustable signal stability.

Switching power supply with PFM and PWM two control methods: PFM work in the frequency mode, by adjusting the operating frequency to maintain the output voltage or output current constant. PWM operates at a fixed frequency, by adjusting the pulse width, that is, duty cycle, to maintain the output voltage or output current constant. In the power supply system, the voltage sampling signal has an input voltage and an output voltage, Fiber Optic Media Coverters while the current sampling has a power inductor DC voltage drop, the current sampling resistor voltage and the power MOSFET conduction voltage drop, etc. These signals can constitute a single ring, Fiber Optic Media Coverters Double loop or multi-loop feedback system to achieve regulation, steady flow or constant power control, and can achieve overvoltage undervoltage protection, overcurrent protection, current sharing, Fiber Optic Media Coverters output voltage sequencing tracking and other functions.

Voltage mode control system. The control loop has only one voltage feedback loop, and the voltage feedback loop includes a voltage error amplifier, a feedback divider resistor, Fiber Optic Media Coverters and a feedback compensation network. The phase difference of the voltage error amplifier is connected to the reference voltage Vref, the feedback divider resistor is connected to the inverting terminal FB of the voltage error amplifier, the feedback compensation network is connected to the output terminal COMP of the inverting terminal FB and the voltage error amplifier COMP, The voltage is Vc. The output of the voltage error amplifier is connected to the inverting terminal of the PWM comparator. Fiber Optic Media Coverters The input terminal of the PWM comparator is the continuous sawtooth output from the ramp generator and is generated by the clock synchronization signal

 The voltage mode of the work process has two stages:

(1) clock oscillator output pulse signal is high, high-end switch tube conduction, start a switching cycle, the inductance of the voltage is positive, Fiber Optic Media Coverters inductance excitation, the current linear rise. Since the voltage of the sawtooth wave is lower than the voltage of Vc, Fiber Optic Media Coverters the PWM comparator outputs a low voltage.

(2) When the voltage of the sawtooth wave increases to a voltage higher than Vc, the PWM comparator output is turned on, the high-side switch is turned off, the low-side synchronous MOSFET or freewheeling diode is turned on, Fiber Optic Media Coverters the voltage applied to the inductor is negative, Fiber Optic Media Coverters Inductance demagnetization, current linearity. Until the next switch cycle starts the clock synchronization signal arrives, so repeatedly.

There are two ways to improve the voltage mode control transient response speed: First, increase the bandwidth of the voltage error amplifier to ensure a certain high-frequency gain, Fiber Optic Media Coverters but it is susceptible to high-frequency switching noise interference, Fiber Optic Media Coverters the need for the main circuit and feedback control circuit Take measures to perform suppression or phase attenuation smoothing. Another method is the use of voltage feedforward technology, with the input voltage on the resistance and capacitance charge generated with a variable slope of the triangular wave, replace the traditional voltage mode PWM controller oscillator generated by the fixed triangular wave. At this time, the input voltage changes can be reflected immediately in the change of the pulse width, so the method of the input voltage changes caused by the transient response speed was significantly improved. The feedforward control of the input voltage is open-loop control, Fiber Optic Media Coverters while the control of the output voltage is closed-loop control, Fiber Optic Media Coverters the purpose is to increase the input voltage changes in the dynamic response speed, Fiber Optic Media Coverters thus forming a ring and a closed loop dual-loop control system.


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