Power supply control method

Abstract

The invention discloses a power supply control method. A power supply comprises a control circuit used for controlling the duty ratio of the power supply. The method comprises the following steps: 1)when a power supply system works in a light-load steady state, predicting a duty ratio D of a power supply circuit after a load is dynamic; 2) according to the prediction result in the step 1), obtaining a duty ratio amplitude limit value Dmax in combination with the turn ratio and the resonant inductance value of the transformer; 3) obtaining the real-time duty ratio D1 of the power supply circuit; calculating the real-time duty ratio of the power supply circuit according to the input voltage value and the output voltage value which are sampled in real time and the turn ratio of a known powersupply transformer; and 4) when the power supply system is in load operation, if the real-time duty ratio D1<=Dmax, controlling a PWM module to emit waves according to the real-time duty ratio D1, and if the real-time duty ratio D1 is greater than the Dmax, assigning the value of the Dmax to the real-time duty ratio D1, and then controlling the PWM module to emit waves according to the D1. According to the method, overshoot of the voltage and the current in the system is effectively suppressed, and overshoot of the voltage and the current is reduced.

Description

technical field [0001] The invention relates to switching power supply control technology, in particular to a power supply control method. Background technique [0002] In switching power supplies such as BUCK, BOOST, forward, flyback, phase-shifted full bridge and other circuits, most of them are controlled by PWM / PFM (pulse width modulation / pulse frequency modulation). When the input, output voltage or load changes, the power supply can be automatically adjusted through PWM / PFM. However, when there is a large dynamic, such as sudden load from light load to heavy load, the working mode of the circuit may switch from DCM (discontinuous mode) to CCM (continuous mode), so that the duty cycle D will have a Big change. Since the input cannot quickly follow the energy required by the output when the load is suddenly increased, there will be a process of input energy shortage. In order to make up for the lack of energy, the duty cycle D will have a large overshoot, which will ca...

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Problems solved by technology

But in the actual change from A to B, it will follow the figure 1 In the 2 and 3 route transition, there will be a process of large overshoot of the duty ratio D, such as state C, in which the duty ratio D c May be much larger than D b , therefore, it will cause a large overshoot of the voltage and current of the power device

[0004] When the current and voltage overshoot, devices such as switch tubes, diodes, and transformers will have greater voltage and current stress, which is not conducive to the selection of devices, and will also increase their losses and affect the efficiency of the power supply.

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